I think the main thing about estop is that
A. When hitting E-Stop all movement stops ASAP.
B. There is no chance things start moving again after the E-stop button is
reset.
Typically a separate "start" button must be pressed before things may
start again.
I recommend that these circuits be implemented in hardware. see therac-25
for how things could go wrong. https://en.m.wikipedia.org/wiki/Therac-25
I have seen machines that leave drives powered during estop but they have
an enable loop that is part of the "hardware" estop loop. (the more modern
machines tend to follow this pattern.) I have seen machines that completely
cut power to all drives as part of the estop loop. It is up to you to
engineer the appropriate way of handling this.
I make these decisions by imagining that if my arm were caught in a
particular machine which way of doing it would result in less injury.
Big machines with lots of momentum would probably cause less harm with
controlled powered stopping... cutting power on those drives may result in
more harm. In a home machine with sketchy Chinese drives... cutting all
power might be ultimately safer it all depnds.
My father lost a hand in the 70's because he reached into a machine that
did not follow this e-stop protocol. It is serious business even for small
machines. Please take it seriously especially if people other than
yourself will be operating them.
-Curt
On Sun, Aug 1, 2021, 3:47 PM Feral Engineer
wrote:
> With safety relays, they require an external reset after being released.
> Every machine tool I've been on in the last 20 years operates in this
> fashion.
>
> Release estop
> Press "power on" or "drive enable" button to reset the pilz
>
> Phil T.
> The Feral Engineer
>
> Check out my LinuxCNC tutorials, machine builds and other antics at
> www.youtube.com/c/theferalengineer
>
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>
> On Sun, Aug 1, 2021, 3:14 PM Nicklas SB Karlsson wrote:
>
> > Anyone have any experience or knowledge with emergency stop circuit?
> >
> >
> > Connected a special safety relay breaking the 24 volt power supply
> > driving the relays today. Then emergency stop have been pushed it have
> > to be reset before relay is switched on again.
> >
> >
> > Nicklas Karlsson
> >
> >
> >
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