Re:[CAD_CAM_EDM_DRO] recomendations for CNC'ing a lathe ( was Re: Lathes

Hi,

I have a Harrison 280 CNC/Trainer lathe. Besides the controller being an
Acorn/BBC type computer, and probably in need of replacement, it is a good
place for you to start looking. I am considering installing a PC and
TurboCNC software but want to test on a smaller machine first. Not only will
the 280 run under full CNC control with G-Code input, it can also be used as
a manual lathe with electronic movement and also as a completely manual
lathe. This machine cost over £18,000 twelve years ago and, because the
school it was put into didn't have anyone qualified to use it, has never
done a days work.

The X and Z axis have servo motors, mounted on the back end of the
leadscrews, and also manual/handle operated leadscrews. The leadscrews are
acme threads and not ballscrews, this is possible because normal lathe
operation doesn't require cutting where backlash becomes a problem.

There is a screw cutting gear-box with the normal thread pickup dial. The
spindle has an encoder so it can cut threads under CNC control using the
canned cycles.

So you see apart from having a few extra switches, so it isn't possible to
run under CNC control and engage the gear-box at the same time, there are
very few differences between a fully manual and CNC machine.

Regards,

Terry

> I re-built and rewired the fwd and rev starters on a small (12x48)
> lathe today. in talking we spoke about the CNC table for a mill and
> how much 'modification' to the Bridgeport he would accept.
>
> seems the fine feed is a prime candidate for CNC as it is easily
> connected, easily removed and does not effect the machine.
>
> OK, on to the lathe.
>
> While we were talking, he asked me what would it take to convert an
> engine lathe to CNC and still have full manual use ?
>
> As I see it, one would need some beefy steppers or servos. if I was
> to undertake this project, he offered to pay for all the parts, and
> in exchange, offer free use of the shop. I'm not sure I have the
> time to do this, but I am interested in putting the basics together.
>
> What is the best way to CNC a lathe ? servo's or steppers ?
> if one is threading, but not via CNC would it be easy to set a stop
> to the cross slide to retrace at the end of the thread ?
>
> What software would be most useful for a lathe CNC operation ?
>
> Currently I use excel for some of my g-code, and hand enter others.
> this could be as simple as hand or more automated, as we are both
> somewhat conversant with g-code.
>
>
> Dave