Re: Rigid or flexable couplings plus limits

>
> No I was trying to test the limit switch when I hit the connector

to

> the encoder before I could hit e- stop it crashed. What I need to

do

> is fix the problem and if it so happens again not total everything
> out with ball screw snapping. I don't trust the wire connector

after

> this one failed. I still have a problem with the limit switch the
> lights on the interface board light up when a switch is trip but

the

> servos won't stop turning. I just would like to reuse the ball

screw

> again and if it runs away, have more than a switch for fail-safe.
> Thanks Randy

One of the nice things about his hobby and this list is that you are
free to build and do things any way you want to. If you wish to
devise a way to protect your shafts during a full tilt runaway rather
than prevent the runaway then go for it.

A properly connected limit/safety switch system so that it requires
all of the safety devices to conduct (normally closed switches) and
refuses to provide raw DC power to the motors unless all safety
devices (limit switches, shields, e-stop switches,) are operational
and will fail if a wire or connection is bad, is the accepted method
of preventing serious crashes. It needs to be designed so that even
a momentary activation of any safety device will cause DC to drop out
and stay out until manually reset.

In addition to hard limit switches there are some other methods to
sense a run away but you still have to be able to shut down the raw
power to the motors to stop the motion.

As for solid VS flexible couplings: Their flex is designed to be in
the radial direction to allow for slight misalignments but to have no
measurable flex in the rotary direction. Their flex is in one
plane. Had you been using flexible couplings they MIGHT have twisted
in two prior to twisting the shaft, but could easly have applied
enough torque to have the same results as the solid ones.