Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one Hi guys, I am sure somebody else already thought about it and implemented it so I am asking those guys to post their solutions in this thread I am starting. My reasoning is that if one of the 3-points is fixed at a certain pre-determined height the other two points can be thumbscrews that adjust the plane relative to that pre-determined height. This way the complexity of the bed assembly decreases a bit and the adjusting can only be done from the front instead of reaching to the back of the printer where the third thumbwheel would be positioned. https://reprap.org/forum/read.php?1,669872,669872#msg-669872 Thu, 14 May 2026 06:55:03 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?1,669872,684048#msg-684048 Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one https://reprap.org/forum/read.php?1,669872,684048#msg-684048
Oh wait... the old water cooling gear... I have tubing!]]> Milton General Mon, 04 Jul 2016 13:56:01 -0400 https://reprap.org/forum/read.php?1,669872,684004#msg-684004 Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one https://reprap.org/forum/read.php?1,669872,684004#msg-684004
Quote
lhartmann
...
P.s. Loved the piezo auto leveling. Where can I find more details on the hardware/firmware?

Thingiverse at [www.thingiverse.com]
Discussion on [forums.reprap.org]

I use standard Repetier firmware although it would be improved by having some code that introduced a short delay before the Z down movement.

Mike]]> leadinglights General Mon, 04 Jul 2016 10:59:17 -0400 https://reprap.org/forum/read.php?1,669872,683965#msg-683965 Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one https://reprap.org/forum/read.php?1,669872,683965#msg-683965
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Milton
...
So has anyone made a vertical brace for the edges of a heat bed that allows it to travel vertically but not horizontally in relation to the Y carriage? I am printing tests of that, but are there any known issues there? Like 'oh man everyone did that 3 years ago but it causes X horrible problem!' type info is sorta what I am after here, as well as any and all good advice.
...

Instead of trying to brace the corners laterally to prevent bed plate wobble, try bracing the leveling screws so they don't allow the bed plate to wobble.

I use three teflon blocks with holes for the leveling screws, firmly screwed to the undercarriage plate. The leveling screws go into the blocks at least 12 mm and are held very firmly so they can wobble. The leveling screws have flat heads and the bed plate, 1/4" cast aluminum, holes are countersunk so the screws sit below the surface of the plate.

In my printer the alignment screws at at the center of the bed plate in the the X direction, controlling pitch in the Y axis, and at the left side of the bed, controlling roll about the Y axis. You can see how the bed leveling is done by clicking the link in my sig, below. I recently converted a Taz 3 printer to a cast tooling plate bed with 3 point leveling. You can see details of that here: [www.instructables.com]


]]> the_digital_dentist General Mon, 04 Jul 2016 08:55:14 -0400 https://reprap.org/forum/read.php?1,669872,683964#msg-683964 Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one https://reprap.org/forum/read.php?1,669872,683964#msg-683964
An option is to use a head tilt switch to cut the main power supply, this way you don't rely on the already misbehaving firmware to save your printer.

Obviously for safety reasons the tilt switch should drive a relay, not mains directly.

P.s. Loved the piezo auto leveling. Where can I find more details on the hardware/firmware?]]> lhartmann General Mon, 04 Jul 2016 08:54:09 -0400 https://reprap.org/forum/read.php?1,669872,683921#msg-683921 Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one https://reprap.org/forum/read.php?1,669872,683921#msg-683921
As for bracing the bed, have a look online at bed mounts for delta printers, which you might be able to adapt. These often need to support a round bed, albeit a fixed immobile one, allowing some vertical movement but no lateral movement.

Here are some examples: [www.thingiverse.com]

The issue really is that the i3 and its derivatives suffer from a small loss in print quality because the y axis and therefore the bed moves. Deltas achieve a fixed bed, at the cost of considerably harder calibration and precision required when building, corexy/hbot type machines manage to only move the bed in z direction which is preferable as these are very slight movements.]]> DjDemonD General Mon, 04 Jul 2016 06:07:09 -0400 https://reprap.org/forum/read.php?1,669872,683919#msg-683919 Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one https://reprap.org/forum/read.php?1,669872,683919#msg-683919 [attachment 80770 PTFEbushes.png]
This is fairly effective although I am still looking for something better.

Mike]]> leadinglights General Mon, 04 Jul 2016 05:43:45 -0400 https://reprap.org/forum/read.php?1,669872,683915#msg-683915 Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one https://reprap.org/forum/read.php?1,669872,683915#msg-683915
Is 4 point leveling possibly a 'borrowed practice' from leveling machines with solid cast iron frames that need 4 or more contacts to support the weight without a fairly massive 3 point hinge system? It seems likely to me that someone looked at how a mill or lathe was leveled and figured 'lets just do it like that and move on to the next problem' which is understandable, but not the best design for the problem.

