dave asked;
{Dear readers, come with me down the garden path a bit ...
If one does
T1 M6
G43 H7 (note that the H# is not = the T#)
T2
G43
(what H# TLO value does LCNC have at this point?)
If G43 w/o an H word was a syntax error, this would not be an issue as
we'd stop at the G43 block.
But now we have G43 w/o the H word is not a syntax error - so what will
LCNC do?
(I'm not near a running LCNC machine to test this on as I write this)
Is the operative G43 offset now:
1) The TLO value for H register #7?
Since this is already the active TLO value?
One can argue that this would be correct, as turning on G43 when G43 is
already active should be a no-op.
2) The TLO value for H register# 1?
Since the last Tn M6 pair in a block had T=1?
3) the TLO value for H register index 1?
Since 1 is the currently mounted tool #?
4) the TLO value for H register 2?
Which was the last T# called for by the gcode?
This is an example of why I dislike it when CNC Controls try to "help"
by providing implicit default values.
"The path to hell is paved with good intentions..."
Dave}
h7 . as g43 is a modal command , g49 cancels g43. in this example g43 was
never turned off it will be active until g49 is issued, and as the last
known height was h7 it was never turned off either . my confession i have
not played with ngcgui as i have excellent cam available so i do not know
the code this is generating, agreed logic would dictate if a g43 with no h
offset were programmed one would expect a syntax , unfortunately many
commercial machines will accept this coding and the inevitable crash will
occur , this is not just a linuxcnc issue . as to previous statements of
machinist vs router operator. as a machinist i would never use the work
station offset as if this is modified any mistake will be in every
successive part, not only is this practice frowned upon i have seen people
lose their jobs when 20000 dollar parts were scrapped. also modifying the
work offset affects EVERY tool , (further bad juju) , however understanding
the limits of many of us on the list without toolchangers and holders i use
the touch off method, while not perfect it has sufficed for anything i do
at the house , i would NEVER allow that in a production environment , in
fact i only allow 2 methods in the shop 1 touch off a block , 2 use a
toolsetter , anything else is just asking for the inevitable crash ,
especially when changing shifts ( dont ask how i know ) :)
jeremy youngs
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