Tank level inaccuracy causing long wait times before print

Am I the only one that is absolutely irked by the fact that the the Form 3+ is unable to accurately estimate the remaining resin volume whatsoever, under almost all circumstances? And because of this, a huge amount of time is wasted before every print while the printer catches up and realizes that there’s actually no resin left aside from what’s in the build tray? Surely other people are running into this too?

Basically, the resin level sensor(s) don’t seem to be able to accurately tell how much resin a tank has left to within about a full liter, or half the total capacity of a new tank. My printers always say the resin tank is still half full when it is completely empty and only resin in the build tray remains. It’s done this since I had it new. The unit we have at work does the same thing. I asked Formlabs why they couldn’t do better at level estimation and got a super lame excuse so I’m hoping for something better. For ~$3k I expect better, and for me, this is near the top of all my complaints for the Form 3 in general.

The reason why this bugs me so much, aside from just being ridiculously inaccurate and unacceptable, is because when you start a print the first thing it will do is try to fill the build tray with more resin. It will keep trying to dispense resin despite the fact that the resin tank is completely empty. So then it just spins its wheels, waiting to dispense more resin that never comes. The last time I started a print it did this pointless fill cycle for ONE HOUR AND FORTY FIVE MINUTES before it finally prompted me with the warning about resin level where it asks if you want to process. So my 45 minute print job became a 2 hr 15 min job simply because the printer is too stupid to tell how much resin is actually left.

What is even the point of resin level monitoring if it’s so inaccurate that it’s unusable as a feature? At the very least, Formlabs could reduce the timeout interval or create some sort of bypass feature so you don’t have to wait while the printer tries to fill resin that’s just not there. In most cases there is enough resin left in the build tray to complete several more rounds of printing. The printer is inaccurate by 50% which means that it’s operating in this false state for nearly HALF your total prints! That’s a huge amount of time wasted at the beginning of every print.

Is anybody else peeved about this too? Are there workarounds other than just waiting for the printer to realize there’s no more resin and tacking on an hour or two of time to half your total prints?

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Hi @misterproject,

Thank you for getting in touch. For more context on this issue, please see my reply in this thread. I understand that this issue can be quite inconvenient and cause downtime due to extended filling. The best workaround I can suggest in the meantime would be to physically pick up or weigh the cartridges to judge their fill level prior to starting a print.

You’ve been “working on” this for 1, maybe 2 years now. So when do we get a fix!? I’m entire p$@%&@ off at Formlabs about this issue. When the resin tank is empty (yet still reports half full), it’s the TIME DELAY that I care about. Did you even read my entire post? The printer will try to fill a build tray using an empty tank, and it will do this for up to 1.75 hours in my case before the print will actually start. This is a huge time suck before every print and is unacceptable. You didn’t address most of the point in my post. Typical Formlabs response. It’s clear you people don’t care at all about resolution. Otherwise a fix would have been employed months ago. Hell, the post YOU linked is nearly 10 months old and still no fix like it promised!

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Hi @misterproject

First let me just start off by saying I understand your frustration, but please know that we want to help. I appreciate you providing the recommendation of lowering the threshold window and will certainly pass that along to our internal Product Feedback page.

You can also submit a request through PreForm by going to Help > Give Feedback. Although I can’t guarantee a change or a timeline to results, we always want to hear directly from our users about how we can improve our hardware, software, and overall user experience.

I understand that this is not a direct resolution to your problem, but some of the workflow tips that Jesse provided in the other thread will hopefully lead to some better user-experience with your printer. Please feel free to reach out to our Support Team for more individualized assistance and recommendations as needed.

The tank level floating sensor inside the tank gets stuck sometimes due to resin getting on the hinge points. It’s a good idea to move in multiple times before starting a print

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Thank you for your input, but unfortunately this is not related whatsoever to the issue I describe. The tank level sensors are not stuck. Even if they were, waiting for 1.75 hours for the system to finally tell you there is a problem is WAY to long. This is the issue at the root of my complaint. As long as there is resin in the build tray (resin tank empty or not–it shouldn’t matter), it should not take 1.75 hrs for the system to start the print.
I feel like I’m not describing this issue very well since everyone is getting hung up on the parts that are only tangentially relevant. I don’t know how else to describe it, but I don’t think I’m making my point. I’ll try one more time.

