Star Micronics to Launch SX-38, the CNC Swiss-Type Automatic Lathe

September 5, 2019

～A new high-functioning and large-diameter model with both gang-type and turret type tool posts～

Star Micronics Co., Ltd. has developed SX-38, a new model of Swiss-type automatic lathe (Note 1), capable of machining up to 38 mm diameter, and will launch it worldwide in April 2020 as a successor model of SV-38R, the current high-functioning model for large-diameter machining, focused on the manufacturing industries including medical, automotive, and aviation-related devices.

SX-38 has one 10-stationed turret-type tool post for front-side machining on the front side and one gang-type tool post equipped with the standard 4-axis face-type milling unit with the tool rotary control axis (B-axis) on the rear side. Simultaneous machining on the turret-type and the gang-type tool posts can reduce time for front-side machining. In addition, this machine is equipped with the 8-spindle rear-end working unit with Y-axis control. With optimized separation of front-side and rear-side machining processes, front and back sides of the workpiece can be machined simultaneously so as to reduce the total machining time.

There are two different versions of turret-type tool post specifications. Type A, the quick-change version with the clamp mechanism which enables quick and easy attachment/detachment of the tool unit; and Type B, the version of Star's unique one-position tool driving. With the Type A version, the existing power tool unit can be used. With the Type B version, the one-position tool driving system suppresses excessive vibrations and heat to ensure continuous operation with more stable accuracy.

In addition, this model employs the guide bush switching mechanism to flexibly meet the diversified needs of machining workpieces. This mechanism allows you to switch freely between the guide bush mode for high-precision machining of long workpieces such as motor shafts by working as a material steady rest and the non-guide bush mode (Note 2) for machining short workpieces economically such as nuts by lessening the length of stock waste. The non-guide bush mode utilizes the spindle head slide guideway structure (Note 3) which secures the rigidity of the main spindle by supporting the slide guideway surface close to the machining point to reduce cutting load generated from machining.
This model is designed for improved rigidity of the whole machine.

Furthermore, the arrangement of tool posts mounted on the machine in the tilted state shortened the distances from the machine front side to the spindles and the tool posts. This model is aimed at improved operability and workability for the operator in both mechanical and software aspects, with the swing type control panel enabling machine operation at the optimum position, and a variety of help features including the alarm help function which enables checking of alarm contents on NC screen.

■Features of SX-38

【High Rigidity and Accuracy】

• The 4-axis face-type milling unit with B-axis control mounted on the gang-type tool post has the structure for holding the upper and lower ends. Furthermore, the clamp mechanism is added to the unit to securely hold it.
• The dovetail groove structure of the Y-axis sliding section of the 8-spindle rear-end working unit ensures rigidity of the tool post.
• A hydraulic rotary cylinder enables stable gripping force for main spindle chuck opening and closing.
• The machine is installed with the function of flexibly correcting thermal displacement with high accuracy based on the temperature data obtained from various positions of the machine.

【High Functionalities】

• The 4-axis face type milling unit with B-axis control which enables angle control within the range of -45 and 90 degrees enables slant machining and simultaneous 5-axis processing on both front and rear sides.
• The sub spindle with the spindle motor which has the same power as the main spindle's ensures enhanced machining capability on the rear side.

【Operability and Workability】

• The machine is designed for operability and workability of any portion of the machine, such as the layout of the tool posts, the height of the opening of the cutting chamber, and the mechanism for guide bush switching, and so on, as to enable simplicity of setup and maintenance work.

■ Main Specifications

(1) Max. machining diameter		⌀ 38 mm
(2) Max. headstock stroke		Guide Bush Mode: 320 mm
		Non-guide Bush Mode: 95 mm
(3) Max. main spindle speed		7000 min-1
(4) Main spindle motor		7.5 kW (continuous) / 11 kW (10 min/25 %ED)
(5) Max. sub spindle speed		7000 min-1
(6) Sub spindle motor		7.5 kW (continuous) / 11 kW (10 min/25 %ED)
(7) Gang-type tool post specifications
	tools	4 tools
	Power tool	Front: ER20 x 4 tools Rear: ER16 x 4 tools
	Max. spindle speed	6000 min-1
	Drive motor	2.2 kW (continuous) / 3.0 kW (5 min/30 %ED)
(8) Turret-type tool post specifications
	Tool position	10 stations
	Tool	Max. 2 tools/station (16 mm)
	Sleeve	Max. 3 tools/station
	Power tool	Max. 2 tools/station
	Max. spindle speed	5700 min-1
	Drive motor	2.7 kW (continuous) / 4.0 kW (5 min/30 %ED)
(9) 8-spindle rear-end working unit specifications
	No. of tools	Stationary tool: Max. 8 tools Power tool: Max. 8 tools
	Max. spindle speed	5000 min-1
	Drive motor	1.2 kW (continuous) / 2.2 kW (5 min/30 %ED)
(10) Front machining capability
	Stationary tool	Max. drilling capability: ⌀ 23 mm Max. tapping capability: M16 x P2.0
	Power tool	Max. drilling capability: ⌀ 10 mm Max. tapping capability: M8 x P1.25
(11) Back machining capability
	Stationary tool	Max. drilling capability: ⌀ 23 mm Max. tapping capability: M16 x P2.0
	Power tool	Max. drilling capability: ⌀ 10 mm Max. tapping capability: M8 x P1.25
(12) Machine dimensions (W x D x H)		2955 x 1430 x 1975 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: Non-guide bush type

This is a sliding head-type automatic lathe which is designed based on the Swiss-type automatic lathe with a guide bush dismounted. Without a guide bush, it is not well suited for machining narrow and long parts. If the workpiece is short and does not deflect, however, such material can be handled effectively.

With the Swiss-type automatic lathe, the rear side of a bar material needs to be handled as waste as a portion equivalent to the size of the guide bush structure which functions as a steady rest for the material cannot be machined.
The non-guide bush type reduces the waste to about 1/3 in length compared to the waste made by the guide bush type.

NOTE 3: Spindle sleeve slide guideway structure

This structure has a sliding surface machined according to the outer diameter of the head stock spindle sleeve, which moves while clamping the workpiece. By eliminating the gap between the spindle sleeve and the guideway, the structure supports the cutting load applied to the head stock through the slide guideway and improves the head stock rigidity.