Re: E-Stop Revisited

The whole subject of stops seems subjective.

If you want a program pause for inspection, or chip removal, then
a 'finish command then pause' is a good option. This would allow the
program to pick up exactly from the last control point.

A 'fault' stop might be a motor temperature sensor or coolant low
sensor that would do something similar to the above pause and wait
for the fault to be cleared.

The emergency stop is often a 'catastrophic failure prevention' and
just kills everything and the the program needs to be re-started or
re-joined after the problem has been cleared.

Hearing the cutter banging into the lathe chuck might be such a
catastrophic failure. if you put in 10.000 instead of 1.0 and the
feed was going to destroy stuff, you probably already lost the part
as well as zeros.

I have home switches and end switches. the end switch is an e-stop.
there is just no reason for the table to go past zero for any reason.

I'm installing a manual pause for tool change or chip clearance or
what-not.

From my readings, E-stops are tailored to your specifc needs, ther is
no one correct solution.

Dave










--- In CAD_CAM_EDM_DRO@yahoogroups.com, "caudlet <info@t...>"
<info@t...> wrote:

> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Peter Cruickshank
> <crankshaft_sg@y...>" <crankshaft_sg@y...> wrote:
> > Hi;
> >
> > Ok, what's the conclusion on the E-Stop issue, should the big red
> > button cut power to everything, or is s soft-stop good enough !
> >
> > I know that there are different opinons on this, but for the
> general
> > hme hobyist CNCer with a Sherline 5410, What's the

recommendation ?

> >
> > Cheers
> >
> > PeterC
>
> Absolute e-stop is pretty easy to accomplish. My e-stop button on

my

> controller and on the machine breaks a circuit that holds in the
> contactor between the DC supply(s) and the motors. The contactor is
> wired in a latching configuration so that voltage is required to

keep

> it "pulled in" and activated. I have two sets of limit switches.

One

> set is wired to perform Home functions. The others are wired in
> series (Normally closed) and control a relay that will cause the
> contactor to open if ANY of the switches are tripped, a wire comes
> loose or there is a component failure in the circuit.
>
> The need for e-stop with a small tabletop unit and small steppers

is

> reduced. It's not like the machine can cause you serious harm if

it

> goes uncontrolled. I am running a small engraving table that does
> not have e-stop or limit switches. The only thing I miss is the
> ability to do a return to home and zero the controller function.
> MACH1 allows you to do that. My big table is a different story.

It

> has enough speed and power to cause real damage and I have limit
> switches all over it!