Troubleshooting Your Auto-Leveling Probe

You connect your Printrbot, click "run" or "start" in your software, only to watch your hot end dive right into the bed and drag itself in circles.  It can be very frustrating.  The good news is that the probe is probably functional.  Try these troubleshooting steps to identify the problem.

1. Make sure that the probe is properly calibrated.  If you have not gone through this process, please do so. Calibration is ABSOLUTELY necessary for your bot to function properly.

 

2. Check for mechanical problems.  For instance, if the Z coupler is not securely attached to both the motor shaft and the threaded rod, the motor will spin without raising the print head. The threaded rod should also be securely pressed to the motor shaft by the Z coupler. 

Other possible mechanical solutions

  • Power your bot on.  Hold something metal (screw driver, knife blade, etc) directly under the end of the probe and see if the light on the top of the probe lights up.
  • Check your probe extension wire.  Always match the wires from the plug end of the cables (as if the probe were being plugged straight into the board) before plugging them together.  Do not just assume that matching the colors is the correct way.  In the picture below, you would actually connect the black cable on the left plug into the red wire on the right plug.    
  • Check your wiring for fatigue or a stress point. Move the extruder just above the bed close enough for the light on the probe to turn on. Move the bot around as well as the bundle of wiring coming off the extruder and see if the light goes out at any point. It it does, find the break in the wire and replace the part.
  • Make sure that the probe has not moved over time. Through movement and vibration, the probe may have shifted after the nuts holding have loosened. You may need to tighten those nuts and re-calibrate your Z probe.
  • Also check to make sure you hot end is not loose. If your hot end is not secure, it might drop far enough to make contact with the bed.
  • If you have a Rev F board, make sure the probe voltage select jumper (pin connector) is in the right location or not missing.

 

 

3. Perhaps the problem is in your software settings.  Download the gcode file (FirstCube.g) attached to this article and use it for testing/calibration.  By using pre-generated gcode, you take your own settings out of the equation, to further isolate the problem.  If you run the "FirstCube.g" and see the same behavior, you can begin to focus on more mechanical issues (wire fatigue, mis-wired connection, faulty part, etc).

 

4. Speaking of gcode, make sure that you are adding the right settings into your start G-Code when slicing. You need to add a homing feature (G28 X0 Y0 Z0). This will start your printer moving to the home position on all three axis. You not only need this to print your object from the right spot, but this also brings your probe close enough to the bed for it to read the metal. The second thing you want to add to your start G-Code is the probing feature (G29). This will command it to probe the bed in three locations in order to find the plane the bed sits on. If this is not done, it can cause the same issue of running into the bed or it will not be working properly.

Check this in Cura/Start-End-GCode

 

 

 

 

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41 Comments

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    74custom

    I have been able to print successfully, however unfortunately I haven't been able to print for over a week now. The Z axis stopped homing properly. Believing the sensor had failed I ordered a replacement, replaced it and the probe failed. Contacted Printrbot, they believed it was a probe failure again and sent a new probe, this probe still lights but have the same issue when trying to home Z it moves up each time z home is pressed and the probe shows it is triggered whether it is near metal or not.

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    Shikhara Nalla

    ^ I have the same problem as above, what is the fix?

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    74custom

    I have not completely fixed the issue yet, but have at least made progress. Ordered replacement printer board the board now shows open not triggered. However DO NOT home z axis until you verify w/ m119 command that it shows appropriate status with reguard to metal under probe(triggered) and metal removed from probe area(Open) respectively. I did not and hot end crashed into bead and broke z axis motor connector. Replaced and now need to try reflashing the board firmware with correct version of firmware to correct current issue (or so i am told).

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    David Jackson

    I JUST got the same problem. I have no clue how to approach it. Literally, the printer worked, I cancelled a job to mirror a piece because of the reversed Y-Axis I still haven't fixed, then it didn't work anymore. Z-axis homes up. Probe works fine, lights up when it's supposed to and everything.

    Is there an official response to this anywhere I haven't found?

  • 0
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    74custom

    Simple answer is no. Trying the M119 Command will show you if your probe switches states if you use it once with metal present and once with out you should see triggered then open respectively. If this does not work likely cause of problem are probe or board. Many people myself included have had issues where the probe appears to be faulty only to find that the MosFet has burned out on the Printrboard. After replacing the board, my probe now triggers and opens however it does them inversely (open when metal present and triggered when removed). It was suggested I may have flashed w/ incorrect firmware after replacing board, have not tried reflashing yet.

