CNC Rotary Machining System Reduces Downtime

The three main factors that appeal to users of the Multistar NX-24 rotary machining system from an economical perspective are outstanding productivity, full flexibility and highest precision, the company says. With its number of cycling steps, it almost achieves the productivity of fully mechanical machines. All axes are programmable, which reduces downtime when changing over the machine from one part to the other.

The company’s transfer machine achieves as much as 150 cycle steps per minute and thus can produce as much as 520 parts per minute when equipped with four cycles per machine. The machine is designed for high output, large volume production but, because it is mechanically controlled, change-over can take time. The CNC-controlled rotary machining system increases flexibility significantly with only slight reduction in the output capability. Therefore, it is especially suitable where different types of workpieces must be produced in quantities from a few hundred up to many thousands of parts, within accuracies in the hundredths of a millimeter range. The machine is especially useful for industries such as automotive, watches, medical devices, and climate control systems.

All axis are programmable, and the control unit’s clearly laid out operator interface simplifies rapid programming and quick product changes. However, the machine still has a range of additional unique features, which are attracting considerable attention from specialists in this field.

The system is equipped with 24 workstations and as many as 44 machining units to 60 axes. All axes work simultaneously, which is how the machine achieves its extraordinarily high output. Workpieces are machined completely. Complete machining also includes processes such as deep hole drilling, turning over the workpiece (repositioning/reclamping), in-process measuring and compensation, as well as complete and perfect deburring. This is how the machine produces, for example, 8.5 injection nozzles per minute for the automotive industry.

Because all axes are CNC-programmable, change-over is done mainly by software programming. Compared with machines with mechanical control, this means significant time saving. With different types of workpieces, with maximum diameters of 35 mm and maximum lengths of up to 65 mm, the machining system achieves costs per part, which are economically attractive.

Machining happens simultaneously on the 24 workstations. Each workstation can machine two sides. On one hand, the machine’s compact design means that temperature has less an influence in the machining area. On the other hand, the machine’s sturdy construction guards against the effect of vibrations, the company says. Turning the rotary table through 15 degrees to the next workstation occurs in 0.6 second. Indexing pins then lock the table with an accuracy of ± 2.5 micrometers for the next machining operation. The table can be equipped with different clamping collets.

The workpiece blank is fed to the first workstation and clamped in the collet; the completely machined workpiece is ejected in the last workstation. Hence, there are 22 workstations for the machining operation.

The machine can be equipped with different clamping collets, which can be driven from above or below the table. During machining in the individual stations, the collet is locked by the C-axis spindle or with a mechanical index pin.

Collet drives for turning work at up to 7,500 rpm rotate with a precision of ± 0.005 mm. Turning is possible on workpieces with diameters up to 15 mm. However, collets that are fixed during machining can accept workpieces with diameters up to 35 mm. Collets that are CNC-programmable, which can rotate and interpolate through 360 degrees, can hold workpieces up to 30 mm in diameter. The CNC programmed axis indexes in 0.1 second through 180 degrees and used for four-axis milling.