Guys what can cause a print to start warping 2 to 3 hours into a print?
What material are you using? With ABS It normally means your bed is not hot enough but if the area is too large it could mean a slightly warped bed.
PLA. And its fine on prints that take less than a couple of hours. Anything longer and it start warping
Differential cooling. Sometimes you can help mitigate it by the wall thickness and infill % or infill orientation. But if you have a sharp outside corner like a square box, or sharp pointed peninsula feature adding small hold down “Lilly Pads” at the corners usually can do the trick. Just add some one or two layer thickness cylinders I to your slicing software at those corners of the model. When it slices it will join them with the model and increase your surface area contact at the small features. And they remove much more easily than a brim.
Eric is correct about the differential cooling. Upper layers are cooler than the lower ones at the bed and as they shrink they will peel up warmer soft layers below. There are several ways to get around it. I use changing bed temps to avoid it. I start out at 60C which is above the glass temperature for PLA and after 0.5mm (or 3 layers min) in height I drop the bed temp down to 45C which is below the glass temperature. This allows the PLA to stick to the bed starting out and then cool down solid enough so it does not get peeled up by subsequent layers cooling down and shrinking but not so cool that it cracks the part off the bed. The surface of your bed may affect the results. I use 3M Blue painter tape on an aluminum bed washed with Windex (before I put the tape on). The tape sticks really really well and even a part edge or corner landing right on a tape edge does not peel it up.
My print bed is PEI. Thats a great idea with the cylinders! My printer sets the bed temperature to 50°C by default should i change this? Its the PLA filament that came with the Prusa i3 MK2S
You can try a little hotter on the bed. I use 60C on the bed for PLA. But the closer you get to the plastics TG on the bed the more likely the base of the print can flow on long prints creating a ridge (or what some people call “elephant foot”) where the base is slightly wider all around the base.
My preference is Lilly Pads. Then again I started printing almost exclusively ABS, so I needed things like this in my bag of tricks.
Yeah definitely dont want the elephant foot effect. So 60° should be ok? That and a 5mm brim/skirt?
Brim if you need it. But I hate removing them off PLA.
Im fixing to print 5 baby groot heads with 5mm brim
Hoping it all goes well lol
You should try both hotter and colder, because you never know exactly how accurate your bed thermistor is and how that’s interacting with your room temp etc. Too cold means more warping force in the bottom ~1cm or so of the print. Too hot means the bottom ~1cm isn’t fully solid and you don’t have a good foundation for the rest of the print, and later layers will pull up the lower layers.
Another cause for warping that starts late in the print is your AC kicking on. Make sure the printer isn’t near any AC vents.
Lol its sitting in my room with the AC on. Where can i find a good enclosure (or instructions for one) for the Prusa i3 MK2S?
Upside down cardboard box or clear plastic tub is pretty ideal to test if an enclosure will help.
Drafts and breezes that should be cooling cooling fins hitting the print too.
Upside down cardboard box. The innovation!
One dangerous suggestion: Once it is printing some 10th layer, you can apply some adhesive (like superglue) around the bottom layer. It will prevent complete warping when you have many hrs print.
It will stick the print very well to the bed and will surely prevent warping. Applying the superglue is tricky when printing. You should not hit the print or hot end when applying. (Like others suggested adding an enclosure will help along with this glue technique)
Warning : You should use safety precautions like wearing safety glass and safety mask as the glue will produce heavy fumes, particularly with heated bed.