So, wanting a 3 point leveling system I have started to think about it. Before printing something fancier though, I modified my off the shelf i3 with a quick 3 point leveling hack I wanted to ask about, ask some experienced people if I am going to run into some unforeseen problem.

I simply removed a spring and the adjustment thumb screw below the carriage on the back right corner. It creates an axis between the front right and back left springs/screws, I adjust the roll for the plane of the heat bed and glass print surface balanced on this axis with the front left spring and thumb screw.


How I level with this setup:
level the extruder first to the back left with both the front corners lower. Move the extruder to the front right avoiding the rear right of the heat beds possibly higher triangle, and get it close but not exactly dialed in. Then move the extruder to the front left and dial it to the back left so I can move the extruder (actually moving the Y carriage) front to back leveled, then with extruder again at the front of the table I move it right and dial the right side in. The back right corner is free hanging and upon checking it is level and the whole bed is possibly perfectly level

It is with a glass bed upgrade printing to .02 corner to corner on some pillow blocks made as a 4 part set, so spanning at least 100mm of the center of the heat bed. I was planning on making a 3 point mount, but barring some unforeseen issue this 2 diagonal 'main' level points and a 3rd adjustment of roll at a corner seems pretty good at providing a level plane without a 4th point pulling it out of alignment into a concave or convex surface.

That is unless there is some unforeseen problem with setting up my heat bed this way? Anyone?

So the next question/problem is:
With the new glass bed, as well as a new thicker 5mm Y carriage, the Y Carriage/heat bed/print surface mass is wobbling and prints got slightly worse at higher print speeds. Ripples on areas after path direction changes, especially in the Y to X axis as the Heat Bed and glass plate wobble front to back. A tighter Y belt will be done. I was thinking about isolating the issue to just the belt which would at least solve some of the problem, and the springs are an obvious source of lateral instability so I was going to eliminate that first. Since lead screws can solve the belt backlash issues completely, but would be sadly ineffective with this springy wobbly mess on top still.

So has anyone made a vertical brace for the edges of a heat bed that allows it to travel vertically but not horizontally in relation to the Y carriage? I am printing tests of that, but are there any known issues there? Like 'oh man everyone did that 3 years ago but it causes X horrible problem!' type info is sorta what I am after here, as well as any and all good advice.

I am preliminarily thinking about bracing on the corners I have conected as a pivot axis (front right back left). Bracing the front, sides, and back of the heat bed with metal plates that allow the heatbed to slide vertical if the extruder head crashes into the bed, and allowing the rolling of the entire build plane across that diagonal axis for leveling, I hope to eliminate the wobbling table as much as possible while retaining the springs function of allowing the z home to be on a simple switch and bottom out slightly without damaging the extruder.

Hope that all makes some sense, I am just learning the dialogue and terminology of 3d printing.

Thanks]]> Milton General Mon, 04 Jul 2016 05:05:21 -0400 https://reprap.org/forum/read.php?1,669872,673879#msg-673879 Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one https://reprap.org/forum/read.php?1,669872,673879#msg-673879 My latest design is using 10mm with SF-1 or sintered bronze bushings (will probably go for SF-1 for now) some 60-70mm apart for good stability, so the bearings' weight is saved here (they're incredibly heavy compared to the LM8UUs).

The hotend to move is to make a Renishaw-probe arrangement where the hotend itself is the probe.

Edit: oh and i've seen a lot of movement in G+ towards silicone instead of the springs... thought of it as a good idea.]]> realthor General Mon, 13 Jun 2016 03:59:24 -0400 https://reprap.org/forum/read.php?1,669872,673803#msg-673803 Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one https://reprap.org/forum/read.php?1,669872,673803#msg-673803 MechaBits General Sun, 12 Jun 2016 18:33:05 -0400 https://reprap.org/forum/read.php?1,669872,673795#msg-673795 Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one https://reprap.org/forum/read.php?1,669872,673795#msg-673795 DjDemonD General Sun, 12 Jun 2016 17:56:53 -0400 https://reprap.org/forum/read.php?1,669872,673791#msg-673791 Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one https://reprap.org/forum/read.php?1,669872,673791#msg-673791 MechaBits General Sun, 12 Jun 2016 17:49:10 -0400 https://reprap.org/forum/read.php?1,669872,673781#msg-673781 Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one https://reprap.org/forum/read.php?1,669872,673781#msg-673781 [attachment 79686 2016-06-1222.13.36.jpg]

