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Urgent! Opinions wanted : Vendor Supplied CAD Files


Urgent! Opinions wanted : Vendor Supplied CAD Files

First off, I apologize if this is the wrong forum....

There is a big dilemma where I work right now. We have process units
which were done in Pro-E that we have sent out to bid. Some models used
within the Pro-E models do not have a Pro-E drawing associated with the
model but simply have an old hand drawing. Apparently we are getting
some feedback from some vendors that they want models. I assume they are
talking about STEP files for example to compliment the drawings they
will be receiving in hardcopy format. Now the models were created to
nominal with the tolerancing referenced on the drawing with a note :
Machining tolerance per js-Js13 (ASME B4.2)

It seems to me that as long as the vendor has the drawing with the
required dimensioning and the tolerancing noted either through the note
above or actual tolerancing within the dimension, that the STEP file
could be used by them to input into their CNC for example with the
understanding that all tolerances are included on the drawing and not
necessarily in the model.

There are people here jumping up and down thinking that we may need to
create Pro-E drawings for all of the parts that only have a hand-drawing
(of course the deadline for finishing the project is looming). I just
don't think we will need to do that. I am wondering if anyone with a
better machining background can help me understand the vendor
perspective. I have been asked to be included in a big meeting tomorrow
to discuss these issues. It seems to me the vendor wants the STEP file
to import to make their job much easier and less time consuming.

How these issues were never thought about from day one boggles my mind,
but apparently they never were.

Also, as an aside, are there any add-on software packages that you know
of that could automate the process of creating step files for models? I
really would like to avoid pulling up each part and saving as a STEP
file for example.

Any responses to this blanket inquiry would be much appreciated.



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I have no machining specific experience, but I would say that you can
sent them the files but the old hand drawing controls all dimensioning
and tolerancing. In other words, provide the STEP file as a
convenience, but the drawing is still 'gospel'.

We've done this in the past, most recently with a vendor who requested a
flat pattern for a sheet metal part. We don't do flat patterns simply
because every vendor has different equipment and standards. In this
case, we supplied the flat because the vendor insisted it would make
things much, much easier, but we did so with the explicit instructions
that they were responsible for verifying it and that the PDF was still
the gospel for what they were to deliver.

As far as re-creating the drawing in Pro|E, how would that better
communicate the info than the old drawing? If all you're after is a
Pro|E version of what you've already got, sounds like a waste of time.

Doug Schaefer
Doug Schaefer | Experienced Mechanical Design Engineer

That is exactly what we do. We only use step files for communicating
engineering to engineering. DXF files for flat patterns are available on
request by the mfg, but the PDF is the official drawing. If the part
does not pass the PDF and QA rejects it.


Alfonso Medina O.
Mechanical Engineer

I have to echo Doug's take on this. The 3D step file is a convenience
for the vendor/supplier. It will make generating toolpaths easier for
them. By only having the old hand drawn 2D drawing, they will have to
generate their toolpaths "old school". This probably will increase the
amount of time they need to manually generate the toolpaths. They will
ultimately pass this added labor on to you.

Regardless if they have a 3D file or not, the tolerancing and notes
specified on a 2D drawing take precedence over the 3D data.


Jeff Horacek

Sr. Designer

STERIS Corporation

5960 Heisley Rd.

Mentor, OH 44060

P- (440) 392-7721

F- (440) 392-8954


One other note regarding the 3D model vs the disconnected 2D drawing.
There may be some who get nervous when a 3D model is used for
manufacturing purposes and that model had not been verified by use of a
Pro/E related drawing. I've had these same conversations at past
employers where if the model did not undergo some sort of verification
to ensure it's dimensional reliability then somehow the model was
"useless". I do agree with the others though that ultimately the
released document (PDF or otherwise) should be gospel in when these type
of questions arise.

In reference to your "batch processing" of Step files, the probatch
facility does have an option for STEP file generation. I've used this to
create custom scripts that will checkout and process file to step
offline when necessary.

Bob Mills

Engineering Software Administrator

DRS C3 Systems, Inc.


Note that a STEP model does not contain any dimensioning or GD&T. It is just dumb geometry. It would be a different story if you were supplying a Pro/E model because then all the tolerancing & GD&T is in the model although it still may not jibe with the drawing if you use created dimensions. In any case, I think the drawing will take precedence as the legal controlling document. If the vendor is simply going to create the tooling straight from the model with no consideration of your drawing, I think you need to look for another vendor.