Thread cutting with endlessly rotating spindle

In the case of thread cutting with an endlessly rotating spindle (G33), the contouring motion is synchronized to the passage of the spindle rotation through zero. Therefore, the thread can also be cut in several, successive passes.

To achieve a good machining result and to minimize contour errors, feed forward control can be selected for the spindle and for the contouring axes.

Programming 

G33 Z.. K..
Thread cutting with endlessly rotating spindle 1:Fig.16: Example of cutting a longitudinal thread with several cuts

Cutting of a longitudinal thread (M70x1.5) with several cuts:

%L Longit_Thread
N100 G33 Z48 K1.5    Cut thread turn
N110 G00 X72    Retraction and move
N120 Z105    to start position
N130 M29    Sub program end

%G33 (thread depth 0.92 mm)
N10 G51    Selection of diameter programming
N15 T1 D1 M03 S400    Tool selection, start spindle
N20 G00 X72 Z105    Approach to starting point

N25 G01 X69.54 F1000    Positioning on 1. cutting depth
N30 LL Longit_Thread    1. cut

N35 G01 X69.08     Positioning on 2. cutting depth
N30 LL Longit_Thread    2. cut

N35 G01 X68.62     Positioning on 3. cutting depth
N30 LL Longit_Thread    3. cut

N35 G01 X68.16     Positioning on end depth
N30 LL Longit_Thread    4. cut

N35 G01 X68.16     Positioning on end depth again
N30 LL Longit_Thread    Empty cut

N60 M05 X150 Z200    Moving to end position
N65 M30    Program end

Cutting of a 2-start longitudinal thread (M70x1.5):

%G33_2 (2-start thread, thread depth 0.92 mm)
N10 G51    Selection of diameter programming
N15 T1 D1 M03 S400    Tool selection, start spindle
N20 G00 X72 Z105    Approach to starting point
N25 G01 X68.16 F1000    Positioning on thread depth
N30 G33 Z48 K1.5    Cut 1. thread turn
N35 G00 X72    Retraction and move
N40 Z105    to next
N45 G01 X68.16    start position
N50 G33 Z48 K1.5 S.OFFSET=180    Cut 2. thread turn at 180°
N55 G00 X72    Retraction and move
N60 M05 X150 Z200    to end position
N65 M30    Program end