I need to upgrade my little CNC machine spindle. I guess I could use some general input on this, but what I think I'm considering is one of the high-speed 800W air-cooled motors off eBay. That is actually more than I need probably as single phase would work, except I need the shaft to be set up as a spindle with a collet on the end. And... well probably best to just list what I need it to do:
1) It only needs to grip 1/8" bits.
2) The work will range from engraving with a pointed cutter - equate that to ≈ .005" cutter diameter, thus the high-speed desired - to cutting with a 1/8" end mill.
3) Materials will be things like phenolic, copper-clad PCB material and various plastics. Probably never cut metal on this machine (beyond the copper on PCB sheets).
4) Needs to be pretty high speed. the eBay spindles rev up to 40K rpm but I could probably live with 25 to 30 if other requirements were met.
5) I'll probably never need or want it to spin in reverse.
6) I will want to spin it at various RPMs depending on the operation, controllable from Mach3 in both RPM and on/off. I figure that a high-speed spindle will probably have a fairly high minimum RPM too and that's ok - I'll work with that.
7) spindle needs to be solid and run true. I figure .001" runout would be fine. It needs to stand up to sideways thrust without vibrating and flexing (within reason), i.e. needs to be TONS better than a Dremel.
8) Needs to run off 110V because I intend the machine to be portable for occasional demonstrations and such.
9) Cost is a factor, though if I can't find a suitable cheap option I'd be willing to blow around $300 to $400 if I have to.
So with that in mind I was thinking of two options.
1) get one of the .8KW spindles off eBay, but either try to find one which runs off 110V instead of the 220V ones which are the only ones I see available on the net. So either the spindle can use 110V or maybe there's a VFD I can get which takes 110V single-phase input and outputs 220V 3-phase. I guess a 1HP VFD is slightly under the 800W spindle spec, but it's close so I'd think that would work OK. This spindle would be a little overkill for this machine, but if that's the only thing that will work I'll go ahead and just bite that bullet.
2) get some kind of small router or something which will be rigid, spin true and take 1/8" bits. The wrinkle here is that I want it to be variable speed. I've seen VS controls for routers for pretty cheap, but I've never seen one work and don't know if they are junk or if they burn up motors or what. I could replace the potentiometer in one of those controls with a little circuit to convert the Mach3 or Gecko output to whatever the VS control would need... I think. Seems like it's probably just a potentiometer controlling some stuff in the unit, so it's likely to be something I could hack to make it work with Mach.
So those are the two options I can think of, and I don't know enough about either one to know what to do yet. Any help is welcome.
Basically I'm looking for a way to have a decent little spindle to be controlled with Mach. I haven't really considered DC motors because what I've seen seem to be pretty bulky for their power, slow RPM and not set up to be a spindle. Maybe I'm just looking at the wrong motors? I do have a DC motor controller for 90V motors though. Hmmm. I could maybe machine a motor shaft to accept 1/8" bits and make a collet closer for it... Any better ideas out there?
This spindle will be going on my little home-made machine (link to the build thread here).
I have a larger machine in the queue on which I plan to use at least a 1.5KW motor and Hitachi VFD. That will be a much nicer machine and warrant the expense of the slick spindle setup. I'm trying to stay inexpensive as possible on this machine in part because I'd like newcomers to seeing this kind of thing not to be scared away from it because they think it's too expensive to dive in and try. But above it all, I need it to function well and my two cheap tries so far have fallen short.
Anyways, thanks for any input.