However, the colorCONTROL ACS7000 inline colour measurement system from Micro-Epsilon can inspect the colour of the injection-moulded parts as they are extracted from the mould and not just after cooling down. The described method saves time and allows for a 100% colour quality control.
As soon as parts from different manufacturers made from different materials are combined into assemblies, the safe adherence of required colour values becomes an essential quality assurance issue. In order to provide a 100 per cent control of the exact product colour shade during the plastics injection moulding, the SKZ (Süddeutsche Kunststoff-Zentrum) has developed and tested a method as part of a study for different surfaces. The system uses an empirically determined correlation of the colour between warm and cold pieces (thermochromism behaviour). Even with a temperature difference of just 20°C, colour deviations of more than 2 ΔE units can occur depending on the colouring. Colour measurements carried out with colorCONTROL ACS7000 and temperature measurements using the infrared thermoMETER CT sensor generate a master curve at several different temperature levels that describes the thermochromic behaviour of the coloured polymer.This allows colour values determined on a warm component to be converted to room temperature.
The cooling curves pre-determined and stored in the software allow the colour values determined during the de-moulding process to be converted into a reference temperature (20°C). The colour is now automatically checked earlier in the process, which optimises productivity and output compared to conventional sample checks.