CoreyXY with one z motor 3 separate bed leveling motors.

  • Hello everyone, this is my first post on any forum so I am a bit of a forum virgin 😀 I have probably skipped over this reading through the many posts on here so I apologise in advance, I am currently building a coreXY printer with one z motor that moves my bed I've mounted 3 motors onto my bed mount that are independent to my z axis.

    My question is, can you set up bed leveling this way or have I got it totally wrong and also skipped over the subject on here somewhere (sorry), how would you go about controlling the single z motor, and then use the 3 motors on the bed mount to level the bed.

    Thanks in advance

    Regards jase

  • Hi,

    Interesting concept but I have no idea how do make it work.

    Do you wish to run bed leveling at the start of each print or do you see it as a separate operation done as needed?

    Possibly you could alter the motor configuration with M584, etc using a pair of macros, one for the 1 motor setup, one for the 3 motor setup.


  • Anytime you use multiple motors you have to worry about them getting out of sync when power is cycled. Many people prefer to build a Z axis that uses a single motor driving multiple screws with belts to ensure that the screws stay in sync and avoid the multiple motor sync problem completely. If the screws stay in sync, the bed will stay level (assuming the rest of the printer isn't made of cardboard and duct tape).

    You're trying to do a hybrid that takes a perfectly good single motor lift that can't cause the bed to tilt and adds 3 additional motors (and all the electronics and cabling) that are going to lose sync whenever power is cycled, that guarantees the bed will tilt. The fact that the motors are there makes them necessary- if they weren't there, you wouldn't need them.

    If you have to have autoleveling -and it's not too difficult to build a printer that doesn't need it- use multiple lifting screws and motors to lift the bed or X axis driven by independent drivers.

    Many printers have unstable beds that require frequent tweaking. Sometimes it's because the Z axis isn't stable, sometimes the bed and/or its mount is unstable, sometimes both. You can design for stability and eliminate the need to relevel the bed. Start with a rigid, flat, thermally conductive bed plate, put it on a rigid, stable mount (which includes using 3 leveling screws, not four), and lift it with a well constrained single motor system. You'll level it once before you print on it for the first time, and then won't have to relevel until you take something apart that affects the leveling.

  • Moderator

    Wait, so let me see if I understand correctly. You have a single Z motor to move the whole bed assembly up and down, and then between the bed frame and the bed itself you have 3 more motors that you want to use to level the bed?

  • i would be interested in seeing it. please post a picture.

  • Hello everyone and thank you for your interest, ok... I started building my printer about 2 years ago just had a design in my head and thought hmmmn I might give it a go so I was collecting bits motors, extrusion, duet wifi and expansion board etc etc so every weekend I would do a bit here and there as I was running my own garage and was working around 60-65 hours a week so as you could imagine it was quite a slow project but was ok with me.

    July last year I had a bit of a legal battle with my landlord and decided to walk away after 15 years, now I've had lots and lots of time to spend on it it's all built up but looks a mess with wires everywhere (will post some pictures but please excuse the mess 😀), I was watching a 3d printing video on YouTube a bit ago now think it was some kind of convention maybe called murf and there was a printer with 3 motors leveling the bed, he was achieving some very fine quality prints of course I had to add this to my build it's nice to have the choice to go that fine had some thin nema 17s knocking around I mounted them in 3 point configuration and carried on with the rest of my build.

    I'm now close to wiring so I've updated my 5inch panel due firmware also the duet wifi from 1.15b I've also set up a pi zero w so I can see print progress (or if I need to call the fire brigade 😨 ) just need to make an enclosure for the pi cam, everything is coming together so thought I would start looking at this 3 point leveling system and what I might need to do to get it going, and the penny dropped...... realised I have a single z motor independent from the other 3 on the bed and started to panic, I've been on here reading trying to find something to give me a glimmer of hope but can't seem to find any info on this matter specifically so was time to make my first post ever and get some expert advice, must say I'm impressed/blessed I will post some images shortly please excuse the mess, and thanks for your help people.

  • as you can see we are a bit surprised by the design.

    its far more common to drive the entire z bed assembly by 3 (or 4 for the railcore) motors and level the bed assembly and with it the bed.

  • Yes veti it is a strange setup, if it is possible though can't wait to give this project some juice and see what happens i have got some pictures now i will upload them as i said I'm a bit of a forum virgin so if there is away to do it wrong i probably will ☺ .
    ![0_1571070429827_IMG_20191014_163053.jpg](Uploading 100%)

  • is there a file type and size i should use, i have just tried to upload some jpegs but there was an error file too large thanks jase.

  • @Threefaze I reduce my pictures to 1000 pixels wide. Seems good enough for most pictures I post on here.

  • ok I've just resized them lets try again.output-onlinejpgtools.jpg output-onlinejpgtools-6.jpg output-onlinejpgtools-5.jpg output-onlinejpgtools-4.jpg output-onlinejpgtools-3.jpg output-onlinejpgtools-2.jpg

  • Moderator

    I think this should be doable with macros. You would need to rebind which motors are assigned to the Z axis at different times. Homing the printer with the main motor, reassign the z axis to the 3 leveling motors. Do the leveling routine. Then switch back to the main z motor and re-establish Z=0.

    How much travel do the 3 bed motors have?
    Are they mounted to the bed with enough flex for the leveling to happen without binding?

  • small warning. those white belts tend to have steel cores that snap over time and cause problems.

    for the leveling, as phaedrux said. if the bed can move up and down enough for the travel moves to happen with the 3 z motors, then it should work.

  • Cantilevered beds, especially on end supported guide rails, have a tendency to bounce a lot due to motion of the XY mechanism and shaking of the printer's frame. I think those springy shaft couplers on the leveling motors are going to allow a lot of lateral bounce, and on the free end of the cantilevered bed, will also contribute to vertical bouncing.

    How is the bed leveling actually accomplished? The motor turns screws, and there are nuts on the bed plate or the bed plate is threaded? Is there any provision for thermal expansion of the bed plate?

    As @Veti says, steel core belts and corexy mechanisms are a bad combo, mostly because the pulleys are usually too small diameter for the belt. When the steel core wires break inside the belt, it isn't usually obvious and leads to all sorts of weird behavior that can be hard to diagnose.

  • i really hope so phaedrux it would be great if it can be done with macros, the 3 bed motors have 10mm travel each and they are mounted in a way that they can flex and move freely, I'm thinking if i dial it in as best as i can then the bed can do the rest to get it super level, also maybe around 1mm movement for the motors to do there thing, i think haha.

    veti I've got 2 types of belt and pulleys to play with, T2.5 polyurethane and T2 standard black and its super easy to change ive made a system on the print head where you have 4 m5 bolts that draw in the belt and tension it then just lock them off, really hoping the bed leveling can be achieved.

    mrehorstdmd this is something i put quite a bit of thought into oscillation I've got some guides made to run on the front of the bed with some v xtreme wheels to run in the extrusion i will have to take a picture and show you see what you think, planning on having them made of aluminium, i could mount a piece of extrusion behind the bed and run the wheel system there that's my backup plan 🤔, the screws are slotted into the bed, in the pictures i previously posted there are some silver m5 bolts poked in they are just to hold the bed in place while i was measuring , on the slotted ones they just have ceramic washers and nylock nut on the underside, as just mentioned to veti I've got 2 types of belt and pulleys and are quite easy to change but will take both of yours advise and use the standard belts when its up and running.
    output-onlinejpgtools-8.jpg output-onlinejpgtools-7.jpg

    so in summery it is possible to run this bizzare setup 😌

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