PWN Spindle and estop

[Aiph5u (Aiph5u (not affiliated with Onefinity))]

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.

@Aiph5u

On the Masso-G3-Touch-based Onefinity Elite Series, the Emergency Stop Button(s) are directly connected to the “Enable” pins of all motor drivers (see motor driver specs) (besides being connected to the “ESTOP” input of the Masso G3 Controller, which in turn activates its “ES” output that controls the two relays inside the Elite Power Supply Box which interrupt the power supply sockets for “Router” and “Vacuum”. Note: The DC power supply sockets for the stepper motors in the Elite Power Supply Box are not powered off when hitting Emergency Stop Button!)

See also Elite stepper motor and driver specs for “Enable” and “Alarm” pins.

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:

@Aiph5u

A category 0 or 1 stop safety circuit has to be wired in a way that after the Emergency Stop has been triggered, the setup cannot be restarted again without having pressed a dedicated RESET button. Therefore for an emergency circuit, you use a (ISO 13849) Safety relay such as a Omron G9SE. See here for a circuit diagram that describes how to wire it.

That’s why on VFD control cabinets, you have usually in the front door:

1. A manual power switch (can be a magnetic contactor that will prevent to be on when power comes back after a power outage) for powering up the entire setup. Don’t cut power to the VFD when the VFD is not in STOP mode!
2. A red/yellow mushroom-shaped Emergency Stop switch that is wired to the safety relay circuit, that will lead to a Safe Torque Off (STO) of all motors and actuators of the entire CNC machine
3. A reset pushbutton without which it is not possible to restart the motors and actuators of the system after Emergency Stop was triggered.

You can see these three components in the back of the door:

@Aiph5u

you can buy a control cabinet assembled and configured ready-to-use:

• Electrical Cabinets - Mechatron

Unboxing video:

CNC Finale: Automatic Toolchanger Spindle Install & Testing

Image: Shown is a full-blown control cabinet with VFD, circuit breaker, safety relay (red), and EMI filter on the left, and the pneumatics system for the automatic tool changer system of the ATC-8022-42-HSK25 2.2 kW 42,000 rpm water-cooled spindle on the right (and additional air tube (blue) with valve retrofit by video author which also wanted workpiece mist coolant – described in the video). On the back of the door you see the back of power switch, emergency button and reset button. Note the thick earth line that connects door to the rest of the cabinet.

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:

– 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.