High-Precision Machine Division

The USM-20A:  Super-precision is further accelerated.
With the continuous development of higher-speed and higher-density computers, requirements of higher accuracy are ever-increasing in the field of fine-grooving, cutting and grinding of magnetic heads. With the aggregate super-precision machining technologies it has achieved for many years, TOSHIBA MACHINE has accomplished NC high-precision slicer USM-20A that can meet the needs of the times, based on the performance records of our best-seller machine USM-20A. An improved super-precision aerostatic spindle with low heat expansion, low heat generation and low vibration, a high-precision table (X-axis) and a high-precision indexing column (Y-axis) contribute to a remarkable improvement in the yield in machining expensive magnetic materials. Additionally, special measures are taken to keep high total rigidity of the machine including spindle to allow powerful and wide-surface grinding, using a mutli-blade wheel. The machine is also suited for super-precision machining of hard and fragile materials such as fine ceramics. In addition to the existing slicer specifications, this machine is equipped with an image processing unit which, together with a workpiece swivel slide (C-axis) permits automatic alignment. Precision cutting of up to 6-inch diameter workpieces is possible.

                 
model USM-20A  High-precision NC slicing machine


Super-precision grinding:
The wheel spindle incorporates our specially designed cylindrical super-precision aerostatic spin die made of proven special quality material. The workpiece indexing column locates a workpiece accurately by the closed loop system using a linear scale. Additionally, necessary measures against thermal displacement are taken on each machine part to stabalize the repeatability of plus/minus 0.1 um, spindle center runout of 0.2 um or less, spindle elongation of 1 um per 20,000 min-1, and table movement straightness of 0.2 um per 200 mm in a horizontal plane.



  

Maintenance
The aerostatic spindle with less heat generation and vibration has a semi-permanent service life and is maintenance-free. A V-V slide guideway with high accuracy and rigidity is used for the table to assure accurate and smooth table feed. Additionally, a variety of interlocks including an aerostatic spindle protective circuit at air pressure drop are standard-equipped to protect the machine. Spindle bearings made of special material eliminate the runout caused by overload or cut of air.
 
Multi-grinding: Thanks to the highly rigid aerostatic spindle, heavy-duty grinding operation is possible, using a multi-blade wheel. When the wheel spindle diameter is 60 mm, the rigidity is 3.5 kgf/um and 6kgf/um in the radial and thrust directions, respectively. Likewise, when the 40-mm diameter spindle is used, it is 2kgf/um in the radial direction and 4kgf/um in the thrust direction.
 

Auto alignment function:
The auto alignment function including image processing can be selected optionally. Two marks on the workpiece surface input by means of a CCD camera are searched, workpiece inclination is calculated from measured coordinate values, and the C-axis of the swivel slide is rotated to align the two marks in parallel with the X-axis movement.




  

NC system:
The number of controlled axes is four including the basic three axes (X-, Y- and Z-axes) and C-axis, and setting of compensation is easy. The manual and automatic operation modes are available. When neceassary, a desired cycle program can be entered through the MDI keyboard. Also, the machine control unit (MCU) is integrated with the machine body to reduce the floor space and for easy transportation. (NC system: FANUC SYSTEM 18MB)


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