use exact positioning GCode (G61)

git-svn-id: https://pycam.svn.sourceforge.net/svnroot/pycam/trunk@598 bbaffbd6-741e-11dd-a85d-61de82d9cad9

Changelog

@@ -20,6 +20,7 @@ Version 0.3.0 - UNRELEASED
  * fixed performance issue when using a support grid
  * fixed empty toolpath after transforming the model
  * fixed various minor bugs of the toolpath generator
+ * fixed rounded corners (see GCode G61)
 
 Version 0.2.5 - 2010-06-10
  * added support bridges for holding the object during cutting

src/pycam/Exporters/SimpleGCodeExporter.py

@@ -55,6 +55,8 @@ class SimpleGCodeExporter:
         self.destination.write(self.gcode.begin() + "\n")
         self.destination.write("F" + str(feedrate) + "\n")
         self.destination.write("S" + str(speed) + "\n")
+        # enable "exact path" mode (prefer accuracy over speed)
+        self.destination.write(self.gcode.exactpath())
         self.destination.write(self.gcode.safety() + "\n")
 
     def close(self):

src/pycam/Exporters/gcode.py

@@ -29,7 +29,14 @@ class gcode:
         self.lastz = self.safetyheight
 
     def begin(self):
-        # no x/y positioning - just go up to safety height
+        """
+        G40: disable tool radius compensation
+        G49: disable tool length compensation
+        G54: select coordinate system 1
+        G80: cancel model motion
+        G90: use absolute coordinates instead of axis increments
+        G00 Z?: no x/y positioning - just go up to safety height
+        """
         return "G40 G49 G54 G80 G90\n" \
                 + "G04 P3 T%d M6\n" % self.tool_id \
                 + "G00 Z%.4f\n" % self.safetyheight