Plastic mold factory introduces some problems and solutions.

Problem: Inadequate Injection Pressure or Time

If there is not enough injection pressure the plastic material will cool and solidify before the mold is properly packed.

If there is inadequate mold injection hold time, the packing process is minimized.

If there is inadequate mold injection pressure or hold time the molecules will not be constrained, which allows them to move around uncontrolled during the cooling process. This causes the part to cool at different rates and results in mold warpage.

Solution: Increase mold injection pressure or hold time.

Problem: Inadequate Residence Time

Residence time is the amount of time the resin is exposed to heat in the barrel. If there is inadequate residence time the molecules will not absorb heat uniformly throughout the material. The under-heated material will become stiff and will cool before the mold is properly packed. This causes the molecules to shrink at different rates during the cooling process which results in mold warpage.

Solution: Increase residence time by adding time to the cooling process of the cycle. This will ensure the material receives the proper amount of residence time and eliminate mold warping.


Problem: Barrel Temperature too Low

If the barrel temperature is too low, the resin is not able to heat up to the proper flow temperature. If the resin is not at proper flow temperature and is pushed into the mold it will solidify before the molecules are properly packed. This causes the molecules to shrink at varying rates which produces mold warpage.

Solution: Increase barrel temperature. Make sure material melt temperature is homogenous for the entire shot size.


Problem: Mold Temperature Too Low

If there is insufficient mold temperature the molecules will solidify prior to packing and at different rates, causing mold warpage.

Solution: Increase mold temperature based on the resin supplier’s recommendations and adjust accordingly. In order to allow the process to re-stabilize, operators should allow 10 cycles for every 10 degree change.

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