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    David Jackson

    Okay, I just unplugged z-stop and M119 still said z_min: TRIGGERED.

    I then flashed the board and that didn't fix the problem (didn't fix the inverted y-axis either, for that matter.) This'll be my third board if they replace it - it was bought just over a month ago.

    I can't think it's hardware - the printer doesn't exactly take a power surge when you cancel a job. Very frustrating.

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    74custom

    Just out of curiousity what version of the firmware are you using? I know there was an issue with people using the rev d board version of firmware on the Rev F boards causing axis reversal. As for the probe does it always display triggered w/ M119 command? As I mentioned before my probe acts inversely at the moment so even w/ probe removed M119 displays Triggered however when I plug it back in and place metal under probe it shows open (incorrectly).

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    Marshalla87

    Same thing happened to me. I printed a calibration cube and noticed it was globing up from a little bit of plastic on the nozzle. I canceled the print and then restarted it and the nozzle was about 1cm above the board. So I tried restarting the software and hardware and nothing seems to work.I got the printer for christmas, its a Rev F board too.

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    74custom

    So if you have a triggered response from the M119 command regardless of the presence of metal or not. Easiest way to trouble shoot is to remove sensor retest M119 command if still triggered board is bad. Some people have gone to elaborate measure to develop work arounds, you can find their methods if you search the forums. Simply put the FET on the board has fried and its less hassle to buck up the $100 and get a new rev board. You may have to modify the firmware, I did my probe logic was reversed after replacing...

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    Don Winterhalter

    I think I'm having a different auto-leveling problem. The printer is a pre-assembled Metal Plus.

    The background: My hot end had become clogged. I removed the nozzle, heated the hot end, and pushed the clogged PLA through. I let it cool, put the nozzle back on, heated it, and was able to get a good stream of PLA through it.

    But then when I tried to print something, the nozzle was about an inch above the base and remained there after I killed the job and hit "home all" in repetier. I started trying to troubleshoot and the light on the probe doesn't come on if I put i piece of metal close to it. M119 shows "< 10:45:27 AM: z_min: TRIGGERED" whether or not there's metal close to the probe.

    There could be multiple problems going on here, I'm not sure.

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    Don Winterhalter

    More info. If I hit "home all" in repetier, then disconnect and reconnect, then hit "home all" again, the hot end & sensor will raise about 10 mm. The printer is plugged into a UPS / Surge protector so the power should always be clean.

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    evilseizurebunny

    So i have the new metal plus with dual extruders and heated bed. gotten past many stumblings and what not... after i do the home all, and run "G28 X0 Y0" and then do "G29" and it dose its homing dance, how fin a calibration should i be looking for between the 3 points it picks? i am getting a fairly consistent Bed x: 10 y: 259.00 z: 0.79 : Bed x: 10 y: 10 z: 0.79 : Bed x: 210.00 y: 10 z: 0.86

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    Clhartm2

    I am new to PB, just got a simple metal kit. I just ran into the same issues described above ( constant trigger on). I have tried the standard fixes, (fiddle with probe connections, reflash printrboard). I am curious if there have been any updates on latest fixes, or if you can only inform PB of the problems, and hopefully get replacement parts.

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    Robertcvdo

    What do I do if I'm missing the probe voltage select jumper (pin connector)?

    As far as I know, my board never came with that. Only now did I realize I didn't have that pin connector, because my Z probe sensor has yet to ever work upon receiving the printer.

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    John Doorley

    I have a Simple 2014 model. I am having a z-probe problem. When I home z it raises up like normal and instead of going down until the z-probe sees the bed, it raises up more.

    I tried reflashing, unplugging the z-probe, cleaning the z-probe, and adjusting M212 to set the Z manually. I haven't tried new parts, yet.

    Does this sound like software or hardware?

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    Si Janna

    I am having the same issue. It appears as though the auto leveling sensor is being ignored. When I home in the z direction the head moves down, the sensor light comes on, the head hits the bed, the head raises up, the light goes off, the head lowers, the light comes on and the head hits the bed. I have tried manually adjusting the home z position up to 1 mm. The problem is the same.

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    Joe Johnson

    I'm having a few issues with the leveling probe. When I run the M119 The ports say open except for the Z_min which is triggered. However if I unplug it the Z-stop now reports open. What's going on since its not the board thats wrong?

