MECHATRONICS LEARNING ACTIVITY PACKET TORQUING B72001-AA08UEN
LEARNING ACTIVITY PACKET 8 TORQUING INTRODUCTION Torquing systems automatically apply the appropriate amount of torque to fasteners such as screws during the assembly process. This LAP reviews different types of torquing systems, their adjustment, and programming. ITEMS NEEDED Amatrol Supplied 87-MS6 Mechatronics Torquing Station 870-PS7313-AAU, 870-PS7314-AAU, or 870-PS7315-AAU Mechatronics Learning System for Siemens S7-300 - one per station 72024 Siemens S7-300 Programming Cable 82-900 Siemens Step 7 Programming Software School Supplied Computer with Windows XP Operating System Amatrol or School Supplied 41222 Hand Tool Kit or Equivalent FIRST EDITION, LAP 8, REV. C Amatrol, AMNET, CIMSOFT, MCL, MINI-CIM, IST, ITC, VEST, and Technovate are trademarks or registered trademarks of Amatrol, Inc. All other brand and product names are trademarks or registered trademarks of their respective companies. Copyright 2012, 2011 by AMATROL, INC. All rights Reserved. No part of this publication may be reproduced, translated, or transmitted in any form or by any means, electronic, optical, mechanical, or magnetic, including but not limited to photographing, photocopying, recording or any information storage and retrieval system, without written permission of the copyright owner. Amatrol,Inc., 2400 Centennial Blvd., Jeffersonville, IN 47131 USA, Ph 812-288-8285, FAX 812-283-1584 www.amatrol.com 2
TABLE OF CONTENTS SEGMENT 1 STATION OPERATION.......................................................... 4 OBJECTIVE 1 Describe the operation of an automated torquing system OBJECTIVE 2 Describe the operation of a non-servo electric slide OBJECTIVE 3 Describe the operation of a screw torque module SKILL 1 Operate an automated torquing station SEGMENT 2 COMPONENT ADJUSTMENT.................................................. 24 OBJECTIVE 4 Describe how to adjust DC motor speed SKILL 2 Adjust DC motor speed OBJECTIVE 5 Describe how to adjust a non-servo electric slide SKILL 3 Adjust a non-servo electric slide SEGMENT 3 TORQUE ADJUSTMENT...................................................... 40 OBJECTIVE 6 Describe how to adjust motor torque using a clutch SKILL 4 Adjust motor torque using a clutch OBJECTIVE 7 Describe how to adjust motor starter overloads SKILL 5 Adjust motor starter overloads SEGMENT 4 MODULE SEQUENCING...................................................... 58 OBJECTIVE 8 Describe a sequence of operation of a non-servo electric slide SKILL 6 Design a PLC program that sequences a non-servo electric slide OBJECTIVE 9 Describe a sequence of operation of screw torque module SKILL 7 Design a PLC program that sequences a screw torque module SEGMENT 5 STATION SEQUENCING...................................................... 87 OBJECTIVE 10 Describe a sequence of operation of an automated torquing station SKILL 8 Design a PLC program that sequences an automated torquing station OBJECTIVE 11 Describe the operation of a automated torquing station with manual/ auto/ reset functions SKILL 9 Design a PLC program that provides manual/ auto/ reset functions for an automated torquing station 3
SEGMENT 1 STATION OPERATION OBJECTIVE 1 DESCRIBE THE OPERATION OF AN AUTOMATED TORQUING SYSTEM An automated torquing system is used to apply a consistent amount of torque to fasteners on an automated assembly line. Typically the part is clamped into place, the fastener is inserted, and automated tooling torques the fastener to the desired level. The tooling typically consists of a spindle that can be controlled electrically (motor driven), pneumatically, or hydraulically. The amount of torque applied to the fastener is controlled in some manner, either electronically or mechanically. One method is to use a clutch that slips at a predetermined level. An example of an automated torquing system is an automated bottling line. Bottles are filled and the cap placed on them. They then move through a torquing module where the caps are tightened to a pre-determined amount. Figure 1. Automated Torquing Station 4
Torque is a measure of the turning effort caused by a force acting on a part that rotates. In a Mechatronics system, torque typically refers to the amount of force used to turn a bolt that fastens parts together or to install a lid on a product on an automated assembly line. As shown in figure 2, the amount of torque created by a person to turn a bolt with a wrench is caused by applying a force at some distance from the pivot point of the rotating part. In this case, the rotating part is the combination of the wrench and bolt. BOLT F FORCE APPLIED T TORQUE WRENCH PIVOT POINT r DISTANCE Figure 2. Applying Torque to a Bolt Automated torquing systems are often part of an FMS system. The assembly is usually delivered to and removed from the torquing system via a material handling device such as a robot, conveyor, or electric slide. 5
OBJECTIVE 2 DESCRIBE THE OPERATION OF A NON-SERVO ELECTRIC SLIDE A non-servo electric slide is just one type of device used to hold and position parts for a torquing station. They are typically powered by a motor to move parts from one position or station to the next and are controlled by a PLC. The parts are usually placed on and removed from the slide by a robot or pick and place unit. Figure 3 shows the construction of an electric slide. The carriage on which the part rides is attached to the carriage guide, which attaches to the bearing slide. The carriage moves along the slide, as the gears are turned by the synchronous belt and DC motor. SLIDE DETAIL DC MOTOR CARRIAGE GUIDE BEARING SLIDE CARRIAGE LIMIT SWITCHES ADJUSTABLE CLUTCH BELT/PULLEY DETAIL (CARRIAGE REMOVED) DC MOTOR BELT PULLEY SYNCHRONOUS BELT ADJUSTABLE CLUTCH Figure 3. Construction of a Non-Servo Electric Slide 6
One way to operate the motor is to use reversing motor starter. This allows it to drive in both the forward and reverse directions at a constant speed. A clutch is used to connect the motor to the belt pulleys or gears. The clutch is designed to slip at a preset torque level and protect the motor when the fixture drives into the hard stops. Limit switches are typically placed at the beginning of travel (BOT) and end of travel (EOT) positions to indicate to the PLC that the fixture is at one of the hard stops and to turn off the motor. Non-Servo Electric Slide Operation The electric slide operates under the control of a PLC. When the electric slide is in the BOT position, as shown in figure 4, the carriage activates a limit switch to indicate the carriage position to the PLC. MOTOR SLIDE CARRIAGE BOT LIMIT SWITCH ON EOT LIMIT SWITCH OFF Figure 4. Non-Servo Electric Slide 7
A part is placed onto the fixture on the electric slide either manually or automatically by another station or robot. When all of the initial conditions are satisfied (i.e. part present, slide at BOT position, start pushbutton pressed), the PLC turns on an output to energize the motor starter and supply power to the motor. This causes the motor to turn, which drives the synchronous belt, and moves the carriage, as shown in figure 5. MOTOR SLIDE PART BOT LIMIT SWITCH OFF CARRIAGE EOT LIMIT SWITCH OFF Figure 5. Slide Moving in Forward Direction The electric slide fixture moves until it reaches the hard stop at the EOT position. A limit switch is activated to indicate to the PLC that the slide has reached the EOT position. This signal causes the PLC to turn off the output that energized the motor starter, causing the motor to stop. The part can be removed from the slide and moved to another station for further processing. The PLC turns on an output to energize the reverse motor starter to turn on the motor in the reverse direction after the part has been removed. This causes the slide to move back toward the BOT position. When it reaches this position, the BOT limit switch is activated, causing the PLC to turn off the output that energized the reverse motor starter and stop the motor. The slide is then ready to accept a part from a previous station and start the next cycle. 8
OBJECTIVE 3 DESCRIBE THE OPERATION OF A SCREW TORQUE MODULE A screw torque module is used to apply torque to a fastener. Typically it contains a clamping device that holds the part and a spindle with tooling that applies torque to the fastener. The spindle can be operated with an electric motor, or driven using pneumatics or hydraulics. In the example in figure 6, the spindle motor is coupled to a clutch to control the amount of torque applied to the fastener. The speed of the motor is controlled using a pulse width modulator (PWM). The PWM amplifier applies varying amounts of average power to the motor, causing it to speed up or slow down. The parts to be torqued are moved to the torquing module by a slide or traverse axis. Screw Torque Module Operation The screw torque module operates under the control of a PLC. When the clamp is in the retracted position it actuates a proximity sensor that indicates the position to the PLC. PROXIMITY SENSOR CLAMP TOOLING SPINDLE MOTOR PART CLUTCH CYLINDER PWM Figure 6. Screw Torque Module 9
A part placed onto the fixture either manually or automatically by another station or robot actuates a second sensor. When all of the initial conditions are satisfied (i.e. part present, at BOT position, start pushbutton pressed), the PLC turns on an output to extend and clamp the part. After the clamp has extended, a proximity sensor indicates the position to the PLC, which signals that the part has been successfully clamped. After the part has been clamped, the screw torque module motor is energized by the PLC. This causes the tooling at the end of the screw torque module to tighten the fastener in the part to the torque setting determined by the clutch on the module. After the fastener has been torqued, the clamp is released. PROXIMITY SENSOR TOOLING TIGHTENS FASTER PART CLAMPED MOTOR ENERGIZED Figure 7. Screw Torque Application 10
Once the torquing operation is complete, the PLC turns on an output to turn on the slide s forward motor starter, causing the motor to turn on and the slide to move in the forward direction. When the slide reaches the EOT position, a limit switch indicates the position to the PLC, causing the PLC to turn off the output to the motor starter and stopping the motor. The part can then be removed and moved to another station for further processing. The PLC then turns on an output to the reverse motor starter. This output causes the motor to turn in the reverse direction and return the slide to the BOT position. The slide is then ready to accept a part from a previous station and start the next cycle. REVERSE MOTOR STARTER FORWARD MOTOR STARTER POWERED SLIDE SLIDE MOTOR BOT LIMIT SWITCH EOT LIMIT SWITCH Figure 8. Powered Slide 11
SKILL 1 OPERATE AN AUTOMATED TORQUING STATION Procedure Overview In this procedure, you will start up and operate the 87-MS6 Torquing Station of the 870 Mechatronics System. 1. Locate the Torquing station, shown in figure 9. Figure 9. Torquing Station 2. Verify that this station has been separated from the other stations. If it has not, then proceed with Step 3 to separate it from the other stations. If it has, then proceed to Step 4. 12
3. Perform the following substeps to separate the Torquing station from the other stations. A. Remove the power cord from the wall outlet. B. Remove the adjoining unit s power cord. C. Remove the adjoining unit s pneumatic hose. D. Disconnect the 9-pin to 9-pin cable from the other unit(s). E. Loosen the connecting fasteners that hold the work surfaces together by turning the wing nuts CCW. F. Push the station away from the other stations to give yourself room to work. 4. Perform the following safety check before you begin working on the station. Make sure that you can answer yes to each item before proceeding. YES/NO SAFETY CHECKOUT Remove all obstructions from the work area Check for signs of damage to the equipment Wear tight fi tting clothing, roll up long sleeves, remove ties, scarves, jewelry, etc. Tie up long hair Remove any robot teach pendants from the work area Locate the emergency stop button Ensure that safety glasses are worn by people in the area Ensure that all people are outside any work envelopes Figure 10. Mechatronics Safety Check 5. Connect an air supply line to the station s air manifold quick connect. 6. Plug the station s electrical power cable into a wall outlet. 7. Perform the following substeps to power up the 87-MS6 station. A. Place the Mode Selector switch in the Manual position. B. Remove the lockout/tagout device from the electrical power source. C. Remove the lockout/tagout device from the pneumatic power source. D. Turn on the air to the station by shifting the lever on the lockout valve. E. Set the station s air supply regulator to 50 psi/345 kpa. F. Turn the station s Main Power switch to the On position. 13
