I just also thought of this: Depending on your cleaning of plate ritual, it may have built up a microfilm. Some areas have high degrees of minerals in them. Wonder if that could be the culprit.....just bouncing ideas off the wall here....
I like to wash in a sink with soap and water and scrub it well, then rinse, then wash with glass cleaner then dry with paper towel and then give it a coating of PVA mixed with water. There's 3 easy ways to get liquid pva onto the glass. It really helps.
I'm not sure what changed. There could be some oil. Or maybe something is wrong with auto leveling (it's important that the spring in the core is stronger than the springs in the bed but in this case it levels too low which means it sticks better so I doubt it is that). Or maybe what changed is your models are larger or you increased infill percentage (which pulls inward on the upper layers applying more stress). Or maybe you used to have rounded corners or brim and decided sharp corners are better.
Lifting corners and how to deal with this is too complicated to explain here especially since I spent dozens of hours getting it all down into one 15 minute video. I know - 15 minutes seems like too much time. But if you want the full answer to your question you really need to watch the whole thing. Sorry.
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Thanks for the suggestions guys - I forgot to mention that our printers are UM2+, not that it should really makes a difference I suppose.
I have given the build plates a really good clean as @gr5 has suggested - great video by the way! - so will see how the next set of prints goes. I am kind of reluctant to use glue on the surface if possible, but I realised that although I am fairly religious in cleaning the bed with the alcohol I hadn't given it a good clean in soapy water etc for a while. I have also relevelled the bed as per @gr5's video.
I also understand that using brim would improve adhesion, but as we hadn't had this problem before we haven't really had a need to use it. I guess if nothing else works then we may need to go down this route, although time is usually critical so if we can away with not having any extra post-processing it makes things easier ? . Usually we use minimal infill (20%, 2 graduated steps @ 5mm intervals so I wouldn't have thought that would be putting too much extra force on the print - but again, it wasn't an issue before.
We'll see how we go...
I have not heard of glass plates wearing off. It is possible that some materials damage the glass, like pulling off a shard of glass, when you don't use the proper adhesives. And these are bigger than micro pits. @kmanstudios , do you have any references to where you might have read/seen this?
Have you tried both sides of the glass plates? This has not always been a problem for everyone, but perhaps you could try flipping it (again).
Curious to see how your next prints will go @model_dude
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37 minutes ago, SandervG said:@kmanstudios , do you have any references to where you might have read/seen this?
I will have to hunt, but I am not sure I can find it. This was ages ago on the forum. It was right about the time that I started printing and was just sucking up information.
It was one of the reasons I started to slurry all prints....the PVA slurry kinda put a slight protective layer down. And, it happened after I put a couple of major divots in my glass getting too aggressive with print removal.....
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If you don't like brim and glue but need to try one of them - glue is much easier and the smaller evil. Once dry you don't have to do anything to the glass for dozens of prints.
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Ok well... I came in this morning to find one of the prints had dislodged from the bed and left filament spaghetti everywhere, including through the remaining 3 prints on the bed - and even they showed significant warping/lifting anyway ? So just cleaning the bed didn't seem to solve anything. Tick that one off the list ✔️
So am now trying a PVA slurry on the bed and will see how that goes ?
While we have had trouble removing prints before the glass plate shows no signs of any damage. @SandervG is there actually a 'better' side to the glass plate? I have read people say that the side of the plate with the sticker on it supposedly has a layer on that allows for better adhesion, but I have tried it before and found no difference.
I am also wondering if it could be related to the ambient temperature, as we are in winter down here and the problem does seem to be a bit more severe at night. We are in an air conditioned office but I don't believe it runs all through the night, so the air temp is likely lower than through the day. Having said that though, we didn't have these same issues last winter and this year isn't really any colder.
Does anyone use an enclosure? I assume that you would need to tweak settings (bed temp etc) a bit to make an allowance for the extra heat that would be retained?
Have you tried manual-leveling? Auto-Leveling uses the first layer to compensate the Z-offset. I think it could have problem if the offset is too large. Since you don't have the issue until recently, it might be caused by improper force while removing the prints. Or, someone played with your printer and you don't know that. The plate (under the glass) might be bended by the improper force. By doing a manual-leveling, you adjust the screws under the plate to ensure the offset is within a proper range. Then you can still use auto-leveling when printing.