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    Yonnel Mylent

    Idem, the problem is the Z axis which makes up !.
    - When I ask the Z axis to go home, he goes about 10mm;
    - When I ask a calibration (G29), the Z axis up to about 10mm;
    - When I ask that all axes go home (All Home), the Z axis up to about 10mm;
    - If I send the G28 command, the Z-axis rises again .... :evil:

    And it is cumulative :shock:

    And if I ask him to mount 10mm, it does well, that's something ;)
    But I can not go down this axis Z (via control panel), it seems that for him, he is already at zero even after each command that makes up about 10mm!

    Note that the sensor detects the bed because it turns on its approach.
    To lower the Z axis, I am obliged to do by hand with the threaded rod.

    Grrrrrrrrr .........

    All the rest works fine (temperature, fan and other axes).

    The sensor is wired according to the picture below (Printrbot web page):
    http://d17kynu4zpq5hy.cloudfront.net/ig ... hRD.medium

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    Renier Mulder

    Ihave the same issue with Z homing upward, have read through the comments and it seems replacing the board and re-flashing the firmware doesn't correct this, im my specific case i am getting mixed results from the M119 command, i get "TRIGGERED" and "open" both with and without the probe being actually triggered by metal. could we please have some response on a possible course of action? or at least an avenue to look into...

    Fix this soon we must!

  • 0
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    Yonnel Mylent

    Although the probe seems to work well, it is not.
    Conclusion: Replacing the Z-Probe with a new and now everything is ok.

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    Don Winterhalter

    This seems to happen to enough people that there is probably something which is not sufficiently robust. My printrboard and z sensor were replaced and this fixed the problem. Two months later the problem has returned. Last week Brook said that they would take care of me and Aric said that they would get a new board and probe out as soon as they can. I've gotten no notifications that anything has shipped. This is probably as annoying for them as it is for me.

  • 0
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    Renier Mulder

    Good morning

    Could we please have an official response from Printrbot regarding this issue of Z-axis homing upward, looking at the comments here and all of the people who are currently struggling with this i gather that this is a common prblem, If i replace the Z-probe have i then fixed the problem or have i fixed the symptom of the problem? I just want to know whether to order one or two Z-probes...

    Thanking you in advance for your prompt response.

    Best Regards
    Renier

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    John Doorley

    My board was not working properly. If you have the same problem contact PrintrBot, they will help during troubleshooting. If need be they send a new board.

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    Mapalmer02

    Fix: My Z probe came wired Blue, Brown Black. I connected to the extension cable, Black to Black. I added 1/2 watt, 29.4k ohm resistance (two 10k and two 4.7k) to the Red extension wire. Since doing this my Z axis has been finding the base and starting the print at the correct spot.

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    Alexmacp27
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    Mapalmer02

    Thanks Alex. But when plugged-in "correctly" the Z-axis proximity switch doesn't switch at all, with or without the resistors. This is true at the 29.4k level of resistance. Might work at another level of resistance.

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    Alexmacp27

    and now that you have added the resistors, it works?

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    Mapalmer02

    Yes. It is now working correctly. I've seen 100% success at properly locating the base since this modification. Where as when wired as shown in the directions, it could not find the base. We've now printed over 12 items and each one started at the correct height.

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    Anthony Uy Yap

    Hi Mapalmer02, May i see how you add a resistor to the z probe?
    My z probe is not responding to any metal it just continue to home.
    I would really appreciate it.
    Thank you.

  • 0
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    Mapalmer02

    I wish that I could send you some images. But unfortunately, it will be this weekend before I will be near this printer and can take some pics. I will get the images to you as soon as I can.

    For now, here is how I did it. Note that I make no promises to how this will work with your machine.

    I connected to the extension cable, Black to Black. I added 1/2 watt, 29.4k ohm resistance (two 10k and two 4.7k) to the Red extension wire. I cut the red wire, about one inch from where the extension cable connector plugs into the board. I then soldered four resistors in a straight line, one then another, until the total resistance came to 29.4k I just used the resistors that I had on-hand. I see no reason that another combination would not work. I also do not know how accurate you need to be to the 29.4k. So I would think 28k to 30k should work. I covered the resistors with a length of heat shrink tubing so that the exposed solder joints could not short circuit to anything inside the Printrbot casing.

    I hope this gets your printer going. I will get you some pics as soon as I can.

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