I ordered a 300x200mm aluminium bed from Leap3D in the states and it came with what appears to be just thick silicone tubing instead of springs. Very pleased with it, gets rid of all that lateral movement and wobbliness of springs and allows for a reasonable range of adjustment, and its simple and cheap. Won't really give very much if you have a head crash but then springs wont help that much either they'll just compress until they are compressed then if something is going to snap/bend it will do so anyway.]]> DjDemonD General Sun, 12 Jun 2016 17:18:50 -0400 https://reprap.org/forum/read.php?1,669872,673778#msg-673778 Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one https://reprap.org/forum/read.php?1,669872,673778#msg-673778
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DjDemonD
They might bend if you are fortunate enough to have your head crash in the centre of their travel, but near the supports at the ends of the travel - probably not a great deal at all.

Sorry to be a little puzzled at this topic but head crashes are occasional unfortunate events, which generally don't cause much harm as they usually only happen when calibrating/modifying the machine and something is not set right, often during these events you are watching closely and can pull the plug before anything snaps. Electronics failures happen too, but with NC sensors, a failed sensor (or broken wire/connector) results in no z movement, and in my experience this is the most likely and common electronic failure leading to a head crash. Whilst a system that can prevent any head crashes would be nice if it were simple and reliable aren't we trying to force a solution where there is little or no problem to begin with?

I have a belt driven z axis so if I get my motor torque just right, then the z motor skips on a head crash instead of the heatbreak (or any other part of the print head) breaking/bending. Less easy to do with leadscrews/ballscrews I agree due to their gearing but still possible.

Yeah, this topic started as something else and it drifted off. Now, while I was working on some design issue, I remembered about this discussion and posted. I am not too concerned about a head crash into the bed...
I knwo that the nozzle must be in the middle to have the maximum amount of flex and because I imagine that such a crash could only happen during homing, positioning the head in the middle of the XRods is just a software configuration, so easily achievable.

This discussion might be quite trivial but getting rid of the flimsy spring-loaded bolts that secure most beds nowadays is quite an achievement if enough failsafes can be managed to make a head crash non-damaging.]]> realthor General Sun, 12 Jun 2016 17:08:32 -0400 https://reprap.org/forum/read.php?1,669872,673772#msg-673772 Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one https://reprap.org/forum/read.php?1,669872,673772#msg-673772
Sorry to be a little puzzled at this topic but head crashes are occasional unfortunate events, which generally don't cause much harm as they usually only happen when calibrating/modifying the machine and something is not set right, often during these events you are watching closely and can pull the plug before anything snaps. Electronics failures happen too, but with NC sensors, a failed sensor (or broken wire/connector) results in no z movement, and in my experience this is the most likely and common electronic failure leading to a head crash. Whilst a system that can prevent any head crashes would be nice if it were simple and reliable aren't we trying to force a solution where there is little or no problem to begin with?

I have a belt driven z axis so if I get my motor torque just right, then the z motor skips on a head crash instead of the heatbreak (or any other part of the print head) breaking/bending. Less easy to do with leadscrews/ballscrews I agree due to their gearing but still possible.]]> DjDemonD General Sun, 12 Jun 2016 17:01:05 -0400 https://reprap.org/forum/read.php?1,669872,673769#msg-673769 Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one https://reprap.org/forum/read.php?1,669872,673769#msg-673769
Quote
MechaBits
Lol...Just put X arm on a hinge...then you might only need to level bed in one direction.

I don't get it... what X arm?
And really, I don't know if 10mm rods will flex before heatbrake gives away ...]]> realthor General Sun, 12 Jun 2016 16:50:31 -0400 https://reprap.org/forum/read.php?1,669872,673767#msg-673767 Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one https://reprap.org/forum/read.php?1,669872,673767#msg-673767 MechaBits General Sun, 12 Jun 2016 16:46:00 -0400 https://reprap.org/forum/read.php?1,669872,673725#msg-673725 Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one https://reprap.org/forum/read.php?1,669872,673725#msg-673725
Quote
the_digital_dentist
The problem with schemes that use a switch to detect a head crash is the same that problem that causes the z=0 switch to be ignored. You can't rely on malfunctioning electronics to behave the way you want.

The problem with mechanical methods, such as allowing the head to tilt or have a spring(s) to allow the extruder/hot-end or bed to move out of the way is the limited range of motion they can provide.

The only guaranteed way to prevent hot-end damage is to physically stop the bed and extruder nozzle from moving close enough for the two to touch. That requires installing finely adjustable, sturdy mechanical stops for the Z axis. If you physically block contact, you're counting on the motor to slip and not tear any teeth off the drive belt if the axis is belt driven.

