Lathe
I managed to get hold of a small CNC lathe. Its a Myford Speed 10 that was
converted to CNC commercially in the late 80's - lots of them were done as
training machines for colleges & schools. The control was via a BBC Master
computer.
The only problem with the old controller was - it didn't do internal threads.
See
http://www.lathes.co.uk/myford/page4.html
for pictures and specifications of the non CNC version.
It has a few nice touches, like thrust races between the stepper motor faces and
the rigid ballscrew connector to kill any backlash there, and telescopic shrouds
on Z axis ballscrew.
It was originally driven unipolar, I've replaced both steppers with double ended
and driven bipolar via Gecko's. There's a Nema 23 240oz in on X and Nema 34
480oz in on Z. They seem plenty meaty enough, It will take 40 thou cuts in
steel, but I limit myself to .5mm (20thou) on roughing, tool & machine life is
more important to me than speed <G>.
The screw pitches are metric, X is 2.5mm, Z is 4mm, it will run at well over 40
inches per minute on rapids, which on such a small machine is too fast for my
liking. I've de-rated it somewhat by limiting top speed to 20 ipm.
The machine runs flawlessly using Dolphin Partmaster as my CAD/CAM program and Mach3 as the controller.
Here are some close up detail pictures for those thinking of converting one of the similar far eastern models.
Note the last picture, Its the spindle speed sensor as shown on my CNC page. It's just a disc with a 2mm slot running in the opto gap. Works fine and contrary to popular belief, it is possible to make multi-start threads with only 1 pulse per rev!!
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Stepper Motor Drives, Stepping Motors and Motion Control Equipment from Alzanti
Steve Blackmore
Copyright © 2003 Steve Blackmore