wiring e-stop button

[JAZZCNC]

Another way is to make the E-stop switch interrupt the stepper motor step signals (resistor + switch to ground would do it, or better an AND gate on each), or use their enable input if they have one. That way the motors remain powered upon e-stop and make sure the axis' doesn't move. If you just cut the power to the stepper drivers then there's a very slight chance they may be damaged (but then it's an emergency after all, so that shouldn't matter?), but more importantly the motor could keep spinning for a bit due to it's inertia, or gravity with the Z-axis. I once had a power cut whilst my machine was cutting aluminium and it caused the cutter to plunge into the material and shatter - the Z-axis dropped due to gravity.

Having said that I've not bothered with any of this :whistling: ... but that's not reason for anyone else not to.

Yes this works ok for killing motion but it won't do much for you if the spindle grabs you. Plus interia will still move a powered stepper if going fast eneough.
If you want a truely safe EMERGENCY STOP then you kill power and that includes the spindle. . . It's not difficult or expensive just a few relays and some wire.
Lots of folks think because it's just Hobbie CNC then this level of safety hisn't required. . . this will be ok 99% of the time but it only takes 1% to chop your fingers off or crush your hand.!! Even the smaller steppers will crush your hand in the blink of an eye just as will the light duty trend/kress spindles slice your fingers off.! . . . His it worth the risk for £10-15 quid more.? Not to me it hisn't. . . .To use none at all is just plane stupid.!

[Jonathan]

Yes this works ok for killing motion but it won't do much for you if the spindle grabs you.

Yes of course you'd include the spindle in the circuit I described ... though that was obvious! Just don't do it by cutting power to the VFD - that's safer I guess but it's likely to break the VFD.

Plus interia will still move a powered stepper if going fast eneough.

Potentially, but nowhere near as much as if it was just disconnected.

[JAZZCNC]

Yes of course you'd include the spindle in the circuit I described ... though that was obvious!

No you didn't make it obvious and knowhere did you describe killing the spindle and thats the problem when dealing with electrics and control box's.? . . Those that know just take it for granted.!! . . Which doesn't help Folks new to CNC who just pickout bits but miss or don't understand the important bits. (Whether you think they are important or not is upto you.!!)

To have truely safe control box things need to be isolated with power killed to some items and signals broke or sent to others then a signal sent to the control software informing an E-stop as occured and then only allowed to be reset when all safety features IE: limits, E-stop etc are good and working.
An Estop when reset shouldn't allow the power or signals to be re-applied or reset the software. ( I suspect your killing enable signals would do just that without some latching mechanism built in.? Maybe you should clear this up with more INFO.?)
Yes VFD's need treating slightly different but most have provision for this with emergency stop functions built into them and can be safely shut down by killing the correct signal, infact good one's will even DC brake the spindle for you when it see's the E-stop.
Bottom line is.!!. . . The system should only re-apply signals or power when all is correct and safe to do so and then only by pushing a dedicated restart momentry switch. Which then and only then tells the Control software it's safe to allow a restart.

We could disagree all week on the best way to achive this I'm sure.!. . . But the point I'm making is that software driven is not safe and shouldn't be used if you want a safe system. What's even dafter IMO is why wouldn't you want to be safe and protect you and the machine when it cost's so little extra to do it right or safe.

[piercent]

Thought you might be interested in a new article from EAO on e-stops. It's fairly comprehensive and covers the basic background of what they are but also selection options such as design, mounting footprint, parts (actuator, sealing, front plate...), international standards and more. Here's the link: http://www.newark.com/pdfs/techartic...opSwitches.pdf as well as the main e-stop page http://www.newark.com/emergency-stop.

[Gary]

The only way is the cut the AC going to any power components like the AC inverter and the stepper drivers.
Letting software handle the e stop is totaly wrong and will get someone hurt.
if the stepper drivers take DC, then cut the power to the power supply and you should never cut the DC or this can damage the driver or any other electronics on the DC bus.
you can also send a signal into the software to tell it that the estop has been activated, but never rely on it to stop all axis.
Just cutting the clock and direction signals and the 0-10V going to the inverter is not enough.