Making a super high precision injection mold is only part of the formula required to produce high precision plastic parts.
The plastic injection molding process is just as critical, if not more so, and needs to be developed in conjunction with the tooling. This may include steel safe considerations to allow the critical dimensions to be dialed in. It is also very critical that they have the plastic molding equipment necessary to maintain an extremely stable plastic injection molding process.
Also part design is critical. You cannot get precision plastic parts if the part design is poorly engineered. Be sure to closely follow design recommendation for the materials you are using. This also needs to be developed in conjunction with the plastic injection mold design (Gate, ejector and P/L locations to name a few).
Speaking of materials, the material selection process is also critical for precision plastic parts. Picking a material with large shrinkage values only exacerbates the problem of maintaining a consistent injection molding process. Try to choose materials with low shrinkage values (Filled if possible) that also meet the mechanical/chemical/thermal performance criteria of the precision plastic part.
Then, if all these things are in place, you still need a company that has the procedures in place to allow for high precision injection molding. This will require an audit of all of the processes in their companies, preferably by someone with experience in the industry, from how they inspect and verify incoming materials through manufacturing/WIP/QC, into overall QC, through packaging and shipping to your company.
But be careful here as well. It is not always the best looking candidates that make the best partners. The thing here is even when properly trained personal audit a plastic molding company and confirm the appropriate procedures are in place, you still won’t know for sure that they actually follow those procedures. This is where the recommendations help and a slow careful approach is required.
Precision Injection Molding in China
Precision molding means many different things to many people. There are plastic molding shops in China which have state of the art equipment, equal to the best of the injection mold makers in the US, Germany, Switzerland or Japan. The same is true of the precision molding machines and injection molding companies. There are companies in China which are capable to produce state of the art molds and precision molded plastic parts. The Chinese are getting better and better every year.
But the equipment is only part of the equation. It still takes a very talented and experienced individual to control and monitor the precision plastic injection molding processes and procedures. You need to evaluate the infrastructure top to bottom and also insist on the proper certifications for quality and documentation suitable to your field of business.
To make a decision of the actual capabilities of the precision mold maker or molding company will certainly require a personal visit and verification by a 3rd party customer of these companies as to the successful execution of similar parts to your expected part and your required tolerances. You will also need confirmation from the material (resin) manufacturer that the specified material is capable of producing to your custom plastic parts.
Anyone from a molder or mold maker who has responded to you “yes we can do that” without ever seeing the 3D model and 2D detailed drawing should immediately be scratched from list of potential suppliers.
Any commitment from your end must be written such as to attach the payment terms of the precision mold to performance of the injection mold and required tolerance of the precision plastic parts.
I have spent an extensive amount of time in China Shenzhen, Dongguan and Chang’An town building mold for automotive interior appearance parts and I believe there is a good possibility you can find what you need there. Bottom line is taking a slow, careful and thoughtful approach when looking for a high precision plastic injection molding company.