Safety enclosure & Emergency Stop

Hello,

I am currently designing a safety enclosure for a small CNC machine that needs to have one main feature: if the doors are open, the user shouldn't be able to start a G-code or turn on the spindle. The machine should also go into E-stop mode if the door is opened during a job. I would like nonetheless the machine to be able to perform certain actions when the doors are open for ergonomic reasons, i.e. manual jog allowed, or using a tool measure length probe.

I have two ideas in mind, both with advantages and drawbacks:

1. Place a switch on the door frame, wired in series with the main e-stop switch. The advantage is that it will be reliable and work for the scenarios mentioned above, except that I won't be able to control the machine manually with an open door.

2. Place a reed switch or a sensor on the door frame, wired to an input of the Mk3/4 controller. I modified the OnStart and M3 scripts to check the state of that pin before starting a job or turning on the spindle and it works well, but the issue here is: how to stop the program while it's running if the door is suddenly opened?

Lastly, am I missing another possibility to achieve this?

If someone already tried something similar or has ideas to give me, I'd greatly appreciate it!

Use "Expr.txt" to monitor input pin.
Then in global loop trigger e-stop is machine is running and input is triggered and in #OnStart event return NAN to abort,

Nice, thanks a lot for the fast and helpful reply!

Another question though: how can I force the e-stop when the input changes? I mean with which syntax? I saw the variable _hw_estop in the documentation but it's read-only.

Ok so I solved it by using: exec(cmd('Machine.Emergency_Stop'))

One last thing, could you show me what is the syntax to return a Nan value from the script? I couldn't find it in the documentation.

Here is one solution using Expr.txt:

Code:

---

if(_hw_stop==0 && and(_hw_input,64), exec(print('Alarm!!!'), cmd('Machine.Emergency_Stop')));


#OnStart
if(and(_hw_input,64), exec(print('Alarm!!!'), nan()));

---

In main loop, if machine is moving (_hw_stop==0) and inpit 7 is triggered and(_hw_input,64) we execute two things - print alarm and cmd for estop
On on start event we check if input 7 is triggered. We also print alarm but we return nan and start is aborted if it is.