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18. June 2020

Sigma Engineering: Face mask production with Virtual Molding

Starting in April 2020, Sigma Engineering, Arburg and many other partners joined forces to work on a new project for the production of face masks against the spread of the coronavirus. By now the production of injection molded masks made of LSR (Liquid Silicone Rubber) is running at full speed.

Sigmasoft Virtual Molding will precisely calculate the required number of cycles the mold needs to reach thermal steady state. The fixed (left) and the moving platen (right) at 180 °C after stabilization within ten cycles. (Source: Sigma)

Sigmasoft Virtual Molding will precisely calculate the required number of cycles the mold needs to reach thermal steady state. The fixed (left) and the moving platen (right) at 180 °C after stabilization within ten cycles. (Source: Sigma)

"We noticed a high demand for protective masks from the public as well as from our own employees, which made this project-cooperation highly welcome", says Thomas Klein, Managing Director of Sigma about the current situation. "Due to the successful and focused cooperation with partners such as Arburg and Polar-Form we were able to simulate the layout of the complete LSR mold within shortest time and optimized the mold design for process-efficiency and robustness".

Sigmasoft Virtual Molding was used to determine and optimize injection points, pressure requirements, temperature distribution, air entrapment, and the crosslinking of the LSR material.

"We examined a lot of different factors. But the focus was on component quality, optical properties and, of course, the safety of the user that comes with a perfect component free of air entrapments or other defects. But also, a fast and resource-saving process design was very important to us", says Sonntag about the requirements for the project and part.

Sigmasoft Virtual Molding will precisely calculate the required number of cycles the mold needs to reach thermal steady state. For an exact control of the temperature distribution, the number of temperature sensors in the mold was increased to six and their positions were optimized based on the simulation results. This allowed a focused regulation of the heating cartridges. In addition, an optimal insulation of the mold reduced the required energy to a minimum.

Sigma completed the project within 24 hours, from the mold setup to the filling calculations and the thermal layout. A total of four parts per cycle are injection molded at 180 °C from the non-postcure LSR Elastosil LR 5040 supplied by Wacker. The required symmetrical temperature pattern of the four cavities was first created and optimized in a simulation using optimal insulation, six temperature sensors and regulatable heating cartridges, and then realized by Polar-Form in the mold construction.

www.sigmasoft.de
www.arburg.com
www.wacker.com
www.polar-form.de

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