Published papers

Viscoelastic polymer with high scratch resistance has been developed for coating material of product. Due to some particular characteristics such as viscoelasticity, it is difficult to finish the polymer coated surface. In the present circumstances, its polishing process is carried out by the trained technician and depends on the skill like adjustment of the polishing pressure according to the situation. To realize automation of the polishing, high-precision and highly-responsive force control is required firstly. Typically force control is done with force sensor. However when external sensor is used, there are some problems such as high-cost, reduction of machine stiffness and thermal drift. The thermal drift which is caused by polishing heat prohibits accurate measuring of force. The purpose of this research is to develop the polishing pressure control method without any additional sensor. In addition, applying the control method to buffing machine, buffing performance of viscoelastic polymer is experimentally analyzed.

Plastics are regarded as proper materials for microfluidic chips, and, in particular, biodegradable plastics will be more appropriate from the viewpoint of environmental friendliness. In addition, when they are utilized as chip substrate, biochemical machining can be applied. Biochemical machining is a process, which utilizes enzymatic biodegradation. This paper describes studies on application of biochemical machining to nanofabrication of poly(L-lactic acid) (PLLA), which is one of the most widely used biodegradable plastics industrially. The degradation performance of enzyme (proteinase K) was experimentally evaluated to extrapolate a suitable condition for nanofabrication. Additionally, in order to make arbitrary channels with nano-order depth on PLLA, mask fabrication was proposed. It is a fabrication method to control degraded regions and obtain desired shapes with a mask, which has penetrating grooves. Using this method, we achieved fabrication of straight grooves with nano-scale depth. In conclusion, it is clear that biochemical machining can realize an effective process of arbitrarily shaped nanogrooves on PLLA. (C) 2011 Elsevier Inc. All rights reserved.

Electro-rheological gel (ERG) is a new functional material whose surface friction and adhesive properties vary according to the intensity of the applied electric field. In a recent study, one-sided patterned electrodes were applied to the ERG and the change in surface frictional and adhesive property under the electric field, which is called the ERG effect, was experimentally confirmed. The ERG with one-sided patterned electrodes is considered to be suitable for application to a fixture device for micro milling. In this study, a prototype of the ERG fixture device was developed and its performance was experimentally investigated. The proposed ERG fixture devices can be useful for fixturing both metallic and nonmetallic workpieces, such as glass. Micro shrinkage of the ERG occurs in proportion to the voltage applied to the ERG material. Using this characteristic, the alignment of the workpiece can be also adjusted. The developed ERG fixture device was applied to the micro grooving process of a thin glass workpiece, and successful results were obtained.

An electro-rheological fluid (ERF) is a functional fluid whose viscoelastic properties vary according to the intensity of the applied electric field. ERFs are mixtures of nonconductive silicone oil and inorganic/organic composite electro-rheological particles. The properties of ERFs have been exploited to control the performance of machine elements. ERFs have been applied to machine elements such as variable dampers and clutches. However, ERFs have disadvantages, namely the sedimentation of ER particles and the requirement of a seal mechanism. The sedimentation of ER particles reduces the ER effects and results in low stability of ER devices. In order to suppress the sedimentation, and thereby improve the performance of ERF devices, a new functional material called the gel-structured ERF (ERG) is developed, whose basic properties are analyzed in this study. The ER particles are suspended in the gel component, and thus will not precipitate out. This suppresses the decrease in the ER effect caused by precipitation. The ERG developed shows a large shear stress variation in response to the applied electric field. This high performance of ERG originates in a mechanism different from the ER effects of ERF. In order to elucidate the mechanism in ERG, the behavior of ER particles was observed under an electric field. The results show that the contact conditions at the interface between electrode and ERG change rapidly in response to the applied electric field, which result in a variation in shear force. On the basis of the results of a preliminary analysis, ERG was applied to the precision clamp system of an aerostatic slider, and its performance was assessed experimentally. (c) 2005 Elsevier Inc. All rights reserved.

Electro Adhesive Gel (EAG) has the unique characteristic of changing its surface adhesive property with the intensity of the electrical field applied. This propertymakes EAG useful in applications to fixing devices and mechanical brakes. Although its adhesion performance depends on the distribution of the electrorheological particles in the EAG, it is difficult to arrange the particle distribution uniformly in a wide area from the perspective of production process. In this study, a novel functional elastomer that has the same function as EAG is developed, Electro Adhesive Surface (EAS). In EAS, micro photolithography is used to fabricate strut pyramids distributed uniformly on a substrate, and then silicone gel is poured into the structure. When an electrical field is applied, the silicone gel rises to the tops of the pyramids formed by the struts, and adhesion occurs to an object on EAS. To determine a micro structure design for EAS, the fixing force was measured with various struts diameter and gaps. Experimental result shows that the larger struts diameter and the narrower gaps enhance the fixing force of EAS.

A more efficient and precise grinding method for optical glasses is demanded to improve lens quality and productivity. The Reaction Induced Slurry Assisted (RISA) grinding method enhances the ability of ductile regime grinding by utilizing the chemical mechanical action of cerium oxide slurry. In this study, the grinding performance of RISA grinding to multiple optical glasses is experimentally evaluated. The result shows that RISA grinding efficiently produces a fine quality surface of crown glass with high Si-O bond content.

