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If you have ever wished for a quantitative measure of ease of part release, here’s a new technique that can help you choose an optimal mold finish or coating for fast and reliable automatic injection mold cycles. It was featured at this spring’s annual Technology Days expo hosted by ARBURG, Inc. at its Lossburg, Germany, headquarters (see May Close Up). , a venture of Kunststoff Institut Ludenscheid in Germany, showed off a four-year development effort to develop a method to measure release force.

As explained by KIMW managing director Frank Mumme, KIMW has developed a test apparatus with disc-shaped inserts that replicate the mold surface. Any desired coating can be applied to the insert. The test mold produces a disk of 35-mm diam. and 2-mm thick. The disk has a series of raised “teeth” arranged radially around the sprue on the back side. These teeth engage with a mechanism that rotates the disc and senses the force required to cause the disc to first start to turn against the cavity insert. That force serves as a proxy for the force required to release the part. If the user wants to simulate a situation in which the part has shrunk onto a core, a controlled force is applied to press the part against the cavity before the rotational force is applied. KIMW began by investigating release of soft TPEs but is now testing hard thermoplastics.