Best bed levelling system?



  • Hi guys.
    I have a Dbot corexy with one z motor, 4 regulation screws bed 300x300 , bltouch with mesh leveling enabled.
    Is there a better way to obtain a leveled bed> for example would be an improvement switch to 3 z independent Z motors? Or switch from 4 point to 3 point bed screws?
    In other words, what would be the state of the art of bed leveling ?
    Andrea



  • see
    https://duet3d.dozuki.com/Wiki/Bed_levelling_using_multiple_independent_Z_motors

    however with 1 motor driving the 4 screws there should be no tilt after initial leveling, since all lead scews are connected.

    do you have tilt over time?



  • thank you for answering me . Maybe I bad described my setup
    I have a single motor that drive 2 lead screws
    The printing bed is regulated by 4 screws.
    I read the wiki but I am wondering which system is the most effective and rock solid in real use.



  • it really comes down to looking at the tilt over time.

    look at the height map. see where the lead screws are. do they need to be adjusted after a certain time to make the bed more level.



  • On my corexy, I have two leadsrews driven by a stepper via a belt @ 2:1. The bed uses 3 screws to mount to the bed frame. Haven't had a problem with the bed holding it's level.



  • @claustro said in Best bed levelling system?:

    .......................... In other words, what would be the state of the art of bed leveling ?
    .........

    IMO the state of the art is to have a level bed that never needs to be re-levelled, and to achieve that is neither neither difficult nor expensive.

    3 points define a plain, therefore 3 screws, evenly placed in a triangle will raise and lower that plain without imparting any twisting forces so the bed will stay flat. Obviously the lead screws need to be in perfect synchronisation so the best way to achieve that is to drive them via a single motor and continuous belt. Initial levelling is done by slackening the pulleys on the screws, then adjust two screws in relation to the third. If designed correctly so that none of the screw or bed mounts can warp or twist, then the bed will remain level.

    At a conservative guess I'd say that my printer runs about 20 hours a week on average sometimes less, sometimes very much more so at least a 1,000 hours a year for the last 4 years. The bed level was adjusted when it was built and about a week later after things had settled in. Since then, it has needed adjusting on only two occasions and both of those occasions involved partially dismantling the printer and transporting it to another location. The last time it needed adjusting was when I returned from exhibiting at the TCT show in September 2017. I'd say that is "state of the art".☺



  • If you're building something to make impressive youtube videos, or you want to see just how low-end you can get with mechanical construction and still make a functioning printer, go with 3 independently driven lead screws that automatically level the bed before each print, and bed mapping to compensate for a bent piece of sheet metal used for the bed plate.

    My corexy printer's Z axis has two belts driven by a single motor and a 3 point kinematic mount for the 300x300x8mm cast tooling plate bed. The only time it has to be releveled is when I take apart the Z axis to make modifications. It's a tall printer and I transport it laying on its back in my car. I've done that many times - just stand it back up and start printing.

    The difference between the two approaches is where you want to spend your time and money. The first method requires more electronics and motors, and more time to set up and debug. The mechanical approach requires more solid construction and access to tools you might not have.



  • I don't use any leveling system at all, I shimmed the bed into alignment by individually adjusting stainless steel spacers with sandpaper, and it has never moved since.

    This system is the heaviest (and maybe also the most expensive), but if you find yourself constantly adjusting and probing the bed you have to wonder if other alignments are shifting as well.



  • ok so the 'trending answer it raise from this discussion is the best leveling system is the one that is not needed.
    So there is a second question that arise. which is the best bed and how to connect to the frame?
    I have the simplest solution . MK2 heated bed fixed with 4 adjusting screws on the frame with glass over it, it works but isnt perfect.
    I am afraid about aluminum bed for 3 reasons cost, availability and thermal reaction.
    So which way to follow ?'
    Can you post your solutions?



  • @claustro said in Best bed levelling system?:

    .................. I am afraid about aluminum bed for 3 reasons cost, availability and thermal reaction.................

    Aluminium tooling plate is the best solution because the bed needs to be flat, and it needs to be stiff enough, and it needs to have good thermal conductivity. This question gets raised with monotonous regularity.



