I have recently been looking for a simple design with which to start learning Autodesk Fusion 360, and to try out Shapeways‘ Porcelain Ceramic material.

One project I’ve been contemplating for some time is something to help balance shampoo bottles upside-down when they’re near empty. The solution—a simple doughnut-like hollow cylinder—seemed like a good candidate:

First model in Fusion 360

The idea is that you rest the bottle atop the ceramic base most of the time and, when you eventually need to stand it upside-down, you invert it and place the lid in the central hole: I’m tentatively calling it 'Upside’.

The base modelling is fairly simple: drawing and extruding two concentric circles, then filleting the resulting edges. I parametrised the dimensions, so it’s easier to adapt it to different bottles.

What makes things a little interesting is that tolerances for porcelain are large: Shapeways states, ‘± 3% shrinkage + 0.2-1.0 mm of glaze’. Since this particular design works if things are a little too big, but fails entirely if it’s too small (and the lid of the bottle doesn’t fit inside the central hole), I simply scaled the whole model by a factor of 1.03.

Original dimensions

Overall things shrank a little more than I expected as I forgot to account for the glaze. Including this, it does indeed look like roughly 3% shrinkage:

  • inner diameter, from 30.90 mm to 29.25 mm
  • outer diameter, from 82.40 mm to 80.76 mm
  • height, from 30.90 mm to 30.35 mm

Given the 3D printed nature of the design, I had expected it to be fairly precise. Instead, the print has a somewhat handmade, almost wabi-sabi look about it. That was disappointing at first, but I’m coming to like the result. The base is un-glazed, and has a fairly rough, abrasive texture, and might perhaps benefit from a piece of cork.

You can download the original model here, from Thingiverse, or from GitHub.