Need disappearing spray paint

[Ranger Mike]

i have a red light laser measuring device. the application is to scan automobile head light assemblies for contour and size relative to the CAD model. The mounting lugs and plastic on the back of the assembly is easy to measure, the shiny front is a problem in that it scatters laser light and no reading can be obtained. we have spray coated the headlight with water soluble spray and can get great results..but..the cleaning of the powder is going to cause production line problems..
has anyone found a compound that can be applied for 15 to 20 minutes and then will disappear?
we even tried freezing the plastic light assembly over night to scan the frost..heated up too soon..
any ideas??

 

[sophiecentaur]

What about a light dust that could be blown off with an air jet?

 

[varialectio]

What about a thin plastic sheet that can be made to conform to the lens and be lifted off after measurement?

I'm thinking of a frame slightly larger than the assembly with a film, like "cling-film" "Saran wrap" etc, stretched over it (think tambourine). Pattern the film so it can be detected by the laser. Press the frame over the lens so the film follows the contours of the lens face. Lift off afterwards.

 

[sophiecentaur]

What about a volatile liquid, condensed on a chilled surface? It could form a haze of droplets which would evaporate later.

 

[turbo]

Hey, Ranger. Try spraying the lens assembly with a mist of water or water and isopropyl alcohol and see if you can get a decent reading. The water will evaporate, and it will evaporate even quicker with an admixture of alcohol.

 

[berkeman]

i have a red light laser measuring device. the application is to scan automobile head light assemblies for contour and size relative to the CAD model. The mounting lugs and plastic on the back of the assembly is easy to measure, the shiny front is a problem in that it scatters laser light and no reading can be obtained. we have spray coated the headlight with water soluble spray and can get great results..but..the cleaning of the powder is going to cause production line problems..
has anyone found a compound that can be applied for 15 to 20 minutes and then will disappear?
we even tried freezing the plastic light assembly over night to scan the frost..heated up too soon..
any ideas??

Production line problems? You're going to 100% test this on the production line?

I'd suggest a mechanical inspection instead, then. Something like an articulating stick with rotation and translation sensors to be swept over the surface.

 

[Ranger Mike]

Thanks all, for the insight so far..i found a source for spray and peel, used in racing for goggles, tear offs, i am to discuss with the engineer Monday..both the application engineer and i will try the recommended solutions so far..it may come to traditional touch trigger probe measurement to do this..the Manufacturer Engineer for the light assembly added parameters..inspection of rear mounting lugs, and up to 16 data points on the front of the light assembly in under 60 seconds, on the production line, by unskilled employees ( in ohio we don't have workers). one additional parameter is no marking or spray that requires cleaning after inspection.
The laser scanner does a very nice job on the back side and we can incorporate a rotary table which would mean the assembly could be place on the table, rotated and scanned and compared to CAD and it would be great..except that laser light scatters when it hits the head light shinny parts..