158
CUTTER COMPENSATION
96-8000
June 1999
FIVE A XES C UTTER L ENGTH C OMPENSATION
The Haas control now has the capability for 5 axes cutter length compensation. This capability is most useful
for the VR series of machines with A and B axes motion built into the machine head. It allows the user to
correct for variations in the length of cutting tools without the need to revert to CAD/CAM or post processing
steps. 5 axes length compensation applies only to machines where all rotary motion is movement of the
cutting tool. It does not apply to machines where any of the rotary axes involves axes motion of the part or
fixture.
Five axes cutter length compensation in the Haas CNC uses G143. An Hnn code is required to select the tool
length from the existing length compensation tables. G143 is modal and is in the group 8 G codes. It is thus
mutualy exclusive with G43, G44 and G49. Selecting G49 or H00 will cancel 5 axes compensation. If only
normal (Z axes) cutter length compensation is desired, simply program G43 or G44. For G143 to work cor-
rectly, there must be two rotary axes, A and B. G90 must be active for absolute positioning mode and G91
must not be used. Work position 0,0 for the A and B axis must be such that the tool is parallel with Z axes
motion.
When G 143 is active, and commanded motion of X,Yor Z will have a vector component of the tool length added
to the motion according to the work coordinates of the A and B axes. For a positive length of the tool, this will
move Z upward or in the + direction. If one of X, Y or Z is not programmed, there will be no motion of that axes,
even if motion of A or B cause a new vector for tool length. Thus a typical program would use all 5 axes on one
block of data. If G91, incremental, is used, positioning results are incorrect.
Feed rate in G143 is complicated by the vector offset added to XYZ. Thus inverse feed (G93) is strongly
recommended. If the inverse feed rate was correct before applying G143, it will still be correct with any length of
compensation unless the maximum speed of an axes is exceeded.
An example follows:
T1 M06 ;
G00 G90 G54 X0 Y0 Z0 A0 B0 ;
G143 H01 X0. Y0. Z0. A-20. B-20. (RAPID POSIT W. 5 AX COMP) ;
G01 H01 X0. Y0. Z0. A-19.9 B-19.9 F300. (FEED INV TIME) ;
X0.02 Y0.03 Z0.04 A-19.7 B-19.7 F300. ;
X0.02 Y0.055 Z0.064 A-19.5 B-19.6 F300. ;
X2.345 Y.1234 Z-1.234 A-4.127 B12.32 F200. (LAST MOTION) ;
G94 F50. (CANCEL G93) ;
G0 G90 G49 Z0 (RAPID TO ZERO, CANCEL 5 AXIS COMP) ;
X0 Y0 ;
M30 ;
The following parameters have been added for G143:
Common switch SW 3:
5 AX TOFS -X Set to 1 to negate X Comp. direction
5 AX TOFS -Y Set to 1 to negate Y Comp. direction
5 AX A MOV B Set to 1 if A axis moves B axis
When G143 is active, rotation of the A axes causes length compensation motion of the Y axes and rotation of
the B axes causes length compensation motion of the X axes. The direction of these motions can be reversed
with the above parameters. The B axes normally moves the A axes, but if this is not true, the "A MOV B" bit
can be set to change which is the inner axes.
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