Probing

Most machines use a tool setter and/or a probe to precisely position the machine.

Tool setters are used to set the tool length offset, which is basically the Z offset from the tool tip to the work piece. Probes are used to set the X and Y offset based on the work piece.

Because the two are used for different purposes, it is generally okay to use both on the same input port, assuming they are both NPN or PNP.

Tool setter

The simplest tool setter is a switch which is triggered when a tool hits the switch. However, this is not very precise and doesn't leave room for error.

Most advanced tool setters use a spring-loaded mechanism that is triggered when the tool hits the setter. This is more precise because it takes the deceleration of the machine into account when the tool is hit. Also, good tool setters have an ALARM output, which is triggered when the tool setter hits its maximum depth.

Note that tool setting requires a deceleration to work precisely. This implies that the machine should be moving slow to ensure that both the tool setter and the tool are not damaged. When moving slowly, the deceleration is usually between zero or two steps.

If you use flood or mist coolant, it is advisable to use tool setter that is not affected by coolant, or use a magnetic tool setter which can be removed when it is not in use.

While some video's exist that show how to do tool setting manually, we do not recommend setting the tool length offset manually, bacause it implies that users need to use their hands in the machine while running it.

Probes

Probes are used to set the X and Y offset of the work piece. Probes are normally spring loaded and are triggered when the probe hits the work piece. Like tool setting, probing requires a deceleration of the machine to ensure the exact position is measured.

It is possible to use hard probing. Normally, it is advisable to use a dowel pin for hard probing, because dowel pins are cylindrical and therefore don't have a direction like a tool bit.

Wiring

Use the 'probe' input for both tool setting and probing. The probe input is isolated and should only be used in combination with the +5v and GND on the same terminal header.

Configuration example:

probe:
  pin: gpio.34
  check_mode_start: true
  hard_stop: false

If you have a tool setter with an emergency stop functionality, you can wire that along with the other emergency stops to the 'stop' input.