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Printing PLA flat (minimize seam lines)


Ronan

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Posted · Printing PLA flat (minimize seam lines)

I tried with glue, got the result on the left, cleaned the plate, used the spray (waited for it to dry) and got the result on the right. So at the end of the day, it's not a adhesion problem but a shrinkage problem i have now...

I came upon this site: http://support.3dverkstan.se/article/23-a-visual-ultimaker-troubleshooting-guide

This is my problem (Wall Cave In: http://support.3dverkstan.se/article/23-a-visual-ultimaker-troubleshooting-guide#wallcavein

Seems to be a sticking issue + bed being too hot (i run mine at 60 degree's). So i will try a raft to see if it protects the small parts (they are not THAT small though and i print 4-5 at the same time).

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    Posted · Printing PLA flat (minimize seam lines)

    Ok, all I can say is that my personal opinion is that 60 is not to hot. I always print at 65 and have never experienced wall cave in. In the early days I did try 60 but found that larger pieces, footprint at least a third of the bed size, suffered adhesion so I changed to 65 and have left it there for the last 2+ years. Every new filament I try I always print a variety of test cubes, 10mm or 20mm, to establish the best settings, including straight vertical edges, and they always are.

    Irrespective of whether they solve your wall cave-in you will help yourself generally if you standardise your print speeds for small models (if you can get 5 on a bed I count those as small), don't blast you fan on at 100% at .5mm height and get your over high extruder temp down.

    Let's hope you <60 bed temp solves it :)

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    Posted · Printing PLA flat (minimize seam lines)

    "wall cave in" is what jechsturk replied to your very first post Ronan. He called it "elephant foot". It is caused by the bed being too hot. When printing PLA it cools extremely rapidly as it comes out of the nozzle shrinks within milliseconds and acts like a liquid rubber band for a short period before it freezes - like snot. So corners are pulled inwards hence "wall cave in". Simply lower your bed temp another 5C to 55C and this should go away completely.

    Getting your part to stick is best done with brim but if you don't want to use brim just loosen the 3 screws on the bed 1/4 turn (.025mm) moving the bed closer to the nozzle slightly. Possibly also start over with the glue - you want a very thin layer of PVA and dust may have accumulated over the past few days.

    It really sucks that I can't see any of your pictures except for one now - it's really best to use the "image gallery" button (2nd from right) above where you create the post and not "add external image". It's also a bit rude to post a photo from some image website that may drop the picture after a few days/weeks/months/years whereas Ultimaker will host your photo as long as they host this topic.

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    Posted · Printing PLA flat (minimize seam lines)

    Oh and "raft" will likely help but it will make the bottom of the part very ugly and you wont be able to glue it together. "raft" is an older technology and no one uses it anymore now that we have newer technologies like blue tape and after that, then heated kapton, and now we are at heated glass - the best I've seen so far (although there is "build tak" which is even newer but I'm not convinced it's better than heated glass). The raft warps/bends and so the part can shrink the tiniest amount and not lift off the glass and still be dimensionally accurate.

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    Posted (edited) · Printing PLA flat (minimize seam lines)

    Let's start over - now that I've finally seen a photo of your 2 problems.

    For wall cave in you need to cool things down - usually the bed is enough but maybe you should cool down your nozzle temp also.  Also get that fan going by .5mm off the bed.

    For sticking to the bed you need to add brim.  It sucks when you want to glue two pieces together but if you have the right tools (razor blade, mini set of files) it's really not so bad to remove the brim after.  And you need PVA glue and you need the bed above 40C and you need the nozzle slightly closer to the bed (squish that bottom layer in there good!).

    There is a compromise bed temp - the cooler it is the less "wall cave in" you will get.  The hotter it is the less you have to worry about "corners warping up off the bed".  For most of us that is 60C.  At 75C you get zero "lifting off the bed" but horrible "wall cave in" but if you can get it to stick like hell (PVA, brim, squish) then you should be able to get by with 50C or 60C bed temp.

    Edited by Guest
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    Posted (edited) · Printing PLA flat (minimize seam lines)

    Update: Same settings + raft, part comes out 90% perfect, the bottom against the raft being slightly deformed (less than before, but still deformed but no wall cave in or corners peeling back). So what gr5 said!

    Can't use brims, i have hundreds of those parts to print, if i have to go over each one to clean them up, it defeats the purpose and i'm better off using a plastic injection method (blah).

    I will try to lower the bed temp, which is at 60 right now + using the PVA glue method. Using PVA glue + bed at 60 = wall cave in ruining the part.

    It's too bad the raft deforms the part printed on top...

    Edited by Guest
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    Posted · Printing PLA flat (minimize seam lines)

    I agree with what Yellowshark said. I think with smaller parts like that, you're going to want to print slow and cool. 205 or 200 may do the trick, but you might try cooler depending on your filament.

