Keiichi Shirase

• PhD
• Professor (Full) at Kobe University

In end milling operations, the tools are exposed to high temperatures and high pressures, which inevitably causes the tool wear progress. It is well known that the tool wear progress strongly depends on the temperature of cutting edge. In this study, the thermal analysis to predict cutting temperature is performed by modeling heat transfer, heat in...

This study developed a voxel-based method to simulate machining error caused by elastic deformation of the tool and workpiece in end milling. The tool and workpiece shapes are represented by a set of cutting edge points and a voxel model, respectively. The cutting force is calculated based on the collision state between the cutting edge points and...

In mass production, the tool life of cutting tools is generally controlled by the number of parts to be machined and the machining time, making it difficult to operate each tool to its full life. In addition, it is desirable to avoid tool changes due to tool life during machining in order to avoid an increase in machining setup time. This study pro...

Numerical control (NC) is one of the greatest innovations in the achievement of machine tool automation in manufacturing. In this chapter, first a history of the development up to the advent of NC machine tools is briefly reviewed (Sect. 35.2). Then the machining centers and the turning centers are described with their key modules and integration i...

This study proposes a method for automating the determination of assembly order by automating the derivation of the necessary connection relationships between the parts. The proposed method minimizes the information required for the initial conditions and automatically determines the feasible assembly orders. As a general rule, based on the assumpt...

This study aims to establish a simple method for determining tool replacement timing based on tool wear progress. First, the relationship between machining conditions and tool wear progress was investigated via dry cutting experiments conducted using a 8.0dia. cobalt high-speed steel square end mill as the tool and a piece of SS400 steel as the wor...

The contact between a tool and workpiece during machining has a significant effect on the vibration characteristics of machine tools. This study proposes a method for detecting contact between a tool and workpiece, and demonstrates applications of the detection. To detect the contact between the tool and workpiece, this study used the change in the...

A new method to analyze the elastic deformation of a workpiece during end milling is proposed. One of the advantages of this method is the possibility of easily combining it with a voxel-based milling simulation, which is often used to predict cutting force, and to predict machining error due to workpiece deflection. With this method, the workpiece...

In order to solve the labor shortage in manufacturing sites, full automation of machining, including NC program generation and other setup work, is required. In this study, an automatic cutting condition determination system was developed to achieve fully automated NC program generation. The cutting conditions that served as the teacher data were t...

This paper presents a simulation method for the power consumption of servo motors, focusing on the influence of vibrations on the motor efficiency. An apparatus consisting of two servo motors connected through a coupling was specifically designed for this study. The efficiency of the servo motor was experimentally investigated for several torque vi...

“The digital transformation can be understood as the changes that the digital technology causes or influences in all aspects of human life” (definition by Prof. Erik Stolterman). In order to manufacture high value-added products and create a sustainable society, the digital transformation, based on advanced precision engineering, will be an urgent...

In this study, the influence of mechanical vibration characteristics on the efficiency of a servo motor was experimentally investigated. For this purpose, a dedicated apparatus comprising two servo motors connected to a coupling was used. The efficiency of the motor was investigated by first considering the signals of voltage and current; then, the...

The positioning operation of axes is essential before initiating machining operations in NC machine tools. Residual vibration following the positioning operations of the axes deteriorates the cycle time and quality of the machined parts. The purpose of this study is to establish a design method for positioning commands that reduces the residual vib...

In end milling, proper tool life management is crucially important for achieving highly accurate machining, avoiding tool failure, and optimizing production costs. In recent years, a number of tool condition monitoring (TCM) methods aimed at improving tool life management have been proposed. However, these methods have generally been impractical, a...

Articulated robots are widely used in industries because they can perform manufacturing tasks with complicated movements. Higher speed and accuracy of motions are always required to improve the quality and productivity of products. The vibration characteristics of the robots are an important factor to achieve higher speed and accuracy motions. Robo...

Coupling characteristics that depend on the applied torque and the influence of this torque dependency on the system response are investigated in this study. A dedicated apparatus, consisting of two servomotors connected by a coupling, was specifically designed for this purpose. To measure the frequency response of the apparatus, a sweep signal wit...

