5. FEED FUNCTIONS
Feedrate of linear interpolation (G01), circular interpolation (G02, G03),
etc. are commanded with numbers after the F code.
In cutting feed, the next block is executed so that the feedrate change from
the previous block is minimized.
Two modes of specification are available:
1. Feed per minute (G98)
After F, specify the amount of feed of the tool per minute.
2. Feed per revolution (G99)
After F, specify the amount of feed of the tool per spindle revolution.
Feed per minute
G98 ; G code (group 05) for feed per minute
F_ ; Feedrate command (mm/min or inch/min)
Feed per revolution
G99 ; G code (group 05) for feed per revolution
F_ ; Feedrate command (mm/rev or inch/rev)
Cutting feed is controlled so that the tangential feedrate is always set at
a specified feedrate.
Fig. 5.3 (a) Tangential feedrate (F)
After specifying G98 (in the feed per minute mode), the amount of feed
of the tool per minute is to be directly specified by setting a number after
F. G98 is a modal code. Once a G98 is specified, it is valid until G99 (feed
per revolution) is specified. At power–on, the feed per revolution mode
An override from 0% to 254% (in 1% steps) can be applied to feed per
minute with the switch on the machine operator’s panel. For detailed
information, see the appropriate manual of the machine tool builder.
D Tangential speed
D Feed per minute (G98)