Directed energy deposition (DED) is one of additive manufacturing processes attracting attention from various industries. Foam metal is a material having beneficial characteristics, but is difficult to produce with conventional manufacturing system. This study proposes a simple foam metal fabrication method by applying DED. The proposed method produces foam stainless alloy in DED by adding a foaming agent, titanium hydride (TiH2), into the powder material. This study evaluates the foaming behavior of porous stainless in DED by changing the particle size of TiH2 and the number of layers per line, and obtains the optimal number of layers to improve the porosity dispersion.

Using data-based approaches, accurate predictions of thermal deformations, which can significantly affect the quality of manufactured components, can be enabled. However, a sufficient amount of data with maximised information content is necessary for efficient training. In this paper, an approach for optimising sensor configurations for predicting thermal deformations is presented. From initially 300 temperature sensors, the number of required sensors was significantly reduced while maintaining predictive accuracy. Furthermore, a pattern for sensor placement was identified, providing the potential for an efficient sensor layout that enables cost-effective data acquisition and improved monitoring of machining and wear progression of machine tool components.

In recent years, with the spread of electric vehicles, development of high-performance mechanical parts has been required. With respect to the manufacturing process, metal Additive Manufacturing (AM) such as Directed Energy Deposition (DED) is attracting attention in automobile industry. Since the DED process can deposit molten material onto the specific surface, where it solidified, it is regarded as a promising coating process to enhance the hardness and surface functionality of mechanical parts. From this perspective, a gear coating process using DED is proposed in this research to strengthen gear surface and its basic study is conducted. Concretely, the coated material quality and mechanical properties like hardness are evaluated.

Rotary encoders are used in various machines to measure the angular position of a rotating axis. Therefore, rotary encoders are required not only to be highly accurate, but also usable in various environments. When using a rotary encoder on a machine, acquired angle errors occur due to the eccentricity between the encoder and the machine, the deformation of the scale, and the shaft runout of the rotation axis. Various methods have been adopted to reduce such angle errors. However, these methods have problems such as the large size and high cost of the encoder, the necessity of additional devices for measuring, and increasing installation labor, so the environment in which they can be implemented is limited. In this study, we have proposed a method to correct the acquired angle errors based on variation of an angle detection signal intensity in the sensor head. This method can correct the errors on the machine without using multiple sensor heads or additional devices. The angle error estimated by this method is compared with that measured by the external equipment of a reference encoder. While the maximum angle error was 28.36″ without correction, the residual error with correction of the acquired error can be reduced to 1.75″ or less. From this result, the proposed method can improve the measurement accuracy of the rotary encoder already installed on the machine. Therefore, this method is an effective means for achieving both high rotational accuracy on machines and ease of correcting an error in rotary encoder machines.

Selective laser melting (SLM) is one of the additive manufacturing (AM) methods which is applicable to metal. Although this technology enables to form complex inner shapes such as lattice structure, steep temperature gradients due to local laser irradiation and uneven heat conduction during the process may cause bending and cracking of the product. In this study, the influence of laser power and scanning speed on the mechanical characteristics of the support structure and lattice structure formed by SLM is investigated. In the tensile test of the support structure, a positive correlation with volumetric energy density was confirmed. In the compression test of the lattice structure, it was clear that larger amount of heat energy from the laser makes struts of lattice structure thicker and its Young's modulus higher.

Selective laser melting (SLM) is one of the additive manufacturing (AM) methods which is applicable to metal. This technique makes it possible to form complex internal shapes such as lattice structures. The lattice structure is expected to have weight reduction and vibration suppression effects on the product. In addition, a support structure is essential for the SLM fabrication process, which has the role of supporting the product and dissipating heat from the product. However, steep temperature gradients due to local laser irradiation and non-uniform heat conduction during the process can cause bending and cracking of the product. In particular, the support structure and lattice structure consisting of thin metal struts are greatly affected by process conditions, so it is necessary to select conditions suitable for stable and high-precision modeling. In this study, the influence of laser power and scanning speed on the mechanical characteristics of the support structure and lattice structure formed by SLM is investigated. In the tensile test of the support structure, a positive correlation with the volumetric energy density was confirmed, and suitable laser conditions were examined. In the compression test of the lattice structure, it was clear that the amount of energy absorption changed depending on the laser power, and the condition of 240 W achieved the maximum energy absorption.

In current practice, the buffing process required to finish the surface of mechanical parts is performed manually by a technical expert as it requires a delicate adjustment of the buffing force. The automation of this process is desirable in an effort to shorten the process time and reduce labor cost. To automate the buffing process, a beneficial process monitoring technique that supervises the buffing tool conditions in real time must be developed. From a practical perspective, an observer technique that does not require additional sensors would be most suitable for monitoring the tool operating condition. The authors propose a technique that estimates the buffing tool stiffness based on a disturbance observer. The validity of the proposed method as a buffing tool condition monitoring technique is verified through numerical simulations and experiments.