A method to extract the machining region from 3D CAD model in STL (Standard Triangulated Language) format and automatically generate tool path is proposed. At first, this study proposes a method to extract the machining region and obtain the geometrical feature such as convex shape or concave shape from only the 3D CAD model in STL format. The STL...

A cubic-machining test has been proposed to evaluate the geometric errors of rotary axes in five-axis machine tools using a 3 × 3 zone area in the same plane with different tool postures. However, as only the height deviation among the machining zones is detected by evaluating the test results, the machining test results are expected to be affected...

A method for extracting the machining region from a 3D CAD model in Standard Triangulated Language (STL) format and automatically generating a tool path is proposed. First, a method is proposed for extracting the machining region and obtaining the geometrical features such as a convex or concave shape from only the 3D CAD model in STL format. The S...

Evaluating the influence of geometric errors in rotary axes is a common method used by a five-axis machine tool for improving the machining accuracy. In conventional geometric error models, the table coordinate system is considered as the final workpiece coordinate system. In this study, an additional workpiece coordinate transformation was propose...

The positioning operation of the axes of numerically controlled (NC) machine tools is essential before initiating their machining operation. Residual vibration following the positioning operations of the axes deteriorates the cycle time and quality of the machined parts. This study aims to develop a novel acceleration and deceleration design method...

Contact between the tool and the workpiece during machining has a significant effect on the vibration characteristics of the machine tools. In this study, contacting rate is defined as the contact time per unit time based on the detected contact between the tool and workpiece during the excitation tests, and relationship between the contacting rate...

The purpose of this study is to propose a practical tool condition monitoring method in end milling operation. In the proposed method, real-time cutting force simulation is performed in parallel with actual milling operation. The tool condition is recognized by comparing the spindle motor torque, which can be monitored through CNC without additiona...

This study proposes an evaluation method for the coupling characteristics based on the measured frequency function. Stiffness and damping can be identified from the resonance frequency and maximum vibration amplitude at the resonance frequency, respectively. Characteristics of various types of coupling; leaf-spring type couplings and a resin type c...

It is expected that the vibration characteristics of NC machine tools are affected by the contact between tool and workpiece during the cutting operations. However, the influences of the contact have not been clarified up to now. This study investigates the influence of contact between tool and workpiece onto vibration characteristics of machine to...

A method to calculate tool path uniquely for roughing using a flat drill is proposed. A flat drill is a drill with a flat tip. Unlike a square end mill, it cannot feed a tool laterally, but it is suitable for machining to feed a tool longitudinally. The advantage offered by the flat drill is expected to reduce machining troubles, such as tool break...

Cutting force is one of the most important information in order to know machining process and optimize cutting conditions in end milling. An external sensor like a dynamometer is widely used to measure cutting force in the most researches. However, using a dynamometer is inadequate to measure cutting force practically in factories. Thus, the sensor...

Several methods have been proposed to detect tool wear in milling operation using AE (Acoustic Emission) signals or cutting force signals. However, these methods require additional sensors such as an AE sensor or a dynamometer, which incurs additional costs. For this reason, a simple tool life estimation method based on machining time is used. In t...

It is expected that the vibration characteristics of NC machine tools are affected by the contact between the tool and the workpiece during the cutting operations. However, the influences of the contact have not been clarified up to now. In this study, a method to evaluate the contacting effect and evaluated results are described. Frequency respons...

Motion error of machine tool feed axes influences the machined workpiece accuracy. However, the influences of each error sources are not identical; some errors do not influence the machined surface although some error have significant influences. In addition, five-axis machine tools have more error source than conventional three-axis machine tools,...

A method to automatically calculate tool paths and apply to machining from near net shape material is proposed. At first, this study proposes a contour line model, in which the product model is minutely divided on the plane along any one axial direction and the contour lines to show the cross section of the product is superimposed. Subsequently, th...

