Re: [CAD_CAM_EDM_DRO] Disappointed Lathe CNC

"Carey L. Culpepper" wrote:

> Bill: I was lurking here also waiting for answers concerning lathe
> CNC.
> I have a big job sitting here that looks like it is going to require
> CNC. I just finished mounting a 5 phase stepper to my South Bend model
>
> A. Will mount the crossfeed motor tomorrow. That will be a bit more
> challenging. I have gone through my BobCad manuals and found very
> little
> help there. Lathe work seems to be the ugly sister as far as BobCad
> goes. I found lathe cutters in one tool file but can't get it to come
> up
> where I think it should be. I am in desparate need of some help to get
>
> this figured out.

Simple turning (and fancy stuff, too) is really not very different from
either
the CAD/CAM or CNC program's view. Mostly, you are moving a
tool to remove material from stock to produce the desired shape.
In the case of turning, the part is going to be rotationally symmetrical

no matter what you do. So, you can think of the toolpath as moving
along 1/2 of the part cross section. Now, getting tools entered in
Bobcad also has me stymied, but you really don't need that feature
much. If you had a tool with a 1/4" radius, you could tell Bobcad
that you had a 1/2" end mill (radius = 1/4") and it would generate
the correct moves of the machine.

Now, from the XY plane, the moves would be right for a vertical
mill, but not naming the correct axes for turning. You could
write a tiny program to swap the axis names, even an editor
macro would do it.

Or, you could draw your part in the XZ plane, and I think
Bobcad will just turn out the right axis names. You still have
to tell it which lines to cut, and which way to travel.

The thing we are leaving out here is coordination between
spindle and X-axis position, as for threading. For these,
I think you want to code up some standard thread
routines and do it manually. or with a small program
that generates the sequence. Then, you just insert
that fragment of G-code into the rest of your CNC
program. I don't know whether EMC supports the
coordination of axes yet. It did once, but that feature
hasn't been used in too long.

Jon