Saturday, July 29, 2017

3 Point Print Bed Leveling vs 4 Point Bending

The word "leveling" applied to printer beds is a misnomer.  When you "level" the print bed you're not trying to level it to the earth the way you level a picture that you hang on the wall.  You're really "tramming" the bed, which means adjusting it so that it is parallel to the printer's XY plane, which is defined by the positions of the X and Y axis guide rails.  In case you missed it, let me state specifically: the bed surface is NOT the printer's XY plane.  When the bed is properly leveled, it is parallel to the printer's XY plane.  The guide rails, which in a properly built machine don't move, are the reference, not the bed plate.

CAD software uses right hand rule coordinate space, and each of the three axes are perpendicular to the other two, a condition called orthogonality.  Your printers axes should all be orthogonal, too, or prints will come out skewed.  Autoleveling serves one purpose only: to get the first layer of the print to stick to the print bed.  It assumes the guide rails/axes are orthogonal and does its job as if they were.  It can't compensate for axes that are not orthogonal.


Right hand rule coordinate space used in CAD software, slicing software, and in your printer's construction and configuration.


There are two common 3D printer configurations.  The most common, exemplified by the Prusa i3 and it's many clones, has a bed that moves in the Y axis.  The other most common type has the bed moving in the Z axis.  Less common types have fixed beds (most common among those are delta machines).

In printers with the bed moving in the Y axis, the X axis is lifted in Z, most commonly by two stepper motors turning screws.  If the screws don't stay synchronized (and there are many ways they can lose sync, including just powering the printer on), the X axis tilts, which means the XY plane tilts, and is no longer perpendicular to the Z axis.  As long as that condition persists, prints will be skewed, even if your printer has autoleveling.  Skewed prints won't fit together properly, gears won't mesh right, threaded parts may not work, etc.  IMHO, using two motors to lift the X axis is just plain bad design.  Maintaining orthogonality of axes is critical in a 3D printer or you can't print accurately.  In this type of printer, autoleveling contributes to the problem because it masks a tilted X axis until the X axis has tilted so far that either the operator notices the tilt or the Z axis mechanism fails.

That brings up another point.  Autoleveling systems all use some sort of bed sensor on the extruder carriage, which usually rides on the X axis.  The bed itself rides on the Y axis guide rails.  Therefore, autoleveling can compensate for nonideal X and Y axis characteristics, such as sagging guide rails which can be a big problem for large format or cheaply made smaller printers.

In printers with the bed moving in the Z axis, the bed is usually lifted in Z by one or more motors driving screws.  If the screws get out of sync, the bed tilts, but the printer's axes remain orthogonal to each other (assuming they were set up properly in the first place).  The first layer may not stick, but if you manage to print, the prints won't be skewed.  Autoleveling can work well in this type of printer, because it is being used to compensate for an unlevel bed, not to compensate for tilted axes and an unlevel bed.

Anyone who paid attention in the first week of high school geometry (do they teach geometry in high school any more?) knows that 2 points define a line and 3 points define a plane.  Quick quiz: what do 4 points define?

Most printers come with 4 "leveling" screws, one at each corner.  When you turn one of those screws clockwise, two things happen.  The corner of the bed plate goes down and the corner of the carriage plate goes up.  Nothing (or much less) happens at the other three corners which are held in position by their own leveling screws and springs, so the bed plate bends along a line between the adjacent corners.

4 point "leveling" is more accurately called 4 point bending.  Whose idea was this?



In an i3 type printer, the carriage plate has bearings or bushings that ride on the Y axis guide rails.  Those bearing/bushing locations and orientations are critical to proper operation of the Y axis.  By turning that "leveling" screw, you just bent that carriage plate that holds those bearings/bushings in alignment.  That can't be good!  The guide rails are pretty rigid, so bending the bed carriage plate isn't going to move the rails much, so the carriage plate and the bed plate are going to move in some rather complex way.  So, turning one leveling screw throws off the level at the other three.  Now imagine what happens when you twist all four screws while you're trying to level the bed.

