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  1. #1

    Boiling water and pla plastic, and hello from Russia :)

    One day I got this crazy idea to print a thermos using PLA plastic that will not deform and will hold hot coffee or tea. Some time ago I saw a post about a PLA cup that bends and softens when you pour hot drinks into it. Keeping this in mind I decided to design a thermos-like mug with thick walls, basically it’s 2 walls and a little gap between them. My idea was that besides the hot liquid nothing will be pressuring the inner wallsbecause of the air between the walls, the outer walls will not overheat and bend. So, first of all I modelled a thermos-cup and this is how it was done.



    It consists of two parts: cup and thermos twisted together. I created it in https://www.selfcad.com . it was fast and pretty easy. Then I printed the cup with my createbot mini 3D printer, using organic pla plastic best filament (it was important for me that it doesn’t have dye). Also I used cureslicer.
    Printing details:
    0.4 mm nozzle;
    0.2 mm layer;
    1.6 mm wall thickness;
    20% fill.
    Printing took 16 hours so on the next day I tested the cup and poured boiling water into it. Outer walls heated up after 10 minutes, but not enough for the cup to soften. The bottom though heated up faster and became a little soft. By that time the drink cooled down though.
    Turned out I made a mistake while modeling the cup using a wrong thread, so I had to reprint the model. And this is when the real fun begins. I still don’t know what the issue was - the printer or the plastic, maybe both, but plastic got squeezed very badly.



    Maybe it was because the plastic was old. Anyways, now the cup started leaking because of the cracks between layers and fill lines. I decided to dry the coil and to drill the teflon tube a little in hot end. After doing this I had one more small problem: distance between some lines in horizontal plane, on the bottom to be more specific is too big. This was causing the bottom to leak. Coffee helped me to find those places


    This time I used SelfCAD’s built-in slicerbecause I know for sure there is an option to change the distance (top/bottom linewidth).




    After this I printed the thermos, I had to manually improve the thread (took about 10 minutes) and here is the result. Btw, I created the thread’s using SelfCad nut/screw modifiers




    And a few links:
    SelfCad - https://www.selfcad.com
    Youtube channel- https://www.youtube.com/selfcad
    Live-action recording video https://goo.gl/zq5kru
    Thermos model on Thingiverse - http://www.thingiverse.com/thing:2275179
    Last edited by smartly21; 05-05-2017 at 11:24 AM.

  2. #2
    Engineer ralphzoontjens's Avatar
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    Nov 2013
    Location
    Tilburg, the Netherlands
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    PP filament will be a better choice as it has a much higher glass transitioning point and is dishwasher-proof.
    I use XTC3D on the outside to waterproof things.
    Nice project!

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