How to config one Switch for limit and reference

Hi all,

I'm just working on my 2nd cnc router with a few improvements. Actually I don't know how to configure the limit and home switch of the x-axis.
I'm using only at the x-axis one proximy switch NPN for both limit and home. Homing works fine, but when the machine starts to go in the direction to the max. end of the x-axis, ist stops after a few millimeters (15.0 mm) at the point, where the home contact is mounted.
In the baseplate I've mounted 3 matching pins, and when the portal is moving past, the sensor will be activated.
I have pictures for better understanding.

thank you for help.

greetings Thomas

The scheme you propose won't work because the home switch point will be seen as a limit.
What you can do though is remove the home pin and, home to one of the limit pins.
Then if you still want the 0 reference point to be the same as you have it now, add a home offset.

Hi Todd,

that're terrible news :blush: because I don't know how the get the matching pins out :sick: First I wanted to use screws, but the matching pins looking better, but now I have the problem to pull one of them out again

However, thank you for your fast reply.

What are the pins? How are they held in?. It is just MDF, can you drill a couple of holes on either side of the pin, then grab it with a needle nose pliers and pull it out?

the pins are made of steal and are hardened, used in mechanical engineering for example. I know 2 kinds of pins, one with thread inside and one without. I've the one without :laugh: They are held in by press them in. The diameter of the pins is 6m6 mm. The hole in the plate is 5.8 or 5.9 mm.

Thomas wrote: that're terrible news :blush: because I don't know how the get the matching pins out

The underlying problem is that with only one sensor, no matter how you wire it, the system has no way to know if the sensor is sensing a limit pin or the home pin.
Even if you had two sensors and the pins were on different axes, having a single pin mid-travel as a home pin is a problem because the machine does not know which direction to move to search for the home pin. The only way to get a reliable mid-travel home is to have a long target that covers half the travel.

So, given that there is basically no way that the mid-travel pin can ever be useful you do need to find a way to remove it.

I think I would try drilling a hole at a shallow angle underneath the table to insert a punch from the back to push the pin out.

If it makes you feel better, I recently had a very similar problem myself. I drilled a hole in the bed of a lathe to work as a limit switch target, then hammered in an aluminium disc to make it look neat and stop swarf building up in it. What I hadn't realised is that the aluminium disc makes the hole invisible to the proximity sensor. (plastic is fine). In my position I could drill and tap the plug to insert a screw to pull it out.
I would have suggested this to you, but you said that the pin was hardened, so that won't work.

If the hole is deeper than the length of the pin you could try pushing it further in so that it no longer trips the sensor. But that is a bit of a gamble and might not work, but will make the pin even harder to extract.

I am guessing you don't have a welder?