Molded rubber parts typically require finishing to remove small or thin bits of excess rubber (flash) which remain after the rubber is cured into the desired shape. Flash was traditionally trimmed, part-by-part, by hand, and later by machine; however, the cryogenic rubber deflashing process offers a very efficient method of removing flash for high volumes.
The molding process leaves its mark on rubber parts in the form of small strips, flaps, or other evidence of where the rubber entered the mold, where the parts of the mold meet, and where pins and slides are located inside the mold. These tiny remnants or flash need to be removed in a way that doesn’t compromise the shape, size, or surface of the rubber part. Cryogenic deflashing can accomplish this quite efficiently, for both outside surfaces and recessed or hollow areas.
The process involves cooling molded rubber parts with a cryogenic substance — typically liquid nitrogen — to embrittle the excess material, making it easy to break off. The parts are often tumbled with the addition of a tumbling media, such as tiny plastic pellets. Parts are frozen just long enough for the thinner flash to become brittle, so it comes off easily, without affecting the integrity of the part itself. Cryogenically deflashed parts retain their shape, size, and surface finish.
Cryogenic deflashing should be customized to meet the characteristics and finishing needs of the molded rubber parts being treated. Multiple factors work together to create the most efficient and effective method, namely:
The time variable includes the entire process, from chilling parts, transferring them to the deflashing basket, tumbling the parts, and removing them after finishing. Cycle times are low and can vary from a few minutes to half an hour.
Part size, structure, and the amount of flash to be removed help determine an appropriate temperature to which parts should be chilled, generally between 0°F and -180°F (-18°C to -118°C).
Most cryogenic deflashing processes use a tumbling media which is directed at the parts for improved efficiency and better results.
Dust-free, non-toxic, small polycarbonate pellets are most commonly used for cryogenic deflashing, normally sized between 0.015” and 0.060” (0.15 mm to 2.03 mm).
This parameter indicates the speed at which the tumbler rotates the parts and media, with faster speeds used to remove more extensive amounts of flashing. Tumble speeds range between 5 and 40 RPM.
The arrival of cryogenic deflashing has been a game-changer in the rubber molding industry, bringing dramatic improvements over manual deflashing in efficiency, quality, and consistency. Advantages of the cryogenic process include:
Cryogenic deflashing naturally lends itself to removing flash and deburring a wide variety of parts, including those with recesses, hollow areas, or other complex geometries that are more time-consuming to deflash with other methods, including:
At RD Rubber Technology, cryogenic deflashing is just one of the innovative solutions we offer to improve quality and efficiency so we can continue our commitment to the highest level of customer satisfaction. Contact us today to learn more about our industry-leading rubber molding and manufacturing capabilities.