Adjusting resin tank level to fix thin bases and other issues. I "break" my Form1 and fix it in video to demonstrate

Hi All,

Jory has suggested that adjusting the resin tank level yourself will void your warranty - I take strong exception to this, because it’s very easy to do.

The Form1 solution for “levelling” is utterly elegant - in that it’s simple and very forgiving. It uses springs, and so you only need to be “good enough” in adjusting them, there’s no need for micron precision and obsessive spirit level checking etc…

Also adjusting them is completely reversible and can do no lasting harm to your Form1. See my rant on the subject in this thread I really hope Formlabs will change their tune.

In the following video, I explain how easy it is to adjust the resin tank level, if your part bases are coming out too thin when the resin tank springs are too high.

Or -  perhaps your bases are coming out close to spec thickness, but you’re getting strange extraneous goopy flakes on your prints, or maybe your parts won’t adhere to the build platform - in which case it may be that you need to increase the height of the resin tank springs.

It’s my longest video I’m afraid at 14 and a half minutes, but I wanted to thoroughly refute Formlabs assertion that only they should be adjusting resin tank springs, and show just how easy it is, by first “breaking” my form1 and showing you the prints that come out, and then fixing it.

So the first half of the video explains how to adjust the spring tension nuts - and the second half shows a couple of bad prints after I “maladjust” the springs, followed by a good print after correcting the springs.

Alternatively - if you don’t have the patience to watch a few minutes of video, here’s how you do it.

1) Find a small magnet

2) Remove the upper cover+top half of Form1 case (they come off as one unit) - by unscrewing the top 4 hex screws from each side of the Form1 (careful with the black ones, it’s very easy to round out the heads - so only do them back up finger tight), two hex screws under the cover hinge, and also the front and back cover panels. To remove the front panel you need to undo two more hex screws under the base of the Form1 at the front.

3) Plug the Form1 back in and use the magnet on the top right of the front panel to fool the Form1 into thinking it’s cover is on and shut - and load and confirm a print.

4) Wait until the build platform has fully descended to Z=0 - and the resin tank has come back up (tic-tic-tic) and the laser has just started. Then remove the magnet to pause your Form1

5) Now your Form1 build platform and resin tank are mated together in the starting position, and so you can adjust the resin tank spring nuts to match the resting height of the resin tank, to the starting position of the build platform.

There are machine screws through the centre of each of the springs at the four corners of the resin tank frame - you adjust the height of these springs, and hence the height of the resin tank at rest, by tightening or loosening the nuts.

Tightening the nuts, reduces the height of the springs, and the rest height of the resin tank, loosening them of course does the opposite.

If the resin tank springs are too high, then there will be clear screw thread visible between the nut and the black coated steel of the resin tank frame, and what you want to do is tighten the nut** until it’s just about touching the frame, **for example if you could almost slide a piece of paper between the nut and the frame, then that’s spot on.

Conversely - if your parts are coming out with thick bases but goopy flakes attached, or if parts are not attaching to the build platform at all, and one or more of the nuts is obviously tight against the resin tank frame, then back it off until you can see screw thread between the nut and the frame, and then tighten it back up again as above.

That’s it, easy as pie, and zero risk - you can’t hurt* your Form1 doing this.


*PS - when I say you can’t hurt your Form1 doing this, that’s with the caveat of the black hex screws. I did round out the head sockets and had to dremel slots in them to use them. So be careful!!

I really appreciate you taking the time to publish this, but from what I understand, the thing with the magnet is potentially really dangerous (to your eyes, not the machine).

I can see how Formlabs could never endorse this procedure for end-users, when part of it consists of circumventing an important (laser) safety feature.

Hi, Kelvin,

My machine have the same problems as yours but worse, None of the test object attached to the builder platform. I reported to them on Jan 30, sent me the test file on Feb 6, reported on Feb 7 and waited till now. Seems to me reply a user problem once a week is their tradition. I’ve been waiting for 6 days now. I think I’ll tried your method a few days later. see if I can fix my machine.

p.s. I hate to do this. voicing out in the forum seems to get their attention than sending emails. That’s bad.


This is a pretty detailed write-up – but I want to warn everyone here, that in no uncertain terms should the resin tank carriage nuts be adjusted manually. In short, you CAN hurt your Form 1 doing this.

While the issue that you’re trying to solve – incorrect alignment between the build platform and the PDMS – can certainly be modified by adjusting the tank level, the nuts are doing much more than maintaining that distance.

They also control the alignment of the X-Y plane with the z-axis, which is something that we use specialized hardware to do on a per-machine basis in the factory. That’s why this is something that we don’t want to advise people to attempt independently. Your efforts here have been awesome – and honestly, as engineers and hackers ourselves, we appreciate them – but we don’t want to risk people permanently throwing off their alignment, if that’s something that’s important to them.

