COMPANY SPOTLIGHT
Production Process Control
The challenge of an economical production is the reduction of cycle time to achieve a higher output . Reduced cycle times can only be achieved by increased production speed , coupled with increased temperature or pressure . Changes to these process parameters , will have a direct impact on colour as well as on gloss . Due to the complexity of the production process an objective QC system is needed to guarantee a high quality product at the end .
ABS plaques produced at varying mold temperature
5 4 3 2 1 0 -1
40 ° C 60 ° C 75 ° C 90 ° C ΔL * Δa * Δb *
In order to guarantee consistent colour and gloss a frequent sampling rate is needed depending on total production rate .
Tolerance ΔE *
1,20 0,80 0,40 0,00
1 2 3 4 5 6 7 8 9 10
As some colours might change depending on temperature (= thermochromism ) the measurement should always be performed at temperature of the final product to achieve comparable results .
Thermochromism : A temperature-induced and completely reversible change of the absorption behavior of a material in the visible range .
Overall Harmony
Uniformity and consistency of colour is percieved as high quality . Many finished products consist of multiple components . Most of the time , the components are manufactured by different suppliers and at different locations . But in the end the assembled product should be uniform in colour . Thus , not only the production process needs to be controlled , but also the overall harmony of the finished product . Colour tolerances are dependent on the application and the hue .
Studies have shown that CIE Lab colour space is not uniform .
The above diagram shows the CIELab colour space divided into an infinite number of ellipsoidal micro-spaces . All colours within one ellipse are perceived as the same colour . Reason being , a difference in hue is more obvious than a difference in chroma . Tolerances for hue must be tighter .
Chromatic colours have larger ellipses than achromatic colours . Therefore , larger tolerances can be used . The size and shape of the ellipses are different dependent on the hue . Thus , tolerances need to be defined by colour families . Over the years new colour systems and equations ( ECMC – E94 – E99 – E2000 ) were developed based on visual comparison studies for solid colours to improve the visual correlation .
Visit : https :// www . byk-instruments . com / en / twitter : @ surfaceworldmag FEBRUARY 2021
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