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Introducing the Swiss Type Automatic Lathe ST-20

August 6, 2014

- With ø20mm-type Added to 3-Turret Complex Machine Model ST -



Photo:ST-20 Star Micronics is pleased to introduce its new 3-turret complex machine Model ST-20, a new model of the Swiss type automatic lathe (Note 1). This model is designed for complicated shaped parts to be used in the medical, automobile and aircraft industries, and scheduled to be released globally in August, 2014.

Star Micronics introduced the current ST-38; 3-turret type complex machine model in June, 2010. The ST-38 has earned high praise as an excellent automatic lathe for complex machining of large-diameter (up to ø38mm) and complicated parts, mainly in the European and American markets.

The ST-20 can handle workpieces with a maximum machining diameter of ø20mm. There are 12 controlled axes, including 10 linear controlled axes and 2 rotary controlled axes like the ST-38. It has the largest number of controlled axes of all the Swiss type automatic lathes in its class.

The opposing 8-stationed turret type tool post (3-axis control on the front and 2-axis control on the back side) for front-side machining with the guide bush arranged in the center allows turning, drilling and milling simultaneously through the independent control of each tool post.

For back-side machining, an 2-axis controlled 8-stationed turret-type tool post equipped with 2-axis control function is employed. This design achieves a complex machining performance equivalent to that of the front-side machining. Efficient process splitting and simultaneous machining on both the front and back sides enables the reduction of machining time.

In addition, a unique Star Motion Control System (Note 2) is mounted in order to minimize non-cutting time for switching the control system and changing tools to aim at the reduction in the total machining time from the standpoint of the mechanical and control systems.

The alarm help function for checking the details of each alarm on the NC screen, the program check function for checking the contents of the created program before starting machining and many other help functions are employed to improve operator’s operability and workability.





♦ Features of ST-20

[High productivity]

  • Star Motion Control System for reduction of non-cutting time.
  • Simultaneous machining by opposing turret-type tool post for reduction of machining time.
  • The turret-type tool post for back-side machining to achieve simultaneous machining on both the front and back sides.
[High accuracy]
  • Suppressed thermal displacement of the main/sub spindles by spindle cooling unit.
  • Cutting oil cooling unit mounted as standard to suppress the thermal displacement caused by heat generation from rotary tools and temperature rise of cutting oil.
  • Star Motion Control System to achieve smooth axis movement control and restrain machine vibration.
[Machining capability]
  • Turret-type tool post for back-side machining achieves complex machining equally on both the front and back sides.
  • A variety of tool units to be mounted on the turret-type tool post for machining complicated parts.
  • The headstock stroke of 3500mm allows machining of bar materials.



♦ Major Specifications

Max. machining diameter ø20mm
Max. headstock stroke 350mm
Max. main spindle speed 10000 min-1
Main spindle motor  3.7kw / 5.5kw (built-in motor)
Max. sub spindle speed 10000 min-1
Sub spindle motor 3.7kw / 5.5kw (built-in motor)
Tool post specifications Front side 8-stationed turret-type tool post 2 units
Tool Max. 3 tools/station (□12mm)
Sleeve Max. 3 sleeves / station
Power tool Max. 2 tools / station
Max. power tool rotation speed 5750min-1
Power tool motor 2.5kw
Back side 8-stationed turret-type tool post 1 units
Tool Max. 3 tools/station (□12mm)
Sleeve Max. 3 sleeves / station
Power tool Max. 2 tools / station
Max. power tool rotation speed 5750min-1
Power tool motor 2.5kw
Machining capability Stationary tool Max. drilling capability ø14mm
Max. tapping capability M10 × P1.5
Power tool Max. drilling capability ø8mm
Max. tapping capability M6 × P1.0
Machine dimensions (W x D x H) 2988 × 1720 × 1845 mm

NOTE 1: Swiss-type automatic lathe
The Swiss-type automatic lathe was devised as watch component processing machinery in Switzerland in 1870s. Known as a “sliding head-type automatic lathe” as well, it has remarkable characteristics of high-precision cutting of components with longer length compared with the diameter.
In general, if long and narrow parts are processed with a general-purpose lathe, flexure will occur on the workpiece, making finishing with the correct dimensions impossible. The Swiss-type automatic lathe utilizes a guide bush to function as a material steady rest. The tool, positioned at a certain distance from the guide bush, gives a cutting motion only the direction of outside diameter. This allows the workpiece to be cut accurately with no flexure. As for axial motion, the headstock, rather than the tailstock, moves while clamping a workpiece.


NOTE 2: Star Motion Control System
General machining, when NC-controlled, is composed of the following processes:
[Tool selection] → [Approach] → [Cutting] → [Disengagement] → [Next tool selection] → [Approach] → [Next cutting]
In this process, functions other than actual cutting largely affect the machining time. The Star Motion Control System is a function to reduce this non-cutting time.
The Star Motion Control data can be created easily by NC program conversion through “optimization”.
This “optimization” finishes processing related the switching of control systems and completes the processes of [Tool selection] and [Approach] during the process of [Cutting], and the [Disengagement] process of the tool and the next [Cutting] process are controlled to start at the same time. By this control method, the time required for the processes of [Disengagement], [Next tool selection] and [Approach] can be minimized to reduce the non-cutting time.

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