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Polygon turning is becoming more and more common in high-output series production of flats. One prerequisite for this is suitable turning machines and tools, as well as a CNC control system that supports synchronous spindle coupling.

Polygon turning

Driven tools are being used on turning machines in more and more fields of application. The milling of flats, such as polygonal pins, has even become the state of the art. The only drawback to this process is the time that it takes, making efficient implementation difficult in mass production. For this reason, the use of innovative polygon turning in CNC turning centers is increasing. This is a continual process, similar to conventional turning, which allows users to halve machining time compared with milling. Time savings of up to 90% are possible with materials that are easy to machine.

In polygon turning, even surfaces are generated on the lateral surfaces of rotation-symmetrical workpieces using a cutter

Cutter in sync with the main spindle

In polygon turning, even surfaces - such as parallel flats or polygons (with three to eight sides) - are generated on the lateral surface of rotation-symmetrical workpieces using a cutter. The workpiece (the main spindle) and the rotating tool (the cutter) work in a synchronous coupling relationship, creating even surfaces. The number of surfaces generated depends on the translation relation and the number of cutting edges on the cutting tool. The workpiece and tool rotate in opposite directions. In practice, a translation relation of 2:1 is often used. This means that the cutter turns at double the speed of the workpiece. One cutting edge always works on two opposite surfaces. Accordingly, a tool with two cutting edges is used to turn a square, a tool with three cutting edges is used to turn a hexagon and so on. If the translation relation is different, or if a different number of cutting edges are used, surfaces may be very convex or concave.

The synchronous spindle function should be used in the SINUMERIK to ensure coupled, synchronous operation of the main spindle and tool spindle. One spindle must be defined as the leading spindle and the second as the following spindle. The two spindles work synchronously in terms of position and speed. The coupling must be defined and activated in the program before machining and then deactivated and deleted after machining.

Radial and axial processes

Depending on the workpiece, the radial plunging procedure is used for flats, and the axial longitudinal turning procedure is used for polygons behind a flange. These are programmed using stock removal cycles combined with the contour editor, or in G-code.

Programming example: synchronous spindle



COUPDEF (S2,S1,2,-1,"NOC","DV")



; possible couplings delete
; coupling define
; S1 is the main spindle
; S2 is the driven tool
; Translation relation 2:1
; Portents for treatment direction
; couplings switch on
; … ; now the real treatment occurs
 ; couplings switch off
; coupling delete

Synchronous spindle coupling