A new methodology to assess and adapt cutting conditions for machining operation planning is proposed in this study. In order to automate machining operation planning, the method to reuse cutting conditions in the past previous machining operations has been proposed in the previous study. However, the assessment and adaptation of cutting conditions...

This study presents an experimental analysis of the power consumption of feed drive systems. The relevant system components from the power consumption point of view are the motor, bearings, ball-screw and linear guides. The electric power consumption of the motor is investigated experimentally acquiring the inputted voltage and the current; then, t...

While evaluating the accuracy of high-precision machine tools, it is critical to reduce the error factors contributing to the measured results as much as possible. This study aims to evaluate both the error motions and geometric errors of the rotary axis without considering the influence of motion error of the linear axis. In this study, only the r...

A method to uniquely calculate the tool path and to modify the tool path during air cutting motion to reduce the machining time is proposed. This study presents a contour line model, in which the product model is minutely divided on a plane along an axial direction, and the contour line of the cross-section of the product is superimposed. A method...

An experimental analysis of the mechanical and electrical power consumption of feed drive systems is presented in this paper. The main components affecting the power consumption are the motor, bearings, ball-screw, and table. The power consumption of the motor has been investigated experimentally through the study of the electrical efficiency. The...

The present paper proposes a model of muscle fatigue and recovery considering both the behavior of slow- and fast-twitch muscle fibers and the role of antagonistic muscles. The proposed model can be used to predict the degree of muscle fatigue of each muscle in the upper arm when the muscle activation pattern of the muscles changes because of the v...

The purpose of this study is the experimental investigation of the power consumption of each relevant component of a feed drive system; the electric efficiency map of the servo motor has been measured along with the power consumed by each component of the feed drive; specifically, 4 ball-screws differing by the lead of the screw and the preload con...

A contour line model for end milling simulation, which realizes high-speed arithmetic processing by reducing memory usage, is proposed. In this model, a 3-dimensional shape can be expressed by superimposing the contour lines of the cross-sections obtained by dividing the workpiece along any axial direction. Therefore, the memory usage is reduced co...

In this study, we describe a novel mechanical vibration suppression method for high-speed contouring motions. In this method, vibration compensation torque was applied to suppress mechanical vibrations during high-speed contouring motions. The parameters of the compensation signal were determined using commanded acceleration and time for accelerati...

In order to design a feed drive system that performs high-speed and high-precision motion, it is necessary to correctly understand the influence of each mechanical element that constitutes the feed drive mechanism on the characteristics of the entire feed drive system. Therefore, in this study, in order to evaluate the rigidity of the support beari...

To realize autonomous machining, it is necessary to focus on machining tools and also on the automation of process planning in the preparation stage. This study proposes a process planning system that automatically defines the machining region and determines the machining sequence. Although previous studies have explored computer-aided process plan...

Five-axis machine tools, which combine three linear axes and two rotary axes, are required for accuracy in machining complex shapes. In this paper, to clarify the influence of simultaneous three-axis control motion measurements as specified in ISO 10791-6, the measured results using a ball bar and R-test are compared. As the motion trajectories of...

A higher machining ability is always required for NC machine tools to achieve higher productivity. The self-oscillated vibration called “chatter” is a well-known and significant problem that increases the metal removal rate. The generation process of the chatter vibration can be described as a relationship between cutting force and machine tool dyn...

The present study proposed a method to automatically generate a numerical control (NC) program by referring to machining case data for each machine tool with only 3D-CAD models of a product and workpiece as the input data, and to select machine tools for machining the target removal region among several machine tools with different characteristics....

As the motion accuracy of 5-axis machining centers directly influences the geometrical shape accuracy of the machined workpieces, accuracy enhancement of the 5-axis machining centers is strongly needed. To improve the shape accuracy during the machining by a 5-axis machine tool, a method that modifies the CL-data based on the motion trajectory erro...

To improve machining efficiency, it is necessary to know the machining status and optimize cutting conditions. Cutting force prediction is one method of determining the machining status. The instantaneous rigid force model is widely used and can be easily applied to cutting force prediction. However, this model requires six parameters called cuttin...