1 hour ago, rcfocus said:Have you tried manual-leveling? Auto-Leveling uses the first layer to compensate the Z-offset. I think it could have problem if the offset is too large. Since you don't have the issue until recently, it might be caused by improper force while removing the prints. Or, someone played with your printer and you don't know that. The plate (under the glass) might be bended by the improper force. By doing a manual-leveling, you adjust the screws under the plate to ensure the offset is within a proper range. Then you can still use auto-leveling when printing.
We have 2+ and 2+ Extended printers - so only manual levelling ?
The bed itself (glass and metal plate) seems to be pretty level - when doing large prints, skirt lines and bottom layers are all consistent.
First test print with PLA applied to plate has turned out well - no lifting. But the PVA came away with the print and I needed to apply more to the bed to fill in the 'hole'. Now doing a second print which is larger and extends closer to the edge of the bed, so will see how that one goes.
@gr5 - does your PVA slurry come away with the print when it is removed? Or does it stick to the plate?
When I use a PVA slurry with a print, I usually have to soak the plate in some water to get it loose. A bit of running water aimed at the plate will get it off quicker than just a soak.
The few times I can lift the print off, there is always a bit of PVA left on the plate, but the rest of it comes right off and stays with the PLA and that I have to soak off no matter what.
I know the newer plates have the better side for printing on the side of the sticky. I can feel it when I clean as my fingers squeak on it much more than on the backside.
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? Mine is UM3. I don't have UM2+ and don't know it doesn't support auto-leveling.
As you, I don't use glue on glass. Before each print, I clean the glass by alcohol carefully. So far, I never encounter this kind of issue. So, this method works well for me.
If you can find a solution then you probably have to replace the glass with a new one.... at least to test if it is due to the glass.
20 minutes ago, rcfocus said:As you, I don't use glue on glass. Before each print, I clean the glass by alcohol carefully. So far, I never encounter this kind of issue. So, this method works well for me.
For me, the slurry is a two fold op for me.
1. Helps with adhesion.
2. Puts a protective layer down to prevent any damage, no matter how small, to the glass since the other materials are buffered by the thin layer between the plastics and the glass.
14 minutes ago, rcfocus said:? Mine is UM3. I don't have UM2+ and don't know it doesn't support auto-leveling.
As you, I don't use glue on glass. Before each print, I clean the glass by alcohol carefully. So far, I never encounter this kind of issue. So, this method works well for me.
If you can find a solution then you probably have to replace the glass with a new one.... at least to test if it is due to the glass.
All good ? Hopefully we may be getting a UM3 to go with our UM2+ printers in the not too distant future.
So far so good - the second longer print has worked well too. Mind you, this is just with a single piece on the bed - the real test will be to try and printing multiple items together to see if the extra time between layers makes any difference, as well as doing them overnight. But first, baby steps dear grasshopper... ?
I must admit I am kind of tempted to try a new glass bed to see if that makes any difference to printing, and as @kmanstudios suggests that one side is better than the other. It isn't too expensive so might be worth a shot depending on how I keep going with the PVA...
I have seen this happened, more than one occasion and on different printer. UM1, UM2 Clone (original UM2 heated bed and glass build plate), FF Dreamer but not yet on my UM3 (only 150hrs on it still very new). But this is just my personal experience not a general observation/consensus. Since I know this will eventually happen I just got use to putting PVA slurry, use the gr5 and/or kmanstudios method if possible to have a thin but almost evenly coat. This will have less uneven surface on the bottom print as well as less sticking too well (the glue and print). Not to mention the glass surface peeling is a really bad way to go specially when using PET type material and equivalent so a protective layer is more than welcome.
Now as to why it happened, I stopped asking for the list of reasons as there are a ton of potential reason, model you are printing, duration of print, ambient, z offset (getting far off after sometime), PLA degrade over time and etc. It just happens for some reason but sometimes different from the previous. So rather than wasting plastic I invest on prevention. I did try buildtak, flex plate, tape but glue/PVA slurry is the easiest and cheapest to run not to mention it can last for a few prints specially if you move around the prints. Recently, I got to buy the UM adhesion sheet they are quite good as well but PVA slurry is good enough. each method will have its quirk just select which one is acceptable.
