JIGS AND FIXTURES Jigs and Fixtures are Production-work holding devices used to manufacture duplicate parts accurately

A Jig is a special device that holds the workpiece but also guides the cutting tool as the operation is performed

A Fixture is a production tool that locates, holds, and supports the work securely so the required machining operations can be performed

Elements of Jigs and FixturesLocating Elements: These position the workpiece accurately with respect to the tool guiding or setting elements in the fixture.Clamping Elements: These hold the workpiece securely in the located position during operation.Tool Guiding and Setting Elements: These aid guiding of the tool in the correct position with respect to workpiece.

Advantages of Jigs and FixturesProductivity

Interchangeability

Skill Reduction

Cost Reduction

Jigs and Fixture Design Factor1. Study of the component.2. Study of the type of the capacity of the m/c.3. Study the locating elements.4. Study of the clamping arrangement.5. Study of clearance between jig and the component.6. Study of the indexing devices.7. Study of the fool-proofing arrangement.8. Study of the ejecting devices.9. Study of the swarf removal arrangement.10.Study of rigidity and the vibration problems.11.Study the safety devices.12.Study the methods of manufacture of jigs and fixture.

Supporting and Locating PrinciplesPositioning the Locators: Whenever possible, locators should contact the work on a machined surface. This permits accurate placement of the part in the tool and ensures the repeatability of the jig or fixture. Basic Rules for Locating PART WRONG METHOD RIGHT METHOD

2. Tolerance: When designing a tool, the designer must keep the part-tolerance in mind. As a general rule, the tool tolerance should be between 20 and 50 percent of the part tolerance.

3. Fool proofing: Fooling proofing is means by which the tool designer should ensures that the part will fit into the tool only in its correct position.

Locating Methods1. Location from Plane surface:

2. Location from Profile:

3. Location from CylinderPrevention of JammingRecess for burr and dirt

Diamond Pin Locator Diamond pins are the two way locating devices, because they only locates in one axis. Diamond locating pins are used in conjunction with a round locating pin. The round pin holds the workpiece in position to the fixture, and the diamond pin holds the workpiece to keep it from rotating around the round pin.

Restricting MovementsSix-point Location by 3-2-1 Method

Three-pin base restricts six directions of movement

Five-pin base restricts ten directions of movement

six-pin base restricts twelve directions of movement

Clamping and Positioning The function of any clamping device is that of applying and maintaining sufficient counteracting holding force to a workpiece to withstand all tooling forces

Swinging clampTypes of clampStrap clamp

Hinge clampSpherical washers for equalizing clamping forces.Pivoted strap clamp

Edge strap clampQuick acting screw clamps.Edge jaw clamp

Swinging strap clampSwinging hook clamp

T-Slot clampEdge clamp

Method of clamping a small crankshaft by use of a sliding clamp and equalizing pivoting clamp.

Quick acting clamps

Hinge clampVice

Rack and pinion

Universal chuck Magnetic work holding devices

TYPES OF JIGS

CLAMP JIGDIAMETER JIG

CHANNEL JIGLEAF JIG

PLATE JIGJIG FOR MULTISPINDLE MACHINE