Zapp Automation are good for steppers and mechanical components. Drivers are a bit pricey IMHO but I'm sure excellent quality. Quick look on eBay shows you can get a BoB and 3 stepper drivers for about 75 quid. There are also a lot of suppliers of suitable psus on eBay. I fitted my Denford Novamill with new electronics for significantly less than £200 mainly from eBay.
On the question of strength of the mill, with cnc because the machine does the work you can use smaller cutters running faster which I think makes less demands on rigidity. But having a round column without a gib will makes tool changing a pain and really only a lead screw gives good z dimensional accuracy, rather than a quill feed.
Backlash is a pain, and in my experience the backlash compensation in Mach3 only works well for very small amounts of play. You may think that your screws don't have much backlash, but I think you will be surprised if you measure it. My manual VMB and Super7 both have about 0.2 mm backlash in their leadscrews - I've cnc'd the lathe with a ball screw on the x axis, but I need to convert the z axis, as it's a pain having to plan some cutting sequences to compensate for it.
Oh and on software, Mach 3 is pretty good overall. LinuxCNC may be better and it's free but I think unless you are comfortable with a non Windows environment you could find it harder to set up. Another point is that standard Mach3 assumes a PC with a parallel port, and these are getting rarer now. You then use the BoB to adapt the parallel port to the stepper drivers. I've followed this route on both lathe and mill but starting again I would use a USB or Ethernet motion controller. Look for Smoothstepper or CSM products, there are others around too.
Backlash compensation in any software, not just Mach, is pretty much a sticky plaster approach. All it takes is for whatever cutter/drill you're using to push the table, and the free play could end up in either direction of the lead screw.
Things like always conventional milling do help to control the play, but it's still not guaranteed.
thanks guys for all the input.
i did look on ebay at the electronics, as you say you can get the kit for less then £200. but the sellers are either hong kong or china.
now i bought a few things before from sellers in china, but what if a stepper fails or there is a problem.... posting stuff back to china isnt going to be cheap and turn around takes longer then in the uk.
Last edited by T0rnado69; 30-03-2014 at 09:26 PM. Reason: typo
I have not got round to fitting this yet but will let you know the results when I do.
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