Repeating "thick" Layer Lines mainly on underside of prints

Form 2, Brand New Tough 2000 Resin, LT Tank currently at @74%, 100 micron layer, Optics cleaned 5 Weeks ago, All Prints are otherwise perfect but are all suffering from this defect… Most pronounced on the side facing the build Plate. All parts angled at least 20 degrees in both X and Y Axis. I cleaned and re-lubed (super lube) Z Axis Leadscrew with no change in results. Defect distances are somewhat random with these measured distances, 23.9mm, 9.7mm, 7.6mm, 5.4mm Never had this problem before. Firmware is 3.12.3 Is this a Hardware problem or a Firmware issue. I have not updated Firmware as others have recently reported problems with recent Firmware versions. Please look at pictures and advise.

When you install and then close the clamp on your build plate, does the assembly move at all?

Hi Randy, Just checked and it is rock solid. No movement at all. I tried to twist it, lift it, pressed down on it, push it forward, back, left and right. There is no movement or looseness in the Build plate nor the Z Axis that I can determine. Lead Screw Nut and anti Backlash spring all appear to be in good working order. Z Axis is well lubricated and Clean. No odd noises nor vibrations during Z Axis movements. Making parts for Johnny Five Robot. Here is a link to our site.

OK, then, you have to go back to the Z-Axis. You say “well lubricated”. How well? Mechanical positioning systems that need to move in very small steps can be negatively affected by too much grease. The problem is that the grease builds up in the direction of travel, kind of like a snow plow effect. That grease offers some resistance to subsequent motion. It’s slippery, but it’s also viscous. If there’s a build up of material, the motion system has to push that build up aside before it can move correctly. It’s a “hydraulic” effect. Too much grease on the lead screw can be as much of a problem as too little.

Hello @Randy_Cohen,
I have included this picture of the Leadscrew. I own a CNC machine along with a Lathe and Mill so I have some experience with Leadscrew lubrication and maintenance and replacement already. I honestly don’t think its the Z-Axis as one of the lines abruptly stops as seen in the picture (Red Arrow) and is completely normal in the Green circled area.


There are visible lines pretty much throughout. But there’s a major line that occurs at what seems like a fairly regular interval. I don’t remember ever seeing something like this on my Form2 (which has been retired for a Form3). I don’t think that the resin tank moving will matter. But if you’re sure the lead screw isn’t overly greased (I also own a CNC mill), the only place left to look is the resin tank. The lines occur because of mis-registration. The positioning system isn’t getting back to the same place after each peel. The peel puts a lot of force on the build plate which is why I suggested you look there, first. It also puts a load on the tank. Maybe the tank is moving after the layer printing has started. Otherwise it shouldn’t matter where the tank is relative to where it was on the last layer. This doesn’t look like a laser positioning issue…

@Randy_Cohen, I’m going to clean the main mirror and Window just in case it’s some strange Optical issue and reprint those same exact Form files. I’m not going to clean the Galvos again just yet as those are of course a pain to get at and clean and they generally will dislodge any dust just due to the fact that they move around. I will let you and everyone else that may be following this thread know if simply cleaning those optics resolves the issue. I have personally found that 99% of poor print quality issues are fixed once the Optics are properly cleaned. Fingers crossed!

This isn’t a laser power or beam dispersion issue that cleaning mirrors and the window will fix. It’s a mechanical displacement of either the build plate relative to the machine’s base, or some issue with the positioning repeatability of one or both of the galvos. Though the periodicity of the large layer lines is impossible to reconcile with my expectations of what’d happen with a “sloppy” galvo. If there is a galvo problem it should be the same on every layer i.e., totally random.

@Randy_Cohen, Yea… I agree that this one is a bit of a Head Scratcher. I did Clean the Mirror and Optical Window. Noticed some dust (Of Course) on the Mirror along with a bit of discolored “Hazing”. Was not to bad but not real clean ethier. Cleaned the Window…Mainly small dust particles, again nothing to bad. Nothing jumped out at me as being a source of the problem I’m having. Printing out the same exact Form file now to see if anything changes for the better or worse. Oh, and I did check the Tank for proper full engagement and that it was locked in prior to removing it for Optics cleaning. I could not see or feel any movement nor anything else wrong with the Tank being firmly attached to Machine.

@Randy_Cohen, Well I reprinted the part after cleaning the optics but no improvement as we both sort of expected. I did however find some limited information on this Formlabs support page.