8. Perform the following substeps to open the PLC programming software. A. Make sure that the interface from the personal computer to the PLC is connected. B. Power up the PC and monitor. C. Start the SIMATIC Manager. 9. Perform the following substeps to open project Torquing. A. Click the Open Project/Library button. The Open Project/Library dialog should open. B. Locate project Torquing. The project Torquing is provided on a supplemental disk. If it is not listed on the dialog, click the Browse button on the dialog to view the projects located in the S7Proj folder. C. Double-click the Torquing icon to open the project. D. Select Expand All from View menu to expand the project s contents. The option is Expand All if using STEP 7 Version 5.2 or Show All Levels if using STEP 7 Version 5.3. 10. Perform the following substeps to download the PLC project named Torquing to the PLC. A. Place the PLC s Mode Selector switch in the RUN position. B. Reset the PLC. C. Download the SIMATIC 300 Station object to the PLC. Several dialogs will appear during the download. Click the appropriate response to continue downloading the program. The last dialog should ask if you wish to perform a complete (Warm) restart. D. Click Yes on the dialog to complete a warm restart. 11. Press the Output Power pushbutton to enable the PLC s outputs. 12. Turn the Mode Selector switch to Reset. This will home all of the actuators. Once these are all reset, the Start pushbutton light should turn off. 13. Turn the Mode Selector switch back to Manual. 14
14. Load the fixture with a valve assembly in the orientation shown in figure 11. VALVE ASSEMBLY FIXTURE Figure 11. Torquing Station 15. Perform the following substeps to step the station through its sequence of operations using the single step, manual mode. Observe the system and notify your instructor of anything that does not function properly. You should observe the following steps. 1. Clamp Extends 2. Close Clamp 3. Turn on Screw Motor for 3 Seconds 4. Release Close Clamp 5. Retract Clamp 6. Slide Extends 7. Slide Stops to Remove Part and Waits for Input 8. Retract Slide 9. Cycle Ends 15
A. Press and release the Start pushbutton to activate step 1 of the sequence. After the Start pushbutton has been pressed, the PLC turns on an output signal to energize SOL1 to extend the clamp. B. Press and release the Start pushbutton to activate step 2 of the sequence. The PLC outputs a signal to energize SOL2 to close the clamp. The clamp should grasp the part in the fixture. C. Press and release the Start pushbutton to activate step 3 of the sequence. The PLC outputs a signal to energize motor starter M1. This causes the Screw Torque module motor to turn on. This is a timed step, the motor should turn for 3 seconds. D. Press and release the Start pushbutton to activate step 4 of the sequence. The PLC removes the output signal to SOL2. This causes the clamp to open. E. Press and release the Start pushbutton to activate step 5 of the sequence. The PLC removes the output signal to SOL1. This causes the clamp to retract. F. Press and release the Start pushbutton to activate step 6 of the sequence. The PLC sends a signal to motor starter M2. This causes the motor to turn on and move the slide in the forward direction. It should move until it reaches the EOT position and actuates limit switch LS1. This signal causes the PLC to turn off the motor. G. Press and release the Start pushbutton to activate step 7 of the sequence. The station should stop. This is programmed into the PLC to allow the part to be removed. H. Press and release the Start pushbutton to activate step 8 of the sequence. The PLC sends a signal to motor starter M3. This causes the slide motor to turn on in the reverse direction. The slide should move back to the BOT position, where it actuates limit switch LS1. This signal causes the PLC to turn off the motor. I. Remove the valve assembly from the fixture. 16. Turn the Mode Selector switch to Auto. If you successfully single-stepped through the complete sequence and all of the actuators are back in their home position, the Start pushbutton lamp should be off and you can skip to Step 18. If it is not, perform Step 17 to reset the actuators. 16
17. Perform the following substeps to reset the actuators and put the system in Auto mode. A. Turn the Mode Selector switch to Reset. This will move all of the actuators back to their home positions. B. Turn the Mode Selector switch to Auto. The Start pushbutton lamp should be off at this time, indicating that the actuators are reset and the station is ready to run an automatic cycle. 18. Place another valve assembly on the fixture in the orientation shown in figure 11. NOTE When placing valve assemblies on the fixture, verify they have not yet been through the torquing process or that the knob is loosened prior to placement. 19. Perform the following substeps to observe the station s automatic cycle. A. Press the Start pushbutton to start the automatic cycle. Observe the station while it performs the torquing operation and then moves the part to the end of the slide. Here the cycle will stop to allow the part to be removed. The Start pushbutton indicator is on solid during the cycle to indicate that the station is operating. B. Press the Start pushbutton again. The slide should move back to the home position and the cycle ends. 20. Remove the valve assembly from the fixture. 21. Perform the following substeps to record the operation of the station when the Stop pushbutton is pressed. This will show you how the system is programmed to respond to the stop pushbutton. A. Place a valve assembly on the fixture in the correct orientation. B. Press the Start pushbutton to start the cycle again. C. During the middle of the cycle, press the Stop pushbutton to stop the system. Record whether the system executes a halt, cycle stop or emergency stop. You should observe that the station finishes its current step and stops. This means the Stop pushbutton has been programmed to perform a halt function. 17
D. Observe the operator panel indicators and record their status in the table below. OPERATOR PANEL INDICATORS Indicator Status (On/Off/Blinking) Output Power lamp Start lamp Emergency Stop lamp Figure 12. Operator Panel Indicators Since this is a halt, the machine can resume operation, so you should observe that Output power remains on and the Start pushbutton is off. It has been programmed to do so when the station is in the auto mode and ready to run its automatic cycle. The Emergency Stop lamp should be off because it is not pressed. E. Observe the PLC processor s status indicators and record their status. SF DC5V FRCE RUN STOP PLC PROCESSOR STATUS INDICATORS Indicator Status (On/Off) Figure 13. PLC Processor Status Indicators You should see that the PLC processor s DC5V and Run indicator lights are on, because the station is halted and ready to resume automatic operation. F. Observe the PLC I/O modules status indicators to see if some of them are on. You should see various input and output indicators on. Which ones are on will depend on the point in the operation at which the stop button was pushed. 18
22. Press the Start pushbutton to restart the system. It should continue where it left off and finish the cycle. NOTE If any actuators are manually moved while the system is halted, that station may not resume operation when the start pushbutton is pressed. If this occurs, go to Step 24 and restart the system. 23. Repeat Steps 21 and 22 three times, stopping the cycle with the Stop pushbutton at different times to observe how it reacts. 24. Perform the following substeps to restart the station IF any of the inputs change after the Stop button is pressed, otherwise skip to Step 25. If any of the inputs were changed, such as a part removed from the gripper, or a cylinder moved physically, the system cannot be restarted with the Start pushbutton. This is because the input signals will no longer match those needed to begin the sequence. This is a protective measure to prevent damage to the system. A. Remove the valve assembly from the fixture. B. Turn the mode selector switch to Reset. This will move all of the actuators back to their home positions. C. Turn the mode selector switch back to Auto. D. Place a valve assembly on the fixture in the correct orientation. E. Press the Start pushbutton to start the automatic cycle. Observe the system while it goes through the cycle before continuing to the next step. F. Remove the valve assembly from the fixture. 25. Perform the following substeps to record the operation of the station when the Emergency Stop pushbutton is pressed. This step will show you how the system is programmed to respond to the emergency stop pushbutton. A. Place a valve assembly on the fixture in the correct orientation. B. Press the Start pushbutton to start the cycle again. C. During the middle of the cycle, press the Emergency Stop pushbutton to stop the system. 19
D. Observe the operator panel indicators and record their status in the table below. OPERATOR PANEL INDICATORS Indicator Status (On/Off/Blinking) Output Power lamp Start lamp Emergency Stop lamp Figure 14. Operator Panel Indicators Since this is an emergency stop, the machine cannot resume operations. You should observe that the Output Power is off, the Start pushbutton lamp is off, and the Emergency Stop lamp is on. The Emergency Stop function does not remove the air supply. E. Observe the PLC processor s status indicators and record their status. SF DC5V FRCE RUN STOP PLC PROCESSOR STATUS INDICATORS Indicator Status (On/Off) Figure 15. PLC Processor Status Indicators You should see the PLC processor s DC5V and Run indicator lights on. F. Observe the PLC I/O modules status indicators to see if some of them are on. You should see various input indicators on, but all output indicators are off. This is because the Emergency Stop circuit breaks power to the Output Power contactor, which drops all output power. 20
26. Perform the following substeps to recover from the Emergency Stop. A. Pull the Emergency Stop button out. B. Remove the valve assembly from the fixture. C. Press the Output Power button to turn the outputs back on. You should hear the contactor pull in to re-establish the power to the outputs. D. Turn the Mode Selector switch to Reset. This will move all of the actuators back to their home positions. E. Place a valve assembly on the fixture in the correct orientation. F. Turn the Mode Selector switch back to Auto. G. Press the Start pushbutton to start the automatic cycle. Observe the system while it goes through the cycle before continuing to the next step. H. Remove the valve assembly from the fixture. 27. Perform the following substeps to record the operation of the station when the station experiences a power loss. This will show you how the station is programmed to respond to a power loss. A. Place a valve assembly on the fixture in the correct orientation. B. Press the Start pushbutton to start the cycle again. C. During the middle of the cycle, turn the Main Power switch to Off to remove power to the system. D. Observe the operator panel indicators and record their status in the table below. OPERATOR PANEL INDICATORS Indicator Status (On/Off/Blinking) Output Power lamp Start lamp Emergency Stop lamp Figure 16. Operator Panel Indicators Because this is a power loss, simulated by turning the Main Power switch off, power to everything past the Main Power switch is turned off. You should see that all operator panel indicator lamps and PLC indicators are off, but you will notice that the pneumatic power remains. You should also have seen any cylinders (gripper) complete their strokes because they are pneumatically-operated. 21
