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Tiago
(@tiago-2)
Reputable Member
Fix bed variance / warp using flat springs

This guide is about fix bed variance / warp
This will give you total freedom to do the adjustments and steps you want.
Get your first layer perfect again!

Background: https://shop.prusa3d.com/forum/assembly-and-first-prints-troubleshooting-f62/live-z-can-t-get-a-perfect-even-surface-t22944.html

From 1.071mm:

To: 0.009mm:

What you need:

  • 9 x M3 20mm flat screw for bed

  • 9 x Red Flat spring 6mm x 3mm x 15mm (Other sizes will also do just don't buy a very tall spring [10mm height is optimal], or cut a tall spring into more springs)

  • Octoprint with Prusa Mesh Leveling Plugin

  • Patience and many tries
  • Why flat spring?

    First because they are flat, so better surface contact, they support big loads, have high compression rate and do not deform like a regular spring, they stay straight when pressed. I can't compress the spring with my fingers, need three fingers to see some compress, but screws will do the job don't worry.
    So don't buy regular springs, they will not perform the same!
    You can also press the bed without descalibrate your variance.

    I buy these:

    I can't post the link because it's not avaliable anymore, so you have to found them anywhere else.

    David.f42 found these on Ebay from this seller: https://www.ebay.com/itm/142187956825

    How to install

  • Remove screws and spacers from bed and save them on a zip-bag

  • Insert the new 20mm screws on every 9 slot and push them

  • Insert the spring at each screw thread, springs will not fall as ID match the screw

  • Align bed in place and match the holes

  • Tight the center screw only to hold the bed (Don't full tight! just to hold! Once screw lock into carriage frame)

  • Do the rest for all other screws, order don't matter with that method

  • Once you have tiny tight all the screws, tight with a full turn 360º, start on center and respect manual order

  • Now tight all screws equal, i like to apply very tiny force, so when key stop it mean is good and go to next screw, this should not mean that screw is full tight at max! Repeat this so you can't move the key at any screw with that tiny force.

  • Run "Prusa Mesh Leveling Plugin" and from there ajust one to two or three screws at a time, for big variances you can go 45º turn at a time, for small variance you need to go babysteps turns. Note: I do this with cold printer to speed up, now ambient air is 35ºc to 40ºc so i don't need to heat up at all, but if for you is very cold ambient it may be good to heat one time and do many steps as you can.

  • Repeat as you get very low variance, don't need to be perfect 0, go as you like, something like 0.02-0.07 is good.
  • NOTES:
    ➡ It's normal if you fell one screw much more tight than the others and still you need to tight it more, that mean you bed is warp heavy on that side and also that give you a tip how bad bed is on that spot 💡
    ➡ My was top right and it fell good after you know you are fixing the bed warp, so with the time, heat and force it can fix that warp 😉
    ➡ Screws shoud be tight with care, and at end the spring shouldn't be full compressed/strong tight, the spring should able to compress more if necessary. So don't go full tight nor loose tight. Bed shall not move when you remove the magnetic sheet
    ➡ A higher variance on a point don't strict mean you have to tight that point, sometimes you need to loose the other points, that can be found when screw is already tight and you fell hard to screw it more, so if that happen you need to loose adjacent screws to compensate.

    When you finish redo the last point but heat up the bed and pinda to 35ºc
    Script:

    M106; Fan on to cooling down pinda
    G28 W ; home all without mesh bed level
    G0 X50 Y50 Z70 F1500 ; Raise PINDA in case cooling is needed
    M860 S35 ; Wait for PINDA <= 35C
    M190 S60; set and wait for bed temp
    M107; Fan off
    M104 S170 ; set nozzle temp
    G0 X50 Y50 Z0.15 F1500 ; this is a good PINDA heating position
    M860 S35 ; wait until PINDA is >= 35C
    M104 S0 ; turn off temperature
    M140 S0 ; turn off heatbed
    G80 ; mesh bed leveling
    G81 ; check mesh leveling results
    G4 ; wait
    G0 X50 Y50 Z70 F1500 ; Raise PINDA back for next iteration
    M84; Motors off
    M300 S2600 P100; Beep

    If is OK run self-test and redo XYZ calibration, run "Prusa Mesh Leveling Plugin" to check one more time.
    Heat bed to 100ºc and leave that for 20m, cooldown to ambient air or 40ºc, wait for pinda 35ºc and run the "Prusa Mesh Leveling Plugin" to do the last check.

    💡 Do a check from time a time, as told, heat can expand the bed, this is easy and not take much time
    Depending on the height of the spring and your tight force you may lose some mm of Z, so don't forget to run Self-test + XYZ (Wizard) and maybe will require firmware hack to XYZ work again

    Posted : 07/08/2018 9:14 pm
    dimprov
    (@dimprov)
    Noble Member
    Re: Fix bed variance / warp using flat springs

    Impressive!



