96-8000 207
G CODES
June 1999
G143 5 Axes Tool Length Compensation + Group 08
(This G-code is optional it is only used on the bridge mill and VR-11)
This 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 involve motion of
the part or fixture. An H code is required to select the tool length from the existing length compensation tables.
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 correctly, there must be two rotary axis, 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
axes must be such that the tool is parallel with Z axes motion.
G143 tool length compensation works only with rapid (G00) and feed (G01) motions. No other feed functions
(G02 or G03) or canned cycles (drilling, tapping, etc.) can be used. When G143 is active, a commanded
motion of X,Y, or 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 the motion of A or B causes a
new vector for the tool length. Thus a typical program would use all 5 axes on one block of data.
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. 5AX COMP)
G01 G93 X.01 Y.01 Z.01 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 B-12.32 F200. (LAST MOTION)
G94 F50. (CANCEL G93)
G0 G90 G49 Z0 (RAPID TO ZERO, CANCEL 5 AXS COMP)
X0 Y0
M30
5 Axes Tool Length Compensation is canceled by G49
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