The latest technology in liquid silicone rubber (LSR) injection molding will be on display at Medical Design & Manufacturing Minneapolis next month in a demonstration by Arburg, 2KM, M.R. Mold and Shin-Etsu Silicones of America.
Magnifying glasses will be molded from a new optically clear LIMS material (designated KE-2062-70) from Shin-Etsu. Key surfaces are molded from the material: the textured, embossed handle and bezel, and the diamond polished lens. The differing surface textures give the appearance of a two-component part with the simplicity of a single material, according to Shin-Etsu.
Announced last week, the KE-2062 series of 70 durometer A liquid injection molding silicones (LIMS) are described as optically clear. According to Shin-Etsu, it features a wide operating temperature range and flexibility. The material was designed to meet the increasing thermal requirements for high-brightness LED optical lenses.
Equipment in the demonstration includes a SilcoStar e-Flow, which contrary to the usual drive systems uses two metering pumps that are actuated servo-electrically. 2KM, the developer, cites the rising sales of all-electric molding machines in addition to energy savings and cleanliness as advantages of the technology. New features include better control of the process and improved actuators.
The mixed material pressure is measured and controlled at the connection onto the injection molding press. The control monitors even small fluctuations in screw speed that can lead to pressure condition changes and density inconsistency in the metering process. These changes can cause injection errors, especially in the case of multi-cavity tools.
The entire process will run fully automatic on a110-ton, all-electric Arburg Allrounder horizontal liquid injection molding press. An integrated Arburg Multilift robot will pull the parts out of the cavity. The fully automated mold and robot minimize the ejector pins required in the handling area.
M.R. Mold & Engineering manufactured a four-cavity optical lens mold, mounted onto a Royalloy stainless steel universal base with a one drop cold runner system. The lens cavity is polished to a SPI A1 standard. Ejector pins present the parts to Arburg’s end-of-arm tooling, which separates the runner from the parts.