Interior trim colour quality inspection

Need

A grained trim surface gives glare and micro-shadows under directional light, so the same part measures lighter or darker depending on the light angle. Yet a small shade difference between parts sitting side by side in the cabin is spotted by eye at once; ambient light shifts the measurement too.

Solution approach

A dome light wraps the part in even, diffuse light from all sides and shuts out ambient light, suppressing the shadows and glare of the grain. The camera looks straight down through the hole at the top of the dome. Colour is taken as an area average in three regions, converted to L*a*b* and compared with the master sample recorded under the same dome; the difference is given as one number, ΔE.

Process steps

1. 01

   Index

   The rotary table indexes one step; the next part arrives at the measuring station.

2. 02

   Measure

   The dome light strobes; colour is sampled at three regions on the grained surface.

3. 03

   Compare

   The mean L*a*b* value is compared with the master sample and ΔE is calculated.

4. 04

   Decide

   ΔE is compared with the tolerance limit; the result is recorded with the part.