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I have an on-going project to build a large lampshade in the shape of a geodesic dome. It's made of 3D printed frames that will be covered with rice paper. I printed the parts in PLA over a month or so, but then had to ship them from Europe to Japan due to moving house.

Unfortunately, when they arrived a lot of them had warped quite badly. In retrospect they weren't packed very well, and they probably got quite hot while travelling through the tropics in a shipping container.

I'm wondering if there is any reasonable way to un-warp parts that have warped in this way. Specifically, if I heat them up again, will they go back to their original shape, or will that just make it worse?

Here's a photo to show what the parts look like. The problem was a lot more obvious before I assembled it, but I didn't think to take a photo - here you can see that some of the edges aren't dead straight, but when they're not clipped to the other parts they're a lot worse. The edge of each triangle is a bit less than 20cm in length.

enter image description here

I'd really appreciate any tips. It'd be a shame if this project ended up not looking perfect after so much printing time.

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PLA stays a thermoplastic in printed shape. And as you saw when unpacking your things, tropical heat and force are enough to get a lasting deformation. Other people had PLA prints ruined from having them sit in the car, I had seen deformation on a purple print I had let sit in the sun on an edge.

This also means that the reverse is true: under load to shape the part and some heat you can try to unbend parts. A hairdryer air of about 60-80 °C, which is more than enough to make PLA formable.

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    $\begingroup$ Thanks - I'd thought of trying that but wasn't sure if I'd just ruin the parts. I'm not sure if I should do it while it's assembled as in the photo, or try and make some kind of jig to get them absolutely straight and at the correct angles. Or maybe just hold them against a flat surface. I'll do some experimenting next weekend. $\endgroup$
    – N. Virgo
    Aug 23, 2020 at 13:31
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    $\begingroup$ @Nathaniel Don't do anything with the assembled parts. Maybe you will deform some of them in other ways untill you get practice with undeforming procedure. And try make this with a jig. When they are hot, probably you will not be able to touch them long enough to straight them. $\endgroup$
    – mguima
    Aug 24, 2020 at 12:43
  • $\begingroup$ @mguima thanks, that's a good point - if I start blasting the whole thing with a hairdryer I could easily just mess it up. I'll think about how to build a jig, and be careful. $\endgroup$
    – N. Virgo
    Aug 24, 2020 at 13:55
  • $\begingroup$ People here have unwarped prints within reason. You just don't want to get so hot the print sags. They would avoid heating areas that weren't warped. $\endgroup$
    – Perry Webb
    Aug 24, 2020 at 15:50
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    $\begingroup$ @nathaniel I'm wondering if you would get better results heating the pieces with warm water 60° , it could allow a more uniform warming of the warped part than a hairdryer...and a pot with water gives better thermal transfer than a blow of hot air just an idea. Good luck! $\endgroup$
    – mguima
    Aug 26, 2020 at 2:41

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