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Fixture Design

Hold

Locate

Support

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General Considerations

Cost vs. Benefit

Fixture Required

Economics

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Machine considerations

Machine tool info

Condition of workpiece

Which one moves?

Weight and size

Proper tool for the Job?

Larger tool?

Standard cutters

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Process Considerations

Best Method

Fast operation

Holding force vs.cutting forces

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Product Considerations

What does product allow?

Location and clamping surfaces

Areas to machine and precision Changes earlier rather than later

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Types of Fixtures

Classified by machine

Classified by process

Five major groups Plate

Angle-plate

Vise-jaw

Indexing

Multipart

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Plate

Plate

Locators Clamps

Supports

Most common

Material guided by

requirements

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Angle plate

Modified plate

Perpendicular to base May be at other angle

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Vise-jaw

Modified law inserts

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Indexing

Prescribed spacing offeatures

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Multi-part

Sequential operation

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Fixture Classifications

Classified by process

Milling fixtures

Lathe fixtures

Grinding Fixtures

Surface grinding fixtures

Cylindrical grinding fixtures

Boring fixtures

Broaching fixtures

Sawing fixtures

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Milling fixtures

Machine as many surfaces as possible

Change cutter; not move part

Locators resist forces

Space to work inside

Low profile

Worpiece inside fixture

Chip removal and drainage

Provide set blocks or gages

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Lathe fixtures

Lightweight as possible

Balanced

Sharp cornersYow!

Grip by largest diameter

Machine in one fixturing

Clamp to rigid surfaces

Cutter setting incorporated

Standard parts

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Surface grinding fixtures

Similar to milling fixtures higher precision

Magnetic chuck; fixture is corral

Coolant/sludge removal

Coolant containment

Remember, ferrous materials

Wheel dress, true provisions

Locators

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Cylindrical grinding fixtures

Similar to lathe fixtures

May use same centers as lathe work

Sludge removal

Balanced

Standard parts

Wheel dressing and truing

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Boring fixtures

Large parts

Tool setting

Alignment areas

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Broaching fixtures

Hold part relative to tool

More substantial; more force

Internal easier; just hold on Push-pull method keeps part put.

External requires more clamping and location

Resist different forces

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Sawing fixtures

Standard parts

Keep clear of the blade

Coolant / chip control

Referrence fixture to table/blade

Power feed when possible

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Standard mounting of fixtures

T-slots, t-bolts, straps, clamps

Most machines can handle these

Chucks, arbors, collets

Standard components lower costs

Solidly located on the machine

Wasting your time otherwise

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Relationship between fixture andcutting tool

Minimize forces and moments

Motion may change tool angles

Removal of material tospecification

Control with stops?

Setting gage

Dont cut vise or fixture

Dont cut air

Ample space to load / unload

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Tool positioning

Relationship to locators

Used to properly position part

Cutter-setting devices

Gage or setup blocks

Clear by 0.03 min

Mark feeler size near block

Optical methods

Center finder

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Cutter Setting

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Design Fundamentals

View workpiece as a whole

Gather all necessary data

Consider standard workholders Determine need for specials

Study fixtures for similar operations

Review fixturing plan

Execute fixturing plan

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Similar Operations

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Fixture Design process

Sketch part

3.0x2.0x1.0 6061-T6Aluminum

Cut from 1.0 x 2.0 barto 3.0 0.005

750 parts per month

Permanent tool;minimum cost

Horizontal mill (gangmill)

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Fixture Design process

Add locators and baseplate

Aluminum?

Steel?

Dowels

Block?

Fixture keys

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Fixture Design process

Add set block

Remember to allow for

feeler gage

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Fixture Design process

Clamp?

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Fixture Design process

Add cutters

Check clearances

Final drawings