Sage:
This is a question of understanding machine and work coordinates.
Your work coordinate displays the distance from the last zeroed position. So in your case you zeroed
the Y work coordinate when the machine coord was 0.
So the work coordinate and machien coord read 0 together. No now you home, when the switch was hit
the Machine coordinate got set to your offset, in this case 6.4065 , the extra being the distance the
axis took to declerate after hitting the switch. That machine coordinate reading at that point then
is the distance from where your currently at..to what your machine considers "Home" for the Y axis.
Now the Work coordinates instantly changed as well, because its job is to report how far it is
from the last zeroed position. The last time you zeroed you were equal to the machine coordinates.
So when the machien coordinates changed, your work coordinate display had to as well. Your work
coordinates now have to display the distance to the machine coordinate of 0, which you zeroed it to,
so it now displays 6.065 as well. Had you zeroed at a machine coordinate of 10, your work cordinate
would have changed to 16.065 ..
Consider this as an important feature for checking accuracy.. Lets say you zeroed in the middle
of your table for a job. Half way through you suspect you lost steps. So you hit pause. It stops at
a reading of 2.345 on the Y. You note the position and hit ref all. If the system homes and the machine
coordinates are accurate ( you havent lost steps), you will not see any change in the work coordinate DRO's
when the switches are hit. This is beacuse the machien coordinates didnt change, they were and stayed
accurate. BUT, lets say you hit soemthign in the job, and you Y is .5" off. SO when the switch gets
hit the machien coordinate zero and changes by .5, ( the distance it lost since last home). As it changes by
.5, so too muct your work coorindate in order to repair the lost units. SO now you command it to
go back to 2.345 where you pasued and youll notice your now .5" away from where you paused. You have
repaired the lost steps. The rest of the job will now be accurate. Homing is good not only for starting a job
over bu t for verifying that you have lost steps, just home and see if the DRO changes, if it doesnt you
were accurate, if it does, you were off, but no longer are.
I dont know why the guys dont have it startup with the last known coordinates, it can probably be
configured to do that, but thats out of the scope of the printer port itself, more a question of
how mach4 works.. and Im woefully inadequate to that task. I havent used Mach4 other than to code up
a plugin for it. I will be designing my laser engraver aorund M4 so over time Ill know more about
its care and maintenace.. and probably figure out where to set startuyp behaviour.
, but the best
best for any machine with home switches , is to do a refall immediately after every startup..and
whenever you think perhaps youve lost steps..
Art
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