Fixture Design General Considerations Hold Cost vs. Benefit Locate Fixture Required Support Economics MFG316 Chapter 6 MFG316 Chapter 6 Machine considerations Process Considerations Machine tool info Best Method Condition of workpiece Fast operation Which one moves? Holding force vs. Weight and size cutting forces Proper tool for the Job? Larger tool? Standard cutters MFG316 Chapter 6 MFG316 Chapter 6 Product Considerations Types of Fixtures What does product allow? Classified by machine Location and clamping surfaces Classified by process Areas to machine and precision Five major groups Changes earlier rather than later Plate Angle-plate Vise-jaw Indexing Multipart MFG316 Chapter 6 MFG316 Chapter 6 1 Plate Angle plate Plate Modified plate Locators Perpendicular to base Clamps May be at other angle Supports Most common Material guided by requirements MFG316 Chapter 6 MFG316 Chapter 6 Vise-jaw Indexing Modified law inserts Prescribed spacing of features MFG316 Chapter 6 MFG316 Chapter 6 Multi-part Fixture Classifications Sequential operation Classified by process Milling fixtures Lathe fixtures Grinding Fixtures Surface grinding fixtures Cylindrical grinding fixtures Boring fixtures Broaching fixtures Sawing fixtures MFG316 Chapter 6 MFG316 Chapter 6 2 Milling fixtures Lathe fixtures Machine as many surfaces as possible Lightweight as possible Change cutter; not move part Balanced Locators resist forces Sharp corners—Yow! Space to work inside Grip by largest diameter Low profile Machine in one fixturing Worpiece inside fixture Clamp to rigid surfaces Chip removal and drainage Cutter setting incorporated Provide set blocks or gages Standard parts… MFG316 Chapter 6 MFG316 Chapter 6 Surface grinding fixtures Cylindrical grinding fixtures Similar to milling fixtures higher precision Similar to lathe fixtures Magnetic chuck; fixture is corral May use same centers as lathe work Coolant/sludge removal Sludge removal Coolant containment Balanced Remember, ferrous materials Standard parts Wheel dress, true provisions Wheel dressing and truing Locators MFG316 Chapter 6 MFG316 Chapter 6 Boring fixtures Broaching fixtures Large parts Hold part relative to tool Tool setting More substantial; more force Alignment areas Internal easier; just hold on… Push-pull method keeps part put. External requires more clamping and location Resist different forces MFG316 Chapter 6 MFG316 Chapter 6 3 Sawing fixtures Standard mounting of fixtures Standard parts T-slots, t-bolts, straps, clamps Keep clear of the blade Most machines can handle these Coolant / chip control Chucks, arbors, collets Referrence fixture to table/blade Standard components lower costs Power feed when possible Solidly located on the machine Wasting your time otherwise MFG316 Chapter 6 MFG316 Chapter 6 Relationship between fixture and cutting tool Tool positioning Minimize forces and moments Relationship to locators Motion may change tool angles Used to properly position part Removal of material to Cutter-setting devices specification Gage or setup blocks Control with stops? Clear by 0.03 min Setting gage Mark feeler size near block Don’t cut vise or fixture Don’t cut air Optical methods Ample space to load / unload Center finder MFG316 Chapter 6 MFG316 Chapter 6 Cutter Setting 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 MFG316 Chapter 6 MFG316 Chapter 6 4 Similar Operations Fixture Design process Sketch part 3.0x2.0x1.0 6061-T6 Aluminum Cut from 1.0 x 2.0 bar to 3.0 ± 0.005 750 parts per month Permanent tool; minimum cost Horizontal mill (gang mill) MFG316 Chapter 6 MFG316 Chapter 6 Fixture Design process Fixture Design process Add locators and base Add set block plate Remember to allow for Aluminum? feeler gage Steel? Dowels Block? Fixture keys MFG316 Chapter 6 MFG316 Chapter 6 Fixture Design process Fixture Design process Clamp? Add cutters Check clearances Final drawings MFG316 Chapter 6 MFG316 Chapter 6 5.