Study on precision polishing of micro structured mold -Development of micro polishing system using piezoelectric actuator incorporated with mechanical transformer- Sze Keat Chee 1 , Hirofumi Suzuki 2 , Mutsumi Okada 2 , Kazufumi Yoshida 3 , Weimin Lin 4 , Takeshi Yano 1 , Toshiro Higuchi 5 1 Mechano Transformer Corporation, 2 Chubu University, 3 Nagatsu Precision Mold Co., Ltd., 4 Akita Prefectural University, 5 The University of Tokyo Demands of precision molds with complicated microstructures for digital devices, μ-TAS and etc. are increasing [1] . The structured molds must be polished after grinding or cutting in order to improve the surface roughness. In this report, a two dimensional low frequency vibration (2DLFV) polishing actuator using PZT is proposed and developed. The 2DLFV consists of 4 MechaTrans, a multiplayer stacked piezoelectric actuator (PZT) incorporated with mechanical transformer, and a center piece. Mechanical transformer is a kind of flexure hinges structured that magnifies the stroke of the multiplayer stacked piezoelectric actuator around 7 times to 120 μm. With this actuation, the tool vibrates in a circle trajectory to achieve polishing effect [2] . In the polishing experiments, tungsten carbide molds (work pieces) are polished with diamond slurry. The surface roughness of the work pieces and polishing efficiency are evaluated. From the experimental results, we found low frequency vibration especially 2DLFV is a useful micro polishing system for micro structured mold. 1. Introduction Recently, demands of precision molds with complicated microstructures for digital devices, μ-TAS and etc. are increasing [1] . The structured molds need polishing process after grinding or cutting in order to improve the surface roughness. The precision polishing technology of structured molds is becoming more and more important due to the insufficient of the skilled worker in realizing the complicated micro-structured mold. In this report, a two dimensional low frequency vibration (2DLFV) polishing actuator is proposed and shown to be effective for precise structured surface polishing. 2. Configuration and fabrication of 2DLFV The concept of 2DLFV is moving the tool in 2 dimensional directions such as circle with low frequency vibration to polish the work through abrasive material such as diamond slurry. Figure 1 shows the idea of polishing process. The 2DLFV can be realized with many kinds of configuration of actuators. As an example, 2DLFV introduced here consists of 4 MechaTrans and centerpiece as shown in Fig.2. The polishing tool is fixed at the centerpiece. These MechaTrans are driven with a particular frequency of sine wave with 90 degree phase different to each other. This cause the polisher tool vibrates in a circle trajectory. The trajectory can achieve polishing effect at the particular frequency [2] . Fig.3 shows a MechaTrans which its actuation is diagonal direction to the actuation direction of the PZT. The stroke of the PZT is magnified 7 times to 120 μm. Fig. 4 shows the fabricated 2DLFV. The 2DLFV actuates about 120 μm at around 900 Hz with applied voltage 15 V. The stroke measurement result is shown in Fig. 5. 3. Basic polishing characteristics In order to study basic polishing performances, the Fig. 1 Concept of 2DLFV polishing Fig. 2 Configuration of 2DLFV Fig. 3 Actuation of MechaTrans 11 春 - 865 - K69