E. Observe the PLC processor s status indicators and record which indicators are on. SF DC5V FRCE RUN STOP PLC PROCESSOR STATUS INDICATORS Indicator Status (On/Off) Figure 17. PLC Processor Status Indicators You should see all indicators off because there is no power to the PLC. F. Observe the PLC I/O modules status indicators to see if some of them are on. Again, you should see all input and output indicators off because the modules have no power. 28. Perform the following substeps to recover from the power loss. A. Remove the valve assembly from the fixture. B. Place the Mode Selector switch in the Manual position. C. Turn the station s Main Power switch to the On position. D. Press the Output Power pushbutton to enable the PLC s outputs You should also hear the contactor located next to the PLC module pull in. The Start pushbutton should be blinking because the station is not ready for operation E. Turn the Mode Selector switch to Reset. This will move all of the actuators back to their home positions. It will also turn the vacuum to the gripper off. Once the actuators are reset, the Start pushbutton should turn off. F. Place a valve assembly on the fixture in the correct orientation. G. Turn the Mode Selector switch to Auto. H. Press the Start pushbutton to restart the operation. You should see the system start through its sequences. I. Run the system through two complete cycles to make sure it has recovered correctly, removing and replacing valve assemblies as necessary. 29. Perform the following substeps to shut down the 87-MS6 Torquing station. A. Close the LAD/STL/FBD Editor. B. Close the SIMATIC Manager. C. Turn off the PC and monitor. D. Turn the 87-MS6 s Main Power switch to Off. E. Perform a lockout/tagout on the system s electrical power source. F. Perform a lockout/tagout on the system s pneumatic power source. 22
SEGMENT 1 SELF REVIEW 1. Torque is a measure of the turning effort caused by a force acting on a part. 2. An automated torquing system is used to apply amounts of torque to fasteners on an automated assembly line. 3. A non-servo electric is used to hold and position parts for processing. 4. The electric slide operates under the control of a. 5. A Screw Torque module is used to apply to a fastener. 6. A Screw Torque module typically contains a device that holds the part and a spindle with tooling that applies torque to the fastener. 7. The spindle motor can be coupled to a to control the amount of torque applied to the fastener. 8. The speed of the motor can be controlled using a amplifier. 23
SEGMENT 2 COMPONENT ADJUSTMENT OBJECTIVE 4 DESCRIBE HOW TO ADJUST DC MOTOR SPEED One advantage of a DC motor is that its speed can be easily varied. The most basic method of controlling DC motor speed is to vary the resistance of a rheostat (variable resistor) that is connected to the motor windings. However, this method is not very energy efficient. A more efficient device commonly used is a pulse width modulator (PWM) amplifier, shown in figure 18. Figure 18. Pulse Width Modulator Amplifi er One additional advantage of a PWM circuit is that the pulses reach the full supply voltage instead of the reduced amount delivered by a resistive control, and it produces more torque in the motor. 24
Pulse width modulators work by switching the power supplied to the motor on and off rapidly. The DC voltage is converted to a square-wave signal, as shown in figure 19, alternating between fully on and zero. This gives the motor a series of power kicks. If the switching frequency is high enough the rotor s momentum keeps the motor running at a steady speed. Modulating the width of the pulse (the amount of time it is on) adjusts the duty cycle of the signal so the average power can be varied, which varies the motor speed. Depending on the design, this can be accomplished by turning a potentiometer, or by turning a switch on the PWM unit. 12V 0V Figure 19. Square Wave Signal Another advantage of a PWM controller over a resistive power controller is higher efficiency. At a 50% level, the PWM controller will use about 50% of full power, almost all of which is transferred to the load. In contrast, a resistive controller at 50% load power would consume about 71% of full power, 50% of the power goes to the load and the other 21% is wasted heating the series resistor. The main disadvantage of a PWM controller is that it adds complexity to the motor starter circuits. There is also the possibility that the PWM can generate radio frequency interference that may cause interference with other nearby electronic devices. 25
SKILL 2 ADJUST DC MOTOR SPEED Procedure Overview In this procedure, you will use the PWM amplifier to change the DC motor speed on the 87-MS6 Torquing Station to adjust the speed of the Screw Torque module s DC motor. This will show you how changing the speed of a PWMcontrolled DC motor can be done quickly and easily. 1. Locate the 87-MS6 Torquing station. 2. Verify that this station has been separated from any other stations. If it has not, then separate it from the other stations. If it has, then proceed to Step 3. 3. Perform the following safety check before you begin working on the module. Make sure that you can answer yes to each item before proceeding. YES/NO SAFETY CHECKOUT Remove all obstructions from the work area Check for signs of damage to the equipment Wear tight fi tting clothing, roll up long sleeves, remove ties, scarves, jewelry, etc. Tie up long hair Remove any robot teach pendants from the work area Locate the emergency stop button Ensure that safety glasses are worn by people in the area Ensure that all people are outside any work envelopes Figure 20. Mechatronics Safety Check 26
4. Connect an air supply line to the station s air manifold quick connect. 5.Plug the station s power cable into a wall outlet. 6. Perform the following substeps to power up the station. A. Place the Mode Selector switch in the Manual position. B. Remove the lockout/tagout device from the electrical power source. C. Remove the lockout/tagout device from the pneumatic power source. D. Turn on air to the station by shifting the lever on the lockout valve. E. Set the station s air supply regulator to 50 psi/345 kpa. F. Turn the station s Main Power switch to the On position. 7. Perform the following substeps to open the PLC programming software. A. Make sure that the interface from the personal computer to the PLC is connected. B. Power up the PC and monitor. C. Start the SIMATIC Manager. 8. Perform the following substeps to open project Torquing. A. Click the Open Project/Library button. B. Locate project Torquing. The project Torquing is provided on a supplemental disk. If it is not listed on the dialog, click the Browse button on the dialog to view the projects located in the S7proj folder. C. Double-click the Torquing icon to open the project. D. Select Expand All from the View menu to expand the project s contents. The option is Expand All if using STEP 7 Version 5.2 or Show All Levels if using STEP 7 Version 5.3. 9. Perform the following substeps to download the PLC project named Torquing to the PLC. A. Place the PLC s Mode Selector switch in the RUN position. B. Reset the PLC. C. Download the SIMATIC 300 Station object to the PLC. Several dialogs will appear during the download. Click the appropriate response to continue downloading the program. The last dialog should ask if you wish to perform a complete (Warm) restart. D. Click Yes on the dialog to complete a warm restart. 10. Press the Output Power pushbutton to enable the PLC s outputs. 27
11. Locate the PWM amplifier, shown in figure 21. It will be used to adjust the speed of the Screw Torque module motor. PULSE WIDTH MODULATOR SPEED CONTROL KNOB TOGGLE SWITCH Figure 21. Pulse Width Modulator used to Control Screw Motor Speed 28
Figure 22 shows the wiring for the pulse width modulator. Lines 1 and 2 carry the incoming power from the interface terminals to the PWM. Lines 3 and 4 carry power from the PWM to the screw torque motor. Lines 5-8 are optional analog connections. Line 9 is the output from the PLC that calls for the screw torque motor to turn on. The toggle switch on the PWM changes the control path so that it can be controlled by either the PLC or by the operator (manual). If operator wishes to control the motor speed using the speed control potentiometer, the toggle switch must be set to Manual. TOGGLE SWITCH PLC SPEED CONTROL POTENTIOMETER INCOMING 24V POWER TO PWM POWER TO SCREW MOTOR + - + - 1 2 3 4 PLC MANUAL 4 5 3 6 2 7 1 8 0 9 5 6 7 8 9 ANALOG OUTPUT OPTIONS ANALOG INPUT OPTIONS OUTPUT FROM PLC Q5.2 SCREW MOTOR ON MANUAL Figure 22. PWM Diagram TOGGLE SWITCH PWM AMPLIFIER INCOMING POWER TO PWM SCREW MOTOR 24 VDC 0 VDC + - 1 2 3 4 PWM CONTROL PLC MANUAL +5V SPEED CONTROL 5 6 7 8 ANALOG OUTPUT OPTIONS ANALOG INPUT OPTIONS +5V DC/DC CONVERTER 9 PLC DISCRETE OUTPUT 5.2 SCREW MOTOR ON Figure 23. PWM Schematic 12. Perform the following substeps to adjust the speed of the Screw Torque module using the PWM amplifier. A. Place a valve assembly in the fixture in the correct orientation. B. Place the Mode Selector switch in the Auto position. 29
C. Place the toggle switch on the PWM in the Manual position. This allows the setting to be controlled by the rotary switch on the module. D. Place the rotary speed control knob shown in figure 21, in the 0 position. E. Press the Start pushbutton to begin an automatic cycle. F. Observe the speed of the screw torque module motor. This is the motor controlled by the PWM. The motor should not be turning at all. G. Place the rotary speed control switch in the 1 position. H. Loosen the knob/screw assembly on the valve assembly and replace it on the fixture. I. Press the Start pushbutton to start an automatic cycle. J. Observe the speed. You should notice that the motor spins very slowly. K. Continue to increase the rotary speed control switch setting and run an automatic cycle after each change, loosening the knob/screw assembly after each cycle. You should notice that the speed of the screw torque module motor increases when the setting is increased on the PWM. 13. Perform the following substeps to home the station and set Auto mode. A. Turn the Mode Selector switch to Reset. This will home all of the actuators. B. Leave the toggle switch on the PWM Module in the manual position. C. Turn the Mode Selector switch back to Auto. 14. Perform the following substeps to run the station through an automatic cycle. A. Place a valve assembly in the fixture in the proper orientation. The valve assembly should have a spring, knob, and screw installed. B. Press the Start pushbutton to start the automatic cycle. Observe the system while it goes through a cycle before continuing to the next step. 15. Perform the following substeps to power down the station. A. Close the SIMATIC Manager. B. Turn off the PC and monitor. C. Turn the Main Power switch off. D. Perform a lockout/tagout on the system s electrical power source. E. Perform a lockout/tagout on the system s pneumatic power source. 30
OBJECTIVE 5 DESCRIBE HOW TO ADJUST A NON-SERVO ELECTRIC SLIDE A non-servo electric slide typically uses hard stops, either adjustable or nonadjustable, and limit switches for positioning, as shown in figure 24. The carriage is positioned by the motor turning the gears and driving the synchronous belt to move the carriage along the length of the slide. The carriage stops when it reaches the hard stop at either end of the slide. A limit switch is typically positioned so that it actuates as the carriage reaches a hard stop, sending a signal to the PLC to stop the motor and sequence another step. A clutch can be used on the motor s output. It is designed to slip if the motor is still turning after the fixture has driven into a hard stop. MOTOR NON-ADJUSTABLE HARD STOP CARRIAGE NON-ADJUSTABLE HARD STOP LIMIT SWITCH LIMIT SWITCH CLUTCH Figure 24. Hard Stops and Limit Switches If the limit switch is not adjusted properly, it will either send a signal to the PLC before the hard stop is reached, which will cause the slide to be out of position, or it will not actuate, causing the motor to continue to turn after the slide has reached the hard stop. 31
To change the amount of travel of an electric slide, the limit switches must be adjusted. One way to adjust the electric slide travel is to adjust the limit switches. The limit switches are adjusted using the following steps. Step 1: Turn off power - All power should be removed from the machine and the PLC turned off or placed in STOP mode. Alternatively, the PLC s output power can be turned off (preventing any machine motion) and the PLC placed into STOP mode. Step 2: Move the actuator to the desired position - Manually move the actuator to the position where the switch should be activated. Step 3: Loosen the limit switch or actuator arm - The limit switch or adjustable arm is usually held in place with a screw or bolt. They are sometimes mounted on a rail using screws, as shown in figure 25. Loosen the limit switch by either loosening the bolt or screws. LOOSEN LIMIT SWITCH Figure 25. Limit Switch Mounted on a Rail 32
