how to make good plastic injection moulds?

Hi Alice
In order to get good IMM molds the part design and mold design must be scrutinize to the smallest detail. The mold designer must be well diverse and be able to accept input. The mold design must be completed before any steel is cut. (My personal experience which expands over 20 years and worked with Consultant, molding shop, and mold make all over the world, I’ve only meet few designer with these qualities)
The second part would be the shooing of the different steels that will be use in the mold making process were you will still work with the designer and a technical development consultant from the resin manufacturer, the representative of the resin manufacturer will have several tools at your disposal even though that this tools are diminishing due to cost and head count reduction. The representative should bring choices for resins related to performance and shrinkage in addition to related knowledge to gating, hot runners and over all process ability of the resin choices. The representative should also be able to help and or run the mold test after the mold is complete. (If you can get the correct individual) This step is curtail if the resin has filler, additives, compatibleness, color and if the resin is acidic, abrasive, adhesive, or extremely tough
The tool maker must be willing to be a active part of the process and be able to interact with the part owner and the designer as he will change some aspect of the design as his input on the mold making process can aid of fail the project, but he will change some aspects of the design.
The important component of the process is that the design relates to the mold as the mold control the appearance, dimension and cycle of the part during the molding process.
Regards,
JCM