Why Liquid Silicone Rubber (LSR) Injection Molding Stands Out as the Top Choice
In the dynamic realm of manufacturing, the injection molding of Liquid Silicone Rubber (LSR) has emerged as a game-changer over the past two decades. Thanks to its unique properties and advanced processes, LSR injection molding has firmly established itself as the preferred option for creating high-quality parts.
The Distinctive Attributes of LSR Injection Molding
The thermosetting nature of LSR sets it apart, demanding specialized handling during the injection molding process. Uniform distributive mixing is crucial, and maintaining a consistent temperature until the material is injected into the heated cavity for vulcanization is non-negotiable.
LSR is typically supplied in drums or pail kits. Its low viscosity allows for seamless pumping through hoses and pipes to the injection equipment. Comprising two separate components (designated as component A and B), these components are precisely metered and pumped through a static mixer. One component contains the platinum-based catalyst, and coloring pastes or other additives can be incorporated before entering the mixer. Inside the static mixer, the components are thoroughly blended and then transferred to the cooled metering section of the injection molding machine.
The static mixer plays a pivotal role in ensuring a homogeneous blend of component A, component B, and any pigment (if required). This meticulous mixing process guarantees consistent material dosage and initiates the vulcanization process mere moments before raw material injection. Compared to High Consistency Rubber (HCR), LSR’s injection molding process offers unparalleled accuracy. HCR materials, usually pre-mixed and partially vulcanized compounds, are processed in higher cavity press molds via transfer molding. This approach results in less material consistency and control, leading to greater part variability, even within the same batch. Moreover, HCR materials require higher processing temperatures and longer vulcanization times, making them less energy-efficient and more environmentally impactful.
One of the significant advantages of LSR injection molding is the cold runner technology. By cooling the material, manufacturers can produce LSR parts with minimal material waste, eliminating the need for trimming operations. This not only cuts down on material costs but also ensures the production of flash-free parts, provided that high-precision, quality tools are utilized.
LSR: The Ideal Material for Advanced Molding Techniques
LSR’s exceptional adhesion to plastics and metals makes it the perfect choice for two-shot and over-molding technologies, also known as multi-shot or assembly injection molding. Two-shot injection molding of LSR enables the combination of two materials—one with a cold runner and the other with a hot runner—within the same injection mold. This innovative process streamlines production, saving costly assembly steps while integrating multiple functional features into a single, finished part. It ensures consistency across components, guaranteeing that each part exhibits the same high level of performance and required characteristics.
At SHENGHUI Silicone Parts, a renowned leader in manufacturing high-precision parts and components, our expertise lies in the production of LSR and LSR/Thermoplastic (Two-Shot) components. We are committed to delivering top-notch quality and leveraging the latest advancements in LSR injection molding technology.
References
[1] Osswald, T. A.; Baur, E.; Brinkmann, S.; Oberbach, K.; Schmachtenberg, E.: International Plastics Handbook; 4th edition, Hanser Gardner Pubilcations, Cincinatti, 2006
[2] White, J.; De, S.K.; Naskar, K.: Rubber Technologist’s Handbook – volume 2; Smithers Rapra Technology, Shawbury, 2009
[3] Schmachtenberg, E.; Johannaber, F.: Montagespritzgießen – Verfahrensprinzipien und Definition; Technical Conference Montagespritzgießen, Institute of Polymer Technology, Erlangen, Germany, Nov. 2007, p. 1-18
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