Custom Couplings, Assemblies, U-joints, Generate-Only

Transcription

1 Custom Couplings, Assemblies, U-joints, Generate-Only Derek Evans and Tom Puerling 1 Where are we today? Custom Couplings, Assemblies, U-joints Generate-Only Presentations & Seedbox Machined Springs Technical Orientation Catalog Standards Coupling Selection Pyramid of Flexure Knowledge 2

2 Agenda What is a Custom coupling? Couplings vs U-Joints Adjusting the Flexure and performance Generate-only designs Assemblies 3 BD Series McMaster-Carr Aluminum only Clamp and set screw options S shorter lengths High Torsional Stiffness 4

3 Building Part Numbers BDCA BDSA Attachment style: C : Integral Clamp S : Set Screw 5 Custom Couplings What makes a coupling a custom? When it is not a standard! 6

4 Custom Couplings Value-Added Design Improve Pricing for High Quantities Attachment Methods Materials Outside processing Design into System > Reduce Outsourcing 7 Custom Couplings Special Attachments o Bore shapes o Removeable caps o Threads Performance specs o Torque, misalignment, torsional rate Dimensional Specs o Tighter tolerances o Larger/smaller bores with relief 8

5 How a coupling becomes a new custom design Customers requirements not met by standard or existing custom designs Engineer creates drawing Drawing submitted for review and pricing this process may take several days Pricing is sent to customer for review If customer okays pricing, a part number is assigned 9 10

6 Custom Examples 5215, 3508, 7550 & 6732 What can you tell me about these??? Hint: Same dimensions and flexure as WAC25 11 Slight changes led to a custom Similar Part Description / Difference from WAC25 Same flexure. Lock washer under cap screw. Same flexure. Allows smaller A1 bores than WAC25. Same flexure. Allows relief over large A1 bore sizes. Same flexure. Different attachment (2 set screws + keyway) 12

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10 19 What if we need to change the performance? 20

11 Adjusting the Flexure and Performance Torque Capacity Torsional Rate Misalignment Capacity 21 Adjusting the Torque Capacity Nominal Coil Thickness (NCT) Change in ID Change in OD 22

12 Adjusting the Torque Capacity Material Aluminum and 303 CRES 17-4 PH and 15-5 PH CRES Other materials??? 23 Adjusting the Torque Capacity Thickening Thicker coils at the ends increase capacity (10%) Handedness Direction of rotation influences stress level RH flexure: CCW is lower stress than CW 24

13 Adjusting the Torsional Rate Nominal Coil Thickness (NCT) Change in ID Change in OD 25 Adjusting the Torsional Rate Number of Starts Single Triple Double (DS) Triple (TS) Single Double 26

14 Adjusting the Torsional Rate Number of Coils 27 Adjusting the Torsional Rate Material Engineered Plastics (Delrin 150) 7075-T6 Aluminum Titanium Others 28

15 Adjusting the Torsional Rate Why adjust the torsional rate? Wind-up Resonance 29 Is it really that simple? Space constraints ood, length, other features Stresses otorque, bending, axial Stiffnesses otorque, bending, axial Performance give and take 30

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17 WAC25 vs. DS8955 WAC25 DS8955 Momentary Dynamic Torque 2.2Nm 3.5Nm Torsional Rate 3.5deg/Nm 1.1deg/Nm Angular Misalignment 5deg 3deg Axial Misalignment 0.25mm 0.15mm Parallel Misalignment 0.25mm 0.15mm 33 U-Joints 34

18 What is a Helical U-joint? Bends more than 5 degrees 90 deg MAX normally (cardan ~45deg MAX) No moving parts Constant velocity 35 Why use a Helical U-joint? Excessive or intentional misalignment Angular misalignment Parallel misalignment Axial misalignment Custom-designed Constant Velocity 36

19 U-Joint Examples 37 Torsional Stability (or instability) 38

20 Instability Geometry Driven o Number of coils o Aspect ratio 39 Instability 40

21 Adjusting the Angular Misalignment Change in OD Nominal Coil Thickness (NCT) Number of Coils Slot Width Outside Diameter 41 Solved Application Story # 5 OFFICE FURNITURE - Computer Table THE CHALLENGE The need was for an easy method to raise and lower a computer desk top. Allows people of different heights sitting at the same desk to easily and quickly adjust the table top height to fit their own needs comfortably. Needs a 90 degree universal joint incorporated between a hand crank and a lead screw. The customer considered a gearbox but this idea was abandoned due to cost. THE SOLUTION 15-5 PH material is used to give the necessary torque capacity and longevity, in this potentially abusive application. The HELI-CAL Flexure has 17 1/2 coils to allows for the required 90 degree misalignment. Stress relief holes were added for some of the applications. THE ANSWER HELI-CAL Flexured U-Joint #

22 43 Flexure Configurations Flexure Configuration One Flexure - Like A SERIES Two Flexures - Like MC SERIES 44

23 Bore Shapes Round Square Hexagonal D or Double D Spline 45 Attachments Integral Clamp Set Screw Roll and Dowel Pins Removable Cap Tang Drive Internal and External Threads 46

24 Integration of Features (Put it all together) 47 And More Integrated Features 48

25 And More Integrated Features 49 Integration of Features 50

26 Generate-Only Designs ofirst character of the part number is the letter G (e.g. G1400) othe customer supplies the blank. Helical Generates the Flexure in the blank 51 Generate Only Coupling 52

27 Helical Assembly Examples What do assemblies have in common? 2 or more parts 53 Why use a Helical Assembly? Ease installation Cost Integrated parts 54

28 Solved Application Story # 6 OFFICE EQUIPMENT THE CHALLENGE Customer was already using Helical's MCAC150 flexible coupling. Customer required a modification to make it easier to install and have a more positive drive. Maintenance requirements made the standard coupling difficult to remove and replace. THE SOLUTION One end of the MCAC150 coupling was fitted with a removable cap for ease of machine maintenance, and the coupling was shortened. A double "D" bore was incorporated in the coupling to assured that a positive drive was maintained. THE ANSWER HELI-CAL Flexure Flexible Shaft Coupling # Flexure Facts Engineering Seminar Manual 56

29 Keyword Review CONSTANT VELOCITY The driver and driven ends of the u-joint will turn at the same speed 90 DEGREE ANGLE Try that with a cardan! NO MOVING PARTS Greater reliability, less down time, higher production, more money CUSTOM ATTACHMENTS Combining features adds value SPECIAL MATERIALS Wide-range available 57 Custom Couplings, Assemblies, U-joints, Generate-Only Any Questions? 58