stepper motors and e-stop
- Thread starter isiah_s
- Start date
It will? I have not played with steppers before. The issue is it could crush a person's hand and if that started happening, they hit e-stop I am worried the motor would lock leaving his hand being crushed. You are saying steppers dont lock when the drive stops applying power?
g.mccormick
Lifetime Supporting Member
If you remove power, the motor will not be "locked". Now that may or may not allow you to manually move a device. There could still be mechanical reasons that would not allow you to physically move the crushing device. I would say that your main objective should be to make it as impossible as you can to have a person be able to get into a situation where they can be crushed in the first place. Light curtains, gate interlocks, two hand stattions, lazer scanners, etc, etc, etc, etc.
I am still gathering information but everyone is saying it wont move after it has no power. You could be right and everyone else is wrong but I would not want to depend on that. You are definitely right about safety circuits, the best way to solve this problem. My coworker suggested an emergency reverse in addition.
Thanks a lot.
jstolaruk
Lifetime Supporting Member
Is there a brake involved? Motion under emergency conditions is not advised. Proper safety circuits will detect the operator's hand before it reaches the pinch condition so that harmful energy can be removed. In this case, a light curtain or safety mat?
No physical braking. Drive is given a stop command. A light curtain is what I will use, still reviewing the drawings now, also a safety circuit on the electrical and maintenance panels.
mendonsy
Member
Is the stepper motor using a gear reducer?? Gear reductions will often prevent you from turning the output shaft even when power is not applied because of the high ratios involved.
janner_10
Lifetime Supporting Member
No offence, but there seems to be a high degree of guessing and hoping.
If there is a risk someone can get their hand crushed, then you need to consult with someone who is experienced in carrying out risk assessments and designing safety functions.
It doesn't sound like you are at that level.
If there is a risk someone can get their hand crushed, then you need to consult with someone who is experienced in carrying out risk assessments and designing safety functions.
It doesn't sound like you are at that level.
"If there is a risk someone can get their hand crushed, then you need to consult with someone who is experienced in carrying out risk assessments and designing safety functions."
+1 for machine safety risk assessment
Hazard reduction and emergency stop are two different aspects of machine design.
+1 for machine safety risk assessment
Hazard reduction and emergency stop are two different aspects of machine design.
It won't move if you remove Drive Commands. It will move if you remove Power. It needs electricity to hold itself in place.
+2 for machine safety risk assessment.
If you're looking at a way to handle the situation where someone has already got their hand crushed in the machine, you're doing it wrong. Back it up a couple of dozen steps and find a way to prevent that from ever, ever being able to happen.
If you're looking at a way to handle the situation where someone has already got their hand crushed in the machine, you're doing it wrong. Back it up a couple of dozen steps and find a way to prevent that from ever, ever being able to happen.
Geoff White
Member
If there is no current at the stepper motor it will not have holding torque. The rotor will "stick" to one of the poles when unpowered but it is only a small torque relative to the operating torque.
The idea of course is to prevent them from being able to get their hand stuck in the first place.
The idea of course is to prevent them from being able to get their hand stuck in the first place.
Nope, they don't. How do I know this? I've got a Rostock 3D printer (which is a delta style printer) here at home. With the power off, I can move it at will.
As a side note, steppers make dandy generators, the display on the Rambo controller on the Rostock will light up as I raise and lower it by hand. Since it is generating, and supplying power to the Rambo board (the 3D printer's controller), cutting it loose entirely from a load would make it even easier to turn.
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Thought I'd post this to help other's out :) Any further questions, don't hesitate to ask.
Credit to Keithkyll for his advice!,
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