Merge pull request #13 from jmwright/lego_example

Added Lego Brick Example:

CadQuery/Examples/Ex026_Lego_Brick.py

@@ -0,0 +1,53 @@
+# This example is meant to be used from within the CadQuery module of FreeCAD.
+# This script can create any regular rectangular Lego(TM) Brick
+import cadquery
+import Part
+
+#####
+# Inputs
+######
+lbumps = 4        # number of bumps long
+wbumps = 4        # number of bumps wide
+thickness = 3.2   # this is a thin lego
+# thickness = 9.6 # a thick lego
+
+#
+# Lego Brick Constants-- these make a lego brick a lego :)
+#
+pitch = 8.0
+clearance = 0.1
+height = 3.2
+bumpDiam = 4.8
+bumpHeight = 1.8
+
+t = (pitch - (2 * clearance) - bumpDiam) / 2.0
+postDiam = pitch - t  # works out to 6.5
+total_length = lbumps*pitch - 2.0*clearance
+total_width = wbumps*pitch - 2.0*clearance
+
+# make the base
+s = cadquery.Workplane("XY").box(total_length, total_width, height)
+
+# shell inwards not outwards
+s = s.faces("<Z").shell(-1.0 * t)
+
+# make the bumps on the top
+s = s.faces(">Z").workplane(). \
+    rarray(pitch, pitch, lbumps, wbumps, True).circle(bumpDiam / 2.0) \
+    .extrude(bumpHeight)
+
+# add posts on the bottom. posts are different diameter depending on geometry
+# solid studs for 1 bump, tubes for multiple, none for 1x1
+tmp = s.faces("<Z").workplane(invert=True)
+
+if lbumps > 1 and wbumps > 1:
+    tmp = tmp.rarray(pitch, pitch, lbumps - 1, wbumps - 1, center=True). \
+        circle(postDiam / 2.0).circle(bumpDiam / 2.0).extrude(height - t)
+elif lbumps > 1:
+    tmp = tmp.rarray(pitch, pitch, lbumps - 1, 1, center=True). \
+        circle(t).extrude(height - t)
+elif wbumps > 1:
+    tmp = tmp.rarray(pitch, pitch, 1, wbumps - 1, center=True). \
+        circle(t).extrude(height - t)
+
+Part.show(tmp.toFreecad())