Smithy CNC Mills - Manual (Page 90)

Material Edge Contour
When the contour is the edge of the material, the outline of the edge is
described in the NC program. For a material edge contour, the value for the
diameter in the tool table is the actual value of the diameter of the tool. The
value in the table must be positive. The NC code for a material edge contour is
the same regardless of the (actual or intended) diameter of the
tool.
Example 1 :
Here is an NC program which cuts material away from the outside of the trian-
gle in figure above. In this example, the cutter compensation radius is the actu-
al radius of the tool in use, which is 0.5, The value for the diameter in the tool
table is twice the radius, which is 1.0.
N0010 G41 G1 X2 Y2 (turn compensation on and make entry move)
N0020 Y-1 (follow right side of triangle)
N0030 X-2 (follow bottom side of triangle)
N0040 X2 Y2 (follow hypotenuse of triangle)
N0050 G40 (turn compensation off)
This will result in the tool following a path consisting of an entry move and the
path shown on the left going clockwise around the triangle. Notice that the
coordinates of the triangle of material appear in the NC code. Notice also that
the tool path includes three arcs which are not explicitly programmed; they are
generated automatically.
Tool Path Contour
When the contour is a tool path contour, the path is described in the NC pro-
gram. It is expected that (except for during the entry moves) the path is intend-
ed to create some part geometry. The path may be generated manually or by a
post-processor, considering the part geometry which is intended to be made. For
the interpreter to work, the tool path must be such that the tool stays in contact
with the edge of the part geometry, as shown on the left side of Figure 7. If a
path of the sort shown on the right of Figure 7 is used, in which the tool does
not stay in contact with the part geometry all the time, the interpreter will
SmithyCNC Programmer’s Reference Manual: Tool File & Compensation
SmithyCNC Programmer’s Reference Manual: Tool File and Compensation 9-8