Process Control / Changes

[JRKH]

I am looking at how to control processing thru the shop. Basically what I want to do is this:

1) Control the processes themselves (lathe, mill, punch weld etc)

2) Create job routings that move material/product from process to process.

Thus:

If a process changes i.e new/ better equipment, training etc. the process is reevaluated.

However if we reroute a part from one capable process to another, this would not constitute a process change for this part which would require a new PPAP.

Would this method be acceptable for a QS system?

James

 

[D.Scott]

James - I am looking from outside the box here so I may not completely understand what you are doing. As a QS-9000 company I see it this way.

The PPAP submission was accepted based on the control plan for a specific part and outlines the process steps. If you were to divert the product to a different process stage, even though that stage is capable, it would constitute a "change" in the approved control plan.

You may be able to get more than one combination of processes qualified which would allow you flexibility, but I think that would cause a nightmare in lot control (what was processed where and how).

Hope I haven't misunderstood the question and confused you.

Dave

 

[Marc]

There are a number of threads here dealing with what triggers a re-PPAP. Switching the process step sequence is one of the qualifiers. But - more detail is needed. Maybe a more detailed example.

In addition, remember -- when you do a process change (or a design change, for that matter) a complete PPAP is not always necessary . It depends upon what is happening. You may only have a very small portion of the complete PPAP. Be sure to work closely with your customer SQA. I've found it best to contact the SQA, discuss the proposed change and have a proposal of why part of the PPAP you believe should be re-done (if anything) or if you propose no re-PPAP be ready to discuss why you don't believe anything is necessary.

If I was your SQA my first questions, from what I know so far, are "...What was the old sequence and what is the proposed new sequence (I want to see the old and the proposed revised control plan, please)? Why are you rearranging the sequence...?"

 

[JRKH]

Clarification

One quick and easy example would be:

Sequence 1: Shear; Punch; Bend; Plate; Stock

Sequence 2: Punch; Bend; Plate

Sequence 3: Shear; Drill; Bend; Plate

The reason for no shear in sequence 2 is that the punch has a shear built into it.
Sequence 2 is preferable due to cost, and is the "control plan" but sequence 1 or 3 might be needed to adjust workloads in the shop.

My feel is that if the processes used are capable we should be able to utilize the most efficient one.

James

 

[Marc]

> My feel is that if the processes used are capable we
> should be able to utilize the most efficient one.

I have no problem with that. Nor do I think anyone cares that you use the most efficient one. I suspect that's what everyone wants anyway. But - if you're selling to me (automotive) and you tell me you're going to use process / sequence #1, and that's what you qualify, I want notification of any change before you change. If you pre-qualify and get acceptance on all three 'sequences' or machines - that's another story.

The problem is when you tell me you're doing one thing and change - even though it's to "...another capable process..." There are other possible ramifications of a sequence / process change. What if the 'alturnate' process is on the other side of the plant and handling between the two locations becomes an issue?

If what you are doing is not significant on the product, there probably won't be a need for anything other than a runoff to ensure your claim of stability/control is correct.

 

[Al Dyer]

I don't want to get deep here, but:

Encapsule all the possible "probabilities into the control plan. Say we are going to do it this way unless XXXXXXXXXXXXX happens then we will do it that way. That way when you submit your warrant or PPAP the customers know that you have studied the process, have taken into account changes in the process, and that you are pro-active!

Let words be your guide!

 

[Atul Khandekar]

Al's suggestions make sense. Is your customer not consulted when you decide upon process sequence? You could ask your customer to approve alternative sequences. If, as you say, all the processes are stable and capable, this should not be a big problem.... unless the customer is too finicky !

- Atul

 

[Marc]

You lay out a process flow for manufacturing a part. There are certain operations (processes) in it. All operations (processes) are stable and in control. Give me an example where you want to change from one stable process to another stable process. We are at process A. We usually move to process B but want to move from process A to process C. What are processes B and C? Are we talking a sequence change? Is the other 'capable process' a different way of doing the same thing? Are we talking a different machine (as opposed to a process) which does the same thing but that the part in question is not specifically qualified on (although the machine is used on other parts and is proven stable and capable)? Also.... What is the purpose of the change and is the change a permanent change?

Let's get more specific here. This thread started out with:

> if we reroute a part from one capable process to another,
> this would not constitute a process change for this part

So far everything is too vague. Without details, we're resorting to tangent rhetoric.

 

[Atul Khandekar]

From JRKH's post above, the problem IMHO is one of production scheduling and workload adjustment. Say, something like if i have one regular machine ( part of the original sequence - combination of shear and Punch) under breakdown, can this process be carried out on 2 alternative machines (separate processes Shear and Punch) ? And what effect would this have on PPAP?

Again as Al has suggested, if the alternatives are covered in the control plan, new PPAP may not be necessary.

- Atul.

 

[JRKH]

I'll try to clarify. As mentioned in an earlier post options would be:

Sequence 1: Shear; Punch; Bend; Plate; Stock

Sequence 2: Punch; Bend; Plate

Sequence 3: Shear; Drill; Bend; Plate

The part I am making is a copper plate with 6 holes in it.


The difference between Seq 1 and Seq 2 is minimal. The part is produced by the same method, it simply combines the shear and punch into into a single operation/machine. However since I have only one of these machines I want to keep my options open.

The difference between Seq 1 and Seq 3 is that the holes in the part are drilled instead of punched. This method is not as fast as punching, but if the punches are overloaded, and the drills have open time, the production manager might wish to manufacture this way instead.

Does this help? I appreciate everyones input.

I like Al's idea. I just never thought of that as being ok.
So I should be able to say punch or drill on the control sheet, and specify which is prefered.


James