scad/chamfer.scad

/// Chamfering OpenSCAD Example
/// Written by Robert Quattlebaum, 2022-12-14
///
/// This example shows a method for adding a chamfer to a certain
/// class of 3D objects where the profile in the Z dimension doesn't
/// change significantly.
///
/// You must specify the size of the chamfer, the height of the child
/// and the Z-offset for the bottom of the object. You can also specify
/// the shape of the chamfer, which can be either "cone", "curve", "curve-in",
/// or "pyramid".
///
/// This process is ultimately slow, but should be faster than using minkowski.

module chamfer(size=2, child_h=5, child_bot=0, shape="curve") {
    chamfer_size=size;
    
    module chamfer_shape() {
		if (shape == "cone") {
            $fn=16;
            cylinder(chamfer_size/2,chamfer_size/2,0);
        } else if (shape == "curve") {
            $fn=4;
            for( y = [0:1/$fn:1]) {
                cylinder(chamfer_size/2*(1-y),chamfer_size/2/cos(180/$fn)*y,0);
            }
        } else if (shape == "curve-in") {
            $fn=16;
            intersection() {
                sphere(chamfer_size/2/cos(180/$fn));
                translate([0,0,chamfer_size/2])
                    cube(chamfer_size, center=true);
            }
        } else if (shape == "pyramid") {
            $fn=4;
            cylinder(chamfer_size/2/cos(180/$fn),chamfer_size/2,0);
        }
    }
    
    module lower_chamfer() {
        minkowski()
        {
            linear_extrude(0.0001) difference() {
                square([1000,1000],center=true);
                projection()children(0);
            }
            chamfer_shape();
        }
    }

    module upper_chamfer() {
		scale([1,1,-1])lower_chamfer()children();
    }
    
    render()difference() {
        children();
        translate([0,0,child_bot])lower_chamfer()children();
        translate([0,0,child_bot+child_h])upper_chamfer()children();
    }
}

/////////////////////////////////////////////////////////////////////////

module my_shape(h=5) {
    translate([0,0,h/2]) {
        difference() {
            cube([50,50,h],center=true);
            cube([20,20,h+1],center=true);
        }
        translate([20,21,0])cylinder(h=h,r=20,center=true);
    }
}


h=5;

chamfer(3, child_h=h, shape="cone")
    my_shape(h);