Earplug manufacturer McKeon Products Inc., Warren, Mich., commissioned liquid-silicone parts molder Silcotech North America Inc., Bolton, Ontario, to spearhead production and engineer an advanced earplug line.

KE2004-20 silicones from Shin Etsu Silicones of America are used in the manufacture of earplugs for swimming and hearing protection.

The company ran into issues because the product has 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).

The part's geometry and cavity had significant undercuts—therefore, the loads on the material were high during 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 and heat up as well.

An earplug manufacturer faced a production issue because the parts have a thin wall section which needs high tear strength. In previous versions, the de-molding process generated high levels of scrap due to tearing.

Faced with the expensive option of redesigning the tool to eliminate the undercut, Silcotech opted to use a different material with sufficient mechanical strength properties. Silcotech president Michael Maloney contacted Shin-Etsu Silicones of America Inc. to test its KE2004-20 silicone LIMS product. In addition to its 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— particularly those with thin wall thicknesses—without tearing and generating scrap.

Shin-Etsu promptly sent sample test pails to run with the tool and 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 half. It was a night and day difference.”

Liquid injection-molded silicones from Shin Etsu reduced the spill out of material onto the molding machines, resulting in less scrap and less downtime.