Merge pull request #14 from CadQuery/thread

Add Thread.py

Author: adam-urbanczyk

README.md

@@ -59,7 +59,11 @@ A place to share CadQuery scripts, modules, tutorials and projects
 
 * [Involute_Gear.py](examples/Involute_Gear.py) - Fast involute gear generator.
 
-    <img src="examples/images/Involute_Gear.png" width="600"/>
+    <img src="examples/images/Involute_Gear.png" width="600"/>   
+  
+* [Thread.py](examples/Thread.py) - Thread example.
+
+    <img src="examples/images/Thread.png" width="600"/>
 
 ### Tutorials
 

examples/Thread.py

@@ -0,0 +1,64 @@
+from cadquery import *
+from math import *
+
+def helix(r0,r_eps,p,h,d=0,frac=1e-1):
+    
+    def func(t):
+        
+        if t>frac and t<1-frac:
+            z = h*t + d
+            r = r0+r_eps
+        elif t<=frac:
+            z = h*t + d*sin(pi/2 *t/frac)
+            r = r0 + r_eps*sin(pi/2 *t/frac)
+        else:
+            z = h*t - d*sin(2*pi - pi/2*(1-t)/frac)
+            r = r0 - r_eps*sin(2*pi - pi/2*(1-t)/frac)
+            
+        x = r*sin(-2*pi/(p/h)*t)
+        y = r*cos(2*pi/(p/h)*t)
+        
+        return x,y,z
+    
+    return func
+
+def thread(radius, pitch, height, d, radius_eps, aspect= 10):
+    
+    e1_bottom = (cq.Workplane("XY")
+        .parametricCurve(helix(radius,0,pitch,height,-d)).val()
+    )
+    e1_top = (cq.Workplane("XY")
+        .parametricCurve(helix(radius,0,pitch,height,d)).val()
+    )
+    
+    e2_bottom = (cq.Workplane("XY")
+        .parametricCurve(helix(radius,radius_eps,pitch,height,-d/aspect)).val()
+    )
+    e2_top = (cq.Workplane("XY")
+        .parametricCurve(helix(radius,radius_eps,pitch,height,d/aspect)).val()
+    )
+    
+    f1 = Face.makeRuledSurface(e1_bottom, e1_top)
+    f2 = Face.makeRuledSurface(e2_bottom, e2_top)
+    f3 = Face.makeRuledSurface(e1_bottom, e2_bottom)
+    f4 = Face.makeRuledSurface(e1_top, e2_top)
+    
+    sh = Shell.makeShell([f1,f2,f3,f4])
+    rv = Solid.makeSolid(sh)
+    
+    return rv
+
+radius = 4
+pitch = 2
+height = 4
+d = pitch/4
+radius_eps = 0.5
+eps=1e-3
+
+core = cq.Workplane("XY",origin=(0,0,-d)).circle(4).circle(3).extrude(height+1.75*d)
+th1 = thread(radius-eps,pitch,height,d,radius_eps)
+th2  =thread(radius-1+eps,pitch,height,d,-radius_eps)
+
+res = core.union(Compound.makeCompound([th1,th2]))
+
+show_object(res)