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Moisture in Prints

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Posted · Moisture in Prints

I've been making a lot of part out of PETG for my new 3D printer that is on its way. I live in an area with high humidity and I know that PETG has a problem with absorbing moisture. Are these pictures examples of what happens when PETG has to much moisture in it? In the second picture, the outermost wall is being separated from the other walls. It is like stringing but there is no travel at that point. In the first picture, there are gaps in the print where the walls and layers didn't fuse together. I've done flow tests and heat test, so I believe its not one of those. Any ideas?



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    Posted · Moisture in Prints

    I find that when filament gets moist that it acts oddly when extruding into air.  Raise the print head above the bed 100mm and extrude 10mm of filament.  With a .4 nozzle the string that comes out should be near .4mm in diameter.  If it is growing in diameter then there is likely moisture that is turning to steam and causing the extrusion to expand.  I am fortunate that my kitchen oven has a de-hydrator function and I can leave a roll of filament in at 46C for 4 hours and it comes out not perfect but useable again.

    It's hard to see on that print but you may still have some under-extrusion going on.  My philosophy on Flow calibration is to get the E-steps correct, make sure the exact filament diameter is entered into Cura, and then stop right there.  If I see some extrusion problems with a print I tune it on the fly.

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    Posted · Moisture in Prints

    If too moist, under a microscope you can see bubbles in the extruded plastic, due to water forming into steam (=gas), and during printing the plastic is solidifying before the water-vapour had time to condense and being absorbed by the plastic again. So, if the prints have a foamy effect, you could expect too much water-absorption in the filament.


    If you wouldn't have a microscope, sometimes a smartphone camera with close-up lens add-on could be enough for good photos. Or even a simple webcam with close-up lens.


    This is the quality you can achieve with a simple webcam, with a small, old magnifying lens in front of it. This is a standard 5mm LED. Should be good enough to see any bubbles in a print too.testfoto01.thumb.png.44e26ab526df030668bc1023d195cb7e.png


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