  1. The real core issue is that the printer is unable to determine the resin tank volume remaining. It is only accurate to 50%, and it says that the resin tank is about half full when the resin tank actually first becomes empty. This implies that either A) the printer erroneously thinks the resin tank is still half full, or B) that the printer thinks the remaining half of the resin that it says is in the resin tank is actually currently filled into the build tray. Regardless of whether it’s A or B, the printer is still very wrong with its estimation of remaining resin anywhere in the system. A sensor that is only 50% accurate is not doing it’s job correctly. After all, a coin flip is just as accurate regarding if there is resin left or not…

  2. Because of the root issue in #1 above, the printer does some dumb stuff that it shouldn’t and doesn’t need to which makes the print process take wayyyy longer than it should. As you know, before every print the printer will try to fill the build tray using resin from the tank. It fills until the level sensor in the build tray hits some level threshold. Again, a sticky level sensor is not part of the problem I’m describing and in my case they are moving freely. So, the printer keeps trying to fill the build tray with resin that’s not there. It’s not there because the resin tank is completely empty despite the printer saying it’s half full. I guess it only uses the level sensor in the build try to estimate resin volume and there is no flowmeter or anything better to more accurately determine remaining resin level in the tank. That’s what Formlabs told me anyway. So, it will continue trying to fill the build tray for a great deal of time. In my case it’s about 1.75 hrs until finally the printer realizes that nothing is coming out of the empty resin tank and thus the fill level sensor in the tray also isn’t moving. At this point, the printer will prompt you on screen if you want to cancel or proceed at your own risk using whatever resin remains in the build tray. In most cases even with a newly 100% empty resin tank, the build tray itself holds enough extra resin to complete a decent number of additional prints before it finally runs out as well. If I’m going to do future prints using the same resin I might load a new resin tank in, in which case the problem goes away because the fill level sensor can detect additional resin being dispensed. However, in most cases I switch materials or put build trays in storage so it is very common for me to usually first continue to run prints until the build tray is almost completely empty. In this case the problem does not go away and rears its ugly head.

Looking at my dashboard, I successfully completed 6 or 7 additional prints using only the resin left in the build tray itself. Again, the resin tank was completely empty for all these prints. Additionally for all these prints, I had to wait for what seems to be 1.5-1.75hrs before I could start any of the prints themselves. I had to wait this long because that’s how long it takes for the printer to figure out the resin tank is empty before throwing the message on the Form3+ screen.

Ok, so I I have to wait for an hour and a half before I can start my 30 minute print, or whatever it is. For me this wait time is frustrating enough given that I’m usually just trying to quickly bang out a part. In addition to the wait time, you can no longer automatically send a print to the printer and have it automatically start because eventually the warning pops up on the screen and you have to make a selection before it’ll proceed. So you have to sit and wait for the hour and a half so you can then select the option to continue printing with whatever resin is left in the build tray. As I mentioned, I have one of these printers at home and admin the one at work too. The printer we have at work is down in the labs so it’s not like I can just casually look over my should while at my desk and wait for the message to pop up on the screen. It means that I have to make many trips down to the lab in between meetings specifically to see if the message has popped up yet. This makes a print that should take an hour from start to finish, including priming and warmup, to take more like 2-3 hours. It’s bad workflow and there are some easy things that could be done to mitigate.

Here are some reasonable ideas I have to address this pain point. I’ve suggested these to Formlabs in the past but they didn’t get far given how much time has past and how none of them have been addressed at all as far as I’m aware.

  1. Root cause is that the printer can’t accurately estimate resin level remaining. I understand this is in large part due to the fact that there is no flowrate sensor for resin dispensing and it all relies on the build tray level sensor. So the level sensor does a fine job for making sure there is enough resin in the build tray but doesn’t do a good job for estimating dispensed volume. I can sort of appreciate the difficulty with trying to use the level sensor in place of a flowmeter for resin dispensing. I understand that this would never be 100% accurate, or maybe even 90% accurate. But 50% is unacceptable and unusable.
    Idea 1] Formlabs might as well just do away with showing the estimated remaining resin in the tank if it is wrong by 50%. A 50% error makes any estimate pretty much worthless. This is more of a psychological correction than a feature update but I don’t think there’s much point to showing resin level remaining if it’s completely wrong. The printer is literally lying to you.
    Idea 2] I work in the sensor design industry and firmly believe that 50% accuracy could be improved to at least 70-80% or better by improving the printer’s algorithms. An empirical study could easily be done by Formlabs to show the correlation between build tank level readings and the volume of resin dispensed. They must be correlated well somehow given that the resin tank dispenses directly into the build tray. I think the algorithm currently used is simply not that good and really don’t think it would be hard to make some relatively simple changes to the code and how/when sensor data is used to extrapolate resin volume. Even a marginal value like 80% accurate would be much, much better than the current situation.

