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  1. #1

    Trying to print a funnel, bad results

    Hi all, I just got my 1st 3d printer and am not having much success printing.

    I am trying to print a small funnel, and it looks ok from the outside but is all messed up in the inside Please tell me what I'm doing wrong. I made 2 funnels so far, one using slic3r and one using cura. (I got the stl file from thingiverse and did not modify it)

    I also tried printing a gcode file I downloaded from the printer manufacturer's website and that came out pretty good, so that leads me to believe the problem is in the slicing step.

    Here are the settings I just used in cura to print my 2nd funnel:
    layer height 0.1mm
    wall thickness 0.8mm
    wall line count 2
    top/bottom thickness 0.8mm
    top thickness 0.8mm
    top layers 8
    bottom thickness 0.8mm
    bottom layers 8
    infill density 20
    infill pattern grid
    printing temp 180
    speed 40 mm/s
    enable retraction yes
    build plate adhesion type brim
    Attached Images Attached Images

  2. #2
    Student 686 Shooter's Avatar
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    Could be a few things. Are you using supports for the inside the funnel?

  3. #3
    I am not using supports, nor do I know how to use them. I notice there is a "use supports" checkbox in the slicer, do I just click that it and handles the rest or is it more complicated than that?

  4. #4
    yes most likely more complicated than that.. Supports are structures that get 3d printed underneath areas of the print that are not supported.. The plastic can not print in midair gravity prevents that. The slicing software knows where these unsupported areas are and prints pillars of some sort (different in each software) to support the area that is hanging with nothing under it. Once the print is complete these supports get removed with small tools. There are different settings that control how the supports work so it is not just check the box.. 3D printing is not plug and play.. some science some art.. supports are kind of the art part.. knowing when and how much takes trial and error to learn. If you slicer has a preview pane, move the slider so you can watch the print grow then click the add supports and do it again, you should see the supports show up in the preview.. not knowing anything about your slicer I can say for sure but that is how it works in S3D.

  5. #5
    Student 686 Shooter's Avatar
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    In Cura you can click generate support and it will determine where to place them. Give that a try and see how it turns out. You can dive deeper into the support settings as you learn more.

    I learned a lot about 3D printing on YouTube. Makers Muse, The 3D Printing Nerd, Teaching Tech, Dr. Vax, CHEP and other channels are a great resource that I highly recommend. If you know a more experienced printer, their advice can be invaluable as well.

    As airscapes said 3D printing is a lot of trial and error. But don't get frustrated, everyone who 3D prints has been right where you are. If you stick with it, in a short time you will be regularly producing great prints.

  6. #6
    I am using Cura.

    I just tried flipping the funnel vertically so that it prints upside down (mouth side down) and also adjusted the layer height to 0.16mm and wall thickness to 1mm and that resulted in a significantly better print, though still far from perfect.

    I will adjust a few more settings and try again.

    Thanks for the advice.

  7. #7
    Engineer Roberts_Clif's Avatar
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    Not sure where you got this funnel you can either use supports of try printing another funnel/

    I have printed this funnel many times without supports

    https://www.thingiverse.com/thing:22024

    Post where you got your funnel will try to see what can be done to print it.

  8. #8
    This is the funnel I am trying to print: https://www.thingiverse.com/thing:3830412

  9. #9
    Super Moderator curious aardvark's Avatar
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    the problem is obvious :-)

    well it is if you've printed as many funnels as I have lol

    The angle on the funnel part is extremely steep.
    It's verging on the absolute unsupported printability of an fdm machine.

    All you can really do without supports is slow the printspeed right down and increase the print area cooling.
    If it's already on 100% then consider addig a second fan and duct or a better -focussed - duct.

    And of course micro files and sandingblocks/paper are you friend in tidying it up :-)

    You will note that there are NO pictures of an actual printed funnel and no makes listed.

    Looks like someone's designed it, posted it and THEN tried to print it and failed.

    What's it for ? if the exact size and dimensions are not critical, would take a couple minutes to redesign so that it would print a lot more easily.

    failing that I think I've got a full parametric funnel design script for openscad around somewhere. failing that it'll only take me a couple minutes to write one :-)

    so that's what I did lol
    // curious aardvarks funnel generator
    // All measurements are in Millimetres

    $fn=50; // sets 'roundness'. For a hexagonal funnel - set to 6. Octagonal 8 and so on.

    // Adjust values below to make your funnel

    eds=10; // external diameter of the spout
    wt=2; // wall thickness
    md=25; // widest diameter of mouth
    hs=15; // height of spout
    hm=15; // height of mouth

    difference(){
    union() {
    cylinder(d=eds,h=hs);
    translate([0,0,hs]) cylinder(d1=eds, d2=md,h=hm);
    } // end union
    union() {
    cylinder(d=eds-wt*2,h=hs);
    translate([0,0,hs]) cylinder(d1=eds-wt*2, d2=md-wt*2,h=hm);
    } // end union
    } // end diff
    Copy everything in the box and paste it into openscad.

    Adjust measurements, then press f5 for a quick preview and f6 for a fully generated model that you can export as an stl - press f7 - for printing :-)
    (other formats are available)

    The above parameters make a funnel this shape:


    And that folks is why they taught you algebra at school !
    Well in all my life, openscad scripts are the ONLY place I've ever used it.

    Openscad download page: https://www.openscad.org/downloads.html

    Go make some funnels !

    Tips for funnels with very steep overhangs/underhangs
    make the wall thicker.
    Use smaller layer heights - ie: 0.1 rather than 0.2 or 0.3
    make sure your slicer is set to print outlines from the inside to the outside.

    Tip for openscad - when setting wall thickness - remember to multiply by 2 - cos it's got a wall each side.

    I usually print funnels wide side down - that way yopu get the maximum surface area on the printbed.
    Attached Images Attached Images
    Last edited by curious aardvark; 05-20-2020 at 10:43 AM.

  10. #10
    Thanks curious aardvark using your openscad script I printed pretty much a perfect funnel. Being very new to this, I had assumed that either I was screwing up the settings while slicing, or that my printer was too low quality to print a funnel. I guess not everything you find on thingiverse can be trusted.

    My funnel is just very slightly too big in the spout though. In openscad, it clearly shows that the inside of the spout should be 16mm across. But the resulting funnel has a spout that's 17mm across. Is this level of precision not possible with a low quality printer, or am I doing something wrong? I notice in cura there is a setting called "wall thickness" which is set to 0.8mm, is that affecting it some how?funnel.jpg

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