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Is a model good enough?


Is a model good enough?

Posted this a few days ago and not sure as to whether or not it went through, so trying one more time. This also piggy backs a little on the "should scale be removed" thread.



This does dovetail nicely into my initial Thread-bomb. It all depends on how you define your product?

Here are my thoughts - because you asked.

I agree with your bottom line - "not sure if we're there yet" I would go
one step further and say "we're not there yet." Yet being the operative

The model used to communicate the geometry to the vendor is generally a STP
file these days, right? IGS becoming less common / popular and DXF still a
decent choice for 2D geometry (e.g. for laser cut sheets, etc)

The PDF of the 0-60-100% detailed part is generally used these days for
over-alls, critical-to-function or inspection dimensions, hole call outs,
tolerances, material, finish, etc.

While all this info can now fairly easily be included with the NATIVE 3D
part, the "dumb solid" has yet to allow that capability. (to my knowledge -
and if it is capable to put that info into a STP, it's likely my vendors
will need some training to use it)

My practice is, for several reasons, to not send out native files to a
vendor. These reasons include client confidentiality, revision control,
software access/capability of the vendor, file size, convenience, risk of
accidental change, etc. One exception is a sheet metal shop I use begs me
for the native solidworks files - they actually charge me less because it
saves them engineering time. But then there is the real challenge I have
with them when they make a change on the fly to make their job easier and
then need to communicate that to me and I need to either recreate the change
on my model, or take their modified parts and slip them back into my assy. =

But I envision a time when a new 3D dumb solid format comes along that can
handle annotations much like a DXF supports dimensions and text. Then, we
will be ready to submit our designs for quote without a 2D pdf.

I look forward to that day.


23-Emerald II

Maybe a couple months ago there was a discussion on ASME Y14.41 (MODEL BASED DEFINITION).

5-Regular Member


The answer to your question "Is a model good enough?" depends on all the
people internal and external
who need to touch your company's drawing. Preference aside, you would
need to implement the tools needed
so that everyone in the chain has the solution to perform their job,
design, manufacturing, inspection
, etc. Model annotations allow the user to generate a "3D" drawing so the
amount of effort is basically
the same for engineering if you decide to product fully annotated models.
Since your drawing is like you said a contract, you need to format the
model's output to
address all of legal attributes also. Model based definition has come a
long way but each company is very
different and has to address its individual needs.

Best Regards,


Is a model enough? Yes, see ASME Y14.41 or the corresponding ISO DIS 16792 both of which are entitled "Digital Product Definition Data Practices". It will lay out everything as far as what is needed to enforce the design intent of the model onto the manufacture of the part.

I like how you put "Not necessary to manufacture a part, but necessary to ensure that a part was manufactured correctly." because that is one of my main sticking points to jumping on the bandwagon (though not my only one). If your supply chain can support inspection without having to reference a drawing (either you supply or they create from your supplied model) then you are a long way there. Until I can answer that question affirmatively, I will refuse to rule out good quality suppliers for a questionable savings by doing away with drawings completely. I fall in the "in-between" drawing level camp. I have had great success with critical to function (CTF) drawings where dimensions are only included if they are critical and therefore need to be inspected.

As I was responding, Nate Rollins got in with an excellent response that I will just add to by mentioning the new STEP standard (AP242) from LOTAR International. LOTAR is the Long Term Archiving And Retrieval organization working on the problem of how to make files accessible fifty years from now without losing all the annotation information. The 3D CAD vendors are working on including it in future versions. It will NOT include the history tree directly but will carry over design intent based on annotations.

Rob Reifsnyder
Mechanical Design Engineer/ Producibility Engineer / Components Engineer / Pro/E SME / Pro/E Librarian

A fully detailed drawing is a narrative from the designer or engineer to the inspector about what constitutes an acceptable part. Drawings are easily reproduced, easily annotated, and easily distributed.

A CAD model, so far, has none of these features, except within its own ecosystem. Even then it can be unclear because of the many ways in which the software fails to record accurately what the designer or engineer required.

A well-made point. I would counter that a generally accepted and adopted model viewer and display convention would complete that narrative (See ASME Y14.41-2003) as well without the need for secondary files (.drw’s)

In response to what Robert said:
"LOTAR is the Long Term Archiving And Retrieval organization working on the problem of how to make files accessible fifty years from now without losing all the annotation information."

There is a lot more to this problem than the file type. The long term viability of the storage media is the real issue. The fragility of digital media is the real long term problem. If you need long term storage of your design. Then I think you should be creating fully detailed drawings. Not everyone needs this level.

Remember punch cards? Back in the early 90's we had a lot of critical historical design data in card decks. At the time we only had one working card deck reader. We spent quite a number of hours getting that data read into our system at the time.

A few years ago I needed to make some changes to a design that had been done in ProE in the early 90's. The files had not been brought forward in our system because at the time they had been archived on a ¼" tar tape. I located the tape, but no one had a working cartridge reader.

Last year I was out in one of the Labs and took down the serial number and vendor for a glove box that was built in the 70's. I called up the vendor to see if they had any drawings. The guy looked in his computer system and said no, we don't have any drawing for that. I hung up. A few minutes later he called back and said, "guess what, one of our old guys suggested I look in the flat files, and we found the velum's, I make some blue prints and send them to you."

