The customer was notified that a safety component on a fuser was failing in the field prematurely.  A number of things were discovered during the subsequent investigation. First, the test fixture was relocated to another facility, without the customer’s knowledge or approval.

Thermosistor Test Fixture

As the investigation continued, it was found that the current test fixture was inadequate to find defective parts. Also, only 1 part could be tested at a time. When an MSA was performed, the P-value was found to be significant and the equipment resolution was 4.2 (should be > 10), meaning the test fixture was not repeatable nor reproducible (high variation).

More importantly, the test fixture was unsafe for the operator to use since it had an exposed bus bar carrying high voltage and current. As a result of the findings, it was concluded that a new test fixture was required to improve the safety and productivity of the operation.


The new test fixture needed to be safe and easy to operate, have the ability to retrieve and store data, test multiple parts at one time, reduce variation between the parts, and have a test fixture with a test resolution greater than 10 (all variation is part to part).


The resulting fixture was safe and easy to operate and had a data acquisition system. The new test fixture was able to test 4 parts at one time with temperature adjustment via a PLC. The fixture was qualified using measurement systems analysis (MSA). The data from each slot was tested as well as the entire system. The variation in measurement was significantly reduced (P-value > 0.1) yielding repeatable and reproducible results. All variation was part to part (99.4%), meaning there were no interactions between the parts, equipment, or operator. The system resolution was 14.3. The test fixture was deployed at the supplier. The part throughput increased to where there were no issues with delivery and no defective parts were found in the field.



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