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.

© 2018 Elsevier B.V. The aim of this study was to develop an incremental forming method for carbon fiber reinforced thermoplastics (CFRTPs) using an optical heating system. The developed forming machine was mainly composed of a vertically articulated robot to control the position of the blank sheet on the X-Y plane, a reciprocating mechanism to generate the reciprocating motion of the forming punch, an electrical cylinder to control the position of the reciprocating mechanism, and a halogen lamp for local heating. Discontinuous short-fiber CFRTP work sheets with thickness of 0.5, 1.0, and 1.5 mm were used for the experiment. Each work sheet was fixed to a blank holder and locally heated by a halogen lamp set under the work sheet. The heated region of the work sheet was formed using the reciprocating motion of a spherical forming punch with a punch radius of 0.5, 1.5, or 2.5 mm, which was located on the opposite side of the halogen lamp. In order to evaluate the fundamental forming characteristics of the developed system, simple spot-forming was performed without feeding a work sheet on the X-Y plane. The work sheet temperature was set to 200 °C at a distance of 3.0 mm from the optical axis of the halogen lamp for each work sheet thickness. This study examined the relationship between the pushing distance of the reciprocating forming punch to the work sheet and the forming height, which was the distance between the top of the formed concave portion and the flange region of the work sheet. The forming height was lower than the pushing distance of the forming punch, and this tendency was conspicuous when the work sheet was thin and the punch radius was small. Fractures in the formed part were caused by excessive thinning of the work sheet due to the tensile deformation at the sidewall of the formed shape. The symmetrical shape profile of the formed part following the forming punch shape could be obtained when the pushing distance did not exceed 7.0 mm with a work sheet thickness of 1.5 mm and punch radius of 2.5 mm. The shape profile of the formed product obtained by two-dimensional sheet-fed forming was also estimated to evaluate the advantage of the developed method. The forming characteristics in the two-dimensional sheet-fed forming were different from those in the spot-forming. The continuous formed shape according to the sheet-feeding path could be achieved by the two-dimensional sheet-fed forming, and the advantage of the developed method could be experimentally clarified.

In recent years, CFRP is widely used as an alternative structural material to improve fuel consumption with high strength and light weight comparing to conventional aluminum alloy. CFRP is also expected to be the structural material for next generation automobiles - especially electric vehicles - in order improve fuel and/or electric power efficiency. However, CFRP is categorized as one of the difficult-to-cut material and burrs and delamination could occur with conventional drilling and cutting ways due to their severe cutting tool wear. For above mentioned reasons, in order to improve the machinability of CFRP drilling situations, the authors have proposed the inclined planetary milling process as a novel high quality boring technique for CFRP. According to our past experiments, the effectiveness for reduction of burrs and delamination of CFRP boring by the inclined planetary milling has been demonstrated. However, demands for higher speed and wear resistance of cutting tools are rising in the industrial field. The objective of the study is to achieve shorter processing time of CFRP boring and reduction of tool wear with maintaining high bore quality. The authors have carried a set of experiments for evaluating the relationship between feed rate variations and bore quality transition. The workpiece materials were unidirectional and fabric CFRP stack plates and the cutting tool shape was corner radius end-mill. From the experimental results, it was confirmed that the feed rate per one cutting edge strongly affected the generation of cross-sectional profile of the bore. This was also theoretically confirmed by our developed kinematic cutting model of the inclined planetary milling theoretically. In the article, the optimal cutting conditions of the inclined planetary milling for CFRP boring and factorial effect of feed rate to the bore quality are reported.

The study deals with a novel drilling technique of carbon fiber reinforced plastic (CFRP) with high precision and efficiency. The characteristic of high specific strength of CFRP. It enables to reduce the mass of the structure, improve the fuel economy, and reduce the environmental load. Alternating structural materials to CFRP for various products are ongoing. However, due to the structure of CFRP, burrs and delamination occurs when drilling a hole. Presently, it is reported that the helical machining and the planetary drilling processes are efficient to avoid burrs and delamination. Even though, by using those methods, there are limit to improve the circularity and the surface roughness of the hole. It is due to the vibration caused by the structure of the machine. In the research, we suggest the inclined planetary milling to solve the problems. The inclined planetary milling is a drilling method with a precession movement, which is performed by rotating an inclining spindle in the rotation of the tool. The inclined planetary milling enables to reduce the vibration of the machine, miniaturize the machine, improve the quality of the hole and reduce the machining cost. In our previous research, we have fabricated a prototype machine, carried out drilling experiments and confirmed its superiority to other machining methods. In the case of the prototype, the dimension of the hole sets manually. It does not seem practical and limits the conditions of experiments. In the study, we fabricated a new prototype that enable to set in practical conditions, conduct experiment and confirm superiority toward other processing methods.