    I can't post the link because it's not avaliable anymore, so you have to found them anywhere else.

    Anyone found the springs for sale somewhere?

    Posted : 08/08/2018 11:56 am
    Tiago
    (@tiago-2)
    Reputable Member
    Topic starter answered:
    Re: Fix bed variance / warp using flat springs

    I try to find them, but they are rare, i can't see 3mm ID anymore on aliexpress.
    The good thing is you can go with any ID and OD as long it fit all OD on the frame. So you can go with: https://www.aliexpress.com/item/Medium-Load-Red-Spiral-Stamping-Compression-Die-Spring-8X90mm/32771801125.html

    Go with 8x4x100, cut that into 10 equal pieces (10mm each) and you are good. Even if they aren't cut equal it don't matter, they are springs and can be ajusted latter 😉
    Always go Red Spring.

    Posted : 08/08/2018 3:53 pm
    dimprov
    (@dimprov)
    Noble Member
    Re: Fix bed variance / warp using flat springs

    I just now ordered some on Ebay from this seller: https://www.ebay.com/itm/142187956825

    Posted : 08/08/2018 8:54 pm
    Tiago
    (@tiago-2)
    Reputable Member
    Topic starter answered:
    Re: Fix bed variance / warp using flat springs


    I just now ordered some on Ebay from this seller: https://www.ebay.com/itm/142187956825

    Nice find, i will update op with that. Thanks.
    EDIT: Well i can't edit anymore...

    For people who wasn't to lose much Z go with 10mm, they maybe don't exist avaliable to buy, but they can be cut, and after that compress them about 5mm
    I'm with 190mm MAX Z right now (Volcano + Springs)

    So go with that link and buy 6x3x100mm and cut into 10mm pieces

    Posted : 08/08/2018 9:24 pm
    JoanTabb
    (@joantabb)
    Moderator
    Re: Fix bed variance / warp using flat springs

    Hi Tiago,

    I added the link in your first post for you,

    regards Joan

    I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
    Posted : 08/08/2018 9:34 pm
    dimprov
    (@dimprov)
    Noble Member
    Re: Fix bed variance / warp using flat springs

    I wonder why this works better than mesh bed leveling? It's the same nine points.

    Posted : 09/08/2018 1:15 am
    Tiago
    (@tiago-2)
    Reputable Member
    Topic starter answered:
    Re: Fix bed variance / warp using flat springs


    I wonder why this works better than mesh bed leveling? It's the same nine points.

    This is to fix the bed variance, mesh bed leveling is not 100% accurate and severe warp can be problematic even with the mesh bed leveling.
    This mod is not to replace mesh bed leveling procedure, rather that is to work with and get better layer results and less error from mesh leveling.

    Stock bed lock with spacers have some problems:
    You can do your best to put equal force to all screws, but one or other will be tighter, overtime that will warp your bed, i also got a flat bed, but after a time it start to warp on a spot. Lock rigid bed into rigid frame with no space to expand is a bad option imo. Think like the bridges, they always have a small gap where it start or end or at segments, they are not connected at both ends, so the concret can expand with the time and temperature, and not colapse due no space to expand and contract. Briges would fall and crack without that small gaps.

    So the springs will relieve bed pressure and also will allow to expand and contract without any problem, bed will not deform as easy. As bonus it can fix your bed warp overtime.
    Due to screw if you pull bed up it will not move, it's locked at top, but free at bottom, if you push hard down it will move, but due the nature of the springs it will get back to original position as soon you release the push, flat springs don't have memory. You can damage your Y if you try push that thing, the springs are really strong, and they are medium compression (red) 😀

    ➡ Before my bed lived inside a jar, now it grow in a vase 😀

    Posted : 09/08/2018 2:44 am
    dimprov
    (@dimprov)
    Noble Member
    Re: Fix bed variance / warp using flat springs

    I've certainly had occasions where mesh bed leveling didn't seem to work well enough, so I'm game to give it a try. I'll report back after I receive my springs, which may take a month to receive from China.

    Posted : 09/08/2018 10:55 am
    Tiago
    (@tiago-2)
    Reputable Member
    Topic starter answered:
    Re: Fix bed variance / warp using flat springs


    I've certainly had occasions where mesh bed leveling didn't seem to work well enough, so I'm game to give it a try. I'll report back after I receive my springs, which may take a month to receive from China.

    You can check your atual mesh map with the plugin, if your variance is little or you can get perfect first layers then you don't need this mod.

