| Common defects and solutions for MIM molding |
| | | |
| Defect | Potential causes | Potential solution |
| Blistering | Improperly dried material | Dry hygroscopic material |
| | | Reduce humidity in plant |
| Blistering | Poor heat removal from tool | Increase cycle time |
| | | Reduce mold temperature |
| | | Reduce melt temperture |
| | | More cooling channels in tool |
| | | Higher thermal conductivity mold components |
| Blistering | Localized shear heating | Reduce injection speed |
| | | Large gates to reduce shear heating |
| Blistering | Polymer degradation | Use higher MW polymers |
| | | Use antioxidant in binder |
| Cracking | Ejection issue | Increase mold temperature |
| | | Reduce pack pressure |
| | | Decrease melt temperature |
| | | Polish tool |
| Cracking after solvent | Molded in stress | Increase venting |
| | | Increase mold temperature |
| | | Post mold anneal |
| Flash | Tooling not closed | Adjust tooling for better clamping |
| | | Worn tooling, dress parting line |
| | | Clean mold faces of dirt |
| Flash | Too low clamp tonnage | Higher tonnage machine |
| | | Reduce injection pressure by slowing injection |
| | | Reduce pack pressure |
| Flash | Material viscosity | Increase viscosity by increasing solids loading (will cause shrinkage change) |
| | |
| | | Increase viscosity by high molecular weight polymers |
| Gate blemish | Powder/binder separation at gate | Decrease injection speed |
| | | Decrease pack pressure |
| Incomplete fill | Insufficient material in cavity prior to gate freeze | Increase shot size |
| | Increase pack pressure |
| | | Increase injection speed |
| | | Increase venting |
| | | Increase melt temperature |
| | | Increase mold temperature |
| Incomplete fill | Material feed issue | Decrease backpressure on recovery |
| | | Decrease size of feedstock and regrind |
| | | Dry material for hygroscopic material |
| | | Decrease fines in feedstock |
| Sinks | Poorly filled part | Increase pack pressure or pack time |
| | | Increase gate size |
| | | Increase backpressure for screw recovery |
| | | Decrease melt temperature to decrease material shrinkage |
| | | Increase melt temperature to allow greater fill |
| | | Increase venting |
| Variable component mass | Shot size variation | Clean check ring |
| | | Increase recovery backpressure |
| | | Increase cushion |
| Voids | Air entrapment | Decrease injection speed |
| | | Increase backpressure during recovery |
| | | Increase pack pressure and pack time |
| Warpage | Component distorts during ejection | Increase cool time |
| | Decrease mold temperature |
| | | Better cooling in tool |
| Warpage | Pressure gradient in component | Decrease hold pressure |
| Weld lines | Premature material solidification | Increase injection speed |
| | | Increase melt temperature |
| | | Increase pressure for switchcover to pack control |
| Weld lines | Gas entrapment in mold | Increase venting on part and runner |
| | | Decrease injection speed |
| Weld lines | Premature material solidification | Increase injection speed |
| | | Increase melt temperature |
