How to Home Z on Dbot CoreXY??



  • How to Home Z…... Forgive me I am a newbie, I bought a DBot CoreXY with a Duet Wifi board. The man I bought it from obviously was far more experienced than me. He told me, when I got it home, I would need to readjust the settings, as the car ride would move it out of wack some. After setting up the WIFI Control GUI; I was able to attempt to make 1 print. I noticed during the print that the hot end needed to be closer to the bed, as the print would not stick. I attempted to adjust the settings, however it is different from my Printrbot, therefore now when I press Home Z, it cranks my build plate up and makes an awful noise, so I press emergency stop. When it returns to idle, I Home the X & Y, then use the machine controls to move the hot end to the center of the bed and adjust the Z till it almost pinches a piece of paper. I then go to the G-Code Console and type G92 Z0, in return it makes the Z 0, however when I hit Home All or Bed Compensation, it cranks the build plate back up. Before I did anything tonight, if I hit Home Z, it would go to particular spot and move the Z up and then down, it was close, but not close enough. I am very interested in learning and mastering this machine (if I don't accidentally break it first) 😞

    Any pointers or advice you can give me, is well appreciated.
    Thanks


  • administrators

    What settings did you change? Did you back up the configuration and homing files before you changed them?

    Z homing can be done either by a homing switch or using a Z probe. See https://duet3d.com/wiki/Configuring_RepRapFirmware_for_a_Cartesian_printer#Homing_Z_using_a_Z_probe and the section that follows that one.



  • Not sure what settings I changed. I thought it was incremental however something is way off. Because the build plate keeps going in the wrong direction during homing and pushing up into the hot end / extruder. I know this bot is not equipped with a Z Probe, may add one at some point to make it easier. I chatted with the builder of the bot, he said something about adjusting the end stop in the middle of the bed? I am not sure what he is referring to as I only see the stops for the X & Y, the one for the Z is in the wrong orientation; unless I am confused and the Z is not the up and down, the X is not the Left and Right & the Y is not the Front to Back. Here is what my configuration files look like. See if you see something way off.

    Home X

    ; homex.g
    ;homing using a x-MIN endstop

    G91 ; relative mode

    G1 Z4 F200 ; lowers bed 4mm to avoid dragging nozzle over the bed
    G1 X-340 F5000 S1 ; move up to 340mm in the -X direction, stopping if the homing switch is triggered
    G1 X4 F600 ; move slowly 4mm in the +X direction
    G1 X-10 S1 ; move slowly 10mm in the -X direction, stopping at the homing switch
    G1 Z-4 F200 ; rises the bed 4mm back up

    G90 ; back to absolute mode

    Home Y

    ; homey.g
    ;homing using a x-MAX endstop

    G91 ; relative mode

    G1 Z4 F200 ; lowers bed 4mm to avoid dragging nozzle over the bed
    G1 Y340 F5000 S1 ; move up to 340mm in the +Y direction, stopping if the homing switch is triggered
    G1 Y-4 F600 ; move slowly 4mm in the -Y direction
    G1 Y10 S1 ; move slowly 10mm in the +Y direction, stopping at the homing switch
    G1 Z-4 F200 ; rises the bed 4mm back up

    G90 ; back to absolute mode

    Home Z

    ; homez.g
    ;homing using a z-MIN endstop

    G91 ; relative mode

    G1 Z-320 F200 S1 ; move up to 320mm in the -Z direction, stopping if the homing switch is triggered
    G1 Z2 F50 ; move slowly 2mm in the +Z direction
    G1 Z-10 S1 ; move slowly 10mm in the -Z direction, stopping at the homing switch

    G90

    HOME ALL
    ;homeall.g
    ;homing using a x-MIN, Y-MAX and z-MIN endstops

    G91 ; relative mode

    G1 Z4 F200 ; lowers bed 4mm to avoid dragging nozzle over the bed
    G1 X-340 Y240 F3000 S1 ; move up to 340/240mm in the -X (x endstop is MIN) and +Y(y endstop is MAX) directions until the homing switches are triggered
    G1 X4 Y-4 F600 ; move slowly 4mm in +X and +Y directions
    G1 X-10 Y10 S1 ; move up to 10mm in the -X and -Y directions until the homing switches are triggered

    G90 ; back to absolute mode to move nozzel to desired place
    G1 X10 Y190 F5000 ; put head over the centre of the bed, or wherever you want to probe

