Leading retail earplug manufacturer McKeon Products, Inc. (Warren, MI) is a company originated by earplug innovation - having invented the silicone earplug upon its inception in 1962. With a full range of moldable and pre-molded silicone earplugs for a variety of swimmers ear and hearing protection uses, the company recently embarked on progressing its advanced earplug line. McKeon President/CEO Devin Benner commissioned technically advanced, multinational liquid-silicone parts molder Silcotech North America Inc. (Bolton, ON) to lead the engineered production and product performance manufacturing challenges.

The key production issue stemmed from the fact that the product had a thin wall section which needed higher tear strength as the de-molding process generated high levels of scrap due to tearing. After prototyping five different molds, an automatic 16-cavity slide tool was chosen with thin wall sections for sealing flanges and thick wall sections for handle areas (small: .25 mil / thick: 5.0 mil).

Ultimately, the parts’ geometry and cavity had significant undercuts√¢‚Ǩ”therefore, the loads on the material were high in part removal with parts breaking and remaining in the cavity which hindered the overall cycle time. Silicone plating out on surfaces required the tool to be removed from the press for cleaning every two weeks for 6-8 hours - plus, the tool had to cool down & heat up as well.

Faced with the expensive option (US$70-100K) of again redesigning the tool to eliminate the undercut, Silcotech opted to seek out a superior material that had the sufficient mechanical strength properties to handle the part.

Recognizing the need to reduce cycle time, Silcotech NA President Michael Maloney contacted Shin-Etsu Silicones of America, Inc. to test its new KE2004-20 silicone LIMS product which was stated to have the highest tear strength on the market for a 20 durometer product. In addition to their low hardness and high tear strength, KE2004-20’s relatively higher viscosity also translated to improved handling and flash. Its higher strength and outstanding release properties allowed for de-molding parts√¢‚Ǩ” particularly those with thin wall thicknesses√¢‚Ǩ”without tearing and generating scrap.

Shin-Etsu promptly sent Silcotech sample test pails to run with the tool and 3-4 tests were conducted. According to Maloney, “In the final analysis, we needed a higher tear strength material and Shin-Etsu’s KE2004-20 reduced our cycle time by more than one-half (60%)...it was a night and day difference.”

KE2004-20 Series performance benefits in the earplug manufacturing process included:
• Reduced the number of scrap parts during de-molding while maintaining the same soft feel
• Cycle time required reduced by 60%
• Less plating-out of silicone required less frequent cleaning
• No change in processing parameters√¢‚Ǩ”easy transition to new material.
• Higher productivity/higher yield√¢‚Ǩ”100% increase in productivity
• New market opportunities due to greater manufacturing efficiency.

According to Eric Bishop, North American Marketing Manager for Shin-Etsu, “The application called for a material with the optimal combination of soft feel and high tear strength to meet the demanding functional and processing requirements. Our KE2004-20 provides the highest tear strength of any 20 durometer LIMS product on the market today."

A U.S. subsidiary of Shin-Etsu Chemical Co. Ltd., Japan, Shin-Etsu Silicones of America, Inc. is a major supplier of silicone materials to North America's medical, automotive, electronics, aerospace, and manufacturing industries. Shin-Etsu’s premium silicone compounds incorporate leading-edge technology, staff expertise, and value-added service; offering customers the highest levels of quality and consistency in specialty silicone materials.
www.shinetsusilicones.com