Control Plan (Product/Process specification/ Tolerance) acceptance

outdoorsNW

Quite Involved in Discussions
#11
While some to many of you have not run into these problems, there are situations where putting all of the details into the control plan will not work. Experience has made me think standard control plans do not work well with highly complex parts and processes. High mix-low volume with a lot of automation is another situation where control plans may not work well.

When you are running 200 part numbers at any given time where many of the parts use various combinations of standard processes, referencing a master set of process documents makes process changes easy and reduces the chance of one part being missed.

Some parts went through over 250 processes stations, with a lot of circling back to the same process station. In some cases all the parameters would be the same and in other cases the process would be adjusted or a different program used. (Cleaning steps are an example of reusing the exact same process more than once.)

And is case you are wondering, we were AS9100 with lots of aerospace, technology, and industrial customers.

Information should not have circular references that lead nowhere and neglect to provide the information needed. But circular references can be a good thing if important document A references important document B and B references A at a high level, the focus of each document is kept clear and specific information is not duplicated. That way no matter which document someone starts with, they know the other document exists and they may need to check it.

Requirements that need photos to properly document can't be put into control plans without the photo being really small or the control plan really big. Reference samples also must be referenced in the control plan. Complex process flows and process requirements with many conditionals also work much better as a work instruction with a flow chart.

Some processes require more columns. One engineer at a previous job created his own version of a control plan. Management asked him to use the standard format but even after transition time we found his custom format worked better for the process and resulted in fewer errors by presenting information in a more clear format. He used columns for each category of process parameter and color coding that reduced errors. Based on what he did, I think when a process gets too complex, the standard control plan does not work well.

Also, in a high mix job shop, referencing part specific items on the control plan can become cost prohibitive. At a past job, the part traveler contained the critical part specific information, most of which was electronically transferred from the customer data to the shop floor system to the process machine. Putting part specific data on control plans would have required 2 to 4 people doing nothing but creating custom control plans for each part with no added value. Customer drawings were used when specific requirements needed to be verified against the traveler, machine setting, etc. Buying software would not work. The company had an internally developed and maintained shop floor control system that while using outdated technology and ugly looking had better automatic traveler creation than anything on the market. The company wasted several million dollars (plus the software company likely wasted more) trying to replace it only to find they could not. A part specific control plan with all the part specific specs was only created if the customer was willing to pay for it, and once they visited and saw how automated things were, none ever did pay for one. We lost a few potential customers, but those customers were likely a poor fit anyway.

When you have proprietary processes, you have to keep the details out of the control plan. At a past job we had a process where the supplier of the process chemicals and equipment limited disclosure to need to know. Only about 20 people out of 300 had a need to know. Customers were out of luck. Many customers grumbled, but found everyone offering the process was subject to the same rules. We later developed a different proprietary process There was a lot of R&D involved but the end result only required one common chemical and three process parameters. Too easy for someone to memorize. Again not disclosed internally except on need to know. Again customers grumbled, but the choice was accept no disclosure of any type or we would not use the process. Since nobody else in the industry could do this combination of requirements, we did not disclose.
 
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Ron Rompen

Trusted Information Resource
#12
Just echoing what many others have already stated here. On most of our Control Plans, we reference the 'Process Specifications'. This is for a few reasons:
1) The process limits and specifications that we have developed are proprietary knowledge. To openly share them would (potentially) expose us to unfair competition
2) The control plan is not the document which is used by operators on the floor - they use their process sheets, which DO clearly show all process tolerances.

We have been audited on this numerous times, and in each case, once our process (and the rationale for it) was explained to the auditor, they were satisfied.
 

John C. Abnet

Teacher, sensei, kennari
Staff member
#13
The specifications/tolerances for part and process requirements should be explicitly cited
Respectfully disagree @Jim Wynne ;
As you know, there are some industries with extremely proprietary process controls. Are you advocating forcing those organizations to hand those explicit details to the customer?
Many years in first tier OEM supply was never met with push-back from the customers. In all cases (my experiences), the customers well understood the need to not disseminate proprietary details.

Please help me understand your logic in this. Why would an organization do this?

Be well.
 

