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It's the end of the line for End-Of Line Testing

By Joe Ventimiglio, Sciemetric

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End-of-line tests remain popular with many manufacturers, despite their high level of complexity. They can be effective as a final quality check but are not efficient if used as the only quality check. Waiting until after a part is fully assembled to see if it was done right ends up costing more. We should remember that catching bad parts is not the end goal. The focus should be on how to optimize manufacturing so that first time yield rates are as high as they can be and scrap and rework costs as low as possible. Relying only on end-of-line tests will not do that.

The sooner you catch a defect, the less it costs

Every manufacturing operation adds value to the part. Waiting until the end of the line to check whether these operations were done properly means wasted cycle time and materials if there are defects. Also take into consideration that rework of fully assembled parts takes more effort than correcting the flaw right away, at the point where it was introduced.

If you do find a problem at end-of-line, how do you figure out what caused it?

More challenging is being able to effectively manage the line. End-of-line testing will tell you an assembly doesn’t meet the accepted standard. It takes a lot of work to find out why and then even more to determine how it happened, whether it happened before or if it could happen again. Making adjustments to the operations across the manufacturing line requires a little guesswork, which can introduce other issues.

In-process Test as an alternative

In-process testing (or IPT) is about adding process monitoring at every station on the line that is critical to quality. More than providing pass/fail views on the operations, these monitors collect and store all data, including signatures if using a Sciemetric system, to be used for analysis and reporting. So bad parts are taken out of the stream when they occur and if a problem is discovered downstream, the data is there to figure out what caused it and how to avoid it in the future.

IPT is not just about taking a few minor measurements along the line; to provide the real value that allows you to tweak processes you need the meaty data, the information that goes beyond pass/fail or two-point measurement.


Does it work? Ask Ford.

Ford leads the pack in terms of engine quality. The chart shows initial quality satisfaction rates (our analysis based on JD Power data) and Ford has the fewest number of issues. The best part is how the quality continues to improve year over year. It takes vision and commitment to apply IPT to get this kind of result.



  Last words on end of line

The use of IPT versus end-of-line tests depends upon your goals and what you’re trying to achieve on your production line. Sciemetric makes end-of-line testers as well as provides IPT solutions so either way I have product to sell. But if you want visibility and ability to intelligently respond to issues on the line, then you should look into IPT. Relying on end-of-line is bad for your bottom line.



For more information contact Joe Ventimiglio, Director of sales, automotive/industrial at Sciemetric. He can be reached at