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  1. #1

    what's happening here? stringing?

    hi, i'm trying to print molds for epoxy casting directly from my Ender 3. I'm using OVERTURE Flexible TPU https://www.amazon.com/gp/product/B08BC7X8HQ244336295_185250127055991_7343507225227220290_n.jpgthe outside looks fine but the inside is a stringy mess. nozzle 230, bed 50, speed 50mm/s layer height .16mm . any thought? thanks
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    Last edited by steveh2112; 10-09-2021 at 08:20 AM.

  2. #2
    Super Moderator curious aardvark's Avatar
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    you're printing way way way way too fast and too cold and you've forgotten you have a bowden extruder.
    Try 15mm/s speed and 245c temp
    You can probably go up to 20mm/s
    and 0.2mm layer height.

    And try and keep the model on the right hand side of the bed so you don't have too extreme a bend in the bowden tube.

    Ideally you want to fit a secind z-screw and convert it to a direct drive extruder.

    But as it stands, you need to print really slow and hotter and avoid the left side of the print bed.

    I'm impresssed it's come out as well as it has - must be pretty stiff tpu.

    Yeah it's a stiffer than normal tpu.
    Otherwise you'd just have had a pool of thin spaghetti on the bed :-)

    The 5x faster than normal is just total nonsense.
    They're claiming 150mm/s for tpu ?
    In their dreams.

    I have two direct drive printers both with tpu midified extrduers.
    30mm/s is as fast as I print and I hate printing slow.
    It's just the nature of the material.
    Last edited by curious aardvark; 10-09-2021 at 08:53 AM.

  3. #3
    thanks, i'm trying hotter and slower and on the right now, 3:45 to print, will post, the second Z screw i was thinking about already.

    i see there are 2 options for 2nd Z screw, one mechanical (https://www.amazon.com/BCZAMD-Upgrad.../dp/B086C8LS8N $53) and one with a second stepper (https://www.amazon.com/Gwisdom-Alumi.../dp/B08V88CMZZ $30)

    which would you go with?
    Last edited by steveh2112; 10-09-2021 at 09:49 AM.

  4. #4
    Super Moderator curious aardvark's Avatar
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    the second stepper is technically the better option.
    But the one linked with a belt is a decent option and potentially the easiest to calibrate.

    If you have a bed p;robe and have two seperate z-stepper drivers on the motherboard (I have no clue on the boards creality use) then autowiz's guide to automatically levelling the x-axis is well worth reading.

    I think the boards use one controller but have two z-motor sockets.
    So you have to level the x-axis bar by hand - probably.

    There should be plenty videos on how to do that.

    I'm pretty sure it wouldn't be too hard to make a an adaptor that used the existing extruder and just pop it oon top of the hotend.

    It's what i did with my sapphore pro.

    If you want to spend some money then the biqu H2 lightweight extruder-hotend is a good choice: https://www.amazon.com/BIQU-Extruder...788141&sr=8-11

    Me i like to modify rather than upgrade, so i'd make the existing extruder work :-)

  5. #5
    ok, thanks. however i think the whole printing epoxy mold experiment is a failure because the 3d prints leak like the titanic, so i have to use a lot of filler/primer spray paint to make watertight. the problem then is the epoxy cast parts pick up the primer and looks awful and i'm printing gears and high detail stuff so no easy way to sand it off.

    looks like i'm stuck with printing positives and making rubber molds

    Actually i could try spraying the inside of the mold with metallic bronze paint since that's the final look i'm going for on the finished epoxy parts
    Last edited by steveh2112; 10-09-2021 at 10:48 AM.

  6. #6
    Super Moderator curious aardvark's Avatar
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    well some brands of pla are probably as strong as resin, so you could just print the gears :-) https://www.youtube.com/watch?v=UtRJ4lnNAXY&t=116s Dependign on what you want to use the gears for. Also bear in mind angus did not try polycarbonate, nylon with carbon fibre or rigid polyurethane (ninjatek armadillo). Although with out a hi-temp hotend and enclosed build volume, then you won't be able to us epolycarbonate either.

  7. #7
    Super Moderator curious aardvark's Avatar
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    Also bear in mind that angus did NOT print his gears solid. he had infil. A totally soild slab of gear would be a lot stronger.

  8. #8
    Quote Originally Posted by curious aardvark View Post
    well some brands of pla are probably as strong as resin, so you could just print the gears :-) https://www.youtube.com/watch?v=UtRJ4lnNAXY&t=116s Dependign on what you want to use the gears for. Also bear in mind angus did not try polycarbonate, nylon with carbon fibre or rigid polyurethane (ninjatek armadillo). Although with out a hi-temp hotend and enclosed build volume, then you won't be able to us epolycarbonate either.
    its not so much about strength although that is important, its the look, have to look like real cast brass gears and other parts. i'm using brass power epoxy mix now and it looks identical to real brass

  9. #9
    Super Moderator curious aardvark's Avatar
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    So print gear, make silicone mould. use mould for resin.

  10. #10
    Quote Originally Posted by curious aardvark View Post
    So print gear, make silicone mould. use mould for resin.
    yes, that is the standard way. but silicon rubber is messy, expensive and an extra manufacturing step. i'm trying to find a way to print molds directly in flexible PLA since i have hundreds of parts to print and the design is constantly evolving. i just ordered some antique brass spray paint, will try using that to prime/fill the inside of the mold. hopefully will look ok, we'll see

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