Hello Everyone,
What does an inverted delta on print represent?

Welcome Randy, even though I realised you were a user even before me.

If I am not mistaken, you are referring to 'rho' - Rho_(letter).

Hello Everyone,
What does an inverted delta on print represent?

Hello Randy,

I have to guess on the origin of the print you're referring to. An inverted delta on a print (possibly from Ford Motor Company and associated organizations) means that this signifies a special characteristic.

From Ford:

Inverted Delta parts
For parts designated as inverted delta (parts with Critical Characteristics), the organization shall prevent the shipment of non-conforming product to Ford.
Note: this is typically accomplished by using error and/or mistake proofing techniques integrated into the organization's manufacturing and material handling processes.

Look here (http://www.aiag.org/staticcontent/files/Ford_Specfics_for_PPAP_4.pdf) (.pdf file) for more information.

Hope this helps.

Stijloor.

Welcome Randy, even though I realised you were a user even before me.

If I am not mistaken, you are referring to 'rho' - Rho_(letter).

This is the Greek letter delta: Δ
Turn it upside-down and you have an inverted delta. What it means in terms of engineering drawings differs greatly. As Stijloor has already pointed out, Ford uses it to denote special characteristics. If you're not dealing with Ford drawings, you need to ask the customer because there's no telling what it might mean. Note that many companies use delta right-side-up to flag revised specifications on drawings.

I have to guess on the origin of the print you're referring to. An inverted delta on a print (possibly from Ford Motor Company and associated organizations) means that this signifies a special characteristic.

From Ford:

Inverted Delta parts
For parts designated as inverted delta (parts with Critical Characteristics), the organization shall prevent the shipment of non-conforming product to Ford.
Note: this is typically accomplished by using error and/or mistake proofing techniques integrated into the organization's manufacturing and material handling processes.

Look here (http://www.aiag.org/staticcontent/files/Ford_Specfics_for_PPAP_4.pdf) (.pdf file) for more information.

If the drawing is a Ford drawing the inverted delta means more than a special characteristic. It means a critical characteristic, which means a safety characteristic typically involving compliance to Federal Motor Vehicle Safety Standards (FMVSS).

If the drawing is a Ford drawing the inverted delta means more than a special characteristic. It means a critical characteristic, which means a safety characteristic typically involving compliance to Federal Motor Vehicle Safety Standards (FMVSS).

Let me remove all doubt:

From Ford CSR's:

Ford Designated Special Characteristics
Critical Characteristic ( ∇ ) Parts
Ford designated Control Item Parts are selected products identified by Ford Engineering, concurred by Ford manufacturing and identified on drawings and specifications with an inverted delta ( ∇ ) preceding the part and/or material number. Control Item products have Critical Characteristics (refer to the Glossary of this document) that may affect safe vehicle operation and/or compliance with government regulations. Unique symbols identifying safety and regulatory characteristics on components designed by other companies (e.g. Mazda) are equivalent to the inverted delta ( ∇ ) symbol. Examples are the Mazda "A" and "AR" symbols or special fastener base part numbers beginning with "W9" which are to be treated as inverted delta. Critical Characteristics for fasteners may be designated by methods defined in Ford Engineering Fastener Specifications available through Ford Global Materials and Fastener Standards, or the specification providers listed in 4.2 of this document. Other Special Characteristics Significant, High Impact and Pass Through Characteristics are described in the glossary of this document.

Stijloor.

All inverted deltas on Ford drawings should have statistical control of some sort starting with capability studies with a Ppk of at least 1.67 and long term controls such as an X bar and R chart.

Make sure that in your Control Plan you place the inverted delta in the column for significant characteristic on the specific characteristic that was shown on the Ford drawing.

Hope this helps.

This is kinda dated, but may be helpful in putting thkngs into perspective with respect o how every company defines their print contents, to some degree, differently: Print Characteristics (http://elsmar.com/APQP/sld131.htm).

Hi,

I got THIS (http://elsmar.com/external/QAP_001_Key_Characteristic_Designation_System.pdf) from the web - could be useful.

For the Ford Customer Specific Documents, refer to Ford document (http://elsmar.com/external/FordspecTS2nd_08_November_2006.pdf)

Hello Everyone,
What does an inverted delta on print represent?
The responses make Ford's use of the inverted delta quite plain.
Jim Wynne's advice about asking the customer is the only way to be certain.

Jim Wynne's advice about asking the customer is the only way to be certain.

I agree with Jim's advice. However, "asking the customer" is not always "the only way to be certain." Many questions here on The Cove deal with issues relating to customers that confuse their suppliers. Customer communication is still a challenge and often not a very effective process.

Stijloor.

I agree with Jim's advice. However, "asking the customer" is not always "the only way to be certain."

If it's not a Ford drawing the OP is dealing with, asking the customer is the only way to be certain in this case. When dealing with nonstandard symbols on drawings, third-party advice should be never be considered definitive.

If it's not a Ford drawing the OP is dealing with, asking the customer is the only way to be certain in this case. Usually correct, however I've seen lots of occasions where the drawing originated somewhere other that at the customer, and have many times seen customer SQEs (and other customer personnel) who weren't sure, or outright didn't know, what some callouts on prints were.

