Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: Klaus on May 01, 2020, 10:06:58 PM
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How do I pause a Mach3 gCode run
I need to stop a job after a few hours and come back to it later.
What is the best way?
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Hi,
to pause a job in such a manner that it can be restarted without losing steps you must use <FeedHold>.
If you use <Stop> the machine will crash stop and the contents of the motion buffer are aborted and so if you attempt
to restart the result will be inaccurate due to the loss af motion commands that were in the buffer at the time you <Stop>.
Typically the motion buffer will have anywhere from 100ms to 500ms of motion commands therfore any loss of those
commands will usually result in lost steps.
<FeedHold> on the otherhand will carry on exexcuting the buffered motion commands, typically 100 to 500ms worth of movement,
until the motion buffer is drained. If you then <Stop> no motion commands have been lost.
To restart a program at some point within the program is perfectly possible but the procedure is demanding and exacting.
It relies on Mach doing a 'dummy run' to the point in the part program that you wish to restart so that Mach knows the
correct mode in which to restart and then it will make a preparatory move to the restart location. More jobs have been wrecked,
tools broken and machines crashed with this preparatory move than any other operation in Mach3.
If you are prepared to study the RFH, Run From Here documentation, and follow it precisely it works fine.
It takes a few practice runs and disasters before the procedure sinks in and woe betide you if you get distracted duing a RFH
procedure.
It may be possible that if you <FeedHold> a program you can walk away from your machine and come back several hours
later and hit <CycleStart> and the job will restart without all the palava of RFH. Some motion controllers, and some PC's
do not like sitting around idle for any great length of time and so it might transpire that after an absence of several hours
you HAVE to do a RFH.
I use an ESS and Mach4 and run it on a very low-power dual core Atom single board PC and I can happliy leave my machine
for hours or even days in idle state and suffer no loss when executing <CycleStart> after the absence.
Craig
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Hi Craig
Thanks for a very good explanation of this, much appreciated.
I will try to do some experiment with your sugestions.
Cheers