Injection Molding defect:molding crack

Solving molding crack problems

Definition
Cracking can cause part failure, a short part life and be visually unacceptable.
Cracks may not be obvious until several days or weeks after production. Hence, it is better to recognize and remove the potential problem of cracking before production. Moldflow Plastics Insight provides detailed shear stress results. molding crack

Causes
High residual stresses
Cracks may occur in regions where internal shear stresses are frozen into the part.
Weld line weaknesses
Differential shrinkage
Differential orientation, packing and cooling cause differential shrinkage resulting in high internal stress levels being frozen in.

Remedies
Minimize residual stress
Program the ram speed or increase wall thickness to reduce flow induced stresses. Check for the recommended maximum shear stress value for the material (recorded in the Materials Database)
Minimize differential shrinkage
Solving one problem can often introduce other problems to the injection molding process. Each option hence requires consideration of all relevant aspects of the mold design specification.