Comment by nickpinkston | Hacker News Reader

Comment by nickpinkston | Hacker News Reader

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There are a few problems with making new CAD, especially open source:

- CAD math is hard and severely limits contributors. Unlike many open source projects, you need a pretty big core team to make something worth using. FreeCAD/OpenCASCADE, etc. have remained hobbyist CAD, where we've seen the success of open source in software.

- Another core problem is that MechE's can't easily edit the tool they're using when they run into a bug/feature they want to work on, unlike open source software where the users can more easily be contributors.

- High switching costs: there are four big CAD companies: Dassault, Autodesk, Siemens, PTC, and once a company commits to one ecosystem, it's very hard to change. Ex: Boeing isn't putting the CAD for the 787 in OnShape - ever. There also aren't that many new huge hardware companies, meaning that folks like OnShape get SMEs, but virtually all enterprise is taken. This has essentially led to an oligopoly in mechanical CAD, and slow pace of innovation in the space. I believe CAD tools have 50x less $ investment (including big companies) than software dev tools.

- InterOp is also hard, file formats are complex/proprietary/inconsistently implemented. There are kernels like ParaSolid with import/export/conversion systems, but they're not trustworthy enough to really put the 787 into new CAD without so many bugs that you'd lose a year fixing them and likely be paranoid forever wondering if you got them all.

- Folks like nTopology have done a good job side stepping these concerns as they built a CAD tool that does a specific function (generative design) that can't be done in traditional CAD kernels and can be sold for very high value-add situations - ie designs that need very high performance from the uniquely optimized geometries that they're able to generate, and export files that play nice with regular CAD. This means Boeing can have some fancy nTopology-created parts in their planes without having to blow up their CAD/PLM systems.

CAD math is hard and severely limits contributors.

Yes. Autodesk used to have a staff geometer, and probably still does. Constructive solid geometry is hard, because you can use complex forms to cut into complex forms, and have to represent the result.

A typical exercise in a good CSG program is to model a bolt. You start with a cylinder. Then you draw and dimension a thread cross section. Then you extrude the thread cross section along a spiral, subtracting that from the cylinder, to cut the threads. Then, at the end of the bolt, you cut a chamfer by extruding a triangle around a circle and subtracting that from the bolt. The CAD program must correctly and precisely describe what happens to the thread as it is cut by the chamfer. You can zoom way in and take a close look. You might have a design constraint that the chamfered thread can never be thinner than some specified width, to avoid bits of metal flaking off as the bolt is tightened.

Most of the free CAD programs bail before they deal with problems that hard.

I'm not certain about that very last constraint (the chamfered thread not being thinner than X) but other than that, precisely what you describe is a workflow I've been following for the past couple of months in FreeCAD: not for metal threads, for plastic, printed ones, but the workflow is the same. They added helical cuts and additions in the most recent version, but even before that you could get the same effect with a helical path (so a few more steps for the same result, essentially).

Oh, good, FreeCAD is catching up. It's been a few years since I tried it.

Yeah. 0.19.2 is good, at least for the stuff I need; 0.20 is shaping up to be full of good stuff too (and hopefully won't take as long as the 0.18->0.19 cycle did). On-topic, though, if you're doing threads and gears, it gets slow quickly. It doesn't take very much for me to start needing to switch parts of the design off for the UI to stay usable because recalculations kick in that I know shouldn't be needed, but the dependency tree isn't detailed enough to filter out.

it's been able to do everything you just described for at least 5 years (with the exception of that last constraint, I think).

Not only that, but that is the workflow if you were making a custom bolt on the lathe. Machining experience is invaluable when designing mechanical parts.

>>Then you extrude the thread cross section along a spiral, subtracting that from the cylinder, to cut the threads.

Whoa! Whoa! Whoa! No Helix geometry in this office, are you trying to get us all killed?!

And the BREP math is even worse... And the implementations are pretty dirty too

Also, good to see you John :-)

This hits the nail on the head. All of the CAD kernels basically date from the 1980s. The mathematics involved in extending them is not widely taught, and while this knowledge still lives in books, it is not finding its way into minds.

Another blocker is that CAD is a relatively small part of mechanical engineering. Pretty much all software engineers use version control, but depending on subfield/company, maybe 20-50% of mechanical engineers will use CAD significantly. Mostly the design guys. The engineers in test, analysis, materials will barely touch it.

Though interestingly if you look at the numbers there are more CAD seats than MechE's, so I'm guessing a lot of other engineers, technicians, etc. are using it.

Test folks have totally different systems like LabView for data logging and analysis that don't really talk to the simulation tools, CAD, etc. - very fragmented dev tools.

