By Jason Vander Griendt

January 5, 2018 at 6:52 am

When it comes to the mass production of high dimensional tolerant Liquid Silicone Rubber (LSR) products, injection molding is the most commonly used technique. It doesn’t matter if the products are complex or simple. Having knowledge of the LSR’s behavior before the commencement of the processing helps in a number of ways.

Not only does it reduce cost, it also enhances the quality as well as the efficiency of the final product. In the silicone injection molding process, pressure and temperature are the two most important variables. They both have a definite and sometimes irreversible (in the case of a negative outcome) effect on the silicone’s behavior.

You should have a complete grasp of the knowledge of how pressure and temperature (especially temperature) affect the final LSR product before attempting silicone injection (better yet, outsource to professionals instead!). This will aid in minimizing the risk of defects including but not limited to warpage, sink marks, and shrinkage. During the injection molding process, the silicone compound’s curing behavior is largely influenced by temperature, even more than it is by pressure.

Problems That Can Arise In Silicone Injection Molding Due to Temperature and Their Solutions

Due to neglect, ignorance, or just by mistake, a number of temperature-related problems can occur during the silicone injection molding process. These problems can lead to defects in the curing of the silicone or in the final products. These problems, their signs, causes, and possible solutions are highlighted below:

  • Presence of lumps (or gelled particles) in finished product

If the tool temperature is too hot, you might notice that a part -or some parts- of the finished product appear gritty or lumpy. You might also notice that the cured sprue is visible inside the part. To solve this problem, reduce the tooling temperature at the gate.

  • Blisters or bubbles

There might also be visible blisters or small bubbles all over the finished product. Moreover, it might have white or foamy edges. This can also be the result of the tool temperature being too high. To solve this problem, reduce the tool temperature and the defects should be prevented.

  • Silicone isn’t cured

If after you have tried to cure the silicone, it still doesn’t portray all the signs of curing, there’s most likely a temperature problem. If the molded parts have a tacky feel or stick in the cavity, it means the tool temperature is probably too low. Increase the tool temperature, or check each individual cavity for temperature consistency. This should help to fix the problem.

  • Incorrect part dimensions

If the finished parts come out too large or too small or they’re deformed, the problem might be caused by insufficient curing or by a change in shrinkage. Insufficient curing can be rectified by optimizing tool temperature, and shrinkage change can be corrected by checking throughout the tool for consistency in temperature.


To avoid all these problems, it’s advisable to delegate silicone injection molding to experts who will ensure that nothing goes wrong and that your finished products are perfect. Experts are always one step ahead of any possible problem and you have no reason to worry. If you’d like expert advice on your next silicone injection project, call 1.888.202.2052 or email


You might also like:

Another article we’ve written about the process of do-it-yourself injection molding, or this one titled “How much does it cost to make a custom silicone mold?

Jason Vander Griendt

Jason Vander Griendt is a Mechanical Engineering Technician with years of experience working at major companies such as SNC Lavalin Inc, Hatch Ltd. Siemens and Gerdau Ameristeel. He is the CEO of JCAD – Inc., a company he started in 2006 after seeing a gap in the market for businesses who could assist clients through the entire product design and manufacturing process.

Jason has been featured in Forbes, has had his businesses analyzed and discussed in multiple start-up books, was a previous winner of the Notable8 Digital Innovator of the year award, and is a regular guest on business panels and podcasts. Email Jason at or follow him on LinkedIn.

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