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12.1 Tool Length Offsets

Tool length offsets are given as positive numbers in the tool table. A tool length offset is programmed using G43 Hn, where n is the desired table index. It is expected that all entries in the tool table will be positive. The H number is checked for being a non-negative integer when it is read. The interpreter behaves as follows.

1. If G43 Hn is programmed, A USE_TOOL_LENGTH_OFFSET(length) function call is made (where length is the value of the tool length offset entry in the tool table whose index is n), tool_length_offset is reset in the machine settings model, and the value of current_z in the model is adjusted. Note that n does not have to be the same as the slot number of the tool currently in the spindle.

2. If G49 is programmed, USE_TOOL_LENGTH_OFFSET(0.0) is called, tool_length_offset is reset to 0.0 in the machine settings model, and the value of current_z in the model is adjusted. The effect of tool length compensation is illustrated in the screen shot below. Notice that the length of the tool is subtracted from the z setting so that the tool tip appears at the programmed setting.  You should note that the effect of tool length compensation is immediate when you view the z position as a relative coordinate but it does affect actual machine position until you program a z move.

Test tool length program.

Tool #1 is 1 inch long.

N01 G1 F15 X0 Y0 Z0 
N02 G43 H1 Z0 X1 
N03 G49 X0 Z0 
N04 G0 X2 
N05 G1 G43 H1 G4 P10 Z0 X3 
N06 G49 X2 Z0 
N07 G0 X0



\resizebox*{2in}{!}{\includegraphics{/usr/share/lyx/EMC_images/length1.eps}}




The effect of this is that in most cases the machine will pick up the offset as a ramp during the next xyz move after the g43 word.


next up previous contents index
Next: 12.2 Cutter Radius Compensation Up: 12. Programming Tool Compensation Previous: 12. Programming Tool Compensation   Contents   Index
root 2003-05-26