Pet Peeves: Sketches Stuck in 2D Thinking

This is a post I could have written 10 years ago, or even 20 years ago, to be honest. This complaint becomes smaller and smaller, but the fact that it still exists at all makes it a bigger and bigger deal. I don’t write about this stuff often because I think it is just too obvious to warrant it, but problems like this persist, and not just with old guys like me, or guys even older than me, but with young kids right out of school. So someone is going out of their way to teach them some really, really counter-productive thinking.

Here’s the latest problem that set me off. You may recognize this from the SW forum. First, notice that this is an educational part, so it’s coming from a college or high school somewhere. I know there are probably a lot of students who get their hands on the software without any instruction, but…

Second, the student wanted a left and right handed part, so they mirrored the entire sketch. To me, this shows that this person is thinking completely in 2D.

Third is something you can’t see – lots of overlap and extra sketch items, which just means accuracy, CAD hygiene, and efficiency really don’t matter.

Fourth, again something you can’t see. They must have been filled with the dogma about fully defined sketches, because they added a lot of dimensions to make the sketch fully defined. The problem is that there are no tangencies or sketch relations. Everything is placed with dimensions. So hooray, it’s fully defined. This is what happens when you let one idea dominate too much. If this is what fully defined sketches mean, I call them a scourge.

Somebody has taken the time to teach this kid about fully defined sketches and symmetry – both certainly considered best practice – but hasn’t taken the time to teach them WHY. WHY are we mirroring things? WHY are sketches fully defined? Without understanding WHY we follow best practice, these rules become counter-productive.

The way this is done, as I said earlier, it’s clear there’s just 2D thinking going on here. You’d think that by the awesome year of 2020, most of the dyed-in-the-wool 2D users would have succumbed to pressure, retired, been promoted into irrelevance, or one way or another just stopped annoying the rest of us. But they haven’t. Or maybe schools continue to churn out people who have this poisoned 2D frame of mind. All you have to do is hang out on the SW Forums a little bit, and you run into this frequently. I don’t often publicly shame people for really bad ideas, but this one just sent me over the top today. I won’t include any names or the names of any institutions to protect the guilty. I’m not even sure if all of this is the fault of the student or the teacher.

Even some of the other solutions posted for this problem included things like the use of contours, which in my view, just perpetuate bad habits. The use of contours is valid when it’s an intended part of your modeling plan, but not when it’s just a crutch for accidental ignorance. Don’t teach the use of contours to people who don’t know the difference between a 2D drawing and a sketch for a 3D feature.

In case you’re still reading, the problems with this part get even better. Notice all the planes and the 4 Boundary surfaces. Given that the kid is going to eventually want to do a trim with the terrible sketch, 3 of the boundary surfaces could be created as a single extrude, and the remaining one could be a revolve.

So someone has taught this person surfacing? And yet they don’t know about simple extrude/revolve features or mirrored parts/bodies or even how to sketch things properly?

Really, were we this stupid 25 years ago? Maybe we were. Or maybe I was anyway.

In the end, this student’s question to the SW forum was because the trim feature gave him an error. The error message, it turns out gives you a clue, but this kid was just into making things as complicatedly wrong as possible. My solution was to fix the sketch, and someone else suggested the contour crutch. Must be a graduate student there.

This kind of thing drives me crazy. Students need to first understand the difference between a sketch in 3D CAD and a view in 2D CAD. This particular part shows that the problem is at least in part because of the order of the information kids are getting. Looks like they’re reading the back of the book first, and know a whole lot more HOW than WHY.

Who’s at fault here? The teacher or the student?