3/30/2011 | 1 MINUTE READ

Checking Part Changes During Temp Testing

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One of the more annoying causes of squeaks and rattles in a vehicle has a lot to do with climactic conditions.

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One of the more annoying causes of squeaks and rattles in a vehicle has a lot to do with climactic conditions. Say a customer gets a new car in Detroit during one of the transitional weather periods (about half the year). One day it is 50° F. The next day it is 20°. Then up to 40°. And so on. Or say you’re in Phoenix one day, then up in the mountains the next—again, rapid temperature changes. And then there is a rattle in the instrument panel (IP).

Due to this thermal cycling, the plastics in the IP can grow and shrink. According to Jim Arnone of Dynamic Intelligent Solutions (DIS; dynamic3dmeasure.com), the typical approach in developing an IP is to measure it with a coordinate measuring machine (CMM), putting it into a chamber where it is exposed to temperature and humidity for a period of time, then removing it and checking it with a CMM, to see what changes have occurred.

So you have the before and after. But what about the during?

And isn’t it possible—if not likely—that because the IP is an assembly of different-sized parts and made of different materials that there will be some local size-changes that are the root cause of other changes?

DIS has developed a system that utilizes photogrammetry, digital cameras that are in specially designed environmental housings, data acquisition software and hardware, that can be used within environmental chambers (from -77°C to +177°C and relative humidity up to 95%) to obtain data about what happens to the object under study (e.g., an IP) during the tests. Data is obtained 15 times per second, and offers an accuracy of 35 to 45 microns. The software can output the information regarding part changes in a variety of formats.—GSV

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