Visual symptoms
A void that passes through the entire print, including the raft (if one is used). The void may take the form of a small hole in one portion of the part or a linear slit that extends across the part.

Could this have been a new “Bad Tank” causing what they seem to refer to as “a linear slit that extends across the part.”?
While the defect’s are technically not “slit’s”, they do extend across the part. This Tank is now as 78% and has had 2.5 Liters of Resin used in it with all parts being at 100 Microns and no print “Failures” that would have fouled the Tank surface due to Resin particles floating around. I’m going to swap out the Tank for a new one tomorrow and see it that was not the problem but this ongoing trouble shooting is getting expensive from a Resin usage standpoint. I always also add some Resin to a new Tank prior to powering the Printer on so it does not do a “dry sweep” of the Wiper Arm across the Tanks surface.

From March 11th till April 8th I have done 32 prints on this Tank and I do notice that the First parts I printed have the defect but not to the extent in depth or amount that I am seeing now. So this problem slowly got worse over time and sort of snuck up on me as far as noticing the Line defects.

@DKirch, I have seen you helped some others out recently. Have any suggestions on my problem in this thread or can bring it to the attention of someone else at Formlabs that may be able to help?
Thank you!

Your problem doesn’t look like “voids” to me. It looks like simple layer-to-layer displacement. You get the same surface features from a poorly tuned FDM printer. The smoothness of the face of the print is a function of how well each layer is aligned to the last. The apparent periodicity of the defects makes me want to blame the mechanics still. Maybe that’s related to when the mixer does a sweep or something.

Are you always printing the part in the same orientation and in the same position on the build platform? Can you push it to one of the corners maybe?

I can think of one way it might be the tank (indirectly). None of your pictures show the supports. Is the support density high? Try setting that higher still and see if the problem goes away or at least is mitigated some. If the supports aren’t printing rigid enough, because the tank is a little worn out where they supports are printing, the print is going to maybe wiggle around a little each time it’s brought back in contact with the tank bottom. Or maybe the peel force is higher than it should be, so the model’s position is “tweaked” a little each time there’s a peel. The supports aren’t that rigid…

I remember inspecting the bottom retired tanks of my Form2 and seeing physical dimples in the surface, pits, from where I’d printed supports in the same place too many times… The supports are murder on the tank.

Formlabs is going to have to run their test print. I can’t point you to it, but I’ve seen them request it time and again. You could maybe get ahead of them on that and find a thread with the pertinent information and print it in advance…

@Randy_Cohen, Yep, I have that Formlabs test file already, printing it out now prior to Tank change. I’ll let you know how it goes. I use all of the Default settings for supports but I do decrease the touch point size down to 0.40mm. As far as part orientation, it really varies depending on the part geometry and the size of the part I’m printing. I try to place the part in such a way as to decrease the overall amount of surface area being printed to a minimal cross section to reduce peeling force. Here is a YouTube video for you and anyone else that shows in detail the Layer line issue on many different parts and support structures. It is 6 1/2 Minutes long Again thank you for your help @Randy_Cohen!!!

Test print done. due to the very limited Z Axis height of the Formlabs test print file it gives limited space for reproducing my problem but the Largest of the parts shows the issue clearly remains. The upper one is from a previous old test run after Optics cleaning in open mode (No Wiper nor Heater enabled) using Appiedlabwork Gray Resin and a standard Tank. Todays test print does show the same defect as all of my other prints. A Formlabs higher Z Axis test print would likely be much better for diagnosing my particular printing issue. See picture.

@Randy_Cohen @DKirch, Found the likely cause! Re-ran the Formlabs Test print and so far the prints look good. 100% confirming by reprinting my previously printed Form file parts as they have a much higher Z Axis profile and I can directly compare them to my previously bad prints for reference purposes. Looks like it was a defective LT Resin Tank directly from Formlabs. See Video.

Thanks for sharing this Jerry. Nice work. I was also scratching my head but could not make a useful contribution.

Will now add a “ripple” inspection to my process procedures, especially around the edges of the tank.

All the best

@Randy_Cohen, @DKirch Defective Tank confirmed. Same exact Form file, Settings and Resin. New Tank was the only change. Left one is from Defective Tank, Right is from new Tank. The single line on the Right one is from a large spec of dust on my Mirror…need to blow that off…LOL

I had the same issue, I believe its the resin sensor during printing. When the part is out of the tank and the sensor is taking some time to check the amount of resin the longer the time the more lines you’ll get.

Ive resorted to open mode in castable v2 setting now and the lines went away.