An inline colour measurement system from Micro-Epsilon is enabling the colour of plastic injection moulded parts to be automatically checked early in the production process, which reduces cycle times and optimises productivity.
As well as measuring parts at high speed in-process, the colorCONTROL ACS7000 colour measurement system from Micro-Epsilon can also inspect the colour of injection-moulded parts as they are extracted from the mould, without having to wait for the parts to cool down. This dramatically reduces cycle times and allows for 100% quality control of colour.
When parts that are supplied from different manufacturers and made from different materials are combined, it is essential that the colour values of these parts are exact. If they are not, quality assurance can become an issue.
In order to provide 100% control of the exact product colour shade during the injection moulding of plastic parts, German company SKZ (Süddeutsche Kunststoff-Zentrum) has developed and tested a method to correlate the difference in colour of an object at different temperatures (thermochromism behaviour).
Even with a temperature difference of just 20°C, colour deviations of more than 2 ΔE units can occur depending on the colour monitored. Colour measurements carried out using the colorCONTROL ACS7000 system and temperature measurements using the infrared thermoMETER CT sensor from Micro-Epsilon, enable a master curve to be generated 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 the actual room temperature colour values.
These pre-calculated ‘cooling curves’ stored in the system software allow the colour values determined during the de-moulding process to be converted into a reference temperature (@20°C). This enables the colour to be automatically checked earlier in the process, which reduces cycle time and optimises productivity and output, compared to conventional sample checks.