Hi All,

I'm trying to create an instruction to use an arbitrary 2D polygon to create
a fillet. It works fairly well when there are no internal angles, but I do
need it to handle internal angles.

If you take a look at the following, it should give an idea what I'm trying
to do and how:

STPS = 10;      //Number of steps to do the fillet over
RADS = 5;      //Radius of the fillet

union() {
translate([-30,-30,0])
cube([60,60,5]);

//This works fine
translate([12,12,5]) {
    ninteyDegFillet(RADS,STPS)
        circle(10);
    translate([0,0,RADS])
        linear_extrude(5)
            circle(10);
}

//This doesn't work quite like I hope (when I have hull turned on in the

fillet module)
translate([-20,-20,5]){
ninteyDegFillet(RADS,STPS)
a_profile();
translate([0,0,RADS])
linear_extrude(5)
a_profile();
}
}

module a_profile(){
difference() {
square(15);
translate([3,3,0])
circle(5);
}
}

module ninteyDegFillet(r,n) {
/*
r - fllet radius
n - number of steps
*/
s = r/n;                    //step size
for(i = [0:s:r]) {
difference() {
//hull() {
translate([0,0,i-s])
linear_extrude(height = s)
offset(r = r-sqrt(pow(r,2) - pow((i-r),2)))
children(0);
translate([0,0,i])
linear_extrude(height = s)
offset(r = r-sqrt(pow(r,2) - pow((i+s-r),2)))
children(0);
}
translate([0,0,-s])
linear_extrude(height = s)
offset(r = r-sqrt(pow(r,2) - pow((-r),2)))
children(0);
//}
}
}

I wanted to use the hull() to smooth things out, but perhaps there's a
better way to do this.

The parameters I would like to be able to do this within is by specifying a
2D profile and a radius.

on another note, is there a way to define 2, 2D profiles offset in some
direction and have them create a top and bottom to a 3D polygon?

Cheers,
Marno

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Hi Marno,

This might help:

$fn=40;
points=[[0,0],[20,0],[20,10],[10,10],[10,20],[0,20]];
polygon(points);
translate([30,0,0]) offset(r=3) offset(delta=-3) polygon(points);
translate([0,30,0]) offset(r=-3) offset(delta=3) polygon(points);
translate([30,30,0]) offset(r=-3) offset(delta=3)
offset(r=3) offset(delta=-3) polygon(points);

Cheers,
Trygon

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Very nice, Nophead.

I guess this could also be accomplished using skin.scad in the
list-comprehension demos:

https://github.com/openscad/list-comprehension-demos

That should be a bit quicker.

-Trygon

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Thanks Nophead,

Very cool; so you are using minkowski to run a truncated cone around a
sliver of each 'profile step'.

I did want to try do this without using minkowski - but unless I or someone
can think of an alternative way (that works well) this is how I'll do it.

-Marno

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Right, I made a transcription error. But oddly my version still spends more
than double the time of yours to render. Besides, the preview of my code is
as lengthy as the render.

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