I really like Bret Victor's "Seeing Spaces" vision for a more integrated hardware dev environment where it integrated software and workshop into an real-world "dev environment": http://worrydream.com/SeeingSpaces/

I can confirm that. While it's true that the MechE's at my workplace all have CAD seats, we also have a number of floating seats that get used by a variety of people. There are things you can do in the CAD tool, but not in the free "viewer" tool, so we provide CAD seats to our manufacturing engineers, who also use CAD to design things like jigs and fixtures.

I believe it actually takes a bigger and more hierarchical engineering organization to have MechE's who are not busy at the CAD terminal a lot of the time.

In addition, our machinist has a CAD seat, the machine shops that we use all have CAD seats. And while optical engineering is a small field, most OE's have CAD skills.

Peter of Edge Precision recently released a video on the CAD and CAM he does in a typical machining job[1]. The video of him turning the part[2] is also good.

Machinists running any sort of CNC machine will need both CAD & CAM seats.

[1] https://www.youtube.com/watch?v=yPtoxEgzrhE [2] https://www.youtube.com/watch?v=3-jT3HrSHjE

I had a SW license for sure when I was a stress analyst . I'd use it to look at a part to take a dimension, and maybe once a month use it to make a drawing from an existing part that would go into a report. I never modeled in it. By far the most important software for me was Excel though.

>more CAD seats than MechE's

Unless you're an EI fresh out of college, engineers probably won't spend many billable hours in CAD. Your time is too valuable, and most contract rates won't be high enough to have engineers doing drafting.

(EI = Engineer Intern, for getting your 4 years of experience for becoming a PE, which is similar to a Medical Resident for physicians.)

We have a pool of draftsman that handle most of the actual drafting, at the direction of PEs, which let's the PEs focus on actual design and other things that can be billed at higher rates.

But since CAD is still installed on the PE's computers, they're probably still counted as users, even if it's mostly for review, printing, minor redlines, etc.

Hint: Don’t let a CAD designer give you a model that is not fully resolved (i.e. constrained.)

Sometimes closed source software gets open sourced for business reasons, and backed by a big consortium, rather than being written from the ground up by hobbyists.

I wonder if big aerospace and defense companies like Boeing, and automakers, and heavy industry, and so on, might decide it's in their interests to collectively buy and open-source an existing commercial CAD package rather than risk being held hostage to the vendors that gatekeep their engineering.

Dassault Systems was spun off from the european fighter plane manufacturer with the same name. They bought up solidworks and Catia and runs as a standalone business.

https://en.wikipedia.org/wiki/Dassault_Syst%C3%A8mes

Yea, I believe most (all?) CAD systems are spin outs from industrial programs. Pierre Bezier (of the curve) was actually an automotive engineer at Renault as they were trying to better define shapes.

here's a short but fun bit with bezier unisurf system

https://www.youtube.com/watch?v=c0_a6r2JaWQ

BRL-CAD was created by the US Army Research Laboratory (then the Ballistic Research Laboratory, hence 'BRL') and was released in 1984, and became free software in 2004.

https://en.wikipedia.org/wiki/BRL-CAD

BRL-CAD is fascinating in how different it is from ux point of view. It is almost like a window to alternative universe where old fashioned UNIX and CLI won with interesting mix of graphics.

> I wonder if big aerospace and defense companies like Boeing, and automakers, and heavy industry, and so on, might decide it's in their interests to collectively buy and open-source an existing commercial CAD package rather than risk being held hostage to the vendors that gatekeep their engineering.

I doubt it. The vendor/client relationship is a lot more collaborative and symbiotic than most people would think. I'm not sure about Boeing specifically, but I do know that their competitors work very closely with their CAD vendors. Part of the contracted agreement is to have a software team on the vendor side work with the engineering team on the design side to produce essentially a custom fork of the software.

On one hand, yeah, the CAD vendor could play hardball and hold a client hostage. But on the other hand, there are only so many Boeings out there. So if you push them away, that revenue will be hard to replace.

Most likely situation is the one that's played out a few times before: acquire your vendor.

I think the companies want an independent for-profit maintaining the business because they don't trust the dynamics of open source / non-profit to actually provide good products/services. Which I think is actually a reasonable argument given the issues in my OP.

I wish the FTC, etc. tweaked how the CAD industry was handled to increase competition / decreasing switching costs, etc. This relates to them preventing people from being in their equivalent of the "app store" which Dassault has been particularly aggressive about.

I wonder how much it would cost to open source AutoCAD or Solidworks lol. Blender was only $100k.

I'm surprised the article doesn't mention Rhino/Grasshopper, considering how prevalent it is.

3D modelling !== solid modelling.

Because they are programs used to do industrial design and general aesthetic 3D modeling, they aren't CAD programs.

A b-rep is a b-rep. It's not Solidworks, but it's also not trying to be. It'll spit out a STEP file or a set of plans like anything else. Consider a second look.

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