Today managed to cut a 3D part using my CNC mill (rather than 2.5D like the other stuff I’ve done so far).
Here are the source files: balsaholder
I did the design drawing up in Google Sketchup.
The file was exported from Sketchup to STL format using an STL Exporter plugin in Sketchup.
The STL was processed into g-code using FreeMill.
The g-code was then run in the CNC machine to produce the part.
I got stuck on Freemill for a while. You have to run it as administrator (right click then “run as admin”). If you don’t it will fail when you get to the end because it tries to write the g-code into it’s own program directory where there isn’t sufficient privilege for the program process.
I used pretty well all of the defaults of FreeMill except I put in the specific dimensions of my endmill (1/8 diameter, ball radius 0, length 1).
Part dimensions: The measurements of the part do not match the measurements of the drawing from Sketchup. I suspect I have to calibrate the machine (Mach3) or there is something wrong with how I made the g-code.
The 4 1/2″ measure in Sketchup is 4 1/16th” on the part. The 12 1/2″ measure in Sketchup is about 12 1/8″ (measured with ruler). So those two came out a little shy.
I find this puzzling because the 1×1″ square in Sketchup is 1 3/8 x 1 7/16″ (1 3/8″ side is in the direction of the 12 1/2″ measure).
Something is fishy that the 12 1/2″ came out shy but the 1″ along the same line came out long.
Feed Rate: It took really long. Next time I will us a feed rate that is much faster. I’m supposing next time I’ll try a feed rate that is about 5 or 10 times faster. I was running on full override and it was still crawling.
Holes: It seemed to miss the holes. I think I made them right in Sketchup but they didn’t come out on the part.
Multi-pass: The g-code is quite simple. It removes all material in one pass. When it made the edges it plunged about .6″ and cut across the board at that depth. I will look in FreeMill to see if there is a feature to have it remove material in layers.
Clamping: I had to move a clamp and the workpiece shifted a bit. The piece has to really be clamped well. I’m going to get more hardware for clamping.
Dust: This is still an issue. I don’t like lording over the piece with a vacuum. I went out and got some hose so I vacuum near the spindle automatically. I wound up with some 1 1/4″ ID pool hose. It’s pretty light and flexible. I got enough to mount it on the machine. I now need to make a mount for the spindle and a mount for the base so I can just plug the vacuum in when I want.