FANUC Series 16/18/160/180-Model C Machining Center Operators Manual

PROGRAMMING
B–62764EN/01
4. INTERPOLATION FUNCTIONS
73
Straight threads with a constant lead can be cut. The position coder
mounted on the spindle reads the spindle speed in real–time. The read
spindle speed is converted to the feedrate per minute to feed the tool.
G33 _ F_ ;
P
I
F : Long axis direction lead

Z
X
In general, thread cutting is repeated along the same tool path in rough
cutting through finish cutting for a screw. Since thread cutting starts when
the position coder mounted on the spindle outputs a 1–turn signal,
threading is started at a fixed point and the tool path on the workpiece is
unchanged for repeated thread cutting. Note that the spindle speed must
remain constant from rough cutting through finish cutting. If not,
incorrect thread lead will occur.
In general, the lag of the servo system, etc. will produce somewhat
incorrect leads at the starting and ending points of a thread cut. To
compensate for this, a thread cutting length somewhat longer than
required should be specified.
Table 4.12 (a) lists the ranges for specifying the thread lead.
Table. 4.12 (a) Ranges of lead sizes that can be specified
Least command
increment
Command value range of the lead
0.001 mm F1 to F50000 (0.01 to 500.00mm)
mm
npu
0.0001 mm F1 to F50000 (0.01 to 500.00mm)
0.0001 inch F1 to F99999
(0.0001 to 9.9999inch)
nc
npu
0.00001 inch F1 to F99999
(0.0001 to 9.9999inch)
4.12
THREAD CUTTING
(G33)
Format
Explanations

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