Currently, 3D printing has been attracting attention as a new method of prototyping and manufacturing. However, in the case of molding of the shell shaped resin, products by the additive manufacturing method has low strength of the interlayer adhesion and low stiffness of the light curing resin. For these reasons it is difficult to achieve the equivalent strength to injection-molded products. In study, in order to improve the strength of shell shape 3D printing, the authors propose a novel forming method by means of CFRTP and a forming system based on CAD data with local heating system, which can maintain the target formable temperature by a feedback control system was developed.

CFRP and Titanium alloy, which are known as difficult-to-cut materials have been widely used as structural material in aviation industries. The orbital drilling is one of an effective drilling technique for the industries. However this technique has some disadvantages such as increase of cutting force due to cutting with tool center point, inertial vibration generated by revolution and high installation cost. In order to improve the disadvantages, we have invented a new drilling technique which is called inclined planetary motion milling. The inclined planetary motion milling and the planetary mechanism drilling has two axes of cutting tool rotation axis and revolution axis. Cutting tool rotation axis of the orbital drilling is moved parallel to the revolution axis in eccentric. On the other hand, in the case of the inclined planetary motion milling, eccentric of the cutting tool rotation axis is realized by inclination of a few degrees from the revolution axis. Therefore, the movement of eccentric mechanism can be reduced by comparison with the orbital drilling because inclined angle is smaller than eccentricity of the cutting tool tip. As a result, eccentric mechanism can be downsized and inertial vibration is reduced. In the study, a geometrical cutting model of inclined planetary motion milling was set up. The theoretical surface roughness of the inside of drilled holes by use of two types cutting tool geometry were calculated based on the model. And cutting experiments using the new prototype for CFRP were carried out in order to evaluate the effect on machinability with change of cutting point atmosphere. In addition, optimal cutting condition was derived according to cutting experiments for titanium alloys utilizing the orthogonal array.

Recently, the applications of difficult-to-cut materials ( e.g. CFRP and titanium alloy) are increasing in the aviation and automotive industries. Conventional drilling tools occur burr and/or delamination on their materials. The inclined planetary motion milling consists of two independent spindle motions which are tool rotation and revolution. Eccentricity of the tool rotation axis is realized by inclination of few degrees from revolution axis. The movement of eccentric mechanism can be reduced by comparison with that of the orbital drilling. The inclined planetary motion milling reduces inertial vibration and decreases cutting force. According to the geometrical cutting principle, it can be decreased delamination and burr of their materials, comparing to orbital drilling. In the study, the authors revaluated optimum cutting condition for titanium alloy by use of the experimental design and carried out its repeatability test. And the authors developed on measurement and evaluation method for cutting edge profiles and examined the comprehensive discussion of the relationship among change to cutting edge wear and surface texture and circularity on drilling hole, tool rotation torque after based on the practical drilling experiments. (C) 2015 The Authors. Published by Elsevier B.V.

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.

Drilling Carbon Fibre Reinforced Plastics (CFRP) induces different material defects like delamination, burnt matrix material, rough bore channel surfaces, fibre pull-out and uncut fibres. Intensive research has been conducted to analyse the amount of defects caused, describing the surface and subsurface defects introduced by machining operations [1, 2]. Additionally, the mechanical strength of rivet joints has been analysed intensively [3]. However, the mechanical performance of rivet joints includes many influencing factors as different materials prepared with various machining processes are being joined. The presented study introduces five newly developed test rigs to analyse the mechanical performance of single bores in relation to different drilling and loading conditions. The setups are designed to focus either on the mechanical strength of the bore channel or the drill entrance or exit. The developed test rigs expand the capability to describe the workpiece quality after a drilling operation. The test rigs facilitate an efficient quality evaluation of drilling processes as well as the development of adapted drilling tools.