The moral of the story, is if you're looking for real long term viability of your design. Paper is still the one of the top formats. Even newsprint which has a horrible life span compared to velum, will last over a hundred years easily. I have family photos I've scanned that are easily over a hundred years old.
I think the gold standard for longevity is still Microfiche.

History is littered with data formats that are no longer viable.
VHS tape
Removable hard drive platters
8" floppy disks
5 ¼" floppy disks
3 ½" floppy disks

I predict CD's and DVD's will be next.

David Haigh

It would - were one to exist. I think there is no chance that a good one will ever exist** as that would guarantee unambiguous interchangeability of models between CAD systems. There is no motive for CAD software makers to make interchange that easy.

Some can use interchange, but the ones I've heard successful are the result of communications and documents outside the model that provide critical information the model does not contain. Tolerances, materials, datums, surface finish and lay. These are items that are not well represented in interchange models.

'14.43 does not supplya description of a model viewer or sufficient display conventionsto be useful. Independent companies can't build software that complies with '14.43 and works interchangeably. The XKCD page on standards comes to mind.

** My lifetime limitation and all that. The future is a very long time.x

In Reply to Bob Lohbauer:

A well-made point. I would counter that a generally accepted and adopted model viewer and display convention would complete that narrative (See ASME Y14.41-2003) as well without the need for secondary files (.drw’s)

Just to add a little bit more to the discussion ...

One of the big problems I saw in a facility trying to use 14.41 was the ease of looking over a model compared to a drawing. Even with users proficient in Pro (engineering staff) having them query each feature individually to get dimensions, GD&T, notes, etc. was a nightmare. As far along as Pro has come since that experience (WF3) it still strikes me as a rather cumbersome process compared to just having everything right there on a drawing.

In my personal experience there are a lot of people that have mentioned they just cannot check over a design as thoroughly on screen as they can with a paper copy right in front of them. Even when they pull up the drawing on screen more stuff in need of correction gets missed than with a printed-out drawing.

Any time you need to have that information in the field, rather than in the office, you'll run into additional problems. Not just making sure a user is present that knows how to manipulate the software, but also just getting the information to the site, either due to file size or on occasion the remoteness not allowing for any kind of interconnectivity. (Think of stuff assembled in the field, like mining trucks and such.)

You mean this one?

Thanks Nathan,

That's it -

A perennial favorite.


This is an excellent point.

robert.reifsnyder touched on this as well. I have actually passed up good
shops that can do the work better, cheaper and quicker, just because they
work from a 2D print and “I don’t have the time to make a fully dimensioned
working drawing” (like I used to for every single part I designed
) I hate
admitting that, but it is a fact. Moving toward an annotated 3D model and
adopting that as the standard for developing manufacturable parts, will
undoubtedly diminish my choices for capable shops. The ease of readability
is key to success and efficiency in the whole process.

And, Robert - Thanks for the LOTAR STEP AP242 standard lead. I am not
surprised to learn of that today. I will check it out.

And, David – I know you are not the only one who has found unparalleled
success using PAPER archives when electronic media failed. I speak from
first-hand experience as well. But don’t fear, Google likely has a solution
for that coming soon.

Good discussion. Thankfully I have time for it today.


I wonder if there is a way in the model to invoke a plane in the future?
That plane would represent a sheet for the annotations.
This might make it easier to read kinda like a drawing???


I am enjoying reading about this topic and everyone's emails. I think that this would be a great topic to discuss at the PTC Live conference. There is a Technical Committee that is dedicated to this subject. Perhaps we can get more insight from them. I will ping the TC chair and see if they can post any summaries. Here are the ramblings of an old man.

I agree that I am somewhat old school in some of my thought processes. I cannot count the number of times that I thought I had a perfect drawing only to redline it as it came off the printer. There is something different seeing it on paper than on a computer screen. It may be my training and just how I think and see.

I still think that many of our old practices are just that. Old practices that everyone is use to. I can remember people telling me that CAD will never replace the old board drawings. I also heard that 3D is just a toy and will never replace 2D. I think we are on the verge of making the type of changes being discussed below. I have several theories in life and I call this one I call the Egyptian theory. (Not that I have anything against Egyptian's it just that they created paper and started this whole drawing thing I am sure.) Once the paper drawing started, standards were created to make it consistent. (Scale is one of those items. You needed scales so people could buy scaled rulers to create lines and measure and fit on a sheet of paper.) Often the rules end up overriding the reason. There are rule makers and rule enforcers. The enforcers cannot change the rules they just make sure they are followed. The rule makers end up going away but the enforcers remain. Hence we are in the state of flat thinking.

I have been wondering about all this for assemblies for a long time now. What is an assembly drawing? It is just a bunch of instructions. What are the components, how to they interrelate? Are there any special instructions (mark, torque, paint, stake, don't drop...)

In the CAD world, a large assembly drawing can get cumbersome but by current reason are still necessary. We spend lots of time adding balloons, note callouts, sections, detailed views all just to describe what is this beast and what are its requirements? Most often, assembly drawings do little for the manufacturing build. Most manufacturing people make their own set of drawings detailing the steps to reach the conclusion that the drawing is trying to convey.

