Drafting

The systematic representation and dimensional specification of mechanical 
and architectural structures.

Preface

Every article I write starts with a history of the subject. I find that much of today's engineering seems to have no connection to the standard engineering process of the past, mostly in the larger manufacturing firms that can afford the high-end CAD systems that offer the failed PLM system. The lack of any investigative skill or worse "the assumption that they already know" has created this chaos in engineering held there by the vested interests of the CAD companies. I truly believe that the old system based on the standard drawing was more productive. But, of course, now we have computers!!!!

Design Today!

I have just received a part to modify. I work with a molder that gets parts from different customers who have already paid a fortune to a design house and the part still does not meet the customer's requirements. Even small changes are quite expensive. The design was done using Solidworks and as many of you know change is more time consuming than the original conceptual design. I do many jobs revising designs to be more manufacturable without altering the design intent. There seem to be no consideration for this part to be injection molded.

Is 3D CAD Productivity an Oxymoron?

Using Multiple 3D CAD Systems

This part was so convoluted I have decided not to take the job. Sadly, I cannot show it to you. But it has blends on top of blends on top of blends. Blends can be the enemy of direct editing. As a comment related to this subject: This part would incredibly difficult to detail (dimension).

A bit more about blends. I took a job to modify another job also done in Solidworks from the same molder but different designer. It was a very small part that fit on a fingertip. You can imagine the size. The designer used .010 weighted blends. If you don’t know what a weighted blend is, it is a blend that goes past the tangent. Mostly used in industrial design where surface smoothness is a priority as in auto bodies. Zebrastrip rendering are used to see any problem with tangency. Can you imagine using a weight blend on a .010 blend which is nothing more than break edge. But this fellow used them everywhere. The designer did not understand the basics of designing for manufacturability. Again this part would have be very difficult to detail.

"3D CAD has no limitation on design. If the designer is not trained in drafting he will probably let his imagination go, many time beyond the point where the part is easy or even possible to manufacture. Now if there is no one with experience to review his/her work it gets released."

I know these things. Why? Experience? Yes, of course, but what kind of experience

I am a draftsman. I know how to draft. From the thousands of drawing I have made, I know how to design.

Today many are pushing a thing called PMI (Product Manufacturing Information). It is where you define the part by putting limited dimensions and GD&T frames in the 3D space of a native file. It makes the 3D model the authority with a bit of tolerancing that will suffice for inspection. We will get more into PMI later in the article.

I work with many Boeing suppliers and I see parts delivered in the PMI format that have just not been thought through. You could see that these designers have very little experience. But it was not the designers fault! It was the engineering department and the system that allowed these parts to be released! We not only have inexperienced designers but we have inexperience engineering management and no effective checking in place. This has become such a big problem with Boeing they have created a “Producibility group” that reviews the PMI after engineering release.

Producibility Group?

AFTER THE ENGINEERING DOCUMENTATION HAS BEEN RELEASED?

If you don't see that this is a problem, it is time to investigate your engineering process and your lack of knowledge.

Imagine this group finding something wrong? What is their recourse? Take it back to the group? Revise the 3D model. If they are working in a Pro/e (Creo) clone, like Catia 5, this can be very time consuming. Design time is critical to a well-planned project. What happens? Slipped schedules cannot be tolerated.

ENTER DRAFTING TRAINING!!

What is the difference in the way we design today as compared to how we used to do it?

Before 3D CAD

My First 17 Years or "How did we do it without 3D CAD!"

Why do I say 3D CAD, because the electronic drawing CAD packages like Autocad are nothing but extensions of the drawing board where the product was and still is prints.

Conceptual design was done on the drafting board and called layouts.

LAYOUT – A drawing that defined the concept of the parts in the assembly. The part was fully defined but not with the standard drawing requirements.

DRAWING – The document that completely defined the parts and assemblies. Many times the design was done on the drawing itself. But other times layouts were done by designers and given to draftsmen to detail.

