PPM Defectives is abbreviated as PPM and is part of the language of Six Sigma. It is often used in all sorts of computations, but here at Press-Seal is used as one of our measures of quality.
PPM Defectives is easiest to understand when you compare it to a golf score – you simply want the lowest number possible. It refers to the expected number of parts out of one million that you can expect to be defective.
It has been a very common measurement within the automotive industry for many years and has been used by many of these customers to measure the quality performance of a supplier.
So what is the calculation?
You can calculate PPM Defective by simply dividing the number of defective parts by the total number of parts you ship and multiply that by 1-million.
Defective / Total * 1,000,000 = PPM Defective
What Do You Mean By Defective?
Defective should not be considered the same as defects. A defect is something beyond what the customer was expecting to receive. A product could possibly still be sold to a customer with a defect, even though they may not be entirely happy with the end result.
An example in our industry might be the labeling on a concrete pipe gasket. It may not meet the customer’s expectations, but it still can be sold to them and used in the field but not affect performance.
Whereas a defective part is a product that cannot be sold to a customer and is turned into scrap.
An example of this might be a concrete pipe gasket that has a bad splice. The product is unable to be used in the required application, therefore it is a defective part.
And yes, we readily admit we can have defective parts and that’s part of the reason we monitor our PPM. To control our quality and have definitive data pointing to a possible manufacturing process that needs modifying or revised.
What Is Your PPM?
We have been tracking our PPM for 5-years now and the number continues to drop annually. Remember, we want the lowest score possible.
At one time our PPM was nearly 900 and in 2017 we broke an all-time record with a PPM below 100.
So how does this help you? In our next article we’re going to explain how a quality measurement like this can benefit you as a customer and how defective parts could affect an entire storm water or sanitary system.