The Prusa method of p3D-printing holes – who knows more?

[VersabossParticipant @versaboss]

In MEW 342, Roger Froud wrote an article about a device for rotating paint drums. Although I’m not actually interested in that, I skimmed it over because the gadget uses 3D-printed parts. But I was quite surprised about what I found in the last paragraph. Mr. Froud wrote “…the M3 holes use a technique pioneered by Prusa where a hole can be created in an overhanging part. This is done by first printing a slot, followed by a square, then an octagon and finally the circle.”

Even after reading that several times, I still don’t understand it. Usually, holes are defined in the drawing of the part. As the printing is done layer after layer, I cannot see how these 4 different geometric elements are arranged in the 3-dimensional space.

I spent the better part of half an hour to find the answer in the Prusa website, but had no success.

I would be very pleased if someone here can solve that for me (or maybe Mr. Froud is listening here?).

Kind regards,

Hans

[JasonBModerator @jasonb]

Roger can be found on MECH forum, more of his paint mixer in his speedy valve gear thread.

I suspect it is to do with supporting the layers on the overhanging part. As printed I think the counterbore was below the hole so the slicer software uses those steps to bridge across the counterbore

[JasonBModerator @jasonb]

this should explain it, much as I thought

[VersabossParticipant @versaboss]

Many thanks Jason, great how you solved that problem. Now I watched that video three times and made some notes. I think that I now understand the most of it.
I will see (maybe tomorrow) how I can recreate that example in Onshape.

Kind regards,
Hans

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