Ultrasonically Assisted Grinding for Mirror Surface Finishing of Dies with Electroplated Diamond Tools

Isobe, Hiromi,Hara, Keisuke,Kyusojin, Akira,Okada, Manabu,Yoshihara, Hideo Korean Society for Precision Engineering 2007 International Journal of Precision Engineering and Vol.8 No.2

This paper describes ultrasonically assisted grinding used to obtain a glossy surface quickly and precisely. High-quality surfaces are required for plastic injection molding dies used in the production of plastic parts such as dials for cellular phones. Traditionally, in order to finish the dies, manual polishing by a skilled worker has been required after the machining processes, such as electro discharge machining (EDM), which leaves an affected layer, and milling, which leaves tooling marks. However, manual polishing causes detrimental geometrical deviations of the die and consumes several days to finish a die surface. Therefore, a machining process for finishing dies without manual polishing to improve the surface roughness and form accuracy would be extremely valuable. In this study, a 3D positioning machine equipped with an ultrasonic spindle was used to conduct grinding experiments. An electroplated diamond tool was used for these experiments. Generally, diamond tools cannot grind steel because of excessive wear as a result of carbon atoms diffusing into bulk steel and chips. However, ultrasonically assisted grinding can achieve a fine surface (roughness Rz of $0.4{\mu}m$) on die steel without severe tool wear. The final aim of this study is to realize mirror surface grinding for injection molding dies without manual polishing. To do this, it is necessary to fabricate an electroplated diamond tool with high form accuracy and low run-out. This paper describes a tool-making method for high precision grinding and the grinding performance of a self-electroplated tool. The ground surface textures, tool performance and tool life were investigated A ground surface roughness Rz of 0.14 um was achieved Our results show that the spindle speed, feed rate and cross feed affected the surface texture. One tool could finish $5000mm^2$ of die steel surface without any deterioration of the ground surface roughness.

Non-contact Transportation of Flat Panel Substrate by Combined Ultrasonic Acoustic Viscous and Aerostatic Forces

Isobe, Hiromi,Fushimi, Masaaki,Ootsuka, Masami,Kyusojin, Akira Korean Society for Precision Engineering 2007 International Journal of Precision Engineering and Vol.8 No.2

In recent years, the size of plane substrates and semiconductor wafers has increased. As conventional contact transportation systems composed of, for example, carrier rollers, belt conveyers, and robot hands carry these longer and wider substrates, the increased weight results in increased potential for fracture. A noncontact transportation system is required to solve this problem. We propose a new noncontact transportation system combining acoustic viscous and aerostatic forces to provide damage-free transport. In this system, substrates are supported by aerostatic force and transported by acoustic viscous streaming induced by traveling wave deformation of a disk-type stator. A ring-type piezoelectric transducer bonded on the stator excites vibration. A stator with a high Q piezoelectric transducer can generate traveling vibrations with amplitude of $3.2{\mu}m$. Prior to constructing a carrying road for substrates, we clarified the basic properties of this technique and stator vibration characteristics experimentally. We constructed the experimental equipment using a rotational disk with a 95-mm diameter. Electric power was 70 W at an input voltage of 200 Vpp. A rotational torque of $8.5\times10^{-5}Nm$ was obtained when clearance between the stator and disk was $120{\mu}m$. Finally, we constructed a noncontact transport apparatus for polycrystalline silicon wafers $(150(W)\times150(L)\times0.3(t))$, producing a carrying speed of 59.2 mm/s at a clearance of 0.3 mm between the stator and wafer. The carrying force when four stators acted on the wafer was $2\times10^{-3}N$. Thus, the new noncontact transportation system was demonstrated to be effective.

Ultrasonically Assisted Grinding for Mirror Surface Finishing of Dies with Electroplated Diamond Tools

Hiromi Isobe,Keisuke Hara,Akira Kyusojin,Manabu Okada,Hideo Yoshihara 한국정밀공학회 2007 International Journal of Precision Engineering and Vol.8 No.2

This paper describes ultrasonically assisted grinding used to obtain a glossy surface quickly and precisely. High-quality surfaces are required for plastic injection molding dies used in the production of plastic parts such as dials for cellular phones. Traditionally, in order to finish the dies, manual polishing by a skilled worker has been required after the machining processes, such as electro discharge machining (EDM), which leaves an affected layer, and milling, which leaves tooling marks. However, manual polishing causes detrimental geometrical deviations of the die and consumes several days to finish a die surface. Therefore, a machining process for finishing dies without manual polishing to improve the surface roughness and form accuracy would be extremely valuable. In this study, a 3D positioning machine equipped with an ultrasonic spindle was used to conduct grinding experiments. An electroplated diamond tool was used for these experiments. Generally, diamond tools cannot grind steel because of excessive wear as a result of carbon atoms diffusing into bulk steel and chips. However, ultrasonically assisted grinding can achieve a fine surface (roughness Rz of 0.4 ㎛) on die steel without severe tool wear. The final aim of this study is to realize mirror surface grinding for injection molding dies without manual polishing. To do this, it is necessary to fabricate an electroplated diamond tool with high form accuracy and low run-out. This paper describes a tool-making method for high precision grinding and the grinding performance of a self-electroplated tool. The ground surface textures, tool performance and tool life were investigated. A ground surface roughness Rz of 0.14 ㎛ was achieved. Our results show that the spindle speed, feed rate and cross feed affected the surface texture. One tool could finish 5000㎟ of die steel surface without any deterioration of the ground surface roughness.

Non-contact Transportation of Flat Panel Substrate by Combined Ultrasonic Acoustic Viscous and Aerostatic Forces

Hiromi ISOBE,Masaaki FUSHMI,Masami OOTSUKA,Akira KYUSOJIN 한국정밀공학회 2007 International Journal of Precision Engineering and Vol.8 No.2

In recent years, the size of plane substrates and semiconductor wafers has increased. As conventional contact transportation systems composed of, for example, carrier rollers, belt conveyers, and robot hands carry these longer and wider substrates, the increased weight results in increased potential for fracture. A noncontact transportation system is required to solve this problem. We propose a new noncontact transportation system combining acoustic viscous and aerostatic forces to provide damage-free transport. In this system, substrates are supported by aerostatic force and transported by acoustic viscous streaming induced by traveling wave deformation of a disk-type stator. A ring-type piezoelectric transducer bonded on the stator excites vibration. A stator with a high Q piezoelectric transducer can generate traveling vibrations with amplitude of 3.2 ㎛. Prior to constructing a carrying road for substrates, we clarified the basic properties of this technique and stator vibration characteristics experimentally. We constructed the experimental equipment using a rotational disk with a 95-㎜ diameter. Electric power was 70 Wat an input voltage of 200 Vpp. A rotational torque of 8.5 × 10-? Nm was obtained when clearance between the stator and disk was 120 ㎛. Finally, we constructed a noncontact transport apparatus for polycrystalline silicon wafers (150(W) × 150(L) × 0.3(t)), producing a carrying speed of 59.2 ㎜/s at a clearance of 0.3 ㎜ between the stator and wafer. The carrying force when four stators acted on the wafer was 2 × 10-³ N. Thus, the new noncontact transportation system was demonstrated to be effective.