Worldwide R&D

Research on Technologies for Utilizing Miniature Device
Tokio Kitahara, Professor, Shonan Institute of Technology, Faculty of Engineering
Shonan Institute of Technology is a university with anengineering faculty (five departments) and a graduate school(three specializations) and approximately 2,500 students. I
am affiliated with the Mechanical Engineering department
and graduate school specialization. My laboratory deals withtechnologies for utilizing miniature mechanisms, which do
not require very large-scale equipment. We conduct researchon the element technologies of microfabrication machines,
high-speed lathing of microparts, micro generators, and thelike. Here, I will describe two of these research projects.

(1) Direct-driven device with built-in actuator
We are studying direct-driven devices driven by friction.
An actuator is integrated in the device for use in
microfabrication equipment. We have verified the usefulnessof these devices in a microlathe, which we developed earlier,and are currently analyzing the device properties in detail.
Fig. 1 shows the basic structure of the device, wherein
two piezoelectric elements intersect a slider. Fig. 2 shows
the results of an experiment for finding the relationshipbetween the surface pressure and velocity of the slider, whilevarying the slider's thrust. From this experiment, wedetermined that thrust decreases the slider velocity, but aSlider(2) High-speed lathing of microparts
When microparts are processed on a normal lathe, thecutting speed decreases, increasing the roughness of theprocessing surface dramatically. In a lathe experiment using
a high-speed small-diameter spindle (manufactured by NSKLtd.), we proved the effects of increasing the speed of thespindle on improving the lathed surface.
Fig. 3 shows the condition of the surface of brass after
lathing the piece to a diameter of 100 µm. Deep striation andthe like observed when using a spindle rotational speed of 2 x
104 rpm did not appear when the speed was 16 x 104 rpm.
Fig. 4 shows the relationship between the rotational
speed of the spindle and the arithmetic average roughness(Ra) of the lathed surface. A remarkable improvement insurface roughness occurred at a rotational speed of 4 x 104
rpm (a lathing speed of 13 m/min) or greater, while a Ra
value of approximately 20 nm was obtained at 16 x 104 rpm.
These results indicate that microfabrication devices capableof achieving high spindle speeds are effective in improving
the processing surface.

Sliding guides

2104 rpm

16104 rpm

05[ µm ]

60

Thrust
0N
5N
10N

40

20

050

80

110

140

170

200

Slider surface pressure (kPa)

Fig. 2 Properties of the direct-driven device

510 [ µm ] 15
[ µm ]

0.00

1.12

1.72

Fig. 3 Topography of the lathed surface

Arithmetic average roughness Ra(nm)Slider velocity V (µm/s)

100010 [ µm ] 150.00

Fig. 1 Construction of a direct-driven device0055[ µm ] 10[ µm ] 101515Piezoelectric elements

thrust of 10 N or less is possible when the slider surfacepressure is approximately 150 kPa.

120Workpiece : brass
Lathing diameter : 100µm
80

400048121620

Rotational speed n(104 rpm)

Fig. 4 Characteristics of high-speed lathing

MICROMACHINE No. 41
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Date of Issue : October 21, 2002

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