If can make a qualified plastic parts, does that mean the mold is qualified? The answer is MAYBE.
A good and qualified mold can bring profits for the injection company and can be tested by scientific methods.
How to design a good mold? First of all, we need to know what kind of mold is a “good mold”. We believe that every injection company has its own standard requirements.
From the aspect of forming economics, that is not yet truly meets the production standard requirements. Since there have understanding differences on injection molding between the mold making and injection molding department for their own conflict of interest, the typical cognitive bias is that mold making department staff think it just need adjust the process parameters, as long as the machine can bring qualified plastic parts. If can make a qualified product, then the mold definitely is okay. However, this is a misunderstanding for most mold designers and makers.
In order to ensure smooth production:
a) at the product design phase product designers and mold designers need to agree on the following basic information:
For example, the parting line position, core and cavity, gate position, gate number, shape, size, pin location, size, quantity, ejection etc.
Heat concentration points on the product, mold cooling water, size, location; product surface requirement (fire pattern, texture, polishing etc).
Fillet size and location; draft size and location; dimensional tolerance levels and so on.
b) From the perspective of forming process, as we know all molds must have such functions:
1) Forming parts, the core and cavities;
2) The gating system, runner and gates;
3) The access for the air expel from the cavities, the vent;
4) The cooling system;
5) The ejection system.
In order to meet the requirements of injection molding production process, mold design need consider the above five functions. The numbers of cavities classification, the flow balance, fractal surfaces and how to choose parting direction, how to determine the critical dimensions, the factors of gate design etc. From the technology perspective, what is the requirement for the exhaust? How to design a reasonable cooling and ejection system? And so on.
A qualified plastic mold design must consider the plastic products quality requirement and process property as well as whether it can bring profits to the injection company.