We are always working to improve our in-house calibration, so hopefully some of the issues that you’ve encountered will be a thing of the past.  We’ve been on the frontier at taking a look at the machine – and that definitely raises some important questions for us about the nature of our support and warranty, but we’ll make sure to work with you to get your machine working as it should.

Additionally, we recently released a diagnostic flag in PreFrom, which introduces a software tool to change the Z-axis offset of your build platform and resin tank. This accomplishes the same goal as re-adjusting the nuts, but without throwing the calibration off.

To access diagnostic mode, PreForm needs to be started with a -diagnostic flag from the command line. With the printer connected, this will expose some additional settings – in particular, the z-offset mode. This allows you to permanently lift (or lower) your build platform slightly. To create prints with a thicker base (if your machine is having adherence issues), raise the platform slightly to compensate.

Chris – I’m sorry you haven’t gotten a response to your ticket. You will shortly.


Regarding the resin tank carriage nuts being responsible for alignment of the x-y plane with the z-axis - agreed, that makes sense. However, by suggesting that aligning the carriage to the build platform at Z=0 can take it out of alignment with the Z-axis, you are also suggesting that build platforms themselves are not in alignment with the Z-Axis - this strikes me as problematic.

Certainly using the build-platform as a guide for levelling has proven to be more effective for me in adjusting ObtainableLamb than as it was supplied from your Factory Testing floor - and that was January.

I’ve also just heard this morning from another Form1 owner that the rear two adjustment nuts on his recent replacement machine had a lot of thread visible; “3-4mm so the prints were pretty spectacular failures” - I won’t name him to protect his warranty. It seems extremely unlikely to me that his build platform could be that far out of alignment with the Z-axis - which really makes me question your “specialised hardware”.

Moreover - it seems to me that although the nuts are nylon lock nuts, they are still just nylon lock nuts. There’s no locktite applied or anything else to keep them in position. And, they are subject to serious repetitive strain from builds with larger surface areas that have suction-separation “thunks” - I would expect a certain amount of nut drift (loosening) over the 10s or even 100s of 1000’s of layers involved in printing several litres worth of such parts, not only that, but asymmetrical drift, with the nuts furthest from the peel axis drifting more. So presumably with time,  they naturally need adjusting on an active printer making larger parts - eg more than once a year …

Why aren’t the nuts more secure by the way?

It’s unfortunate that Formlabs haven’t spoken to this level of detail before, or previously published the build-platform adjustment function in pre-form (although thanks to Rocus Halbasch for his earlier mention) otherwise I would have run tests on my factory tested replacement machine - with it’s thin part bases and other problems.

So if my PDMS  X-Y plane is now out of alignment with the Z-axis, but I still get complete prints, then I could expect variations in part height from one side of the build area to the other. I’ll print some tall diagnostic parts at the four corners in various layer thickness’s and report back in a few days.


Thinking about this some more - I’m struggling to see what the real impact is if the x-y plane is not perfectly aligned with the z-axis, and is instead approximately lined up with the build-platform surface.

I’ll carry on printing my corner part height test pieces at 0.1, 0.05, and 0.025mm - but I can only think that once the part base is printed and there is no compression on any part of a print layer from the springs, that layer height will be consistent across the build area, and hence part height consistency is not going to be affected.

So I’m not sure what the practical impact is - I guess there could be some very slight part distortion somehow? but I can only think it will pale into insignificance next to the distortion we already have from the galvo tolerances, as in it’ll be too small to easily measure with verniers.

I can’t quite play it out in my head, I never was as good as I wanted at visualising in 3D; my old computer graphics professor had a favourite mental exercise he gave to every class. Take a cube on a flat surface - tilt it on one corner so that it’s opposite corner is directly above it perpendicular to the surface. Then push the cube down through the surface - what are the different intersection silhouettes of the surface with the cube as it travels sinks all the way through the surface? I never managed to visualise the whole thing properly.

I’m sorely tempted to just simulate a layered object build in Solidworks with a perfectly perpendicular PDMS layer, and a slightly skewed one, make an animation - and compare the resulting part dimensions.

I couldn’t sleep trying to visualise what happens during a build with the resin tank not perfectly perpendicular to the Z-axis - it seemed such a simple problem. Then it hit me, prints will be on a lean, or slanted, by the angular difference from perpendicular that the resin tank base is from the Z-axis. Layer height will be the same across the build area (and this is borne out by my first test prints - 50mm verticals test pieces printed at at 0.1mm layer height come out consistently 50.55/50.6mm  where-ever they’re printed on the platform) - but a vertical square will be printed as a canted parallelogram - that is angled away from square - by the same angle that the resin tank floor is to the Z-axis.

