Following the decision to work with the Fablab to create the forms using their large flatbed CNC with 3 axis functionality, myself and the current head of the Fablab began the first tests to establish how the forms would look and how the CNC would deal with them. The first test would define how 1. We would write the toolpaths for the surface 2. What setting we would use for the cutting the tool 3. What finish these settings provided on the surface. We used the software Artcam to write the toolpaths for the CNC. The first test would involve only CNC’ing one side of the forms. Single sided 3 axis CNC cutting is very straightforward. It was simply a case of doing the following steps-
- Set the materials block dimensions
- Import the 3D file, move and orientate it onto the material
- Once you are happy with the models position, paste it onto the CNC bed
- Set the roughing toolpath. This involves selecting the type of cutting bit you are going to use, of which there are many ranging from a 2 flute downward spiral to a 4 flute ballnose bit. Each tool provides as different finish and is used for different types of material. We are using a ballnose as it gives the best finish on curved surfaces. We selected a 12mm bit as it was the longest bit we had so it would have no problem reaching the deep valleys in the surfaces. For roughing, the settings relates to the material being milled. Because we were using blue foam as a test, we could ramp the settings up for a speedy roughing process.
- Set the finishing toolpath. This toopath used the same bit as the roughing toolpath but the settings were much more gentle, smoothing the surface and providing a clean finish. The finish was something I was interested in as I wanted to know what type of surface the 12mm ballnose would provide me with.
- Finally, you send the toolpaths to the CNC machine and set it to go
Below you can see the successful first test on the rear surface of Earth. I am pleased with the finish provided with the 12mm balnose cutter in blue foam and thought the surfaced looked really nice. Having said that, it was quite rough still but this could be reduced by changing the setting of the finishing tool path around.
Below is a short video of the process. I love how the CNC bit follows the forms of the surfaces. I think it is really interesting to think that at large, the path of the tool is defined by the planet of which form it is creating. The data from the planet has gone onto to generate more data first read by a computer to generate a STL file and then read by a CNC machine to create paths for a tool to follow, bringing the form into reality.