Intro: CAD Software and Me
Here are some of my thoughts on CAD. I’m going to start with a story that pretty accurately characterizes all of my experience with 3D software to date…
It was in Regina, I think I was in grade seven because we were still at Dunn place. We had that Atari ST computer which was great because it was miles ahead of the old Coleco Adam and even the ubiquitous Commodore 64. I discovered it had a 3D drawing program! I delved into it and figured out how to make the various shapes, then proceeded to design a futuristic tank. I spent about five or six hours going into all kinds of detail, with separate tracks, body, turret, antennas, the works. The program had a feature to do keyframe animation so I had the tank drive forward, stop, turn the turret, shoot, and then blow up into all of its various pieces. The program could also render the animation with colors and save it as a video that you could play back.
I set it up to animate, it rendered half a screen, then it crashed and I lost everything. That pretty much sums it up.
When it works, CAD has two main attributes:
- It is very precise.
- It has a great memory.
How those help you depends on how you use it.
I’m going to go way up for a birds-eye view of CAD and what it is generally used for, just so we can use some of the same terms. In a nutshell, I would say CAD is used in three main ways: Design, Documentation, and Production, where Design includes things like Sketching (how will it look?) and Validation (will it fit?), Documentation includes Drafting (blueprints) and Presentation (pretty pictures), and Production includes making things, or output to control machinery that actually makes things. I’m going to start at production and work backwards, cause that’s easiest. 
#3) Production.
The majority of our production at my work is still manual, meaning
(obviously) that our guys interpret the drawings and use their hands to put things in the right place. Unless you have some tools I don’t know about, that’s the way you’ll be doing things. Of course, you’ll use jigs and fixtures, rulers and tape measure, guides, braces, templates, et cetera to make sure that things are as close to where you want them to be as possible, but in the end, it is still you who interprets your CAD data and translates that to a physical product. For non-manual examples of CAD used in production: We get some stuff laser cut out of steel plate for some of our equipment, and for those parts I send CAD profiles to the vendors and they use those profiles to program their machines. We also get some small parts CNC machined when we have large enough runs to make it economical, or where parts are too small for us to do accurately (Our machinists are used to BIG stuff). For those parts, I export a 3D model which the vendor uses to generate toolpaths for their mills.
This is one of only two areas where Precision of your CAD software comes into play. If a laser cutter is directly controlled by your CAD data, then it must be precise. Otherwise, as long as you can interpret it in such a way that you successfully build what you intend, it’s usually close enough. Interpretation of a drawing falls under the big umbrella of ‘communication’, and that leads us to:
#2) Documentation
Documentation is probably where I am able to use CAD most effectively. The majority of my work is communicating design intent and [proposed] method of manufacture to the people who actually build things. Me and the guys in the shop both speak a language called “mechanical blueprint” (or ASME Y14.5, to be specific) and that allows me, for the most part, to clearly describe how things are supposed to be built. Nothing is perfect, so it is supplemented by color printouts of the 3D models from views I see on my monitor, and sometimes verbal explanation. The work I do is heavily weighted towards the technical side of communication (as opposed to aesthetic), here is a little
graph:
Drafting . . . . . . . . . . . Presentation
< --|--My Work----|-------------->
(More technical) . . . . . .(More artistic)
I’d like to do more fancy 3D renderings at work but since my boss doesn’t see it supporting our core business, I don’t spend much time on it. (I don’t do much at home because I haven’t found many programs where I don’t hate their guts after a few hours and wish bad things to happen to the programmers - see story at the beginning for reference.) When you start to get into making pretty pictures, you’re really blurring the lines a bit… Skipping outside the bounds of what I would call “CAD”. However, when your goal is communication, if a picture is worth a thousand words, a color 3D exploded assembly view of a machine might be worth a thousand dollars (by preventing misteaks.)
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Throughout a project I accumulate a stack of drawings for all of the parts and assemblies that are used to make our products and machinery. The drawings are directly derived from the 3D models that I make at earlier stages of the project (more on that later). That stack of drawings serves several purposes relating to documentation: “What are we going to build next?” “What DID we build?” “Ooooops… What were we supposed to build?” (and to the customer:) “This project has 300 drawings! That’s why you should send us all that money for engineering.”
A guy that my boss knows runs a small high-end semi-portable sawmill. He came into the office last year sometime and wanted to know how much it would be to draw up a set of plans to build another of the sawmill that he purchased, with some modifications. My boss set me on the task of estimating it, so I took a bunch of pictures, took notes on how it worked, and notes on the mods he wanted. I spent a few hours going through it all and came up with an estimate of about ten weeks to complete the entire thing - at a cost of around $30k for the time. The guy got angry. “I can make the thing myself from scratch for less than that!” That was probably true, and he didn’t much care that with that set of plans, he could make 100 of them that were all exactly the same, and have them built absolutely anywhere - because the entire machine would be documented, down to the last bolt.
This is where attribute #2 shows up: CAD has a great memory. With our 3D software, I can go back to a project from seven years ago and tell you within about a minute how many spray nozzles it used, what size they were, and whether they were brass or stainless. (Of course, if you never build two of the same thing, this may not be as important.)