There definitely are times when a third party knows something that a customer doesn't. Heck, I've even seen customer originated prints that their own design engineers couldn't explain.

Usually correct, however I've seen lots of occasions where the drawing originated somewhere other that at the customer, and have many times seen customer SQEs (and other customer personnel) who weren't sure, or outright didn't know, what some callouts on prints were.

There definitely are times when a third party knows something that a customer doesn't. Heck, I've even seen customer originated prints that their own design engineers couldn't explain.

The advice of a third party carries no weight or authority in such matters. If the customer claims to not know what's expected, the only rational response is to ask him to find out and get back to you, and tell him that the work won't proceed until he does. The idea that customers shouldn't be held responsible for their own requirements, or that it might be a better idea to get a third party's unsubstantiated advice, is ludicrous.

The advice of a third party carries no weight or authority in such matters. By golly, we each have different opinions!

By golly, we each have different opinions!
And, that's why we have a forum.

And, that's why we have a forum.

Exactly!

If the customers had all the answers, traffic on The Cove would reduce by a significant amount. :D

Stijloor.

Exactly!

If the customers had all the answers, traffic on The Cove would reduce by a significant amount. :D

Stijloor.

Does anyone here really think that a disinterested third party has the authority to render a definitive interpretation of a customer's ambiguous requirements? If I have a drawing with some ambiguous or irresolvable callout, and I call my customer and ask for clarification and he says, "Gee, I have no idea what it means," and I accept that answer and then ask someone else what he thinks the callout means, and I proceed based on that interpretation, and it turns out to be wrong, do you think the customer will let me off the hook when I say, "Well, Henry said that was what you wanted"?

Does anyone here really think that a disinterested third party has the authority to render a definitive interpretation of a customer's ambiguous requirements? If I have a drawing with some ambiguous or irresolvable callout, and I call my customer and ask for clarification and he says, "Gee, I have no idea what it means," and I accept that answer and then ask someone else what he thinks the callout means, and I proceed based on that interpretation, and it turns out to be wrong, do you think the customer will let me off the hook when I say, "Well, Henry said that was what you wanted"?

Jim,

Often, a response from a "third party" may help a supplier clarify/formulate the right question for a customer. I believe it's about gaining some insight, not necessarily seeking a "binding" response. I don't think that's the intent here. I found it very interesting to explore the intent of many of the questions here at The Cove.

Stijloor.

Jim,

Often, a response from a "third party" may help a supplier clarify/formulate the right question for a customer. I believe it's about gaining some insight, not necessarily seeking a "binding" response. I don't think that's the intent here. I found it very interesting to explore the intent of many of the questions here at The Cove.

Stijloor.

I understand, but that has nothing to do with the fact that customers are responsible for providing unambiguous requirements, and being available to explain themselves in the event that explanations are needed.
An illustration from my own experience: I was working for an injection molding house, tier one to GM. With a QS9000 registration audit looming in the near future, I was given a drawing to review for a new job. I noted that there was a symbol on the drawing (a circle enclosing a crosshatch) which was normally used to denote a point on the part for impact testing. There was no impact test specification on the drawing, however, nor was there any other indication as to what was intended.

A call was placed to the "cognizant" engineer, who said that if there was no impact test spec on the print, I shouldn't worry about it. I was fine with that, so long as he was willing to put "Don't worry about it" in writing. He wasn't willing. So I told him I needed a definitive written answer before we could go forward. He wasn't happy about it, but told me he'd get back to me. After a few days of not hearing anything, another call was placed. My contact engineer was on vacation, I was told, and wouldn't be back for a week. I asked who else could help me, and was told that no one could.:mad:

To make the rest of a long story short, it was like pulling teeth but I finally got an updated print with the symbol removed. It turned out that the first version of the print did indeed have an impact test requirement, but the requirement had been removed, and the symbol had been inadvertently left behind. The interesting thing is that the drawing had gone through these changes without a formal change procedure or revision bump, and I now had two different drawings at the same revision level. :bonk:

There was no point during all of this when I could have asked someone else why there was an impact test target on the print, but no specification and expected a definitive answer. That's because when nonstandard symbology of any sort is in evidence, the only definitive answer is from the customer. All else is guessing--educated guessing perhaps, but still guessing.

And, that's why we have a forum. Yuppers, that's why. One instance of several I had in mind is Harley. I've done work for them and customers of theirs since 1996. Working with their customers I have had to get outside consultants who are GD&T/Print experts to correct Harley prints many times. It was a pain, but I've had to get Harley design people together with my GD&T/Print consultant and the customer to completely redo prints from Milwaukee because the prints were so screwed up. I will admit that prints are a tough world, so to speak. My major complaint was the customers, rather than Harley - They accepted a contract and didn't have anyone who was expert in reading prints so they accepted contracts they *thought* they could make/measure. The prints for the V Rod were a nightmare which required a lot of outside 3rd party help with Harley prints.

Hello Everyone,
What does an inverted delta on print represent?

Hi randymhl,

Was it an actual "Ford" print?

Now I am curious.......;)

Stijloor.

This conversation got me to thinking (yes, I know that's rare for me....), so I started this discussion thread: Prints / Drawings - What Problems Have You Had with Prints? (http://elsmar.com/Forums/showthread.php?t=24675).