Tolerance block on customer drawing - Major interpretation problem with customer

Jim Wynne

Staff member
Admin
#21
I was not arguing that point. As you can see, I also stated that unless you can prove otherwise, using the Customer's Drawing Standard or something more concrete, how is the determination that the customer is wrong?

I have challenged numerous customers errors, but I have supported that with documentation.
I'll defer to the noted quality guru Bob Dylan, who said, "You don't need to be a weatherman to know which way the wind is blowing." While it's a good thing to be aware of the standards a customer might be using with regard to engineering drawings, and qualifying new customers should always include questions about it, we generally don't require reference to standard when the customer gives an explicit specification. In the current example of wall thickness, the customer specified the required thickness without direct reference to a tolerance, in which case it's universally known (or should be) that the block tolerance is to be applied. That's why there is a tolerance block. Are you suggesting that every dimensional specification on a drawing should be questioned if it's not given a tolerance directly, or that we need a standard to tell us whether or not to apply the block tolerance?
 
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D.Scott

#22
However, we have to pick our battles, and in this case, I think we have agreed the supplier failed to do proper review of the drawing. So, this case might not be the right battle to apply your philosphy.
Sorry, but I'm not sure we have agreed that. Jim's point is that there is no reason to not trust the print the customer supplied. The correct interpretation is the one Jim outlines. The parts were supplied to the specifications called for on the drawing. Further review of the drawing wouldn't bring the problem to light.

What we have agreed is the need for understanding of the perception on both sides of the coin. This can only happen in contract negotiation or review. Both sides have to be sure they are understood before a contract is drawn. Both sides have to accept a portion of responsibility when a miscommunication occurs.

In this instance, I feel the parts were supplied to spec. Any action on the part of the supplier would be a concession for customer relations. The customer needs to look at their system of communicating purchase requirements to their suppliers. Don't be smug though supplier, you knew you were dealing with a difficult customer. Your communication may have been a bit lax too.

Another thing I agree with Jim on is that this horse will never be dead. Communication is at the root of far too many issues and nonconformity. There can never be enough discussion about the need for effective communication. Examples like this should be added to a banner page so as many people as possible will read it, add to it and learn from it.

Dave
 

Helmut Jilling

Auditor / Consultant
#23
Sorry, but I'm not sure we have agreed that.
Actually, I was referring to Jim and I (and Wes) agreeing. See post #14 and #10.



Jim's point is that there is no reason to not trust the print the customer supplied. The correct interpretation is the one Jim outlines. The parts were supplied to the specifications called for on the drawing. Further review of the drawing wouldn't bring the problem to light.

The specs on the print contradicted themselves. That would and should be brought out in a drawing review. It was that point I thought we had pretty much agreed. Perhaps not, but the next quote seems to suggest you agreed that contract review should resolve such differences.

What we have agreed is the need for understanding of the perception on both sides of the coin. This can only happen in contract negotiation or review. Both sides have to be sure they are understood before a contract is drawn. Both sides have to accept a portion of responsibility when a miscommunication occurs.
Certainly.

In this instance, I feel the parts were supplied to spec. Any action on the part of the supplier would be a concession for customer relations.
I feel the specs almost contradict themselves, so it would be impossible to meet the spec unless the part is near nominal. These parts were clearly no where near nominal. Significantly off nominal.


The customer needs to look at their system of communicating purchase requirements to their suppliers. Don't be smug though supplier, you knew you were dealing with a difficult customer. Your communication may have been a bit lax too.

Another thing I agree with Jim on is that this horse will never be dead. Communication is at the root of far too many issues and nonconformity. There can never be enough discussion about the need for effective communication. Examples like this should be added to a banner page so as many people as possible will read it, add to it and learn from it.

Amen.
 
D

Dave Dunn

#24
The specs on the print contradicted themselves. That would and should be brought out in a drawing review. It was that point I thought we had pretty much agreed. Perhaps not, but the next quote seems to suggest you agreed that contract review should resolve such differences.
If I understood the description of the specifications, and the OP can verify, the specifications as listed were clear cut. The dimension was .460 min. Since a minimum tolerance was applied to the specification, the title block tolerance (±.010) would not apply. QMMike, is it correct to state that there is no other tolerance applied to the individual dimension aside from "min"? It would be helpful if you can show us the area of the drawing.

In the case of wall thickness that was brought up listed as a spec of .060, since no tolerance was applied to the individual spec, the tolerance block should apply, overridden only by specific wall thickness notations, or by design requirements of specified features of the part that would change from the nominal wall thickness.

In both cases, at least to my understanding, the specifications are clear and if there is a design issue resulting from the customer not expressing what they really need, then they need to correct the issue. As a good supplier, it would be to our advantage to assist in helping them express what they need.
 
D

Dean Frederickson

#25
There is not a contradiction with these tolerances, when you have a direct tol. (.460 min) then the tolerance block does not apply. Its that simple. Those parts should be made to the .460 min call-out. There would be no reason to even question this during the quoting and contract review processes.
 

Wes Bucey

Quite Involved in Discussions
#26
Somewhere I missed whether or not there had been a First Article inspection by the customer BEFORE supplier committed to manufacturing or shipping an entire order of extrusions.

Often, the very nature of extrusions gives rise to "afterthoughts" by customers when they see the First Article. At that point, even though the part may be to print, both customer and supplier can negotiate a fix without either side taking a big financial hit.

As some here have alluded, sticking too hard to a point of view may win the battle, but lose the war. Suppliers do well (except in automotive) by holding themselves out as "helpful partner and mentor" about the supplier's area of expertise about the idiosyncrasies of the manufacturing process which may not be apparent to the customer. Sorry to say, the automotive OEM can be brutal if they sense a "weakness" in a supplier.
 
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