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Seeking non-porous FDM filament

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    Seeking non-porous FDM filament

    Part of my current project involves low-pressure compressed air. There are some fittings I have printed which have to hold this compressed air and I find PLA to be less than successful. So much less than successful, in fact, that I would be as well off trying to hold compressed air in fittings made of charcoal. It's just too porous!

    Can someone suggest a filament which will give me non-porous artifacts?

    Thanks

    #2
    Just in case you thought I was joking ...https://1drv.ms/v/s!ArMxdUYEh9fKwACX...TDdwk?e=eKFcIQ

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      #3
      The question here is not the material itself I would say. For me it is just the case that the layers are not welding well between them.

      Have you tried a higher extrusion temperature as well as maybe finer layer and a lower printing speed ? From my thinking this could lead to a better melting of the previous layer and a better bond.

      Just a guess based on what I see and how the part is made by the printer ...

      IMHO

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        #4
        I think you hit the nail on the head NHSA_Rainer!

        My filament supplier suggested using PETG ("Think Coke Bottles!" he said.) I tried that but the result was exactly the same. He also suggested printing at the top of the temperature range for the material and printing at a high extrusion rate. Neither of these made any difference. Just as porous as ever.

        I came to the conclusion that it is the FDM printing process that is the problem. Imagine rope winding onto a winch drum. There will always be spaces between one turn of the rope on the drum and the turns beside, above and below it. I believe it is this sort of space present in an FDM model, a sort of capillary tube, which allows the air to permeate through the printed model - even if you set infill density to 100%,

        My new solution was to print the Dean End quite normally but to give it a coat of oil=based varnish. The result is evident.
        https://1drv.ms/v/s!ArMxdUYEh9fKwAI_...Z1pw7?e=q1teUe
        As you can see there is still some permeation but a second coat of varnish will fix that.

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          #5
          Hi Vagulus,

          I see you like to go the difficult way. Varnish can get brittle and start to crack under pressure after a certain time especially if it is subject to be pressurized and unpressurized again and again, wash, rinse, repeat ...

          In your latest video if I look at the size of your layers I would say they are HUGE ... looking at the thread pitch of the coupler and the thread pitch of your print and comparing them ...

          May I ask you pinter settings like layer height for example ?

          Imagine rope winding onto a winch drum
          Yes and now imagine winding a fine thread onto a drum. OK, you will need more time. Another thing is extruded material temperature, speed as well as fan speed eg how fast do you cool the molten plastic into solid plastic. Give the molten plastic time to melt the previous layer and so bond better onto the previous layer.

          OK, if you are in a hurry and need your parts quick then all my suggestions are not valid

          regards

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            #6
            I am using 0.8mm nozzles, layer height is 0.64mm and extrusion width 0.9. Surface finish is not critical since I am prototyping mechanical things and I usually just need a bit that does the job. Yes, the quicker the better.

            This thing doesn't have to last for ever so varnish does the job quite nicely.

            I hadn't thought of turning down/off the fans and I guess playing around with that and extrusion height, width, speed et al. would produce a model with the strings of filament better fused together. Whether or not you could ever get rid of the gaps at the side and above and below the extruded string (as in the winch drum effect) I do not know.

            If someone does some experimenting with that please post it here. I would like to know.

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