GNAL/spiral/spiral_1.scad

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D=300; // start diameter
N=1; // number of spirals
FN=100;
$fn=FN;
H = 2.1;
/**
* Render all spiral facets for as many rotations as supplied
*/
module spiral (START_D = 50, SPIRALS = 39) {
//STOP_D = 100;
SPACING = 0.86;//1.34;
TOP_T = 0.86; //thickness
BOTTOM_T = 1.4;
START_R = START_D / 2;
union () {
for (i = [0 : $fn]) {
rotate ([0, 0, i * (360 / $fn)]) {
for (x = [0: (SPIRALS - 1)]) {
spiral_facet(i, x, START_R, SPACING, BOTTOM_T, TOP_T, H);
}
}
}
}
}
/**
* Generates a single face of the spiral, in this case a trapazoidal
* shape. Issues are (1) performance (maybe use of hull()) and (2) all
2020-05-27 13:52:15 +00:00
* facet counts are the same, despite the diameter. This means that
* there are excessive numbers of facets for the smaller spirals to
* compensate for the number of facets needed for the outer spiral.
*/
module spiral_facet (i, x, START_R, SPACING, BOTTOM_T, TOP_T, H) {
STEP_SIZE = ((SPACING + BOTTOM_T) / $fn);
STEP_OFFSET = i * STEP_SIZE;
SPIRAL_START_OFFSET = (x * (SPACING + BOTTOM_T));
ACTUAL_R = START_R + SPIRAL_START_OFFSET + STEP_OFFSET;
L = 2 * (ACTUAL_R * tan((360 / $fn) / 2));
ANGLE = -atan( STEP_SIZE / (L / 2) ) / 2;
OFFSET = START_R - (BOTTOM_T / 2) + SPIRAL_START_OFFSET + STEP_OFFSET;
translate ([OFFSET, 0, - H / 2]) {
rotate ([0, 0, ANGLE]) {
//replace hull for quick render?
//test spiral lib
hull () {
translate([0, 0, H])
cube([TOP_T, L, 0.1], center=true);
cube([BOTTOM_T, L, 0.1], center=true);
}
}
}
}
spiral(D, N);