田中 秀岳

The demand for carbon fiber reinforced plastics (CFRP), classified as functional resins, has increased for micromachined products that are manufactured using lathes and used in the medical field. However, the problems with machining CFRP include the occurrence of burrs and deterioration of the finished dimensions owing to the significant tool wear caused by the carbon fiber. To turn CFRP and maintain high dimensional accuracy, the authors proposed a novel combination of conventional turning and electrical discharge-assisted turning (EDAT). In this study, the capability to control the machinability of EDAT under low-voltage conditions was experimentally investigated. The relationship between the discharge voltage, frequency, and depth of discharge influence of the carbon fibers was clarified.

Although, three-dimensional printing has several advantages, however there are currently many limitations. In particular, printed products using composite materials such as fiber-reinforced plastic have yet to achieve the same mechanical properties as those obtained from conventional manufacturing methods. In addition, fabricating thin plates or thin shell shapes with sufficient strength is challenging. Incremental forming enables high-mix, low-volume production of thin sheets. This method applies incremental deformation to thin sheets, the desired shape is obtained by accumulating the deformation, and no dies are required. Carbon-fiber-reinforced plastic (CFRP) materials have high specific strength. Discontinuous-fiber CFRP is capable of large plastic deformation under appropriate conditions due to the discontinuity of the reinforcement, and its mechanical properties are nearly isotropic due to the random fiber arrangement. The authors focused on this property and studied the application of single-point incremental forming to discontinuous carbon-fiber-reinforced polyamides. In this study, the workpiece was formed by heating it locally to a deformable temperature by the frictional heat between the rotating tool and the workpiece. The forming experiment was also conducted in an oil bath to keep the entire material at a suitable forming temperature. The results showed that the spindle speed affected forming results even in an oil bath and that heating using an oil bath suppressed deviations from the sine law for thickness and wall angle due to elastic deformation.

Carbon fiber reinforced plastic (CFRP) is a composite material with high specific strength and is applied to transportation and aviation equipment. However, conventional processing methods require large-scale production apparatus or a high level of dexterity that only comes with extensive experience which makes it difficult to achieve high processing efficiency. The objective of this study is to develop a novel method for forming thermos-plastic CFRP (CFRTP) preforms implementing a 3D printer for press molding. Applying this method offers the advantage that continuous carbon fibers can be formed on a free-form surface. It also reduces the manufacturing time and operator skill required. The goal of this research is to establish a method for molding a free-form surface composed of continuous fibers by employing a 3D-printed preform designed to match the unfolded polygonised diagram of the free-form surface. Previous research introduced an unfolding approach for converting a three-dimensional shape to a plane surface based on a computer-aided design and manufacturing (CAD/CAM) system, enabling the generation of an unfolding diagram that maintains the continuity of fiber tow. Furthermore, the validity of unfolded diagram was confirmed by reproducing the objective three-dimensional shape from the unfolded diagram using thermos-setting CPRP (CFRTS) tow prepreg. In this study, the viability of the proposed molding process using CFRTP preform fabricated by a 3D printer was verified and an assessment of the formability of the molded parts was conducted.

The Swiss-type automatic lathe is designed for continuous mass production of the same product. In the research, the authors propose a combined turning process in which a joining process using the frictional welding method is introduced into the automatic lathe. If the joining process is performed with a Swiss-type automatic lathe, it is expected that the problem of a large amount of residual material due to the mechanical structure can be solved. Generally, the friction welding method is performed by a dedicated machine and is pressure controlled by a hydraulic power source, however in the case of an automatic lathe, friction welding is controlled by the feed length and feed rate. The low rigidity of automatic lathes is also concerned. In the study, the authors investigated the tensile strength and rotational bending fatigue strength of the A6061 bonding material to investigate and quantitatively evaluate the optimum friction welding conditions that can obtain good bonding results in the friction welding method using a multi-axis automatic lathe. Upset speed was the most influential factor for tensile strength and friction rotation speed was good at about 4000 rpm. This fact suggests that excessive heat input leads to a decrease in tensile strength. The tensile strength was equivalent to that of the annealed material. It also seems that the air-cooled annealing phenomenon occurs during the friction welding process. The results of rotational bending fatigue strength were similar to those of the annealed material. It is clarified that friction welding with an automatic lathe is feasible, however, the strength of the bonded material is reduced to the same level as that of the annealed material.

