Plausiblty check on feedrates
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14 Apr 2025 10:05 #326261
by RotarySMP
Plausiblty check on feedrates was created by RotarySMP
This weekend I again trashed a tool (luckily only a drill), but using an F50 (Expecting G94 50 mm/min) while in G95 mode. (at about 38:45...)
I have heard the some other controllers allow setting an error trigger if the feedrate exceeds a set threshold. I went searching if LinuxCNC offers an option to set a max feedrate it will error out on in G95 (would also make sense to have a min feedrate error message in G94, as I have also had F0.01, and then wondered why the machine didn't seem to move). I didnt find these options. Am I missing something or they really dont exist?
Cheer,
Mark
I have heard the some other controllers allow setting an error trigger if the feedrate exceeds a set threshold. I went searching if LinuxCNC offers an option to set a max feedrate it will error out on in G95 (would also make sense to have a min feedrate error message in G94, as I have also had F0.01, and then wondered why the machine didn't seem to move). I didnt find these options. Am I missing something or they really dont exist?
Cheer,
Mark
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- spumco
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14 Apr 2025 13:21 - 14 Apr 2025 13:44 #326273
by spumco
Replied by spumco on topic Plausiblty check on feedrates
Mark-
My Fanuc 21 will alarm if you program a feedrate which exceeds the machine's capability during G94 or G95. There are no settings; the control checks commanded RPM and FPR, calculates the IPM (or m/m) and vomits if you exceed the ceiling. In my case, this is about half the max rapid rate.
There is no check to see if the commanded feedrate is a good idea - only if it exceeds the MFGR's max.
In your case you could probably set a ceiling which corresponds with your coarsest desired thread plus some headroom for accel... but that is probably still fast enough to crash a drill.
EDIT
Is there any reason for you to program in G94? On my Fanuc lathe the only time I need to program in G94 is during live tool work or when I need to position the turret for the bar feeder with the spindle stopped.
Maybe just stop using G94 on the lathe?
My Fanuc 21 will alarm if you program a feedrate which exceeds the machine's capability during G94 or G95. There are no settings; the control checks commanded RPM and FPR, calculates the IPM (or m/m) and vomits if you exceed the ceiling. In my case, this is about half the max rapid rate.
There is no check to see if the commanded feedrate is a good idea - only if it exceeds the MFGR's max.
In your case you could probably set a ceiling which corresponds with your coarsest desired thread plus some headroom for accel... but that is probably still fast enough to crash a drill.
EDIT
Is there any reason for you to program in G94? On my Fanuc lathe the only time I need to program in G94 is during live tool work or when I need to position the turret for the bar feeder with the spindle stopped.
Maybe just stop using G94 on the lathe?
Last edit: 14 Apr 2025 13:44 by spumco. Reason: and another thing...
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14 Apr 2025 15:15 #326288
by RotarySMP
Replied by RotarySMP on topic Plausiblty check on feedrates
Thanks, Andy also made that suggestion. You are right, I am kind of used to thinking in G94. Need to reprogram my brain.
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