Re: Re: Old CNC controls

> From: Jon Elson <jmelson@...>
> No, there is a G-code for synchronized threading. Apparently, there are
> two
> very similar codes, one for mills (G84) which is a tapping cycle, which
> reverses
> the spindle at the end of the move, and backs the tap out of the hole.
> This has
> apparently been implemented, although it is not in the interpreter
> documantation.
> I was assured by Fred Proctor (or was it Matt Shaver?) about a year ago
> that
> GM Powertrain had tested it on one of their big machining centers, and
> it worked.

It's true, but this is back in the PMAC/Windows NT days, so it may not be
there now, or work anymore. If someone wants to do this it could probably be
put back in or fixed as required.

> Well, it is not a 'compensation'. You need to install a spindle
> encoder, with an
> index channel, and hook it up to an encoder input on the STG board (or
> whatever
> you are using). EMC computes where the Z axis should be relative to
> spindle
> position.

Another way to look at this is "electronic gearing". The EMC (and other
controls that thread) start up the spindle and then "sync" or "slave" the
other axis (usually Z) to the spindle encoder. This explains why the Z axis
must travel a short distance before you can cut the workpiece.

Matt