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 Warped Plastic

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Warped Plastic
« on: Mar 29, 2021, 10:44 PM »
Today I put a coat of filler primer over my helmet, and left it outside for a few hours to dry. When I came back, I saw that the helmet was warped out of shape:



I'm not sure how this happened. It was warm today, but only 75į F. Seems unlikely that the outside temperature would've warped the helmet (PLA plastic, 3-D printed) like that, but I could be wrong.

Right now, I'm trying to figure out how to fix this. My first instinct would be to use a hair dryer, heat the bent part, and bend it back into shape. But any other suggestions, or insight into this matter, would be appreciated.

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Re: Warped Plastic
« Reply #1 on: Mar 29, 2021, 11:00 PM »
PLA can warp at some pretty low temps but 75 does seem too low. Direct sunlight or trapping in heat (like in a car or under a window) can also have a major effect so it's not ambient air temperature alone that does in prints. Your best bet is going to be very gentle application of heat and trying to shape it back but with that much warping I think you might be fighting an uphill battle. In the future you might want to consider fiberglassing the inside of your print if you have enough room for it. Be wary of fiberglass as it is an exothermic reaction and using too much oxidizer can cause the resin to heat up so much it warps the helmet before it cures.

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Bowfanny


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Re: Warped Plastic
« Reply #2 on: Mar 31, 2021, 12:47 AM »
Direct sunlight is good about super heating pla. I lost a couple prints that way.

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Re: Warped Plastic
« Reply #3 on: Apr 03, 2021, 03:59 PM »
I used a hairdryer to heat the affected area, and gently pushed it back into shape. It's definitely not perfect, but I'm also relieved that it wasn't worse:




However, the process caused a crack to form. I'm hoping that perhaps caulking, or more filler primer, can cover that up.

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Celtkhan


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Re: Warped Plastic
« Reply #4 on: Apr 03, 2021, 08:16 PM »
Filler primer wonít hold that. I donít think bondo has the structural integrity, either; youíre going to need to fiberglass it.

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Re: Warped Plastic
« Reply #5 on: Apr 10, 2021, 11:59 AM »
Anyone have any good resources on fiberglassing?

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Bowfanny


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Re: Warped Plastic
« Reply #6 on: Apr 11, 2021, 10:56 PM »
Anyone have any good resources on fiberglassing?
Loads of old Pepakura videos on YouTube that go over the fiberglassing process.

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QMU#084

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Re: Warped Plastic
« Reply #7 on: Apr 12, 2021, 03:17 PM »
Another thing that could help is to melt some filament into the crack, either with a hot knife or a 3d pen, it would mean likely sanding the primer off, but would basically weld the helmet into one piece again.

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Re: Warped Plastic
« Reply #8 on: Apr 17, 2021, 03:25 PM »
That's a good idea. I have a Dremel that I could use to friction weld the crack together, like this: https://www.scorchworks.com/Blog/friction-welding-with-a-dremel-rotary-tool/

What do you think?  Just curious if a Dremel friction weld would work, before I buy a hot knife.

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Bowfanny


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Re: Warped Plastic
« Reply #9 on: Apr 17, 2021, 04:11 PM »
That's a good idea. I have a Dremel that I could use to friction weld the crack together, like this: https://www.scorchworks.com/Blog/friction-welding-with-a-dremel-rotary-tool/

What do you think?  Just curious if a Dremel friction weld would work, before I buy a hot knife.

friction weld would work

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QMU#084

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Re: Warped Plastic
« Reply #10 on: Apr 24, 2021, 11:52 AM »
That's a good idea. I have a Dremel that I could use to friction weld the crack together, like this: https://www.scorchworks.com/Blog/friction-welding-with-a-dremel-rotary-tool/

What do you think?  Just curious if a Dremel friction weld would work, before I buy a hot knife.


Thatís a great idea, once my new ABS armor plates come in, to weld my collar plate to my back plate.

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Re: Warped Plastic
« Reply #11 on: Apr 26, 2021, 01:41 AM »
Your skill levels may well be greater than mine but I'll suggest another option.

Make a small shim and epoxy it on the inside of the bucket behind the crack. That'll stop it from developing any further and give you a scaffold for using the filler of your choice. You could use bondo/P38 though a bitter option for a deep fill like that would be any two part epoxy material like epoxy steel or even milliput.

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Re: Warped Plastic
« Reply #12 on: May 16, 2021, 05:20 PM »
That was a great idea, thanks. Worked like a charm!



Your skill levels may well be greater than mine but I'll suggest another option.

Make a small shim and epoxy it on the inside of the bucket behind the crack. That'll stop it from developing any further and give you a scaffold for using the filler of your choice. You could use bondo/P38 though a bitter option for a deep fill like that would be any two part epoxy material like epoxy steel or even milliput.

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Re: Warped Plastic
« Reply #13 on: May 16, 2021, 05:55 PM »
That's great! I'm glad to have been able to help. Your bucket looks like it's on back on track for a great paint job.

 :8):

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