Friday, December 25, 2015

First Projects on New CNC Router

After building my CNC router and getting things tuned up I've had some time to finish a few projects.

Engraved Signs

For holiday gifts I made a few name plates for friends and family. Two of the signs are for some of my fellow sculptors at West Huron SculptorsRobert Ongaro and Yuni Aaron. I put some Golden Oak stain into the carved areas to heighten the contrast.

The latest updated of Autodesk 360 Fusion included an Engrave toolpath. It's quite simple to use - select the text and the tool and Fusion does the rest - moving the tool up and down so the sides of the cutter align with the edges of the text.

In the image below the lower blue line is the path of the tool tip. You can see it moves deeper in the wider areas and retracts at the ends of strokes.

The fonts I choose to test out were these:
I had no trouble cutting any of them.

One side effect of being a woodworker for many years is you have LOTS of wood scraps. Off cuts and small pieces accumulate over time so it's great to have little projects like this to make use of the wood. I used some left over tiger maple, quartersawn white oak, and walnut to make these.

The tool for this work is a 60 degree sign making bit. It uses a single solid carbide inset knife. I got this one from Tools Today. This insert knife actually came loose during my first test cuts. I didn't notice until it was done with one piece. The wild chattering which was taking place chipped the tip and the edge. I'm glad it didn't come fully loose - yikes. Anyway, it still works well enough to produce all the signs above. It does need to be replaced though.

The spindle speed used was 12000 RPM. The feed and plunge rates were 100 IPM.

Acrylic Guitar Templates

In cutting guitars it's important to get the router origin perfectly aligned with the wood blank. In order to help with this I routed some clear templates out of 1/4" acrylic. The origin is at the bottom center of the guitar body. Align the template, mark the bottom with a pencil, zero the tool point in X and Y to that origin and things are ready to cut.

Here's the template for the Jazzmaster:

And the Telecaster template:

These are cut with this tool, one flute, sharp point, scalloped back edge - specially made for acrylic and other hard plastics: Spiral O Flute from Tools Today.

More Guitars

I cut fifteen more guitars for Wallace Detroit Guitars. These were he first ones I did on my machine.
The flats and a few finished guitars:

The flats are screwed to the spoilboard. A few tabs hold them in place. These are easily removed via a bearing guided straight cutter bit at the router table. 

Ready for pickup, further custom routing, and finish. More details on the cutting, with the University of Michigan routers, is available here

Newer Work

Here's a post about some newer work done on a rotary axis I added to the machine.

Here's a project cutting acrylic and assembling into a figure

Tuesday, December 15, 2015

3D Printed Cytoskeleton Figure Sculpt

I've been searching for an interesting geometric variation to the figure forms I've been sculpting. I wanted to do quick sculpts from live models but use computational geometry to convert them into spatially interesting, geometric forms.

The last sculpt I did I kept very simple. I wanted the proportions correct, but only the basic form. For example barely an indication of fingers or toes. Same for the ears and face. My original ZBrush sculpt is shown below:

(The ZBrush sculpting process is described in this post).

Using ZBrush's Decimation Master and Rhino's Grasshopper I was able to get the geometric form variation I was after and 3D print the result. Below are details of the process.

The first step was to use Decimation Master to greatly reduce the face count. The original sculpt had 1.5 million faces.

Here's the sculpt after reducing it down to only 1,100 triangular faces.

The next step was to use a Grasshopper plug-in called Cytoskeleton. This is a wireframe thickening tool written by Daniel Piker. It will take a triangle mesh and turn every edge of the mesh into a solid suitable for 3D printing. If you want to try this all the Gha and Dlls you need are zipped here. Put them in your Grasshopper Components Folder (in Grasshopper do File > Special Folders > Components Folder). Note that you may need to Unblock the files.

The Grasshopper definition is super simple:

You specify a mesh, a radius for the thickening, and a Boolean to indicate if you want to use the original mesh or its dual.

The dual of a triangle is constructed by taking its center point (shown in green) and running a line through the midpoint of each edge (shown in black). Connect the ends of these lines with the corners of the triangle. This results in a hexagon (shown in blue). This hexagon is the dual of the triangle.

This is done for every triangle in the mesh. This technique was used for this form.

Cytoskeleton generates a water-tight 3D mesh, ready to print. Here you can see the dual cytoskeleton compared to a mirrored version of the original, decimated mesh. 

I used the online 3D printing service Shapeways to print this file. To keep the cost down I made it 10" long. I used their "Strong & Flexible" plastic material. It came out really well.

Here's another variation using a different technique: Tesselated Voronoi Figure Sculpt.