DETAILING – Drawing the part and adding all the required dimensions with tolerancing in a standard industry and company format to be released with all the information necessary to manufacture and inspect the part.

CHECKING – This was done by a highly experienced draftsman that would review the part drawing in relationship to the assembly to assure the parts would fit and the dimensioning, tolerancing and annotations was complete enough to not allow any ambiguities when delivered to manufacturing.

SIGNATURE BLOCK – Not only did the draftsman and checker sign off on the part, there would be a variety of specialty engineers to review the drawing for obvious errors plus the lead engineer. After these many eyes on the part for approval they would be released to the Document Control Group.

The Ten Eyes that ‘See the Part’ Before It Comes off the Bench/Lathe/CNC Machine

Yes, this was time consuming. But those draftsman, checkers and engineers know one person that sat there and just waited for errors. His name is “MURPHY” and he is omnipresent.

I hate to have to state this here, but I am afraid the many young engineers may have no idea that this fellows sits on your shoulder. We always designed with this in mind. Making sure it could be installed only one way. Nothing worse than final fabrication calls and says "It doesn't fit". Your answer "You have it backwards", hoping they think it is their oversight. You can feel them roll their eyes.

There you go, that is the way we did our design and documentation and it was called drafting.

Today's Headlines! - Engineering 101

The Age of 3D CAD

I was introduced to 3D CAD in 1982 on Computervision CADDS 4. I have never use an electronic drawing package such as Autocad. Noticed I didn’t say 2D drawings since there is no other kind of drawings. Do I hear “Wait a minute, Joe, I do lots of 2D drawings”. No, you don’t. I will get into that later.

Today we do not need draftsman. We design the 3D part directly. There is no need to do drafting. So why would we need draftsman? I must say this is true. But as we got rid of the draftsman someone was going to have to take their responsibility. Which was to create, check, release and maintain the correct engineering documentation.

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

Engineering's only purpose is to deliver concise, complete
and unambiguous documentation to manufacturing.

So now the engineer must know how to do the documentation. No, no, no engineers did not do drafting in the past. That is why we had “draftsman”. But the documentation still must be complete, correct and unambiguous.

This transition was never officially put in place. The draftsmen were being let go by attrition and all of that experienced disappeared. The young engineers coming out of college were now not prepared to provide the documentation. They were learning it on the job. Of course, they did not have the basics and did not understand why they were doing most thing and started doing it by a rote process.

The Millennial 3D MCAD Engineer

Educating the New 3D CAD Engineer - 2015

Now for an explanation why we do not do 2D drawings.

Today all 3D CAD systems have a documentation modules. Some mistakenly call them the drawing module. These modules allow you do place different “Instances” or “Views” of the part. You can also take section cuts or create details of different parts or features. They are designed around “drafting standards’ and when done and printed you cannot tell the difference between a drawing and a hmm what do we call this documentation? At Boeing they called it the flat file, I have coined a different term the AID (Associated Information Document)

So, document creation is much different than before 3D CAD.

It is much, much easier all you do is attach dimensions to existing graphics.

Even though we are not creating drawings, are we still doing drafting?

I know, I know, it takes forever for me to get to the subject. But there is so much history that created the situation and why I am writing this article.

Drafting is the art of creating mechanical drawings. But it is much more that that. You have to know many things about the part. You need to know the form, fit and function of the part, how it relates to the mating parts and how to clearly present it to manufacturing.

No we don’t create drawings but we do create the same information in the form of AIDs and deliver them with the 3D model as a PDF.

More on the PMI

The industry in trying to make the Pro/e Clones, Creo, NX, Soldworks, Solid Edge and Inventor data more manageable, devised a diabolical format called the PMI,

PMI (Product Manufacturing Information)

AID (Associated Information Document)

PMI (Product Manufacturing Information) vs AID (Associated Information Document)

In the beginning the 3D CAD programs above have separate associated AIDs (drawing files). At that time the AIDs were being delivered a paper prints. They quickly became a nightmare to manage with PLM. So, some power said "let’s create the PMI we can have all of the dimensional definition and annotation in one file." We will create MBE (Model Based Enterprise) this was where the model became the part authority. There are so many things wrong with this.

