This is true I have gone through this problem not in one company but in many, from the period when I started carrier from trainee engineer. Here are some techniques I used to troubleshooting this kind of issue through process. (By considering that injection mold design and mold maintenance is ok in all aspects)
  • Decrease the shot wt. Decrease the hold pressure at starting.
  • If cold water circulation required in injection mold, keep it off initially.
  • Increase the cooling time 4-5 secs for startup.
  • Ensure the purging of barrel for degrading material.
  • Dipper cavity mold, optimize injection mold initial opening speed some vacuum pull back component to cavity.
  • After repair of injection mold, ejector plate become much free in movement, (as all the contamination has cleaned, and if ejector rod is not coupling type). When injection mold clamping drops to zero, ejector plate move forward push the component to cavity.
There is a law for warpage but unfortunately it does not take you much further forward. It is that warping is proportional to internal stress in the molded plastic part. There is always going to be a lot of that because conventional plastic injection molding is a forceful process thanks to the very high viscosity of the plastics melt. It involves, inter alia, high pressures on compressible materials, high shear stresses on long tangled molecules, large temperature gradients in conflict with poor thermal conductivity, and movement constraints applied by some but not all parts of the plastic injection mold. It is allied to shrinkage: indeed many authorities have defined warpage as non-uniform shrinkage. So within your particular scenario of product geometry, material choice, injection mold design and process conditions, it will help to think about ways of reducing shrinkage magnitude and variation. Which element will have the major influence depends so much on the scenario, which is why the general law does not help much.
Moldflow is wonderful and is true that it is absolutely useful tool, specially when driven by knowledgeable user. However please ask your team a simple question "How close to best in class is your cycle time after moldflow?"

Moldflow is vastly market leader and every technical director demands moldflow from engineering team. After this is done, you visit shop floor, there is never a case that parts were right as with dimensions and warpage and cycle time. Molding tools are predominantly built without conformal cooling and will have warpage in a part with uniform wall thickness that every trainee engineer will design with?
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