Before the FIRE starts – Control Plan with additional referenced parameter lists

  • What is the revision date of this CP? – I asked the process engineer when I was performing a VDA 6.3 process audit at an automotive supplier.
  • Almost one year ago – the engineer replied and showed me the revision date of the document.
  • Was there any change in the process in the meantime? – I asked him again.
  • Nope – he replied immediately.
  • How about this machine parameter list? Which version is this? – I turned to him again.
  • Last update happened one week ago – the engineer said and proudly showed the revision list of the parameter list.

Finally it turns out that there were some changes in the process, but the CP has not been revised as “only” the referenced documents were updated. “Certainly” there was no change management activity, customer was not involved and by the way, the currently set parameters were not aligned with the defined parameters.

Typical solution at the automotive suppliers that there is a nice CP, several pages, contains mainly only product characteristics.

If someone takes a closer look, it is very difficult to find any process parameters in the document, but there are some reference documents linked to some machines, which are called as parameter lists.

These describes list of process parameters which need to be set to achieve the desired result: the product characteristics.

  • Is it the right thing to do?

From auditor point of view, I can not state that this is against the described requirements within the APQP/CP booklet or against any of the customer requirements as long as these referenced documents are part of the documentation system and protected and handled properly.

  • So why would this cause any issue?

Based on my experience, this is a method or the cause for the organizations to hide or make (without even recognizing) process parameter changes.

  • Oh, that is not always bad… Customer will not ask unpleasant questions, will not request unwanted documentations, samplings… who could wish more?

Not really:

  • It encourages line technicians, maintenance guys, process engineers to change process parameters without proper risk analysis whenever there is some problem in the process or with the products. Instead of proper root cause analysis, the process might be changed to the NOK parts.
    • The CP revision history will not even include such changes as only referenced documents has been revised.
    • Unauthorized process change could lead to escalation at the customer.
    • Great risk for customer quality claim, impact on lifetime.
  • Why is it a problem of changing some process parameters when the significant characteristics of the parts are checked anyway 100%? We are sure that the parts fulfill its dimension specification.

I was faced several times with similar questions in the past.

The reason is that the process parameters have been verified and approved by the organization and by the customer within the PPAP activity.

It has been stated and proved that the described controls (process and product characteristics) are appropriate to produce parts which meet the customer requirements.

If any of these parameters are changed (out of the specified range), risk analysis regarding the impact of the change needs to be performed according to the customer requirements.

Within change management process, supplier needs to demonstrate that the modified process will also produce OK parts, customer notification or approval might be needed in prior the change is implemented.

I would encourage all quality managers and the quality engineers to review the CPs and verify if the process parameters are listed properly. It is better to list all process parameters directly in the CP.

As always, think in system with Pro Automotive.

If you are interested reading articles about automotive quality management topics, best practices, case studies, follow Pro Automotive.

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