Best bed levelling system?
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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!):
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:
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:
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.
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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
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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 achievethank you all
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@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.
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@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:
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.
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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:)
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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
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Something like this could work ? Worth change from printed bed support to aluminum one?
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? -
@mrehorstdmd Thank you for sharing your really good idea or implementation for us printer
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@claustro You don't have to put the pitch and reference screws at the center line of the bed as I did. If you do that, when you raise one side with the roll screw, the other side goes down. You can put the reference and pitch adjusters along the edge opposite the roll adjuster. Then when you adjust the roll, only that side goes up or down which should make leveling even easier than it is on my machine.
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@mrehorstdmd
Someting like this?
Do you think the d-bot structure will be rigid enough for the extra weight of the bed?
Just for talking, what problem do you find in using a single plate made of glass ( plate and printing surface at same time), a thick one , maybe 10 mm , with holes like your plate. the problem could be the weakness and low thermal conductibility so longer time for reach the temperature , but other then that?
Just thinking I have a lot of problem finding small peace of cast aluminium in Italy.
Ideally what planar tolerance is desirable?Other question , , what about inox , if weight isn't a problem , which has a lower thermal dilatation coefficient ?
thx
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@claustro said in Best bed levelling system?:
el are you talking about 3 indipendent motors for Z axis?
can you give me more info regarding your prYes 3 independent motors. In the config you setup where the 3 ballscrews are located in X/Y and then you make a bed file that probes as close to the motors as possible. Once 3x probe points are done it calculates how much to compensate on each screw and then it levels. On the video below it only corrects 0.190mm error so it's not easy to see the correction after probing but it works really quick and simple.
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@claustro Your diagram is good.
You don't want to attach a heater to glass because the heaters don't heat evenly by themselves and glass is a thermal insulator and will not spread the heat well. Also, glass can break. You really should mount the heater on a thermal conductor like aluminum (cheapest, readily available material). If you want to put glass on the aluminum it's OK if the aluminum is flat or the glass is thin enough to conform to an unflat aluminum surface. If you put thick glass on an unflat aluminum surface, the heating will be uneven and may have problems with prints sticking.
The D-bot's strength will depend on how you built it.
Planar tolerance that is a small fraction of print first layer thickness is best, but if it isn't very flat, mesh compensation can make it usable.
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I have a modified Dbot. You can see my solution to the Z axis deficiencies in the link in my signature.
In summary, it is 3 point adjustment of aluminum plate on a solid bed platform, V wheels at all 4 vertical corners with a cross brace on the front of the bed frame, and 3 lead screws synced to 1 motor with a belt. To level the bed I use manual bed level assistant to help me adjust the bed screws. The platform itself must be aligned very carefully to begin with, but once aligned it stays stable for me. Then I use mesh bed compensation to adjust for the bed surface (one corner of my bed has a slight curve. If your plate is flat, this isn't needed.)
There are many ways to go about this. It's a trade off. After seeing the railcore II this weekend at MRRF using the 3 independent lead screws to do automatic leveling I can confirm that when designed correctly to allow for some flex it can work very very well. On the flip side, if you have a solid platform and a single motor, you can get great results without it. It's nice to have options.
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Hi,
This is what I have been told to use, on several occasions, for bed plates:
https://www.midweststeelsupply.com/store/castaluminumplateatp5
It's cast rather than rolled and is supposed to be more uniform.
Frederick
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@claustro said in Best bed levelling system?:
Worth change from printed bed support to aluminum one?
Absolutely. There are aluminum versions of several of the basic printed dbot frame parts. Replace as many of the printed parts as you can.
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I might try a three lead screw setup.
Where did you find such a long belt?
Thanks.
Frederick
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@fcwilt I'm in Canada, so I got it from MakerParts.ca
https://makerparts.ca/products/102mm-long-6mm-wide-gt2-endless-belt-loop?variant=37138162511
They carry a lot of the OpenBuilds parts and other various printer parts on the higher end of the quality spectrum. I originally had a loop belt and pulleys from aliexpress, but the belt was stretchy and the pulleys out of round and I had some Z banding issues, but after switching to the parts from MakerParts I had no more issues.
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@phaedrux said in Best bed levelling system?:
@fcwilt I'm in Canada, so I got it from MakerParts.ca
https://makerparts.ca/products/102mm-long-6mm-wide-gt2-endless-belt-loop?variant=37138162511
They carry a lot of the OpenBuilds parts and other various printer parts on the higher end of the quality spectrum. I originally had a loop belt and pulleys from aliexpress, but the belt was stretchy and the pulleys out of round and I had some Z banding issues, but after switching to the parts from MakerParts I had no more issues.
Thanks.
I think I am seeing the same thing. I get much of my stuff off of Amazon but I think most is low cost import stuff.
Frederick
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Thank you all for such great suggestions.
I am still not sure which way to go.I have a no cantilever 2 lead screw single motors setup , changing to 3?
3 lead screws with one motor: pro lead screw always in sync con need manual adjustment
3 lead screws with independent motor pro automatic leveling of the plane cons a little bit more expensive , need software setup , risk of out of sync motors?
with this setup is bed leveling system still needed or the bed plate can be mounted fixed on the frame? Is it possible , and make it sense, combine mrehorstdmd bed leveling system with 3 motors lead screws setup?
I already own the extra Z motors so costs isn't a variable in this decision.These are some photos of my printer take a look , any suggestion is appreciated!
https://www.dropbox.com/sh/7bvnlctmiqushv1/AAB_oR3lea8S2ZBIfeM5EsyUa?dl=0Other question for D-bot owners.
I have 3 wheels Z guide, is it worth converting y axis also to 3 wheels, I read mixed experience about it.@minim can you tell some more of your setup do you have some photos for taking inspiration:-).
Thank you all
A.