    G91 ; relative mode again
    G1 Z-310 F200 S1 ; home z
    G1 Z2 F50 ; move slowly 2mm in the +Z direction
    G1 Z-10 S1 ; move slowly 10mm in the -Z direction, stopping at the homing switch
    G90 ; back to absolute mode

    ;–--------------------------------------------------------------------------

    ;homeall.g
    ;homing using a x-MIN, Y-MAX and z-MIN endstops

    ;G91 ; relative mode
    ;G1 Z4 F200 ; lowers bed 4mm to avoid dragging nozzle over the bed
    ;G1 X-340 Y240 F3000 S1 ; move up to 340/240mm in the -X (x endstop is MIN) and +Y(y endstop is MAX) directions until the homing switches are triggered
    ;G1 X4 Y-4 F600 ; move slowly 4mm in +X and +Y directions
    ;G1 X-10 Y10 S1 ; move up to 10mm in the -X and -Y directions until the homing switches are triggered
    ;G1 Z-310 F200 S1 ; home z
    ;G1 Z2 F50 ; move slowly 2mm in the +Z direction
    ;G1 Z-10 S1 ; move slowly 10mm in the -Z direction, stopping at the homing switch
    ;G90 ; back to absolute mode

    Here are some pictures of the end stops I am identifying as to their position.
    X End Stop

    http://i1081.photobucket.com/albums/j346/titancornhusker/Dbot%20CoreXY/X%20End%20Stop_zpsixfi1n3e.jpg

    Y End Stop
    http://i1081.photobucket.com/albums/j346/titancornhusker/Dbot%20CoreXY/Y%20End%20Stop_zpsizsqpzu1.jpg

    Z End Stop
    http://i1081.photobucket.com/albums/j346/titancornhusker/Dbot%20CoreXY/Z%20End%20Stop_zpsy4hxlzit.jpg

    Thanks for all of your help


  • administrators

    Does the bed move up and down, or does the gantry move up and down?

    I agree that the Z homing switch looks like it is in the wrong orientation. Has its mounting broken?



  • The bed moves up and down (or should I say up to down), the gantry moves left to right and front to back. Experimenting I have successfully edited the homez.g to get it to stop digging into the bed with success, however it still says the Z axis not set.Probably because it written to just of up and down a little, instead of picking points on the bed, since I am not certain how this code is written. The bed volume for this build is 300mm wide (X) 200mm (Y) 350mm (Z). Also I don't if it relevant but the Z axis only has one threaded rod in the rear center of the bed. I know most DBot's are configured with 2 on the left and right side of the build platform. The builder of the bot, stated he liked that approach better because he thought it held the bed more level and he produced great prints with the setup. He did give me additional parts to convert it back if I so desired. But hey why fix it if it ain't broke, oops I did break it, at least now I feel it is something simpler than I thought, I just can't see it.

    I reached out to the builder of this bot, he was very vague as to why the z end stop was located where it was, none the less, he edited homez.g file to compensate for that, or so he states. Before the original file was edited, I believe it would home Z by starting where Y was at 0 (Back left corner), then move to 200mm Y (front left corner), then move 150mm to X was at 150 (in center). Ideally would you want the homing to go Y0, Y200, Y100/X150, center? I am not sure if you can set multiple probe points, but if you can 4 then X0 / Y0; Y200 / X0; X300 / Y200; X300 / Y200.

    I knew I need someone more experienced to look at this config. When I get this resolved and am able to starting printing again, I will back up all files and find / print the correct part to relocate the Z end stop to be functional again. The mount has not been broke, it just looks to be positioned incorrectly serving no purpose. Thanks for looking it over and giving me your insight.

    Here is what I changed the homez.g file to reflect to get it to stop digging into the bed.

    G91 ; relative mode

    G1 Z4 F200 ; lowers bed 4mm to avoid dragging nozzle over the bed
    G1 Z0 F200 S1 ; move up to 320mm in the Z direction, stopping if the homing switch is triggered
    G1 Z4 F50 ; move slowly 4mm in the +Z direction
    G1 Z-4 S1 ; move slowly 4mm in the -Z direction, stopping at the homing switch
    G1 Z-4 F200 ; rises the bed 4mm back up

    G90 ; back to absolute mode


  • administrators

    I think the first thing you need to do is to establish whether you can get the Z homing switch to trigger at all. You can read the state of the homing switches by looking at the Settings/Machine properties page of the web interface, or by sending M119. If you can get the Z switch to trigger by moving the bed, then let us know what height the bed is at when it triggers. If not, then you need to adjust the position of the Z switch so that it does trigger.