Five-axis machine tools, consisting of three translational axes and two rotary axes, are increasingly being used for complex surface machining. This paper proposes a new sensitivity analysis method to elucidate the relationship between the tool trajectory error and the error motions of the feed axes. Based on the free-curve trajectory during simult...

The prediction of muscle forces is very important in order to evaluate the physical loads during human motion. Although a number of musculoskeletal models, which can predict muscle forces during motion, have been proposed, these models use the optimization method, in which the sum of the predicted muscle forces is minimized. However, unfortunately,...

Five-axis machining center, combined three linear and two rotary axes, has been increasingly used in complex surface machining. However, as the two additional axes, the machined surface under table coordinate system is usually different from the tool motion under machine coordinate system, and as a result, it is very tough to predict the machined s...

On-machine measurement (OMM) is introducing to Numerical Control (NC) machine tools. By the OMM, a workpiece is measured on the machine tool (i.e., without loading and unloading), so OMM can reduce the setup time and positioning error for reloading a workpiece. OMM is used for the process control during machining because it is still difficult to su...

According to the change of manufacturing style from mass production to customized production, it is important to manage the process plan and to control the machining quality of products. On machine measurement (OMM) has an advantage that it eliminates the operations of remove and reattachment of the workpiece and eliminates the positioning error at...

A new methodology to generate instruction commands for prompt machine control as a replacement for the previously prepared numerical control (NC) programs is developed to realize an innovative intelligent machine tool. This machine tool can eliminate NC program preparation, achieve cutting process control, reduce the production lead time, and reali...

The present paper proposes a new model of muscle fatigue and recovery considering the roles of slow twitch (ST) and fast twitch (FT) muscle fibers. The proposed model can predict the variation in the degree of muscle fatigue because it considers the properties of muscle fatigue and recovery, which have been neglected in previous models. The aim of...

In order to realize autonomous machining, it is necessary not only to automate the preparation tasks for machining but also to verify the machining results during the process. Therefore, this study realized the automation of planning for on-machine measurement, where measurement is conducted at the necessary time during the machining process based...

A machining error correction, which is based on the predicted machining error caused by elastic deflection of tool system, is proposed. This method is based on an instantaneous force with static deflection feedback model which is classified to consider the milling process representation. The uncut chip thickness, which is required to predict cuttin...

Conventional musculoskeletal model often uses the optimization method to estimate muscle forces. However, the optimization method unfortunately does not usually consider the role of antagonistic muscles, which act in opposite direction to the prime motion or for restriction of rotational joint motion. Therefore, this study proposes a new method to...

A key concept of production management is proposed to achieve adaptive and flexible manufacturing supported by highly automated production resources such as autonomous machine tools, robots and so on. In the present research, heterogeneity in process planning is remained to select an appropriate options in scheduling. This paper clarifies the advan...

During the cutting operations, it is expected that the vibration characteristics of the entire machine tool are influenced by the process damping and contacting stiffness due to the contact between the tool and the workpiece. In this study, excitation tests were carried out by using the motor torque command in the feed drive system. The frequency c...

Feed drive systems are widely used in the industrial field, especially in manufacturing. It is effective to analyze the vibration characteristics of the system to make an optimum mechanical and control design. From this point of view, several simulation techniques have been proposed and applied to the design in the field. One of the most popular me...

A new methodology to generate instruction commands for real-time machine control instead of preparing NC programs is developed under the CAM-CNC integration concept. A machine tool based on this methodology can eliminate NC program preparation, achieve cutting process control, reduce production lead time, and realize an autonomous distributed facto...

In this study, an automatic process planning system for milling operation is proposed, in which user's intention for process planning is considered. First, our new process planning system stores the geometrical properties of the selected machining region when a user decides the machining sequence. After storing the geometrical properties, the appro...

This paper describes an automation system to realize autonomous sheet metal bending operation by industrial robot. This system can derive bending sequences using topological information in a CAD model of a sheet metal product, and can generate operation paths to control an industrial robot in consideration of its positions and configurations.