Of course, the bed plate or the carriage plate are going to flex different amounts, depending on which is more rigid.  The bed plate should be flat, so you really don't want it to bend at all or you'll have trouble getting prints to stick to it.  The  carriage plate holds those critical bearings/bushings, so you really don't want it to bend at all, either.  Yet printers that come with 4 leveling screws almost always have thin, flexible carriage plates and thin, flexible bed plates.  Hmmm.

In printers with the bed moving in the Z axis, the bed support is usually solidly built, so it isn't likely to flex when you tweak a leveling screw.  That means the bed is going to do most of the flexing.  How can a bent bed be made level?  Autoleveling that maps the bed surface can compensate for this.

Printers that have four leveling screws usually have "special" sequences of tweaking the screws to try to get the bed leveled.  They invariably end up bending the bed.  Then people clamp glass to it to try to provide a flatter surface that prints might stick to.  But then it isn't evenly heated, so they do stuff (thermal pads, glue, hairspray, etc.) to try to compensate for that.  What a mess!

Three Point Leveling


With 3 point leveling, there are three screws, reference, pitch adjust, and roll adjust.  The screws are normally arranged so that two of them, reference and pitch adjust, are along the printer's X or Y axes. The roll adjust screw is usually located along an edge of the bed, opposite the other two screws.  The reference screw is used to set the overall height of the bed above the carriage plate and not normally used for bed leveling.  After initial set-up, only the pitch and roll adjust screws are used to level the bed.

Look at the image, below.  Notice that when you turn any screw, the bed is free to pivot at the other two screws, so nothing is forced to bend.  The bearings mounted on the carriage plate are not affected.

3 point bed leveling.  Adjusting any screw causes the bed to pivot on the other two screws.  Nothing is forced to bend. Leveling is accomplished by adjusting the pitch first, then the roll.  


To level a bed on 3 points for the first time, you move the nozzle to the reference adjuster and adjust the screw to grab a piece of paper, then move to the pitch adjuster and adjust the screw to just catch a piece of paper.  Finally, move the nozzle to the roll adjuster and adjust the screw to just catch the paper.  The roll adjustment does not affect the pitch setting because when you adjust the roll, the bed pivots on the reference and pitch screws.  After the first time, if ever, you adjust the level by simply tweaking the pitch and roll adjusters.  Always adjust pitch first, then roll.

Example 1:


In the example below, the bed moves in the Y axis.  The reference screw is at the back of the bed (hard to reach, so best not used for leveling) and the pitch adjust screw is at the front of the bed.  The pitch adjust screw adjusts the bed plate's pitch in the Y axis.  The third screw, the roll adjuster, is located at the left side of the bed and adjusts the bed plate's roll around the Y axis.

Son of MegaMax (SoM) bed plate showing level adjustment screws.


The screws can be placed anywhere that is convenient, but the best place to put them is close to the bearings that support the bed, because that's where the most solid structure is located.  In this machine there are two guide rails for the Y axis, one at about the center of the bed and the other to the left, near the edge of the bed.

The printer shown above is Son of MegaMax.  The bed leveling screws have flat heads that sit in countersunk holes so there's nothing for the extruder nozzle to crash into.  Originally, strong springs pushed the bed plate up against the screw heads.  The leveling is so stable in this machine that once set, it doesn't have to be adjusted unless the machine is taken apart for mods or maintenance, so the springs were replaced with nuts (if you allow something to move, it will!).

The bed plate itself is a piece of 1/4" thick MIC6 cast aluminum tooling plate.  That plate comes milled flat on both sides with plastic film to protect it until you use it.  It is flat enough to print on edge to edge and stays that way when heated.  The brown print surface is kapton tape but that has since been replaced with PEI.

85 wheels printed almost edge to edge on the plate.



