Good Plastic Injection Mold Design Is Essential For Success

The proper design of an plastic injection mold will increase your chance of success in every way. Injection molding is difficult at best, a good 3D design will give you the edge.

Your mold maker will be confident that the components all fit, the dimensions all work together, and that the mold will ultimately function as it should.

The injection molding engineer will have confidence in the 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.

A very good book on injection mold design is called "Understanding Injection Mold Design", by Herbert Rees, which is also very reasonably priced. You can read an independent review of the excellent book "Understanding Injection Mold Design" here.

What is important in good mold design?

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.

What about gates and runners in injection molds?

Here is a review of how to design gates and runners in an injection mold.

Find out about mold flow from this video

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Here are some recommended books for designers

• Understanding Injection Mold Design Book Review
  Independent review of a book on understanding injection mold design.
  
  
• How To Design Injection Molding Plastic Gates and Runners
  Learn tips to properly design injection molding plastic gates and runners. The wrong gate placement can make a huge difference in the end result.