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6 Jan 2020

A hiatus from my last entry. Christmas break was hectic! Some project work done, but pretty disjointed.

I've done a number of 3D prints now on my Geeetech A10. I've had some good success, including creating my own models in Blender. I've started to have some problems recently, though, with adhesion and contraction (I think, i.e. lower layers shrinking and pulling off from the heat bed). It's possible my bed is not levelled properly (though I've made multiple attempts at this) or the glass plate is slightly warped.

I was trying to bring an SVG into Blender and extrude it, which was working fine, but then I was having trouble when trying to "flare" it out at the bottom, sort of like a rubber stamp. In Adobe Illustrator this would be called "offset path". In technical/mechanical design, I think this is called "drafted sides" or tapering, or maybe offset or polygon buffering or envelope curve or something else. I've tried many methods in Blender which all tend to result in the same problem: Overlapping or extreme projections don't merge or collapse automatically, leading to bad geometry or "mitres" that stick out.

I'm looking into some other ideas, including:

  • Doing the "offset" in Illustrator and then exporting "bottom" and "top" curves, so that maybe one can be overlaid on the other in Blender, and then pulled up to create the tapering geometry in between. Note that the key here is that each needs different geometry, rather than simply equivalent "tweaked" geometry.
  • Instead of Illustrator, what about Clipper? I think it has other implementations, too.
  • Minkowski addition which basically means sweeping one surface completely over another surface, to create a new solid.
  • Dilation (related to Minkowski addition) and its complement, erosion.
  • OpenSCAD might be worth a look, including using it to do an offset before importing into Blender.
  • Do it as a height map? i.e. put a raster version of the image into one layer in Photoshop, then on an underlying layer blur it. There are probably various ways, then, that the profile can be controlled. See also: this
  • This might be the best information, technically: https://stackoverflow.com/questions/1109536/an-algorithm-for-inflating-deflating-offsetting-buffering-polygons
  • Offset script for Blender, e.g. this?

See also: