Help regarding my CoreXY



  • Hi, I have built a 300x300x300 CoreXY with Duet 0.6 board.
    I am facing some issues
    1. X axis is mirrored - In my prints, X axis is mirrored.
    My Home X happens in Back right side and having it as 300. When it comes to extreme left, it comes 0.
    My home is in Back left side. Homing makes 0, and when it moves front it comes 300.
    Left motor configured as X and right motor as Y motor.
    Z homes up (Mini IR sensor) with 0 and down to 300.
    How to change the config to get normal prints?

    2. My Z uses dual motors wired in series. Z axis motors are Wantai 42BHY811 having 2.5A current rating. I am using 1600mA current in config. Uses 412mm smooth rods supported by 2TR8*8 lead screws.
    When moving up and down it is jerking a lot. I adjusted jerk to 12mm/min, acceleration down to 15, maximum speed to 30.
    Only 1-2 times it slowly moves without any issues. Again jerk starts.

    3. I am using original Igus rails for X and Y. That is also creating a lot of noise. Even the acceleration values are given as X - 300, Y-120.
    Belts are GT2 with 20teeth pulleys.
    Also, belts are getting loose frequently. Belts are tighten by taking inside 2slots. Tighten with 2 Zip ties.



  • Sounds like you have your wires reversed for the axis. You can fix it be swapping the wires on the motors or changing the direction in the config.

    Noise sounds like slop, make sure your igus bushings are compressed properly to have no play.



  • @Whitewolf:

    Sounds like you have your wires reversed for the axis. You can fix it be swapping the wires on the motors or changing the direction in the config.

    Noise sounds like slop, make sure your igus bushings are compressed properly to have no play.

    Thanks. I will swap and see the results.

    Igus block was tighten properly and it is not having any play.

    Any solution for Z axis jerk?



  • @selva_tvi:

    …...........
    Any solution for Z axis jerk?

    8mm lead screws are going to need a lot of torque if you are driving them directly without any gearing. Suggest you first check that there is no binding of your 4 guide rods and that the bed slides freely, when disconnected from the lead screws. If there is no binding or sticking then try increasing the motor current to the maximum that the Duet can supply which I think s 2.0 Amps (2,000) mA. I'm not sure but I suspect that when you use two motors in series, each motor will only draw half what the stepper driver can supply. If that is the case, then try using two stepper drivers - one for each motor. You'll need to map them using M584 like this https://duet3d.com/wiki/G-code#M584:_Set_drive_mapping



  • Yeah, I checked. Without the motors connected, with lead screw + 12mm rods slides very easily down as well as up.
    I hope as per Dc42, when connected in series, current will be same for both motors (set current). Voltage will be divided into half.



  • So suggest you try upping the current to 2,000 mA. If that doesn't work, try using two separate drivers. I have a single high torque nemA 17 driving 3 screws which runs fine at 1800mA but struggles at 1200. BUT, my lead is only 1mm. As yours is 8mm, then you'll need a lot more torque. TBH, if it were my printer, I'd throw away those 8mm lead screws and use a much finer lead or use gearing to both lower the torque requirement and improve positional accuracy.


  • administrators

    1. To change to a right hand coordinate system, add parameter Y-1 to your M667 command, or swap the X and Y motor wires.

    2. The jerky Z movement probably means that your Z acceleration in M201 and/or maximum Z speed in M203 is set too high.

    HTH David



  • @dc42:

    1. To change to a right hand coordinate system, add parameter Y-1 to your M667 command, or swap the X and Y motor wires.

    2. The jerky Z movement probably means that your Z acceleration in M201 and/or maximum Z speed in M203 is set too high.

    HTH David

    I have set acceleration and maximum speed too low. Now Z is moving very slowly.
    Still it is having jerks.
    My motors are rated for 2.5A with 4.8kg torque.
    So, if I give 1600mA current (around 65% of rated current), will it be sufficient to hold Z axis?
    I have another set of motors with 5.5kg torque with 1.5A current rating. Shall I change it?


  • administrators

    Do the leadscrews move smoothly and easily if you turn them both by hand? Perhaps the Z axis is binding.



  • Yes. It runs very smoothly without motors. Even after fitted with motors it is moving freely when turned with both hands.
    How to get rid of that binding.?


  • administrators

    If you are running a Duet 0.6 at 1600mA then the drivers may be overheating. Are you cooling the Duet with a fan? B!owing air along the line of drivers on both sides of the PCB is best. Reducing the current to about 1300mA may improve things if this is the problem.



  • I have provided 60mm dc cooling fan for the duet 0.6 board.
    It cools both top and bottom layers.

    I initially started with 1200ma faced the jerk, then increased to 1600ma.

    For Z binding lubrication will provide solution?


  • administrators

    If it is moving freely when you turn it by hand, then binding may not be the problem.

    What is the Z steps/mm in your M92 command?



  • @dc42:

    Do the leadscrews move smoothly and easily if you turn them both by hand? Perhaps the Z axis is binding.

    I hope finally I got some solution. As you said it may be Z axis binding, I googled and found some other forums suggesting to use Lubrication for the smooth rods.

    I didnt find any non greasy oil, so I used normal vechicle grease for the smooth rods and coconut oil for the lead screw nuts. It worked fine. Immediately, jerk stopped. Now it is running smoothly. Also, slowly increasing the acceleration and max speed for Z axis.

    Always it is a wonderful thing to get help from this forum. Thanks for everyone who has helped to identify the problem.



  • I was just bragging about his awesome support in the folgertech FT5 forum… looks like another duet wifi for an ft5 has been sold LOL Thanks again David, i have been doing tech support for over 30 years and never seen anything like this. Paid through the nose for CISCO TAC and that doesn't even come close to this level. You are Da Man! 🙂



  • @dc42 said in Help regarding my CoreXY:

    1. To change to a right hand coordinate system, add parameter Y-1 to your M667 command, or swap the X and Y motor wires.

    2. The jerky Z movement probably means that your Z acceleration in M201 and/or maximum Z speed in M203 is set too high.

    HTH David

    In the "Configuring RepRap Firmware for Core XY" doc it says:

    "Important: make sure that you have chosen a right-hand axis system. That is, looking down on the printer the +Y direction should be 90 degrees anticlockwise from the +X direction. If instead it is 90 degrees clockwise, you have a left-hand axis system, which will give you mirror-image prints."

    But there's no note on this setting. My CoreXY is right handed, and this forum reply was the answer I needed. Maybe the doc could be updated?


 

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