Reading your "habits" on maintenance and printing procedure, stick with that but just as some preventive measure to reduce plastic waste and I think you're good. In fact reading your recent comment you have positive result with PVA slurry.
Oh the enclosure is not a bad idea but i think not necessary, since you print mostly PLA. I do print 40++ hrs print with PLA with open printer just fine but note, I live in tropical climate, temp here fluctuates 24-35C between day and night so I dont have freezing temp.
In the past I too have got to a position where prints no longer stick properly to what seems like perfectly clean glass. It's as if there's something invisible to the naked eye that's causing a lack of adhesion.
I found that using one of those scouring creams like you use for cleaning limescale off in the bathroom (Cif, it's called in the UK) seemed to rejuvenate the adhesion. These creams have a mild abrasion effect and whilst they're not aggressive enough to affect the glass in terms of creating any scratching, using this seems to "rejuvenate" the glass plate so that prints then stick like they did before.
I have no idea what it's doing, either it's removing an invisible film that's built up over time, or having some other effect on the glass to address whatever's caused the deterioration - what I do know is that it works for me.
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@SteveCox3D, Thanks! A possible solution is worth a thousand speculations! I will have to keep this in mind as well :)
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cif is known as jif in australia.
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9 hours ago, model_dude said:But the PVA came away with the print and I needed to apply more to the bed to fill in the 'hole'.
I don't think you need to. Some PVA is left behind I think. In fact parts seem to stick to the "holes" better than the non-holes. I don't know why but it seems the less PVA there is the better it sticks and at some point it sticks too well and I have to add more pva (or just spread it around but that looks ugly so I usually add more instead).
If you print PET or CPE or nGen you should probably remove all the PVA because PET combined with PVA seems to be the leading cause of chips of glass removed from the bed.
The poster earlier who mentioned about the bed being bent - that's an interesting point. Probably not the issue but the aluminum bed can be bent and the glass bends with very little force. 0.2mm of height change in a corner can make a big difference if you print in that corner. In general the left and right rear corners are most problematic because they are farthest from where you leveled. So those are the best 2 areas to avoid.
You can use a metal ruler to check how flat your bed is. But I doubt this is your issue. This is a common issue on the UM3 but for some reason not as much on the UM2. More importantly the bed is unlikely to change over time. It takes a LOT of force to bend it permanently - I know - I did it on purpose.
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27 minutes ago, gr5 said:I don't know why but it seems the less PVA there is the better it sticks and at some point it sticks too well and I have to add more pva (or just spread it around but that looks ugly so I usually add more instead).
I will have to agree with this. I have tested everything from thick layers to thin layers. Thin layers worked the best. I am experimenting with adding a touch of alcohol (Isopropyl) just to cut the surface tension. I found this out one day when I put the PVA slurry on the bed immediately after cleaning with alcohol and it really improved things a lot by letting it level out better and made it thinner.
2 hours ago, kmanstudios said:and it really improved things a lot by letting it level out better and made it thinner.
Ah. Maybe the secret to 3dlac.
Well the PVA slurry seems to be working pretty well so far, so for the moment we have stopped having the issue with lifting/warping of prints ?
Thank you to @gr5 and @kmanstudios for your tips/advice/suggestions!
Thank you to to @SteveCox3D for the Cif/Jif tip - I will be giving that a go to see if that works too ?
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Your *environment* could also play a big role: air moisture and temperature. In the beginning a couple of years ago, when printing on bare glass (=no bonding method), I had reasonable bonding in cold freezing weather (=very dry air). However, in moist, rainy weather, I got no bonding at all. Nothing else had changed. It was very frustrating. This is when I started searching for a suitable bonding method.
Now, for bonding PLA my "salt method" seems to level out these differences, even though I still don't know why it works, from a chemical viewpoint.
Salt method = gently wipe the glass plate with a tissue moistened with salt water. Keep wiping while it dries, so it leaves a thin, almost invisible mist of salt stuck to the glass.
When hot, models stick like glued. But after cooling they come off by themself. It is very well suited for low, long 100% filled models like I usually print: I have done maybe 1000 models since then. But it may be less suited for high narrow models.
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If I remember correctly, over time, micro pits are created in the glass by pulling off prints if they are really stuck on.
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