  • the question raises with monotonous regularity maybe because the answer is not as clear as you think. You can find many opinions saying glass is the way to go same for the opposite.

    I think glass surface has many advantages over aluminum
    100% flat surface
    cheap and widely available even borosilicate 4mm
    heating isn't a problem in my opinion , even with my 24 volts mk2 bed I can reach 100 celsius in reasonable time
    in my experience no big sticking problem capton tape , blue tape , or hair spary , I never had adhesion problems.
    So you can say , "so why don't you stick with your glass bed and stop bugging us if you alredy know the solution//"

    the answer is that I am not sure glass is the best solution
    The main problem , in my experience with glass, is how to connect glass to the frame?
    I used 2 system till now , the classic metallic clip over mk2 heated bed , and magnetic supported glued under glass connected to metal sphere on the frame unfortunately none of this system works perfectly

    Can i ask you where you sourced your aluminum bed and how much does it cost?



  • @claustro I think you misunderstand. The aluminium forms the bed structure and also acts as a heat spreader. You can put your preferred print surface on top of that, whether it be glass, PEI sheet, Kapton tape, or some other exotic material. Attaching a heater directly to glass is a bad idea because of local hot spots, and because glass is fragile - especially if it is unsupported.

    Here in the UK I used these people and chose their fine milled, high precision Ecocast plate https://www.aluminiumwarehouse.co.uk/aluminium-plate-cut-to-order?utm_source=googleadwords&gclid=CjwKCAjwp_zkBRBBEiwAndwD9SywzaSx2jpN4yzrttZt1r3oBqrlwYsYoaXiHW9OrJxuNPGxQYDQmRoCMh4QAvD_BwE

    A search for "aluminium tooling plate" should turn up a local supplier.

    BTW, I use 6mm un-toughened float glass glass on top of my 10mm thick aluminium plate, with a mains powered silicone heater stuck to the underside of the aluminium.



  • Glass is a print surface, not a bed plate (at least it shouldn't be).

    A 4 screw mount doesn't level the bed. It bends it, makes it unstable (sort of like a table with 4 legs on an uneven floor), or both. Glass and air are thermal insulators. Putting glass on an unflat plate will lead to cool spots where the glass doesn't touch the plate. Attaching a heater directly to the glass also leads to uneven heating because the heaters aren't perfect and glass is a thermal insulator. Here's a Taz 2 printer that came with a heater glued to a glass bed plate (on 4 screws!):
    alt text

    That glass bed eventually broke and was replaced with a piece of 1/4" thick cast aluminum/PEI on a 3 point leveling system. Here's the same printer with the original heater glued to the new aluminum bed plate:
    alt text

    A 3 point mount is stable, like a tripod. When you turn one leveling screw, the whole bed plate tilts on the other two screws. A kinematic 3 point mount allows the aluminum plate to expand and to be set in tram with the XY plane of the printer without causing anything to bend or flex.

    A Kelvin kinematic mount has one reference point and allows the expanding heated plate to slide on the leveling screws in a controlled way. Setting it level the first time is fast and easy and then it doesn't have to be touched again, assuming the printer's frame is reasonably well made. Here's the underside of the plate I recently installed in a printer:
    alt text
    Notice the reference hole on the left and the slot in the right ear. The chamfer prevents lateral motion but allows the plate to tilt on the spherical head screws for leveling. As the plate expands the slot slides on the pitch screw head in the X direction (in this case). The roll screw contacts the smooth underside of the plate which is free to expand in X and Y at that location. The roll screw tilts the bed on the other two screws. Springs hold the plate down on the leveling screws.

    I'm partial to PEI as a print surface but there are plenty of other options. PEI is glued to the aluminum so there are no clips or clamps to bang the extruder into. I have to wait for it to cool off before removing prints, so it isn't for impatient or high production users.



  • Hi,

    I'm happy with my cast aluminum beds supported by four adjustable screws. Yes three is fine but I prefer four.

