Programming manual.
CNC 8070
ELECTRONIC THREADING AND RIGID TAPPING.
10.
Electronic threading with variable pitch (G34)
·187·
(REF: 1709)
Considerations about execution.
Beginning of threading.
If threading begins in square (sharp) corner, the pitch increase in the first turn will be half
the increment ("K1"/2) and it will be a full increment "K1" in the following turns.
Interrupt execution ([STOP] key or PLC mark _FEEDHOL).
The behavior of the CNC when interrupting a threading ([STOP] key or PLC mark
_FEEDHOL) depends on function G233. See "10.4 Withdraw the axes after interrupting an
electronic threading (G233)." on page 191.
• If G233 is active, when interrupting the thread, the axes withdraw the distance
programmed in that function. If when interrupting the threading the pass is near the end,
the CNC ignores G233 and stops the axes at the end of the pass.
• If G233 is not active, when interrupting the threading the axes stop at the end of the pass.
Spindle home search.
If the spindle has not been homed (referenced), the first G34 will be done automatically when
using the master spindle. If the spindle is the master and it has not been homed, it will issue
a warning.
Feedrate behavior.
The threading feedrate depends on the programmed spindle speed and thread pitch
(Feedrate = Spindle speed x Pitch). The electronic threading is carried out at 100% of the
calculated feedrate and these values cannot be modified from the CNC's operator panel or
via PLC.
Behavior of the spindle speed and of the spindle speed override
If the OEM allows it, (parameter THREADOVR), the user can modify the speed override from
the operator panel and, in that case, the CNC will adapt the feedrate automatically respecting
the thread pitch. In order to be able to modify the override, the feed forward active on the
axes involved in threading must be higher than 90%.
If more than one G34 have been programmed for the same thread, all the threading
operations must start at the same speed; otherwise, the entry point (start) to the thread will
not be the same in all the threads. The CNC permits changing the spindle override during
the thread cutting pass.
If more than one G34 have been programmed for a multi-start (multi-entry) thread, all the
threading operations must start at the same speed; otherwise, the angle between the starts
(entry points) to the thread will not be the same as the one programmed. The CNC permits
changing the spindle override during the thread cutting pass.
Considerations about thread blending.
When working in round corner (G05), the CNC lets blend different threads seamlessly in a
single part. When thread blending, the CNC only takes into consideration the angular position
of the spindle (Q1) in the first thread, after activating G33 or G34. The CNC ignores parameter
Q1until this function is canceled and activated back and it is synchronized when going
through that angle.
Blending a thread of fixed pitch (G33) with a thread of variable pitch (G34).
The starting pitch of the variable thread (G34) must be the same as the pitch of the fixed-
pitch thread (G33). The pitch increment of the variable thread will be half the increment
("K1"/2) in the first turn and a full increment "K1" in the following turns.
G33 Z-40 K2.5
G34 Z-80 K2.5 K1=1
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