Dr.Apiwat Muttamara

1. Jig & Fixture Design Dr.Apiwat Muttamara

2. Introduction Modern Manufacturing FMS, CIM Workholder (Jig & fixture)

3. Purpose • What ’s different between Jig and Fixture • Basic Principle of workholder • Identify the types of locators and support used fro jigs and fixtures

4. Purpose of tool design To improve efficiency and productivity To reduce cost

5. Jig & Fixture Hold & support guide the cutting tool. • references the cutting tool

6. Jig

7. COUNTERSINK&BORE

8. Fixtures

9. Permanent Jigs and Fixtures

10. Modular Fixtures

11. Drill jig and milling fixture.

12. NON-MACHINING APPLICATIONS • Assembly   • Welding fixtures • Inspection   • Mechanical-inspection fixtures   • Optical-inspection fixtures   • Electronic-inspection fixtures

13. Go - No go gage

14. Tool Design Tool Design

16. Work Holding Principles • Purpose and function of work holders • Consistently position workpiece relative to the tool • Hold workpiece in position against tool forces • Restrict deflection of the workpiece due to tool and holding forces

17. Locating principles • A locator is usually a fixed part of a fixture, the purpose of which is to restrict movement of the workpiece. • A clamp is a moveable part of a fixture, the purpose of which is to provide a holding force. • A support is a fixed or moveable part of a fixture, the purpose of which is to prevent workpiece deflection under the action of imposed cutting forces or clamping forces.

18. Clamp Support Locator

19. The Locating Process: Degrees of Freedom Translational Rotational.

20. Two objectives when mounting a part in a fixture for machining: • 1. Accurately position the part at the desired coordinates. • 2. Restrict all six degrees of freedom so that the part cannot move.

21. First Plane 3-2-1 Principle First Plane

22. 3-2-1 Principle TIPS• Use the largest surface of the part for the first ("primary") reference plane.• Position the three support points as far apart as possible.• If more than three support points are required to prevent deflection, make the additional points adjustable.

23. Second Plane

24. Third Plane If more than one support point is required to prevent deflection, make the additional points adjustable.

25. 3-2-1 9 degrees fix

26. Positioning Locators

27. BASIC PRINCIPLES OF LOCATING • To perform properly, workholders must accurately and consistently position the workpiece relative to the cutting tool, part after part. To accomplish this, the locators must ensure that the workpiece is properly referencedand the process is repeatable.

28. Referencing and Repeatability • Workpiece should automatically come to rest against locators despite operators skill or effort. • Location system must consistently position all workpieces in relations to the tool despite the variations in the working environment. • e.g. surface irregularities, wear of locators, dirt, temperatures difference.

29. 1. Establishing a locating plane • Surface should be machined to insure accurate location • Choose locating point as far as possible.

30. 2. Part size • Number of locator used to reference a part normally depends on the part size. • 3-2-1 principle determines the minimum number required • When holding force cannot be applied more than six locators can be used • Less operator skill is required when placing the workpiece in the holder • To Increase center line control

31. 3. Stability • Workpiece is unstable when placed on the locators, the workpiece tends to lift or rock away from one or more locators. • Place locators far for more stability and to minimize the effect of wear of locators and workpiece irregularity. • Top heavy workpiece may led to stability • Poorly placed holding force • Not enough locators

32. 4. Cutting pressures • Try to place locator opposite of the tool force to avoid deflection of the workpiece. • Where possible, tool-forces should be such that they force the workpiece into contact with the locators. • Holding forces should not be in the opposite direction to the tool forces

33. 6. Fool-proofing • Process of position locators such that part will only fit in the proper position. Achieved by foolproofing pin.

34. Chip removal • Chips and burr on locating surface can cause wear and disturb proper location. • 1. Make locators easy to clean 2. Make them self cleaning 3. Protect them

35. Chips can be swept easily

36. Controlling Chips

37. Sharp locators • Burr and Chip Relief

39. Summary: • Clamping Rules of Thumb• Define three reference planes on the workpiece and fixture.• Provide one opposing clamping force opposite each plane to restrict movement.• When in doubt, rely on additional cylinders to take up uncertainty.

40. . Types of workpiece location

41. C) Radail Location

42. Radial location • Supplement to the concentric locators to provide a specified fixed relationship to the concentric locator.

43. Combined location • Most workholders use a combination of locational methods to completely locate a workpiece.

44. Basic types of locators • 1. External locators • Devices used to locate the part from external surface. • Two basic forms of external locators are fixed or adjustable.

45. External Surfaces

46. Commercial Locating pins • easily available in market,

47. Adjustable support • Threaded type adjustable supports

48. Spring type adjustable support with locking nut

49. Internal locators • For locating holes and bored diameters – usually located internal surfaces. • Fixed locators – machined to suit specific size when the size variations are not large – example: base plate • Compensating locators: conical and self adjusting

50. Integral locators • Locators which are machined into the body of the work holder. • Disadvantage – extra time for machining and no replacement for wear or damaged locators