EMC Internal E-Stop Drive Stopping

[electrosteam]

I am new to CNC with a stepper driven mill acquired without any external E-Stop buttons and currently being re-commissioned.
I will implement external buttons.

My search of the EMC documents that came with the machine and this forum provided no detailed description of the EMC sequence of actions on the declaration of an E-Stop.

On E-Stop does EMC:
- instantly stop all drive pulses,
- ramp the drive to zero speed at the maximum deceleration rate and then stop pulses,
- other sequence ?

If the drives are ramped, does EMC delay asserting the E-Stop output until the drives are stopped ?

Thanks in advance,
John.

[Alexthehun]

From my experience, emc drops pulses immediately and also the enable pin to the drives. No rampdown.
I would advise against this being your main way to do an emergency stop: if the reason for the stop is a software/computer problem no amount of estop pressing is going to stop your runaway machine!!
I have e-stops wired such that they drop the power to the drives and the router(mill in your case) as soon as any of them is pressed. (done with a latched relay: to be enabled first ==you now know the machine is armed! The e-stops are in series with the relay power so as soon as one activates the power is dropped and will not come back until the enable switch is used: also deals with short mains interuptions which mess up your cut)
My limit switches do something similar with the only difference that they allow an overide switch to re-apply power and jog the gantry away from the offending limit switch.

regards

Alex

[electrosteam]

Alex,
Thanks for the comments.

As previously stated, I will have external E-Stop buttons and these will provide absolute power isolation,

The question in my mind is, should the external power removal be delayed a short while ( 1 sec ? )to give EMC a chance to stop the motions first ?

My drivers are Leadshine MD882 and their application engineer confirmed that asserting /ENABLE at the drivers instantly removes pulses.

A Bridgeport sized machine with a heavy set-up at full speed on the X-axis could coast quite a distance without pulses.

John.

[samco]

imho - the external estop chain should run through the drive power supply and power down everything that can cause motion. there should be no delay in this. if your worried about the machine coasting - you need to come up with an external way to stop the motion. maybe a brake or shorting out the windings or....

In my conversion of a HMC - the estop drops out all the relays that run the hydrualic, spindle, servo drives and such. It is a hard wired thing - no computer involvment. The computer knows it happened - and can re-enable the estop loop once the BRB's are back out.

my 2 cents...

sam