Liquid silicone rubber symposium targets emerging advancements

Mike Edwards
May 04, 2011
Written by
Shin-Etsu Silicones of America, Inc. and Arburg, Inc. recently co-hosted their 5th Annual Liquid Silicone Injection Molding Symposium at Arburg’s state-of-the-art Technology Center Midwest in Elgin, IL.
A world class line-up of material and equipment suppliers profiled Innovations in LIMS (Liquid Injection Molding System) technology and products including: molding and process equipment, molds, computer simulation advancements for LIMS part & mold flow, and LSR pumping systems & injection nozzles. Dedicated tracks also addressed multi-component applications for Liquid Silicone Rubber (LSR) – a vital topic in the medical, consumer, and automotive markets. 

Over 100 LSR industry professionals attended the symposium and experienced hands-on equipment displays and presentations from industry leading keynote speakers including: Shin-Etsu Silicones of America, Arburg, Gayson SDI, Kruse Analysis, Roembke Mfg. and Design, and Fluid Automation.

fluidautomation_webEric Bishop, North America marketing manager for Shin-Etsu Silicones of America, Inc. (SESA: A U.S. subsidiary of Shin-Etsu Chemical Co. Ltd., Japan), noted that SESA is broadening the unique palette of properties of its Select-Hesive LIMS KE2090 Series. In addition to the core benefits of eliminating the need for hazardous priming, inconvenient pre-treatments, and costly secondary assembly operations, the series now provides new hardness ranges from 5- to-70, Shore-A. “The goal is to expand the series’ primer-less adhesion benefits to a wider range of applications. We’re seeing an increased demand for softer silicones,” stated Bishop. 

Notably, SESA is also having success utilizing their KE2090 Series with higher temperature thermoplastic resin substrates such as PEEK, PSU, PPSU, and PEI. According to Bishop, “The ability to run the over-mold temperature hotter, allows the silicone to cure faster, which lowers the cycle time – ultimately increasing the productivity of the equipment.” 

Arburg, a manufacturer of injection molding machines for plastics processing, provided an LSR molding demonstration of its Allrounder 470 A (1000-70) running Shin-Etsu’s KEG2000-40 Series material in a 4-cavity baby nipple mold (see video). The economical, high-performance, 110-ton machine is equipped with an integrated 3-axis Arburg Multilift servo-drive robot and a LSR dosing machine from Fluid Automation. The machine is used in industries that require an optimum level of efficiency, even where a high level of performance is expected, such as the medical technology sector and the food, packaging and automotive industries. 

The electric Allrounder 470 A machine features 18.5 in. tie-bar spacing and 3.4 oz maximum injection shot size that offers the flexibility to go as small as 12 mm screw size to optimize efficiency according to shot volume and process requirements. The integrated 3-axis Multilift V robot features an integrated machine control system responsible for controlling the entire robot cell. 
Features for ensuring LSR shot-to-shot repeatability and accuracy include a special check ring assembly for the screw and regulated back pressure control via servo drive with paraxial measurement at the screw and the point of process. 

According to Martin Neff, ARBURG’s U.S. Manager Midwest Sales & Engineering, “The importance of accuracy and repeatability cannot be understated in LSR production. The drive technology of the Allrounder electric machine features a planetary roller screw drive and liquid cooled servo-electric motors. These key elements provide fast, energy efficient, precise, and responsive acceleration/deceleration movements with a short intervention time. This allows for responsive adjustments to process accuracy for the LSR material viscosity and consequently shot-to-shot consistency while reducing cycle time.” 


A designer and builder of inserted flashless rubber molds, Roembke Mfg. & Design president Greg Roembke offered insights into developments in LSR flashless tooling and internal cavity mold pressure sensors which can measure imperfections and correct them during each shot – essentially allowing molders to achieve a window into what's happening inside the mold with each process.

Notably, Roembke focused its attention to a new 2-shot (rubber/plastic) technology system it is spearheading in the North American market. The key to the technology vs. the transfer method is that one machine gets the entire product out in molding plastic and LSR together – thus, eliminating an entire step in the molding process. Since it’s a 2-shot system, the warm LSR will adhere to warm plastics better. The 2-shot system could use a Shin-Etsu self-bonding material to adhere the silicone to the plastic substrate. Additionally, internal mold pressure sensors can be incorporated which allows complete control of the valve gates including: balance of the cold runner, monitoring the internal cavity material, and its temperature and/or pressure. 

Gayson Silicone Dispersions, Inc. (GSDI), is a provider of pigment, chemical additive, and catalyst dispersions for HCR/LSR/RTV applications since 1979. Whereas color is a hot trend in multiple market LSR applications for product identification, corporate product branding, and overall aesthetics, it is often considered late in the LIMS production process which can lead to unwanted and costly problems. 

According to GSDI Sales Manager Tom Manello, “Troubleshooting color considerations as early as possible in the design engineering and production tool building phase is the key to avoiding color issues when a part goes into production.” 

At forefront of developing and building state-of-the-art dispensing equipment for RTV and LSR materials since 1974, Fluid Automation, Inc.’s VP of Sales, Bob Pelletier discussed the continuing demand for advanced verifiable ratio control in LSR. According to Pelletier, “It’s vital to educate customers on the checks and balances for LSR such as pressure fluctuations and how they affect the process, water cooling and the temperature of material and thermal expansion properties.” 

kruseanalysis_webWith an eye on the present and future potential of silicone technology, Torsten Kruse, owner of Kruse Analysis, Inc., presented his company’s innovative CAE (computer aided engineering) injection molding simulation services which are being adopted in the early phases of LIMS mold-making to determine thermal behaviors in steel molds prior to building. Kruse noted that while the technology has been prevalently used in plastics injection molding, the LSR industry is just beginning to embrace true 3-D LIMS simulations to maximize mold designs. 

This article was provided by Shin-Etsu Silicones.

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