NDT Applications: Eddy Current Testing Improves Thread Inspection with Automation
A custom eddy current testing (ECT) inspection system engineered by Zetec (Snoqualmie, WA) for automotive hub and spindle manufacturer Delphi Chassis (Troy, MI) has provided a fast and 100% reliable test method for thread inspection so cost-effective that it paid for itself in less than a year.
Inspection times have improved to better than two seconds per part and simultaneous inspection of multiple threaded holes at production line speeds has increased productivity, saving approximately $100,000 per year for each line.
Automation proved the key factor to improving the company's thread inspection. By using the Zetec MIZ-27CT ECT instrument from Uson L.P. (Houston, TX), it was easy to add the thread inspection inline with production.
Delphi had been using thread gages and vision systems for thread inspection, but these were time-consuming and labor intensive, as well as expensive, limited and not fully reliable. They first thought of using ECT to determine thread condition vs. no thread condition, which would have been a simple test for this proven method of nondestructive testing.
But then they raised the bar to include the additional test parameters of partial and damaged threads, oversized and undersized threads, broken tap, no hole, thread width, and depth of thread peak and valley. Zetec engineers proved up to the challenge.
The most critical challenge was centering. Initially the part was positioned over the ECT probe manually, but operator placement slowed the process and caused false rejects due to improper loading, as well as high probe wear due to mishandling.
To remove the hands-on process while ensuring product quality and probe longevity, Zetec's automated ECT solution includes a chamfered nose to optimize centering, a stainless steel sleeve over the ECT coil and a spring-loaded housing that retracts the probe if the threaded hole has a broken tap or no drill hole. The tester's two-way communication to a material handler for precise probe positioning is also critical to prolonged probe life.
So production speeds are up and costs are down, operation is "clean" and thread inspection reliability is assured. Lead Delphi engineer for the project, Bablu Ratnaparkhi, is extremely satisfied that Zetec had provided them with the solution as well as excellent customer service and satisfaction.
- Inspection times have improved to better than two seconds per part.
- Simultaneous inspection of multiple threaded holes at production line speeds has increased productivity, which saves approximately $100,000 per year for each line
- The automated ECT solution uses a chamfered nose to optimize centering, a stainless steel sleeve over the ECT coil and a spring-loaded housing that retracts the probe if the threaded hole has a broken tap or no drill hole.
- The tester's two-way communication to a material handler for precise probe positioning leads to a prolonged probe life.