150
FUNCTIONS
96-8000
June 1999
4.6 SPINDLE S PEED F UNCTIONS
SPINDLE S PEED C OMMANDS
Spindle speed functions are controlled primarily by the S address code. The S address specifies RPM in
integer values from 1 to maximum spindle speed (Parameter 131). NOT TO BE CHANGED BY USER!
Speeds from S1 to the Parameter 142 value (usually 1200) will automatically select low gear and speeds above
Parameter 142 will select high gear. Two M codes, M41 and M42 can be used to override the gear selection.
M41 for low gear and M42 for high gear. Low gear operation above S1250 is not recommended. High gear
operation below S100 may lack torque or speed accuracy.
If there is no gear box in your machine (VF-0) the gear box is disabled by parameters, it is always in high gear,
and M41 and M42 commands are ignored.
Three M codes are used to start and stop the spindle. M03 starts the spindle clockwise, M04 starts the spindle
counterclockwise, and M05 stops the spindle.
Note that only one M code is allowed in a block. This means that if you wish to override the gear with M41 or
M42, you must put the Snnnn and M41 (or M42) in one block and the M03 (or M04) in the next block. The
Snnnn should always be in the same block as the M41 or M42 as an unneeded double gear change might
otherwise be performed.
RIGID T APPING C ONTROL O F S PINDLE
Rigid tapping is an option which can be installed on this machine at the factory. It is enabled with the Param-
eter 57 îš“Rigid Tapîš” flag. When installed and enabled, it changes the way G74 and G84 work and a floating tap
holder is not needed for these G codes. In addition, if the îš“REPT RIG TAPîš” flag in Parameter 57 is set, every
repetition of a tapping operation will control the orientation of the spindle so that the tapping is repeatable.
Rigid tapping allows the use of a tap without a floating tap holder. Pitch control is within 0.0005 inch. Bottom
depth control is +/-0.020 inch and repeatability is +/-0.005 inch. Rigid tapping will operate from 100 to 2000
RPM and up to 100 inches per minute feed. Bottom depth control is better at lower speeds. Thread pitch can
be from 5 to 100 TPI.
The pitch of a tapped hole is defined by the ratio between the feed rate and spindle speed. When rigid tapping
is selected, these two must be set exactly. An encoder mounted with the spindle tracks the position of the
spindle and the Z-axis is moved precisely to match the pitch of the thread. If the repeatable option is selected,
a position pulse from the encoder is used to synchronize the starting of the Z motion with the position of the
spindle.
Note that with G74 and G84, you do not ever need to use M03, M04, or M05. These canned cycles start and
stop the spindle automatically. This applies to using normal or rigid tapping.
The rigid tapping option requires additional hardware be added to the spindle head assembly and a different
electronics card put into the control. When this option is installed, the second page of diagnostic data will
show the actual spindle speed. See îš“Tapping with the VF Series CNC Millîš” for more information.
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