Step 4: Position the limit switch or actuator arm - The limit switch is positioned by either moving it within the limits of the attachment holes, or by sliding it along a rail. Moving the arm depends on the type of limit switch actuator. Initially, the switch or arm should be positioned so that the limit switch actuator is just starting to move. This positions the switch actuator in its pretravel area. Monitor the PLC s input status indicator while continuing to slide the switch or actuator arm until a snap is heard. The snap indicates the internal contacts have closed. The PLC s input status indicator should turn on, indicating that the switch contacts have closed. This is the final position of the limit switch. METAL TAB ACTUATOR ARM Figure 26. Positioning the Limit Switch Step 5: Tighten the limit switch - Tighten the limit switch by tightening the bolts or screws loosened in Step 3. Step 6: Check the setting using the PLC status indicators - Manually operate the limit switch actuator arm while viewing the limit switch s status indicator on the PLC input module or while monitoring the terminals with a multimeter. The status indicator should turn on (or turn off, depending on if the switch is wired N.O. or N.C.) just as the actuator reaches the hard stop. If monitoring the limit switch terminals, they should change states. If the switch actuates too early, repeat the procedure until the adjustment is correct. This step requires power to the PLC. 33
SKILL 3 ADJUST A NON-SERVO ELECTRIC SLIDE Procedure Overview In this procedure, you will adjust the limit switches that are used to indicate fixture position to the PLC. This will familiarize you with adjusting the limit switches on a non-servo electric slide. 1. Locate the 87-MS6 Torquing station. 2. Verify that this station has been separated from any other stations. If it has not, then separate it from the other stations. If it has, then proceed to Step 3. 3. Perform the following safety check before you begin working on the module. Make sure that you can answer yes to each item before proceeding. YES/NO SAFETY CHECKOUT Remove all obstructions from the work area Check for signs of damage to the equipment Wear tight fi tting clothing, roll up long sleeves, remove ties, scarves, jewelry, etc. Tie up long hair Remove any robot teach pendants from the work area Locate the emergency stop button Ensure that safety glasses are worn by people in the area Ensure that all people are outside any work envelopes Figure 27. Mechatronics Safety Check 4. Connect an air supply line to the station s air manifold quick connect. 5. Plug the station s power cable into a wall outlet. 6. Perform the following substeps to power up the station. A. Place the Mode Selector switch in the Manual position. B. Remove the lockout/tagout device from the electrical power source. C. Remove the lockout/tagout device from the pneumatic power source. D. Turn on air to the station by shifting the lever on the lockout valve. 34
E. Set the station s air supply regulator to 50 psi/345 kpa. F. Turn the station s Main Power switch to the On position. 7. Perform the following substeps to open the PLC programming software. A. Make sure that the interface from the personal computer to the PLC is connected. B. Power up the PC and monitor. C. Start the SIMATIC Manager. 8. Perform the following substeps to open project Torquing. A. Click the Open Project/Library button. B. Locate project Torquing. The project Torquing is provided on a supplemental disk. If it is not listed on the dialog, click the Browse button on the dialog to view the projects located in the S7proj folder. C. Double-click the Torquing icon to open the project. D. Select Expand All from the View menu to expand the project s contents. The option is Expand All if using STEP 7 Version 5.2 or Show All Levels if using STEP 7 Version 5.3. 9. Perform the following substeps to download the PLC project named Torquing to the PLC. A. Place the PLC s Mode Selector switch in the RUN position. B. Reset the PLC. C. Download the SIMATIC 300 Station object to the PLC. Several dialogs will appear during the download. Click the appropriate response to continue downloading the program. The last dialog should ask if you wish to perform a complete (Warm) restart. D. Click Yes on the dialog to complete a warm restart. 10. Make sure that the Output Power to the PLC is turned off. You can verify this by checking the Output Power indicator lamp to see that it is off. 35
11. Perform the following substeps to adjust the limit switches on the non-servo electric slide. The slide has non-adjustable hard stops, shown in figure 28. The only way to adjust the positioning of the fixture at either end of slide travel is to adjust the limit switches. They send a signal to the PLC to turn off the motor after either the BOT or EOT position has been reached. CARRIAGE SLIDE HARD STOP HARD STOP LIMIT SWITCH Figure 28. Limit Switches and Hard Stops LIMIT SWITCH A. Place the PLC s Mode Selector switch in the STOP position. This will prevent any actuators from being turned on during the adjustment. B. Locate the two limit switches, shown in figure 24, on the non-servo electric slide. C. Position the slide fixture against the hard stop at the BOT position. D. Mark the position of the BOT switch with tape or a marker. E. Loosen the screws that attach the limit switch bracket to the rail. F. Move the switch an inch or so toward the middle of the slide. This will change the limit switch location, which will also change the homing location. G. Tighten the limit switch attachment screws. H. Place the PLC s Mode Selector switch in the RUN position. 36
12. Perform the following substeps to test the adjustment. A. Press the Output Power pushbutton to enable the PLC s outputs. B. Manually position the fixture so that it is located in the middle of the slide. C. Turn the Mode Selector switch to Reset. This will home all of the actuators. You should notice that the fixture has not stopped in front of the clamp and Screw Torque module. This is because the limit switch has been adjusted to turn on too early. As soon as the limit switch actuates, the motor turns off. 13. Turn the Main Power switch to the Off position. 14. Readjust the limit switch so that it will not actuate when the carriage has reached the hard stop at the BOT position. To do this, move it to the left of the original adjustment. 15. Turn the Main Power switch to the On position. 16. Press the Output Power pushbutton to enable the PLC s outputs. 17. Perform the following substeps to home the station. A. Turn the Mode Selector switch to Reset. This will home all of the actuators. You should notice that the fixture hits the hard stop, but the motor does not turn off. The clutch should slip to prevent the motor from burning out. 18. Turn the Main Power switch to the Off position. 19. Readjust the limit switch to the original position. 20. Turn the Main Power switch to the On position. 21. Press the Output Power pushbutton to enable the PLC s outputs. 22. Perform the following substeps to home the station. A. Use the slide s manual overrides to position the carriage in the middle of the slide. B. Turn the Mode Selector switch to Reset. This will home all of the actuators. You should notice that the fixture hits the hard stop and actuates the limit switch. The motor should turn off. 23. Perform the following substeps to run the station through an automatic cycle. A successful automatic cycle will let you know that the limit switch and the non-servo electric slide s travel at the BOT position has been adjusted properly. A. Place a valve assembly in the fixture in the correct orientation. The valve assembly should have a spring, knob, and screw installed. B. Press the Start pushbutton to start the automatic cycle. Observe the system while it goes through a cycle before continuing to the next step. 37
24. Perform the following substeps to power down the station. A. Close the SIMATIC Manager. B. Turn off the PC and monitor. C. Turn the Main Power switch off. D. Perform a lockout/tagout on the system s electrical power source. E. Perform a lockout/tagout on the system s pneumatic power source. 38
SEGMENT 2 SELF REVIEW 1. The major advantage of a DC motor is that its speed can be easily. 2. At 50% level a PWM will use about 50% of. 3. A pulse width modulator (PWM) amplifier is a device that may be used as an efficient motor speed controller. 4. A PWM circuit can produce more in a motor because the pulses reach full supply voltage. 5. PWM s work by switching the power supplied to the motor rapidly. 6. A non-servo electric slide typically uses hard stops and for positioning. 7. The stops when it reaches the non-adjustable hard stop at either end of the slide. 8. A limit switch is typically positioned so that it as the slide reaches the hard stop, sending a signal to the PLC to stop the motor and sequence another step. 39
SEGMENT 3 TORQUE ADJUSTMENT OBJECTIVE 6 DESCRIBE HOW TO ADJUST MOTOR TORQUE USING A CLUTCH A clutch is a mechanical device that uses mechanical, magnetic, hydraulic, pneumatic or friction connections to engage or disengage two rotating members. A common example is the friction clutch located between an automobile engine and manual transmission. The motor rotates and applies its rotational energy to the clutch, which supplies rotational energy to the drive shaft. In automation applications, the clutch is usually placed between a motor and a driven member and is designed to slip at a preset torque level to protect the motor from burning out if excessive loads are encountered. One application is a screw torque module, as shown in figure 29. CLUTCH STOPS TURNING ONCE PRESET TOQUE LEVEL IS REACHED FASTENER MOTOR TURNS TOOLING (DRIVEN MEMBER) ADJUSTABLE KNOB DC MOTOR Figure 29. Clutch Application The screw torque module uses an electric motor to tighten the fastener after the tooling has been inserted into the fastener. The motor and tooling turn the fastener until the preset clutch torque level has been reached. When the torque level has been reached, the clutch slips, stopping the movement of the tooling on the end of the screw torque module. 40
The torque level at which the clutch slips is controlled by compressing the springs with the adjusting nut. Turning the nut counterclockwise causes less force to be applied to the springs, reducing the amount of torque required for the clutch to slip. Turning the nut clockwise causes more force to be applied to the springs, increasing the amount of torque required for the clutch to slip. INCREASE TORQUE TURN ADJUSTMENT KNOB CCW DECREASE TORQUE LESS FORCE APPLIED TO THE SPRINGS TURN ADJUSTMENT KNOB CW MORE FORCE APPLIED TO THE SPRINGS Figure 30. Adjusting Torque 41
SKILL 4 ADJUST MOTOR TORQUE USING A CLUTCH Procedure Overview In this procedure, you will adjust the clutch on the screw torque module to apply different amounts of torque to the valve assembly screw. This will familiarize you with adjusting the torque level of a clutch. 1. Locate the 87-MS6 Torquing station. 2. Verify that this station has been separated from any other stations. If it has not, then separate it from the other stations. If it has, then proceed to Step 3. 3. Perform the following safety check before you begin working on the module. Make sure that you can answer yes to each item before proceeding. YES/NO SAFETY CHECKOUT Remove all obstructions from the work area Check for signs of damage to the equipment Wear tight fi tting clothing, roll up long sleeves, remove ties, scarves, jewelry, etc. Tie up long hair Remove any robot teach pendants from the work area Locate the emergency stop button Ensure that safety glasses are worn by people in the area Ensure that all people are outside any work envelopes Figure 31. Mechatronics Safety Check 4. Connect an air supply line to the station s air manifold quick connect. 5. Plug the station s power cable into a wall outlet. 42
6. Perform the following substeps to power up the station. A. Place the Mode Selector switch in the Manual position. B. Remove the lockout/tagout device from the electrical power source. C. Remove the lockout/tagout device from the pneumatic power source. D. Turn on air to the station by shifting the lever on the lockout valve. E. Set the station s air supply regulator to 50 psi/345 kpa. F. Turn the station s Main Power switch to the On position. 7. Perform the following substeps to open the PLC programming software. A. Make sure that the interface from the personal computer to the PLC is connected. B. Power up the PC and monitor. C. Start the SIMATIC Manager. 8. Perform the following substeps to open project Torquing. A. Click the Open Project/Library button. B. Locate project Torquing. The project Torquing is provided on a supplemental disk. If it is not listed on the dialog, click the Browse button on the dialog to view the projects located in the S7proj folder. C. Double-click the Torquing icon to open the project. D. Select Expand All from the View menu to expand the project s contents. The option is Expand All if using STEP 7 Version 5.2 or Show All Levels if using STEP 7 Version 5.3. 9. Perform the following substeps to download the PLC project named Torquing to the PLC. A. Place the PLC s Mode Selector switch in the RUN position. B. Reset the PLC. C. Download the SIMATIC 300 Station object to the PLC. Several dialogs will appear during the download. Click the appropriate response to continue downloading the program. The last dialog should ask if you wish to perform a complete (Warm) restart. D. Click Yes on the dialog to complete a warm restart. 10. Make sure that the Output Power to the PLC is turned off. 43
