Machined Aluminum Utah Teapot by Gershon Elber

In this test case, the iconic Utah teapot model was used as a benchmark shape for research into algorithms for automatically computing 3D machining toolpaths for objects

represented by NURBS solid models with curved surfaces, concavities, and hollows.

Technical Overview
The body of the teapot, including spout and handle, was sculpted from a solid block of aluminum in the Advanced Manufacturing Lab of the College of Engineering of the University of Utah.

The Cincinatti Milacron T-500 5-axis horizontal milling center used to make this object has a rapidly spinning cutter, shaped like a rounded drill bit in this case, cylindrical with a hemispherical end, and cutting teeth on both. The machine holds a block of material clamped to a table with three linear and two rotational axes, all under precise computer control.

The object of the computation is to generate a 5-axis toolpath that sweeps the cutter through the negative volume around the desired object.

The trick is not cutting into the surface of the desired shape, tilting the milling cutter around its ball end to avoid projections such as the spout and handle of the teapot. A larger-diameter roughing cutter is used to remove the bulk of the material first.

The lid of the teapot was separately turned on a lathe, specifically a Cincinnati Milacron MillTurn turning center with a 12-tool turret. In a lathe, the cylindrical block of aluminum raw material is spun rapidly, as a sharp cutter moves into and along the axis of rotation.

The Bézier-curve profile of the Utah teapot model is offset and used directly for the final lathe finishing-tool path. The most interesting algorithmic bit is the part that leads up to that, which efficiently roughs out the bulk of the raw material as aluminum chips.

Ann Torrence
University of Utah School of Computing
Torrence (at)