Quite interesting thank you, I found myself watching the full 23 minutes.
This guy must be @Luke’s hipster cousin or something ? 
That’s a beautiful piece he made, but I was interested in that part :
It’s subtle, but the marks are there. If a $4000 ballscrew machine grants this (nice) result, the result we get from a Shapeoko are not too shabby.
He also seems to be using some kind of coolant/mist?
I’ll watch part 9 now.
Well watching part 9 already paid off, because out of the blue he shares a great tip about a miniature edge finder from Proxxon that has a 6mm shaft, at this point in the video.
Funny how he mentions that “if you have something like a Shapeoko with a Dewalt router this won’t work” , which is true since he mentions a max speed of about 400 RPM. Enter the modded Shapeokos with water-cooled VFDs, and I now have ONE MORE THING I need to try 
New to me too. Shame about the RPM limitation but good to see a metric option!
I’ve been using a cheap 10mm edge finder in my VFD spindle for a while now, it’s invaluable for those times where you don’t have a square flat piece with a WCS on the bottom left corner, and for not forcing you to set up that way. Mine says 1,200 RPM as the target speed.
Some of the earlier parts are interesting too. In part 2 he describes having to move his compressor away from the CNC because it was putting marks in the workpiece when it started up by shaking his machine.
Try this, spray your workpiece with olive oil, it will reduce the tool marks. You can call me crazy, but it works.
Hi @Julien, maybe a little too late here, but did it ever occur to you that this might have to do with how F360 extrudes 2D curves into bodys? My thought is that while you have a 2point arc on the sketch… when you extrude that into a 3D body the 2point curve actually transforms into a multi-point vector arc along the bodys curved edges. Food for thought, visually thats how it shows in F360s webbased viewer…
Hi @MarkDGaal, yep there are definitely lots of small arc segments in the generated G-code along the curves (as can be seen in that earlier post in this thread), and it seems that GRBL turns arcs into tiny linear segments anyway. But those segments are very small, an order of magnitude smaller than the periodicity of the tool marks on the piece. A test I did early on is to cut a perfect circle: the generated G-code was then made of exactly four 90° arc commands, and still the marks were there. I also tried Fusion360’s “smoothing” options to minimize the number of subsegments along curves, to no avail. That and measuring the toolmarks spacing along a 1° line kind of convinced me it is (only?) stepper quantization, but I would love to change my mind if someone came up with a smooth curve in acrylic on a Shapeoko!
For folks who are curious about the underlying math and principles on this see:
http://mae.engr.ucdavis.edu/~farouki/ijmtm99a.pdf
Academic paper discussing how curves, arcs and circles are handled and the consequences of representing them as polygons or polylines.
that and two more references are at:
Not exactly applicable. Probably best to rezero after those CNCj’s soft limit alarms?
I hit a slab of .375" cast acrylic at my full rapids speed, whatever the max jam I could cram is, and it ripped full .375" material and a stack of wasteboard before even starting the ramp. I didn’t know what happened, rechecked the fusion file and post, nothing wrong, rezero’d, started the op again. Very little contact on the 2nd attempt op. The roughing vs finishing limits are probably quite interesting.
I know him personally. Haven’t seen him since 2006 where we met in Zagreb, Croatia.
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