CNC Z32 - Programming guide (Milling machines) 2.13.2 Variable pitch threading (G34, G35) The term “variable pitch threading” indicates a threading whose pitch is not constant, but varies continuously according to a determined variation quantity. The variable pitch threading is programmed through two different G functions: G34 K.. I.. increasing pitch threading G35 K.. I.. decreasing pitch threadingAll descriptions related to the fixed pitch threading (G33) remain valid also for the variable pitch threading (G34 and G35). K = initial threading pitch (mm or inches) This parameter can be programmed in the same block of G34/G35, or in preceding blocks. Warning : if the K parameter is newly programmed in subsequent blocks, when G34/G35 is active, an abrupt pitch variation is encountered. I = pitch increment expressed in mm/round or in/round. This parameter can only be programmed in the same line of G34/G35. The parameter is always positive and assumed as absolute value if programmed as a negative number. In G34 mode, it expresses the increment in mm or inches imposed on pitch K at every round. In G35 mode, it expresses the decrement in mm or inches imposed on pitch K at every round. Warning : if the continuous decrement of K brings to a negative value, the alarm CN1F13 will be issued (in real time). Threading movements with a fixed or variable pitch may be executed in sequence: the threading pitch will continuously vary or remain constant, or it will have a discontinuity, depending on the threading function and parameters programmed. 2.13.3 Rigid tapping (G63) G63 activates a tapping movement composed by: advance with pitch K up to the programmed position on-the-fly spindle inversion return to the starting position. The movement of programmed axes (normally only Z axis) is rigidly connected to that of the spindle for the complete duration of the cycle (one K increment for every spindle turn). Example: ... N10 G0 X0 Y0 Z10 S300 M3 N11 G63 Z-50 G63 K1.25 Z-50 N12 G0 X-10 N13 ... N10 : rapid positioning to hole start position and spindle on. N11 : tapping cycle. It is necessary that the spindle reaches its nominal speed before tapping start. Cycle composition: wait for spindle zero crossing start of Z axis. It is necessary to leave an adequate margin for the axis acceleration, in order to reach complete synchronization while still in air. tapping with a pitch of 1.25 and Z axis synchronized with the spindle up to position Z-50

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