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>

The study deals with a proposal and experimental study on the tilted planetary motion drilling for CFRP. The authors have modified cutting mechanism principle of the orbital drilling, which named as the tilted planetary motion drilling. Its axis of tool rotation spindle is not parallel to the axis of planetary revolution. The tilted angle is adjustable from 0 to 2 degrees. Because of tool rotation axis is tilted, penetration is not caused by outermost cutting edges but inner cutting edges. If penetration could be occurred, the inner cutting edges penetrate firstly, then the outermost edges enlarge drilled hole and these sequence can avoid generation of delaminations and burrs. The tilted planetary motion drilling has been demonstrated by the practical fundamental drilling experiment by use of a high-speed spindle unit and a lathe as imitating tilted planetary motion. From the experimental result, capability of tilted planetary motion drilling has been realized and no burrs and delaminations are observed on the workpiece. © 2012 The Authors.

This study deals with automation of metal hammering forming on the basis of CAD data by use of a linear motor. The metal hammering is one of traditional handicrafts. An objective shape is pulled into shape as integration of discrete deformations on each hammered part. In order to automate the metal hammering working that has been operated by human handwork conventionally, following approaches are adopted in the study. To improve these workings with numerical control, the tool path is generated on the basis of CAD data. To imitate skilled human worker's hammering, the hammering mechanism by using of a linear motor is developed. Linear motor can perform linear motion with smooth arbitrary acceleration and precise position control and hammer motion. Hammering motion of the liner motor is controlled by the internal model control method and optimal control method. From the experimental result, the developed system is realized to have enough ability to form various shape of workpieces and the linear motor hammering improve the formability of the system. © 2012 The Japan Society of Mechanical Engineers.

The study deals with forging type rapid prototyping system that automates metal hammering done by an industrial robot. In order to automate metal hammering work, a CAD/CAM system is required to define product shapes and generate tool paths. However, the hammering process differs from the cutting process in that the hammering errors accumulate. Thus, unsuitable work methods threaten to cause both deterioration of work accuracy and sheet metal fractures. However, the relationship between the effects of errors and hammering results has not yet been fully defined. Hence, in this report, the effects of hammering direction on product shape is taken up to make these relationships clear, and a method to improving work accuracy is proposed in order to reduce the potential source of errors. Finally, the usefulness of the devised method is confirmed experimentally.

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.

The study deals with burnishing tool wear and its lifetime, which Is made of Single Crystalline Diamond (SCD). The burnishing process Is one of a microplastic working, which a spherical diamond point tool compresses the metal surface to obtain a mirror-like surface roughness; it could improve surface layer hardness similarly to the shot-peening process. Although the SCD burnishing process Is widely used, tool wear phenomenon and tool lifetime have not been fully made clear. In order to ensure Its practical conditions, certain way of tool lifetime estimation would be required. Through the above-mentioned background and some fundamental experiments on the burnishing condition using an NC lathe, we set the objective of this study as to estimate the lifetime of diamond burnishing tool under its optimum condition. The worn surface of diamond burnishing tool and workpiece surface finish were investigated from a surface engineering point of view. From the experimental result, the burnishing tool surface texture was transcribed on workpiece surface. Estimation method for lifetime of diamond burnishing tool is suggested. © 2011 Wiley-VCH Verlag GmbH & Co. KGaA. Weinheim.

<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.

Chamfering is an essential process after machining for almost all machined workpieces to control products' appearance. Usually, workpieces having simple shapes can be chamfered by an automatic chamfering machine. However, complicated shaped workpieces are obliged to chamfer with handwork because of their intricacy. Especially, products made by sand mold casting have dimensional errors. The chapter focuses on the automation of chamfering without the influence of dimensional error piece by piece. Generally, products made by casting have dimensional error. A cast impeller, used in water pump, is treated in the study as an example of the casting product. The impeller is usually chamfered with handwork because it has individual dimensional errors. In the system, a diamond file driven by air reciprocating actuator is used as a chamfering tool and image processing is used to compensate the dimensional error of the workpiece. The robot hand carries a workpiece instead of a chamfering tool, both for machining and for material handling. © 2006 Elsevier Ltd. All rights reserved.

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>