In this study, autonomous end milling system for manufacturing custom-made dental prostheses was developed. This system can decide suitable machining orientation of dental prostheses to minimize unmachined volume automatically, and can prevent tool breakage by tool feed rate control based on the predicted cutting forces in end milling operation.

In this study, the automated process planning system for end-milling operation is realized. This study considers to minimize the number of times of tool change and to determine the appropriate machining sequence in the process planning. In our previous process planning system, the machining sequence is calculated geometrically, based on the Total R...

The motion trajectories of machine tools directly influence the geometrical shape of machined workpieces. Hence, improvement in their motion accuracy is required. It is known that machined shape errors occurring in numerical control (NC) machine tools can be compensated for by modifying the CL-data, based on the amount of error calculated by the me...

This study proposed a new method to automatically determine cutting conditions for NC program generation by utilizing the similarity of the removal volume extracted from a work material. In the new method, the cutting conditions associated with the geometric properties of the removal volume, which is extracted from work material shape and product s...

In order to achieve both high precision and high productivity in machining operation, machining error compensation of finished shape named as correction machining is more effective. In general, the correction machining requires additional CAD/CAM operations to generate the NC program for the correction machining, and it takes lots of time and effor...

A new method, which accurately predicts cutting force in ball end milling considering cutting edge around center web, has been proposed. The new method accurately calculates the uncut chip thickness, which is required to estimate the cutting force by the instantaneous rigid force model. In the instantaneous rigid force model, the uncut chip thickne...

Motion accuracy of NC machine tools is directory copied onto the machined shape. However, it is known that the motion accuracy is deteriorated by several error courses; geometric and dynamic motion errors of feed axes. In this study, in order to enhance the motion accuracy of NC machine tools, a method that modifies the NC program based on the norm...

S-shaped machining test is proposed for ISO standard to evaluate the motion accuracy of five-axis machining centers. However, it have not been investigated that which factor mainly influences the quality of the finished S-shape workpieces. This study focuses on the influence of the quality of NC program and geometric errors of rotary axes onto the...

In order to improve machining efficiency, it is required to recognize machining status and optimize cutting conditions. This study develops a newly cutting simulator for end-milling operation, which considers the elastic deflection of tool system. This simulator is based on an instantaneous rigid force model. The uncut chip thickness, which is requ...

In this study, an automatic process planning system for end-milling operation is proposed, in which CAM operator's intention for process planning is considered. In the previous process planning systems, the machining sequence is calculated geometrically, based on the Total Removal Volume (TRV) and the machining region split from TRV. However, it re...

An S-shaped machining test is proposed for the ISO 10791-7 standard to verify the performance of five-axis machining centers. However, investigation of the factor that has the most influence on the geometrical accuracy of finished S-shaped workpieces has not been undertaken. Determination of the influence of NC program tolerance and geometric error...

This study proposes an identification and compensation method for the geometric errors of the rotary axes in five-axis machining centers, based on the on-machine measurement results of the machined workpiece. Geometric errors can be identified from the shape geometry of the workpiece machined by five-axis motions because the influence of the errors...

In order to improve machining efficiency, it is required to recognize machining status and optimize cutting conditions. Cutting force is meaningful information to recognize machining status. In the instantaneous rigid force model, which is the most popular model for milling force prediction, milling force is calculated based on the geometrical inte...

In end milling operations, undesired tool approach marks may occur due to the tool deflection by transient cutting force change in the tool approach motion. The tool approach marks have a particularly big influence on the machined surface quality in case of the smooth and continuous surfaces are highly required. Therefore, in this study, a method t...

In this study, a virtual milling force monitoring method is proposed for industrial milling process monitoring. For this purpose, a modified instantaneous rigid force model is proposed. Oblique and orthogonal cutting theories are applied in the model to reduce the number of cutting parameters required for milling force prediction. Only the shear an...

