Thermal Imaging Camera Finds Robotic Weld Gun Problems

by James Coorough
General Motors Corporation
In March of 2001 a GM production foreman asked J & R Thermography to find the source of a foul burning rubber odor. Upon scanning the area with a thermal imaging camera, the team discovered a 500 MCM air cooled ribbon (ribbon 1) that was dangerously overheated. Figure 1 shows the original thermal imaging scan of the area showing a temperature of 208 degrees C on ribbon 1. The rubber sheath on these cables was pretty loose, so true temperature readings of the actual cable were impossible while using our thermal imaging camera. When operating normally, the thermal imaging camera found that this ribbon has a temperature of 30-50 degrees C.  Ribbon 1 was replaced at the next down time.
   
Figure 1: Air cooled ribbon (ribbon 1) on the weld gun is severely overheated. Normal operation for this ribbon is 49 degrees C. Further investigation with our thermal imaging camera shows somewhat higher temps on the other ribbon (ribbon 2) also.
The thermal imaging photos in Figure 2 show the breakdown of ribbon 1 due to heat. Micro-ohmmeter measurements of the cable read 140 micro-ohms, roughly three times that of a new cable.
   
Figure 2: Photos are of ribbon 1 after removal from weld gun. Photo 1 shows rubber sheath burned off in areas. Photo 2 shows internal deterioration of the cable.
Further investigation with my thermal imaging camera shows somewhat higher temps on the other ribbon (ribbon 2) as well. An inspection with a thermal imaging camera after the first ribbons’ replacement (Figure 3) showed normal operating temperatures on ribbon 1. Ribbon 2 also showed a decrease of 30 degrees C after repair but is still slightly higher than normal. The decrease in temperature may be due to less conduction from ribbon 1, and also less compensation for the breakdown of ribbon 1. Low emmisivity made reflection a non-issue. It was advised that ribbon 2 be inspected every day with our thermal imaging camera and replaced when temperatures consistently reached 95 degrees C. Further inspections with our thermal imaging camera may reveal the need to replace the air cooled ribbons with water cooled ones.
   
Figure 3: The thermal imaging scan in Ribbon 2 shows somewhat higher than normal temperatures.
A follow up inspection with a thermal imaging camera determined a time savings of approximately 30 minutes for the problems found. With production downtime costing about $5,000 per minute, our thermal imaging camera helped in savings of about $150,000. Ribbon 2 lasted approximately 30 more production days before being replaced.

For more information on thermal imaging cameras, please visit http://www.flirthermography.com/cameras/all_cameras.asp.

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