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11. October 2021

Sigma: Simulation of compression molding processes

Sigma Engineering GmbH has enhanced its Sigmasoft process simulation software. The new version 5.3.1 contains a new module for simulation of compression molding processes of rubber compounds.

25 cavities and 9 preforms in a compression molding process. (Source: Sigma)25 cavities and 9 preforms in a compression molding process. (Source: Sigma)

According to the company, the simulation allows reliable prediction of curing degree and cycle-data. Questions around shape, weight, position and number of preforms can also be investigated. The quality of the molded parts can be optimized while reducing the material consumption, without time-consuming and costly trial-work.

„It sounds easy, but implementation was relatively complex“, explains Sigma CTO Timo Gebauer: „The challenge is, that the cavity, or the room into which we inject, constantly changes during the closing of the mold. At the same time the inserted preforms are already heating up, are plasticizing and deforming. This development would not have passed the finish line without continuous advise and validation through our customers.“

Contrary to thermoplastics, there are only very few standardized elastomer compounds. Therefore, Sigmasoft features the creation of new material laws within the software, based on internal or external measurements and supports users during implementation.

„It’s interesting: with this approach there is practically no remaining difference between transfer and compression molding processes for the simulation. Technically, the injection sprue in the middle platen becomes part of the cavity. In the validation, we therefore also calculated transfer molding tools successfully“, says Gebauer. „We are curious, how the most advanced simulation approach is accepted by the experienced rubber manufacturers for the oldest processes.”

Sigmasoft v5.3.1 not only includes the first possibility to simulate compression molding of elastomers, but offers numerous innovations and improvements, especially in the area of thermoplastics, for example a more precise prediction of warpage and shrinkage. The Autonomous Optimization feature included in the software now also works for two-component parts. Additionally, the material data base was enhanced.


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