E-Stop Button

[widgitmaster]

Question,
What devices should and should not be disrupted when the E-Stop button is pressed?

Widgit

[Karl_T]

You'll likely get various opinions. When I worked for a Fortune 100 company, we used to schedule design reviews just for this subject.

In general, a machine stop button is always located next to the E-stop. It is to be used in all but emergency situations. Estop is then assumed to be: The machine is broken, something is seriously wrong. In general Estop then killed power by dropping a NO contactor to any device that caused machine motion but not to controllers, computers, displays, etc. One big question was always brakes and braking. The guidline here was: assume somebody screwed the controller program - you still need to be able to kill it. We often installed brakes that were held open by power; drop power and it comes to a screaching halt.

Karl

[Al_The_Man]

Originally Posted by widgitmaster Question, What devices should and should not be disrupted when the E-Stop button is pressed? Widgit

There is the mandatory requirements as laid out in the NFPA79 as related here http://www.cnczone.com/forums/showthread.php?t=57888
These are effectively done in current industrial applications by a Safety Relay.
The primary interest is operator safety and Machine damage prevention.
These should be looked at first.
There are rare occasions when immediate stop is not the best approach, for example, if you have a very large spindle that takes several seconds to wind down if the power is removed, it may be better to leave the power on the spindle so a controlled fast deceleration can take place before power removal.

In a home hobby built machine, make a list of the things you want to achieve when an E-stop is pushed, and go from there. e.g. look at disable drives as well as remove power.

The hardest button to find on a machine is always the E-STOP.
Al.

[Guldberg]

This is what i plan to do. Cut the power to the stepper drivers and either the pwm signal to the digispeed board that controls the vfd or the 0-10v coming from the digispeed. This will stops the motor faster than when freewheeling assuming the logic in the VFD works:-) Something had to be seriously wrong though or else ill just hit the reset switch to make mach 3 switch of all outputs