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tuning for unsupported overhangs (worm screw)


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Posted · tuning for unsupported overhangs (worm screw)

I just got my UM2, and am trying out things. I tried to print this worm screw and matching gear: http://www.thingiverse.com/thing:18544

The spiral thread forms a continuous unsupported overhanging edge, which does not print very cleanly for me. You can compare the below image of my actual print (left) and the Cura CAD rendering of the file at right.

Is there any hope for tuning the printer for a better result on this print, or is this geometry just not suitable for this type of printer? (The person who designed it did not even have a printer, it was a CAD modelling excercise). The matching gear, by the way prints beautfully, but of course being printed flat it has almost no overhang.

UM2 with Ultimaker blue PLA, 0.1mm layer, 100% infill, no support, 210 C head, 60 C plate, print speed 40 mm/sec adjusted to 90% speed, fans 100%. Ambient temperature 30 C. Print duration was about 3 1/2 hours.



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    Posted · tuning for unsupported overhangs (worm screw)

    Here is a view of the other part of the gear, which came out well using the same settings, taking about 6 hours to print.





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    Posted · tuning for unsupported overhangs (worm screw)

    Hi jbeale ;)

    :cool: Well you have described it ...

    Below my unprofessional and non-binding opinion:

    - Right, the basic object shown in Cura looks as if it were not for the 3D printing optimized.

    - Some say UM-PLA-blue is no good, try it once with other available material.

    - I was able to make good to very good experience with the following UM-Materials: silver-gray metallic, green, blue semi-transparent, green semi-transparent, Naturel.

    - Your worm-screw looks generally made after insufficient or uneven amount of material. Only the beginning and the end of the spiral should be sharp, but not the coils.

    - Give it a try and use a Little bit more flow.

    - Prints two objects at once, even if you only need one, then the individual layers have more time to cool down.

    - Try sometimes a lower layer thickness, for example 0.06mm, at less than 210 degrees, and 25 to 35 mm / s Speed.

    - If less material per layer used, it rolls up probably less high, especially in combination with the other methods.

    - When printing two identical objects at the same time can cause lint due to the head-trip. But this lint can be removed more easily, as opposed to possible distortions of the objects.

    - Targeted optional object-cooling could also be beneficial.

    - There are ways to print on a cold platform, which could be helpful in complicated overhangs.



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    Posted · tuning for unsupported overhangs (worm screw)

    Try printing it with fresh glue stick and the bed heater turned off.

    PLA will usually stick just fine on a cold glass bed, and there is no point in heating it at the bottom while you are trying to cool it just above the bed.


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    Posted · tuning for unsupported overhangs (worm screw)

    I don't think that the heated bed has a big influence. The lowest surface (close to the bed) looks identical to the upper ones.

    It's simply the nearly horizontal orientation of the surfaces. IMHO you can't get it much better without support or cutting the object into two parts (along the axis).


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    Posted · tuning for unsupported overhangs (worm screw)

    Weird, your printed part looks a lot different to your cad model. I think you should be able to get better results than that. I have printed some threads with quite good success. I would try printing two at the same time and slow the print down a bit. It`s horrible I know, but sometimes we have to be patient :p


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    Posted · tuning for unsupported overhangs (worm screw)

    I have had to test to print this object.

    Without support and in one piece, I can't get better quality than your first photo.

    I have tried different support types (meshmixer, Cura-Lines and Cura-Grid), but the resulting surfaces are always to uggly and the shape doesn't come close to the CAD-file.

    The only good result I can get is by cutting the object in two halfs (along the main axis). And glue them together.

    I have added some support in meshmixer, but I think that was not necessary. Lost some of the support structures during the print.

    PLA- ColorFab "Standard white"

    Temp: 215°

    Bed: 60°

    LayerHight: 0.1mm

    Speed: 50mm/s


    Some comparison with surfaces printed as one piece (Meshmixer support, no support, cura_lines, Cura grid):



    Some more photos in my Album for this test:



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    Posted · tuning for unsupported overhangs (worm screw)

    @Conz: wow, you did a lot of work to try this out; thank you for your efforts on this project! Yes, splitting it in two and printing horizontally definitely gave the best profile.

    I tried printing with full support (and also 0.14 mm layers, because I was impatient) and it took a lot of work to clear out the support structure. The resulting profile was better than without support, but not nearly as good as your horizontal print. Also, it took a lot of work to separate out all the support structure.


    However after mounting it on a drill press and doing a lot of sandpaper work to smooth it down, then running it against the matching gear, it seems usable.


    A few more photos are here: http://umforum.ultimaker.com/index.php?/gallery/album/1043-worm-gear/

    (These are all the same parts, even though the color looks quite different depending on the lighting.)

    And by the way, if anyone just wants a similar gear and doesn't want to print it, you can buy such things as replacement parts for a garage door opener, for example




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    Posted · tuning for unsupported overhangs (worm screw)

    You should throw this one in the Monthly Print Challenge (MPC) and see what people can do with it...


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