Siemens CNC Milling | SPOS | Spindle Positioning

In this article, we describe how to use SPOS code for spindle positioning in Siemens CNC controlled milling (machine centre) machines with all details and examples.


SPOS Introduction

With the function SPOS= you can position the spindle in a specific angular position. The spindle is held in the position through position control.

The speed of the positioning procedure is defined in machine data.


The spindle must be technically designed for position control.

With SPOS=value from the M3/M4 movement, the respective direction of rotation is maintained until the end of the positioning. When positioning from standstill, the position is approached via the shortest path. The direction results from the respective start and end position.


First movement of the spindle, i.e. if the measuring system is not yet synchronized. In this case, the direction is specified in machine data.

Other movement specifications for the spindle are possible with SPOS=ACP(…), SPOS=ACN(…), … as for rotary axes.

The spindle movement takes place parallel to any other axis movements in the same block. This block is ended when both movements are finished.

You may be interested also:
“CNC | M03-M04-S Command | Spindle Speed”

SPOS Format

SPOS=… ; Absolute position: 0 … <360 degrees
SPOS=ACP(…) ; Absolute dimensions, approach position in positive direction
SPOS=ACN(…) ; Absolute dimensions, approach position in negative direction
SPOS=IC(…) ; Incremental dimensions, leading sign determines the traversal direction
SPOS=DC(…) ; Absolute dimensions, approach position directly (on the shortest path)

SPOS Example

N10 SPOS=14.3 ; Spindle position 14.3 degrees
N80 G0 X89 Z300 SPOS=25.6 ; Positioning spindle with axis movements ; This block is ended when all movements have finished
N81 X200 Z300 ; The N81 block only begins once the spindle position from N80 is reached.

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