    You also mentioned that you were printing with a hood and door. Have you tried printing without the hood or opening the door? With smaller parts, I generally don't enclose my machines at all. I put a cover over the front if I'm printing ABS, or if I have a PLA print that covers most of the bed. You're probably ending up with a lot of ambient heat inside the machine.

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    Posted (edited) · Printing PLA flat (minimize seam lines)

    I have to use the door/hood otherwise it's too noisy (printers are next to me).

    I just tried another print, this time at 55 degrees for the bed with pva glue/water layer. It stuck really well but it had the wall cave in (zero peeling/curling this time). That was one print at 25 minute total, so no chance of it 'cooking' on the bed.

    I'll try everything slow/cool for the next one.

    The goal is basically to print 'lego shape/size' pieces that will fit together nicely/properly. It's a huge project we are working on, making everything modular. Our parts can of course be printed any size, but at 'conventional' size it needs to look properly and fit properly (some people will glue them together + paint, other will use our snap-pin system so they can change their constructions/inventions).

    It's beyond critical to get it right at this stage. Pulling my hair out on this one haha...

    Edit: I wanted to mention i have seen people print lego's on blue tape at 50 mm/s speed and they came out... perfect. So i know it's something to do with too much heat/speed... So gonna try to cool the nozzle down, slow everything up... and see how it goes!

    Edited by Guest
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    Posted · Printing PLA flat (minimize seam lines)

    If you've got Ultimaker 2+ machines, the fans should be fairly quiet. Would going without the hood or without the door (rather than without both), be an option? It really does sound like there's too much heat in there.

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    Posted · Printing PLA flat (minimize seam lines)

    If you've got Ultimaker 2+ machines, the fans should be fairly quiet. Would going without the hood or without the door (rather than without both), be an option? It really does sound like there's too much heat in there.

     

    Trying yes, in practice no :( Not until i get a seperate place for them.

    One thing i noticed... the cave in of walls happens at around 0.5mm which is when i have my fan 100% setup to start! So gonna change it to 2mm, start at 60% to 100% to see if that changes anything. I'll also lower the nozzle heat a bit, but keep the bed at 60 degrees...

    Wish me luck!

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    Posted · Printing PLA flat (minimize seam lines)

    Because your machine is covered - try lowering the bed to 50C. The PLA should stick just as well.

    I did experiments where I did a 2 minute print (the bottom 5 layers of the ultimaker robot) about 20 times with different settings. I used a scale and a screwdriver to push the part off the bed (while bed was still hot) and measured the force.

    I tried glue/noglue. I tried hairspray. I tried many different temperatures. There was a huge difference around 35C where cooler than 35C and the part came of with about 1/10 the force. After that I never print with bed cooler than 40C. 50C should be quite safe - well above that critical threshold.

    The next threshold is around 60C to 70C where you are above the glass temp of PLA and if you can keep the bottom 2mm of the part above glass temp you get horrible "wall cave in" but you get zero "lifting off bed" problems. You don't want wall cave in" so once you are down to 60C there isn't much "down side" to going even cooler to 50C as you are now below glass temp of PLA anyway.

    Finally another completely different option - you could print the bottom 5mm of the part at 190C and at 1/4 speed and then speed it up when you are well past the "wall cave in" area. If this works you can hand edit the gcode or use the "tweakAtZ" plugin to change temp and/or speed at a given Z height.

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    Posted · Printing PLA flat (minimize seam lines)

    Oh - and blue tape is actually a reasonable option for you. But it's critical that you clean the blue tape with isopropyl alcohol to get the wax off the non-sticky side of the painters tape.

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    Posted (edited) · Printing PLA flat (minimize seam lines)

    So this is what i tried on PVA glue:

    Same settings as before but with yellowshark tweaks, bed at 55, nozzle at 200, fan start 30% at 2mm. Same result except the cave in was bigger.

    Same settings but with the hood + door taken off, same results as above but edges curled.

    So those 2 prints were worst than before.

    So it seems that the fans are causing the wall cave in... should i try having them on from the beginning? Will that hurt the first layers even though the bed is at 50/55/60 + PVA glue?? Do i raise the bed in this case?...

    Edited by Guest
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    Posted · Printing PLA flat (minimize seam lines)

    Update: Did a quick test print, on blue tape, stock cura settings, came out 99% perfect. The 1% being one of the corners lifted ever so slightly.

    So it's a heat issue causing the peeling which was resolved using the PLA glue, but then everything is to hot and as soon the fans turns on, it causes wall cave in.

    Any idea how to print this on a hot bed? Otherwise i am going to end up going through a lot of blue tape...!

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    Posted · Printing PLA flat (minimize seam lines)

    >The 1% being one of the corners lifted ever so slightly.

    Shouldn't happen. Did you remember to clean it with isopropyl alcohol? I've had tape come off the glass but never part come off the tape. Again you need to squish it a bit just like with glass to get in the nooks and crannies of the tape.

    I can't see how fan could possibly make wall-cave-in worse.