Example 2:


We have a Taz 3 printer at the makerspace.  It originally came with a glass bed with 4 point leveling that didn't work well for reasons explained above.  Between the uneven heating of the glass and the leveling problems, we could only print near the center of the bed.  After the bed broke I decided to upgrade to a piece of cast aluminum tooling plate on a 3 screw leveling system.

Taz 3 printer modified undercarriage showing leveling screw blocks (white) and location of bushings for the Y axis guide rails.  4 bushings on the guide rails make about as much sense and 4 leveling screws!  The plate is quite flexible and I wasn't able to put the new leveling screws closer to the bearings, so this one is a little less stable than SoM, but still a huge improvement over the original design.

In this printer the reference and pitch screws are aligned parallel to the X axis.  The roll adjuster is at the back of the bed.  While it has been a great improvement, it is not as stable as the system in SoM because the rest of the printer isn't very solidly built.  As long as we don't move the machine, the bed stays level and doesn't require any releveling, but as soon as we move it, it has to be releveled.  The thermal performance improved drastically.

Taz 3 with the cast tooling plate bed installed.  The roll adjuster is behind the extruder.  We originally put PET tape on the top surface but recently replaced it with a layer of PEI because it works better.


Example 3:


My most recent printer design, Ultra MegaMax Dominator, uses a unique 3 point leveling scheme called a kinematic mount.  The idea was taken from an optical table lens mount. It still uses reference, pitch, and roll adjusters, but since the bed moves in the Z axis, I didn't have to put the leveling screws through the bed plate. The plate rests on top of the screws (held down by springs) which allows the plate to expand freely when heated without pushing laterally against the leveling screws.  More details can be found here.

UMMD's bed leveling scheme (and the rest of the construction) is so stable I can transport the printer laying on its back in my car and take it out and stand it up and start printing without any adjustments.

Here are flatness scans of UMMD's bed that was made by mounting a digital dial gauge on the extruder carriage and then slowly sweeping it over the surface of the bed.  The first is at room temperature, 19C, and the second is at 100C.  This type of scan measures several things at once- variation in thickness of the PEI print surface, the thickness of the adhesive tape that holds the PEI on the bed, the flatness (and level) of the bed plate, the sag in the X axis linear guide, and the sag in the printer's frame, rigidity of the Z axis mechanism, all of which will contribute to the "stickiness" of a print's first layer.


And a print that runs almost from the left edge to the right edge of the bed:

Base of a filament spool holder printed in PLA in 290 um layers using a 0.6mm nozzle.

All three printer examples above have 300 mm x 300mm bed plates.  The first two are 1/4" thick, the third one is 8mm thick.  All are flat enough for edge to edge printing in 200 um layers.  I can't say how big the bed can get and still be rigid enough to stay flat enough to print on with only 3 screws supporting it.  That will depend on the thicknesses of the bed plate and the first print layer.  Larger printers are typically used to print larger objects in thicker layers, and thicker layers are more tolerant of variations in flatness, so I suspect that 3 point leveling can be used to go quite a bit larger than 300 mm square, unless you're trying to print a 50 um first layer.  Guide rail sag is likely to be more of a problem than bed flatness.

In summary, 4 point leveling bends either the bed plate or support plate or both, which can be very hard to print on.  Autoleveling can compensate for that and get the prints to stick.  3 point leveling and solid construction eliminates the need for autoleveling or even releveling.  The only fix for tilted axes is to prevent them from tilting through good design (one motor driving both screws) or check and realign them frequently.  Autoleveling does not and cannot compensate for tilted axes.



48 comments:

  1. Mark Nice work!!!

    I'm converting my Mendelmax 3 bed to Linear rails from having the Rollers.

    I fabricated a 1/4" aluminum as the bed carrier for the 3/8" MIC6. I have 3 point leveling system using 40mm long m5 flat head screws with springs.

    Do you still recommend using springs or just level it then lock it in place with nuts?

    I know you mentioned on your SOM printer you said you changed out the spring with nuts.

