Tank - Slowly (Original)

Slow sand filters slowly lose their performance as the biofilm thickens and thereby reduces the rate of flow through the filter. Eventually, it is necessary to refurbish the filter. Two methods are commonly used to do this. In the first, the top few millimetres of fine sand is scraped off to expose a new layer of clean sand. Water is then decanted back into the filter and re-circulated for a few hours to allow a new biofilm to develop. The filter is then filled to full volume and brought back into service.[10] The second method, sometimes called wet harrowing, involves lowering the water level to just above the hypogeal layer, stirring the sand; thus precipitating any solids held in that layer and allowing the remaining water to wash through the sand. The filter column is then filled to full capacity and brought back into service. Wet harrowing can allow the filter to be brought back into service more quickly.[9]

Tank - Slowly (Original)

No luck and still get slow leaks that need to be cleaned up off of the edge of the moving LCD platform way too frequently. Best I can tell is that the leak is coming from the holes where the tank bolts to the LCD platform, and it seems like the frame metal is too thin and flimsy to get a good seal in that area. Looking for help here as I want to enjoy resin printing more, but this leak has been keeping me cleaning up more than just printing.

Yes, the frame metal is flimsy, but its acting like a great big washer for all the screws. The screws are so close together that screwing them down tight should give an even seal to stop liquid leaking. You may even like to take the resin tank out of the printer and fill it up with water? Make sure its not leaking before putting it back in.

Another reason for seeing resin below the FEP may be that you transfer some resin there accidentally when cleaning the resin tank? I use a fresh sheet of paper towel to wipe the underside of the FEP and then am careful not to touch the underside of the FEP again.

I've tried tightening to various levels starting light and working my way to crazy hard. Did the water test, leaking slowly. Visually inspected the tank for defects, nothing visibly wrong. Everything points to the current tank/frame design being poor and prone to failures. It's like it's missing a necessary o-ring. I'm pretty much out of ideas on how to get my SL1 back up and running reliably without the dread of a slow leek.

Just had this happen to me. I absolutely know that resin was not spilled outside the tank in any quantity, but when I went to empty the tank yesterday due to a failed print I found my LCD covered in resin (including some cured areas). I cleaned the tank and can find no sign of a puncture or tear. I filled it with water (well past the 100% mark) and placed it on a paper towel most of yesterday and over night, this morning the towel was still dry. Obviously that is a static test and does not account for the movements during the printing process, but prior to putting it down I did poke at the underside a bit to try to simulate the layer change force.

Haven't changed the FEP on the tank yet as I had a second tank. Found a print failure this morning with part of the print attached to the FEP. Finally got around to dealing with it and when I pulled the tank to empty it I found a nice mess underneath.

Both tanks had their FEPs installed by Prusa. Both tanks passed water leak tests prior to going on the printer. The first tank passed water tests after getting cleaned up. I know for certain that no resin was spilled. WTH is going on? I wasted most of Saturday cleaning up the printer and now I've got to do it again a few days later?

Have you tried with water in the tank gently pushing up on the FEP film from the bottom? This should show in short order if the pulling action of the lifting build plate is opening a small hole that is otherwise not present.

I did think of that mainly because it parks the tank in the down position after a print. If I refill to 100% at that point it is then well above the 100% mark when it raises the tank back up to start printing. So when I switched tanks I also started raising the tank to the level position before adding resin to the 100% mark. I have also watched closely for any sign of splashing and seen none (e.g. no residual resin down the sides of the tank.

The first leak was a royal mess by the time I found it (it didn't drip into the printer that I could see, but I did have to unbolt the LCD so I could lift it out and clean the frame) so trying to identify a source was fruitless (I also assumed that I had punctured the FEP). In this second case all the resin was located within the bounds of the print area on the LCD (e.g. definitely not ran down the side and seeped under). After wiping the tank off I don't see any indication that it worked itself from inside out (e.g. bad FEP seal) either.

Once I clean the second tank up I'll be able to find out for sure, but I highly doubt a puncture as the only thing that has touched it is resin, water, and a cotton pad. So unless the print process itself is tearing/puncturing it I don't see how a puncture is possible.

Support's response was that FEPs are only guaranteed for 10 prints (seriously?) and (summarizing) I need to change the FEP more often. For the record, the first tank may have hit the 10 print mark, but the second tank was at 5 tops.

In talking to him, however, I did notice a pattern. With the first failure I had a print fail in a "printed, but not correctly" way. I ran my finger and a plastic spatula against the FEP and didn't feel anything so I tried the print again. It failed, but in a worse manner that left part of the print stuck to the FEP. When I removed the tank to clean that up is when I found the leak. For the second tank I had a print fail yesterday where everything came out of the resin, but there was warpage and the parts had pulled away from supports in some places. I figured that the orientation was the problem (they weren't parallel with the platform, but not far off) so I resliced, tried again, and ended up with the failure that required me to empty the tank.

... It occurs to me that if the print sticks really well, the FEP might "snap" loose when peeling prints, and maybe flick some resin out of the tank. But then you should see it in more places than just under the tank...

While possible in theory, I would think it would have to be extremely low (well below the min level) before that would be possible. I would expect the volume and mass of the resin in the tank to dampen such forces to the point that escape velocity wouldn't be possible. Regardless, there are no signs of splashing.

So I replaced the FEPs on both tanks last night. The second tank I didn't bother cleaning first, just wiped the worst of the residual resin out of the way and then cleaned it up while the FEP was off.

When I removed the retaining plate from the tank I found a fair bit of resin underneath it and even more in the recessed area under the FEP. I did notice while cleaning it that there were small amounts of resin between the bottom lip of the tank and FEP which I had to really work to get out. With the retaining plate in place, however, it didn't appear that the resin worked itself up higher.

Given this I'm suspecting that maybe that is what is happening. It's not a perfect seal between tank and FEP so the resin works it's way under and then wicks up under the retaining plate. It then finds exits from the FEP either around the edge or through the screw holes and can then get down to the LCD itself.

There is a fair bit of room between the sides of the plate and the inner sides of the tank. Would there be a negative effect (other than the mess to deal with when changing the FEP) to putting a small bead of silicon sealer inside the tank around the edge?

In my own water tests, this is exactly what is happening. As for the silicon sealer, I've had the same idea, but am concerned about how, not smooth that is going to be and thus any impact on the final result that will have. It's almost like this design is missing an o-ring & channel milled into the tank right by the edge of where the frame sits to get a good water tight seal.

Everything I can think of around this problem still comes back to the initial design of this tank/frame setup as being, well crap and prone to failures like this. Not really what I was expecting coming from Prusa.

I knew about (and didn't like) the low LCD lifetime, but I was prepared for that. The LEDs are another known thing, but should have a decent life. The FEP was the surprise and honestly I may well have rethought it if I understood that changing the FEP was so frequent. Still better than the Form 3 that has a limited (4l I think) life span for their tanks and you have to replace the entire tank for what you can buy a cheap resin printer for...

So here's exactly why this tank/frame/fep design is a problem The attached image is from my most recent brand new Prusa replacement FEP and water test that failed. As you can see in the attached image, the FEP stretches, we know this as this is what ensures a tight flat surface to print on. Well, the pre punched screw holes also stretch, and in some cases enough to reach the edge of the frame and provide the perfect spot for water to leak through. This FEP was installed using a traditional cross tightening pattern as mentioned in the FEP installation documents. There is 100% absolutely nothing we as consumers can do to prevent this, it's fully up to shear dumb luck / material consistency at the punch holes as to if they stretch enough during installation to leak or not. 041b061a72