What shrinkage value should be used when designing a silicone mold?

Question: What shrinkage value should be used when designing a silicone mold?

Answer: Shrinkage is defined as “the amount or proportion by which something shrinks” (http://www.thefreedictionary.com/shrinkage). A material’s shrinkage must be accounted for when designing a mold to produce a silicone part that meets all required dimensions. Silicone normally can shrink from 1% to 4%. The shrinkage analysis is sometimes not provided when we buy silicone from manufacturers. Based on my personal opinion, 2% can usually be used for a standard shrinkage value when designing a silicone mold. Nevertheless, variation between material lots can significantly affect the shrinkage percentage as well as the part’s geometry. For example, a long hollow cylinder part that has a thin wall is going to shrink differently on different axes. Specifically, the long section of the part is going to shrink more than other axes. In this case, the part must be scaled differently on different axes.

The suggested shrinkage value will work most of the time. However, in a case where the material’s shrinkage doesn’t meet the standard shrinkage allowance or a part has a similar geometry to the one described above, educated estimation on shrinkage value should be made when designing a silicone mold.

This entry was posted in General Silicone, Silicone Design, Silicone Manufacturing, Silicone Properties on by .

About Hean

Prior to joining Albright Technologies, Hean was an intern and a part-time employee at Berry Plastics. After starting at Albright Technologies in May 2011 as an intern, he recently became a full-time employee as a Project Engineer in Training. Currently his responsibilities include, designing molds, programming codes for tools, inspecting articles, setting up a LIM machine and anything else that helps the team move forward. Hean received his Associates degree in Liberal Arts and a concentration in Physical Science from Middlesex Community College in 2008, and a Bachelors degree in Plastics Engineering with a business minor from UMass Lowell in 2011.

  • leo sze

    Generally speaking, you need to scale up around 3/1000 to compensate the shrinkage. (Good Silicon and PU material)
    But it really depends on what silicon and PU you use.

  • Hunk Han

    Silicone rubber mould is a relatively popular rapid tooling manufacturing process and is widely used in the rapid manufacturing industry due to its good toughness to make prototypes with complicated structure, fine pattern, no mold inclination and even pouring angle. It has the following advantages.

  • Hunk
  • Praveen Dhamanekar

    How much % is the shrinkage allowance for 3mm Silicon rubber sheet