Update for gravity casting.

- cw.py: added inlets and air escapes for gravity casting
- README: documented the tool making workflow

README

@@ -28,3 +28,20 @@ Finally, all elements on the main PCB that are unusually tall are taped
 over, to further reduce the risk of them working their way into the
 counterweight. Right now, the only component where problems are
 considered likely is the buzzer.
+
+
+Workflow
+--------
+
+- analyze geometry, e.g., by viewing ben-bottom-inside-500um
+- define CAD model in cw.py
+- generate in HeeksCAD with "import cw"
+- define Zig-Zag operation
+- generate Python script and run it (takes a while)
+- save NC file
+- convert G-code to gnuplot, with cncmap/g2gp
+- mount piece and determine geometry with millp
+  (from http://svn.openmoko.org/developers/werner/cncmap)
+- define conversion in "doit" script (to do: put in repository)
+- ./doit >job
+- send job with cncmap/spool

cw.py

@@ -25,6 +25,14 @@ z_ceiling = 5.0	# mm
 #
 y_axis = 16.0
 
+off_x = -15+18
+off_y = -46+5
+
+channel_radius = 1	# mm
+inlet_radius = 7
+shaft = 3
+ymax_piece = 50
+
 total_mass = 0
 total_torque = 0
 
@@ -87,6 +95,35 @@ def rect_gnuplot(x0, y0, z0, x1, y1, z1):
     print
 
 
+#
+# add inlets and air escapes for gravitation casting
+#
+
+def channel(sk, x, y, r0, r1):
+    if r0 == r1:
+	cad.cylinder(x, y, 0, r0, ymax_piece-y)
+        obj = cad.getlastobj()
+    else:
+	cad.cylinder(x, y, 0, r0, shaft)
+	cyl = cad.getlastobj()
+	cad.cone(x, y, shaft, r0, r1, ymax_piece-y-shaft)
+	cone = cad.getlastobj()
+	cad.fuse(cyl, cone)
+	obj = cad.getlastobj()
+    cad.rotate(obj, x, y, 0, 1, 0, 0, -math.pi/2)
+    cad.cut(sk, obj)
+    return cad.getlastobj()
+
+
+def inlet(sk, x, y):
+    return channel(sk, x+off_x, y+off_y, channel_radius, inlet_radius)
+    pass
+
+
+def escape(sk, x, y):
+    return channel(sk, x+off_x, y+off_y, channel_radius, channel_radius)
+
+
 #
 # add a rectangle to the CAD model
 #
@@ -185,6 +222,9 @@ else:
 
 make_base()
 
+#
+# for wax model
+#
 #if __name__ !=  "__main__":
 #    sk = do_rect_cad(10, 40, z_ceiling, 110, 70, z_ceiling)
 #    cad.extrude(sk, 3)
@@ -205,6 +245,14 @@ if __name__ !=  "__main__":
     cad.extrude(sk, -10)
     sk = cad.getlastobj()
     cad.cut(sk, group)
+    sk = cad.getlastobj()
+    sk = escape(sk, 15+channel_radius, 69.5)
+    sk = inlet(sk, 34-channel_radius, 69.5)
+    sk = inlet(sk, 89.5+channel_radius, 69)
+    sk = escape(sk, 100-channel_radius, 69)
+    sk = escape(sk, 60.5-channel_radius, 65)
+    sk = escape(sk, 62.5+channel_radius, 65)
+    sk = inlet(sk, 50, 65)
 
 print >>sys.stderr, "total mass =", total_mass, "g"
 print >>sys.stderr, "total torque =", total_torque*1000.0, "mNm"