screws tests

cases/rack/screws.scad

@@ -1,13 +1,113 @@
 
 /* Some common screw dimensions */
-holeRadiusSlack = 0.5;
 
 
+inf = 400; // basically infinity
+
+/********************************************************************************/
+// M3 dimensions
+
+m3HoleRadiusSlack = 0.15;
 m3Diameter = 3.0;
 m3Radius = m3Diameter/2.0;
 
-m3RadiusSlacked = m3Radius + holeRadiusSlack;
+m3RadiusSlacked = m3Radius + m3HoleRadiusSlack;
-
-
 
+// legacy TODO: replace
 m3ptr = m3RadiusSlacked;
+
+// NUTS!
+m3HexNutWidthAcrossFlats = 5.41;
+m3HexNutWidthAcrossCorners = FtoG(m3HexNutWidthAcrossFlats);
+
+m3HexNutThickness = 2.18;
+
+module m3HexNutPocketNegative() {
+  hexNutPocketNegative(m3RadiusSlacked,
+                       m3HexNutWidthAcrossCorners/2 + 0.1,
+                       m3HexNutThickness + 0.2);
+}
+
+
+// TODO: remove test
+
+*difference() {
+  cube(size=[8,12,5], center=true);
+
+  rotate(a=[0,0,20])
+  m3HexNutPocketNegative();
+}
+
+*m3HexNutPocketNegative();
+
+
+/********************************************************************************/
+// M4 dimensions
+
+m4HoleRadiusSlack = 0.15;
+m4Diameter = 4.0;
+m4Radius = m4Diameter/2.0;
+m4RadiusSlacked = m4Radius + m4HoleRadiusSlack;
+
+m4HexNutWidthAcrossFlats = 6.89;
+m4HexNutWidthAcrossCorners = FtoG(m4HexNutWidthAcrossFlats);
+
+m4HexNutThickness = 3.07;
+
+module m4HexNutPocketNegative() {
+  hexNutPocketNegative(m4RadiusSlacked,
+                       m4HexNutWidthAcrossCorners/2 + 0.1,
+                       m4HexNutThickness + 0.2);
+}
+
+
+// TODO: remove test
+
+difference() {
+  translate(v=[0,1,0])
+  cube(size=[10,12,6], center=true);
+
+  rotate(a=[0,0,20])
+  m4HexNutPocketNegative();
+}
+
+*m4HexNutPocketNegative();
+
+/********************************************************************************/
+
+// Convert a regular hexagon widthAcrossFlats to widthAcrossCorners
+function FtoG(widthAcrossFlats) = widthAcrossFlats * (2/sqrt(3));  
+
+// Convert a regular hexagon widthAcrossCorners to widthAcrossFlats
+function GtoF(widthAcrossCorners) =  widthAcrossCorners * (sqrt(3)/2);
+
+
+module hexNutPocketNegative(
+  innerRadius,
+  widthAcrossCorners,
+  thickness)
+{
+
+  union() {
+
+    hull() {
+      // hexagonal cylinder representing where the nut should fit
+      cylinder(r=widthAcrossCorners, h=thickness, center=true, $fn=6);
+
+      // negative volume for sliding in the nut
+      translate(v=[inf,0,0])
+      cylinder(r=widthAcrossCorners, h=thickness, center=true, $fn=6);
+    }
+
+    // negative volume for screw lead
+    translate(v=[0,0,-10])
+    cylinder(r=innerRadius, h = inf, $fn=32);
+
+    hull() {
+     translate(v=[inf,0,0])
+       cylinder(r=innerRadius, h = inf, $fn=32);
+     cylinder(r=innerRadius, h = inf, $fn=32);
+    }
+  }
+}
+