    Thanks!
    Arnold

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    1. If you are the only one using the machine, springs are fine. I converted SoM to fixed screws and nuts because the machine was at a makerspace where people tend to try to adjust things if you make them easy to adjust.

      Delete
  2. Nice article! Helped me a lot to understand the leveling. Although i have a question. I have an ender 2 printer and can not really decide which screw is which (ref, pitch, roll) Could you help me with that? Thanks

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    1. If two of the screws are parallel to one axis, conside one of those to be the reference (it doesn't matter which), and the other the pitch screw. The third screw will be the roll adjust.

      Delete
  3. V-Slot® NEMA 23 Linear Actuator Bundle (Lead Screw)
    SKU:1175-BUNDLEUPC:819368022902
    Mark I know this probably wont be as accurate as your Z axis on your UMMB but do you think these will suffice? I've got 4 nema 23s looking for a project. FYI I modded my CR 10 last night to a 3 point leveling and got a dead on print first time. Thanks for the blog tip.

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    1. Sorry, I didn't see your comment until today, and I can find any reference to that linear actuator.

      Delete
  4. So i have a 6 hole bed.

    [1 2 3]
    [a b]
    [4 5 6]

    In this case, should I suppose to drill at (a) or (b)?
    but is it safe to drill a heated bed?

    Can I just put screws on 1, 3, and 5?
    or
    2, 4, and 6?

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    1. If it already has 6 holes, you can just use 3 of those to set up pitch and roll leveling. Use 1, 3, and 5, or 2, 4, and 6, or 1 , b, and 4, or 3, a, and 6.

      If the bed has a heater attached, you have to be extremely careful about where you drill holes- you don't want to drill through the heater!

      Delete
    2. Thank you very much. I asked because you used 3 middles of 3 sides.

      [A.B.C]
      [1.2.3]
      [D.E.F]

      You used points B,1,3 or 1,3,E. Combination of 1,B,3.E

      and mine is more on the sides (like A,C,E or C,F,1) so I think that might cause bad balance?

      Delete
    3. The balance is unimportant. I put the bed plate ears for the reference and pitch adjusters at the center of the plate because that's where the Z axis bearing blocks are. If I had put them at the far edge of the plate they would be about 150 mm away from the bearing blocks which would require a larger support structure and would not be as solid.

      Delete
  5. FYI: it's 'E'ffect. Affect is causal. :)

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    1. The grammar police have spoken!

      I used "affect" in two places in this post, and https://www.diffen.com/difference/Affect_vs_Effect says my usage is correct.

      Maybe there are different rules in Australia...?

      Delete
  6. Hi...New owner of an Geeetech i3 x pro, assembled by someone else. Alum bed is warped so I fitted a 5mm GLASS bed and have been level fiddling all day.Just read your article and tried with just 3 screws in the original corners, Seems to work fine as an interim measure. Unsure if ill alter the bed for the screws to be triangulated at this point. Different but the geometry still works for me. thanks for the tip...

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  7. Great article. I had been thinking about going to a 3 point system for some time. My Ft-5 originally had 8 adjustment points and was a bear. I cut it down to the four corners and it became easier. With three I think it will be a snap.

    I will run my bltouch (9 points) with the Octoprint mesh leveling test for comparison before I move to 3 point. Then I will rerun the tests to see what happens. Additionally, I will run the tests with the bed cold and again hot (say 100C) to get see if there is any warp due to the heat. I will come back and tell you what my results were.

    Incidentally, trying to get a better multi-point level by adjusting the corners based on the mesh tests was always very difficult. Should be easier.

    Thanks for the article!

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    1. Thanks! I look forward to seeing your test results.

      Delete
  8. The post is a bit older, but I like the approach very well. I have a large heating bed (300x300) and also have 4 points. It is almost impossible to level the bed properly. Your method is very promising and so I will retool my printer and see if it works that way.
    The explanation is really good and obvious. Thank you for the great work and detailed presentation of the connections.
    Arens

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  9. Mark - This is a great article, very nicely explained!
    I took my 1st printer, a Monoprice Select v2 (Wanhao i3 clone), to a 3 point system and have been intending to do so on my CR-10S.

