This is encouraging! I’ve spent a lot of time thinking about how to solve the challenges of printing the window crank on my Prusa MK3s 3D printer. Solving for the printing issues with fit and print quality. 

What are the issues to solve you ask?

  • Tolerances – The surfaces that print on support material tend to be rough. Thus need to add in a bit of offset to allow for that. 
  • Threaded VW Cap. The cap that goes over the bolt that holds the crank to the door. It was difficult to remove the way I had it designed as a bayonet clip. As a threaded cap, as you turn it pushes out of the crank making it much easier to remove and easier to print. 
  • Knob snap assembly- In my first prototype that broke. I had the knob tongue and groove friction fit and glue. This worked fine but required glue and I’m not confident PETG glues well. Plus I hate glue,  super glue always comes in those dumb small tubes. After 3 tries I got a snap to work quite well. 
  • Fit to Door- After printing this crank many many times I took another look at the very small teeth that interface with the gear that comes out of the door. Turns out I was off by 1mm. This is why in the past those teeth pushed into the plastic and made it hard to install. Now the fit is perfect. We will see how well it survives in practice.

    So this is pretty exciting for me. I feel as if I’m very close to having the crank designed in a way that makes it manufacturable as a 3D printed product. There are still some streamlining of support structure that needs to happen. As far as print quality and functionality it is there.

This is frustrating, I really want to print these cranks in ABS Plastic (better heat resistance). No matter what I try I can’t get a clean print out of ABS.
I tried PETG the other day and it came out super clean! No warping not melting. I could make them out of PETG, they just have slightly less ability to resist heat (survive a hot car). Although as you can see in the picture below the PETG seems to be stronger, After a very unscientific stress test the ABS crank fail fairly easily. (See ABS broken on the right in the picture below)

That said I’m continuing to run tests with PETG. The nest test look at printing the knob and the crank as 1 part leaving space for the knob to rotate freely without having to split it into two parts.

Hey hey, I hope you are well,
New news, I bought a 3D printer a few months ago and I built an enclosure so I could print a larger range of materials. I didn’t post that project as it was kind of a bungling nightmare. (yes that is a Vanagon poster)

The first project is a housing for a device John ShoeMan (SP?) and I have been working on. This is an IoT clock that can tell you if your NJT transit train is running on time every morning. It was a great idea till the pandemic hit. Never the less I had a housing designed for it so that was the print first test.
I’ve been printing the development of the housing in ABS. ABS is the plastic I’ve printed with my entires design career and so it was natural that I would continue with this on my personal machine. ABS is great for it’s heat resistance. So the things I’ve created for the van need to be printed in ABS. This clock does not. Unfortunately, I had the ABS white material so its been all I could use. It has not gone well.

I’ve tried 2 different strategies for the design. A single housing with foot and screen. I’ve also tried it as 2 halves with a foot. See pic above.
Sadly I have given up on this design for the moment. I think ABS isn’t the right material for this. I want to try a white PETG. Stay tuned.

Vanagon Window Crank

Left to right is higher bed temp…. Too high melts things.

So as you know I’ve printed this window crank out in the past on my work machine and it came out well and worked well.
That said I hoped it might be a good candidate for my home machine. Sadly I’m running into a lot of similar issues with the crank that I did with the clock. It all comes down to heat. Both the heat of the bead and the heat of the nozzle. That also affects the support material that then tends to mark up the part with melted pockmarks. The latest one I’ve done turned out decent but there is much more to be done before I would feel comfortable using them or offering them to anyone.

Wish me luck! I hope to keep posting about this as this is perfect pandemic DIY stuff.