Jim Wynne

Staff member
Admin
#14
Respectfully disagree @Jim Wynne ;
As you know, there are some industries with extremely proprietary process controls. Are you advocating forcing those organizations to hand those explicit details to the customer?
Many years in first tier OEM supply was never met with push-back from the customers. In all cases (my experiences), the customers well understood the need to not disseminate proprietary details.

Please help me understand your logic in this. Why would an organization do this?

Be well.
Can you give an example of an "extremely proprietary process control"?
 

outdoorsNW

Quite Involved in Discussions
#15
Here is an example, based on a prior job. You work in an industry where for the most part everyone uses one of 2-4 industry suppliers for a process.

Your company figures a way to do something nobody else can and that is in high demand by certain segments of the market. The industry suppliers don’t know how you do it. The method can’t be reversed engineered from the final product because the final product has only the result and not the inputs.

The method is easy for someone in the industry to duplicate once they know the details, so the company needs protect the details to maintain an advantage as the only company that can do this particular process. While there are substitutions in the market, those substitutions have weakness that the proprietary process outputs do not, and as a result you can get a nice profit margin on this process.
 

Jim Wynne

Staff member
Admin
#16
Here is an example, based on a prior job. You work in an industry where for the most part everyone uses one of 2-4 industry suppliers for a process.

Your company figures a way to do something nobody else can and that is in high demand by certain segments of the market. The industry suppliers don’t know how you do it. The method can’t be reversed engineered from the final product because the final product has only the result and not the inputs.

The method is easy for someone in the industry to duplicate once they know the details, so the company needs protect the details to maintain an advantage as the only company that can do this particular process. While there are substitutions in the market, those substitutions have weakness that the proprietary process outputs do not, and as a result you can get a nice profit margin on this process.
I was hoping for a specific example. What is it about your non-specific example that would prevent you from showing specifications, tolerances and measurement methods on a control plan?
 

Jim Wynne

Staff member
Admin
#17
I should clarify here that the OP's question was specific to "...what to accept under the specific column (Product/ Process Specification/ Tolerances." This has nothing to do with identification of potentially sensitive information with regard to identifying specific processes. You can claim that identifying a process is proprietary but still show the specifications, tolerances and measurement methods.
 

outdoorsNW

Quite Involved in Discussions
#18
Jim,

Are you referring to process or product specifications, tolerances, etc.?
I thought the context made clear I was referring to process specs and tolerances. I don't see the OP as clearly limiting the question to one or the other. Obviously, customer supplied product specs are not proprietary.

Looking back at the original questions, if you follow the concept of avoiding unnecessary copying of information in order to prevent errors, then referring in the control plan to information sources (process or product) that are readily available to the person who needs to know reduces opportunities for error.

Having many control plans with identical specs for a process creates opportunities for error if one or more control plans is not updated when the process spec changes. Good process control often requires software with automatic alerts, process test data capture (both automatic and manual), process related control charts, and other functions not found in typical software used for control plans.

The OP is concerned about circular references. Yes they can occur, but so can errors in copying or updating data. A circular reference with no data should cause someone to ask for help getting the correct information. A error in copying information is less likely to be caught and therefore non conforming product is more likely to be passed or a out of spec process to be used.

Auditing a control plan that references other data sources is more time consuming, but a proper audit should verify information against the master source. Unless the control plan is the master source, the control plan should be verified against the drawing, specs etc.
 

Ron Rompen

Trusted Information Resource
#19
I was hoping for a specific example. What is it about your non-specific example that would prevent you from showing specifications, tolerances and measurement methods on a control plan?
Jim: A specific example (from my personal experience) would be a tempering process (time/temperature dependent) for strip steel which needs to meet specific physical parameters (yield strength and % elongation). When I was involved in the project, we were able to find only one manufacturer who could meet our requirements, and they spent quite a bit of time (and money) in developing their process.
 

John C. Abnet

Teacher, sensei, kennari
Staff member
#20
I was hoping for a specific example. What is it about your non-specific example that would prevent you from showing specifications, tolerances and measurement methods on a control plan?
Good day @Jim Wynne ;
@Ron Rompen gave a good example. My personal experiences are similar, with thermal processing (austenitizing time/temp, etc...) And many of the organizations I have worked with (aluminum casting, "BOP shop chemistry" [steel mills], , etc...)
 
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