Re: Re: G92

>    From: "pcfw" <pcfw@...>
> Subject: Re: G92
>
> Ray Henry <rehenry@u...> wrote:
> > Tom Kramer of NIST, the author of the EMC's interpreter describes
> > the effect of a g92 this way, "To make the current point have the
> > coordinates you want (without motion), program G92 X- Y- Z- A- B- C-
> > where the axis words contain the axis numbers you want."
> > 
> > So the critical notion here is that the current location of the tool
> > is the point that will take on the value that you set using the g92
> > command.
>
> N1520 G02 X-17.5 Y10 I0 J9.5
> N1530 G00 Z5
>
> N1540 G92 X110 T1 (dia 10mm)
> N1550 G01 Y127 X-11.5
>
> So at N1540, the x-coord of the current tool position had been set to
> x=110, which means that the program zero is 110 units to the left of
> the current tool position.
>
> So N1550 should send the tool to x=-11.5, that is, 110+11.5=122.5
> units to the left!
>
> The simulation shows the tool moving approx. 100 units to the right
> instead!
>
> Is there another interpretation of G92?
>
> Anyone else using cncsimulator?
>
> Thanks

Peter

Well, no I don't use cncsimulator. I use the backplotter that Paul and I
wrote for the EMC but I don't see how that should affect the world of
machine movement.

I ran your code through EMC with the following small mods because I did
not have the position where the arc in N1520 started. I also commented
out the T1 because the EMC does not work like that and added the G20 to
run in mm rather than inch.

(test program from pfcw)
N1510 g20 g0 x0 y0 z0
N1520 G01 f15 X-17.5 Y10 (I0 J9.5)
N1530 G00 Z5
N1540 G92 X110 (T1 dia 10mm)
N1550 G01 Y127 X-11.5
N1560 M2

It does set x-17.5 in machine coordinates to 110 in relative position.
From there it moved in about the same direction it was traveling before
the g92.

I still get confused about direction of travel because it seems so much
like an operator's point of view kind of thing. In backplotter the tool
appears to move around a stationary part while with my minimill the tool
sits still and the part moves around the tool. With backplot you can
change the direction of each axis with respect to the others in order to
match an oddball machine and rotate the whole thing to view the part from
any angle. Perhaps cncsimulator has similar options.

What I often do is go to mdi and command a short move, or jog a bit in
manual so that I can be certain which direction +x,y,z is in the current
view.

Hope this helps

Ray