6. Interpolation Functions
6.7 Thread Cutting
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(6) If the feed hold function is employed during thread cutting to stop the feed, the thread ridges
will lose their shape. For this reason, feed hold does not function during thread cutting.
Note that this is valid from the time the thread cutting command is executed to the time the axis
moves.
If the feed hold switch is pressed during thread cutting, block stop will result at the end point of
the block following the block in which thread cutting is completed (no longer G33 mode).
(7) The converted cutting feedrate is compared with the cutting feed clamp rate when thread
cutting starts, and if it is found to exceed the clamp rate, an operation error will result.
(8) In order to protect the lead during thread cutting, a cutting feed rate which has been converted
may sometimes exceed the cutting feed clamp rate.
(9) An illegal lead is normally produced at the start of the thread and at the end of the cutting
because of servo system delay and other such factors.
Therefore, it is necessary to command a thread length which is determined by adding the
illegal lead lengths to the required thread length.
(10) The spindle speed is subject to the following restriction :
1
≤
R
≤
Maximum feedrate
Thread lead
Where R
≤
Permissible speed of encoder (r/min)
R
: Spindle speed (r/min)
Thread lead
: mm or inches
Maximum feedrate : mm/min or inch/mm (This is subject to the restrictions imposed
by the machine specifications).
(11) When the thread lead is extremely large to the maximum cutting feedrate enough to satisfy
"R<1" in the formula of (10) above, the program error (P93) may occur.
(12) Though dry run is valid for thread cutting, the feed rate based on dry run is not synchronized
with the spindle rotation.
The dry run signal is checked at the start of thread cutting and any switching during thread
cutting is ignored.
(13) Synchronous feed applies for the thread cutting commands even with an asynchronous feed
command (G94).
(14) Spindle override and cutting feed override are invalid and the speeds are fixed to 100% during
thread cutting.
(15) When a thread cutting is commanded during tool radius compensation, the compensation is
temporarily canceled and the thread cutting is executed.
(16) When the mode is switched to another automatic mode while G33 is executed, the following
block which does not contain a thread cutting command is first executed and then the
automatic operation stops.
(17) When the mode is switched to the manual mode while G33 is executed, the following block
which does not contain a thread cutting command is first executed and then the automatic
operation stops.
In the case of a single block, the following block which does not contain a thread cutting
command (when G33 mode is cancelled) is first executed and then the automatic operation
stops.
Note that automatic operation will stop immediately if the mode is switched before the
G33-commanded axis starts moving.
(18) The handle interruption for automatic operation is valid while thread cutting.
(19) The thread cutting start shift angle is not a modal. If there is no Q command with G33, this will
be handled as "Q0".
(20) If a value more than 360.000 is commanded with G33 Q, the program error (P35) will occur.
(21) G33 cuts one row with one cycle. To cut two rows, change the Q value, and issue the same
command.