Professor Yoshimi Takeuchi

Department of Mechanical Engineering

Osaka University, Japan

with Complicated Shape

Abstract

Ultraprecision micromachining is a key technology to realize the fabrication of microparts, microrobots, etc. Until now, etching and lithography based technologies are well known in the microfabrication fields, where such a material as silicon oxide is generally utilized. A large problem of these technologies is the difficulty of producing 3-dimensional shapes with inclined and sculptured surfaces.

Utraprecision mechanical micromachining technology is utilized to meet the requirement, using a diamond cutting tool and an ultraprecision machine tool such as a turning lathe or a milling machine, especially with the multi-axis control machining function. Multi-axis control machine tools are one solution for improving productivity and accuracy, however, it is difficult to actually implement due to the interference between a cutting tool and a workpiece. Thus, the speech presents the current state of multi-axis control ultraprecision machine tools in Japan and a machined example of small workpieces with a complicated shape by making use of multi-axis control machining function.

In order to set a cutting tool at an arbitrary position with an arbitrary attitude, 6 degrees of freedom are required, that is, 3 translational positioning mechanisms, X, Y, and Z, and 3 rotational positioning mechanisms, A, B, and C around each corresponding translational axis. Usually, conventional machine tools consist of 3 translational axes. On the contrary, multi-axis control machine tools stand for machine tools having more than 3 control axes. 5-axis control machine tools, the representative of multi-axis control ones, are usually equipped with 3 translational axes and 2 rotational axes, for example, X, Y, Z, A, and B. The axis C is used as the main spindle to rotate a diamond cutting tool or a workpiece so that high cutting speed can be realized. In case of 6-axis control machining, non-rotational diamond cutting tools are used, which enable the characteristic machining in spite of extremely low cutting speed.

In general, ultraprecision machine tools have the translational positioning accuracy of 1 nm and the rotational one of 0.00001 degree. In Japan, there are currently more than 5 ultraprecision machine tool builders. Ultraprecision machine tools can be classified into several types in terms of driving mechanism of movement axes such as ball-screw, pneumatic/hydrostatic screw or linear drive, and supporting mechanism/bearing such as ball/roller bearing or pneumatic/hydrostatic bearing.

In order to fabricate microparts with complicated shape, advanced CAM systems are essential. Such a CAM system can generate NC data for ultraprecision machine tools, based on 3-D CAD systems. In other words, it is impossible to create microparts with complicated shape without advanced CAM systems.

As a representative of complicated micromachines, there is a miropump useful for water-cooling of heat generation from CPU, fuel-supplying to fuel cells, blood circulation and so on. Let us introduce the machining of an inducer of axial flow type micropump for blood circulation. Then, several machined results by means of our own multi-axis control CAM system for ultraprecision milling are presented.
 

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