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  • Problems with ABS ( and PLA for that matter!)

    This maybe a newbie problem so please bear with me.

    I have two printers a Qidi Tech and Flashforge Creator pro, (basically the same machine).

    I'm trying to print with ABS, if I use ABS on the Qidi Tech it's fine,an extrude temp of 240 deg, and a bed temp of 55deg seems to produce good prints.

    However if I take the same reel of filament, and use it on the Flashforge with the same settings I get misprints, I've noticed these seem to be caused by the filament not feeding into the nozzle at all times, it seems to jam.

    So first question is;
    Can anyone offer a reason why it should fail to feed all the time on the Creator and not on the Qidi tech ?

    Second problem is that I am trying to print off military vehicles, mainly tanks, but the barrels snap off at the slightest touch, the ABS appear to be very brittle and not have strength I thought it would have, PLA is no better.
    By slightest touch I mean press to hard with a paintbrush and the barrel will break off !

    Any suggestions for cures would be welcome.

  • #2
    I would raise the bed temp to 100c not uf your using simplify3d you coukd print the barrel layers at 100% infill

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    • #3
      Call me a newbie, but I can't see what effect raising the bed temperature will have on the nozzle, and why is it different on each machine ?

      The barrels are a case in point, the only way I can alter the infill on them is to print them separately from the tank hull, that's not a bad idea I will give it a go and see if that improves things.

      Comment


      • #4
        I missread sorry, it could be a temo on the nozzle, the thermistor or thermocouple could be misreading, its not uncommon to get incorrect temps, compare both machines at the same time and see how close to ambiant they are, my bed thermistor is about 10c high so i can adjust but my hotend is about 2c above room temp so i ignore it

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        • #5
          240 is quite high for a standard ABS but not unheard of. I use 220 on my FFCP for ABS prints, 105 on the bed.
          Assuming your temperature readouts are correct, do an extrude test on the FFCP - if it extrudes fine then you know its not your extruder or hot end.
          Failed extrudes come from back pressure (e.g. too close to bed or a blocked nozzle) or from difficultly pulling filament from the spool, or the extruder failing to apply load to a filament. As you've said you've extruded from the same spool on the Qidi it is less likely the FFCP is having difficultly pulling filament from the spool, so take a look at the other 2 first.

          Part strength:
          FFF printed parts (currently) have low inter layer strength (they fail on Z axis easily). Long thin parts (e.g. tank barrels) have large flexure stresses due to applied loads. The two methods for improving part strength therefore are: increase strength along stress bearing plane (change the build orientation, increase infill, post cure parts with vapor smoothing) or reduce flexure stresses (vapor smoothing, modify part geometry, reduce applied load). Note that vapor smoothing is in both as it increases interlayer adhesion through solvent bonding as well as rounding out stress concentration cracks. Maximum improvement will likely be obtained through build orientation.
          Best of luck.

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          • #6
            Originally posted by christian View Post
            240 is quite high for a standard ABS but not unheard of. I use 220 on my FFCP for ABS prints, 105 on the bed.
            Assuming your temperature readouts are correct, do an extrude test on the FFCP - if it extrudes fine then you know its not your extruder or hot end.
            Failed extrudes come from back pressure (e.g. too close to bed or a blocked nozzle) or from difficultly pulling filament from the spool, or the extruder failing to apply load to a filament. As you've said you've extruded from the same spool on the Qidi it is less likely the FFCP is having difficultly pulling filament from the spool, so take a look at the other 2 first.

            Part strength:
            FFF printed parts (currently) have low inter layer strength (they fail on Z axis easily). Long thin parts (e.g. tank barrels) have large flexure stresses due to applied loads. The two methods for improving part strength therefore are: increase strength along stress bearing plane (change the build orientation, increase infill, post cure parts with vapor smoothing) or reduce flexure stresses (vapor smoothing, modify part geometry, reduce applied load). Note that vapor smoothing is in both as it increases interlayer adhesion through solvent bonding as well as rounding out stress concentration cracks. Maximum improvement will likely be obtained through build orientation.
            Best of luck.
            I upped the temp to 240 because the extruded filament on filament loading was getting a "crinkly" effect, that seemed to stop it.

            I have changed the angle at which the print is on the bed on the y axis, giving it abut 10deg of lean, this only seemed to make the barrel more fragile. Increasing the fill seems to have made them a lot stronger now, which I guess is natural !

            What is and how do you "Vapour Smooth"

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            • #7
              Not having checked out the printers but have you cot sufficient cooling on the ptfe tube just befor the hot end?

              Comment


              • #8
                vapour/vapor smoothing is a post processing step to smooth the finish on 3D printed parts made from certain materials. For ABS prints a small amount of acetone is vaporised in a container and the print placed in the container for a short time - the acetone will dissolve the ABS with sharp edges being the first to go. Run a Google search for ABS vapour/vapor smoothing to find out more.

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                • #9
                  Hi Submriner,
                  i'm new in 3d printing but i understant that the thermistor coud be installed in very right position on nozzle or not so right, this could be the reason for that 240 are enought on a 3dprinter and with another you have to set higher temperature.

                  hope this can help you.

                  bye and good luck


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