In a previous project, I 3D printed a fidget spinner. It was in the shape of the Adafruit logo and designed using forms in Autodesk Fusion 360. I had originally 3D printed it vertically to achieve a smooth surface finish (though, it requires support material & rafts). A few folks in the community asked, “Why not 3D print it flat on the bed?”. Hadn’t actually tried, I quickly thought of using the concentric external infill pattern feature in Simplify3D. 3D printed flat, leaves lots of build lines and appears a lot like a machined part.
This led me to try CNC machining the part on the Othermill Pro. Since I already refined the part for 3D printing flat on a bed, it’s also “CNC” ready. I had a cheap piece of pine stock laying around, so I thought I’d use that for testing. Next, I had to come up with the tooling strategies in Fusion 360. I was able to resolve the part using just two processes. 1x 2D Face, produces a quick operation for preparing the thickness of the material. 1x 3D Adaptive clearing, makes a series of cuts with variable depths to produce the part by removing quantities of material. I only used one tool for the job: a 1/8″ flat end mill. This took approximately 2hrs to machine (same amount of time 3D printing) with a cutting feed rate of 800mm/min. I did a light sanding just to remove all of the burrs. It could be smoothed a lot more and could even be stained.
I think it was a good first test of machining a 3D object. I’ve only made a handful of parts so it was good practice. If I were to machine it again, I’d adjust the center pocket so it has a tighter hold on the 608 bearing. I had forgotten it was designed for 3D printing, so it’s a bit more open. If I were to guess, I’d need to offset the inner diameter by 0.1mm. I’d most likely run a test cut using scrape material first (which I have plenty of). I’d also use dense wood like or walnut or hard maple for the final part.
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