Set your Mobile Phones to Silent Respect your colleagues no private conversations Be on time

Size: px

Start display at page:

Download "Set your Mobile Phones to Silent Respect your colleagues no private conversations Be on time"

Delphia Lawson
5 years ago
Views:

1 Set your Mobile Phones to Silent Respect your colleagues no private conversations Be on time E. Francalanza 1

2 Thread Applications Thread Manufacturing Thread Design Thread Gaging Thread Measurement CMMs Gears Gear Applications Gear Manufacturing Gear Design Gear Measurement E. Francalanza 2

Coordinate Measuring Machines (CMMs) are extremely powerful metrological instruments: they enable us to locate point coordinates on three-dimensional structures.

3 Coordinate Measuring Machines (CMMs) are extremely powerful metrological instruments: they enable us to locate point coordinates on three-dimensional structures. When we add a computer to the CMM, we create an instrument that c automatically perform complex analysis and that can learn measurement routines to compare how a piece conforms to its specifications. E. Francalanza 3

analysis or comparisons. The greater the complexity of the piece, the greater the benefits from a CMM.

4 Instead of performing timeconsuming measurements with traditional, single axis instruments (micrometres, height gages, etc.) and performing cumbersome mathematics, you can dimensionally evaluate complex workpieces with precision and speed- and you can store data for later analysis or comparisons. The greater the complexity of the piece, the greater the benefits from a CMM. Coordinate measuring machines play an important role in a large number of industries, including aerospace, automotive, electronics, food processing, health care, paper, pharmaceuticals, plastics, research and development and semiconductor. E. Francalanza 4

The ability to quickly and accurately capture and evaluate dimensional data distinguishes the CMM from other types of measurement processes.

By reducing inspection time on the order of 80-90%, CMMs become a viable solution.

5 The ability to quickly and accurately capture and evaluate dimensional data distinguishes the CMM from other types of measurement processes. Sophisticated contact and noncontact sensors, combined with vast computer processing capabilities, make the CMM a practical, cost-effective solution. By reducing inspection time on the order of 80-90%, CMMs become a viable solution. CMMs are particularly suited for the following conditions: Short runs We may be producing hundreds or even thousands of a part, but the production run is not sufficient to justify the cost of production inspection tooling. Multiple features When we have a number of features, both dimensional and geometric, to control, CMM is the instrument that makes control easy and economical. Flexibility Because we can choose the application of the CMM system, we can also do short runs and measure multiple features. E. Francalanza 5

6 CMMs are particularly suited for the following conditions: High Unit Cost Because reworking or scrapping is costly, CMM systems significantly increases the production of acceptable parts. Production interruption Whenever you have to inspect and pass one part before you can start machining on the next part, a machining centre may actually be able to help a manufacturer save more money by reducing down time than would be saved by inspection. Cantilever Type In the cantilever-type CMM, a vertical probe moves in the z axis, carried by a cantilevered arm that moves in the y axis. This arm also moves laterally through the x axis. You have easy access to the work area, and the cantilever CMM provides a relatively large envelope without taking up too much floor space. E. Francalanza 6

The bridge construction adds rigidity to the machine, but it also forces us to make sure that both ends of the y axis track at exactly the same rate.

7 Moving Bridge Type The most popular type of CMM, this machine has a moving bridge. It is similar to the cantilever type, because it has a support for the outer ends of the y-axis bean on the base. The bridge construction adds rigidity to the machine, but it also forces us to make sure that both ends of the y axis track at exactly the same rate. Column Type This CMMs construction is similar to the most popular type of jig borer and is often referred to as a universal measuring machine, instead of a CMM. The column type CMMs construction provides exceptional rigidity and accuracy, and these machines are usually reserved for gage rooms rather then inspection. E. Francalanza 7

Horizontal Arm Type Unlike the pervious machines, the basic horizontal arm-type

area, which makes it perfect for very large workpieces like automotive dies.

x and y axes, both of which are overhead, supported by four vertical columns

8 Horizontal Arm Type Unlike the pervious machines, the basic horizontal arm-type CMM, also referred to as a layout machine, has a moving arm and the probe is carried along the y axis. This machine s main advantage is that it provides a large, unobstructed work area, which makes it perfect for very large workpieces like automotive dies. Gantry Type CMM In this type, the support of the workpiece is independent of the x and y axes, both of which are overhead, supported by four vertical columns rising from the floor. This setup allows you to walk along the workpiece with the probe, which is helpful for extremely large pieces. E. Francalanza 8

Sometimes a manufacturer will find it impractical or impossible to move a part of assembly

Portable CMMs are an articulated measuring arm, with precision bearings and rotary

Manual A manual mode CMM has a free floating probe that you, as the operator, move along

9 Sometimes a manufacturer will find it impractical or impossible to move a part of assembly to a stationary CMM. In those instances, a portable arm CMM can move to the part. Portable CMMs are an articulated measuring arm, with precision bearings and rotary transducers at eac of tis joints. Manual A manual mode CMM has a free floating probe that you, as the operator, move along the machine s three axes to establish contact with the part feature you are assessing. The differences between the contact positions are the measurements E. Francalanza 9

