Init: DNA Double Helix OpenSCAD project.

DNA_Double_Helix/main.scad

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+// Author: Edward Middleton-Smith
+// Project: DNA Double Helix
+// Technology: Main
+// Feature: 
+
+include <modules/constants.scad>;
+use <modules/dna_double_helix.scad>;
+
+DNA_Double_Helix(radius_rotation_helix, radius_strand_helix, angle_twist_total, height, rise, length_discretisation, pi, angle_incline);

DNA_Double_Helix/modules/constants.scad

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+// Author: Edward Middleton-Smith
+// Project: DNA Double Helix
+// Technology: Constants and Variables
+// Feature: 
+
+// constants
+radius_rotation_helix = 80; // radius of helix (displacement of any part of helix from central axis)
+radius_strand_helix = 20;
+angle_twist_total = 1440;
+height = 1300;
+rise = 240; // vertical spacing between base-pair rungs
+length_discretisation = 1; // length_discretisationretisation of points per units length
+pi = 3.14159265359; // rounded
+
+// intermediate variables
+angle_incline = asin(height * 360 / angle_twist_total / 2 / pi / radius_rotation_helix);
+echo("angle_incline: ", angle_incline);

DNA_Double_Helix/modules/dna_double_helix.scad

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+// Author: Edward Middleton-Smith
+// Project: Miscellaneous
+// Technology: DNA Double Helix
+// Feature: Main
+
+include <constants.scad>;
+use <tip_cutting_cube.scad>;
+
+module DNA_Double_Helix(radius_rotation_helix, radius_strand_helix, angle_twist_total, height, rise, length_discretisation, pi, angle_incline) {
+    union() {
+        difference() {
+            union() {
+                linear_extrude(height = height, center = false, convexity = 10, twist = angle_twist_total, slices = height * length_discretisation) translate([radius_rotation_helix, 0, 0]) scale([1, 2, 1]) circle(radius_strand_helix);
+                linear_extrude(height = height, center = false, convexity = 10, twist = angle_twist_total, slices = height * length_discretisation) translate([-radius_rotation_helix, 0, 0]) scale([1, 2, 1]) circle(radius_strand_helix);
+            }
+            
+            // grooves
+            
+        
+            // tip removal - forces faces at ends of helix to be tangential to helix circumference at that point
+            for (index_tip_helix = [1:4]) {
+                rotate([0, 0, -7]) tip_cutting_cube(radius_rotation_helix, radius_strand_helix, index_tip_helix, angle_incline, height, angle_twist_total);
+            }
+        }  
+
+        // knobs - balls at ends of helixes
+        rotate([0, 0, -25]) translate([radius_rotation_helix, radius_strand_helix * (1 - sin(angle_incline)),radius_strand_helix * cos(angle_incline)]) sphere(radius_strand_helix);
+        rotate([0, 0, 155]) translate([radius_rotation_helix, radius_strand_helix * (1 - sin(angle_incline)),radius_strand_helix * cos(angle_incline)]) sphere(radius_strand_helix);
+        rotate([0, 0, 39]) mirror([0, 0, 1]) translate([0, 0, -height]) {
+            rotate([0,0,-25]) translate([radius_rotation_helix, radius_strand_helix * (1 - sin(angle_incline)),radius_strand_helix * cos(angle_incline)]) sphere(radius_strand_helix);
+            rotate([0,0,155]) translate([radius_rotation_helix, radius_strand_helix * (1 - sin(angle_incline)),radius_strand_helix * cos(angle_incline)]) sphere(radius_strand_helix);
+        }
+
+
+        // base-pair rungs
+        for (index_rung = [1 : (height - height % rise) / rise]) {
+            echo("index rung: ", index_rung);
+            position_rung = rise * index_rung / height * angle_twist_total;
+            echo("position rung: ", position_rung);
+            translate([0, 0, rise * index_rung - radius_strand_helix * 3/2]) rotate([-angle_incline, 90, -position_rung]) scale([1/2, 1, 1]) cylinder(2 * radius_rotation_helix, radius_strand_helix, radius_strand_helix, center = true);
+        }
+    }
+}
+
+DNA_Double_Helix(radius_rotation_helix, radius_strand_helix, angle_twist_total, height, rise, length_discretisation, pi, angle_incline);

DNA_Double_Helix/modules/tip_cutting_cube.scad

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+// Author: Edward Middleton-Smith
+// Project: Miscellaneous
+// Technology: DNA Double Helix
+// Feature: Main
+
+include <constants.scad>;
+
+module tip_cutting_cube (radius_rotation_helix, radius_strand_helix, index_tip_helix, angle_incline, height, angle_twist_total) {
+    dx = radius_rotation_helix / 2 + radius_strand_helix * 2;
+    dy = radius_strand_helix * 2 * (1 - cos(angle_incline)); 
+    edge_size = 3 * radius_strand_helix;
+    echo("cutting cube edge size: ", edge_size);
+    requires_rotation_to_alternative_tip_at_end = (index_tip_helix == 1 || index_tip_helix == 4);
+    tip_is_at_top = (index_tip_helix == 3 || index_tip_helix == 4);
+    height_tip_top = height;
+    rotate([0, 0, (requires_rotation_to_alternative_tip_at_end ? 180 : 0) + (tip_is_at_top ? 0 : 0)]) translate([dx, dy, tip_is_at_top ? height_tip_top : 0]) rotate([-angle_incline, 0, 0]) cube(edge_size, center = true);
+}
+
+index_tip_helix = 1; // 1 - 4
+
+tip_cutting_cube(radius_rotation_helix, radius_strand_helix, index_tip_helix, angle_incline, height, angle_twist_total);