  • M119
    Endstops - X: at min stop, Y: at max stop, Z: not stopped, Z probe: not stopped
    Drive Configuration
    Drive Endstop hit Minimum Maximum InstantDv Max Speed Acceleration Motor Current
    0 Yes 0 mm 300 mm 3.33 mm/s 250 mm/s 1200 mm/s² 800 mA
    1 Yes 0 mm 200 mm 3.33 mm/s 250 mm/s 1200 mm/s² 800 mA
    2 No -0.2 mm 300 mm 0.5 mm/s 5 mm/s 15 mm/s² 800 mA
    3 Yes n/a n/a 0.5 mm/s 60 mm/s 1000 mm/s² 1000 mA
    4 Yes n/a n/a 0.5 mm/s 60 mm/s 1000 mm/s² 1000 mA
    5 No n/a n/a 0.5 mm/s 60 mm/s 1000 mm/s² 1000 mA
    6 No n/a n/a 0.5 mm/s 60 mm/s 1000 mm/s² 1000 mA
    7 No n/a n/a 0.5 mm/s 60 mm/s 1000 mm/s² 1000 mA
    8 No n/a n/a 0.5 mm/s 60 mm/s 1000 mm/s² 1000 mA
    9 n/a n/a n/a 0.5 mm/s 60 mm/s 1000 mm/s² 1000 mA
    Z-Probe
    Type:
    Unmodulated (1)
    Trigger Height:
    0.7 mm
    Trigger Value:
    500
    Other
    Geometry:
    CoreXY
    Motor Idle Current Factor:
    30%
    Motor Idle Timeout:
    30s


  • administrators

    So does the Z (drive 2) endstop switch status change to 'stopped' when the bed is at an appropriate height?



  • No the end stop status never changes, of course that is due to orientation of that end stop looking straight at you rather than looking down at the floor. When I manually push it, the status does change from no to yes and so forth. So that end stop is working, just apparently it is not setup mechanically right. Some how the configuration was working before, because when you hit home Z it would go and probe the bed or maybe it was just making it's rounds around the bed. I assume they setup via configuration to do that. If I can some how modify that to do it again, I will fabricate a new arm for the end stop and position it correctly so that the stop hits the end of the bolt. When I do that, should the extruder actually be touching the bed when the end stop is active or just before it touches the bed? Nonetheless do you see anyway to make this work until then.



  • And am I correct in saying that the bed has to be completely homed in before it will actually begin to print?
    I you look at this guys setup, he seems to have the end stop in the same position in the back right corner. I may be new to this machine, but seems like a waste of an end stop if nothing is going to activate it or why even have it.
    https://cdn.thingiverse.com/renders/82/59/35/7f/66/f6a3e2daee352ac560b4c4cc8efe4021_preview_featured.jpg


  • administrators

    To make it work until then, you can home Z manually. First home X and Y. Then command the head to the centre of the bed, and command the bed up until the nozzle just touches the bed, or just grips a sheet of paper. Make sure that your slicer start gcode does not include a G28 command to home the printer.

    It doesn't matter whether the Z homing switch triggers exactly when the nozzle touches the bed or slightly earlier, as long as the switch doesn't physically prevent the nozzle touching the bed.



  • I tried that Simplfy 3d but it executed the command and messed up. I have engineered a functioning Z end stop. Now the X is the only thing homing. I found this tool for writing firmware.

    https://configurator.reprapfirmware.org

    If I knew all of the correct information too input, wouldn't it write the firmware for this setup, fairly easily? I don't know if I am savy enough to know all of the details to input without assistance to correctly get everything right. I tried to import my config file just to see what it would do, but it won't accept it, therefore I don't want to monkey around with it to much till I am certain. You have been big help. I know I am not far away from seeing this thing work.



  • does it use a switch mounted on the rails on the back or does it have a probe?

    If it has a switch on the back do you see wires coming off of that switch or have they come unplugged?

    A probe will be mounted to the XY carriage that holds the hotend. Can you post pics of your printer? I have a C-bot myself, and there is also a facebook group for the C/D bots that may be able to help if it is an actual hardware issue and not firmware or controller.