In this study, a novel end milling operation cutting simulator that considers the static tool deflection was developed. This simulator is based on an instantaneous rigid force model. In this model, the uncut chip thickness, which is necessary to estimate the cutting force, is calculated based on the static tool deflection, which consists of the def...

This study investigates the vibration isolation effect of rubber sheets under machine bed supports in a vertical type machining center. It is known that the stiffness and dumping of the machine bed supports influence the dynamic characteristics of the machining center, and the rubber sheets are often applied under the machine bed supports to isolat...

Appearance quality of the products is an important issue especially in the molds, dies and designed surfaces. However, the geometrical shape error of machined surface and the appearance quality are not identical due to human visual characteristics. Previous studies had clarified that the derivative of normal vector of machined surface is related to...

In this study, the automated process planning system for end-milling operation is realized. This study considers to minimize the number of times of tool change and to determine the appropriate machining sequence in the process planning. The previous process planning systems do not consider to realize reasonable operation planning in the determinati...

The S-shape machining test, proposed to ISO standard as an amendment, is expected to be a test to evaluate the accuracy of five-axis machine tools. However, there are few research works achievements done to investigate the influence caused by dynamic errors. This study is focused on the S-shape machining accuracy in different dynamic conditions, wh...

Since motion accuracy of 5-axis machining centers directly influences the geometrical accuracy of the machined workpieces, accuracy enhancement of the 5-axis machining centers is strongly demanded. In order to improve the geometrical accuracy during the machining by a 5-axis machining centers, a method that modifies the CL-data based on the trackin...

In end milling, in order to improve machining efficiency and accuracy, instantaneous rigid force model is widely used to predict cutting force and improve cutting conditions. The instantaneous rigid force model is well known as the practically simple model to predict cutting force. However this model requires the six parameters called cutting coeff...

This study aims to develop a monitoring system, which can automatically detect tool wear in end-milling operation. A feature of this system is the utilization of the predicted cutting torque for detecting the difference between normal and cutting trouble. The cutting torque predicted by a cutting force simulator is compared with the cutting torque...

A new cutting force simulator has been developed to predict cutting force in ball end milling. In this simulator, uncut chip thickness is discretely calculated based on fully voxel models representing both cutting edge and instantaneous workpiece shape. In the previous simulator, a workpiece voxel model was used to calculate uncut chip thickness un...

It is known that the cutting force excites the structural vibration of machine tool. In addition, cutting force acts on feed and spindle drive system as a force disturbance, and feed speed and spindle speed are changed. As the results, cutting force is also changed because the depth of cut and cutting speed are changed due to the machine vibration,...

Several methods for evaluating the motion accuracy of the rotary axes of five-axis controlled machining centers have been proposed up to now. Since it is known that particular motion errors exist around motion direction changing points, it is important to evaluate the behavior of the rotary axes around these points. In this study, the characteristi...

Energy consumption of numerical control (NC) machine tools is one of the key issues in modern industrial field. This study focuses on reducing the energy consumed by a five-axis machining center by changing only the workpiece setting position. Previous studies show that the movements along each axis in five-axis machining centers depend on the work...

In this study, we propose a new process planning system for machining operations, one which considers user strategies and intentions for such operations. In previous process planning systems, the machining sequence is calculated geometrically, based on the Total Removal Volume (TRV) and the machining primitive region split from TRV. However, it rem...

A new cutting force simulator has been developed to predict cutting force in ball end milling. This new simulator discretely calculates uncut chip thickness based on a fully voxel representation of the cutting edge and instantaneous workpiece shape. Previously, a workpiece voxel model was used to calculate uncut chip thickness under a complex chang...

Energy consumption of numerical control (NC) machine tools is one of the key issues in modern industrial field. This study focuses on reducing the energy consumed by a five-axis machining center by changing only the workpiece-setting position. Previous studies show that the movements along each axis in five-axis machining centers depend on the work...

A new method of the process planning for end-milling operation considering product design constraints in this study. In our previous study, the process planning system, in which the Total Removal Volume is divided by the planes parallel with the XY, YZ or ZX planes to analyze machining sequence from top to bottom of the target product, is proposed....