A three-dimensional (3D) printer can be used to form various shapes in a single process. However, shell shape formation is difficult because of the low adhesion strength between the layers in 3D printing, and sufficient stiffness cannot be maintained. Therefore, the authors focused on laser-assisted incremental forming, which enables the formation of shell shapes from sheet materials, and used carbon fiber reinforced thermo plastic (CFRTP) for the samples. In the study, a laser-assist incremental forming system based on 3D computer-aided design (CAD) data was developed. The system comprises computer-aided manufacturing (CAM) system, which generates a tool path based on CAD data and evaluates the formability between the CAD data and 3D-scanned data, including alignment compensation. The feasibility of the developed system was demonstrated through a set of forming experiments.

Carbon fiber-reinforced plastics (CFRP), which are classified as functional resins, are rapidly replacing conventional materials because of their excellent properties. Typically, they have been used to fabricate components of airplanes or cars. In the field of medicine, the demand for micro-machined products manufactured with lathes is also increasing. However, owing to the significant tool wear caused by the carbon fiber, CFRP machining can result in burrs and inaccuracies in the finished product. The tool wear caused by carbon fiber must be reduced to ensure high dimensional accuracy. In this study, the possibility of combining conventional turning with electric current or electrical discharge machining was explored.

In this study, a novel design and fabrication method that corresponds to simple and optimized press molding for carbon fiber reinforced plastics (CFRP) is proposed based on CAD data. Specifically, in recent years, CFRP has been widely used for weight reduction of transportation equipment. However, optimization of the production process is required to expand the range of applications of CFRP. To satisfy the aforementioned requirements, this study focused on the press molding technique. It was assumed that partial excessive or partial breakage of the fiber occurs due to the drawing of the fiber by the deformation force. A design and fabrication method was proposed for CFRP preform that exhibits the unfolded diagram shape of an objective three-dimensional (3D) model by using a tow prepreg as a solution for the aforementioned problems. A calculation method to generate the unfolded diagram was also proposed. Furthermore, the validity of the unfolded diagram was confirmed by reproducing the diagram for a 3D shape.

The study deals with development of the inclined planetary milling spindle unit. Although CFRP and composite materials are known as difficult-to-cut-material due to their abrasive action for intensive wear of cutting tools, they are widely used as structural materials in recent aviation industries. The orbital drilling technique is one of possible solutions for making hole drilling faster and more effective in aviation assembling process. However the orbital drilling has some drawbacks such as vibration and cutting with 0 velocity point. In order to improve machinability of the orbital drilling, the authors propose an inclined planetary milling system which is inspired by the oblique and helical milling by 5-DOF machining center to avoid cutting with 0 velocity point. Eccentricity is realized by a few degrees inclination of tool rotation spindle and it can reduce mechanical vibration. In the study, analysis of geometric machining model of the inclined planetary milling has been considered. A prototype of the spindle unit was developed and actual drilling experiment were carried out. Comprehensive observation revealed that vibration, machining force, burrs and delaminations are greatly improved in comparison with the orbital one. This inclined planetary milling method has some advantages and its practicality and usability has been demonstrated.

This paper deals with invention of a new measurement principle for straightness profile measuring instrument based on numerical software datum. The novel sequential two-point method was realized using a twin heads displacement sensor and a shifting reference plate in the lateral direction. Utilizing a precise level meter for correction of the reference plate slope, a long distance straightness profile can be measured in an extrapolative way. Uncertainty analysis on designed specifications of the measuring instrument assured its high accuracy and practicality. The experimental variation of straightness profiles measured by a developed measurement system was in a good agreement with the numerical simulation.

This study deals with drilling kinematics by planetary mechanism, adopted tool performances and cutter wear phenomena. Recently lightweight materials such as CFRP or titanium alloy are widely used as structural materials in aviation and aerospace industries for the purpose of mass reduction. Although these materials have characteristics of lightweight and high strength, they are regarded as difficult-to-cut materials. Planetary mechanism drilling is one of effective drilling methods for difficult-to-cut materials. The advantages of planetary mechanism drilling are short machining time, high-quality drilled holes and long tool lifetime. In this study, three types of tools for the planetary mechanism drilling were developed on the basis of kinematics of the cutting edges. Through the experimental results of tool wear or cutting edge observation, cutter performance of the tools and tool lifetime were made clear.

