Smithy CNC Mills - Manual (Page 35)

offsets and the one that restores them, make a copy of the parameter file written
by the first program and use it as the parameter file for the
second program.
2.20 G93, G94: Set Feed Rate Mode
Two feed rate modes are recognized: units per minute and inverse time. Program
G94 to start the units per minute mode. Program G93 to start the inverse time
mode.
In units per minute feed rate mode, an F word is interpreted to mean the controlled
point should move at a certain number of inches per minute, millimeters per
minute, or degrees per minute, depending upon what length units are being used
and which axis or axes are moving.
In inverse time feed rate mode, an F word means the move should be completed
in[one divided by the F number] minutes. For example, if the F number is 2.0,
the move should be completed in half a minute.
When the inverse time feed rate mode is active, an F word must appear on every
line which has a G1, G2, or G3 motion, and an F word on a line that does not have
G1, G2, or G3 is ignored. Being in inverse time feed rate mode does not affect G0
(rapid traverse) motions. It is an error if:
* inverse time feed rate mode is active and a line with G1, G2, or G3 (explicitly or
implicitly) does not have an F word.
2.21 G98, G99: Set Canned Cycle Return Level
When the spindle retracts during canned cycles, there is a choice of how far it
retracts: (1) retract perpendicular to the selected plane to the position indicated by
the R word, or (2) retract perpendicular to the selected plane to the position that
axis was in just before the canned cycle started (unless that position is lower than
the position indicated by the R word, in which case use the R word position).
To use option (1), program G99. To use option (2), program G98. Remember that
the R word has different meanings in absolute distance mode and incremental
distance mode.
SmithyCNC Programmer’s Reference Manual:G Codes
SmithyCNC Programmer’s Reference Manual: G-Codes 2-20