X-Axis & Z-axis homing problem - issue with Proximity Sensor

I am facing problem in X-Axis & Z-Axis homing. When i try to home X-axis, it keeps going till the end and clatters against the X-motor. Similarly when i try to home Z-axis, nozzle hits the heated bed. I understand it is a problem with Proximity Sensor (Please correct me if i am wrong).

Now when the Proximity sensor is around 20-30mm from Bed and i am sending G31 command, it gives the reading as 256 (against 20 as written in the guide) and when i putting a white paper under the sensor and sending G31 command, it gives a reading as 496 (against 950 as written in the guide).

I have done all the troubleshooting as given in the troubleshooting guide:-
1. I have checked the wiring
2. I am using the updated firmware (version 0.78)
3. My SD card is being read properly. When i am sending M105, it gives OK: T:-18 B:-25. So OK means SD card is read properly.
4. THere is no IR source near the printer
5. Z-axis is properly moving up and down.

Please let me know what possibly is going wrong.

Regards,
Sagar

Hello,

i had also the problem that my sensor gives me a value about 500 when i am putting a white paper under the sensor. Unfortunately i didnt find the forum post which helped me. i used the wrong pin for the newer firmware version.

NOTE: From firmware 0.78 (3rd July 2014), the pin the proximity sensor uses has changed. On EXPANSION header, it has moved from the 9th pin from the right, bottom row, to the 6th pin from the right, bottom row. The diagram and picture below has been updated to reflect this.

You can also set your "probe height and threshold" with this comment in your config file.

G31 Z2.5 P370 ; Set the probe height and threshold

regards

Hello,

THank you for the reply.

I am using RepRapFirmware FIRMWARE_VERSION:0.78 ELECTRONICSuet DATE:2014-06-11.

I could successfully print for a long time. This is a sudden error i am receiving only now when My X-axis & Z-axis is not homing properly. When i read the troubleshooting instructions, i came to know this problem is to do with Proximity sensor.

I did all the troubleshooting, but still could not rectify the problem.

Regards,
SAgar

Hi Sagar,

try homing with the sensor shaded. It is very sensitive to IR-light.

You write you check the Z G31 at 20-30mm is that a typo? The instructions suggest 2-3mm for the G31 check or a P between 600-700. Below is Ian's guide to Z home (the reprap genius) It does sound like you get a light interference. I also upgraded to the newer Reprap sensor and have no more light related printing issues.

From Ian:
I'm currently rewriting the axis compensation page - it's got rather
long-winded and over-complicated. This will be the instructions for
setting Z homing:

1. Send M561 then M556 S100 X0 Y0 Z0. This resets any bed plane and
orthogonal axis compensation.
2. Move the X axis so that the proximity probe is over the tag closest
to X0 Y0. This is usually around X55 Y0.
3. Move the Z axis down so the nozzle just touches the bed.
4. Send G92 Z0. This sets the current Z position to 0, for reference.
5. Move the Z axis up 2mm. Send G31. The response will most likely be
around 400 to 500.
6. Move the Z axis up 0.1mm. Send G31.
7. Repeat the above until G31 reports a value of between 600 and 700
8. Send M114, and note the Z height.
9. Send G31 Z[zzz] P[ppp], where [zzz] is the height of Z from the M114
command, and [ppp] is the value reported by the last G31 command.
10. An EXAMPLE might be G31 Z2.5 P600
11. Home Z to test, and adjust as necessary.
12. Copy the G31 Z[zzz] P[ppp] command you have derived into the
config.g file on the SD card.

The sensor works best in the range 600-700. At this distance the nozzle
can be between 1.5mm and 4mm from the bed, depending on your printer. We
don't set the sensor at the point the nozzle is touching the bed - the
reading is too high and inaccurate.

If the homing seems inaccurate after all of the above, check that the Z
axis is moving correctly; there could be backlash that is causing
problems. Check:

1. look for binding or stalling in the z-gears
2. stiff movement of the Z axis up and down
3. If you have an adjustable z-runner-mount, it should only be lightly
gripping the extrusion, or that will cause problems for the Z axis movement

I hope that helps - you can always ask Ian directly at [reprappro.com]

---

Socrates ~ The Amsterdamman
slic3r-1.2.9

Quote
sagar_juneja
I could successfully print for a long time. This is a sudden error i am receiving only now when My X-axis & Z-axis is not homing properly. When i read the troubleshooting instructions, i came to know this problem is to do with Proximity sensor.