    It only takes a couple of minutes to run the macro that allows me to check all four corners of the aluminum plate and make any needed adjustments.

    Not high tech but it has proven to be reliable and stable.

    Frederick



  • thank you all for the answers , my first cartesia printer , believe it or not, has a glass bed connected to the y with glued supports.

    @deckingman thank you for the supplier link I'll check it out.
    Isn't in your solution the weight a problem?
    Can i ask you the power of you heating element?

    @mrehorstdmd
    I have difficult to perfectly understand your bed mount .
    left and right are for regulation screws.upper one is the reference .right?
    the groove on the right let the bed expand only in this direction (x)
    how about the force through the Y direction?
    Do you think your system could be fitted in a corexy D-bot?

    @fcwilt To be honest I ma not having problem with my simple setup ,MK2 with 4 screws and 4mm glass bed on it, but maybe because I don't know what kind of print quality
    and speed , a " well built " 3d printer can achieve

    thank you all



  • @claustro said in Best bed levelling system?:

    @deckingman thank you for the supplier link I'll check it out.
    Isn't in your solution the weight a problem?
    Can i ask you the power of you heating element?

    Weight isn't a problem - in fact a heavy bed that does not have to move in the Y direction, is an advantage because it makes the printer more stable. It only moves in the Z direction so apart from homing, it only ever moves by the layer height which is a very short move. A single Nema 17 motor is more than adequate with the fine lead screws that I use.

    The bed uses a 10mm thick x 400mm x 400mm aluminium plate and I use 6mm thick glass on top and an 800 Watt mains powered heater. If I was starting again I would probably use an 8mm thick plate. The heater is somewhat over powered but I prefer the faster warm up time that gives me. The underside of the aluminium is insulated for the same reason.



  • @claustro said in Best bed levelling system?:

    @mrehorstdmd
    I have difficult to perfectly understand your bed mount .
    left and right are for regulation screws.upper one is the reference .right?
    the groove on the right let the bed expand only in this direction (x)
    how about the force through the Y direction?
    Do you think your system could be fitted in a corexy D-bot?

    In the third photo, the upper ear is the roll adjust point. The left ear with the chamfered hole is for the reference adjuster, used to set the height of the bed, and the right ear with the chamfered slot is for the pitch adjuster.

    When the bed heats up it expands in all directions away from the reference point which could be anywhere on the bed: alt text

    I chose the left edge for the reference point, and put the reference screw there. When the bed expands, the direction of expansion at the pitch support point is in the X direction only, so the slot is parallel to X. That allows the bed to slide on the pitch screw's head. At the roll screw, the plate is flat and can slide on the screw in X and Y. Reference and pitch adjusters are turned through holes in the bed plate, the roll adjuster is tweaked from under the bed.

    I put this type of bed in my coreXY machine and in another printer that moves the bed in Y, so there's no reason it couldn't be put in a D bot. The reference and pitch levelers don't have to be at the center of the edges of the bed- they can be put along the edge opposite the roll adjuster. I put them at the center because I wanted them located close to the Z axis linear guide bearing blocks.

    Leveling is super fast and easy. When you turn one screw, the bed plate tilts on the other two, so the easiest way to level is to adjust the pitch first. Once pitch is dialed in, adjusting roll doesn't affect it. If I do work that requires me to take the Z axis apart, I use the manual bed leveling assist in RRF to reset the bed to level. If I don't take the Z axis apart, I don't have to touch the leveling, even if I transport the printer laying on its back in my car.



  • thank you all , I have to study your solutions and figure out how I could implement in my print. If it will be not a bother for you I'll ask your opinion in the future:)



  • I use 3 screw autoleveling and I'd never go back to old school. It's just so nice to have it level without hassle when I've worked on the machine or if I suspect that it's out of level. It's so quick that I just run it when I probe Z anyways. No more fiddling 🙂



  • Something like this could work ? Worth change from printed bed support to aluminum one?
    0_1554137861271_dbot.jpg

    @minim

    When you talk about 3 screw autolevel are you talking about 3 indipendent motors for Z axis?
    can you give me more info regarding your printer?


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