10 Manual Computer Assisted In the manual computer-assisted mode, we add electronic digital displays for these machines, making zero setting; changing the sign; converting inch and SI; and printing out data easy and practical. Even without further sophistication, these features save time, minimize calculations, and reduce errors. Motorized Computer Assisted A motorized CMM uses a joystick to drive the machine exes. The operator manipulates the joystick to bring the probe sensor into contact with the workpiece. E. Francalanza 10

11 Direct Computer Controlled (DCC) A direct computer controlled CMM is fully programmable. The CMM uses taught locations of CAD data to determine where the probe sensor contacts the workpiece, collecting measurement data. The fully automated CMM allows the operator to place the workpiece in a fixture or on the worktable, run a sored program, collect the data points, and generate an output reports. E. Francalanza 11

12 The probe is at the heart of the CMM operation. All CMMs consist of a probe and a way to move it along three axes relative to a workpiece. In a sense a CMM is three calipers placed in an orthogonal array. Probes fall into two general categories: Contact Non Contact Contact probes are the most commonly used on CMMs. Contact probes can include touch-trigger probes, and analogue scanning probes which maintain contact with the part as they can along the surface of the part as they measure. Noncontact probes include laser and video probes. E. Francalanza 12

Non Contact Probes Scanning Probes Laser Probes Non Contact

the machine or the software of the system enables a CMM to

Contour programs allow the CMM to quickly define detailed,

13 Non Contact Probes Scanning Probes Laser Probes Non Contact Probes Video Probes Touch Trigger Probes The programming of the machine or the software of the system enables a CMM to reach its full potential for accuracy, precision, and speed. Contour programs allow the CMM to quickly define detailed, complex non-geometric shapes without straight edges such as gears, cams, and injection moulds. These programs also can be used to compare the measurement data with a CAD Model. E. Francalanza 13

CMM manufacturers claim repeatability to or in excess of 2.

through their function, fulfil the fundamental principles of

14 CMM manufacturers claim repeatability to or in excess of 2.5µm and accuracy of 10µm, however these values decrease as the size of the CMM increases. Designers and manufacturers of CMMs take care that their machines, through their function, fulfil the fundamental principles of metrology, and features like system rigidity and the capability of the probe system make their success possible. E. Francalanza 14

15 CMMs reduce computational errors, but this reduction must be balanced with any errors that we might find in the programming. When you manually measure, you add systematic error because of the method you use, even though you may not even recognize the errors are there. E. Francalanza 15

16 E. Francalanza 16

Gearboxes and Differentials At the heart of each

makes use of different types of gears to transmit torque

From Grandfather Clocks to Wristwatches With the move to

17 Gearboxes and Differentials At the heart of each motorized vehicle lies an extremely complex system which makes use of different types of gears to transmit torque in varying ratios from the engine to the wheels. From Grandfather Clocks to Wristwatches With the move to the digital age, gears in clocks and watches are loosing their importance. Yet the most luxurious and exclusive watches all use gears as their principal mechanism. E. Francalanza 17

18 CD Drives, Printer and Scanners These items can be found on each desk in every office. They make use of gears to achieve linear or rotary motion from electrical motors. Mountain Bikes One of the most notorious gear manufacturers Shimano, produces gears for mountain bikes. E. Francalanza 18

Broaching uses a toothed tool to remove material.

19 Broaching is one of the most common methods to manufacture gears. Two types of broaches exist: Internal and External. Broaching uses a toothed tool to remove material. It is used for machining of gears since it allow for high precision machining and is idle for the odd shape of gears. Broaching finishes a surface in a single pass, which makes it very efficient. E. Francalanza 19

20 Hobbing is a machining process for making gears, splines, and sprockets on a hobbing machine, which is a special type of milling machine. The teeth or splines are progressively cut into the workpiece by a series of cuts made by a cutting tool called a hob. Compared to other gear forming processes it is relatively inexpensive but still quite accurate, thus it is used for a broad range of parts and quantities. It is the most widely used gear cutting process for creating spur and helical gears and more gears are cut by hobbing than any other process since it is relatively quick and inexpensive E. Francalanza 20

21 For high production of gears, especially gears which are small in size the plastic injection moulding method is an extremely popular method, since many gears can be produced in one cycle. E. Francalanza 21

22 Metal Casting is a common type of manufacturing process by which a liquid metal is poured into a mould. For Gear manufacture the hollow cavity in which the metal is poured will hold the shape of the gear to be cast. Especially used for very large and complex gears. E. Francalanza 22

23 E. Francalanza 23

24 For process control, particularly in the setup of gear making machines, and for the inspection of gear cutting tools; often the errors of individual tooth elements must be determined in a series of analytical measurements. The discrete measurement of particular gear elements is also needed for the inspection of gears intended for critical applications. E. Francalanza 24

