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svanbennekom

What are your biggest PLA warps on heated beds

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Hi there,

I'm in the process of designing a qualitative test for comparing the warping tendencies of different PLA's.

 

If you experienced warping using PLA at bed temperatures of 50-80 degrees you would greatly help me by answering the following questions:

 

  • Did you experience large scale warping in printing with PLA on a heated bed (Such as on the UM2)?
  • What were you printing?
  • What kind of warping occured?

Good pictures are very much appreciated ofcourse!

Any other input/insights are also very welcome.

I'll post the test once it's finished so you can compare your PLA's at home.

 

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Hi,

I did experience warping only twice. Sadly I don't have any pictures of these parts. But other thant that, warping is pretty much not an issue any more. If I apply a bit of glue(stick) and dillute it a bit with a wet paper towel and set the heated bed to 65°, then every object sticks like crazy and there is never warping involved. With my two warped prints I had forgotten to either apply glue or the heated bed temp was too low.

 

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There's 2 types of warping people seem to associate with heated bed. The most common issue is where the upper layers cool more and pull hard and lift up the corners. This is obviously even worse with no heated bed. Most solutions involve stronger sticking to the bed and I found 30C and hotter to be equally sticky although the threshold is sensitive so that 40C is much safer. 80C is no better or worse than 40C for "sticking". Additionally, temperatures well above the approx 50C glass temp of PLA help the bottom several mm stay above the glass temp which means they will flow instead of warp so some people prefer temps above 75C for this purpose and no fan (not me! unless I'm desperate!)

The second type is related to "too much heat". It's not really warping but it looks like it. Typically the bottom layers of your object - maybe bottom 5mm curve inward and then back to normal. It's usually only bad near corners (both convex and concave corners where concave corners push outward).

The problem is actually that the filament doesn't cool fast enough and the lower layer is still too hot when the next layer is placed. PLA comes out like a string and cools rapidly and shrinks a bit and is like a liquid rubber band pulling a bit on the next layer down. If that lower layer is still hot it pulls it inward and "warps" it. This issue is dependent on the size of the part (layer time - large parts cool before the next layer) but in general I found 60C is cool enough.

So why not print always at 40C? Well because I love the additional feature of after I cool the part from 60C to 20C it typically just pops off the bed. 40C to 20C doesn't give me that advantage.

 

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Since 2 weeks I have an UM2.

I do have a lot of problems with warping. Small object, like the Makerbot are ok, but larger object sometime don't even finish because the printhead hits one of the warped corners an pushes the object out of position.

Bed leveling is ok.

I tried the default heated bed at 70C, 50C, with or without glue.

I made a testblock 200 x 200 x 5 mm, 20% fill. It didn't finish because the printhead kicked it of the bed.

I have some pictures of objects I printed.

Also a picture of the testblock. I will post more pictures when I have prints with other temperatures.

 

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