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Problem with PETG single layer shell

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  • Problem with PETG single layer shell

    Hello I am currently working on an high performance 1.8m rc plane. To reduce its weight i need to print it with only one outer layer and 10% infill
    I am using petg.
    as you see in the picture, there are quiet big holes in the shell after corners. And I can't deal with them. My best solution was to reduce the printing heat from 250c - 225c that solved around 60% of the holes.

    Printing settings

    Print rite diy printer
    cura
    225c
    0.4 extruder, with 1.75 petg filament
    30mm/s shell sped
    40mm/s infill
    2.5 layer hight
    1.2mm retraction
    and 1mm/s speed
    bed on 90c
    no direct fans

    if someone got a nice Idee =D
    greetings Olgidos
    Attached Files

  • #2
    With PETG, you'll need to increase your top layers to at least 3, perhaps as many as 6 layers. Or increase your infill. Co-polyesters are known to do this, it's challenging to get perfect print settings, especially with some brands like ColorFabb-XT. ColorFabb NGEN is easier to print. Other generic PETs are a mixed bag. You can lower your temp and turn your fan to max to try to improve the bridging performance. But if you lower your temp too much, you'll risk a nozzle jam and reduce the layer adhesion bond strength. Also, having a direct drive vs. Bowden tube is helpful.

    Good luck

    Comment


    • #3
      Thx for your answer. But it isn't possible to increase layer count. Because every gram in the wing counts =)
      can you recommend an other filament, which gives better results in one layer shells. But still is this durable and heat resistant?

      i got a direct drive. I managed to get a better shell by first printing the infill and the shell after ... its better but still not perfect so the inside is a bit more messed up
      Last edited by Olgidos; 12-20-2016, 05:03 PM.

      Comment


      • #4
        better choice is to print internal ribs and cross members like a balsa wood model then cover the wing with heat shrink stuff they use printing anything less than 1 mm will be messy

        Comment


        • #5
          You could try ABS, it has very similar mechanical properties to PETG including durability and heat resistance. ABS does bridge better than PET, although it still won't be perfect doing a single layer with low infill. A rigid material like PLA can do this, but won't provide the durability you seek.

          If your hotend can go to 300C or higher, PC (Polycarbonate) would be an even better choice than ABS or PET. It has much higher strength and heat resistance. But PC can be very hard to print due to it's extreme shrinkage/warpage. If you go this route, you'll ideally want to fully enclose your printer and at minimum use some Airwolf3D Wolfbite Mega to keep your parts planted. Also printing with a large brim or raft helps.

          The most durable material is Nylon, but also very difficult to print due to it's low surface energy which basically means it's like trying to print Teflon - it won't stick to anything other than itself. In order to print it, you'll need either a phenolic sheet (Garolite), perforated build plate, or use Airwolf3D Wolfbite Nitro to get it to stick. It will peel right off most other print surfaces, including BuildTak. I've not tried printing single layer Nylon, so not sure how it would perform. The most popular Nylon at present is Taulman3D's Alloy 910.

          Lastly you might consider hybrid or infused materials (aka composite, blended, etc.) with glass or carbon fiber fill. For RC planes, drones, robots, etc., the most promising material I've seen is CF-Nylon (carbon fiber filled Nylon). This promises the durability of Nylon with added stiffness and strength from a roughly 20% CF fill. With the CF fill, it should improve bridging performance. I recently got a spool of this, but have yet to test it. You can try the NylonX from MatterHackers or CarbonX from 3DXTech. You could also get some CF-PETG or CF-ABS as well, but if you're going to spend the money may as well get the nylon. To print any of these materials you'll need a hardened or coated nozzle as the fibers will wear out a standard brass nozzle rather quickly.

          Both PC and the CF-filled filaments are considerably more expensive than your typical PLA/ABS/PET rolls, so it will partly depend on how much you're willing to spend on this endeavor.

          Hmm, Roger's idea is interesting (print the internal structure and cover that in another material). But of course at that point, why 3D print any of it? Use balsa wood and an X-Acto blade, or get sheet plastic and use a laser cutter since all the pieces could be made flat and assembled together.

          These videos may help, they're fun to watch at least:



          Also see link below to filament strength testing article
          MatterHackers is dedicated to enabling 3D Printing. Check us out at www.matterhackers.com or our Retail Store in Foothill Ranch, CA.

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