11. Perform the following substeps to set up the force table to test the clutch assembly in the next step. A. Go online with the processor and monitor the project. B. Select Display Force Values from the PLC menu. An Empty Force Values table should open. C. Select the Address column of the table. D. Enter Q5.2 into the address column. E. Press Enter. The address should be entered into the address column and BOOL entered into the Display Format Column. The cursor should move to the next row s address column. F. Select row 1 s Force Value column by clicking on it. Do not enter anything in this box at this time. You will force the value in the next step. 12. Perform the following substeps to reduce the torque setting on the screw torque module s clutch. A. Locate the screw torque module clutch assembly shown in figure 32. CLUTCH ADJUSTMENT KNOB Figure 32. Clutch Assembly and Motor B. Turn the knurled adjustment knob, shown in figure 32, counterclockwise (looking at the rear of the clutch assembly) five turns. You should be able to see that the tension on the springs is being reduced as you turn the knob. This is visible by the increase in the gap between the adjustment nut and the rest of the clutch components. 44
C. Manually place a pre-assembled valve assembly in the fixture and place the screw head against the Phillips head bit. You will hold the valve body in place while the motor is turning. D. Push the Output Power button to enable the PLC s outputs. E. Go back to the PC and, while someone is holding the valve assembly in place, enter true in the Force Value column for output Q5.2 and press Enter. F. Right-click in row 1 s Force Value column to display the shortcut menu. G. Select Force from the shortcut menu. H. Click Yes on the dialog to force the input on. This should force the screw motor on. It will stay on until you change the force value in the table. A red F should also appear in row 1 s Identification column to indicate that a force is active. The torque setting should be very low. The screw motor should turn and slip at this low torque level. I. Once the screw motor turns and slips turn the force off by changing the true value in row 1 s Force Value column to false. J. Press Enter. K. Right click in row 1 s Force Value column to display the shortcut menu. L. Select Force from the shortcut menu. The Force dialog should appear. M. Click Yes on the dialog to force the input off. A red F should appear in the row s Identification column to indicate that the force is active. N. Remove the valve assembly and test the tightness of the screw using a Phillips head screw driver. You should be able to easily turn the screw in the assembly. 45
13. Perform the following substeps to increase the torque setting on the screw torque module s clutch. A. Turn the knurled adjustment knob clockwise (looking at the rear of the clutch assembly) two turns. You should be able to see that the tension on the springs is being increased as you turn the knob. B. Manually place a pre-assembled valve in the fixture and place it against the Phillips head bit. You will hold it in place while the motor is turning. C. Force output Q5.2 on as in Step 12. The torque setting should be higher than in the last step. The screw motor should turn and slip at a higher torque level. D. Force output Q5.2 off as in Step 12. E. Remove the valve assembly and test the tightness of the screw using a Phillips head screw driver. You should still be able to turn the screw, but it may not be as easy as it was with the last setting. 14. Perform the following substeps to increase the torque setting on the screw torque module s clutch. A. Turn the knurled adjustment knob counterclockwise (looking at the rear of the clutch assembly) three more turns. This should place it close to the original setting. B. Manually place a pre-assembled valve in the fixture and place it against the Phillips head bit. You will hold it in place while the motor is turning. C. Force output Q5.2 on as in Step 12. The torque setting should be lower than in the last step. The screw motor should turn and slip at a higher torque level. D. Force output Q5.2 off as in Step 12. E. Remove the valve assembly and test the tightness of the screw using a Phillips head screw driver. You may or may not be able to turn the screw as it should be rather tight. 15. Perform the following substeps to delete the force on output Q5.2. A. Make sure the variable table is displayed on the monitor. B. Right-click in row 1 s Force Value column to display the shortcut menu again. C. Select Delete Force from the shortcut menu. The Delete Force dialog should appear. D. Click YES on the dialog to delete the force. The force should be removed. The red F should disappear from row 1 s Identification column. 46
16. Perform the following substeps to close the Force Values table. A. Close the Force Values table by clicking the X in the top right hand corner of the variable table window. A dialog should appear asking if you wish to save the variable table. B. Click No on the dialog to close the variable table without saving it. 17. Click the Monitor button on the LAD/STL/FBD Editor s toolbar to go offline. 18. Perform the following substeps to run the station through an automatic cycle. A. Place pre-assembled valve in the fixture. The valve body should have a spring, knob, and screw installed. B. Press the Start pushbutton to start the automatic cycle. Observe the system while it goes through a cycle before continuing to the next step. C. Remove the valve assembly from the station. 19. Perform the following substeps to power down the station. A. Close the SIMATIC Manager. B. Turn off the PC and monitor. C. Turn the Main Power switch off. D. Perform a lockout/tagout on the system s electrical power source. E. Perform a lockout/tagout on the system s pneumatic power source. 47
OBJECTIVE 7 DESCRIBE HOW TO ADJUST MOTOR STARTER OVERLOADS An overload protection device is used to sense when a motor is being loaded beyond its safe operating limits. The overload device should be sized to disconnect the motor from its power source before the motor is damaged. Overload relays are also included in magnetic motor starters as an additional protective device. Figure 33. Overload Protection Device When the motor starter s overload device reaches its trip point, the overload relay s set of N.C. contact open. The overload relay contacts are wired into the control circuit in a manner that will de-energize the starter coil. When the starter coil is de-energized, the motor starter line contacts open, which disconnects the motor from the power source. 48
Figure 34 shows the operation of a thermal overload circuit with a motor starter. In this example, during normal operations, the current passes through the normally closed contact in the overload to the motor starter coil. The N.O. contact in the overload blocks a signal to the PLC. MOTOR STARTER SIGNAL FROM PLC POSITIVE TO COIL 4.7 SLIDE REV. NEGATIVE TO MOTOR OL A1 A2 L1 L2 L3 N.C. CONTACT 98 97 95 96 L1 L2 L3 MOTOR STARTER T1 T2 T3 N.O. CONTACT (BLOCKED SIGNAL) OVERLOAD SIGNAL TO PLC 1.7 OVERCURRENT NEGATIVE TO COIL POSITIVE TO MOTOR + - + + - REARVIEW OF SLIDE MOTOR Figure 34. Thermal Overload Operation 49
If the motor current exceeds the trip setting, the normally closed contact in the overload will open (trip) and power will not be passed on to the motor starter as shown in figure 35. In this instance, the normally open contact in the motor starter will close, sending a signal back to the PLC that the overload has tripped. Once the heat from the excessive current has dissipated, the overload can be reset (manually) and will operate normally. MOTOR STARTER SIGNAL FROM PLC POSITIVE TO COIL 4.7 SLIDE REV. NEGATIVE TO MOTOR OL A1 A2 L1 L2 L3 N.C. CONTACT (BLOCKED) 98 97 95 96 L1 L2 L3 MOTOR STARTER T1 T2 T3 N.O. CONTACT (BLOCKED SIGNAL) OVERLOAD SIGNAL TO PLC 1.7 OVERCURRENT NEGATIVE TO COIL POSITIVE TO MOTOR + - + + - REARVIEW OF SLIDE MOTOR Figure 35. Thermal Overload Operation 50
Some overload devices are adjustable. An adjustable overload typically has a small dial that can be turned with a small screwdriver to change the trip point setting. TRIP CURRENT SET TO 1.6A ADJUSTMENT DIAL RESET Figure 36. Reset Button and Trip Current Adjustment Dial 51
SKILL 5 ADJUST MOTOR STARTER OVERLOADS Procedure Overview In this procedure, you will adjust the thermal overload on the motor starters for the non-servo electrice slide. This will familiarize you with adjusting the overload on a motor starter. 1. Locate the 87-MS6 Torquing station. 2. Verify that this station has been separated from any other stations. If it has not, then separate it from the other stations. If it has, then proceed to Step 3. 3. Perform the following safety check before you begin working on the module. Make sure that you can answer yes to each item before proceeding. YES/NO SAFETY CHECKOUT Remove all obstructions from the work area Check for signs of damage to the equipment Wear tight fi tting clothing, roll up long sleeves, remove ties, scarves, jewelry, etc. Tie up long hair Remove any robot teach pendants from the work area Locate the emergency stop button Ensure that safety glasses are worn by people in the area Ensure that all people are outside any work envelopes Figure 37. Mechatronics Safety Check 4. Connect an air supply line to the station s air manifold quick connect. 5. Plug the station s power cable into a wall outlet. 52
6. Perform the following substeps to power up the station. A. Place the Mode Selector switch in the Manual position. B. Remove the lockout/tagout device from the electrical power source. C. Remove the lockout/tagout device from the pneumatic power source. D. Turn on air to the station by shifting the lever on the lockout valve. E. Set the station s air supply regulator to 50 psi/345 kpa. F. Turn the station s Main Power switch to the On position. 7. Perform the following substeps to open the PLC programming software. A. Make sure that the interface from the personal computer to the PLC is connected. B. Power up the PC and monitor. C. Start the SIMATIC Manager. 8. Perform the following substeps to open project Torquing. A. Click the Open Project/Library button. B. Locate project Torquing. The project Torquing Station is provided on a supplemental disk. If it is not listed on the dialog, click the Browse button on the dialog to view the projects located in the S7proj folder. C. Double-click the Torquing icon to open the project. D. Select Expand All from the View menu to expand the project s contents. The option is Expand All if using STEP 7 Version 5.2 or Show All Levels if using STEP 7 Version 5.3. 9. Perform the following substeps to download the PLC project named Torquing to the PLC. A. Place the PLC s Mode Selector switch in the RUN position. B. Reset the PLC. C. Download the SIMATIC 300 Station object to the PLC. Several dialogs will appear during the download. Click the appropriate response to continue downloading the program. The last dialog should ask if you wish to perform a complete (Warm) restart. D. Click Yes on the dialog to complete a warm restart. 10. Press the Output Power pushbutton to enable the PLC s outputs. 53
11. Perform the following substeps to adjust the thermal overload setting. A. Locate the overload relay next to motor starter M2, shown in figure 38. This relay is used for both motor starters. THERMAL OVERLOAD RELAY OVERLOAD RESET BUTTON OVERLOAD SETTING Figure 38. Motor Starter Overload Location B. Record the overload setting in the space provided. Setting C. Using a small screwdriver, set the trip point (setting) to the lowest value. 54
