Internal/concave Path Tool Radius Compensation Example G41/G42
Internal/concave paths must not be angled as it is impossible for a round tool to follow such a path without gouging. Instead arcs must be used with a radius larger than the tool radius. Here is a GCode Example showing a possible internal path and the resulting tool center path with tool radius compensation turned on.
Note a carefully chosen entry move with a convex corner must be made to avoid gouging the path.
The G Code:
( Tool Table should contain: )
( Slot 1 Length 0.000 Diam 0.500 )
G49 G40 G54
G20 (inches mode)
G0 x1y0z0 (Path with no compensation)
G41 D1 (Tool #1 Radius comp Left of contour)
Fanuc vs EMC/NIST Radius Compensation Entry Move Styles
A new Fanuc Style Radius Compensation Entry Move has been added. To Select which type of Entry move should be performed add a setting to the GCode Interpreter Settings file as shown below. KMotionCNC specifies the GCode Interpreter Settings File to be used in the Tool Setup | Setup Files section. The first value after comp_entry_style will be the selected type.
comp_entry_style FANUC_COMP_ENTRY_STYLE EMC_COMP_ENTRY_STYLE
The Original EMC Entry Style type performed an immediate movement to a tangent point as shown below:
The New Fanuc TYPE A Entry Style delays movement of the entry move until a successive line or arc is specified. It then performs the entry move to a position tangent to the beginning of the successive line or arc. No gouging warnings or errors are generated. The system assumes it is proper to move to the tangent point. Only Type A is currently supported.
This GCode utilizes the Fanuc Entry style to perform a tight helix bore. The code was designed for a nominal tool diameter of 0.194 inches
(T1 D=0.194 CR=0. - ZMIN=-0.2 - flat end mill)
G90 G94 G17 G40
G53 G0 Z0.
G0 X0.563 Y0.
G43 Z0.18 H1
G1 Z0.1 F10.
G41 X0.5285 Y0.122 D1
G3 X0.4065 Y0. I0. J-0.122
X0.4071 Y0.0136 Z-0.0479 I0.1565 J0.
X0.7194 Y-0.0068 Z-0.124 I0.1559 J-0.0136
X0.4065 Y0. Z-0.2 I-0.1564 J0.0068
X0.7195 I0.1565 J0.
X0.4065 I-0.1565 J0.
X0.5285 Y-0.122 I0.122 J0.
G1 G40 X0.563 Y0.
G53 G0 Z0.
G53 X0. Y0.
Here is a Plot of the result:
Orthogonal Top View