Enable pins on Stepper driver, are they required?

[Robin Hewitt]

Doesn't the EN pin free the motor so you can do a bit of manual positioning? If so it makes for a crummy emergency stop because there is no braking. OTOH if your drivers have no pattern memory and revert to a set home pattern when you switch on, then EN would be a good option if you wanted everything to cool down while you replaced a broken tool, went out to buy milk, fags etc.

[Neale]

I hadn't thought of the possibility that the driver might remove motor voltage if not enabled. I can't see anything specific about this in the manual - going to have to actually test the hardware. I take the point about motor braking but I was influenced by a number of comments on this forum that you should not trust motion controller firmware for safety-critical functions like e-stop. Not entirely sure why not as we trust it to move each axis correctly and recognise limit switch inputs but there we are. So IF you don't trust the firmware and IF chopping power to the drivers will not have immediate effect, how do you stop the machine quickly? I'm particularly interested in avoiding damage if one of the slaved axis motors stalls. The manual does say that on stall detect, power is removed from the motor.

[Clive S]

I agree Neale the beauty of stall detect is that you have all the drives connected together so that if any one drive stalls they all stop and that will stop the gantry from destroying itself.

[magicniner]

Not entirely sure why not as we trust it to move each axis correctly.

We assume it will and we hope it does and that is usually the case but the E-Stop is there purely because we should be aware that the worst can happen and the way to make sure everything is guaranteed stop if we want it to is to have the best failsafe we can devise, and that is not the systems which will have failed in the worst case scenario.

[magicniner]

On the actual function of enable pins, a useful way to use them is to position work on the machine, jog the tool to your desired reference point, hit the disable switch and jog the controller to the matching position on the path display without moving the steppers. You could manually position the machine while the steppers are off if it has handwheels,

- Nick

[Robin Hewitt]

There is a big difference between PAUSE and emergency STOP. If everything goes to hell in a handbasket I usually retreat to the safety of the mains socket and kill the power there. This does preclude braking the spindle at the VFD but it is comforting to know everything will soon come to a halt without removing any more fingers.
Pause OTOH implies a restart so it is purely a software driven thing which involves looking in to the G code future and creating a plan to get everything back up to speed. A well written pause is a joy to behold and well worth playing with

[Clive S]

Pause OTOH implies a restart so it is purely a software driven thing which involves looking in to the G code future and creating a plan to get everything back up to speed.

Why should a pause require a restart as you should just be able to do a resume with no problems. A pause is generally a controlled stop as apposed to an emergency stop which always requires a rehome etc.

[Robin Hewitt]

Why should a pause require a restart as you should just be able to do a resume with no problems. A pause is generally a controlled stop as apposed to an emergency stop which always requires a rehome etc.

Sorry I should have said UNPAUSE. I award stepper motors a speed at which I can start or stop them without losing steps. Once beyond that speed pausing and unpausing become interesting. It's tricky keeping everyone in synch. I have written it twice, once in Z80 assembler and once in C.