Everyday I work with customers to provide them with quotes for their new silicone molded part designs. In the preparation of those quotes I have noticed an interesting trend; many part drawings are coming in with a note that reads, “Part must be free of burrs.” This brings about a common misconception with silicone molded parts and most importantly, their respective part drawings.
Burrs are residual flakes or chips of material that remain once a part has been machined. One thing to keep in mind is that burrs occur on machined parts, not molded parts. Flash on the other hand, occurs on molded parts, whether compression molded, transfer molded or injection molded. Flash can occur in multiple locations on your silicone molded parts including along the parting line, at the gate, and at pin or insert locations. Flash is an unwanted byproduct of the silicone molding process and typically must be removed to allow the silicone part to meet quality requirements. Liquid silicone parts are prone to flash due to the material’s very low viscosity, as compared to other molded materials including rubbers and plastics.
Albright Technologies’ liquid silicone molded parts are deflashed prior to final inspection and shipment to your facility. To minimize flash, we machine a high precision parting line into our customer’s mold tools that is designed to reduce flash and promote effective deflashing. This approach often results in a part that meets flash tolerances within specifications with no need for additional deflashing. Other times, parts will require additional deflashing methods in order to meet the flash tolerance. Albright typically sets it’s flash tolerance at 0.010”, however, we have molded many silicone prototypes and production parts with flash tolerances between 0.005” and 0.003”. We complete a 100% inspection on your silicone molded parts to ensure flash tolerances are met and other part characteristics are compliant. We use the latest metrology measuring equipment to determine part measurements including residual flash.
The next time you are creating a silicone part drawing, keep in mind that you should note “Part must be free of flash in excess of 0.010” (or requirement number that works for your part design), instead of the common “Part must be free of burrs” reference.
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