Best way to draw a funnel

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Best way to draw a funnel

simon_w
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Hello, first-off I'm fairly new to openscad.

I'd like to draw a funnel with a smooth, e.g. arc, transition between the cone and the pipe.  What would be the best way to code this?

Thanks
Simon
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Re: Best way to draw a funnel

laird
That's a little tricky. I guess you could make a donut shape, then a cone tangent to the surface going up, and a cylinder tangent to the surface going down. Do that twice with different sizes by the thickness, and difference them.
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Re: Best way to draw a funnel

MichaelAtOz
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In reply to this post by simon_w
BTW your post is still flagged as "This post has NOT been accepted by the mailing list yet", you may want to check your registration.
Admin - email* me if you need anything, or if I've done something stupid...
* click on my MichaelAtOz label, there is a link to email me.

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Re: Best way to draw a funnel

MichaelAtOz
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In reply to this post by simon_w
I'd have a look at rotate_extrude, generate the shape, then spin it around the axis to complete the funnel.

Simple example with a straight line:

rotate_extrude()
  translate([2,0]) // need to ensure it is all in the X+ quadent, also makes the hole.
    rotate(45)
      square([25,1]);

Then workout a curvey shape; a little harder.
Admin - email* me if you need anything, or if I've done something stupid...
* click on my MichaelAtOz label, there is a link to email me.

Unless specifically shown otherwise above, my contribution is in the Public Domain; to the extent possible under law, I have waived all copyright and related or neighbouring rights to this work.
Obviously inclusion of works of previous authors is not included in the above.
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Re: Best way to draw a funnel

nophead
In reply to this post by simon_w
The best way to get tangents is with hull().

bowl = 50;
bowl_r = 50;
stem = 60;
stem_r = 5;
neck_r = 10;
thickness = 2;

curve_r = 10;

$fa = 5;
$fs = 0.1;
eps = 0.01;

module profile() {
        hull() {
                translate([stem_r, 0])
                        square([thickness, eps]);

                translate([neck_r + curve_r, stem])
                        circle(r = curve_r);
               
                translate([bowl_r, stem + bowl - eps])
                        square([thickness, eps]);
        }
}

rotate_extrude()
        difference() {
                profile();
                translate([thickness, 0])
                        profile();
        }

funnel
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Re: Best way to draw a funnel

simon_w
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Great, thanks for all your replies.  I'll tease apart the instructions to figure out exactly how its working.

I was pretty sure I'd tried to subscribe but didn't get the promised email.  Have tried again.

Cheers
Simon