<tt>The study deals with the development of a diamond burnishing tool with a hydraulic control system for discontinuous workpiece surface finishing. Burnishing can be regarded as an alternative surface finishing technology. However, applying a commercial burnishing tool to a discontinuous surface is almost impossible owing to its configuration. We developed a hydrostatic burnishing tooling system and demonstrated the capability of the system developed. To apply burnishing to an interrupted surface, we tried to develop a hydrostatic burnishing tooling system. The system developed permits a minimum displacement of the pushed depth as well as in-process burnishing force monitoring. Some experimental results demonstrated the capability of the hydraulic burnishing tool to be applied to an interrupted surface. Also we discussed in this report is the relationship between compression depth and surface texture, determined by comparing the hydraulic burnishing tool developed with a </tt><tt>commercial one. </tt>

This study deals with a surface modification phenomenon in a cylindrical surface finishing process using diamond burnishing tools. The burnishing process is a micro-plastic machining method, in which a spherical diamond point tool compresses the metal surface to obtain a mirrorlike surface roughness; it could improve surface layer hardness similarly to the shot-peening process. In this report, we try to evaluate the surface modification in the burnishing process using the nanoindentation technique and an X-ray residual stress measuring instrument owing to the extremely thin surface layer. From the experimental result, the hardness of the surface layer is improved (by at least 100 HV) and a significant residual stress (-700MPa) remains on the surface layer of the burnished workpiece.

<jats:p>This study deals with the development of a CAM system that considers the deforming process for a forgingtype rapid prototyping system. An industrial robot that has high degrees of freedom is employed to handle the hammering unit. A special CAM system suitable for the hammering work is developed using parametric curve interpolation. The tool path is generated considering continuity in order to avoid fracture or breakage. Using the system, metal hammering experiments are carried out. The system successfully shaped workpieces according to the generated path. The experimental results confirm the ability of the system to improve, owing to the parametric curve interpolation, forming properties.</jats:p>

The study deals with an automation of chamfering by a material-handling robot with considering of accuracy and costs. The study focused on automation of chamfering without influence of individual dimensional error of workpiece. A casted impeller usually chamfered with handwork is treated in the study as an example of a workpiece having individual dimensional error. In the system, a file driven by air reciprocating actuator is used as a chamfering tool and image processing technology is used to compensate the dimensional error of the workpiece. The robot hand carries a workpiece instead of a chamfering tool both for chamfering and for material handling. From the experimental result, the system is found effective to chamfer a workpiece having dimensional error automatically.

This study deals with experimental and geometrical analyses of a cylindrical surface finishing process using a diamond burnishing tool. Roller burnishing techniques are applied to the surface finishing of aluminum alloy or stainless steel parts. However, they are not applicable to hardened work materials such as high-carbon-chromium- bearing steel. Diamond burnishing tools, instead of the roller tools, are used to finish such hardened materials. Certain practical burnishing tests were carried out under several machining conditions considering burnishing load, feed rate and diverse preliminary processes using an NC. lathe. From the experimental results, the effect of surface texture on and the estimation of a dimensional change in burnishing are clarified and performed, respectively.

This study deals with a development of analytical estimation system for machined surface texture based on tool run-out and cutting edge profile measurement for end-mills by optical method. In the article, geometrical cutting model is proposed with a consideration of tool deflection, tool run-out and cutting edge profile. In order to obtain those analytical parameter values, we constructed certain optical equipments for measuring spindle rotation trajectory and cutting edge profile in three dimensions. Through an analytical consideration of tool run-out trajectory, we revealed that the tool run-out components (both RRO and NRRO) are geometrically transferred to the machined surface as the corresponding wavelength components. From the experimental result, wavelength spectrum between surface roughness profile and tool run-out trajectory is closely conformed to the analytical simulation.

This study deals with the automation of metal hammering using an industrial robot and trial development of rapid prototyping of sheet metal forming. Computer-aided manufacturing (CAM) takes into account feedback considering tool positioning by using a range finder to improve depth and shape error at workpiece corners. Experimental results confirmed that our proposal reduces shape error through tool positioning optimization.

This study deals with automation of metal hammering working on the basis of CAD data as a forging type rapid prototyping system. In this article, in order to analyze the phenomenon in metal hammering working, a CAM system for metal hammering is developed and experiments of incremental metal hammering based on the system are examined under several conditions. From the experimental result, influences of the mode of a tool path on the deformation behavior, a possibility to improve a forming limit by distribution control of strain on a workpiece and a capability of the system to perform the forging type rapid prototyping are found.

<jats:p>The forging rapid prototyping we proposed based on CAD data involves numerically controlled free forging and metal hammer working as new three-dimensional modeling. Almost all products are now designed and developed using CAD/CAM, and rapid prototyping using CAD data is also used to model design previews or mock ups. Free forging and plastic working, however, have few ways to automate the process. We developed numerical controlled free forging and metal hammer working as new modeling for rapid prototyping. Experimental results demonstrate that our proposal provides feasible three-dimensional modeling as rapid prototyping.</jats:p>