I wonder how the rigidity holds up over time. Working at a robotics company, the mechanical engineers had to overcome quite some challenges to find a compromise between, precision, speed and repeatability.
And that was with a metal frame.
If you're talking something like carbon fiber reinforced nylon, it's probably a bit better. If you move to something like Markforged's fiber-strand reinforcement it'd get even better. And then there are the SLA/SLS solutions, like Formlabs "rigid" material, which I think would be a very interesting material to try for this.
I think at the end of the day, you need to keep in mind this is an educational robot, not an industrial robot. If it can maintain 0.050" of repeatability, that would probably be good enough for a lot of use cases (but of course, that depends on your use case.)
Maybe this is a project where I can put the random collection of components to use which lying around in my basement.
Not exactly to spec but that's the spirit I think.
Quote from the manual:
> Screws are in this example M3 screws and holes are undersized to 2.7-2.8mm that means that when we screw in the screws we are tapping holes in 3D printed parts.
> There are multiple benefits to this:
> ● Connection is strongest compared to tapping holes with a tap or using brass inserts
> ● It is simple and fast
> ● No need to prepare the hole, it can be printed undersized
> Cons are that you can’t disassemble it a lot of times. In case you feel screws slipping in the hole. Put some super glue in the hole and wait for it to cure. After that re tap the hole.
If you have something you want to reassemble frequently, use inserts. If you're putting it together once and intend to use it that way for a long time, threadforming works fine.
Did they have any moving parts? Did they experience continuous vibrations and frequent mechanical shocks? For DIY robot arms, fasteners are very often the issue #1, if arms operated more than just for demo purposes.
You would be surprised how many screws will go lose after a a thousand of hours of operation, even in this case.
What I'm saying to you is to make sure something is an actual problem before saying it is. In this case, the fact that the screws are used as self tapping, the screws themselves create the threads, likely combats this. Like a nylock nut.
This isn't what I would do for say, a surgical robotics system, but that's not what this is.
If given the choice of having the design as is, or making it more expensive, more difficult to assemble, and less accessible. I'd choose it as it is.
There are always tradeoffs. I believe the designer made the right ones here.
Before saying they didn't, maybe build one.