posted 06 June 2000 11:14 AM               

1)This company makes wood, plastic and metal core box patterns that are used to produce crankshafts or cylinder heads at the Ford foundries. We make anywhere from 2 to 6 at a time following Fordâs specific instructions (usually taken over the phone). All dimensions are checked to ensure they get what they asked for but no final dimensions are actually recorded anywhere. Plus they are always exact because if they arenât, the Pattern Maker keeps working on it until it is correct. Question: What can I do to calculate CpK and PpK ?

2)Machine slides. We produce 2 to 6 at a time (total of 10 to 30 per month). All slides have a ãprint specä to which we final audit for flatness, parallelism, surface fit, etc. We donât have ãbatchesä or enough volume to obtain samples in order to calculate CpK and PpK . We do keep all final audit reports that state the USL/LSL and measured values. Question: Is there a way to use these measurements to come up with a valid CpK and PpK ?

3)Automated Machines. These projects take from 3 to 8 months. Usually they are not full turn-key (missing the controls so wonât run). Question: How does one calculate CpK and PpK for this type of manufacturing? We canât even do the Machine Qualification Runoff Testing (another requirement of TE) because controls are not in place and the customer does not require or want it done.

posted 08 June 2000 01:09 PM               

First, reference the introduction ãimplementationä section·.ähowever it is recognized that not all of these requirements are applicable to every organizationä ö unfortunately they use 4.4 ö Design ö as the example which is fairly obvious in regards to applicability. Having said that Îcontinuous improvementä is obviously applicable, but how you go about accomplishing it may or may not involve Cpk/Ppk.

Since you mentioned facilitating continuous improvement efforts, Iâm assuming you are referring to 4.2.5, and page 19 of QS, which says if you have variables data, that you need to optimize characteristics and parameters toward a target value. Your process should first be identified as ãstableä ö hence, SPC would apply. In the first 2 scenarios, short run SPC would seem to make sense ö reference T/E supplement, page 14. Since you mention that the pattern maker works until the parts are exact, Iâm not sure you even have an SPC application in the first scenario, but I would start writing down the data, and look for other CI possibilities ö like first time quality, delivery timeliness, I am not personally familiar with any ãcustom workä scenario which would allow for SPC and Cpk to be used ö but am willing to learn if anyone else is.

The Phase 1,2,and 3 process performance referred to in the T/E supplement would be regarding the product produced with the tooling. It doesnât appear that you have the capabilities to do this. Anyway, once stability is proved, use data from your shortrun SPC charts for the process capability. Make sure you note process changes.

In the 3rd case, the Machine qualification section would apply. Since the machines are missing the controls, I would ask if you run parts manually? The SPC/CPk, PPk, would apply to the product produced by the machines. I worked with a T/E client that in some cases was just material handling equipment, no product was produced. Their qualification was the 50/20 dry run and MTBF, MTTR data. Without controls, Iâm wondering how you verify your equipment can produce parts within specification today. Bottom line is the table on page 6 of T/E says, ãAs required by the customer.ä Also take a close look at the ãintentä stated in the bullets on page 6 of the T/E supplement. BTW ö when do controls get installed? At the customer?

Finally, note that section 4.2 ö Maintaining Process Control, in the T/E supplement refers to high volume tooling ö if you are not required to ãmaintain process controlä would imply that you shouldnât be required to use Cpk analysis ongoing for continuous improvement either.
As stated on page 18 of QS ö the continuous improvement philosophy shall be deployed throughout the organization. They couldnât eliminate the product Cpk/PPk aspect for the T/E supplement because you do have high volume machine tool suppliers that this section could apply to.

With my training and experience to date, thatâs the best I can do, and Iâm open for discussion. Would love to hear from others that have been registered to T/E or the T/E registrars out there.