Manufacturing Project

The project whose scope includes delivery through manufacturing will include some quality assurance steps from the previous blog post to ensure we are able to produce the designed product to the quality expected by the sponsor.

Trial Production Run and Problem Discovery

The manufacturing team reviews the development of the manufacturing line with the TPR or Trial Production Run.  The TPRs happen before the run at rate or PPAP reviews, and is a mechanism for preparing the line for these two events. The team uses these trial runs to identify problems in the production line undiscovered during design.  The team gathers data from the exercising of the line to adjust the line.

Trial Production Run

During the TPR, there are reviews of the tools and equipment created for the line and those that are still in progress. The review will also include the work instructions for the line. The quality assurance engineer leads these reviews, but inclusion of key development staff is also appropriate.  We have even seen key development personnel and the customer (OEM) quality assurance personnel, also participate in these events.  These critical, multiple-perspective reviews help ensure the final product from the line will meet quality requirements and customer expectation.  This review is especially beneficial for lines that employ large amounts of manual labor due to the human-oriented quality of the controls (visual inspection). The reviews produce improved work instructions and tools for the assembly process since poor instructions and tools become apparent during the run.

Trial Production Run and First Pass Yield

We will begin measuring the first pass yield for the production line. First pass yield refers to the parts that make it through a station or entire line without rework.  For example, out of the 100 parts built, 97 of them did not require rework. Our first pass yield is then 97%.  First pass yield is a measure of efficiency and accuracy of the line and provides a measure of the suitability of the process.

What to do with Trial Production Run Parts

What do we do with parts from our TPR? We have a couple of options. Some of these parts may become late stage prototype parts for the OEM for trials and evaluation.  Ultimately, some of these TPR parts become parts for product verification testing (PVT).  Often the PVT is the same test regimen as the design verification (we will not digress in this blog post about this approach).

Trial Production Run Balancing Act

It is critical to consider the number of parts required for both this production run and the subsequent verification activity.  To make any sort of valuable assessment of the production line requires a production of a suitable number of parts.  We also must consider that our early builds via the TPR will not likely produce a first pass yield of 100%. It is possible to build too few and learn nothing and not have enough parts for DVT.  It is also possible to produce too many and have parts that will not be customer prototype nor DVT and will ultimately go to waste.  Additionally, it is not unheard of for the customer to disallow re-worked parts for the PVT activity.