12. Perform the following substeps to adjust the clutch so that it does not slip when the fixture is driven into the BOT stop. MOTOR CLUTCH ADJUSTMENT KNOB Figure 39. Motor Clutch Adjustment Knob A. Turn the knurled adjustment knob clockwise (looking at the rear of the clutch assembly) four or five turns. You should be able to see that the tension on the springs is being increased as you turn the knob. B. Press and hold motor starter M2 s manual override. The torque setting should be high enough that the motor does not slip when the fixture hits the stops. If the clutch still slips, repeat substep A to increase the torque setting. If the clutch does not slip, continue to hold the motor starter manual override until the thermal overloads trip. You should hear it trip and I1.7 should turn on. C. Verify that PLC input I1.7 is on. This is the thermal overload input. Because this is a fault, if you tried to operate the system using the program, it would not run. D. Press the Reset button on the thermal overload, shown in figure 38. 55
13. Readjust the thermal overload trip point to the original setting. 14. Readjust the clutch by turning the knurled adjustment knob counterclockwise the same number of times you turned it clockwise. 15. Perform the following substeps to home the station. A. Manually position the fixture in the middle of the slide. B. Turn the Mode Selector switch to Reset. This will home all of the actuators. You should notice that the fixture hits the hard stop and actuates the limit switch. The motor should turn off. 16. Perform the following substeps to run the station through an automatic cycle. A. Place pre-assembled valve in the fixture. The valve body should have a spring, knob, and screw installed. B. Press the Start pushbutton to start the automatic cycle. Observe the system while it goes through a cycle before continuing to the next step. 17. Perform the following substeps to power down the station. A. Close the SIMATIC Manager. B. Turn off the PC and monitor. C. Turn the Main Power switch off. D. Perform a lockout/tagout on the system s electrical power source. E. Perform a lockout/tagout on the system s pneumatic power source. 56
SEGMENT 3 SELF REVIEW 1. A clutch is a mechanical device that uses mechanical, magnetic, hydraulic, pneumatic or friction connections to engage or disengage two members. 2. A screw torque module uses a slip clutch between the and the driven member. 3. The torque level at which the clutch slips is controlled by the springs with the adjusting nut. 4. An protection device is used to sense when a motor is being loaded beyond its safe operating limits. 5. When the overload in a manual motor starter trips the overload relay s set of open, disconnecting the motor from its power source. 6. An adjustable overload typically has a small that can be turned with a small screwdriver to change the trip point setting. 57
SEGMENT 4 MODULE SEQUENCING OBJECTIVE 8 DESCRIBE A SEQUENCE OF OPERATION OF A NON-SERVO ELECTRIC SLIDE A typical non-servo electric slide, shown in figure 40, includes a carriage mounted on a belt-driven electric slide that transports parts from one end of the slide to the other. It is driven by a motor with a reversible motor starter, which includes a thermal overload to protect the motor if the clutch is misadjusted or faulty. In this example, the slide includes two limit switches to indicate the end-oftravel positions. FORWARD MOTOR STARTER THERMAL OVERLOAD REVERSE MOTOR STARTER MOTOR ELECTRIC SLIDE LIMIT SWITCH CARRIAGE LIMIT SWITCH CLUTCH Figure 40. Non-Servo Electric Slide Construction 58
An electric slide is generally controlled by a PLC, but could also be controlled by robotic I/O. In either case, the sequence will be similar to that shown in the following table. NON-SERVO ELECTRIC SLIDE SEQUENCE STEP INPUT OUTPUT 1 PLC Receives Slide Start Input Slide Extends (M2 on) (S1 on) 2 Slide Extended (LS2 on) Cycle Stops 3 PLC Receives Slide Start Input Retract Slide (M3 on) (S1 on) 4 Slide Retracted (LS1 on) Cycle Ends Figure 41. Non-Servo Electric Slide Sequence 59
Initial Conditions The electric slide must be in some pre-determined state before any sequence may take place. Many times this will be a state in which the carriage is in the BOT position (LS1 actuated). If this condition is not present, the non-servo electric slide will not operate and the PLC controlling the slide may even provide an alarm light or message to the operator, indicating that operator intervention is necessary. MOTOR OFF BOT LIMIT SWITCH LS1 ON OL 24 VDC M2 M2 FORWARD SLIDE MOTOR CLUTCH CARRIAGE GND M3 LIMIT SWITCH LIMIT SWITCH M3 LS1 REV LS2 FWD REVERSE Figure 42. Initial Condition 60
Step 1: PLC Receives Slide Start Input, Slide Extends In this step, the PLC controlling the slide receives an input to start the sequence. The input may be from another workstation, an operator, or another station. After receiving the input signal, the PLC energizes motor starter M2. This causes the motor to turn in the forward direction, towards the EOT position. MOTOR ON SLIDE BEGINS TO EXTEND BOT LIMIT SWITCH LS1 ON OL 24 VDC M2 FORWARD SLIDE MOTOR GND M2 CARRIAGE M3 M3 LIMIT SWITCH LS1 LIMIT SWITCH LS2 REVERSE REV FWD Figure 43. Step 1: PLC Reaches Slide Start Input, Slide Extends 61
Step 2: Slide Extended, Cycle Stops When the carriage has reached the EOT position, limit switch LS2 actuates to indicate to the PLC that the EOT position has been reached. The limit switch signal causes the PLC to turn off the signal to the motor starter, stopping the motor. After the slide has extended to the EOT position, it stops until it receives another input signal. This is to allow time for the part to be removed and also prevents the slide from moving when the part is being removed. MOTOR OFF LS1 OFF EOT LIMIT SWITCH LS2 ON 24 VDC OL M2 FORWARD SLIDE MOTOR CLUTCH M2 CARRIAGE GND M3 M3 LIMIT SWITCH LS1 REV LIMIT SWITCH LS2 FWD REVERSE Figure 44. Step 2: Slide Extended, Cycle Stops 62
Step 3: Receive Input Signal, Retract Slide After the input signal is received, the PLC outputs a signal to energize motor starter M3. This causes the motor to turn in the reverse direction, causing the fixture to move away from the EOT position and back toward the BOT position. MOTOR ON SLIDE BEGINS TO RETRACT OL 24 VDC M2 FORWARD SCREW MOTOR CLUTCH GND M2 CARRIAGE M3 M3 LIMIT SWITCH LS1 LIMIT SWITCH LS2 REVERSE REV FWD Figure 45. Step 3: Receive Input Signal, Retract Slide 63
Step 4: Slide Retracted, Cycle Ends After the carriage has reached the stop at the BOT position, limit switch LS1 is actuated, indicating to the PLC that the fixture has reached the BOT position. This causes the PLC to remove the output to motor starter M3, de-energizing the motor starter and turning off the motor. This is the home position for the non-servo electric slide. CARRIAGE HOMED MOTOR OFF LS1 ON LS2 OFF OL 24 VDC M2 FORWARD SLIDE MOTOR CLUTCH M2 CARRIAGE GND M3 M3 LIMIT SWITCH LS1 LIMIT SWITCH LS2 REVERSE REV FWD Figure 46. Step 4: Slide Retracted, Cycle Ends 64
This sequence just described is summarized by sequence diagram in figure 47. NON-SERVO ELECTRIC SLIDE SEQUENCE INPUTS OUTPUTS Step Input Action Output Action Start PB Stop PB LS1 LS2 Thermal O.L. Active Lamp M2 Slide FWD M3 Slide REV 0 Start Condition 0 1 1 0 0 0 0 0 1 Receive Start Input Slide Extends 1/0 1 1 2 Slide Extended Cycle Stops 0 1 0 0 3 Receive Start Input Retract Slide 1/0 1 1 4 Slide Retracted Cycle Ends 1 0 0 0 End Condition 0 1 1 0 0 0 0 0 Figure 47. Sequence Diagram 65
SKILL 6 DESIGN A PLC PROGRAM THAT SEQUENCES A NON-SERVO ELECTRIC SLIDE Procedure Overview In this procedure, you will design and test a PLC program that controls the non-servo electric slide on the 87-MS6 Torquing Station. 1. Design a ladder logic routine given the following information. The general sequence, I/O diagram, and power diagram are as follows: General Sequence 1) Pressing the Start pushbutton (PB1) causes the fixture to move toward the EOT position. 2) Once the slide has fully extended, actuating LS2, it stops. 3) Pressing the Start pushbutton again causes the slide to retract towards the BOT position. 4) When the slide has fully retracted, actuating LS1, the process will stop. Special Conditions The Start pushbutton should be off, indicating that the station is ready, when the slide is in its home position (at the BOT position with LS1 actuated). Program logic should start the non-servo electric slide sequence from its home position. 66
I/O DIAGRAM INPUTS OUTPUTS PB1 START INPUT I0.0 Q4.0 ACTIVE LAMP PB2 STOP I0.1 Q4.6 SLIDE FWD M2 LS1 SLIDE BOT I1.4 Q4.7 SLIDE REV M3 LS2 SLIDE EOT I1.5 THERMAL OVERLOAD I1.7 Figure 48. I/O Diagram OL 24 VDC M1 FORWARD CARRIAGE GND M1 CLUTCH M2 M2 LIMIT SWITCH LS1 REV LIMIT SWITCH LS2 FWD REVERSE Figure 49. Power Diagram 67
NON-SERVO ELECTRIC SLIDE SEQUENCE INPUTS OUTPUTS Step Input Action Output Action Start PB (I0.0) Stop PB (I0.1) LS1 (I1.4) LS2 (I1.5) Thermal O.L (I1.7). Active Lamp (Q4.0) M2 (Q4.6) Slide FWD M3 (Q4.7) Slide REV 0 Start Condition 0 1 1 0 0 0 0 0 1 Receive Start Input Slide Extends 1/0 1 1 2 Slide Extended Cycle Stops 0 1 0 0 3 Receive Start Input Retract Slide 1/0 1 1 4 Slide Retracted Cycle Ends 1 0 0 0 End Condition 0 1 1 0 0 0 0 0 Figure 50. Sequence Diagram 2. Perform the following substeps to open the PLC programming software. A. Make sure that the interface from the personal computer to the PLC is connected. B. Power up the PC and monitor. C. Start the SIMATIC Manager. 3. Perform the following substeps to create a project. A. Create a Project named L8S6XXX where XXX represents your initials. B. Create an S7 Station object for the station and configure its hardware. C. Open Organizational Block OB1. D. Enter the program that you developed in Step 1 into Organizational Block OB1. E. Save OB1. 4. If the 87-MS6 Torquing station is connected to another station, separate the stations. If the 87-MS6 Torquing station is already disconnected, continue to Step 5. 68
5. Perform the following safety check before you begin working on the station. Make sure that you can answer yes to each item before proceeding. YES/NO SAFETY CHECKOUT Remove all obstructions from the work area Check for signs of damage to the equipment Wear tight fi tting clothing, roll up long sleeves, remove ties, scarves, jewelry, etc. Tie up long hair Remove any robot teach pendants from the work area Locate the emergency stop button Ensure that safety glasses are worn by people in the area Ensure that all people are outside any work envelopes Figure 51. Mechatronics Safety Check 6. Connect an air supply line to the station s air manifold quick connect. 7. Plug the station s power cable into a power outlet. 8. Perform the following substeps to power up the 87-MS6 Torquing station. A. Remove the lockout/tagout device from the electrical power source. B. Remove the lockout/tagout device from the pneumatic power source. C. Turn on the air to the station by shifting the lever on the lockout value. D. Set the station s air supply regulator to 50 psi/ 345 kpa. E. Turn the station s Main Power Switch to the On position. 9. Perform the following substeps to download the project to the PLC. A. Place the Mode Selector Switch in the RUN position. B. Reset the PLC. C. Download the SIMATIC 300 Station object to the PLC. Several dialogs will appear during the download. Click the appropriate response to continue downloading the program. The last dialog should ask if you wish to perform a complete (Warm) restart. D. Click Yes on the dialog to complete a warm restart. 10. Go online with the processor and monitor the OB1 Block. 11. Press the Output Power pushbutton to enable the PLC s outputs. 69
12. Perform the following substeps to test the PLC program. At this time, the Start pushbutton lamp should be off. A. Press the Start pushbutton momentarily. The slide s fixture should move away from the BOT position and move toward the EOT position. After the fixture reaches the EOT position, LS2 should actuate, causing the motor to stop. The fixture should remain in the EOT position. B. Press the Start pushbutton again. The reverse motor starter should turn on, and the fixture should begin to move toward the BOT position. After the fixture reaches the BOT position, LS1 should actuate, causing the motor starter to de-energize, stopping the motor. C. Press the Start pushbutton again. The cycle should repeat. 13. Print out a copy of the ladder logic program and place it in your portfolio. It will be used in your assessment. 14. Perform the following substeps to shut down the 87-MS6 Torquing station. A. Close the LAD/STL/FBD Editor. B. Close the SIMATIC Manager. C. Turn off the PC and monitor. D. Turn the 87-MS6 s main power switch to Off. E. Perform a lockout/tagout on the system s electrical power source. F. Perform a lockout/tagout on the system s pneumatic power source. 70
