Creation of CAD solid models using customers supplied drawings

[BMappes]

Ok
Question #2 for me

I just found out that a co-worker is creating his own CAD solid models using customers supplied drawings.
Some customers provide models, some do not and just provide a PDF drawing

I know that what he is doing is wrong....can easily transpose numbers and create something that is not quite right...etc.

But where in all these AS standards does it say you can not create your own? I need backup to support my position.

So many docs and no time to read each and every one to find it.

A little help please
Thanks in advance
Bob

 

[dsanabria]

Ok
Question #2 for me

I just found out that a co-worker is creating his own CAD solid models using customers supplied drawings.
Some customers provide models, some do not and just provide a PDF drawing

I know that what he is doing is wrong....can easily transpose numbers and create something that is not quite right...etc.

But where in all these AS standards does it say you can not create your own? I need backup to support my position.

So many docs and no time to read each and every one to find it.

A little help please
Thanks in advance
Bob

If you are looking for a standard - try using AS9102b

but to your question, no standard will prevent you from establishing your 2D criteria. However, the customer can and will at time.

Hope this helps

 

[PaulJSmith]

We used to have a primary sheet metal fabricator who we found out was doing this, too. The only way we found out was when during the investigation of a problem they sent one of their drawings to us as evidence they were right. Turned out to be the evidence that proved that when they created their own model they had transposed the front and rear views, and as a result cut and formed the entire run of parts backwards ... a mistake easily avoidable by using the solid models supplied by our engineer.

They are no longer our primary metal fabrication supplier, by the way (for a ridiculously long list of reasons, including that).

So, standard violation or not, yes it happens, and yes it's a bad idea.

 

[qpled]

You may need to spend some extra time with any customers that only supply a PDF. Find out which models they are capable of generating so that the model itself can be imported into the CAD modeling software you are using. This reminds me of my work on CAD models of electrical designs (schematic capture, PCB's, etc...) that I did in the 1980's - back then the focus was on how to generate exportable models. I hope by now the capability is there!

 

[JAltmann]

I don't see a big problem with this practice, which is fairly common regardless of industry. Ultimately if the paper design is what the product is to be made to and certified to if this is being done then the end product is fine.

How is the making of ones own CAD different than CNC programs or forming tool creation? Their is additional risk to the company if product is made to an incorrect model, but ultimately the paper drawing would be the certification requirement, so in the case where a vendor is certifying to their generated model then they have likely violated contractual agreements which is a larger issue and one that does violate the standards.

 

[BMappes]

First...our main customer supplies a STEP model AND a PDF with each order, but our secondary customer only supplies a PDF

The first situation as I see it is that some PDFs do not correctly represent the model...exp. the PDF has a length at 3.28 with block tolerance, but the model may measure at 3.275
So depending on tolerances, most likely you can make a good part with no problem.
But if all you have is the PDF and you create a model at 3.28, but really the customer may want 3.275, you would be checking to a model that is slightly different than what the customer may want.

The second situation would be that you transpose numbers and instead of creating a feature at 3.28 you enter it at 3.82 and now your model that you are inspecting to is incorrect.....making all these parts as scrap

So, if all you have is a PDF and you inspect to that same PDF, you can't go wrong

Just my $0.02

Thanks all for your comments and suggestions

 

[Michael_M]

We create 'operation prints' off the customer supplied drawing for various jobs. In some cases, it's because the drawing is so cluttered that we 'clean' up the print to make is easily readable, other times it's because the print is for a -1, -2, or a -3 part with 1 or 2 different dimensions. In one case, a -001 part and -002 part has a single depth dimension of a counterbore that is different by .015" (one is .745", the other is .760"). In other cases, we make prints with 'pre-plate' dimensions.

In all cases, someone who knows how has to review the drawings and 'sign-off' that the operation print is good. The finish part (after plating, processing, etc) is inspected to the customer supplied drawing.

If someone with knowledge and authority can buy off the model, I don't see any issues.

 

[BMappes]

If someone with knowledge and authority can buy off the model, I don't see any issues.

The person creating models is the same person inspecting the parts with those models......kind of a double barreled thing