    I once posted a rather passionate post on a CR-10 forum trying to get people to understand the concept of tramming, after answering for the tenth time that putting a bubble level on the bed was NOT how you "leveled the bed", LOL!

    Not an engineer, but I get the basic physics of it and hope to switch to a linear rail Y axis and convert it to 3 point soon once it gets by the "Finance Committee" {Ahem} my Wife ... ;-) Cheers!

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  10. Thank you Mark for a great article. The fact that it's still top 5 in a Google search after 2 years speaks to that.

    I am tired of the leveling dance on my current printer (Anet E12). I have considered a 3 point system since I heard about it last year. My main question though is can I utilize the existing holes on my hotbead (on each corner)? If so, what do I do with the 4th hole? I'm guessing that I fix it in place at a given height and leave it don't touch it. If that's the case, do you have any recommendations on what to use for fixing it in place? Screw and wing nuts, lock washers, aluminum post with the screw and nut?

    Thank you to everyone in the hobby I appreciate all the help I have received!!

    73

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    1. Thanks!

      I don't know what the bed plate is like, but if it's the flexible type, you'll need to put something adjustable under that 4th corner to support it, or it may flop around during printing. I'd probably use a screw/post and a spring to hold the corner down on that post. I'd probably level the plate by the pitch/roll technique using the other three screws, then tweak that 4th support to just bring the corner of the plate up to level with the rest of the plate. It's still 4 point leveling, but without moving the leveling screw locations there's not much more you can do.

      Delete
  11. Very impressive work, and really well detailed "how to". This article is pure gold !

    3 years after you wrote this, manufacturers still rely on that 4-point thing (notable exception : Prusa and their i3 MK3 bed, with a fixed ref at bed center and 8 adjustable points. 8-way bending ?).

    Anyway, your article confirmed what I supposed, both on 4-point "leveling" and Z-probe.

    My printer (name and shame : i3 Mega-S) also has 4-point thing, and I never really managed to get the bed as wanted, though everything has been checked and set "square". Minus the Y axis. Linear rods have some flex due to the Y carriage.

    After reading (4 or 5 times) what you wrote, I decided to follow the 3-point leveling system (with added linear rails for Y axis) while entirely changing the bed design.
    Still have to go to CAD before, so some shop will do all the required holes in a cast aluminum plate (either MIC6 or ALCA 5).

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    1. Thanks! Please post the results of your modifications.

      Delete
    2. I will.
      As for now, I'm still in the process to lay everything down on paper. There is quite a bit of things to prepare, as a 240x220mm silicon heater which has holes on each dorner (duh...) would be used as heat source.
      Have to check if a 250-260mm wide plate would fit the printer structure with the adjusting wheels.

      Was wondering ... Could it be possible to use locking nuts encased in printed thumbwheels instead of springs ?
      As for the holes in the bed plate, how oversized should they be ? Say, if M4 screws were to be used, should the holes be really larger ?

      Delete
  12. Using springs allows the bed to pivot when the leveling is adjusted. If you use locking nuts, something is going to have to flex a bit when the adjustments are made. Have you looked at using a kinematic mount? See: https://drmrehorst.blogspot.com/2017/07/ultra-megamax-dominator-3d-printer-bed.html for the concept and https://drmrehorst.blogspot.com/2019/01/son-of-megamax-gets-new-y-axis.html for the design applied to a bed flinger.

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    1. Sure. It's a very clever idea, though it seems very difficult to fit on the i3 Mega, due to the way it's built. On the other hand, it might be done on a future printer that I'll build by myself.

      You're right about springs vs locking nuts. Makes whole sense : we want the bed to pivot and stay flat, not to flex.
      Looks like a 4-mm MIC6 plate will be a better option than the 3-mm that was initially planned.

      Everything's clear :) Should be quickly done, just waiting for the plates to be delivered.

