M122 MaxReps
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@T3P3Tony Yes, this report is after homing and after probing and leveling the z axis. The report looked identical before homing and leveling as well, except for some minor deviation in variables.
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How fast are you homing now? Have you tried increasing the speed yet? How fast do you want to go?
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@Phaedrux 30mm/s on x and y for coarse homing. 5mm/s on z probe for coarse homing. My main issue is the z axis, I would like that to move a bit faster, but I don't want to end up crashing the bed. I was considering adding some type of inductive probe to the machine and coarse homing fast towards the inductive probe, and then lowering the speed after it activates the inductive probe. I would like to decrease the total time to home either way, and get it as fast as I can while still having it home reliably every time.
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@Surgikill said in M122 MaxReps:
@Phaedrux 30mm/s on x and y for coarse homing. 5mm/s on z probe for coarse homing. My main issue is the z axis, I would like that to move a bit faster, but I don't want to end up crashing the bed. I was considering adding some type of inductive probe to the machine and coarse homing fast towards the inductive probe, and then lowering the speed after it activates the inductive probe. I would like to decrease the total time to home either way, and get it as fast as I can while still having it home reliably every time.
This may or may not interest you, but I had a similar problem. That is to say, my Z axis is heavy but also has a potential travel of >750 mm so homing at a low speed could take several minutes if a tall part was last printed. But to move the Z axis at faster speed means that I can't reduce the motor current, so in the event of the probe failing to trigger, I'd risk a serious crash. My solution was to fit a simple micro-switch on a swinging arm such that the bed can trigger the switch as it rises after which the arm holding the switch will swing upwards so that the switch doesn't get crushed. From switch trigger to Z=0 is about 110mm. So using conditional gcode, I have a loop which checks the switch, then if it isn't triggered raises the bed 100mm at full motor current rapidly. The loop will repeat until the switch triggers. This is part of my home Z macro so the bed will always move rapidly until it is within 10 and 109 mm of the bed, after which normal homing at lower speed and reduced motor current takes place. The length of the arm and it's position could be altered if one wanted to get closer at high speed.
You can see it in action as part of a longer video I made. This link with the "t=210" should take you straight to it (it's about 3 1/2 minutes in from the start). https://www.youtube.com/watch?v=OWmsIK4qbZ0&t=210s
EDIT. That fast jog happens at 900mm/min(15mm/sec). The course homing of Z is at 300mm/min (5mm/sec) and the second, fine homing of 5mm happens at 60mm/min (1mm/sec). So 750mm of Z travel used to take 150 seconds or 2 1/2 minutes at 5mm/sec and now it's about 50 seconds - obviously a lot less for shorter travel distances.
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Those speeds aren't crazy by any means. For Z you can do a fast first probe and a slower secondary.
Or you could add optical endstop for a fast home. The optical flag can pass through the switch body, so it doesn't need to be at exact Z0. Then use the probe for a second homing pass.
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@Phaedrux said in M122 MaxReps:
.............. Or you could add optical endstop for a fast home. The optical flag can pass through the switch body, so it doesn't need to be at exact Z0. Then use the probe for a second homing pass.
Wish I'd thought of that before I mounted a micro-switch on a swinging arm.
But I'm planning a fairly major re-build so I'll incorporate that idea into it - thanks.
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@deckingman said in M122 MaxReps:
Wish I'd thought of that before I mounted a micro-switch on a swinging arm.
I wanted to keep my switch - simple, reliable, existent - but still stay safe of the nozzle touching the bed during a first, rapid approximation. Works.
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@Phaedrux That's pretty much what I was thinking with the induction probe. Not sure if I can pull it off with an optical endstop due to tolerances. I'm guessing this would just go to a regular z-endstop? Do you know where I could find the requisite g-code for something like this?
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@Surgikill said in M122 MaxReps:
Do you know where I could find the requisite g-code for something like this?
For what specifically?
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@Phaedrux Basically a secondary homing switch. I'm guessing in my homez.g I could just home to the secondary switch, and then go straight into a z probe?
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Yes in that case you could do it sequentially.
G91 ; relative movement
G1 H1 Z-300 F600 ; home Z with switch
G1 Z5 ; raise Z
G1 X150 Y150 ; move probe to center of bed
G30 ; probe bed -
@Phaedrux Awesome, thanks.
So is the MaxReps feature in M122 gone? Or has it been moved somewhere else?
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No idea about maxreps. Never paid any attention to it.
