Re: EMC Homing Switches

[Ray <rehenry-at-up.net>]

On Sun, 23 Jul 2000, Dan wrote:
> I use the home switches as a reference at the beginning of a run.  Usually,
> they are where 0,0,0 is, but not always.  Things can get tricky if you are
> running a program that uses G54 through g59.3 fixture offsets and you abort in
> the middle of a program.  Things can also be flaky if you call out a G92 Xxxx
> Yyyy at the beginning of a session that isn't  X0 Y0.   When you fire up the
> next session and then home to the switches, EMC will revert back to the
> previous sessions G92 coordinate call.  Try it out.  Open EMC,  then at a
> random position go into MDI mode and type "G92 X5.0 Y5.0".  Shut EMC down. 
> Reopen EMC and home to the X and Y switches.  The display on the screen will
> show X5.0 Y5.0.  

I had to try this and yes it does.  G92 writes those values into the *.var
file that you are using.  After I executed the line above, the relevant
lines of my var file looked like:

Axes offsets for G92
5211	-5.000000
5212	-5.000000
5213	0.000000

when EMC restarts, it will read those variables as the initial settings
for startup position.  If there is a value in the HOME = variable that
value will be added to the g92 value when the axis is homed.

But then if you execute g53 x0 y0 z0 it will move to the g92 position
regardless of the value in the ini HOME variable.

Ray