      Delete
    2. I've never seen 3 and 4 mm MIC6 plate. I thought it started at 6 mm thick. Let me know how it goes.

      Delete
    3. I'm still in the "thinking / design" process. So, the MIC-6 plate and 3-point leveling are not done ... yet.

      Some late design flaws have been discovered and there HAD to be fixed. Like the print head block that wasn't squared, and getting rid of the highly non-efficient 12V PCB heater in favor of a mains silicone heater.

      Anyway, speaking of cast aluminium plates, I've found some starting from 5mm thickness. It should be plenty ok.

      Yet, given all the discussed things, about frame squaring and such, I'm wondering if something else could be an option.

      If you know :
      - your frame is squared
      - Z-motors are synchronized (either with belts or Marlin's G34 "z-stepper auto-align")
      - and your bed being flat by design

      Therefore maybe the leveling springs could be removed in favor of rigid aluminum spacers ? Still on 3 points, though.

      I don't know, that's something that seems to make sense to me. Do you see any disadvantage to that kind of design ?

      Delete
    4. I put lock nuts on a printer at the makerspace instead of springs mostly because people kept turning the screws when there were springs there. I spent a lot of time trying to relevel the bed after noobs messed with it.

      Lock nuts aren't ideal. They will force to bed to flex a bit when you're adjusting the leveling. The best approach is a kinematic mount where the bed sits on top of the leveling screws and springs hold the bed plate down on the screw heads.

      Delete
  13. Very good article. Thank you. I tried a good quality three point leveling kit on my Ender 3 and learned why, though logically sound, three point leveling does not always work. My printer's heated bed plate is not perfectly flat. Despite the stiffener plate provided for the side of the three point carriage that has only one height adjuster (right side), the back portion of the bed was higher than the front portion. I had no available adjustment remaining on the back left side and the front left side adjustment did nothing to correct the problem. This is where four point adjustment proves to be the better solution. I was able to reinstall my original carriage and use the back right adjuster to correct for the non-flat bed.

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    1. Interesting. If the bed isn't flat it's anyone's guess what it will take to flatten it. Good on you for getting it working!

      Delete
  14. Hi, I stumbled onto your page while searching for upgrade options for my Taz4 bed. You mention the 4 Y rail bushings to be just as bad as 4 point leveling. Did you consider changing it to 3 bushings instead of 4? Just remove one from one rail and re-drill the carriage plate to center one of them. Then do 3 point bed mounting like you did above.

    I'm still considering if it's worth putting the effort into this "old" printer or just go with a newer better designed frame(any suggestions?).

    ReplyDelete
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    1. If all you need to do is fix the bed problem, it's relatively simple, so I'd do it, but once you start looking at the printer critically, you may find you want to replace the extruder and carriage, etc. Then it isn't such an easy decision. Those machines are full of printed parts that make it a less than solid machine.

      Delete
  15. Mark, I enjoyed the article. Do you think that this method would work on a router CNC. Instead of trying to level the router by adjusting screws on the gantry, if I taped three holes into the bottom where the router sits. Insert 3 screw with nuts to lock them in place once the router is level using the 3 point method.
    Thank you

    ReplyDelete
    Replies
    1. I think that would work fine. The bottom of the router is supposed to be a flat plate. The way to level a flat plate is to use 3 points.

      Delete
  16. Mark I did not try to level the router. When I first looked at it, I thought that I could use your three point method. However, in order to level it, I would need to shim the y direction and adjust the screws holding the z axis for the x direction. I just used a small bit to level the spoil board. It is not the best solution but something that I could do and then work on other projects.
    Thank you for your comments.
    Harvey

    ReplyDelete
    Replies
    1. Unlike a 3D printer, you can always level the bed surface using the tool in a mill or router.

