The Injection Molding Process: Part Two
How change can affect the injection molding process
Part Design – Depending on the significance of the change, it may improve or decrease your ability to optimize the molding process. Inspection data should be collected to verify the molding process is still acceptable.
Material – Material change from lot to lot should be tracked but if the brand or type of material is changed, this may affect the material shrinkage and dimensional stability. Inspection data should be collected to verify the molding process is still acceptable after the material change.
Mold Design/Construction – Repair, refurbishment or improvement to a mold can help prolong the life of the mold, but depending on the complexity of the mold, changes may or may not improve the stability of the molding process. Startup inspection will verify the mold is still qualified. Inspection data should be collected to verify the molding process is still acceptable after the mold modification.
Machine – A machine with a similar barrel size and clamp tonnage should not impact the process, however, the startup and set up may need to be updated for the machine to run an optimal process. Startup inspection will verify the mold set up in the alternate machine is qualified to run the mold. Inspection data for the production lots using the alternate machine should be collected to verify the machine is reliable in producing consistent results.
Production Process Set-up – Injection Molded plastic parts shrink as they cool. The amount or way they shrink is dependent on the material flow behavior. Once we modify the original production set-up in a way that affects the material flow behavior in order to compensate for a certain deficient dimension or feature, we will affect the entire molded part (all dimensions and features) and run the risk of other dimensions or features running out of specification as well as jeopardize our ability to make consistent, dimensionally stable parts.