Z-axis motors are monitored?
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hi Guys,
my print bed is only placed on three points with balls for true bed leveling and can be lifted upwards. what happens if one of the three z-motors breaks. is that monitored and the printer stops? if not, the hot plate would eventually fall off if one stops and the other one moves forward. does anyone know that? otherwise I have to think about a solution.....
thx
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@ErwinH78 said in Z-axis motors are monitored?:
what happens if one of the three z-motors breaks.
that is very uncommon for a motor to break.
but no the print would not stop.
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ok i want to avoid that. any idea how to handle that?
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@ErwinH78 I would guess that using a closed loop stepper and somehow get the alarm connection to trigger a stop print.
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https://duet3d.dozuki.com/Wiki/Connecting_an_Emergency_Stop
have a cable that makes a curcuit and if the heated bed falls it disconnects and executes an emergency stop.
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@ErwinH78 said in Z-axis motors are monitored?:
ok i want to avoid that. any idea how to handle that?
I don't think there is any way of catching all eventualities unless maybe if you had linear encoders fitted to every screw and some way of monitoring those linear encoders. I'm thinking along the lines of (arguably) the most common cause which would be something like a pulley or coupling coming loose on a shaft, so the motor turns as normal but there is no movement of the shaft.
Thinking about it some more ........ how about a couple of tilt switches? Something like this https://uk.rs-online.com/web/p/mercury-tilt-switches/4553693/
One fitted parallel with the X axis and the other parallel with the Y axis. Wire each one to spare io pin and use M581 to trigger an emergency stop if either tilt switch triggers.
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@ErwinH78 Mine has four motors.
When one of them is broken as the bed get slant, the other Z motor will blocked by friction. -
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@Hiroaki
I use true bed leveling. each axis is driven separately. the bed lies on a holder with a ball. if the angle gets too big it pulls out -
@deckingman said in Z-axis motors are monitored?:
@ErwinH78 said in Z-axis motors are monitored?:
ok i want to avoid that. any idea how to handle that?
I don't think there is any way of catching all eventualities unless maybe if you had linear encoders fitted to every screw and some way of monitoring those linear encoders. I'm thinking along the lines of (arguably) the most common cause which would be something like a pulley or coupling coming loose on a shaft, so the motor turns as normal but there is no movement of the shaft.
Thinking about it some more ........ how about a couple of tilt switches? Something like this https://uk.rs-online.com/web/p/mercury-tilt-switches/4553693/
One fitted parallel with the X axis and the other parallel with the Y axis. Wire each one to spare io pin and use M581 to trigger an emergency stop if either tilt switch triggers.
tilt switches are a good idea. that would be a good solution. Thank you
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@deckingman said in Z-axis motors are monitored?:
One fitted parallel with the X axis and the other parallel with the Y axis. Wire each one to spare io pin and use M581 to trigger an emergency stop if either tilt switch triggers.
I don't think it would work easily like that. He would have to use 4 (two per axis) and under angle. Problem is if they are "parallel to the axis" they are too sensitive so you actually need to give them a slight tilt in oposite direction from where they trigger but use two (tilted oposite way). So the fault is if bed is slanted more than some angle and ball/mercury switch triggers. If you go with "they are connected in horisontal position" and error triggers as soon as they disconnect a very small safe angle will still trigger the error. But generally great idea to use ball/mercury switches for this.
much simpler imho is what most ppl use - springs with balls pulling bed to spring not allowing bed to slide off three balls
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use 2 til switches connected on opposite planes?
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@Veti said in Z-axis motors are monitored?:
use 2 til switches connected on opposite planes?
you print a holder to hold 2 tilt switches tilted in different position like this
so if bed gets tilted in any direction "too much" one of them will trigger. just connect the "open" sides in parallel and you have a trigger. changing the amount both are tilted gives you the allowed tilt for the bed.
now, I would not feel safe using these on the heated bed taking into account how much mercury expands with heat.. you might want to use ones with a small metal ball inside.. work similar, much cheaper, won't be as affected by heat
e.g.
https://www.aliexpress.com/item/4001036165133.html
https://www.aliexpress.com/item/4001303798529.htmlwatch out only there are the one with springs, I don't think those work ok for what you need
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I wouldn't have though that it'd be too difficult to make a tilt switch that work in this application. Something like a small square plate with micro-switch at each side and a heavy(ish) steel ball. If the plate tilts, the ball rolls and triggers one other micro switch. Fix the thing under the bed, connect one side of the first switch to gnd, wire all the other switches in series, and connect the last one to an io pin and use that to trigger an emergency stop.
Personally, I couldn't be ars*d but it'd work I reckon..............
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Can you make electrical contacts between the balls and the bed? When contact is broken, trigger stop.
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A more costly way is to use, for example:
Write software for the Adafruit Feather M4 Express to use the gyro on the Adafruit LSM6DS33 6-DoF Accel + Gyro IMU - STEMMA QT. Use it to trigger a pin on the duet.
https://www.adafruit.com/product/3857 and https://www.adafruit.com/product/4480
