Re: EMC & Linux

> From: "Tim Goldstein" <timg@...>
>
> I just checked the ftp server for EMC and there is a new build dated
> June-5-1999 on the site. Don't know what it fixes, but I am downloading it
> right now and will report back later.

Sorry, I forgot to tell you. I believe this fixes the problem of
DEFAULT_VELOCITY not affecting the default feed rate. It also may limit the
max feed rate to MAX_VELOCITY. Fred told me this on Friday, but I was sick
and my brain was clogged up so I didn't do any writing to the list and by now
I've forgotten the exact details. Fred also e-mailed a question to me today
on this same subject and I'm sure he wont mind my echoing it here as well as
my reply:

> From: Fred Proctor
> To: mshaver@...
> Subject: Feed rate override and max feed rate
> Date: Saturday, June 05, 1999 6:49 PM
>
> Matt,
>
> More detail than I left on your answering machine: consider this
> example:
>
> 1. As set in the ini file, the max feed rate is 60 IPM and the max
> allowable feedrate override is 200%.
> 1. You set the feed rate override to its max, 200%.
> 2. You MDI "G1 X10 F60", which moves the machine at 60 IPM despite the
> 200% feed rate override, since the max feed is set to 60 IPM.
> 3. You reduce the feed rate override to 150%, then 100%, then 50%.
>
> What should happen? Should the feeds be 60, 60, 30, or should they be
> 45, 30, 15? In the first case the operator would be surprised that
> reducing the feed rate override from 200% to 150% and 100% had no
> effect. In the second case the operator would be surprised that at the
> final 50% feed rate override and a nominal 60 IPM, the feed is actually
> 15 IPM.
>
> What is your experience with other CNCs?
>
> --Fred

I replied:
-----
I think the 60, 60, 60, 30 scenario is the correct one. The way this is
handled in other cncs is that the rapid traverse rate is greater than the
highest allowable _programmed feed rate_. Also, the feed override control
usually only goes up to 125%. For example, on a mill that rapids at 150ipm,
the max feed rate you can program might be 100ipm which can be increased to
125ipm with the feed override knob.

Some random ideas:

1. Add a MAX_PROGRAMMED_FEED_RATE parameter to allow setting up the
conditions described above. The writer of the .ini file could always goof up
and allow MAX_PROGRAMMED_FEED_RATE x MAX_FEED_OVERRIDE > MAX_VELOCITY, but
the maximum actual velocity should never exceed MAX_VELOCITY.

2. Maybe there should be a "clipping" indicator when this error condition
happens.

3. Maybe there should be an _actual_ feed rate display to compliment the
_commanded_ feed rate display we have now. If we go to the "exact path"
motion control system this would show when the system is forced to decrease
the feed rate to keep acceleration within bounds.

Sorry I didn't get your phone message earlier, I've been home most all day
but I left to go to Radio Shack when your message came in and I never looked
at the machine until I read your e-mail. The stepper control hardware is
progressing...

Thanks,

Matt
-----

If anyone else has suggestions on how to handle this, speak up!

When I do a software update, I usually:

1. Save run.emc (or whatever you've named your customized script), emc.ini
(ditto here), tool.tbl (tool data), and rs274ngc.var (the offsets). Also save
any other stuff you want to keep that is in or below /usr/local/nist/emc.

2. Go to /usr/local/nist and run ./clean which removes everything including
the emc directory.

3. Put the latest emc.tgz (whatever its name) in /usr/local/nist and
un-tar/zip it.

4. Run ./install to compile the new version.

5. Put back the files you saved in step 1.

There is a ./update script as well that I believe saves your customized
settings, but I've never used it. If you try it, let me know, maybe I should
too!

> Thought I would take the opportunity to start a new thread name as the
> original one of Linux vs. DOS has become just info and tips about setting

up

> and using Linux and EMC.

A good idea! I'll start using it too.

Matt