That prevents damage due to the nozzle crashing into the bed plate, but doesn't help with the nozzle crashing into a print or clip used to hold a glass plate on the bed.

I don't think there is a mechanism that can protect from all possible crashes without severely compromising print quality.

Or install the nozzle 1mm below the X Rods so that if the bed hits the nozzle the flex of the rods will allow for that 1-ish mm and the bed will remain pushing against the rods. Will 10mm rods flex for 1mm if the bed forces against the nozzle before the heatbreak gives away and bends?]]> realthor General Sun, 12 Jun 2016 14:26:14 -0400 https://reprap.org/forum/read.php?1,669872,673537#msg-673537 Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one https://reprap.org/forum/read.php?1,669872,673537#msg-673537 Here is a very simple way to constrain laterally (on X) the build plate:

[attachment 79650 screenshot.597.png]

Due to the cork the heat should not creep into the ALU angle so an ABS simple part and an M3 allen bolt should do the constraining. I do believe that some sort of insulating pad should be there at the tip of the bolt so the heat doesn't creep back through the allen bolt into the plastic.]]> realthor General Sat, 11 Jun 2016 17:31:30 -0400 https://reprap.org/forum/read.php?1,669872,673519#msg-673519 Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one https://reprap.org/forum/read.php?1,669872,673519#msg-673519
[attachment 79640 sensorview2a.jpg]

Piezo disk not marked but under the pressure pad.

Mike]]> leadinglights General Sat, 11 Jun 2016 16:35:06 -0400 https://reprap.org/forum/read.php?1,669872,673503#msg-673503 Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one https://reprap.org/forum/read.php?1,669872,673503#msg-673503
My setup is quite simple, 3 rods and 3 bearing-blocks that also act as square tube clamps and level adjusters. The issue I faced with the previous design is that I didn't have any way to constrain XY movement of the bed and now I have added the ALU angle to constrain on Y and I could use the adjusting bolts on the 2-rods side to constrain the bed movement on X. I can't do much for X on the single-rod side so I must somehow take advantage of the two adjustment bolts' heads on the other side.

I would also like to know if the cork the bed rests on is ok from the leveling pov.]]> realthor General Sat, 11 Jun 2016 15:53:36 -0400 https://reprap.org/forum/read.php?1,669872,673457#msg-673457 Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one https://reprap.org/forum/read.php?1,669872,673457#msg-673457
[attachment 79620 20160527_191956.jpg]

This design started as a quick kludge to overcome the print bed taking up random positions in X and Y but is now fitted to all of my printers. Although the geometry is not great, it is able to accept any point of the hexagon being depressed by 15mm without sticking.

Mike]]> leadinglights General Sat, 11 Jun 2016 13:02:00 -0400 https://reprap.org/forum/read.php?1,669872,673340#msg-673340 Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one https://reprap.org/forum/read.php?1,669872,673340#msg-673340
[attachment 79591 SCOUTcorexy_ZStage_Moving_v2ALU-Angle-reinforced.png]

I also need to find an angle that is shorter that 12mm on one side and 20mm on the other side, so an asymmetrical ALU angle.]]> realthor General Sat, 11 Jun 2016 05:49:24 -0400 https://reprap.org/forum/read.php?1,669872,672156#msg-672156 Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one https://reprap.org/forum/read.php?1,669872,672156#msg-672156
Quote
the_digital_dentist
Quote
realthor
Yes, I understand and agree. I was wary about the silicone springiness but couldn't think of something else especially that silicone can be high temp and is also somewhat non-slippery. In a previous iteration I did have constraints at the corners but those are not possible anymore now after I have changed several things :) ... I am still scratching my head for this as I am not completely happy with the bed support solution I have.

What if you glued disc magnets to the top of the silicone pads and to the underside of the bed plate? The smooth magnetic discs would slip against each other when turning the leveling screws, preventing the silicone "unwinding" problem, and would keep the bed plate in place better than relying solely on gravity to do so.

The only problem with magnets is a heated bed. They loose magnetism pretty quickly with temp. I am thinking more and more that I need either of:
a) a milled recess in the plate that would receive a round bolt-head (allen type) - best would be a half sphere recess to receive a dome-head bolt-
or
b) a bolt that i can file the end to a round and insert a drilled round piece that I would cover with silicone or even some double sided adhesive pad and which will stay fixed while the thumbwheel will rotate the bolt underneath it.

