Investment casting may seem like a fairly simple process on the surface, but it requires significant experience and expertise to avoid investment casting defects. Here are four common types of defects:
Misrun – occurs when the molten alloy does not completely fill the mold, causing a rounded, smooth edge. This can occur when the mold is too cool, the alloy is too cool, or the mold is filled too slowly.
Shrinkage Cracks – also called hot tears, these are irregular cracks that result when the molten alloy is prevented from contracting by the mold during cooling and solidification. Adjusting the casting design often remedies the defect.
Porosity – occurs when gas trapped in the molten alloy is expelled as the casting cools, leaving pores in the part, possibly compromising its integrity. It can usually be corrected by proper handling of the molten alloy.
Cold Shut – can happen when multiple alloy streams do not fuse properly in the mold during pouring. It creates a weak area or discontinuity in the casting. Too cool molds or alloys or too slow pour rates can be the cause.