Injection Molding 5 Lessons Learned(2)

Today, I will share the remaining lessons about injection molding with you.

Lesson 3: Not verifying fill only weight at startup. To replicate the fill portion of the cycle we need to know how much material we injected and how long it took. The two tools we will use to evaluate the fill is the fill time and the fill only part weight. By matching the fill time and fill only part weight we know that the same amount of plastic has been injected over the same time. By using these two pieces of data we have a result that gives us weight injected/fill time which can be converted to a volumetric flow rate. To keep a consistent process we must know that this volumetric flow rate is the same from shot to shot and run to run.

Lesson 4: To conduct a gate seal study first remove the runners. This can trip people up when running a gate seal study, we are concerned about the part side of the gate not the runners! If you are weighing the gate seal parts with runners you will be conducting a runner/sprue seal study. We are not concerned about if the runners can be packed more we are concerned about packing the part.

Lesson 5: Steel hand tools in the mold cavity. Do not allow the mentality of “I have done this for years” to override the right thing to do, all it takes is one slip. The lesson here is no steel tools in the mold and buy your techs the brass and bronze tools they need. Years ago I ran into a couple of cases where when we reviewed the mold damage it was possible to lay a pair nippers perfectly into the gouge on the parting line. This is a risk that is really not worth taking, the potential damage may cause scrap or downtime plus the expense of repair.

These are all lessons I like, hoping is useful for you!