So - I’m printing some vertical square windows now - which will be easy to test for right angles - just by tracing their outlines on paper lined up against a rail, turning them 90 degs against the rail and tracing their outline again - the mismatch will show how slanted they are.

My feeling is that they won’t be out by much - possibly less than one degree - and that this won’t be any worse (and quite possibly better) than printers out of the box …


You’re a brave tinkerer what can I say. Don’t you think though that no matter what, the adjustment for accuracy should be made on the software/firmware level? Because the further away you get from the center, the more skewed some objects become in X, Y and Z directions. There has to be a software algorithm in place to compensate for this.

I think once Formlabs releases some kinda calibration addon, it will be much easier (and safer) to make these adjustments without the need to open the machine up and adjust the screws.

MD - this thread is not about accuracy, this is about failed prints, and parts with bases that are too thin because the resin tank is not levelled correctly.

For many the Z-axis adjustment in software explained by Sam above will do the job - athough that is the first mention of this function I’ve seen from Formlabs. I doubt it will do the job for all, given what I heard from another owner about his recent replacement machine “my new printer had the two rear nuts backed off 3-4mm so the prints were pretty spectacular failures.” - that’s clear thread visible between the nut and resin tank carriage when the build platform is at Z=0 for clarity, it seems very unlikely that any software tweak could have helped in that case.

But it’s good to know - and I think it would great if Formlabs would document the -diagnostic function of Preform in the troubleshooting section, although Rocus Halbasch already mentioned it a couple of weeks ago and I put it on the wiki then.

Levelling adjustments via software is limited to adjusting the Zero position of the build platform - and if the resin tank is not close to level (as in the example I mentioned above)- that will not help.

Moreover - as I also mentioned in a previous post already the nuts are only nylon lock nuts, with no loctite or anything else holding them in position. For you jewellers making rings, and pendants, it’s probably fine, you won’t ever be subjecting your resin tank to peels that “thunk” as they separate - but for those of us making larger parts, it seems likely that the nuts will drift over time, and drift asymmetrically, and will inevitably need adjustment.

Sam has also suggested that levelling the resin tank as per my instructions above can take the resin tank out of perpendicular alignment to the z-axis as calibrated by their specialist hardware - well I’m remain to be convinced their specialist hardware is really doing a good job, or that levelling the resin tank against the build platform is going to put you in a worse position.

I’m running some test prints now to show how close (or far) from perfectly perpendicular to the Z-axis my PDMS x-y plane is, and then I’ll start a new thread - asking if anyone would like to see how well aligned to the z-axis their resin tanks are.


As many of us have multiple resin vats and no 2 vats are identical, how is one expected to calibrate a not-originally-included and calibrated vat?  By 'calibration" I mean the platform and PDMS surfaces are parallel.

I agree that only software is not going to solve the leveling problems. I am in that business for many years now and every machine has to be mechanical calibrated also. So as far the form1 is likely impossible to adjust the focus, the leveling and the distortion with a firmware update. Don’t forget that the left bolts are fixed in position so you can adjust only the right side by leveling up or down via software, that is for x axis. What about z and y axis? As you can understand if you want a perfect level and calibrated machine you must adjust all axis in the right position and not only one! So the conclusion is that if you are lucky enough and the y axis is not off position, the silicon tray is parallel with the x,y axis and the built platform is parallel with the silicon tray, then the software maybe will do the job but not for sure…

After a little thought, bringing the PDMS surface into parallel with the platform is not critical as the 2mm(or whatever the user specifies in Preform) base beneath the supports will negate any resin vat irregularities.  I’ll go into more detail on the Unofficial Wiki soon.

Also, I’ve come up with a calibration process for paralellizing the platform to peel tray that is probably on par with what Formlabs is doing.  The process will improve upon what Kevin Holmes has devised.  Stay tuned!

I’ve been talking back and forth with Formlabs on this very topic for quite a while now. I have had two machine replacements trying to get my platform parallel to my bed. I want this so prints printed directly to the platform with no supports come out correctly. However they told me:

the platform and tank are intended to be positioned at a slight angle to each other, and that angle is accommodated in the machine’s calibration processes.

I tried to get an answer to what “accommodated” means explaining that the angle to which it is not parallel translates directly to my prints, resulting in a variance in thickness and a lean. With a lot of back and forth and a lot of non-committal answers on their part I finally asked:

I’m just trying to figure out if my machine is behaving as designed or not. If it is I’ll figure out something. So could you please ask the engineering people if it is considered correct behaviour that when the Eiffel Tower is printed directly to the bed at 100um it prints leaning to one side by 0.4 degrees and with the pads on the bottom varying in thickness by 0.85mm? If they say that is expected behaviour then my printer is fine. If not then something is wrong with it.

And they answered:

From everything I’ve heard from our engineers, yes, your machine is performing as it’s designed to.

I will elaborate more later.