  • I removed the code from the slicer and attempted to print. No luck, it actually dropped the bed down several inches and proceeded to print. So that is not going to work. I have no choice but to figure the homing issue out before hand.



  • The switch originally mounted to the back of the rail, but it did seem to serve a purpose, because when the bed came all the way up, it didn't hit the stop due to the orientation. I don't think the bot is equipped with a probe. Here are photos of my bot. It was original configured as a D, but the builder decided to use a single motor on the Z, I think so it would be easier to configure, which I am fine with. Right now the only axis that will home correctly is X. Any advice you can give would be appreciated.

    Here is the original end stop rail

    http://i1081.photobucket.com/albums/j346/titancornhusker/Dbot%20CoreXY/750F6D77-8ABE-4727-8768-E65EB86BFAFC_zpsc18lxnyw.jpg

    The one I changed, but can change back
    http://i1081.photobucket.com/albums/j346/titancornhusker/Dbot%20CoreXY/8FB1D025-6057-43FC-9F9B-5A50ED1B6C6A_zpsapwrc0n8.jpg

    The stop mount I had to rig to make switch active
    http://i1081.photobucket.com/albums/j346/titancornhusker/Dbot%20CoreXY/484E1CB9-32FB-4AD7-9F50-3AFD54E932E7_zps2ionmvni.jpg

    Build Plate all the way Positive on Z (single motor)
    http://i1081.photobucket.com/albums/j346/titancornhusker/Dbot%20CoreXY/1589F06B-674E-4074-AC01-0CE47933E699_zpseutcea4f.jpg

    Titan extruder setup
    http://i1081.photobucket.com/albums/j346/titancornhusker/Dbot%20CoreXY/8F3FD5BF-AB78-452A-B762-094685AE54B8_zpsk9hdbayg.jpg

    Overview
    http://i1081.photobucket.com/albums/j346/titancornhusker/Dbot%20CoreXY/144522B5-931E-450B-ADA6-459D0592C7C7_zpsw3h4m1ce.jpg

    Duet Wifi in case and Power Supply
    http://i1081.photobucket.com/albums/j346/titancornhusker/Dbot%20CoreXY/02561DB0-8334-49F4-82A8-09ABD350099B_zpsdmjrymib.jpg

    There is no probe on the hotend just the fan shroud,



  • I just assembled a DBot with a Duet Wifi and am in process of calibrating/tuning now.

    I finally got the homing working on all axis, relevant configuration files here: https://drive.google.com/open?id=0B4QI9opJS9SbSldRZjQ5NUd0U2c

    I hope those are of some help.



  • I will check those files out as soon as I am home tonight. Is your printer configured with 1 or 2 Z axis motors? Got any pics?



  • Regarding your Z endstop, it seems that the microswitch has been bent out of position by the endstop screw on the bed platform.
    The original mounting bracket is correct, but the switch itself is supposed to be flush with the PCB, see: https://drive.google.com/open?id=0B4QI9opJS9SbTUp3VE0tWHVSY1k

    The first thing I'd do if I were you is to verify that the platform moves in the correct direction, pressing Z +0.1mm in the UI is supposed to move the build plate DOWN. If it doesn't, you need to change the Z motor direction in your config.g then try again.

    If that works, I would suggest you take a copy of my homez.g and verify manually that it works as it should.
    What I mean by manually is that you

    1. move the build plate down from the UI to something like 100mm (do this in small steps in case your steps/mm is incorrect, simply clicking "Z +100mm" might translate to some ridiculous value in those cases)
    2. click "Home Z" in the web ui
    3. verify that the build plate starts moving towards the hotend and
    4. use your finger to push the Z endstop to verify that the build plate stops. If it doesn't, hit the emergency stop in the UI before the bed crashes into the head/endstop.

    E: I'm using the default 2 Z-motor setup, but it's a pain in the butt. Be glad you only have one, my Z axis gets all wonky as soon as I turn off the Z motors since one side will start sagging while the other will stay put. Probably the first upgrade I'll do is either a 1 Z-screw or 3 Z-screw modification. I kinda like the linear rod setup you have on yours, will consider something similar.



  • Hey flaw I,
    I meant to also ask did you configure yours with a z probe or end stop? And what orientation / location is your Z end stop if using one? That is why I asked if you had any pics.



  • Yeah, I have a Z endstop. There's a link to a picture of it in the previous post. The pic can be found in the same folder as as the config files as well.


 

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