OBJECTIVE 9 DESCRIBE A SEQUENCE OF OPERATION OF SCREW TORQUE MODULE An example of a typical screw torque module is shown in figure 52. This unit includes a screw motor, which is a DC motor controlled by a motor starter. It also has a clamp module, that contains a pneumatic slide and a gripper. The slide and gripper are controlled by two single-acting solenoids. In this example, when the PLC receives a signal that a part is in place, SOL1 is energized and extends the clamp and the part toward the screwdriver bit in the screw torque tool. When magnetic reed switch MR2 is on, indicating the clamp is extended, SOL2 is then energized to close the clamp on the part to hold it stationary during the torquing operation. Once the clamp is closed, inductive sensor IND1 is turned on indicating the clamp is closed on the part. The screw motor is then turned on and held on for three seconds to allow the operation to complete. After the three seconds is up, the screw motor turns off and SOL2 is de-energized so the clamp opens. Once the clamp opens, SOL1 is turned off, the clamp retracts, and the cycle is complete. PROXIMITY SENSOR (IND1) CLAMP SCREW DRIVER BIT SCREW TORQUE TOOL SCREW MOTOR MR1 MR2 CLAMP EXTEND CYLINDER (PNEUMATIC SLIDE) CLAMP CYLINDER SINGLE-ACTING SOLENOID (SOL1) PART ADJUSTABLE CLUTCH PWM AMPLIFIER SINGLE-ACTING SOLENOID (SOL2) Figure 52. Screw Torque Module Construction 71
The sequence of a screw clamp module is similar to the one shown in the table. SCREW TORQUE MODULE SEQUENCE STEP INPUT OUTPUT 1 PLC Receives Start Input (S1 on) Clamp Extends (SOL1 on) 2 Clamp Extended (MR2 on) Close Clamp (SOL2 on) 3 Clamp Closed (IND1 on) Turn on Screw Motor for Three Seconds (Dwell Timer Starts) 4 Screw Motor on for Three Seconds Release Close Clamp (Timer Done) 5 Clamp Closed Deactivated Retract Clamp 6 Clamp Retracted (MR1 on) Cycle Ends Figure 53. Screw Torque Module Sequence 72
Initial Conditions The screw torque module must be in some pre-determined state before any sequence may take place. Many times this will be a state in which the clamp is retracted and opened, and the motor starter is not energized. If these conditions are not present, the screw torque module will not operate and the PLC controlling the module may even provide an alarm light or message to the operator, indicating that operator intervention is necessary. PART MR1 ON CLAMP RETRACTED SCREW MOTOR OFF FROM SOURCE MR1 MR2 SOL1 CLAMP EXTEND IND1 SOL2 CLAMP CLOSE PWM AMPLIFIER INCOMING POWER TO PLC 24 VDC 0 VDC + - 1 2 3 4 PWM CONTROL PLC MANUAL +5V SPEED CONTROL 5 6 7 8 ANALOG OPTIONS +5V DC/DC CONVERTER 9 PLC DISCRETE OUTPUT 5.2 SCREW MOTOR ON Figure 54. Initial Condition 73
Step 1: PLC Receives Start Input, Clamp Extends In this step, the PLC controlling the slide receives an input to start the sequence. The input may be from another workstation, an operator, or another station. After receiving the input signal, the PLC energizes SOL1. This causes the clamp cylinder to extend, turning MR1 off. CLAMP BEGINS TO EXTEND FROM SOURCE MR1 MR2 SOL1 CLAMP EXTEND IND1 SOL2 CLAMP CLOSE PWM AMPLIFIER INCOMING POWER TO PLC 24 VDC 0 VDC + - 1 2 3 4 PWM CONTROL PLC MANUAL +5V SPEED CONTROL 5 6 7 8 ANALOG OPTIONS +5V DC/DC CONVERTER 9 PLC DISCRETE OUTPUT 5.2 SCREW MOTOR ON Figure 55. Step 1: PLC Receives Start Input, Clamp Extends 74
Step 2: Clamp Extended, Close Clamp After the clamp has extended, magnetic reed switch MR2 energizes, indicating to the PLC that the clamp has extended. This causes the PLC to energize SOL2, which causes the clamp to close. The clamp has an inductive sensor (IND1) that energizes when a part is gripped. CLAMP BEGINS TO CLOSE MR1 OFF MR2 ON CLAMP EXTENDED FROM SOURCE MR1 MR2 SOL1 CLAMP EXTEND IND1 SOL2 CLAMP CLOSE PWM AMPLIFIER INCOMING POWER TO PLC 24 VDC 0 VDC + - 1 2 3 4 PWM CONTROL PLC MANUAL +5V SPEED CONTROL 5 6 7 8 ANALOG OPTIONS +5V DC/DC CONVERTER 9 PLC DISCRETE OUTPUT 5.2 SCREW MOTOR ON Figure 56. Step 2: Clamp Extended, Close Clamp 75
Step 3: Clamp Closed, Turn on Screw Motor for Three Seconds After inductive sensor IND1 has energized, indicating that the clamp has closed, the screw motor is turned on for three seconds. This allows enough time for the tooling to tighten the fastener. IND1 ON CLAMP CLOSED FROM SOURCE MR1 MR2 SOL1 CLAMP EXTEND IND1 SOL2 CLAMP CLOSE PWM AMPLIFIER INCOMING POWER TO PLC 24 VDC 0 VDC + - 1 2 3 4 PWM CONTROL PLC MANUAL +5V SPEED CONTROL 5 6 7 8 ANALOG OPTIONS +5V DC/DC CONVERTER 9 PLC DISCRETE OUTPUT 5.2 SCREW MOTOR ON Figure 57. Step 3: Clamp Closed, Turn on Screw Motor for Three Seconds 76
Step 4: Screw Motor on for Three Seconds, Release Close Clamp The screw motor is stopped after the three second timer has expired. After the screw motor has stopped, the PLC removes the signal from SOL2. This causes the clamp to open and IND1 to turn off. CLAMP BEGINS TO OPEN BIT TURNS TO TORQUE SCREW SCREW MOTOR ON FROM SOURCE MR1 MR2 SOL1 CLAMP EXTEND IND1 SOL2 CLAMP CLOSE PWM AMPLIFIER INCOMING POWER TO PLC 24 VDC 0 VDC + - 1 2 3 4 PWM CONTROL PLC MANUAL +5V SPEED CONTROL 5 6 7 8 ANALOG OPTIONS +5V DC/DC CONVERTER 9 PLC DISCRETE OUTPUT 5.2 SCREW MOTOR ON Figure 58. Step 4: Screw Motor on for Three Seconds, Release Close Clamp 77
Step 5: Clamp Close Deactivated, Retract Clamp After the clamp has opened, the PLC removes the signal from SOL1. The causes the clamp to retract. The signal from magnetic reed switch MR2 will de-energize as the clamp begins to retract. The signal from magnetic reed switch MR1 will energize when the clamp has fully retracted. CLAMP OPEN CLAMP BEGINS TO RETRACT FROM SOURCE MR1 MR2 SOL1 CLAMP EXTEND IND1 SOL2 CLAMP CLOSE PWM AMPLIFIER INCOMING POWER TO PLC 24 VDC 0 VDC + - 1 2 3 4 PWM CONTROL PLC MANUAL +5V SPEED CONTROL 5 6 7 8 ANALOG OPTIONS +5V DC/DC CONVERTER 9 PLC DISCRETE OUTPUT 5.2 SCREW MOTOR ON Figure 59. Step 5: Clamp Closed Deactivated, Retract Clamp 78
Step 6: Clamp Retracted, Cycle Ends After MR1 has energized, the cycle is complete and the actuators are in the homed position. MR1 ON MR2 OFF CLAMP RETRACTED FROM SOURCE MR1 MR2 SOL1 CLAMP EXTEND IND1 SOL2 CLAMP CLOSE PWM AMPLIFIER INCOMING POWER TO PLC 24 VDC 0 VDC + - 1 2 3 4 PWM CONTROL PLC MANUAL +5V SPEED CONTROL 5 6 7 8 ANALOG OPTIONS +5V DC/DC CONVERTER 9 PLC DISCRETE OUTPUT 5.2 SCREW MOTOR ON Figure 60. Step 6: Clamp Retracted, Cycle Complete 79
This sequence just described is summarized by sequence diagram in figure 61. SCREW TORQUE MODULE SEQUENCE INPUTS OUTPUTS Step Input Action Output Action Start PB Stop PB MR1 Clamp Retracted MR2 Clamp Extended IND1 Clamp Closed Active Lamp SOL1 Clamp Extended M1 Screw Motor On SOL2 Clamp Close T1 Internal Timer Bit 0 Start Condition 0 1 1 0 0 0 0 0 0 1 Receive Start Input Clamp Extends 1/0 1 1 2 Clamp Extended Close Clamp 0 1 1 3 Clamp Closed Turn on Screw Motor for 3 Seconds 1 1 4 Screw Motor on for Three Seconds Release Close Clamp 0 0 1 5 Clamp Closed Deactivated Retract Clamp 0 0 0 6 Clamp Retracted Cycle Ends 1 0 0 End Condition 0 1 1 0 0 0 0 0 0 0 Figure 61. Sequence Diagram 80
SKILL 7 DESIGN A PLC PROGRAM THAT SEQUENCES A SCREW TORQUE MODULE Procedure Overview In this procedure, you will design and test a PLC program that controls the screw torque module on the 87-MS6 Torquing Station. 1. Design a ladder logic routine given the following information. The general sequence, I/O diagram, and power diagram are as follows: General Sequence 1) Pressing the Start pushbutton (PB1) causes the clamp to extend towards the valve body. 2) After the clamp has fully extended, it closes around the knob body. 3) After the clamp has closed, the screw motor is turned on for three seconds. 4) After the screw motor has turned off, the clamp is released. 5) After the clamp has released, the clamp is retracted. 6) After the clamp has retracted, the process is complete. Special Conditions Pressing the Stop pushbutton at any time will cause the screw torque module to stop (or halt) at the end of its current step. Pressing the Start pushbutton will resume the sequence. The Start pushbutton should be off, indicating that the station is ready, when the screw torque module is in its home position (clamp retracted). Program logic should start the screw torque module sequence from its home position. If the clamp closed signal turns on and then off as the clamp closes, a part is not present and the clamp should be reset. 81
I/O DIAGRAM PB1 PB2 MR1 INPUTS START INPUT I0.0 STOP I0.1 CLAMP RETRACTED I1.2 Q4.0 Q4.5 Q5.2 OUTPUTS ACTIVE LAMP CLAMP EXTEND SOL 1 SCREW MOTOR ON M1 MR2 CLAMP EXTENDED I1.3 Q5.3 CLAMP CLOSE SOL 2 IND1 CLAMP CLOSED I1.6 Figure 62. I/O Diagram FROM SOURCE MR1 MR2 SOL1 CLAMP EXTEND IND1 SOL2 CLAMP CLOSE PWM AMPLIFIER INCOMING POWER TO PLC 24 VDC 0 VDC + - 1 2 3 4 PWM CONTROL PLC MANUAL +5V SPEED CONTROL 5 6 7 8 ANALOG OPTIONS +5V DC/DC CONVERTER 9 PLC DISCRETE OUTPUT 5.2 SCREW MOTOR ON Figure 63. Power Diagram 82
SCREW TORQUE MODULE SEQUENCE INPUTS OUTPUTS Step Input Action Output Action Start PB (I0.0) Stop PB (I0.1) MR1 (I1.2) Clamp Retracted MR2 (I1.3) Clamp Extended IND1 (I1.6) Clamp Closed Active Lamp (Q4.0) SOL1 (Q4.5) Clamp Extended M1 (Q5.2) Screw Motor On SOL2 (Q5.3) Clamp Close T1 Internal Timer Bit 0 Start Condition 0 1 1 0 0 0 0 0 0 1 Receive Start Input Clamp Extends 1/0 1 1 2 Clamp Extended Close Clamp 0 1 1 3 Clamp Closed Turn on Screw Motor for 3 Seconds 1 1 4 Screw Motor on for Three Seconds Release Close Clamp 0 0 1 5 Clamp Closed Deactivated Retract Clamp 0 0 0 6 Clamp Retracted Cycle Ends 1 0 0 End Condition 0 1 1 0 0 0 0 0 0 0 Figure 64. Sequence Diagram 2. Perform the following substeps to open the PLC programming software. A. Make sure that the interface from the personal computer to the PLC is connected. B. Power up the PC and monitor. C. Start the SIMATIC Manager. 3. Perform the following substeps to create a project. A. Create a Project named L8S7XXX where XXX represents your initials. B. Create an S7 Station object for the station and configure its hardware. C. Open Organizational Block OB1. D. Enter the program that you developed in Step 1 into Organizational Block OB1. E. Save OB1. 4. If the 87-MS6 Torquing station is connected to other stations, separate the stations. If the 87-MS6 Torquing station is already disconnected, continue to Step 5. 83
5. Perform the following safety check before you begin working on the station. Make sure that you can answer yes to each item before proceeding. YES/NO SAFETY CHECKOUT Remove all obstructions from the work area Check for signs of damage to the equipment Wear tight fi tting clothing, roll up long sleeves, remove ties, scarves, jewelry, etc. Tie up long hair Remove any robot teach pendants from the work area Locate the emergency stop button Ensure that safety glasses are worn by people in the area Ensure that all people are outside any work envelopes Figure 65. Mechatronics Safety Check 6. Connect an air supply line to the station s air manifold quick connect. 7. Plug the station s power cable into a power outlet. 8. Perform the following substeps to power up the 87-MS6 Torquing station. A. Remove the lockout/tagout device from the electrical power source. B. Remove the lockout/tagout device from the pneumatic power source. C. Turn on the air to the station by shifting the lever on the lockout value. D. Set the station s air supply regulator to 50 psi/345 kpa. E. Turn the station s Main Power Switch to the On position. 9. Perform the following substeps to download the project to the PLC. A. Place the Mode Selector Switch in the RUN position. B. Reset the PLC. C. Download the SIMATIC 300 Station object to the PLC. Several dialogs will appear during the download. Click the appropriate response to continue downloading the program. The last dialog should ask if you wish to perform a complete (Warm) restart. D. Click Yes on the dialog to complete a warm restart. 10. Go online with the processor and monitor the OB1 Block. 84
11. Place an assembled valve into the fixture. The valve should be oriented as shown in figure 66. VAVLE ASSEMBLY FIXTURE Figure 66. Valve Body Orientation 12. Press the Output Power pushbutton to enable the PLC s outputs. 13. Perform the following substeps to test the PLC program. At this time, the Start pushbutton lamp should be off. A. Press the Start pushbutton momentarily. The clamp should extend toward the valve body. After the clamp has fully extended, it should close around the valve body. After the clamp has closed, the screw motor should turn on for three seconds, applying torque to the screw. As the screw motor is applying torque, the clutch on the screw motor should slip. After the screw motor has turned off, the clamp is released, releasing the valve body. After the clamp has released, it should begin to retract. After the clamp has retracted, the process is complete. B. Manually remove the valve body from the fixture. 14. Print out a copy of the ladder logic program and place it in your portfolio. It will be used in your assessment. 15. Perform the following substeps to shut down the 87-MS6 Torquing station. A. Close the LAD/STL/FBD Editor. B. Close the SIMATIC Manager. C. Turn off the PC and monitor. D. Turn the 87-MS6 s main power switch to Off. E. Perform a lockout/tagout on the system s electrical power source. F. Perform a lockout/tagout on the system s pneumatic power source. 85
