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Adding support to TPU structure


printingWhiz

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Posted · Adding support to TPU structure

Hello,

For the past two weeks I have been really struggling with how to add supports to a TPU structure I have. I have been playing around with PVA without any luck and have recently ordered Breakaway as well. The problem with PVA is that the material quality is so bad. I once tried printing the structure with a faster print speed at 25mm/s and the quality of TPU was amazing except that the TPU would stop extruding mid print. So I decreased the print speed to 10 mm/s, but now the printing quality is terrible. I feel like I really don't know what to do other than adding custom supports. For reference, my model is shown below. Any help will be greatly appreciated.

Thanks

image.thumb.png.92e828850207bbecb5c1e5e23d20a135.png

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    Posted · Adding support to TPU structure
    6 hours ago, printingWhiz said:

    Hello,

    For the past two weeks I have been really struggling with how to add supports to a TPU structure I have. I have been playing around with PVA without any luck and have recently ordered Breakaway as well. The problem with PVA is that the material quality is so bad. I once tried printing the structure with a faster print speed at 25mm/s and the quality of TPU was amazing except that the TPU would stop extruding mid print. So I decreased the print speed to 10 mm/s, but now the printing quality is terrible. I feel like I really don't know what to do other than adding custom supports. For reference, my model is shown below. Any help will be greatly appreciated.

    Thanks

    image.thumb.png.92e828850207bbecb5c1e5e23d20a135.png

     

    First of all, is your material (including the TPU!) dry? Make sure it is, because wet TPU will always print with terrible quality.

     

    Also, one suggestion: Have you tried just making the supports out of TPU, using single extrusion? I found the TPU supports quite easy to remove in many cases.

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    Posted · Adding support to TPU structure

    The printing quality of TPU without any support PVA is oftentimes really good so I don't think the TPU is wet. However, I have never tried TPU support. Do I just enable it as a support or design my own custom supports? Additionally, can I use breakaway as a support?

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    Posted · Adding support to TPU structure

    OK, that is good - one source of errors less :)

     

    Just use your TPU extruder for both the model and the supports. You may have to tweak the support settings a bit. I never tried breakaway as support material for TPU, since for my parts TPU supports have been adequate so far.

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    Posted · Adding support to TPU structure

    I was finally able to print it out although it was a little cumbersome to remove the structures. As you said, a little tweaking should get the job done, however. Once again, thank you so much for the help @P3D!

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    Posted · Adding support to TPU structure
    12 hours ago, printingWhiz said:

    I was finally able to print it out although it was a little cumbersome to remove the structures. As you said, a little tweaking should get the job done, however. Once again, thank you so much for the help @P3D!

     

    That's good to hear ☺️

     

    You're very welcome, glad that I could help you on this :)

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    Posted · Adding support to TPU structure

    I usually design custom supports, so that I can make sure that I can get in there with a knife, or get in with pliers and hooks to pull out the support. In custom support I can also increase or decrease clearances as desired.

     

     

    Some of my usual examples, in case you need ideas:

     

    Various support concepts. The ribs (0.5mm wide, 1mm aparat) on top allow tighter clearances.

    support_ideas1.thumb.jpg.01b652b9b15851890834b65181100d91.jpg

     

    Orange and pink are supports: they have extensions so I can grab them with a plier, as the model is too tiny to get in with a knife. The brim is for added bonding, due to the large overhangs (they float above the yellow).

    ostrcp_key_v20_zoom.thumb.jpg.c85991865979ff09557a37d9ca6ad20f.jpg

     

     

    A totally free hanging support: easy to remove, consumes very few material, and does not damage the underlying parts. The inverted staircase at the underside of the support reduces its tendency to curl up, compared to a triangle shape.

    clamp1.thumb.jpg.376227acc930e40f6de8d3919b3f0a7f.jpg

     

     

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    Posted · Adding support to TPU structure

    @geert_2, Thank you for showing this technique!  What clearance do you like between the top of your supports and the part?  It looks like maybe 0.25mm?

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    Posted · Adding support to TPU structure

    That depends a lot on the model, printing speed, material and temperature. It may also depend on your slicer. Smaller models can get away with smaller clearances. But in bigger models, this makes it harder to remove the support. Also, the easier you can get in with tools, the narrower the gap can be.

     

    So it boils down to trial and error: make a testmodel with various clearances that mimicks that part of your real design (like the one shown above with the numbers 0.2, 0.3, 0.4 and 0.5mm), and print that with your desired materials, speeds and temps. But generally, clearance is indeed between 0.2mm and 0.5mm, with 0.3 and 0.4 being most common in my designs.

     

    And it also depends on the functionality: if accuracy does not matter too much, take bigger clearances. If accuracy is important, for example in rulers that have to slide into each other, then tighter gaps are better, but that requires more effort to design and print the model and to remove the supports.

     

    Thus provide enough features in your design to make support-removal possible, so you can get in there with a knife, scalpel (=surgical knife), hook, pliers, or whatever else tool. A massive block of support in a tight area is almost impossible to remove. The better you can get in with tools, the tighter you can make the tolerances. For example to wiggle-out supports with pliers, extend the support to outside of the model to get a good grip with the pliers. It is worth thinking this over very well, and to make several simple concept tests, before doing it in the real model. Especially if the real model is big and complex and takes a lot of time to print, or if you have to print a lot of them.

     

    That extra testing time is very well spent. Keep watching while these test models are printing, and look what happens. That also gives you a lot of insight, especially for the free-hanging supports, because of their tendencies to sag and to curl up at the same time. So you can catch and correct any outpoints immediately at the beginning of the design phase.

     

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