      Delete
  17. Hi,

    Loved you idea on 3 point levelling, I have been struggling to level my Alfawise U30 for ages now. I get it printing then for whatever reason it goes off and I spend days messing about trying to level it. The problem I have is actually that the y carriage rollers when adjusted to firm up the build plate and move back and forward without cogging alters the build surface enough so that the bed can be out. It can move the bed enough to have high spots at differing points making it impossible to get a good level. I take out a high spot and it just moves elsewhere on the build surface. I have spent days trying everything to get it to print with no luck at all. It either prints in parts or filament balls up around the nozzle or the prints pulls off the surface AHH I am going mad with this dam machine. Hope have a suggestion as I am ready to take a hammer to it at the minuet.
    Regards

    Gary

    ReplyDelete
    Replies
    1. It sounds like the bed is flexing. Maybe you can try to use a 3 point leveling system and see if that stops the flexing. Maybe it will be flat enough to print on- if not, replacing the bed plate with one that is flat and using a 3 point mount should fix it. The kinematic mounts in the four printers I have put them in all work perfectly and are so stable that you don't have to relevel the bed after initial setup. That initial setup is very easy, too.
      It's best to start with a flat plate- cast aluminum if you can get it.

      See: https://drmrehorst.blogspot.com/2019/04/more-changes-to-ummds-z-axis.html
      https://drmrehorst.blogspot.com/2019/01/son-of-megamax-gets-new-y-axis.html

      Delete
  18. Hello,

    Thank you for the article. I have ordered some hardware for my Ender 3, linked below, but have a software question.

    Marlin supports 4 point bed tramming just fine. Does anyone know how to get it to do 3 point tramming? Please note, I'm not asking about 3 point auto leveling. Thank you in advance.

    This is the bed I ordered, drilled with 6 holes, no magnets:
    https://mandalaroseworks.com/products/ender-3-magbed

    This is the bed carriage:
    https://gulfcoast-robotics.com/collections/heated-beds/products/modular-y-carriage-plate-upgrade-creality-ender-3-point-leveling

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    1. I'm not sure what you're asking. Autotramming is autoleveling. Maybe who knows more about Marlin can help here.

      Delete
    2. I've not used Marlin in a long while now, having move to Klipper. Principle is the same, though.
      Within Marlin, in config_adv.h, line 984, there is an option called "ASSISTED_TRAMMING" (gcode command G35) which can be configured to work with defined points/coordinates (in XY plane). It REQUIRES a probe to operate.
      It's easy : define your 3 points coordinates in config_adv.h in the right block, point names (with 3, it should be "Ref", "Pitch", and "Roll"). You can also enable a report on Z deviation (in mm) and a few other options.
      Have a look at it, it might answer your question. :)

      Delete
  19. I just bought a 3d printer, I fastly read about leveling the bed, and no matter how hard I tried, once the corners were leveled with the feeler gauge, the center was always hitting the nozzle. Then it hit me, who the heck came up with the idea of leveling a plane with 4 screws? That's pretty insane thinking that no real engineer will ever do that. Thanks for this! Perhaps the manufactures will read this article, or perhaps hire a real engineer to design things like that!

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    1. When heat is applied to one side of a poor thermal conductor such as a PCB, the heated side expands more than the unheated side resulting in the whole thing warping, with the degree of warp being a function of the temperature. If that temperature isn't well regulated, the bed will rise and fall with the temperature changes (it only takes a few C) and it will create z artifacts in your prints.

      There are quite a few manufacturers and hobbyist designs that are paying attention to the bed and its mount. A lot of designs and products out there use kinematic mounts and to support flat beds. You have to pay a bit more to get or build those features, but I'd say they're worth the extra $ if you're concerned about reliability of the printing process (and if you aren't now, you will be after experiencing a bunch of print failures).

      Delete
  20. Does that mean Voron 2.4’s quad gantry leveling is flawed by design?

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    1. In general, using four screws or belts to lift a planar rectangular object (like using 4 screws to level a rectangular bed) is a bad idea unless the part being lifted is flexible. If it's flexible, then 4 or more screws or belts may not be a bad idea because they will help keep the lifted object close to planar.

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  21. Well written, well explained.

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