I’m a beginner too but I had exactly this with my weather station PC last winter, and the fix was to stop caring about the number. Find the port by what’s plugged into it instead. pyserial can list ports with their USB ids and serial number:

from serial.tools import list_ports

def find_arduino():
    for p in list_ports.comports():
        print(p.device, p.vid, p.pid, p.serial_number, p.description)
        if p.vid == 0x2341 and p.serial_number == "85736323838351F0B0E1":
            return p.device
    return None

port = find_arduino()
ser = serial.Serial(port, 9600, timeout=2)

Run it once to print yours and copy the serial number in. 0x2341 is the vendor id of genuine Arduino boards. If yours is a clone with a CH340 chip (vid 0x1A86), careful: those usually have no serial number, so with two clones you can’t tell them apart and you’d match on p.location (the USB socket) instead.

Also wrap the read loop so it looks for the port again after an error instead of dying, then people can replug whenever they like.

I looked into this for a friend’s small bakery. I couldn’t find a doc page for Forge either, so I can’t tell you what it does for quality or how it gets on a plan.

What works with the normal IoT part: have the sensor’s controller (or a small PLC) send the thickness of each piece, or the min/max/average per 10 s, as telemetry, e.g. {"thick_mm": 7.12, "rejects": 3}. Then an alarm rule on the profile for out of tolerance. There’s no «between» operator, but you can group conditions with any:

{ "any": [
  { "key": "thick_mm", "op": "<", "value": 6.0 },
  { "key": "thick_mm", "op": ">", "value": 8.0 }
] }

For counts per shift, send a growing rejects_total counter and chart it with the increase aggregate per hour. The reject gate itself must be driven locally by the sensor controller or PLC, not from the cloud; a belt at 0.4 m/s can’t wait on a round trip.

The conditions reference is Alarm conditions reference.