Friedrichshafen, Germany — The two main innovations on the booth of Kunststoff Institut Lüdenscheid (KIMW) both offer solutions to remove visible knitlines, phenomena that can be particularly noticeable in high gloss parts.
In the ThermoOpt process, a passive temperature control ceramic thermal barrier layer applied to a mold means less heat is absorbed into the mold metal. As a result, the higher temperature in the mold causes the knit line to practically melt away. Stefan Schmidt, managing director of KIMW said the ThermoOpt coating is 20-25µm thick and that this approach has been conceived for dealing with knitlines on large surface area parts.
KIMW displayed ThermoOpt examples in the form of a Gigaset telephone handset and a remote-control garage door opener housing produced by Mayweg Kunststofftechnik GmbH during the Fakuma 2015 trade show in Friedrichshafen.
The other passive temperature control knitline solution uses partial application of additional heat just in the areas where visible knitlines occur. This is applied using electric heating cartridges form Hotset Heizpatronen und Zubehör GmbH in Lüdenscheid.
In what Hotset calls its Z-System partial dynamic temperature control, developed jointly with KIMW, dynamic heating is applied to relevant points in the mold cavity at a heating rate of up to 60°K per second. This raises the temperature from just over 40°C to just over 50°C within 7 seconds, followed by cooling to 10.5°C.