Added Z-axis wobble fix

Z-Axis Wobble Fix/z-wobble.scad

+
+diameter_outer_min = 10;
+diameter_outer_max = 12;
+height = 10;
+diameter_inner_min = 2.8;
+diameter_inner_max = 2.8;
+
+$fn = 20;
+
+difference() {
+    cylinder(d1 = diameter_outer_max, d2 = diameter_outer_min, h = height);
+    cylinder(d = diameter_inner_max, d2 = diameter_inner_min, h = height);
+}