  2. Difficulty in estimating resin volume aside, some software tweaks could also just be made to the printer to minimize the pain that comes from the root cause. Let’s just say Formlabs was unable to improve the accuracy of resin dispensing volume and we have to live it with.
    Idea 3] Instead of having a 1.5-1.75 hr timeout before the printer finally asks if you want to cancel or proceed, why not simply reduce this time to something more reasonable. 15 minutes or even 30 minutes would be a much shorter wait and I don’t think there’s be many downsides to this. There is no need for the printer to spin its wheels needlessly for longer periods of time. After all, if there is a clogged bite valve or stuck build tray level sensor, they also don’t need to take 1.5 hrs to trigger and 15 minutes would be a more productive time period. Reducing this timeout interval seems like a trivial no-brainer for Formlabs to me. It’s not even a perfect solution but in my case would make me a 90% happier camper, so to speak.
    Idea 4] I try to suggest all software changes since I get that Formlabs doesn’t want to implement additional hardware costs. But push come to shove even additional cheap sensors could be implemented even as add-on upgrade kits. I’d personally pay a couple hundred more bucks for some bolt-on sensor kit if it resolved this issue. Of course a flowmeter could be used but this might be expensive and also may not work well with such viscous and slow-flowing liquids. So another sensor such as a break beam optical sensor could be used. They are dirt cheap ($5USD or less) and extremely easy to integrate. One could insert a break beam sensor where the resin dispenses from the tank’s bite valve right before it goes into the build tank. There’s plenty of space there and it wouldn’t be too difficult to find a way to mount it. Heck, double sided foam tape would probably do the trick. This way, the sensor would immediately detect whether or not resin was flowing from the resin tank and into the build tray. If there was no resin flow detected the printer could immediately display an on-screen warning that the bite valve is clogged or that the resin tank is empty. The word “immediately” being the key there. You wouldn’t get accurate resin volume level, but honesty that’d be secondary at this point and I’m not sure I actually care about that problem primarily since I’m not tracking cost/resin used per part. Again, I care about the huge time suck involved and reducing the wasted time is what I care about most. With this break beam sensor, you’d no longer have to wait 1.5+ hours for the build tray level sensor to timeout and could immediately tell the printer to cancel or keep printing with whatever resin remains in the tank.

So there’s four reasonable ideas. Formlabs keeps saying that there’s either no fix for #1 or that they won’t work on it. I can’t understand why they haven’t done anything with the other three ideas I just came up with on the spot then. There’s got to be more that I haven’t thought of as well. I, along with a few other users, brought up these issues around 2 years ago. Since then I’ve had half a dozen Formlabs reps tell me they hear my concerns, are working on it, or that I should submit a request. It’s all just talk, and I don’t feel like Formlabs reps have really heard me. At least not enough to show they give a damn. 2 years is more than enough time to address this issue if they wanted to. Formlabs simply won’t prioritize it enough or don’t care. I’m tired of the lip service. I paid thousands for a premium product with what I thought was good support. Overall the printer is still great, but has some serious issues that could easily be improved if Formlabs wanted to do something about it. I’ve complained, submitted requests, and tried to find workarounds. I guess I’m just ranting into the void at this point. Props to you if you actually read my thoughts and ideas. Many kudos to Formlabs IF they ever decide to do anything about it.

To the Formlabs reps: know that my next SLA printer will NOT be a Formlabs product. And it’s not because of the printer itself. It’s because of the lousy support and issue resolution. Yeah, you’re all active on the forums and can link other partially-related posts, but I have yet to see ANY of my complaints actually and fully addressed, or ideas implemented. Until you can prove to me that you care by implementing a fix of some kind, or ANY kind for that matter, I will forever be convinced that you don’t really care enough to fix it and get my business again in the future. I sincerely hope you can prove me wrong by affecting some kind of changes.

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An idea I had proposed in the past was for us to be able to weight the resin cartridge, then enter that value in preform before each print.
Preform would have a database with all cartridges (empty and full weight), and that would give a much closer estimate.

They have implement a weight sensor in the 3L, but not on 3/3+. A cheap way of thinking in my opinion, what would be the cost of it??

Load cell sensors are also VERY cheap. A quick search shows they can be purchased for less than $10. It is an interesting concept. I know that they do tend to have drift issues over long time periods and taring is often required. Newer load cells may bypass this issue and I kind of doubt it would be a problem with small load application like a resin cartridge. It’s yet another good idea that Formlabs could consider, but I’m skeptical they will for the 3/3+…