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Nicolinux

PLA Form Memory

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Hi,

I've just discovered an interesting property of PLA. When heated up (to around glass transition temperature) it tends to regain its shape.

I was about to repurpose a ball bearing for Robert's feeder and couldn't get out those small round washers/clips. So I used brute force and put two dents into it:

PLA form memory 1

 

After heating up it looks like this:

PLA form memory 2

PLA form memory 3

Interesting...

EDIT: Using Ultimaker orange PLA

 

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Unrelated but the new yoke does away with those intricate thingies for a simple cylinder if you want to replace it. I too have had trouble sometimes to remove them :p

I can't remember ever seeing something like that though. I wonder if it could be leveraged somehow. Stuffing things into something else and then reheating to regain shape perhaps. Hmm...

 

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I don't suppose it's a coincidence? E.g. when you heat it up it expands and when it cools again it will will find its lowest energy shape. Could that shape be a cylinder? After all when you deformed the original shape I assume that implies deformation stresses.

 

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@Didier I did something similar a while ago. I printed a plane of flex pla and re heated it after to bend it to produce a cylinder that would fit around the cables of the UM2 after having to re solder some loose fan connecter.

I also did the test for dishwasher resistant materials. I tested UM PLA, XT and orbitect ABS. They all bend easily under very hot water but when you bend it back to its normal shape the PLA leave a big mark where it was bent compared to the 2 others... I use XT now for print to be in dishwasher since its "food safe" and BPA free. If its thick enought it wont bend.

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Hey Nico,

Great find! My guess is that by denting the filament you introduced stresses in the material. Polymers tend to exhibit relaxation and heating the PLA above its glass temperature allows the chains to move. If only we could change back entire prints into spools :D

 

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