Z Axis home switch is not working

[johnleyburn]

Hello,

Received my Carve King this week and just completed the build.  When I try to home the machine the Z axis travels up and when it contacts the Z -Axis home switch it continues into the frame and acts if the switcht is not detected.  I have performed the following troubleshooting steps:

1. Checked the switch with an OHM meter and the switch is working properly.
2. Checked switch operation at the connector and find that the wiring is OK.
3. Checked all switches using Show verbose output option in UGS. Y - Switch displays Pn: Y when closed. X- displays Pn:X when closed. Z - No chage
4. Plugged Z axis home switch connector into X - Axis End stop and UGS displays Pn:X when closed.
5. Checked for voltage at the Z+ end stop pins on the CNC shield and found no voltage.  The X+ and Y+ end stop pins show 5 Volts.

Thanks in advance for any help you can provide.

[Derek the Admin]

Couple things to check. You’ve done some good diagnostics so far. I’m sure we can solve this in pretty short order.

Can you confirm that one of the pins is not pushed to the side? Sometimes a pin from the red board misaligns with the blue board and doesn’t seat. Next, have ya ever plugged the 24v power supply into the Uno board? That usually affects homing pins.

[johnleyburn]

Hi Derek,

First of all I would like to say that the build went very well. I followed the instructions to the letter and the machine turned out great. I think that this is a very nice machine that you have put together.

I did a little research on the GRBL firmware and the CNC shield, and found out that the spindle enable and the Z limit were swapped starting with GBRL 0.9. So I checked the Spindle enable pin and found that there was 5.0v there. I then connected the z limit switch connector to the pins labeled spindle enable and triggered the switch and watched the verbose output; the screen displayed Pn:Z. I then started a homing cycle and it went through without a hitch. It looks like there may be some discrepancy between the CNC shield and the newer versions of GBRL.

Thank you for getting back to me.

[Derek the Admin]

There is such a discrepancy if a certain compile time options is not modified, but we have changed that option to keep the Z functionality where it is labeled on the board. That is the case unless you have a laser (just curious, do you?) in which case we have to let that Z functionality move to SpEn so we can use some onboard pulse width modulation that only exists non that Z pin.

[johnleyburn]

No, I do not have a Laser. Will I loose any functionality by leaving the Z limit on the SpEn pin?

[Derek the Admin]

No you won’t.

[Brendan]

I had a similar issue. I did this fix and the z pin is showing... will I run into issues? I do have a laser that I will want to get working soon enough.

[Derek the Admin]

No I think you will be OK. When you get the laser you will just put it where it is labeled as z limit.

[Brendan]

Ok I'm not sure if this is related. Now the z pin is working. When I run $H it goes up, and backs off as it should. But when it backs up to the Y & X home position something goes wrong and the couplers disconnect and spin. Its like the threaded bar moves to the front of the machine, and since its still doing $H the motors just spin. Do I need to tighten the tiny screws for the bearings on the opposite end of the threaded rods?

[Brendan]

I just tried it again. I looks like it moves back hits the homeing switch - but doesn't stop. So the couplers keep spinning and disconnect.

[Derek the Admin]

Yes. Please check that section of the instructions about that. Those set screws do need to get tightened or the screw will walk axially, possibly causing what you are experiencing.

[Brendan]

So I had the x & y wires crossed. My mistake in assuming what the x and y were. So when it hit the Y pin x continued to move.