Fixtures work holding and locating device used with machine tooldevice.pptx

Fixtures work holding devices, jigs , fixtures

1. Fixtures

2. Fixture Fixture is a workpiece-locating and holding device used with machine tools. It is also used in inspection welding and assembly Fixture does not guide the cutting tool, but is always fixed to machine or bench. By using fixture, responsibility for accuracy shifts from the operator to the construction of machine tool

3. Design Consideration in Fixtures Frame : Strong enough to sustain deflection Sufficient Mass Simple sections – Ease in assembly For Complex shapes – Cast Clamping : Fast and easy Arrangement – readily available and easily removable Springs wherever possible If swings  swing FarRemoval should be made easy Visibility and Accessibility Same wrench for all clamps and support pins Chip removal

4. Design Consideration in Fixtures Workpiece Stability: If Rough  3 fixed support points If Smooth  May be > 3 support points Support point should be placed as farthest as possible from each other 3 support points should circumscribe the centre of gravity of the workpiece. The surface area of contact of support should not damage w/p Support points and other parts are designed in such a way that they may be easily replaced if they break

5. Based on the type of component used

6. INDEXING FIXTURE A fixture that changes position with regular step like movements. IN Indexing fixture following factors are considered The work piece should be positively located and clamped on the fixture independently of the indexing mechanism should be both rapid in action and positive in location Care should be taken to prevent chips affecting the accuracy or functioning of the indexing device

7. Vise jaw fixtures

8. Multipart fixture

9. Based on operation performed

10. Milling Fixtures

11. Milling Fixtures

12. Milling Fixtures

13. Milling Fixtures

14. Milling Fixture- Elements A base plate has a flat and accurate undersurface and forms main body on which various components are mounted. This surface aligns with the surface of the mill table and forms the reference plane with respect to the mill feed movement

15. T-Bolt and slots

16. Setting blocks After the fixture has been securely clamped to the machine table , the work piece which is correctly located in the fixture , has to be set in correct relationship to the cutters. This is achieved by the use of setting blocks and feeler gauges . The setting blocks is fixed to the fixture. Feeler gauges are placed between the cutter and refrence planes on the setting block so that the correct depth of the cut and correct lateral setting is obtained.

17. Some principles 1: Pressure of cut should always be against the solid part of the fixture(fig 1). 2: Clamps should always operates from the front of the fixture (fig 2) 3: The work piece should be supported as near the tool thrust as possible(fig 3)