Proposal of ‘ImpEC (impact excitation cutting)’ for realization of high-flexibility and high-efficiency micro/nano surface texturing

doi:10.1016/j.cirp.2021.04.023

CIRP Annals

Volume 70, Issue 1, 2021, Pages 41-44

https://doi.org/10.1016/j.cirp.2021.04.023 Get rights and content

Abstract

In this paper, a novel micro/nano surface texturing method, namely ‘ImpEC (impact excitation cutting)’, is proposed. To machine micro/nano-textures, vibration cutting and fast tool servo have been utilized. However, the former one is limited to formation of periodical combination of sine waves since the resonance(s) of the cutting tool system is used, and the latter one is limited in terms of efficiency since it has conventionally been utilized within the bandwidth of the servo system, e.g. 3 kHz. Hence, conventional methods cannot realize high flexibility and high efficiency simultaneously. In the proposed ImpEC (impact excitation cutting), the frequencies higher than the resonant frequency are also used, and a series of impacts (pulses) are utilized to diminish the residual vibration. The proposed cutting method can create structures in a short time since the high frequency components are also used, and it can also realize high flexibility since a variety of texturing motions without residual vibrations can be triggered at any timing. The effectiveness of the proposed method is verified both analytically and experimentally.

Introduction

Micro/nano textures on surfaces of products can enhance characteristics such as hydrophobicity [1], optical functionality [2], and tribological performance [3]. Hence, research interest has focused on the manufacturing of these textures [4]. Especially, ultraprecision diamond cutting has received special focus because of its high precision and high efficiency.

In the literature, a variety of methods have been developed, and many of them have been utilized in practice. The most famous method is the fast tool servo [5,6]. In this method, the frequencies below the resonant frequency of the cutting tool system have been conventionally used to control the trajectory of the tool. Therefore, periodic/aperiodic structures can be machined with a high degree of freedom. Moreover, an ultrafast tool servo was also developed to increase the bandwidth of the system, where a flat gain up to around 3 kHz can be obtained for the closed-loop system [7]. However, this method has a limitation in efficiency since only the frequency components below the resonance are used, and hence the adopted cutting speed is low.

Another method is the vibration cutting [8,9]. To achieve a micron-order vibration amplitude at an ultrasonic frequency, the mechanical resonance of the cutting tool is generally utilized. Due to this nature, the fabricable structures are limited to periodic sine-waves. On the other hand, to increase the flexibility of the machinable micro/nano structures, multi-mode vibration cutting has been developed, where multiple modes of the vibratory cutting tool are utilized so that combination of sine waves can be output [10]. However, the structures are still limited to periodic structures since only the resonant frequency components are utilized.

In summary, it can be said that there is no texturing method which realizes high flexibility and high efficiency simultaneously. In this paper, a novel cutting method named ‘ImpEC (impact excitation cutting)’ is proposed. In this method, a high frequency range, which includes frequencies higher than the resonance of the cutting tool system, is used so that a high cutting speed can be adopted. In addition, the residual vibration due to the impact excitation of the cutting tool is suppressed by a series of other impacts based on the input shaping method [11]. As a result, a variety of micro/nano structures can be machined at an arbitrary timing, i.e. the flexibility is high. Therefore, the proposed ImpEC can realize high efficiency and high flexibility simultaneously.

Section snippets

Proposal of ImpEC and analytical investigation

In this chapter, the characteristics of ImpEC is explained in detail. Fig. 1 shows a schematic of the proposed method, and Fig. 2 shows a schematic of how the vibration is suppressed in ImpEC. For simplicity, a single resonant mode for the cutting tool with a resonant frequency of $f_{n}$ is assumed. In the proposed ImpEC, a series of impacts are utilized to achieve the micro/nano structure and suppress the residual vibration due to other impacts based on the input shaping method [11]. In the

Experimental verification

Experiments are conducted to verify the proposed cutting method. An ultraprecision 5-axis machine tool (ROBONANO $α$ -NM $i$ A, Fanuc Corp.) is utilized for cutting, and a piezoelectric stage (PU1H70F-012 U, THK Precision Co., LTD.) is mounted onto it. A photograph of the experimental setup is shown in Fig. 8, and the specifications of the tool/workpiece, the machine tool, and the piezoelectric stage are shown in Table 1. Note that the tool system can be of any kind. The voltage function prepared on a

Conclusion

A novel texturing method named ImpEC has been proposed in this paper. In the proposed method, a series of impacts are prepared to generate the texture and suppress the residual vibration. Compared to fast tool servo, where the frequency components below the resonance are utilized, the proposed method utilizes components above the resonance also, which means that higher efficiency can be achieved. Compared to vibration cutting, aperiodic textures can be machined since residual vibration is

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

The research is supported by the Program for Building Regional Innovation Ecosystem “Aichi Innovation Ecosystem Project for Next-Generation Automobile” from the Ministry of Education, Culture, Sports, Science and Technology of Japan. In addition, the authors would like to express their sincere thanks to FANUC Corp. for their help to conduct the present research.

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