On a drawing format you want to know bits of information. Model name, revision, change history, who to blame (signatures) general tolerance block, descriptive information about views and dimensions by specifying standards.

I could go on, but I think I have made my point.

It seems ludicrous that with all the technology we have we still have to record all of this on paper. I have PDM systems that track every revision. I have tools to verify what changed between every iteration. I know who created, who changed, who approved. I can automatically create paper or electronic versions. I have files that control materials, access specifications, generate notes and memo's. I can create light weight versions and put them on a device that I shake to get an exploded view. It is overwhelming the amount of information that I have and can share at my fingertips. Yet, I make a drawing using the same methods and standards as it was done with charcoal and pounded papyrus reeds.

I agree with David on the fact that paper it probably the most reliable method for long term storage. Software vendors will only let you go back a number of versions. Operating systems change, media changes and some companies go out of business and there is no longer any way to get the data.

Currently I don't have the answer to all of this. Yet I think we still need to push for new and better ways to document and convey what we want built and how it is to be done.

Ronald B. Grabau
Roseville, CA

With this idea about the plane of notes and Ron G's response (Egyptian theory) it got me wondering. Maybe we could create a "slab" part and then "engrave" the annotations in the slab to accompany the actual part. Then if a hard copy was needed it could be out put on a 3D printer.

Just Kidding of course, well about the 3D printer part. It's Friday eve.

Mark A. Peterson
Design Engineer
Varel International


I do not dispute the fact that we can pack a 3D model full with all of the necessary information needed to make the part/assembly. However, before we crumple up all of our drawings and toss them in the garbage can, I think we need to consider the person that will be fabricating/assembling/inspecting the real world part/assembly. Do they have the necessary tools to extract all of the valuable information from the 3D model? Are those tools easy and accessible to use for this person in his/her working environment? If this person, ever, at anytime needs to write something down due to a lack of these tools, they've instantly justified the need for a drawing. I don't see a computer sitting next to every machining center on our shop floors. So it will be a while yet before we can eliminate drawings.

Tim Knier
QG Product & Support Engineering
A Subsidiary of Quad/Graphics
Sussex, Wisconsin
414-566-7439 phone

I agree with the historical media problems and one might include serious IT
stuff like ½” magnetic tapes too.

I think the future is safer and from a superficially intangible medium – the
Cloud. Server hardware will come and go but the worldwide investment in data
“in” the Internet gives me hope that I can keep and access a very large
stream of bits by a human understandable name (i.e. a file) for a very, very
long time provided I curate it, verify its checksum and move it around the
net as servers come and go.

The challenge of whether those bits will mean anything is much bigger and
here we might come full circle in the argument. PDF has a big enough
presence to last – so I bet on the most recoverable design being in PDF
files of conventional engineering drawings stored in public or private Cloud

John Prentice

I read Johns comment and find myself thinking "Sure...but all it takes is one large micro-burst ...all my paper prints will still here."
And that is not beyond the realm of possibilities. 😉

My .02....

I have heard the buzz "drawingless environments" for 20 years or more. Many keep trying to make it all "cool and 22nd century" butfolks, remember, just because we "can do it" does not mean we "should do it" or it is the "best way to do it". Tim Knier has thecorrect thoughts on this thread in my opinion. This is not a technology question as much as it is a Human Being question. We simply do not operate well by interrogatingmanufacturing info on the screen when the rubber hits the road. It's really difficult to garner all the correct info in that manner. That is not how we operate or disseminate information in an optimum manner. We are not machines and we make mistakes.

The big (eternal)issue is noteveryone "models" their parts in the exact same way those parts and assembliesmight bemanufactured or inspected. Ask yourself this question: Do you ALWAYS, 100% of the time, model your parts with the manufacturing AND inspection processin mind? Or better yet, once you know how the parts are going to be manufactured/inspected, do you go back and remodel your parts to mimic that methodology if your parts were not modeled that way in the first place? If you do not, then this thread is essentially pointless. In other words, you can't have it both ways. You cannot be lazy in modeling and then simply let the manufacturer figure it out.

The reason we have "Arms length transactions" in things like real estate and legal matters is because we absolutely "need" the human element in the process to mitigate error. Sure, one could argue that the manufacturing/inspection process needs to usethe 3Dmodel to be correct because that is the "master". But, I submit it is better to create the 2D that explicitly states your intent as the product developer. For me, I choose to do the 2D when it ismission critical ensuring they get the full picture with less opportunity to get it wrong.

Being an old timer, I consider the 3D only asthe lazy way to product. Too risky in my opinion.


Dean Long,

You have said what I think a lot of us have been thinking. We all love
technology and see where certain elements of technology can help us. But
there are a lot of people who will never work well from a 3D model, no
matter how it is packaged.

My proposal is to have a hybrid system of documentation. Use the 3D model as
a last resort. Have a FULLY detailed set of drawings. That's what the
machine shop needs.

Michael P. Locascio
Business Continuity with Creo: Learn more about it here.