Re: NEW member Suitable conversions?

> > From: "Matt Shaver" <mshaver@...>
> >
> > > From: D.F.S. <dfs@...>
> > > How could the system intelligenty do a "Tool Change" without simply
> > > making me do absolute positioning of the entire table based on

presumed

> > > tool location.
>
> > Some controls (this includes the EMC) have "work coordinate systems" or
> > "fixture offsets" that can be independently adjusted and called up as
> > required in your program.

You should not need work offset for a lathe. Just use the tool offsets,
with x & z distances from say tool number 1. When you next run the same
job, put the tools anywhere you want, and just compare their locations to T1
to set the offsets. This will work if EMC keeps track of X & Z offsets.
Most lathe controllers can, and this makes set up a lot easier.

>
> As a second question, how good is the accuracy of threading on
> systems with encoders on the spindle or chuck?
>
> Clearly it must work, but I still have doubts considering the
> rotational speeds of the work, and the inertia of it, and the tools
> themselves.
>
> I'm talking single point on CNC lathes in particular.
>
> Is it really possible with any accuracy, and can it be
> done in multiple passes and pick up at the correct location?

The accuracy is as good as the spindle, the encoders, and the machine
ways/frame condition. If you have an older machine with a 5T controller, it
should be NO trouble, as this control was an expensive, commercial product &
used for years to single point turn threads. My little threader program was
specifically written to program my Pratt & Whitney lathe with a Fanuc 5T.
If you have the Fanuc manuals look in them for the alpha and beta
calculation formulae(in the Appendix I believe). It tells you the max rpm
and distance required to get the tool in synch with the spindle, and how
much distance to allow for pull out. There is a short distance on both ends
during which the threading tool is not in the true position. I usually
allow about .100 inch in front of the start of the thread (in Z) to avoid
problems.

In case you missed it, there is a link to my threader program at:
http://209.69.202.197/cadcamedmdro.html


Best Regards,

Fred Smith
IMService

imserv@...
Phone: 248-486-3600 or 800-386-1670
Fax:248-486-3698