    Posted : 09/08/2018 4:30 pm
    dimprov
    (@dimprov)
    Noble Member
    Re: Fix bed variance / warp using flat springs

    I don't know what size these springs are, but they are described as "strong": https://www.aliexpress.com/item/Titan-Extruder-Strong-Spring-For-3D-Printer-Parts-Extruder/32811213869.html?spm=2114.33020108.8.15.292bkyCskyCsvE&scm=1007.17258.98095.0&pvid=39355110-2af5-4e9e-ad6a-3ef6553722dd
    Inexpensive.

    Posted : 17/08/2018 11:27 pm
    Tiago
    (@tiago-2)
    Reputable Member
    Topic starter answered:
    Re: Fix bed variance / warp using flat springs

    They lack of specs, normally flat springs have colors to identify the compression force.
    But they can be a good bet, i will ask for sizes

    Edit: They look like 10mm, they have 6 turns, the 15mm have 10 turns
    And i think they are M4 since titan use M4 thumb screw, 4mm ID spring will work for this mod as well

    Posted : 18/08/2018 1:55 am
    themzlab
    (@themzlab)
    Estimable Member
    Re: Fix bed variance / warp using flat springs



    I wonder why this works better than mesh bed leveling? It's the same nine points.

    This is to fix the bed variance, mesh bed leveling is not 100% accurate and severe warp can be problematic even with the mesh bed leveling.
    This mod is not to replace mesh bed leveling procedure, rather that is to work with and get better layer results and less error from mesh leveling.
    .......

    tiago, this is a great idea! thanks for spending the time to put this together.

    I did a very similar modification except I used shorter spacers and a short stack of disk springs - which was a pita to assemble. The heavy springs you suggest are a much easier solution.

    I did not have any problems before doing the project but I did notice that the Z motor was moving around to compensate and I thought printing would be more stable without this motion.

    I don't think it was mentioned how to do the adjustment in terms of the details. What I did is to take an average of the mesh measurements that are returned and then subtract this from the 9 points that line up with the measurements. This gives a plus/minus value that all average together about 0. The pitch of the screws is 0.5mm so if you want to know how many degrees to turn each screw this is 360/0.5 * error or 720 * error. The pattern of the screws is not precisely the same as the measuring points so you may need another fudge factor - I computed one but this is a long time ago and I forgot what it was - sorry!

    I went around the bed and turned each screw according to the math (example, one is +45 degrees, another is -30 degrees...) and that was good enough for me - just one trip.

    My print results are the same as before except now the Z axis screws do not appear to turn while laying down the first layer.

    Posted : 18/08/2018 3:52 am
    Tiago
    (@tiago-2)
    Reputable Member
    Topic starter answered:
    Re: Fix bed variance / warp using flat springs


    tiago, this is a great idea! thanks for spending the time to put this together.

    I did a very similar modification except I used shorter spacers and a short stack of disk springs - which was a pita to assemble. The heavy springs you suggest are a much easier solution.

    I did not have any problems before doing the project but I did notice that the Z motor was moving around to compensate and I thought printing would be more stable without this motion.

    I don't think it was mentioned how to do the adjustment in terms of the details. What I did is to take an average of the mesh measurements that are returned and then subtract this from the 9 points that line up with the measurements. This gives a plus/minus value that all average together about 0. The pitch of the screws is 0.5mm so if you want to know how many degrees to turn each screw this is 360/0.5 * error or 720 * error. The pattern of the screws is not precisely the same as the measuring points so you may need another fudge factor - I computed one but this is a long time ago and I forgot what it was - sorry!

    I went around the bed and turned each screw according to the math (example, one is +45 degrees, another is -30 degrees...) and that was good enough for me - just one trip.

    My print results are the same as before except now the Z axis screws do not appear to turn while laying down the first layer.

    Yes there are other ways, like wave washers and others, but you loose the ability to do ajustments as you want. With wave washers once they are full compressed they become flat, and if you need to go up on that point you will need a new washer and make all over again, math is important there. So that way i look at this kind of springs (I used them before on other printer) and why not give it a try? Well they work very well, problem free, easy to assembly and i think they should be standard with mk3. As downside is time consuption to get it perfect, but each one know best. Both my MK2S and MK3 don't have problems at first, but after a short time guess what, bed warp and first layer never went good, so i recomend this even if not having problem now, because with time, heat and force bed will deform.

    I have order the last springs suggested by david, the short ones, they seen low height, maybe they can do the work and keep same Z.
    I will inform back when i got them and test (+/- 1 month)

    Posted : 18/08/2018 4:25 am
    themzlab
    (@themzlab)
    Estimable Member
    Re: Fix bed variance / warp using flat springs

    hi tiago.c,

    I do agree with you, the springs you found are better.

    I didn't mean to imply I had a better solution just explaining what I did and I think it is an option people can use but with the biggest downside being that my assembly was extremely hard to put together.

    If a person does the adjustments by math it should work out that the bed can be flattened and if the springs end up too tight, simply go around and loosen everything 0.5 turns or tighter 0.5 turns and so on.

