Thread cutting with endlessly rotating spindle (G33)
Single-start/multi-start threads
When thread cutting with an endlessly rotating spindle (G33), the path motion is synchronised to the zero passage of the spindle rotation. Therefore, the thread can also be cut in several passes in succession. When an offset angle is specified as option, multi-start threads can also be produced.
To achieve a good machining result and to minimise path errors, feedforward control can be selected for the spindle and for path axes.
Programming
Syntax example for ZX plane (longitudinal axis Z, feed axis X): | |
G33 Z.. K.. [ <spindle_name>.OFFSET=.. ] | modal |
G33 | Thread cutting with endlessly rotating spindle. The G33 function is modal. The next motion block with a modal block type (G00, G01, G02, G03, spline, polynomial) deselects thread cutting. |
Z.. | Target point ("thread length”) in [mm, inch] |
K.. | The thread pitch is programmed with active thread cutting in the unit [mm/rev, inch/rev] without a mathematical sign using the address letters I, J and K. They are assigned to the X, Y and Z axes according to DIN 66025. The thread pitch is modal up to program end and should not be zero on when G33 is selected. The feed is not programmed using the F word but results from the spindle speed and the thread pitch. The pitch of longitudinal or tapered threads at an inclination angle less than 45° is specified by the address letter K if the Z axis is the longitudinal turning axis. With facing or tapered threads with a pitch greater than or equal to 45°, the pitch is specified by I if the X axis is used as the face turning axis, and by J if the Y axis is used. The figure below shows examples for specifying thread pitch using the address letters in the Z-X plane. |
<spindle_name>.OFFSET=.. | Thread offset angle in [°] in spindle modulo range. Only required as an option for multi-turn threads. The offset angle is modal up to program end. Spindle name according to P-CHAN-00053. The "=” character is optional. |
Pitch values I, K with longitudinal thread
Pitch values I, K with tapered thread
Programing Example
Thread cutting with endlessly rotating spindle (G33)
G33 Z.. K.. [S.OFFSET=..]
Cutting a longitudinal thread (M70x1.5) with several cuts:
%L longit_thread
N100 G33 Z48 K1.5 ;Cut thread turn
N110 G00 X72 ;Retract and move
N120 Z105 ;to start position
N130 M29 ;Subroutine end
%G33 (thread depth 0.92 mm)
N10 G51 ;Select diameter programming
N15 T1 D1 M03 S400 ;Select tool, start spindle
N20 G00 X72 Z105 ;Approach
N25 G01 X69.54 F1000 ;Position at 1st cutting depth
N30 LL longitudinal thread ;1st thread cut
N35 G01 X69.08 ;Position at 2nd cutting depth
N30 LL longitudinal thread ;2nd thread cut
N35 G01 X68.62 ;Position at 3rd cutting depth
N30 LL longitudinal thread ;3rd thread cut
N35 G01 X68.16 ;Position at final depth
N30 LL longitudinal thread ;4th thread cut
N35 G01 X68.16 ;Reposition at final depth
N30 LL longitudinal thread ;Empty cut
N60 M05 X150 Z200 ;Moving to end position
N65 M30 ;Program end
Cut a 2-turn longitudinal thread (M70x1.5)
%G33_2 (2-turn thread, thread depth 0.92 mm)
N10 G51 ;Select diameter programming
N15 T1 D1 M03 S40 ;Select tool, start spindle
N20 G00 X72 Z105 ;Approach
N25 G01 X68.16 F1000 ;Position at thread depth
N30 G33 Z48 K1.5 ;Cut 1st thread turn
N35 G00 X72 ;Retract and move
N40 Z105 ;to next
N45 G01 X68.16 ;start position
N50 G33 Z48 K1.5 S.OFFSET=180 ;Cut 2nd thread turn at 180°
N55 G00 X72 ;Retract and move
N60 M05 X150 Z200 ;to end position
N65 M30 ;Program end
Cutting a tapered thread
%L tapered thread
N010 G33 Z90 X1 I5.0 ;Cut thread turn (reference I)
; N010 G33 Z90 X1 K5.0 ;Cut thread turn (reference K)
N020 G00 X72 ;Retract and move
N030 Z105 ;to start position
N040 M29 ;Subroutine end
%G33
N050 G00 X0 Y0 Z0
N060 G18
N070 G51 ;Select diameter programming
N080 D1 M03 S1 ;Select tool, start spindle
N090 G00 X105 Z105 ;Start
N100 G01 X100 F1000 ;Position at 1st cutting depth
N110 LL tapered thread ;1st thread cut
N120 M05 X150 Z200 ;Move to end position
N130 M30 ;Program end