Keiichi Nakamoto

Prototyping of Autonomous CNC Machine Tool Based on Digital Copy Milling Concept

A prototype of CNC machine tool which realizes autonomous milling operation was developed. The machine tool developed is controlled by the digital copy milling concept. In the digital copy milling concept, a tracing probe and a master model in traditional copy milling are represented by 3D virtual models, and cutter locations are generated dynamically according to the motion of virtual tracing probe in real time. Therefore, not only feed speed, but also radial and axial depths of cut can be adapted for milling process control. Also, new tool paths can be added to avoid and recover from cutting troubles without any NC program. In the experimental tool crash condition, the cutting tool was successfully retracted to avoid tool breakage.

Development of a circular vibration milling attachment and its application to machining of hardened steel

It has been proven that vibration-assisted machining can improve finished surface quality of hard materials and reduce tool wear. In previous researches, a prototype milling machine was developed to investigate the feasibility of vibration-assisted milling process. In this research, a device that can be attached to any machining centre to perform circular vibration milling was developed and its performance was investigated. The device is used to vibrate a cutting tool along a circular locus about the machine tool spindle axis, in addition to tool rotation motion. Experimental results showed that by using the circular vibration milling attachment, the finished surface quality of hardened steel can be improved and tool wear can be reduced compared with conventional milling process.

Proposal of a concept of future oriented machine tools for advanced manufacturing systems

In order to satisfy the recent various consumers’ needs, an advanced manufacturing system will be required. So, the innovative concept of Future Oriented Machine Tools (FOMT), which consists of four function blocks to realize the advanced manufacturing system, is proposed. The four function blocks are Management, Prediction, Observation and Strategy, and intelligent manufacturing processes are realized by utilizing these function blocks. FOMT can make a significant contribution in four stages: design stage, production scheduling stage, machining stage and post-machining stage. In the design stage, the product information such as accuracy can be evaluated in CAD, considering the manufacturing ability concurrently. In the production scheduling stage, the product schedules can be generated automatically and flexibly for the various products. In the machining stage, cutting conditions adjusted autonomously according to the machining status and machining problems. In the post-machining stage, the machining know-how data are accumulated and stored for future production and human engineers. The feasibility of it, especially the machining stage, is discussed using the developed cutting process simulator called VMSim (virtual machining simulator) from the view points of cutting force, machining error and environmental burden (CO2 emission).

Proposal of Real-Time Balancing mechanism Using Magnetic Fluid for Machine Tool Spindle

Spindle vibration of machine tools causes premature tool wear and deterioration of machining accuracy. However, the vibration changes depending on the used tooling system and the rotational speed during various machining operations. In this study, a smart spindle with a real-time balancing mechanism using a magnetic fluid is proposed. The magnetic fluid is enclosed inside the rotational part, and the distribution of the circumferential fluid mass is actively controlled. A test spindle with the real-time balancing mechanism was designed and developed. The experimental results proof the feasibility of the proposed real-time balancing mechanism for achieving high accuracy and efficiency machining.

A New Architecture of Tool Path Generation for Five-Axis Control Machining

NC machine tools, which are widely employed in manufacturing systems, are basically driven by NC programs. However, it requires extensive amount of time and efforts to generate high quality tool paths before a machining operation. An NC program for five-axis control machining is more difficult to generate because the motion of machine tool is more complicated. In this paper, a new architecture is proposed to autonomously control the machine tool without an NC program for more rapid and flexible machining. A technique called digital copy milling is developed to generate the tool paths in real time based on the principle of copy milling. It means that the cutting parameters can be adaptively controlled in order to maintain stable cutting process and to avoid the cutting troubles. In the experimental verification, the improved digital copy milling system for five-axis control milling successfully detected and avoided tool collision in real-time.

Ultra-Precision Finishing of Micro Aspherical Surface by Ultrasonic Vibration Assisted Polishing

Micro axis-symmetric aspherical glass lenses are being increasingly used in digital devices and optical devices. The glass lenses are molded by using micro ceramic dies such as tungsten carbide [1].Recently, as the pixel number of digital image sensors increases, the accuracy of micro molding dies are required to be much more precise than ever [2]. In this study, ultrasonic assisted polishing method is proposed and developed in order to finish micro axis-symmetric aspherical dies which were pre-ground with a diamond wheel [3]. In this paper, the proposed polishing method was applied to the micro aspherical molding dies to finish form compensation processing.

Development of an innovative autonomous machine tool for dynamic product planning

Abstract In the area of machining, laborsaving and automation are comparatively realized mainly by the contribution of NC machine tools so far. However, conventional NC machine tools are not autonomous and intelligent because they don’t have any feedback mechanisms during machining operations. Therefore, in order to realize dynamic product planning for an innovative autonomous machine tool, it is indispensable that machine tools have feedback mechanism to adapt cutting parameters to monitoring information. As a matter of course, it is needed for the mechanism to include a function of tool path generation in real time. Because the real time tool path generation can perform to change not only feed speed but also depth of cut during an operation. In this paper, digital copy milling system that can generate tool paths in real time is developed by applying the traditional copy milling principle. And also, machining strategy is proposed to adapt cutting parameters considering cutting load, and integrated into the digital copy milling. Feedback machining control can be realized using the digital copy milling system with the proposed machining strategy. Furthermore, in order to achieve dynamic product planning, an automatic function of product planning is added by customizing commercial CAD software. By using this automatic planning system, even in case of a cutting trouble, it is possible to reschedule product planning immediately. Autonomous machining based on dynamic product planning can enable to realize high flexibility and high durability in machining operations.