Greetings Guys;
2 questions actually:
1. What is the schedule saying about the renaming of this list to
linuxcnc-users@etc?
2. I apparently am having trouble understanding the G92 family docs, which
state:
------------------------
G92 makes the current point have the coordinates you want (without motion),
where the axis words contain the axis numbers you want. All axis words are
optional, except that at least one must be used. If an axis word is not
used for a given axis, the coordinate on that axis of the current point is
not changed.
When G92 is executed, the origins of all coordinate systems move. They move
such that the value of the current controlled point, in the currently
active coordinate system, becomes the specified value. All coordinate
system’s origins are offset this same distance.
For example, suppose the current point is at X=4 and there is currently no
G92 offset active. Then G92 x7 is programmed. This moves all origins -3 in
X, which causes the current point to become X=7. This -3 is saved in
parameter 5211.
Being in incremental distance mode has no effect on the action of G92.
G92 offsets may be already be in effect when the G92 is called. If this is
the case, the offset is replaced with a new offset that makes the current
point become the specified value.
It is an error if:
all axis words are omitted.
LinuxCNC stores the G92 offsets and reuses them on the next run of a
program. To prevent this, one can program a G92.1 (to erase them), or
program a G92.2 (to remove them - they are still stored).
----------------
Ok
Then:
------------------------
G92.1 - reset axis offsets to zero and set parameters 5211 - 5219 to
zero.
G92.2 - reset axis offsets to zero.
G93.3 Restore Axis Offsets
G93.3 - set the axis offset to the values saved in parameters 5211 to
5219
You can set axis offsets in one program and use the same offsets in another
program. Program G92 in the first program. This will set parameters 5211 to
5219. Do not use G92.1 in the remainder of the first program. The parameter
values will be saved when the first program exits and restored when the
second one starts up. Use G92.3 near the beginning of the second program.
That will restore the offsets saved in the first program.
------------------------
That seems to intimate that using a G92 axis number not only stores the
desired position in the axis named, but also stores the rest of the axis
positions in 5211-5219.
What I am trying to do is add some position offsets on a per axis basis,
but if a G92 actually updates all axis's to the current location except the
one named in the G92 command, then the subsequent execution of a g92.1 it
seems is restoring bogus numbers, as is evidenced when a new home operation
is done, the z reading of 4.0681 doesn't revert to 0.0000.
So, assuming the machine is sitting about .040" above my little brass tube
I set in the pallet, nominally at X-0.3 Y+0.2, where I run holefinder.ngc
in order to locate the precise location that brass contact within half a
thou both ways. This routine uses G38.2 a total of five times, and sets
#100 to the real X location, and #101 to the real Y location. I then use
those #vars to move the machine to a position that is X-0.100, y0.000 from
what should be the boards left front corner, and home x and y there.
Then I raise it far enough to change out the drill chuck holding the
conical tipped metal probe out for a collet and a 1/8" shank engraving bit,
which raises the effective tool tip by about 4" since the collet is that
much shorter than the drill chuck when its mounted,about 0.1" and run it
down slowly with the down key until the bit contacts the pcb triggering the
stop during a jog function. At that point, I home the Z. Its a bit
abitrary as I do that same G38.2 once in the o<tedautoz> call and use G92 Z
to install a very small offset, a thou or less, in Z so I can fine tune the
depth of the engraving done in the top.etch file.
Now, in the remainder of the files, 4 more to complete the board, and at
the present I am using the holefinder to locate a hole drilled in the
board, which when the board is turned end for end, is used to install the
offset value into the x so that the etch and bot.drill will result in the
drill bit tips exactly meeting in the center of each hole. I know I will
have to break this holefinder into 2 files since I don't want to muck with
the Y location when running it the second time.
Obviously I have to use G92 to install the Z offset that compensates for
the drill length, that is unavoidable from my reading. I have no lengths
in my tool table since I'm using a drill chuck, making those lengths
arbitrary and requiring I G38.2 to find this out after every tool change.
So what is the sequence of G9X's I must use in the remaining 5 files it
takes to complete a board?, and which will not result in the machine moving
its Z zero up in the air, both in axis display, and visually, about 4" for
every tool change after the 2nd one. It seems to me that I need to restore
its reference such that if I ran it to X0.0Y0.0Z0.4, it should be sitting
exactly over the corner of the board and not very high above it since that
was located by a probe of similar length as one of the smaller drill bits
originally. That would seem to need a G92.3 at some point in each tool
probe.
At that point I seem to be lost and can't find the tree I want in all this
forest.
Thanks for any clues, or cluebats as the case may be, that will help solve
my apparent loss of Z references problem. Ideally, I would like to put all
this stuff in the callable autoz function as that simplifies the editing of
the pcb-gcode outputs to just adding the o<(ted/bed)autoz> call after each
M6 T# in the rest of them, and adding a spindle speed in the top of each
file since pcb-gcode, while asking how long it takes for the spindle to
spin up, doesn't ask for, or issue an S command. Duh...
I'll be reading that doc some more, but it all hinges on: Does a G92 Z#
diddle the other 8 vars in the 5211-5219 group, or just the Z offset?
It seems that what I want to do is restore the whole snapshot exactly is it
was when last HOME'd, so that axis displays where it is in reference to
this original HOME'd position. Perhaps there is such a command and I'm not
recognizing it?
Thanks again guys.
Cheers, Gene
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
My web page: <http://coyoteden.dyndns-free.com:85/gene>
Jones' Motto:
Friends come and go, but enemies accumulate.
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