Sunday, July 5, 2015

CNC Routing a ZBrush Sculpt

I made use of the Roland 4-axis router at the Penny W. Stamps School of Art & Design to make a walnut version of a portrait sculpture I created in ZBrush.

Here's the ZBrush sculpt (more details on its creation are available here). It has been decimated down to about 400,000 polygons to make is manageable for RhinoCAM (the software used to drive the router).

Mounted in the bed of the router is the block of walnut. It is about 3" x 4.5" x 8". It is clamped by the 4th axis at one end and by the tail-stock at the other end.

Roughing begins using a 3/8" diameter 2 flute end mill. This is pretty rough yet only 0.05" was left for the finishing pass.

The 4th axis of the router is rotated to the other side and roughing continues.

The first finish pass is done using a 1/8" ball end mill. It is cutting from the face to the back of the head.

Here's the final finish pass using a 1/16" diameter ball end bit. Only in the smallest crevices was any material removed.

Here's the part after the router has finished: 

Here's are a few clips of the routing process. This is shown at the actual speed of the router:

After routing there's still a need for hand work. Some sections of tear out need to be sanded/scraped out (above the left eye, at the base of the neck). The back of the ears had some very strange tool marks that needed to be filled (I used a mix of sawdust and polyurethane). And the area where the block was attached needed to be carved away and finished to match the curvature of the head and texture of the hair.

With some finish and a base:

Newer Work

A more recent small portrait sculpture, done on my own router, is discussed here.


  1. Great job, congrats! How long it takes on the router?

  2. Thanks. It took less than an hour to cut on the router. And about 1/2 hour to set it up for cutting (program the toolpaths).

  3. fantastic job !! which cam software did you use?

  4. Hello, can you tell me if cnc can handle the details from zbrush? from what I can see, the bust that you've made isn't detailed enough. I wonder how much detail can a cnc handle? For example, can it make skin details? Thanks!

    1. Skin details? No. ZBrush can have such high polygon counts the detail is incredible. On a CNC the level of detail is set by the smallest diameter of the tool you use. They make them very small - but the tool has to go back and forth across the surface at a very small step over. Not really practical in terms of time, especially for a material like wood which can only accept so much detail. Of course, if you have a large sculpture, and a great deal of time, you can let the machine run for many, many hours. And if you picked a material that can accept tiny details - for example boxwood, you could get close. But skin detail, I don't think so. I'd say print it on a very high resolution wax printer then cast it.