Ever experience troubleshooting issues with investment casting? We have put together a list of possible defects, the cause and the solution that should solve the problem.
| Defect | Cause | Solution |
|---|---|---|
| Cracking | Quenching too soon | Wait 15-20 minutes |
| Cracking | Metal cast too soon | Increase casting temperature |
| Cracking | Flask too cold | Increase flask temperature |
| Cracking | Incorrect spruing | Modify sprueing |
| Cracking | Contamination of gold or alloy | Refine metal |
| Cracking | Oxide build up in metal, over-use | Refine metal |
| Cracking | Hydrochloric acid divesting | Use alternative di-vestor |
| Incomplete Fill | Metal too cold | Increase casting temperature |
| Incomplete Fill | Flask too cold | Increase flask temperature |
| Incomplete Fill | Insufficient vacuum | Check vacuum for leaks and seal |
| Incomplete Fill | Wrong speed on centrifugal caster | Adjust speed |
| Incomplete Fill | Insufficient burn out | Modify sprue |
| Incomplete Fill | Incomplete burn out | Use proper burn out schedule |
| Inclusions in castings | Sharp corners or bends in sprueing | Round out sharp corners and bends |
| Inclusions in castings | Crucible old and deteriorating | Replace Crucible |
| Inclusions in castings | Oxide build up in crucible | Clean or replace crucible |
| Inclusions in castings | Foreign particles or oxides in metal | Refine metal |
| Inclusions in castings | Investment erosion or breakdown | Follow investment manufacturer's mixing instructions |
| Brittle prongs on castings | Improperly alloyed metal | Pre-alloy gold and master alloy |
| Brittle prongs on castings | Flask temperature too cold | Increase flask tempretature |
| Shrinkage porosity | Incorrect sprueing | Sprue to heaviest area of casting |
| Shrinkage porosity | Inadequate sprueing | Use larger sprue or multiple sprues |
| Shrinkage porosity | Flask too hot | Use lower flask temperature |
| Shrinkage porosity | Castings too close to sprue button | Leave 1" space on tree above main sprue button |
| Gas porosity | Metal overheated | Reduce casting temperature |
| Gas porosity | Inadequate burn out | Increase top end burn out time |
| Gas porosity | Inadequate air supply during burn out | Assure oven has good air supply & exhaust |
| Gas porosity | Flask too hot | Reduce flask temperature |
| Gas porosity | Scrap reused too many times | Refine metal |
| Gas porosity | Too much oxygen on torch flame | Use reducing flame when melting |
| Gas porosity | Investment residue on remelted scrap | Remove investment residue before remelting scrap |
| Rough castings | Flasks not cured before burnout loading | Let flasks set 1-2 hrs. before burnout loading |
| Rough castings | Incorrect water/powder ratio in investment mix | Follow investment manufacturer's instructions |
| Rough castings | Flasks heated too rapidly | Follow investment manufacturer's instructions |
| Bubbles/nodules on castings | Investment not mixed, vacuumed or vibrated sufficiently | Follow investment manufacturer's instructions |
| Bubbles/nodules on castings | Vacuum pump not working properly | Check vacuum pump oil |
| Bubbles/nodules on castings | Wax patterns not coated with wetting agent | Coat wax patterns with wetting agent |