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    Posted · Printing PLA flat (minimize seam lines)

    I tried again with tape, this time it turned out fine. There must have been a bit of wax left before.

    Now my issue is the tape is good once, after i peel it off, you can see the top layer of the tape ripping off. It's a minor issue but heh. I'm also seeing trouble for the bigger parts, taking them off w/o breaking (or is it just the tape that breaks off?).

    More testing to do. I'm also tempted doing a test at 50 degree's hot bed, but seems to be the fans go on and the wall cave in happens (it moves up/down the part when i change when the fans turn on)...

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    Posted · Printing PLA flat (minimize seam lines)

    1) Let the tape rip and make a mess.

    2) Place the print in a pan with a very thin layer/puddle of isopropyl alcohol for 5 minutes. Then the tape almost falls off.

    3) Re tape your bed after each print.

    Now you see why glass and PVA is an improvement for most people. I have no idea why you have so much wall-cave-in. I'm thinking your heated bed is like 20C hotter than normal and the temp sensor is way off. Do you have an independent method of measuring bed temp such as an IR temperature gun?

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    Posted (edited) · Printing PLA flat (minimize seam lines)

    My temp sensor gun is dead so i would have to buy another one to confirm the bed temperature. That or once the other Ulti's are finally free then i can try on one of those.

    I'm curious, how often do you have to clean + recoat with PVA glue?

    Edited by Guest
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    Posted · Printing PLA flat (minimize seam lines)

    At least once per month I take the glass out and wash in the sink with soap and water to get all the accumulated dust off the top. Even if I only did 1 print that month.

    I often go 10 prints before re-wetting the glue. I don't usually reapply glue unless it's because I washed the glass.

    To re-wet the PVA I take a small paintbrush soak it in water, then spread it around on the glass mixing the water into the PVA for about 10 seconds then turn the bed heat on and dry again and ready to go within 5 minutes. Everytime I rewet the glass gets ugly around the edges so after doing that 2 or 3 times I decide it's too ugly and wash it clean again.

    My favorite PVA is elmers wood glue mixed 1 part glue, 10 to 20 parts water. Spread with paint brush. I keep a jar of this mixture and a clean paint brush in the same room as my printers.

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    Posted · Printing PLA flat (minimize seam lines)

    Oh - one more thing - for large prints - say 150mm wide or longer on one axis - I do an extra good job because it's that much more critical (much more powerful warping/lifting forces). So I will usually completely wash the glass and apply a fresh coat before any print longer than 150mm. Such as a quadcopter plate or arm.

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    Posted · Printing PLA flat (minimize seam lines)

    Here's the kicker... did a full print last night on tape, cold glass, tape cleaned with alcohol.

    Half the parts came perfect, the other half came deformed. Those are all the same parts just printed in multitude. It seems to me something is wrong, and its been causing issues over the past few days.

    I am going to clean the glass (again), relevel the bed (again), reset the settings, print a ulti bot on my normal settings and see what happens. I also finally have another printer that is free, so it's gonna take a print today to check.

    I shouldn't have to print on tape those parts, there's nothing 'weird' about them (it's like printing a rectangle lego block basically).

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    Posted · Printing PLA flat (minimize seam lines)
    I shouldn't have to print on tape those parts, there's nothing 'weird' about them (it's like printing a rectangle lego block basically).

    I agree. But apparently you don't like to squish your bottom layer as much as I do - so that's one issue (even just raising the bed 0.01mm will help - yes .01mm not .1mm). I don't blame you - for dimensionally perfect parts I do the same thing - I don't squish the bottom layer at all and have the same issue - parts occasionally warp off the bed. Also you don't like brim.

    As for "wall-cave-in" the only thing I can imagine that changed is that your air temp or your bed temp (and hence air temp) is warmer than it was when things were working fine. For some reason the air is warmer than before - maybe a fan 50 feet away used to be pointing at the printer but now points a different direction - it could be many things that affect temperature and airflow.

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    Posted (edited) · Printing PLA flat (minimize seam lines)

    I just tried half a dozen prints on a regular ultimaker 2. Exactly the same issues (this one has no hood, no door, used normal settings).

    When ever i print on tape and shut the bed heat off, the parts print perfectly (they are insanely hard to get off the bed though!).

    I have now tried it with 2 different ultimaker and colorfabb PLA, i keep getting the same results both ways. It seems to be there's a LOT of fine tuning to print 'lego' like blocks on a hot bed, while on the cold one i can use regular PLA settings with the hot bed set to 0.

    Edited by Guest
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    Posted · Printing PLA flat (minimize seam lines)

    If you skip the alcohol cleaning step then parts stick less-well.

    Which of the united states are you in Ronan?

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    Posted · Printing PLA flat (minimize seam lines)

    If you skip the alcohol cleaning step then parts stick less-well.

    Which of the united states are you in Ronan?

     

    I'm in MD, right next to Washington DC.

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