Hi all-
This summer’s project for me is to design and make the hardware for my HF 7X10 CNC conversion. I’ve looked at some people’s methods on how to do this, and was wondering which would be the best way to go about it. I’m hoping to make it capable of both CNC and manual operation and would like to keep it accurate, though I don’t really need sub-tenth-level accuracy for what I do (+/-5 thou is pretty much good enough for me). From what I can see, there are 3 main methods people have used…
1. Attach the main feed screw to the stepper/servo motors… The pros I’ve heard on this is its simple and it lets you go back and forth from CNC to manual with a flick of the power feed switch. The main con has to do with accuracy and premature wear of the screw due to constant use in this way.
2. Rig the saddle directly, either putting the motor directly on the Z axis shaft or by attaching a timing belt to the back of the handwheel and running that to the motor. The pro I can see here is easy CNC/manual use, but the big con there I can see could be a low level of accuracy (I haven’t measured what the backlash in my rig is, but its clearly visible).
3. Run a separate ballscrew (or other type of screw) to the saddle and run this to the end of the lathe where the motor mates with the shaft independent of the other systems on the lathe. The pro I see on this one is possible greater accuracy (with a properly done ballscrew setup) but the con I see there is it will make it all but impossible to use manually; every time you try to crank over the Z feed, you’ll have to fight against the ballnut and could cause it to wear out faster by attempting it. This one also looks to be the most expensive setup due to a new ballscrew and nut. Does anyone know a way to make it possible to use this setup manually with the existing handwheel on the apron for the Z feed?
Does anyone have any thoughts or opinions on this? So far, I’ve seen Ron Steele’s conversion, FigNoggle’s and the one being built at CNCFusion- all three look to use option #3. JFetting’s design (the free one floating out there on the net) uses option #1- his looks OK, but I have to wonder at his using a compression/clamp fitting to hold the Z axis motor on the machine- it looks fairly weak and potentially inaccurate (due to slippage through use) to me. Does anyone have pictures or links to any other conversions I might reference? Lastly, I’ve seen a few places where there are CNC’d turrets out there (I have 2 sets of plans already and seen one where the author sells the plans). Does anyone have any thoughts or advice on using/making these or know of any plans on the net?
Thanks-
Farasien