Re: Feed hold with G-Codes

--- In CAD_CAM_EDM_DRO@yahoogroups.com, John Dammeyer <johnd@...> wrote:

>
> Hi,
> For the various CNC systems out there, how do they handle feed hold

while

> threading on a lathe?
>
> Say you specify that the system should do the thread in 12 passes.

If you

> feed hold after the sixth pass, and the restart, does it restart at

the

> beginning and just turn empty air until it reaches where it stopped?

Or

> does it continue where it left off. I'm assuming threading here with

the

> single line G-Code. I've always assumed that Feed Hold stops on G-

Codes and

> not in the middle.

Except for threading and synchronized tapping cycles, feed hold stops
all slide motion. For threading and tapping commands, feed hold is
effected upon completion of the current line of either G-code ( ie G33,
G84, etc). Stopping the spindle during either operation "should" stop
slide motion.

If you have a multiple pass threading process, restarting a program
after interrupting in the middle should cut air until the previous last
pass completed is repeated, then cutting should resume as if it was the
original run.

In the past some controllers have permitted feed-rate override to be
used during threading cycles. This is usually excluded as the thread
pitch is messed up, however, I have seen some VERY expensive CNC lathes
that would not correctly repeat the cut if feed rate override was used
between threading cycles.

Fred Smith - IMService
http://www.imsrv.com