Injection Mold Design Tips To Save You Money

These simple injection mold design tips will increase your chance of success in every way. Injection mold making is difficult at best, a good 3D injection mold design will give you a solid foundation. For a full tutorial on mold design, check out the Mold Design Tutorial, highly recommended.

With a solid design your mold maker will be confident that the components all fit, the dimensions work together, and that the mold will ultimately function as it should. It is maddening for the mold maker to begin second guessing the design and needing to constantly refer to the CAD file or designer.

The injection molding engineer will have confidence in the injection mold design and the operation of the mold itself. You molder won’t be second guessing the design and it will help him process the parts.

Most of all, your customer will be delighted with a clean, flash-free, dimensionally correct plastic part.

Mold Design Tips
Mold design

I asked an experienced mold designer for a few tips to pass on and he surprised me with the simplicity of his answer.

Injection mold design tips

  • A good design must be practical. The mold maker must be able to produce the components in a logical, orderly manner to make money. Often, close tolerance dimensions are specified when a much looser tolerance could have easily done the job.
    Take an ejector pin plate, for example. Everyone knows that the thickness is basically irrelevant, but usually the dimension given is a close tolerance size. An experienced toolmaker will just ignore the tolerance and proceed, but nowadays, with the specialization of tasks in the shop, a less skilled operator would waste precious time holding an unreasonable tolerance.
  • The 3D geometry must be clean. The fast pace of mold making today makes it essential to have efficient, reliable software. The days of vague sketches, or toolmakers making up the design as they go are long gone. There are many excellent companies that offer high end software programs for designing molds, dies, and just about any kind of tooling you can imagine.
    CNC machines need clean geometry to run properly. If the design is sloppy and the translation of different software messy, the end result will show it. Plus, the operator will have a much easier time running the programs with clean geometry.
  • The design must be clear in it’s function. It is maddening for a plastic injection mold maker to spend hours deciphering what the designer means. Information that is assumed or omitted can delay the construction by days and cause unnecessary errors. Why should a toolmaker spend time looking up information that was right in front of the designer at one time?
    It is always much easier to include notes or details that show what is required than to search it out later on. Once the design is in process, and the information is available, why not simply give the mold maker the same information? For example, a 3D drawing can visually clarify many questions.
Mold Design Tips
Hasco Standard Components

Obviously there are many other tips that are more specific, here is a mold design checklist to help.

Injection mold design is complex and allows no room for error. Investing in a quality training tool, such as the Injection Mold Design Tutorial makes sense for everyone in the design department.

Whether you are a veteran designer or novice, there is always more to learn. Parting lines, water lines, gates, runners, shut-offs, lifters, slides, venting, textures, manufacturablility, shrinkage, fits and function are just few of the many considerations.


  1. It makes sense that you have to have a good design to make a decent mold. If it doesn’t work well, the mold won’t make things well. You have to make sure that the shape is clean and precise.

  2. This is a very good guide and something everyone looking to design something to be moulded should read!

  3. I do agree that the design must be clear in its function since it will cause a lot of issues when made vague. If I’d ever need one, I’ll be sure to take your article in mind. Thanks for the great read!

  4. I am hoping to open a cosmetic line soon. For some of the products, I will be needing to use injection molding. Like you suggested, I will be sure to consider the features of the mold that will allow it to hold up over time to be more durable. Thanks for sharing!

  5. I’ve always been fascinated with injection molding since you really can make anything that you can design the mold for. Now as you said, the mold must be clean so that when the molding is done, you will have a complete product without any imperfections. If I was doing something like that, I’d also be sure that the functionality of the finished product will work and not be broken.

  6. Hello,
    I am looking MIM mold designer ?

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