Amadeal CJ18A CNC Conversion

[JohnHaine]

I converted a Super7 to CNC 12 years back. I did not fit a ball screw to the Z axis on the basis that the vast majority of turning operations can be done only moving the tool towards the headstock. Initially I used ordinary screw on the cross-slide but quickly found this didn't work so fitted a 5mm pitch x 12mm ballscrew to that, directly driven from the stepper. In order to fit this I had to "reverse" the nut as its diameter was too large, though having a power XF S7 the hole in the cross slide was just big enough for the 12mm ballscrew itself. If you can't fit a 10 or 12 mm screw it is possible to get 8mm ones though they are more expensive. Have a look at https://cncyourmyford.com/ to get some ideas.

That website shows a ballscrew on the Z axis too, one day I may get round to that but manage without it.

For the controller I use Mach3. I have a single slot encoder on the spindle and for a lathe like the Myford with a fair amount of power and inertia this is fine for screwcutting. There is a lot of disinformation around about Mach3 and screwcutting, it does actually work pretty well. I attach a photo of the thread cut for an ER16 collet chuck which is a perfect fit in the nut. I cut this using the threading wizard, no adjustments needed, home-made tool, infeed calculated from the Martin Cleeve formula in his book.

However Mach3 is long in the tooth now and unsupported, Mach4 is better and can I believe support a multi-slot encoder which can accomodate a less powerful spindle drive. I have flirted with Linux CNC but I'd rather cut metal than wrestle with software.

Just to add that you don't need active spindle speed control to do good threading provided the speed remains sufficiently constant while cutting - in fact I believe that systems with multi-slot spindle encoders adapt the feed rate not the spindle speed. My spindle is not even controlled from Mach3, I turn it on and set its speed via a VFD.

And also to add that I run Mach3 on a Dell mini PC with Win10, using a UC100 motion controller connected via USB. The one change that I would like to make is to update the stepper drivers as the ones I have are limited in step frequency.