    I also want to warn about the tapped holes. I don't know how many machines will be this way but I found that I had to run a tap through my frog plate to clean the threads on a couple of the holes. I don't know if it came from the factory this way or if I damaged it at some point. If a person finds resistance in turning the screws in they may need to purchase an M3-0.5 tap.

    Posted : 18/08/2018 4:40 am
    themzlab
    (@themzlab)
    Estimable Member
    Re: Fix bed variance / warp using flat springs


    hi tiago.c,

    I do agree with you, the springs you found are better.

    I didn't mean to imply I had a better solution just explaining what I did and I think it is an option people can use but with the biggest downside being that my assembly was extremely hard to put together.

    If a person does the adjustments by math it should work out that the bed can be flattened and if the springs end up too tight, simply go around and loosen everything 0.5 turns or tighter 0.5 turns on all if you want more compression to hold the bed to the springs.

    I also want to warn about the tapped holes. I don't know how many machines will be this way but I found that I had to run a tap through my frog plate to clean the threads on a couple of the holes. I don't know if it came from the factory this way or if I damaged it at some point. If a person finds resistance in turning the screws in they may need to purchase an M3-0.5 tap.

    Posted : 18/08/2018 4:41 am
    andrew.m70
    (@andrew-m70)
    New Member
    Re: Fix bed variance / warp using flat springs

    I picked up the same 15mm die springs and have them installed. I got the bed nice and level using the mesh level. However, when attempting the XYZ calibration, the nozzle hits the bed and stops the calibration before the step of calibrating the mesh leveling points. Is there a trick to making that work considering the difference in bed height with springs now added? I figured the home calibration in the self test (which runs fine) would find the new level and the rest of the calibration fine.

    Posted : 24/08/2018 11:38 pm
    Tiago
    (@tiago-2)
    Reputable Member
    Topic starter answered:
    Re: Fix bed variance / warp using flat springs


    I picked up the same 15mm die springs and have them installed. I got the bed nice and level using the mesh level. However, when attempting the XYZ calibration, the nozzle hits the bed and stops the calibration before the step of calibrating the mesh leveling points. Is there a trick to making that work considering the difference in bed height with springs now added? I figured the home calibration in the self test (which runs fine) would find the new level and the rest of the calibration fine.

    Yes thats normal, because MK3 measures the Z height, and if far from preset it will trigger error. Auto Z Height must be requested and added to public firemware, that would solve many problems with custom mods like volcano.
    To solve that the only way is modify the firmware and reflash, you need to define less Z now.

    Solutions:

    1) Order 90mm or 100mm spring and cut into 10mm springs
    2) Cut your springs to have 10mm and compress them to 5mm.
    3) You can also try compress the 15mm springs down to 5mm and test, i think bed will hold fine
    4) I have ordered 5mm springs from ali and i will test them when arrive, if they are ok i will recommend that to not lose Z or have to reflash

    Posted : 24/08/2018 11:50 pm
    andrew.m70
    (@andrew-m70)
    New Member
    Re: Fix bed variance / warp using flat springs



    I picked up the same 15mm die springs and have them installed. I got the bed nice and level using the mesh level. However, when attempting the XYZ calibration, the nozzle hits the bed and stops the calibration before the step of calibrating the mesh leveling points. Is there a trick to making that work considering the difference in bed height with springs now added? I figured the home calibration in the self test (which runs fine) would find the new level and the rest of the calibration fine.

    Yes thats normal, because MK3 measures the Z height, and if far from preset it will trigger error. Auto Z Height must be requested and added to public firemware, that would solve many problems with custom mods like volcano.
    To solve that the only way is modify the firmware and reflash, you need to define less Z now.

    Solutions:

    1) Order 90mm or 100mm spring and cut into 10mm springs
    2) Cut your springs to have 10mm and compress them to 5mm.
    3) You can also try compress the 15mm springs down to 5mm and test, i think bed will hold fine
    4) I have ordered 5mm springs from ali and i will test them when arrive, if they are ok i will recommend that to not lose Z or have to reflash

    Oh OK that makes sense. Thank you. I ordered 20 springs. So I will try to cut them first.

    Is there a guide to customizing the firmware so I can see if that route is worth taking?

    Posted : 24/08/2018 11:57 pm
    Tiago
    (@tiago-2)
    Reputable Member
    Topic starter answered:
    Re: Fix bed variance / warp using flat springs


    Oh OK that makes sense. Thank you. I ordered 20 springs. So I will try to cut them first.

    Is there a guide to customizing the firmware so I can see if that route is worth taking?

    Print a 10mm tall tower to help cut springs about same height.

    Yes, readme: https://github.com/prusa3d/Prusa-Firmware
    Once you can compile the firmware its very easy to make changes

    Posted : 25/08/2018 1:07 am
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