Did the change from working to not working correspond to any of these:

1. A firmware upgrade? If you upgraded to 0.78 from an earlier version, you need to move the blue z-probe wire to a different pin.

2. A change in the lighting in the room you have the printer in? Bright incandescent lighting (especially halogen lighting) produces lots of IR.

3. An improvement in the weather? Bright sunlight includes lots of IR.

If the answer to all of these is No, and you are still getting an abnormally high reading when the sensor is well above the bed, then:

1. Check that the black sensor head at the bottom of the board hasn't got bent (e.g. because it hit the bed clips).

2. Check the wiring, in particular the quality of the connections at both ends of the black and blue wires in the sensor loom.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

The X motor direction was also reversed in later firmware, which requires reversing the X motor connection on the Duet.

Dave

Hi Sagar

Sorry you're having problems with your Ormerod proximity sensor. However, I think this fault is not a common one. Two things:
1. You've got a very short range of IR responses: 256 to 496
2. Unless you have written it incorrectly, you are getting MINUS temperatures? You say "OK: T:-18 B:-25"?

If these are correct, I think something has shorted out and damaged the board, and the Analogue to Digital Converters are damaged and misreading. This can be caused by either a wiring problem, an internal short on the Duet, or a failed component on the board. Can you post a picture of your Duet, preferably with the wiring in place?

Ian
RepRapPro tech support

Hi,

Please note:-

1. First is correct, I am getting very short range of IR responses: 256 to 496
2. No I am not getting MINUS temperature, - is hyphen sign (punctuation mark). I am getting correct HEAD & BED temperature.

Please note except homing X & Z Axis, my printers works fine, all axis move perfectly. I am able to heat the head & bed properly. I am able to extrude as well.

Since I am not able to home X-axis & Z-axis, I am unable to print.

Regards,
Sagar

Sounds like the issues are all connected to the IR sensor. Both X and Z home require it and your reading a improper range of IR responses. Either the sensor itself may have gone bad of the Duet which controls and works with the sensor. Upgrading the sensor to the newer reprap IR friendly version is a upgrade I am very very happy I made. If you upgrade the sensor and the problem remains consistent, then its likely the Duet. Then at least you'll have a upgraded sensor and have found the issue.

Can you manually set the X axis to the home point and send a G92 X0 and do the same for G92 Z0? If the sensor is the issue you would have bypassed its function, homed the X & Z and should be able to print.

---

Socrates ~ The Amsterdamman
slic3r-1.2.9

Hi Sagar

The firmware reports the temperature without a hyphen for positive temperatures, so it's confusing if you put it in, especially when that's exactly how the firmware reports a negative temperature!

A workaround for homing the X and Z axes, so you can print, is to move the x-carriage, by hand, so the nozzle is over the edge of the bed, and send 'G92 X0'. Then lower the Z axis until the nozzle just touches the bed, and send 'G92 Z0'. Home Y as normal. This will set the X, Y and Z homing position, and allow you to carry on printing. Make sure the none of your gcode has any G28 commands at the beginning, which will cause the axes to home again, and the manual settings to be lost. Before you turn off the printer, if you move the axes to a specific point eg X10 Y10, then Z10, you can easily send G92 X10 Y10 Z10 when you turn it back on, and have the same position.

You said this fault happened 'suddenly'. Was there anything that changed, or happened, that caused this? Did the sensor board hit one of the bed clips? Check that 12V is not being transferred to the clips by an incorrectly constructed heated bed, as this can short circuit to the 3.3V sensor board; see 7th step here: [reprappro.com]

Also, it's quite easy to dislodge the wires on the sensor board, or Duet. Double check they are fully plugged in.

To check the proximity sensor, compare your sensor with the one on this page: [forums.reprap.org]
You can also test that the sensor output is correct; put a multimeter between ground, and the pin on the sensor board that the blue wire plugs into (3-wire board), and test the voltage. With a piece of paper up against the sensor, it should read at least +3V, and with 5cm of space under the sensor, it should read pretty much 0V. If this is correct, the problem is with the Duet, and most likely the internal Analogue to Digital Converter (ADC) is damaged, most likely from short circuiting somewhere, though do make sure the wiring is correct.

Let me know if that helps.

Ian
RepRapPro tech support

Edited 1 time(s). Last edit at 10/01/2014 06:27AM by droftarts.