DIY hot wire cutter electronics: needs some advice

[JCA34F]

@themarinus

void loop(){
	  int val = analogRead( A0 ); // read potentiometer
    int sensorValue = analogRead(A0);
    val = map(val, 0, 1023, 0, 255); // map the analog value from max 1023 to max 255
	  analogWrite(PWM_PIN, val ); // send value to the mosfet
    Serial.println(sensorValue*1);
  delay(100);        // delay in between reads for stability
  }

Wouldn't this be easier?
analogWrite(PWM_PIN, analogRead(A0) / 4);

Why print sensorValue 10 times a second?
The MOSFET source pin MUST be connected to 15V ground along with Arduino GND.
You should put a 10k pulldown resistor from Mosfet gate to GND so gate is not floating while Arduino is starting up.