In-Mould Paint Thickness Control

Marauder · Feb 3, 2003

I am working on improving application of in-mould paint with a PU system. Current method is using manual spray gun, but it is inconsistent and operator-dependent.

The method I had in moind was to use multiple nozzles to spray around the mould and (hopefully) obtain consistent even coverage.

1. Any suggestions of a nozzle that would do that? I imagine it would have to spray an ellipse pattern per nozzle, so a group of nozzles would provide for the required shape.

2. Any better ideas? Robots are out due to cost...

3. Related to the same issue, I have much difficulty measuring the thickness of the paint on PU. I attempted an ultrasonic gauge, but the readings were inconsistent on the same spot. To complicate matters, I believe the paint reacts to the PU so there is no real distinct boundary. Any suggestions?

Thanks!

kenvlach · Feb 3, 2003

Ultrasonic is poor for measuring thin coatings.
If you use metal molds, an accurate way to measure the DFT of the paint is by eddy current device. Most are handheld devices with a small probe on the end of a cable, so easy to measure on any ~flat surface (3/8" is fine, some can do on 1/4" flats). In aluminum anodizing, routinely measure to about 0.01 mil (0.25 micron). If your molds are steel, you can also use magnetic type instruments.
Some suppliers are Fischer & UPA.

http://www.fischer-technology.com/

http://www.upa.com/home.html

For measuring wet paint thickness (& other things), see

http://www.gardco.com/

What is PU? If you mean polyurethane, then only the wet film testers mentioned will work.

Marauder · Feb 4, 2003

thanks for the feedback kenvlach.

you're right - by pu i meant polyurethane.

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