Why MBE/MBD/PMI Will FAIL

The biggest problem with the PMI it short cuts the design process.

Why the new 3D CAD engineer needs to learn drafting?

If you have a difficulty detailing a part,
manufacturing will also have difficulty making the part!

I have seen part after part that has not been scrutinized for manufacturability. Many in the industry tout DFM (Design for Manufacturability). It is strange to an experienced design draftsman why this acronym even exists? DFM was the standard operating procedure for designers and draftsman in the past. I mean, think it through. What is the level of experience to even have this be a consideration?

Who would design for non-manufacturability? You just have to shake your head. But I have seen many parts that were very costly. A few parts could not even be made. So I guess this is a problem in the industry today and someone has to tell the new 3D CAD engineer this.

I push for completely detailed AID’s. It gives the designer a second look at the design for errors or a better design. The AID gives a format that allows easy review. It can be printed and passed around the different groups for input. Easy to check and mark up. Much better than giving them a file to review on a display.

Here is and ancient example of a detailed assembly.

Here is the converted 3D CAD assembly presented as an AID sans dimensions. This AID was set up in minutes. Detailing would take an hour or two. But with the documentation advancements of today we could easily produce much better presentations than trying to duplicate a century old standard. But this would take a complete knowledge of basics of that standard.

But to completely correctly detail a part it takes drafting knowledge and skill. This is where I believe we need to teach the 3D CAD engineer to make actual manual drawings. I would probably do it on the board with the different drafting tools. It will give them a good hands on feeling of the basics. It take much less of a learning curve than training on an electronic drawing package such as Autocad. No, of course, we do not train to the level of the past just a good understanding of the process. When they create the drawing with the orthographic, section and detail views, they will be able to read a drawing. Reading a drawing is the ability to see the part in 3D by reviewing the drawing.

It wouldn’t have to be a long class one good semester. Each engineer would understand how things are laid out. Remember this is not only for creating documentation for manufacturing, but also to understand the thoroughness required for good design engineering. Today the 3D CAD engineers are doing peer checking. Which in many cases can be the blind leading the blind? Every large engineering group needs a dedicated checker. Who is responsible for the correctness and completeness of the parts. To consider checking as nothing but an overview for obvious errors is a recipe for disaster in incorrect parts and slipped schedules. It is always the small error that can cause disaster.

We would need to follow with a class of 3D CAD design. After learning the basics of 3D CAD and with the ability to read a drawing, they can now start creating parts from sample drawings. Not only does this give the student different challenges with the CAD system, but exposes them how parts are designed and defined. Thereby giving the student a hands-on introduction to 3D CAD design and engineering with an emphasis on KISS (Keep It Simple Stupid)

Engineering Ignorance Defined IV
Defining the “2D Drawing” 
Redundant? Of course!
Educating the PLM Guru!

I suggest any school adopt Onshape. Not that it is the best 3D CAD system, but it can easily be used to create parts from drawings. It is free and resides on the cloud, so they can work on it anywhere. PC or Apple.

I am sure this would go hand in hand with the basic understanding of classic engineering. With the 3D CAD they can be introduce to all of the CAE with simulation functionality.

So, there you go. We now have well rounded 3D CAD engineer ready to relate to a real engineering environment and ready to go to work.

Update 4-3-18

As I review this article I realize there is little or no drafting or documentation training available today for the 3D CAD engineer or AIDs from models. It has to be folded into the college courses. If not, the engineer is delivered to a strange world of dimensions, annotation, form, fit and function design and even a new CAD system. They have to learn this before they can be effective. Sadly, this learning curve is fraught with many pitfalls causing errors and slipped schedule depending on the haphazard way it is introduced.

If you would like discuss options about setting up a functional curriculum on this subject in your company or school, please give us a call.