25 To determine how the gear will perform in continual engagement with a mating gear. Instruments providing close approximation of the actual operating conditions are used, and the composite action of several potential tooth errors is measured by the functional checking of a work gear, commonly using for mating member a master gear of known accuracy. Analytical gear measurements are used to check for compliance of particular gear tooth parameters with the pertinent design specifications, or deviations, to measure the characteristics and extent of the error. E. Francalanza 25

26 1. To determine the sources of improper gear operation, either experienced in use or discovered by functional checking 2. To inspect the accuracy of specific gear tooth parameters, for example involute profile, tooth spacing or backlash errors that may be mutually compensating. 3. To provide guidance in the proper setup of gear manufacturing machines, thereby avoiding the production of faulty gears. 4. To check the appropriate execution or sharpening of gear cutting tools, such as hobs or gear cutters. 5. To determine the effects of the applied heat-treating processes so that appropriate modification in work material or procedures can be made. E. Francalanza 26

Pitch is the theoretical distance between corresponding points on adjacent teeth. The actual distance between those points is the tooth-to-tooth spacing, a directly measurable dimension.

27 Pitch is the theoretical distance between corresponding points on adjacent teeth. The actual distance between those points is the tooth-to-tooth spacing, a directly measurable dimension. The profile of the gear tooth is the shape of its functional surface that during the operation of the gear is in contact with the corresponding tooth surface of the mating gear. The involute curve proved to be particularly well adapted for the profile of most types of commonly used gear teeth because it can assure a constant velocity transmission of the rotation in a slippagefree rolling contact. E. Francalanza 27

28 A Involute profile B Lead C Contact line (path of the tooth form generating tool) In the manufacture of gears the teeth are usually made thinner than the width of the tooth space along the pitch circle in order to assure the specified backlash. That additional space is commonly required to avoid tooth jamming as the consequence of tolerances in pitch, profile, concentricity etc. On the other hand, too much backlash cause by excessive tooth thinning results in noisy and inaccurate gears. E. Francalanza 28

points of that arc is the distance measured.

29 Tooth thickness is the length of the pitch circle section bounded by the opposite flanks of the gear tooth. The length of the circle section is the arc thickness of the tooth, but for practical reasons the straight line distance between the end points of that arc is the distance measured. Actual Measurement A direct method of tooth thickness measurement is by means of a gear tooth Caliper. The gear tooth Caliper has two adjustable members, the tongue for setting the addendum and the jaws for measuring the chordal thickness. E. Francalanza 29

30 The method determines the composite effect of gear errors, simulating the operational conditions by running two mating gears in mesh. The tight mesh engagement, which is used for most functional gear checking, produces contact on both flanks of the meshing gear teeth, and for that reason it is also termed double flank or dual flank testing. Cylindrical Gear Running Machines are used for monitoring the functional quality, e.g. for evaluating the running and noise behaviour. Speeds up to 3000 rpm and braking torques up to 20 Nm can be realized. E. Francalanza 30

31 In Double flank testing both flanks of the mating gears are in simultaneous contact along a portion of the tooth flank exceeding the area that is active in most types of actual gear operations. Single flank gear testing simulates the actual operating conditions of a gear pair running at a fixed centre distance. The single flank gear tester measures the transmission error of a pair of gears. A Double flank contact gear rolling with the gears in tight mesh. Variations of tooth profile and pitch produce centre distance changes as composite effect. B Single flank testing with gears mounted at fixed centre distance. Variations of gear tooth profile and pitch cause transmission errors which are registered by an optical electronic rotary resolver and recorded on a strip chart. E. Francalanza 31

Several different objectives may warrant the inspection of gears in a n automatic process, such as: Inspection during manufacturing, between two successive production steps, for avoiding the

32 Several different objectives may warrant the inspection of gears in a n automatic process, such as: Inspection during manufacturing, between two successive production steps, for avoiding the continued processing of defective workpieces. Inspection of finished gears, which are produced in large volume and are intended for critical applications. Through analysis of a series of gear parameters measured with a high degree of accuracy. This fully automatic CNC controlled gear measuring centre has been designed as a compact unit for the smaller workpiece diameter range up to 260 mm. The measuring centre is suitable for testing many types of different gears. In addition to the mechanical components of the measuring centre such as bed, workpiece rotation, the tailstock, the horizontal, vertical and tangential measuring axis and the 3D tracer head, a 4-axis path control in conjunction with a computer ensures the functions of this machine. E. Francalanza 32

A Reminder: Many of the gear measuring instruments have various automatic functions, however two significant functions of those instruments are not automated:

33 A Reminder: Many of the gear measuring instruments have various automatic functions, however two significant functions of those instruments are not automated: The mounting and removal of the work gear being inspected. The evaluation and decision-making based on the determined dimensional conditions. E. Francalanza 33

34 During this lecture we have seen: Gear Applications Gear Manufacturing Gear Design Gear Measurement CMMs E. Francalanza 34

35 E. Francalanza 35

Gear Measurement. Lecture (7) Mechanical Measurements

Gear Measurement. Lecture (7) Mechanical Measurements 18 3. Gear profile checking 2. Involute measuring machine In this method the gear is held on a mandrel and circular disc of same diameter as the base circle of gear for the measurement is fixed on the