I got a lot of suggestions with respect to how to clean the slingshot up. I took my time to think about it, but in the end I went with the solution that may not be the easiest nor the fastest, but I think will yield the best results.

I took a board of insulation foam. This stuff is great for making fast prototypes by the way. I cut out the negative space of half the slingshot. No roughing pass, just hi-speed parallell finishing with a small ballnose. This enables me to ‘hold’ the 3D-part 100% level to the Z-plane, and the added bonus is I have a working zero! It fit snugly and didn’t really need extra clamping.

To remove the outer layer of filth, I thought of a pretty elegant way.

I could just have lowered the Z by a hair, but then the vertical walls would practically be left untouched. I could offset the 3D file inwards, but I don’t know Rhino all that well, so it would take some time to figure that out. Then it hit me, My ballnose is 1/8″, so 3.175mm. I created a new ballnose tool with a 2mm diameter in RhinoCAM, and exported the new gcode for it. When running this code with the 3.175mm tool I have, it will effectively shave 0.6 mm all around the 3D shape. Took me 2 minutes. Pretty clever even if I say so myself. 😉

Seems to do the trick! I took a 5% stepover, which will give me a finish that doesn’t need more sanding.

First thing I’ll do then is coat the hell out of it. 🙂