Re: a new glitch

[Jon Elson <jmelson-at-artsci.wustl.edu>]

Fred (and others),

I have been using the 17-Feb-1999 version of EMC through xemc for a
few days.  It has been working well, but tonight I had a very strange
experience.  I was running a program that had been run before, but I
edited a few lines out of it to skip over drilling a hole that had a drill
bit
broken off in it (my fault).  Those cut lines are between N15 and N40.
The program appears to be correct.  It drilled 2 holes correctly, then
on the third, at line N120, it is supposed to retract in Z to make the tool
clear the top of the work by .1" (Z=0 is set at the top surface of the
work - strange practice, but that's how I often do it) before positioning
in XY to the next hole.  Instead, it started the XY move while the Z
axis was still about in the middle of the move.  This broke the drill bit
off (this time, NOT my fault).

Now, I used to have stuff like this happen when the Z axis got stuck,
as with a chip in the ball nut.  But, now I have a maxerror limit set
to .050" on the Z axis.  I checked, and the maximum cumulative
error on Z was .014", which would not have caused the broken
drill, as it still would have cleared by .086".  Fred mentioned some
changes to the synchronization of messages, so I wonder if there
might be a subtle condition under which the messages get out of
order, or are emitted from the trajectory planner before they should
be?

Anyway, this has only happened once, and I've been using programs
of this style quite a bit in the last couple of days.

Jon

N10 G01 F45 X0.75 Y0.062
N15 Z.1
N40 G01 F30 X2.25
N50 F3.00 Z-0.6250
N60 F30 Z0.1000
N70 G01 F30 Y1.25
N80 F3.00 Z-0.6250
N90 F30 Z0.1000
N100 G01 F30 X0.75
N110 F3.00 Z-0.6250
N120 F30 Z0.1000
N130 G01 F30 X1.025 Y.44
N135 Z-.36
N140 F3.00 Z-1.0
N150 F30 Z0.1000
N160 G01 F30 Y.77
N165 Z-.36
N170 F3.00 Z-1.00
N180 F30 Z0.7500
N190 F45 G49 X3.000 Y0.0000
N200 M02