SEGMENT 4 SELF REVIEW 1. The non-servo electric slide is generally controlled by a but could also be controlled by robotic I/O. 2. The electric slide must be in some state before any sequence may take place. 3. A typical non-servo electric slide is driven by a motor with a reversible motor starter that includes a to protect the motor. 4. A Screw Torque module can contain a clamp that contains a pneumatic slide and a gripper. 5. The slide and gripper are controlled by two solenoids, SOL1 and SOL2. 6. Magnetic reed switches MR1 and MR2 are used to if the clamp is retracted (MR1) or extended (MR2). 86
SEGMENT 5 STATION SEQUENCING OBJECTIVE 10 DESCRIBE A SEQUENCE OF OPERATION OF AN AUTOMATED TORQUING STATION An automated torquing system is used to apply consistent torque to fasteners on an automated assembly line. A typical automated torquing system includes an electrically driven spindle, a clamping mechanism, and a material handling device such as a powered slide. An example of an automated torquing system is shown in figure 67. This system is designed to tighten a screw and knob assembly in a part. The clamping module holds the knob stationary while the automated tooling turns the screw for a predetermined amount of time, threading it further into the knob. Once the timer is done, the clamping module releases the knob and retracts. A powered slide then shuttles the part to the end of travel location, where the part is removed from the carriage. M3 M2 MR3 IND1 CLAMPING MODULE SOL1 SOL2 MR2 POWERED SLIDE SLIDE MOTOR PART CARRIAGE BOT LIMIT SWITCH (LS1) CLUTCH AUTOMATED TOOLING EOT LIMIT SWITCH (LS2) ELECTRIC MOTOR Figure 67. Torquing Station Construction 87
The Torquing station will typically have a sequence similar to that shown in the table below. STEP INPUT OUTPUT 1 PLC Receives Slide Start Input (S1 Extend Clamp (SOL1 on) on) 2 Clamp Extended (MR2 on) Close Clamp (SOL2 on) 3 Clamp Closed (IND1 on) Turn on Screw Motor for 3 Seconds (Dwell Timer Starts) 4 Screw Motor on for Three Seconds Release Close Clamp (Timer Done) 5 Clamp Closed Deactivated Retract Clamp 6 Clamp Retracted (MR1 on) Slide Extends (M2 on) 7 Slide Extended (LS2 on) Cycle Stops 8 PLC Receives Slide Start Input (S1 Retract Slide (M3 on) on) 9 Slide Retracted (LS1 on) Cycle Ends Figure 68. Torquing Station Sequence 88
SKILL 8 DESIGN A PLC PROGRAM THAT SEQUENCES AN AUTOMATED TORQUING STATION Procedure Overview In this procedure, you will design and test a PLC program to control the 87-MS6 Torquing Station. 1. Design a ladder logic routine given the following information. The general sequence, I/O diagram, and power diagram are as follows: General Sequence 1) Pressing the Start pushbutton (PB1) causes the clamp to extend towards the valve body. 2) After the clamp has fully extended, it closes around the knob. 3) After the clamp has closed, the screw motor is turned on for three seconds. 4) After the screw motor has turned off, the clamp is released. 5) After the clamp has released, the clamp is retracted. 6) After the clamp has retracted, the slide moves toward the EOT position. 7) Once the slide has fully extended, actuating LS2, it stops to allow a part to be manually removed. 8) Pressing the start pushbutton again causes, the slide to retract towards the BOT position. 9) When the slide has fully retracted, actuating LS1, the process is complete. Special Conditions Pressing the Stop pushbutton at any time will cause the screw torque module to stop (or halt) at the end of its current step. Pressing the Start pushbutton will resume the sequence. The Start pushbutton should be off, indicating that the station is ready, when the screw torque module is in its home position (clamp retracted). Program logic should start the screw torque module sequence from its home position. 89
INPUTS I/O DIAGRAM OUTPUTS PB1 START INPUT I0.0 SOL1 Q4.0 ACTIVE LAMP PB2 MR1 STOP I0.1 CLAMP RETRACTED I1.2 SOL1 Q4.5 Q4.6 CLAMP EXTEND SLIDE FWD M2 M2 MR2 CLAMP EXTENDED I1.3 Q4.7 SLIDE REV M3 M3 LS1 SLIDE BOT I1.4 Q5.2 SCREW MOTOR ON M1 LS2 SLIDE EOT I1.5 SOL2 Q5.3 CLAMP CLOSE IND1 CLAMP CLOSED I1.6 OL THERMAL OVERLOAD I1.7 Figure 69. I/O Diagram 90
FROM SOURCE MR1 MR2 SOL1 CLAMP EXTEND IND1 SOL2 CLAMP CLOSE PWM AMPLIFIER INCOMING POWER TO PLC 24 VDC 0 VDC + - 1 2 3 4 PWM CONTROL PLC MANUAL +5V SPEED CONTROL 5 6 7 8 ANALOG OPTIONS +5V DC/DC CONVERTER 9 PLC DISCRETE OUTPUT 5.2 SCREW MOTOR ON 24 VDC GND OL M2 FORWARD M2 SLIDE MOTOR CLUTCH CARRIAGE M3 M3 REVERSE LIMIT SWITCH LS1 REV LIMIT SWITCH LS2 FWD Figure 70. Power Diagram 91
AUTOMATED TORQUING STATION SEQUENCE INPUTS OUTPUTS Step Input Action Output Action 0 Start Condition 0 1 1 0 0 1 0 0 0 0 0 0 0 0 0 1 Receive Start Input Clamp Extends 1/0 1 1 2 Clamp Extended Close Clamp 0 1 1 3 Clamp Closed Turn on Screw Motor for 1 1 3 Seconds 4 Screw Motor on for Release Close Clamp 0 0 1 Three Seconds 5 Clamp Closed Deactivated Retract Clamp 0 0 0 6 Clamp Retracted Slide Extends 1 0 1 0 7 Slide Extended Cycle Stops 0 1 0 0 8 Receive Start Input Retract Slide 1/0 1 1 9 Slide Retracted Cycle Ends 1 0 0 0 End Condition 0 1 1 0 0 1 0 0 0 0 0 0 0 0 0 Start PB (I0.0) Stop PB (I0.1) MR1 (I1.2) Clamp Retracted MR2 (I1.3) Clamp Extended IND1 (I1.6) Clamp Closed Slide BOT (I1.4) Slide EOT (I1.5) Thermal O.L. (I1.7) Active Lamp (Q4.0) M2 (Q4.6) Slide FWD Cont. M3 (Q4.7) Slide REV Cont. SOL1 (Q4.5) Clamp Extended M1 (Q5.2) Screw Motor On SOL2 (Q5.3) Clamp Close T1 Internal Timer Bit Figure 71. Sequence Diagram 2. Perform the following substeps to open the PLC programming software. A. Make sure that the interface from the personal computer to the PLC is connected. B. Power up the PC and monitor. C. Start the SIMATIC Manager. 3. Perform the following substeps to create a project. A. Create a Project named L8S8XXX where XXX represents your initials. B. Create an S7 Station object for the station and configure its hardware. C. Open Organizational Block OB1. D. Enter the program that you developed in Step 1 into Organizational Block OB1. E. Save OB1. 4. If the 87-MS6 Torquing station is connected to other stations, separate the stations. If the 87-MS6 Torquing station is already disconnected, continue to Step 5. 92
5. Perform the following safety check before you begin working on the station. Make sure that you can answer yes to each item before proceeding. YES/NO SAFETY CHECKOUT Remove all obstructions from the work area Check for signs of damage to the equipment Wear tight fi tting clothing, roll up long sleeves, remove ties, scarves, jewelry, etc. Tie up long hair Remove any robot teach pendants from the work area Locate the emergency stop button Ensure that safety glasses are worn by people in the area Ensure that all people are outside any work envelopes Figure 72. Mechatronics Safety Check 6. Connect an air supply line to the station s air manifold quick connect. 7. Plug the station s power cable into a power outlet. 8. Perform the following substeps to power up the 87-MS6 Torquing station. A. Remove the lockout/tagout device from the electrical power source. B. Remove the lockout/tagout device from the pneumatic power source. C. Turn on the air to the station by shifting the lever on the lockout value. D. Set the station s air supply regulator to 50 psi/ 345 kpa. E. Turn the station s Main Power Switch to the On position. 9. Perform the following substeps to download the project to the PLC. A. Place the Mode Selector Switch in the RUN position. B. Reset the PLC. C. Download the SIMATIC 300 Station object to the PLC. Several dialogs will appear during the download. Click the appropriate response to continue downloading the program. The last dialog should ask if you wish to perform a complete (Warm) restart. D. Click Yes on the dialog to complete a warm restart. 93
10. Go online with the processor and monitor the OB1 Block. 11. Place an assembled valve body into the fixture. The valve body should be oriented as shown in figure 73. VAVLE ASSEMBLY FIXTURE Figure 73. Torquing Station 94
12. Press the Output Power pushbutton to enable the PLC s outputs. 13. Perform the following substeps to test the PLC program. At this time, the Start pushbutton lamp should be off. A. Press the Start pushbutton momentarily. The clamp should extend toward the valve body. After the clamp has fully extended, it should close around the knob. After the clamp has closed, the screw motor should turn on for three seconds, applying torque to the screw. As the screw motor is applying torque, the clutch on the screw motor should slip. After the screw motor has turned off, the clamp is released, releasing the valve body. After the clamp has released, it should retract. The slide s fixture should move away from the BOT position and move toward the EOT position. After the fixture reaches the EOT position, LS2 should actuate, causing the motor to stop. B. Press the Start pushbutton momentarily. The reverse motor starter should turn on, and the fixture should begin to move toward the BOT position. After the fixture reaches the BOT position, LS1 should actuate, causing the motor starter to de-energize, stopping the motor. C. Press the Start pushbutton again. The cycle should repeat. D. Manually remove the valve body from the fixture. E. Press the Start pushbutton momentarily. The clamp should extend. The clamp should close, attempting to clamp the valve body. After the clamp has detected that a part is not present (input I2.0 turns on as the clamp is closing, and then turns off), the clamp should retract. 14. Print out a copy of the ladder logic program and place it in your portfolio. It will be used in your assessment. 15. Perform the following substeps to shut down the 87-MS6 Torquing station. A. Close the LAD/STL/FBD Editor. B. Close the SIMATIC Manager. C. Turn off the PC and monitor. D. Turn the 87-MS6 s main power switch to Off. E. Perform a lockout/tagout on the system s electrical power source. F. Perform a lockout/tagout on the system s pneumatic power source. 95
OBJECTIVE 11 DESCRIBE THE OPERATION OF A AUTOMATED TORQUING STATION WITH MANUAL/ AUTO/ RESET FUNCTIONS Torquing stations, like most other machines and stations, are usually programmed to provide two or three different operating modes depending upon the needs of the application. The three most common modes are automatic (or Auto), manual, and reset. Automatic Selecting the automatic mode causes the PLC program to enable the machine s automatic operation. After the machine is homed and the automatic mode is selected, pressing a start pushbutton causes the station to perform its sequence automatically. Depending upon the machine and process being controlled, the station may perform the sequence once (single-cycle) or continuously (continuous-cycle). Manual Selecting the manual mode causes the PLC program to enable the machine s manual functions. Placing a machine in manual mode enables the user to move the machine s actuators independently on an as needed basis, or to step through the machine s sequence. Reset Selecting Reset causes the PLC to reset the machine s actuators and program logic to some initial or starting condition (i.e. home position). This is usually a preparatory step before placing the machine into Automatic Mode. This is usually done in program logic by enabling a function or function block containing the reset operations while disabling functions and/or function blocks supporting the machine s other operating modes. To reset a torquing station, as with other types of stations, the PLC is normally designed to return all actuators to their start positions when the mode selector switch is placed in the Reset position. For a non-servo electric slide, the slide should be fully retracted to the beginning of travel (BOT) position. For a torque clamp module, the clamp should be fully retracted and opened. 96
CLAMPS RETRACTED AND OPEN SLIDE CARRIAGE HOMED Figure 74. Station Actuators in Reset Position The most basic way to program a reset function is to turn all output devices on or off at the same time to return all actuators to their start positions. In some cases, certain actuators may interfere with each other, so some reset functions must be programmed to perform a reset sequence of returning the actuators to their start positions in a certain order. For a Torquing station, one such sequence might be to retract the non-servo electric slide first, and then retract and open the clamp on the clamp torque module. 97