[bnoble]

Hi all, I got the CNC bug earlier this year and finally have something to show for it. I originally wanted to build a small machine for cutting out circuit boards, but after talking the idea over with my stepfather we decided to make it a little bigger and settled on jgro's design.

We started working on it in early January. It's been moving on at a leisurely pace since then and I finally think it can be considered "finished". For the most part we followed jgro's plans exactly, just making a few mild modifications here and there. The adjustment blocks are oversize and made out of maple, and 1/4" tee nuts were epoxied in and used to thread the bolts in. We went with 1/2" by 10 acme leadscrews all around, and with a 276oz-in motor on the Y-axis and 125oz-in motors on the X and Z-axis we're getting about 100ipm rapids. The motor drivers are Microstep drives from EAS, based on the LMD18245. We're running 48volts into them which really works well fighting against all that inductance.

Of course, now I need to figure out what to make with it, I find myself cutting out circles just to watch it go. I milled the lower end of a touch probe I'd like to make out of machinists wax, I'm quite happy with how accurate this thing cuts.
It's amazing to see these machines work.

[WilliamD]

Nice setup! What kind of accuracy would you say you're getting? What would you say the cutting ipm's are for what you're doing? Sorry for all the questions, I'm collecting all the stuff to build one myself. 100 ipm rapids is pretty good. What is that blue stuff that you're milling?

[bnoble]

Accuracy kind of depends on how slow you're willing to go. I usually stay between 10 and 30ipm, and that seems to have worked well for me. Any faster, and I'd be worried about the gantry flexing too much. If I could build the machine again (and I might), I'd incorporate the torsion box idea as spalm and others have done. (Link here.) A lot of guys build a jgro style machine to build parts for a second machine, but I think with a few modifications it has the potential to be plenty rigid for many hobby applications. I'm not saying the original design isn't good, I just checked a small part I cut out a few days ago, and it's within 3 thousandths, but I did take it slow.

The blue stuff is machiniable wax, I got it from Enco. It's a little expensive, but you can melt it down and re-use it, and it cuts wonderfully.

Hope this helps,
Bryan