PWN Spindle and estop

Hey all,

the Emergency Stop on Onefinity Elite’s custom variant of the Masso G3 Touch is not wired the way that Masso describes vs. recommends, but it is a Onefinity custom wiring that puts all stepper motor “Enable” wires in a circuit together. So when you press Estop, the stepper motors are disabled and stop moving.

The only allowed way to stop a spindle, including emergency stop, is to use the STOP mode of the VFD (either through VFD front keypad, Modbus command, or programmable input terminal with STOP function assigned to it). This is done either via a Modbus command, or, if the CNC controller does not support Modbus communication, by activating a programmable input terminal of the VFD that is assigned to the STOP command (some VFD also have dedicated Alarm function that can be assigned to input terminals, e.g. like described here). So the strict requirement of stopping the spindle when estop is hit (be the estop button located on the CNC controller or on the VFD control cabinet’s door) has to be implemented in a way that the estop signal triggers the STOP function of the VFD. According to the updated IEC 60204-1, a VFD’s spindle STOP command is considered as a valid Safe Torque Off (STO) that fulfils the stop category 0 requirement (so allows to e.g. safely manually change the tool in this state).

If you want to comply to IEC 60204-1, you would even need to do more:

But besides this very strict requirement, I think that simply implementing the requirement that on pressing estop, not only the steppers are halted, but also every actuator, i.e. the spindle is ensured to be stopped, which can only be implemented by sending the VFD the STOP command, needs to be done by attaching something to Masso G3’s ES output which triggers (ususally via a relay) a programmable input terminal on the VFD that has been assigned to the STOP function (or, if supported by the VFD, to the dedicated emergency Stop function according to IEC61508 & ISO13849 (see Appendix E in Omron MX2 manual).

So I think this Masso diagram shows how the VFD has to be stopped correctly:

image
– Source: EStop Wiring – Masso Documentation

As explained above, in this diagram, the “Emergency” input of the VFD means one of the programmable input terminals, assigned either – if present – to the dedicated emergency stop function, or to the regular STOP function that is sometimes implemented by disabling FWD RUN (and REV to be strict). On the Masso spindle/VFD control wiring examples, this pin is already assigned this way for regular RUN/STOP, and can be used for this purpose if you make sure that STOP cannot be reversed while Estop is active. As already mentioned above, according to the updated IEC 60204-1, a VFD’s spindle STOP command is considered as a valid Safe Torque Off (STO) that fulfils the stop category 0 requirement.