PLA curling on printed part

I print PLA and for the most part I don’t have a big problem with curling around the edges, usually a minor amount if that.

My last print, two of the same thing actually, has been an exception. A 2 1/4" round base 8mm thick with a relief in the middle and a boss on the top for mounting in a 4 jaw chuck. It is a glue chuck for mounting castings to be turned on a lathe. Confused yet. It is an experiment to see if it is viable to make one out of plastic. With the current insane price of metal it seemed like something to try instead of turning one out of aluminum.

All around the bottom it curled and pulled up off the bed but I think I know why so correct me if I’m wrong.

I needed this to be as strong as possible to resist crushing forces of the chuck jaws. So to this end I made the outside walls 9 layers thick, ya I know crazy but it is an experiment. My best guess is that all those layers caused the outside to shrink much more then the rest and caused the curling. I usually have the bed at 60C for the first layer and then 50C for the rest. If you have an other idea I would like to here it.

What is the best temp or the lowest temp that PLA could be printed at and would it be better at stopping curling by lowering the bed temp. below 50C.

I usually print PLA 215 on the nozzle and 60 on the bed with no reduction.

I print 9 walls sometimes more too less as well. I rarely have lifting issues. Is there a draft? that might be the issue. A draft shield might be worth the try. I hate the waste but if it works…

You might try a few extra bottom layers.

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Maybe slow down the print a bit, and try my 70C bed temp… Come to the Dark Side…

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I print in a closed room which heats up if I print for a while, so no drafts.

70C isn’t that going the wrong way. With PLA isn’t lower better then higher??? With that small of a footprint on the bed you probably can’t get lifting, that’s cheating.

I’m still impressed, though, that it didn’t get knocked over.

Don’t take my word for it, try it yourself. Since I went to 70C first layer, 65C subsequent layers, while printing, you could rappel off my prints, after it cools, it’s just sitting there, harsh language will push it off the bed…

do you get elephants foot at that temp with PLA?

Not really. I put some effort into a level bed, so now I use 0.2mm/145% flow for the first layer, 0.1mm elephant compensation.

This is the latest off the bed,

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I watched that video and others where he/they say to clean the bed. I have cleaned the bed over and over, I avoid touching it, I wipe it down with alcohol as a final treatment and I still can’t get things to stick to the pebbly side of the glass plate. I levelled the bed and everything else I can thing of but no joy so I turned it over and use glue, mostly OK but not always. I will try raising the bed temp but that sounds counter intuitive for PLA.

Should the Z offset be closer to the bed to force the plastic down into the area between the bumps?

Mobi why the increase in the flow rate for the first pass?

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I couldn’t get my pebbly side to stick either until I →
Wash with one drop of dish soap and progressively more water, rubbing with fingertips.
Air dry, no touching, no alcohol. Sometimes I dry three bottom off and let the bed heat evaporate the residual water on the top.
Maybe a soft bristle brush(toothbrush) between prints if needed for dust, debris.

70C for the first layer, 65C after. This is the step that really solved my bed sticking problems.
50C for TPU
85C for PETG

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Alright, I have to try these recommendations. While I currently need a hammer and spatula to get the prints off my bed; it does involve a layer of Elmers’.

I’ll be curious to see if it will stick like this without.

Also, does anyone know what the bed surface temperature actually is? With thermistors mounted on the bottom, they are really measuring the bottom temperature and the top surface will be cooler depending on the thickness of the heated plate, the thickness of the build plate on top of the heated plate, whether there’s a micro air gap between the heated plate and the build surface (my problem due to a heated plate with a center bulge), and the thermal conductivity of the build plate (in my case carbon fibre, 5mm thick).

no, but I’ve been thinking about it. my thermistor is right in the middle, I just had to take mine apart. there’s no heated pad on the bottom. there is like trace for heating elements under a ceramic-like paint but the trace goes all the way within about 8mm of the edges. the thermistor is in the aluminum above the level of the heaters by a few millimeters and getting radiated heat from the sides. I don’t know much about the performance of this kind of heating element. but I suspect it’s pretty even and close to accurate from the thermocouple POV. I think the slightest air movement across the bed takes the heat away quickly though so how this kind of element will replace the heat that’s lost away from the middle where the sensor is I don’t know, I can’t see the pattern of the trace or if every part of the element has an end toward where the thermistor is then it might not be so bad If the traces sort of start at the electrical connection then zig-zag everywhere then it’s not going to be great away from the sensor. You will already have roiling warm air rising off the bed and cool air rushing in from the sides so it’s no wonder that draft shield works so well.

With a hard surface, I can see where there could be gaps between the layers. like cheap pans on an electric stove are so wasteful because the heat only transfers to the pan at a contact point.

45.5C @ 50C bed temp, under these conditions. +/- 2C seemed easy to make happen with the slightest breeze or shielding.

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No joy in Mudville tonight.

I changed the temp to 70C for the first pass and down to 65 for the rest, as Mobi suggested, lowered the wall lines to 5 and increase the initial layer line width to 125% since that is suppose to help with adhesion, and I think it did. I also shut the door to the room to stop any drafts, check the Z offset to be safe but the results where the same, curling around the edges just the same as before.

I have a couple of other things to try but maybe it is just the shape of the print that is the problem.

Have you tried Cura’s Draft Shield settings?

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have you tried draft sheild? I haven’t really been following but also what does your first layer look like?

Not yet.

I just tied printing the same part with 70C first layer and down to 40C for the rest just to see what would happen and only about 1/3 done it popped of of the bed with a curl on the base already.

whenever I’ve had trouble like this before I had my enclosure … also once or twice after I used hairspray on the bed and draft shield. fort layers always were good though if your first layer isn’t formed properly then that’s a problem. What’s your cooling like? are you cooling the first few layers?

Aah, sorry.
Least I’m staying on my average of being right at about 10%…

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one question. why are you dropping the bed temp later in the print? why not just keep it the same for the duation?