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Can someone confirm I'm setting the Z axis correctly? getting funky results

Discussion in 'OpenBuilds Forum Help' started by Garrette Hedrick, Jan 6, 2025.

  1. Garrette Hedrick

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    I was eyeballing the Z settings - i would simply lower the spindle to just above the boards and set zero there. this was causing hard limit errors alot. I bought a aluminum Z probe, its solid 15mm. I go thru the configuration and theres a couple things I dont understand and that documented below. the good news is i dont get the hard limit errors anymore. just looking to do it correctly and your input is appreciated.
    Setup z probe

    upload_2025-1-6_11-25-27.png
    Setup my 15mm solid z probe under the spindle, confirm probe position
    upload_2025-1-6_11-26-22.png

    Click on probe. The spindle lowers until contact as expected. It displays this message, quickly followed my the error message
    upload_2025-1-6_11-26-50.png
    upload_2025-1-6_11-27-1.png

    I clear the alarm

    This is where I need some guidance. I remove the alligator clip and probe and this is the current setting.
    upload_2025-1-6_11-27-17.png
    I manually lower the spindle to just above the wood deck and get ready to cut. My question is – am I supposed to set the z here? Or leave it alone? If I leave it alone and start the cut, it goes into position way above the piece and starts up there which is worthless obviously. I bring it back to home and lower the spindle to the board, set the zero there. When I run the job it cuts normally. My question is, what did I accomplish using the probe if I am manually overriding the z setting? When I use this configuration, its not throwing any errors, but cuts too deep, I have to rebuild the grbl telling it the wood is thinner to get it to cut properly with tabs. I’m glad I’ve eliminated the z limit errors, but don’t understand the proper way to set this. Maybe this is jus the way it is and everybody is fiddling with these settings?

    This is my cut settings on a 13mm plywood board.
    upload_2025-1-6_11-27-33.png
     
  2. Giarc

    Giarc OpenBuilds Team
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    You said you have a 15mm thick probe, but you are using the OpenBuilds Probe settings which is for a 9 mm thick probe. Therefore the machine thinks it is 7mm closer to your work surface than it actually is so it starts cutting in the air. You need to enter a custom probe. Fix this and then see if you get errors.

    Also, have you homed the machine at start up?
     
    #2 Giarc, Jan 7, 2025
    Last edited: Jan 7, 2025
  3. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    The RESET indicates a short circuit when the probe is touched too... Wired wrong? (Should be SIG and GND only)
     
  4. Garrette Hedrick

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    thank you for this response. I didnt even notice I had to choose the probe type and you are correct i left the default openbuild probe, thats my fault and I will use the custom probe setting and try again. I appreciate the guidance!
    when you asked about 'have you homed the machine at start up?' I'm not sure what that means. I simply set the x, y and z each time and begin cutting. Maybe this would explain why my cuts start in places I didnt expect....can you describe the homing process please.
     
  5. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Step 1: Click Home all
    Step 2: All done

    Home, then setzero/probe, then run the job
     
  6. Garrette Hedrick

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    I must admit, I've never touched that Home setting. My assumption is the home is the machine home and the set zero for x, y and z are for the job settings? do you do the home all each time you setup a cut?
     
  7. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Home on power up, and after every crash, alarm, error, abort + any time you are not sure if its still homed

    Home sets Machine Coordinates

    Probing/Setzero sets Work Coordinates. But Work coordinates are nothing but an offset from Machine Coordinates, so it makes sense to Home.

    Even if your gcode never uses any machine coordinates (our Fusion 360 post etc does) you might run some Macros like this that does, or want to use the Crashed Job recovery wizard etc - having home - means a crash is as simple as rehoming and bam your zero point is right back where it was automatically. Later on you could use jigs etc that overlay multiple coordinate systems etc - just good practise to start homing. Ensure the machine knows where it is in the real world
     
  8. Garrette Hedrick

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    I performed the home operation successfully. I moved the spindle to the left corner of the board. I lifted up to use the custom z probe. these are my settings. upload_2025-1-8_15-40-37.png I engage the custom probe. upload_2025-1-8_15-41-6.png
    When I click on custom probe parameters, this is what I see upload_2025-1-8_15-41-50.png
    i update the values to what I think they should be as I want this to be my X and Y zero and a 15mm probe upload_2025-1-8_15-42-43.png
    I start the probe. It moves down to the top, confirms the Z, then instead of just going back up, it slides left, apparently looking for X or Y? then it errors. I did not get this behavior with prior tries. Not sure what its looking for. maybe i should buy a different probe or are my settings incorrect? thanks
    upload_2025-1-8_15-43-38.png
     
  9. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Zero? Impossible - am XYZ probe always has a shoulder of some thickness... Sounds like you have a "z probe" - in which case move off the XYZ probing tab and use the Z probing tab :) - can't run an XYZ probe operation with a probe that doesn't do XY too...


    Now see that is the best idea... just order XYZ Touch Probe Plus then you can do XYZ, X, Y, Z even Tool diameter probes, upside down Z probes all of it!
     
  10. Garrette Hedrick

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    thanks again for your response.
    View attachment 62288
    i went back in to try your suggestion. on the z zero tab there are only 3 choices, the openbuilds xyz, the openbuild z touch and the custom xyz probe. there is no custom z probe option. so I was usin the custom xyz option and tried the openbuild z touch. it did not move laterally or horizontally like it did before and found the z depth. this set my z to 20mm. upload_2025-1-9_13-40-35.png upload_2025-1-9_13-41-3.png i still dont understand what I have accomplished? if I begin a cut using these values what am I telling the machine? that my material is 5mm thick? the board Im cutting is 12mm with a 3mm waste board under and then the deck. This makes no sense to me, dont I want to tell the machine the distance to the top of my material? sorry for these primitive questions, i just dont get what the goal is here. thanks.
     

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  11. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Plate thickness = measure your Probe plate with calipers.

    If your place puck on top of material, then do a z probe, then once its finished, remove the puck and do a gotozero on Z (buttons next to DRO) you should be bang on top of the material (at zero)

    After probing its up off material puck thickness + some clearance looks like 5mm, whatever - do the Gotozero to see if Zero is where it should be
     
  12. Garrette Hedrick

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    Wonderful! this made good sense and it did exactly what i wanted, the location and cut depth was perfect. Now I understand these setting and how to make it more accurate. The homing seemed to made the biggest impact along with the proper probe setting. I appreciate the help.
     
    Giarc and David the swarfer like this.

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