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Update: 10-22-15

Now that the draftsman is slowly disappearing and the CAD engineer is taking on the draftsman's responsibilities the transition seems to be working well with the smaller companies. The engineers, I have talked to, seem to be willing to accept these new responsibilities and are even proud of the work they do, completely detailing parts. I am still wondering what kind of supervision they are under. Do they have a lead engineer guiding the design. It seems they are doing peer checking. I suppose this will be the process until they finally set up a standard checking process. There will be many more worker bee engineers replacing the draftsman thereby reducing the opportunities to move into engineering management.

Educating the New CAD Engineer - 2015

 
"I will tell you, if a part is difficult to detail,
it will be equally or more difficult to manufacture.
"

As for the large companies, they have strived to streamline engineering by adopting the unworkable MBE (Model Based Enterprise) concept. They are cutting corners on all levels. They now produce the PMI (Product Manufacturing Information) which includes the minimum of GD&T applied on different planes in 3D space. So the CAD engineers are not doing concise, complete and unambiguous engineering documentation. The completely detailed associated information documents (drawing) gives the designer a second look at the design for errors or a more efficient design before release. I will tell you, if a part is difficult to detail, it will be equally or more difficult to manufacture. Sadly, it looks like engineers are now not in charge of engineering in these large companies. This has driven engineering cost sky high and reflected in the incorrect parts and slipped schedules. Hopefully engineering management will soon wake up and start taking control back from the PLM, IT and MBD proponents.

Why MBE/MBD/PMI Will FAIL

The Argument Against Model-Based Definition


TO DRAW OR NOT TO DRAW??

 
I remember when I first got into 3D CAD in 1982. It was 3D wireframe. After working for awhile I said "boy, we will not need drawings any more".  Now, many companies are attempting to take that path.  Creating an associated information document (drawing) from a model is very easy, even when complex it only takes a few hours.  We are now getting models with only the features that need to be inspected defined. The rest are basically covered by a profile tolerance. 

This now being delivered in a format called PMI or Product Manufacturing Information, views in 3D with annotation added. This seems to be a solution requested by the PLM folks to only have to maintain one document instead of the solid model and an associated information document (drawing). Now this seems like a good way to cut design costs and get your parts manufactured.  But there are problems.




Redefining 2D/3D
 
DESIGN REVIEW      
 
We now have to introduce the "AID (Associated Information Document)" formerly fondly known as the complete engineering deliverable authority "The Drawing"

I have taken jobs to make the associated information documents (drawings) from solid models for a couple of my aerospace customers. They were delivered AIDs, with just the GD&T, a step above a PMI. I really did not make a drawing, I created a AID (Associated Information Document) or what they called at Boeing the flat file based on the 3D model. I suppose we could call them prints, but they are delivered as PDFs or do they really qualify as prints only when they hit paper? I have never created an electronic drawing in CAD, I have only created AIDs. I started in 3D CAD in 1982!! 35 years ago.

The 1980's - 3D CAD - The Beginning

The Death of the Drawing

While detailing these parts I could that there were problems with the design.  These 3D solid models are not being designed, they seemed to be created with very little thought or concern for standards by some CAD jockeys to basically fit.  As you start to detail these parts you can see that there is not much rhyme or reason to the end result. 

The AID (drawing) defines what is important and what is not important.  Now, of course, we do get some GD&T (Geometric Dimensioning and Tolerancing) in a AID (drawing) usually as a PDF.  We now have two documents that have to travel together the solid model and the AID (drawing).  Some systems like Catia have 3D annotation and other information included with the part, which is called PMI many with very little dimensional definition of the part. The new trend is to only include GD&T, having to have a CAD system to scrutinize the part. But very few programs can read the native Catia PMI file format so we may still have to have a separate AID (drawing) that goes with the model.  There by creating the same situation of making sure both pieces of data are synchronized.  Which leads to our next proble
m.

Checking, Design Review, Manufacturing and Data Extraction!


Free PMI Importer?
 
DATA VERIFICATION 
 
Now that we are attempting to use the model and not the drawing as the authorizing document, we seem to have a problem keeping track of the data. When we had a drawing we had something that was in stone.  You could look and say, "That has to be a .50 radius" and when it wasn't we had a problem.  Now we have model verification process, that compares two models. No where does it say that the models are correct, just that they are the same. 

