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Precision Molding: Three Issues That Can Save You Money

Views: 4     Author: Site Editor     Publish Time: 2022-10-26      Origin: Site

If you need to mold a product part with extreme precision - for example, to ensure that there are no air leaks between two molded parts or that there are no visible seal gap lines - you may need precision molding. The difference between normal mold molding and precision molding is the range of tolerances or acceptable dimensional variations: while most molds have tolerances of +/- .005", precision mold molding has tolerances of +/- .002" and +/- .001" (or less in some cases).


For example, let's say you plan to manufacture military projectiles. For the projectile to fit properly in the firearm, handle acceleration on launch, and explode on impact, it requires high precision.

precision molding parts


If your application requires precision molding, you can't afford to take any chances - so before you start the process, you need to ask yourself the following three questions.


1. Are you sure which areas of the mold need precision?

Because precision molding is more expensive than typical mold molding, determine what areas of the part require tight tolerances and whether those tolerances can be achieved through injection molding before moving forward. For example, a surgical handle may only require precision for the part attached to the pin, not the entire handle. Determining your accuracy requirements from the outset ensures you get what you need without wasting money.


2. Have you chosen a material with a low shrinkage rate?

The material you choose for your part can greatly impact whether you can perform precision molding. For example, polypropylene has a shrinkage range of +/- .014" to +/- .022", with an average of +/- .018". This is a very wide shrinkage range, making it difficult to achieve specific tolerances. If you are molding a toothbrush (usually polypropylene), handling shrinkage is not a big issue because it works fine whether the toothbrush is slightly larger or smaller than its counterpart. Acrylonitrile butadiene styrene (ABS) - another common thermoplastic polymer - has a much narrower average shrinkage of +/- 0.006. This gives you a better chance of achieving tighter tolerances, but it still won't achieve the +/- .001" or +/- .002" tolerances required for precision parts.


One way to achieve high tolerances with plastic materials is to add glass or other filler resins (such as carbon fiber or mica) to the material. This can minimize shrinkage and warpage by providing more structure in the material. For example, if you include long glass fibers in a polymer material, the part will shrink more perpendicular to those fibers.


3. Can the mold maker choose a high-precision mold?

The process of making parts with tight tolerances begins with high-precision tooling. If every plastic part you create is different, you won't get an accurate product - and accurate tooling ensures that there is no variation in every part. That's why it's important to choose a mold maker who understands the slow, steady process of making high-precision tools. Remember that choosing a mold maker specializing in rapid tooling may not be your best choice, as the goal of rapid tooling is to get the mold done quickly but not necessarily accurately.


Knowing the above 3 issues before making custom precision molds can help you finish your molds faster and better, but the more important thing is to choose the right precision molding supplier. If you are hesitating to choose which manufacturer is good, Shengqi is a good choice.


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