On Sunday 12 April 2015 11:07:41 Neil wrote:
> Another couple things I can't yet find...
>
> (1) How do I tell LinuxCNC that I am at a specific position. So I set
> Z to touch the top of a part and I want to tell it that's Z=-20. In
> Mach 3, I type the value in the DRO-displayed field.
To me, used to LinuxCNC, I'd call that a bit spooky. What we do is
highlight the dot for the axis, and click on "touch off" which will open
a small window allowing you to type a number into it. If you have
precisely enough located the top of the workpiece with a G38 command
I(see the fine manual again) and the machine is stopped at that contact
point, then it will be sufficient reference, so enter "-20.00000000" and
hit ENTER. The entry box will be closed and the Z position in the DRO
display will now show Z to be -20.00.
> (2) Extra credit -- is there any way for me to set the Z-position to
> touch the top of a part (or table), then have one button set that to
> Z=-20, then it would automatically home X and Y? This would just make
> setup as simple as possible.
Someone more familiar may say it can be done, but I haven't found
anything in the docs that sound anything like that.
But again, you are asking potentially deadly machinery to move, and I,
like most here, would discourage trying to do a one button solution for
2, almost the same problems. IMO, zeroing the tool against the workpiece
is a valid operation, but when that is done. LCNC will force you to set
the home positions for every axis that is defined in the .ini file since
it will not do any other moves until it knows where it is.
So the proceedure is
In the HOME_SEQUENCE, make z the last. Set its parking place at the
contact point of 0.000000.
1. home it all, by manually presetting it so Z is up in the air and will
clear everythingso as not to damage or demolish either the workpiece or
the machines tool as it moves to set the X and Y from each axis's own
home switch. Set the offsets in the .ini such that it is parked at the
center of the workpiece top when xy is done.
Then, assuming the workpiece is isolated and the probe lead for G38 is
attached, a bit of magic logic in the .hal file will let you use the
probe contact as the z home function, but you will not be using the G38
directly, you will be using that contact, crossfed into the homing logic
to find the top of the piece and thereby zero it there, and leave it
there.
2.When the homing is done, then click the z button, then the touch off
button, and enter your -20.0000000 offset there. You are, or should be
ready to load your code and hit the r button on the keyboard, it is all
ready to go.
The excess precision is to keep math rounding errors to a bare minimum.
If re-running the same code for multiple parts see the manual for how to
re-init all that stuff at matching zeros because the touch off entries
are cumulative, so the re-init of all available co-ordinate maps to
match the machine's zeros in the G53 map then puts you back to square
one every time.
> Cheers,
> -Neil.
>
HTH.
Cheers, Gene Heskett
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>
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