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  1. #1
    Student
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    OpenSCAD making complex parts

    I need to make a whole bunch of complex parts that involve complex curves and have been using the hull() command to make them, for an arch, for example I need to use about 50 short hull() segments, otherwise the hull() command fills in the area inside the arch. I need that area not filled in. Anyone have a good idea on doing that? Thinking maybe a module that divides the arch into 50 segments each of identical lengths, but one of you may have a smarter idea

    Thanks in advance.

  2. #2
    Super Moderator curious aardvark's Avatar
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    Jul 2014
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    The simplest way to make an arch is to use the rotate extrude command to create a 180 degree curve and then resize it to get that upward arch.

    resize([20,50,3])rotate_extrude(angle=180,convexity = 10) translate([20, 0, 0]) circle(d = 1);
    A simple one line Arch generator :-)

    Adjust the roundness of the shape by changing '$fn='

    So a simple parametric arch script looks like this:
    // CA's simple arch generator

    $fn=80; // change to adjust roundness of arch ie: numbers between 4&20 make some interesting shapes

    ah=30; // arch height
    aw=40; // arch width
    at=3; //arch thickness
    bt=5; //beam thickness
    bw=50; // adjusts beam width - larger numbers make narrower beams

    resize([aw,ah,at])rotate_extrude(angle=180,convexity = 10) translate([bw, 0, 0]) circle(d = bt);
    Not sure you can do it any simpler. Obviously you'd need to make a slightly smaller arch and difference it to thin the top part down.
    Although you can also do that by adjusting beam thickness and arch thickness.

    But basically that's a pretty versatile one line arch generator :-)

    what other shapes do you need ?
    Last edited by curious aardvark; 10-01-2021 at 03:27 PM.

  3. #3
    Super Moderator curious aardvark's Avatar
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    Throw in an angle adjuster and you can make any curve:-)

    // CA's simple curve and arch generator

    $fn=50; // change to adjust roundness of arch NB: numbers between 4&20 make some interesting shapes

    ca=90; // angle of curve - 180 makes an arch

    ah=30; // arch height
    aw=40; // arch width
    at=3; //arch thickness
    bt=5; //beam thickness
    bw=50; // adjusts beam width - larger numbers make narrower beams

    resize([aw,ah,at])rotate_extrude(angle=ca,convexity = 10) translate([bw, 0,0]) circle(d = bt);
    So to make a smooth arch with a pointed top you could generate a 90 degree curve then mirror it to join two together with a more pointed apex.

    The applications are almost endless.
    Rotate the 90 degree curves around the centre and you'd get a sort of pergola effect.
    I've also rotated the whole thing to sit flat on the usual plane:
    // CA's simple arch and curve generator

    $fn=8; // change to adjust roundness of arch NB: numbers between 4&20 make some interesting shapes

    ca=90; // angle of curve
    ch=0; // curve height adjuster

    ah=60; // arch height
    aw=40; // arch width
    at=3; //arch thickness
    bt=5; //beam thickness
    bw=50; // adjusts beam width - larger numbers make narrower beam

    module curve(){
    resize([aw,ah,at])rotate_extrude(angle=ca,convexity = 10) translate([bw, 0,0]) circle(d = bt);
    } // end mod curve

    nps=10; //number of pergola segments

    module pergola(){
    rotate([90,0,0])for (i = [1:nps]) rotate([0,(360/nps)*i,0]) curve();
    } // end mod pergola

    pergola();


    Add enough pergola sections and you can make interesting 'buildings'.

    Basically it's now a fairly useful little script.
    I know I'll be using it again ;-)

    Oh yeah, a 2 segment pergola is an arch :-)
    So no need to use the curve module.

    Also using 180 curve with the pergola module makes a whole bunch of different shape arches.
    Last edited by curious aardvark; 10-01-2021 at 04:03 PM.

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