Of course we have a problem keeping the AID (drawing) up to date.  This can be a bit time consuming, but you can check it on an AID (drawing) or check in at manufacturing after the part is made. Believe me a completely detailed AID (drawing) is much cheaper.  The AID (drawing) allows you to scrutinize and allows more eyes on the design. 

As of now I am really not sure the procedure for checking and releasing parts to manufacturing.  I am not in the design loop, but I am seeing what is being delivered to the vendors.  It is not pretty. Some of the machine shops are sending parts back, saying that they can not be built. 

I can not imagine this happening in the days I was on the board.  I remember working on the Manned Maneuvering Unit at Martin Marietta.  I would take the drawings, after they were checked by the checker for fit and function and drafting standards to all the manufacturing , materials and stress engineers for review and sign off.  At Boeing we would have design meetings with the drawings on the table.  After seeing some of the parts coming out of engineering, I can't imagine how many of these parts being released.

PTC Creo Totally Misunderstands MBD

The problem with AIDs (drawings) is that they take time to keep up to date. So no more AIDs (drawings), but the problems created without AIDs (drawings) seems to be worse.  So now we need a CAD model verification program, that does not assure correctness.


Update:

Boeing now has a Producibility Group that reviews the design after release. I am not sure what happens when they find an error. Do they send it back to the original group? I can only imagine what problems with scheduling that would cause.

Compare and Validation Programs? Band-Aids for Self Inflicted Wounds!

 PURPOSE OF AIDS (DRAWINGS) TODAY!
 
The basic purpose of engineer is to deliver concise, complete and unambiguous documentation to manufacturing.

So now we need CAD software to VERIFY the models and see the differences.  This seems to be the unexpected consequence of eliminating complete AIDs (drawings). I have come to the conclusion the elimination of AIDs (drawings) are having devastating effects on our engineering process.  So what is the purpose of the AID (drawing) in this day of "solid" models?
 
1.  The original purpose "To inspect the final part."
 
2.  Ease of design review, anyone can get a PDF and review the part design and function. To see how the assembly of the parts affect each other.  No need for CAD experience or access to the CAD program or viewer.
 
3.  Absolute authority for the part. A second check on the model.
 
4.  A review by the designer on any errors or design functionality the may have been overlooked.  A chance to see if the design can be simplified or optimized. I have had a manufacturer tell me that he has to refuse some parts for lack of manufacturability.  Even machine shops have had to refuse some part because they could not be built.
 
5.  To teach new drafters, designer and engineers how to design.  They need to have their designs scrutinized by an experienced checker, whose purpose is to not only check fit, form and function, but to impart his vast design and engineering knowledge and experience.
 
6.  A history of the design.  Years ago we used the microfiche to review designs of the past, today you have to have CAD software available to access the data.  I am not sure how we get to the data.  With a complete AID (drawing) you can recreate the part if necessary.
 
7.  I am sure there are a few more reasons, those above surely would save much time and money as these parts are being delivered to assembly and do not fit.
 
CONCLUSION
 
As I have said before, to create an AID (drawing) from a model is very easy.  Many of the CAD programs will update the AID automatically.  I suppose that is the problem, the CAD software really doesn't do a very good job updating the dimensions. But even then the problems caused by the lack of AIDs (drawings), seems to me to worth the effort.

Update:

The Death of the Draftsman or “Where has all the talent gone? 

Today, the engineer is now doing the draftsman's job. Detailing a part is a time consuming and sometimes tedious process and engineers are not interested in doing it. Plus all of the form, fit and function design, investigating and fix any problems and revising and assuring these changes are recorded and maintained. 

Engineers have not been trained to do it and it seems that this lack of desire or knowledge has led to some peculiar solutions. The engineers lack of responsibility to establish a standard engineering process has left a void to be filled by the PLM (data management) and MBE (Inspection department) to create a process that fits their needs more than what engineering needs. Leaving the CAD engineer to jump through complicated processes, not realizing that PLM and Inspection are really subject to engineering's needs. A bit like the cart before the horse.

Sadly the draftsman, who were responsible for the standard engineering process in the past are being let go and being replaced by engineers with very little knowledge of the past standard process. The engineering world is in chaos.


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Joe Brouwer
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