‘Presentation’ finds its way into sales for a lot of companies… Most of our customers don’t care how the stuff looks, as long as it works - and that’s mostly a reputation thing. Good reputation is built on how closely our equipment matches what they want and need, and that leads to:
#1. Design
Design is a funny thing. Most of the time I would describe it as “the active struggle to find a tenuous balance between different competing requirements.” Sometimes the design process has a mind of its own, and it’s usually uncooperative, won’t go where you tell it to, and gets into places where it shouldn’t be. Sometimes it’s like whack-a-mole, sometimes it’s like pushing string, and other times it is much like “herding cats“**.
The process of design itself is hard to nail down accurately - though not for lack of people who try. It’s true that there are systems that can help you make better decisions during the design process, but anyone that tells you it can be completely regimented is ignoring inspiration, or those “ah-ha!” moments where new pieces materialize or old pieces click into place.
Among competing design requirements, one that holds veto over the others is Manufacturability (can it actually be built as-drawn?). It is just as easy in CAD as it is on paper to draw something that is simply impossible to make. Other requirements are: Cost. Functionality. Dimensions and Portability (can we physically get it from our shop to where it needs to go, and once it’s there, do they need to move it? Is there a door it needs to fit through, or a bridge on the highway it needs to fit under?) Ease of use. Ease of manufacture. Aesthetic. These all tug at each other and need to be settled in rough equilibrium or a design just won’t ‘feel right’. (Though you might be surprised how often fuctionality gets bumped in lieu of cost.)
I have been looking for years for CAD software that is also a good design tool, that really helps me to balance all those requirements, and gives me the flexibility to quickly change the design to satisfy them. So far the result of my search is that at my work, close to 90% of the design we do is on ruled graph paper, with a clicky pencil. (A lot of it goes on sticky notes too. ;)) We work in pairs or in a group, and trade ideas by sketching. When we hit something we like, we sometimes photocopy, or I will take some time and block it out in Solid Edge, then print a line drawing of the results and we’ll continue sketching over top of that.
‘Blocking it out’ in CAD is also what I would call Validation. Here’s how Validation often happens: My boss will walk in on a ‘design session’ and propose some idea. I usually try to hold a picture in my head of how things will look as we’re designing, and in this case I can see it won’t work - but I know from experience that just saying so doesn’t have any effect. I fire up Solid Edge, draw a couple boxes or cylinders, and rotate the view. “You want us to do what?”, I ask. “Oh.”, says my boss.
Much of the time spent on a project is one very long validation session - taking all of the design criteria, notes, sketches, and ideas and building them into a complete 3D model of the entire project. This is the second of two areas where Precision is important. For example, we did a project a couple years ago where we built all of the main parts but didn’t assemble any of them at our shop - we sent the entire thing to the customer’s site in pieces, and they put it together with zero problems fitting parts. That level of precision at that scale of project is near impossible if you have to keep track of all the details in your head alone. (This process of proving things will fit also blurs the line between design and documentation.)
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Flexibility is important in the design process, because of the way the requirements pull against each other. Unfortunately, Precision and Flexibility are mutually exclusive. The problem with the Validation part of design is that with each variable that you nail down - be it dimension, area, weight, or a host of others that you can manipulate in a CAD program - you are adding precision, and removing flexibility.
Design using software tools is hard because the program and the computer keep getting in the way, and interrupting the ‘flow’. In AutoCAD for example, probably 20% of what you do is about drafting (or drawing), and the remainder is split between things like learning how computers work, dealing with the limitations of computers, and working around historical short-sightedness of software developers. (Can’t blame them, really… It’s impossible to predict the future, and good user interface design is hard.)
If design is about finding balance between often-opposing requirements, then the quicker you can prove that you have balance, the faster you validate your design. BUT! The design mostly doesn’t happen in the CAD software. It ends up happening in the grey matter. Translating it ‘in the best way’ to a medium that you can share is where the problem lies. For example, sketching on paper is fast but inaccurate, where sketching in CAD is downright painful, and it is painful exactly because of CAD’s fantastic precision. Even after ten years of using AutoCAD, I would rather sketch on paper to illustrate a design concept. The word illustrate hilights the difference. Ask me to draw an idea for a feed hopper and I’ll pick up the pencil. But - ask me to draw ten of them, each with a specific volume, and I’ll fire up the CAD software - the pain of drawing the first one makes up for itself by saving time on the next nine. Add in some fancy stuff like layers, colors, blocks, “bills of material” and things like that, and CAD starts to become more attractive the bigger and more complicated your project is.
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What’s Next
Next time I’ll talk a little more specifically about the various programs I’ve used, and how they fit into these three main areas in my experience - and the scores I’d give them in specific areas where I find each of them lacking.
If you’re thinking of using CAD for a project, it is probably a good idea to be able to describe in detail how you envision using CAD to help you work. In your head, do you see spinny 3D things? Do you see huge lists of numbers? Something in between? CAD is precise, and it has a great memory - how do those benefit you?
There is an important word, ‘parametric’, which is a key differentiator for functionality among CAD programs. I’ll go into more detail on it later as well.
Note 1: Some images have been altered to protect the obviously guilty…
Note 2: As a funny aside, several years ago, EDS (the company who made that ‘herding cats’ advertisement) purchased Unigraphics Solutions, the company that makes Solid Edge, and tried to bring it under their brand. They screwed it up for around two years with lousy marketing that resulted in even worse sales, then sold the company off again. It’s in much better hands now.
