Minimum Wall Thickness

I submitted my designs to Shapeways, and waited with baited breath for their realization in plastic. By the tenth day, I wanted to race home at lunch time to check the mail box. That day passed, as did the next and a few more; finally I got an email from Shapeways.

Apparently they do one last manual check before submitting the model to print, and in this manual check they found that I had violated the minimum wall thickness. Now, I knew I was violating this rule, but with a thorough read of their site, it seemed like I could do so as long as I kept the distances minimal. The way I read it, I should be able to have a short span of something finer than 1 mm diameter. However, this turns out to be false: you can have something that ends finer than 1 mm, like a knife edge, but you can’t have a barbell shape with a fine handle.

So much for window mullions, or printing ladders, at least for now. I’ve redesigned the passenger car without any window frames, and I guess I’ll get those laser cut in .015 material. The more challenging redesign was the truck, however. For this, I’ve made all the various straps in the double arch bar include a 0.7 mm (minimum wall thickness for white strong flexible) diameter rod that tapers to the front and to the back. It doesn’t look too much worse than the draft angle on some of the older injection molded arch bar trucks, at least on screen.

I’m going to wait a week before I submit the job so it doesn’t arrive when I’m on holidays. Hopefully this time, it passes muster and I actually get some plastic!

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