The more I think of it the more feasible the b) option looks .... filing the threads off the end of a bolt is quite easy (put bolt in drill by its head and press the file against it while it is rotating until there are no more threads). Then take a thick washer or some sort of drilled disk or even a printed part that is dipped in silicone on its head and insert it on the smooth end of the bolt. And voila, non-slip and no rotation.

Edit: the screws used in table clamps that have the swiveling, free-rotating cones would be ideal: fill the cone with silicone and you're set.]]> realthor General Tue, 07 Jun 2016 18:53:39 -0400 https://reprap.org/forum/read.php?1,669872,672045#msg-672045 Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one https://reprap.org/forum/read.php?1,669872,672045#msg-672045
Yes I know it's still electronic and can fail but it would add significant redundancy for little cost and be far more reliable than a software solution. Physical limits sound nice but they are going to be difficult to set and prone to drifting off.]]> DjDemonD General Tue, 07 Jun 2016 13:41:50 -0400 https://reprap.org/forum/read.php?1,669872,672038#msg-672038 Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one https://reprap.org/forum/read.php?1,669872,672038#msg-672038
Quote
realthor
Yes, I understand and agree. I was wary about the silicone springiness but couldn't think of something else especially that silicone can be high temp and is also somewhat non-slippery. In a previous iteration I did have constraints at the corners but those are not possible anymore now after I have changed several things :) ... I am still scratching my head for this as I am not completely happy with the bed support solution I have.

What if you glued disc magnets to the top of the silicone pads and to the underside of the bed plate? The smooth magnetic discs would slip against each other when turning the leveling screws, preventing the silicone "unwinding" problem, and would keep the bed plate in place better than relying solely on gravity to do so.]]> the_digital_dentist General Tue, 07 Jun 2016 13:21:16 -0400 https://reprap.org/forum/read.php?1,669872,672037#msg-672037 Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one https://reprap.org/forum/read.php?1,669872,672037#msg-672037
The problem with mechanical methods, such as allowing the head to tilt or have a spring(s) to allow the extruder/hot-end or bed to move out of the way is the limited range of motion they can provide.

The only guaranteed way to prevent hot-end damage is to physically stop the bed and extruder nozzle from moving close enough for the two to touch. That requires installing finely adjustable, sturdy mechanical stops for the Z axis. If you physically block contact, you're counting on the motor to slip and not tear any teeth off the drive belt if the axis is belt driven.

That prevents damage due to the nozzle crashing into the bed plate, but doesn't help with the nozzle crashing into a print or clip used to hold a glass plate on the bed.

I don't think there is a mechanism that can protect from all possible crashes without severely compromising print quality.]]> the_digital_dentist General Tue, 07 Jun 2016 13:16:22 -0400 https://reprap.org/forum/read.php?1,669872,672011#msg-672011 Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one https://reprap.org/forum/read.php?1,669872,672011#msg-672011 DjDemonD General Tue, 07 Jun 2016 11:50:28 -0400 https://reprap.org/forum/read.php?1,669872,670395#msg-670395 Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one https://reprap.org/forum/read.php?1,669872,670395#msg-670395
So it's the general consensus that the springs in the bed leveling bolts should be strong enough to keep the bed in position but will be too strong for an eventual crash for absorbing the shock?
If that's the case why not ditch them completely like d_d did and only have some bolts with a locknut instead of the spring, with a built-in wheel for easier turning.]]> realthor General Thu, 02 Jun 2016 15:39:39 -0400 https://reprap.org/forum/read.php?1,669872,670349#msg-670349 Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one https://reprap.org/forum/read.php?1,669872,670349#msg-670349
Quote
realthor
I am seriously thinking of implementing some sort of renishaw_probe-style hotend, so that any head-crash would just cut the power to the motors or something like that...

@dc42: ... can you post a pic or something (link?) about that? I am very curious...

There are some pictures on the assembly instructions page here [reprappro.com]. The X-carriage and head assembly rotates around the smooth rod, and the runner on the back of the X arm stops it going too far. The weakness in the original design is the acrylic X-arm which tends to twist slightly, but many Ormerod owners have replaced it with an aluminium arm.

Delta printers sometimes use use the nozzle itself as the Z probe, with either FSRs under the bed supports or an FSR or microswitch in the head assembly to detect contact with the bed. The same device could be used to cut power to the motors.]]> dc42 General Thu, 02 Jun 2016 13:10:57 -0400 https://reprap.org/forum/read.php?1,669872,670300#msg-670300 Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one https://reprap.org/forum/read.php?1,669872,670300#msg-670300
@dc42: ... can you post a pic or something (link?) about that? I am very curious...]]> realthor General Thu, 02 Jun 2016 09:45:35 -0400