This paper presents the results of detailed thermal analysis of a 5-axis machine tool with focus on the rotary axes. The rotary axes are characterized regarding their position and orientation errors as a function of the underlying thermal load, contributing significantly to the overall accuracy. A physical model is presented, which allows the simulation of the thermal behavior of the rotary axes based on the power input to the drives of the rotary axes and the heat conduction in a swiveling rotary table unit and convection into environment. This enables an external online-compensation of thermal errors. The compensation model is verified and validated.
Recently, three-dimensional microstructures have been attracting much attention because of their potential application to electromagnetic devices operating with specific frequencies such as THz wave. For suitability in such applications, the structures often need to have complex three-dimensional shapes, be smaller than or at least as small as the applied wavelengths, consist of metals or dielectric materials, and have certain electromagnetic characteristics such as high permittivity. Although there are several methods for fabricating micro-structures, few of them satisfy all of these conditions. We propose a new fabrication method for dielectric-metal three-dimensional structures with sizes of a few tens of micrometers. The main feature of our method is the extraction of metal using photocatalyst nanoparticles. Silver ions in solution are reduced to neutral silver by electrons from the photocatalyst nanoparticles. Experimental results show that our system can be used to fabricate three-dimensional structures, and we propose a new method for controlling the composition of the structures.
The machining accuracy of ultra-precision machine tools relies on the performance of the spindle and linear table. The machining accuracy of ultra-precision machine tools is now at the level of several tens of nanometers. In order for ultra-precision machine tools to achieve machining accuracy, a precise spindle system is indispensible. High bearing stiffness is particularly important to minimize displacement due to the cutting force. This paper considers a spindle design supported by high-stiffness water hydrostatic thrust bearings. An objective of this study is to design a precision spindle supported by water hydrostatic thrust bearings with 1 kN/μm bearing stiffness. The bearing restrictors are chosen so that the highest stiffness can be obtained for given bearing parameters. The influences of gap sizes and supply water pressure on the bearing stiffness are presented. Based on the feasibility study done on the design of high-stiffness water hydrostatic thrust bearings, the spindle is designed and developed. The influences of the water pressure on the spindle deformation and bearing stiffness are also investigated.
In this paper, a method to Control a Manufacturing Cell by Driving Simulation Models (CMC-DSM) is proposed. The purposes of CMC-DSM is not only to directly operate the manufacturing cell while controlling and monitoring the manufacturing cell based on a simulation model in the manufacturing system execution phase, but also to support the manufacturing engineering processes based on the simulation model. In the manufacturing engineering processes, the simulation model is mixed and synchronized with real equipment and management applications in the case where parts of equipment and manufacturing management applications are not provided in the manufacturing cell. In the manufacturing system execution phase, when the simulation model acts in response to manufacturing system behaviors, the manufacturing system is controlled by synchronizing the simulation model behaviors. In this paper, the Environment required to Control a Manufacturing Cell by Driving Simulation Models (E-CMC-DSM) is proposed. The necessary functions for E-CMC-DSM are defined and developed. E-CMC-DSM consists of a simulator developed to drive simulation models (EMU), a soft-wiring system developed in this study, and a semi-standard industrial network middleware. The validation of E-CMC-DSM was carried out through a case study.
This study investigates the contributions of high-speed cutting and a high rake angle to the improvement of the cutting performance of natural rubber. Orthogonal cutting experiments were conducted at cutting speeds ranging from 1.0 m/s to 141.1 m/s. The rake angles examined were 0°, 20° and 50°. The following results were obtained from the experiments. The cutting ratio is almost 1.0 regardless of the cutting speed and rake angle. The cutting force rises rapidly as the cutting speed increases. High-speed cutting or a high rake angle eliminates tear defects on the machined surface and reduces chipping defects at the entry edge of the workpiece. An uncut portion, however, always remains at the exit edge. The cross-sectional shape of the machined surface becomes concave. Besides, the machined surface comes into broad contact with the clearance face. These degradations in the shape accuracy arise from the large elastic distortion that occurs in the shear zone. Increasing the cutting speed improves the flatness of the machined surface. Although an analysis of the cutting mechanism reveals that the apparent stiffness of the material in the shear zone is enhanced with increasing the cutting speed, a very high cutting speed worsens the shape accuracy because of the development of shock waves. Depending on the rake angle, there is a critical cutting speed that should not be exceeded to maximize the cutting performance of natural rubber.
Discharge duration and pulse frequency are studied to determine the optimum conditions for creating a single crater. In addition, the relationships between pulse frequency and surface characteristics using Whirling Electrical Discharge Texturing (WEDT) are determined. It is confirmed that the texture-area ratio and the total removal volume of craters, but not crater diameter or crater depth, can be controlled by adjusting pulse frequency. Moreover, after honing, surface characteristics decrease owing to the removal of protrusions. With honing, the surface roughness of the textured surface leads to a reduced friction coefficient as expected.
The objectives of this paper are to describe a quantitative evaluation of mini-size diamond grinding wheel surface topography in Ultrasonic Assisted Grinding (UAG) process and demonstrate the effects of topography on grinding characteristics. In this study, three-dimensional (3D) analysis of the wheel working surface was observed using a Scanning Electron Microscope (SEM) with four electron probes (hereafter described as 3D-SEM) in an on-surface UAG process. These results indicated that a good wheel surface maintained in the UAG process is related to the number and the area of cutting edges. Additionally, the resulting topographic features of the grinding wheel surface are closely related to low grinding forces and allow easy manufacturing of a mirror workpiece surface.
Recently, fixed abrasive technologies have been needed to solve some problems with free abrasive technologies, such as processing efficiency and environmental pollution. Plane honing is one effective fixed abrasive technology for processing wafer-like materials. Advantages of plane honing include a high processing rate, slurry waste-free process, and high finishing accuracy. The paper presents a method to simulate the plane honing process based on statistical analysis of a grinding process. One of the most significant differences between grinding and plane honing is process controlling method: the former is position-controlled, whereas the latter is pressure-controlled processes. In order to treat a pressure-controlled process, the amount of material removed from each segment was assumed to be constant based on Preston’s law, which is the most common principle for material removal in the polishing process. Reference curves of a segment were introduced to map tip points of abrasive grains contained in the segment. The reference curve can be compared with the surface curve of the workpiece to determine the material to be removed; repeating the comparison allows the plane honing process to be simulated. Plane honing experiments were conducted, and the results agreed qualitatively with the simulation results.
Remotely Operated underwater Vehicles (ROVs) equipped with manipulators have increasingly been used for underwater operation. An ROV is usually operated manually with the aid of an underwater camera for approaching and grasping a target using its manipulator. Owing to the low quality of underwater imaging, it is quite difficult for the human operator to determine accurate distances and orientations between the ROV and the target of interest. This paper presents a proposal for developing an automatic three-dimensional measurement and guidance system for ROVs in an effort to facilitate this process. Based on optical triangulation principles, dual laser lines and a camera are utilized to calculate the position and orientation of a cylindrical target. A measurement model considering refraction compensation and a joint system calibration method are proposed. The experimental study shows that the proposed system is feasible for automatically determining the position and orientation of a cylindrical target in an accurate and efficient manner. The accuracy of the measurement system is verified in air and underwater, respectively, by a prototype system.
To investigate basic polishing properties of fixed abrasive polishing using alumina abrasive grain for Si wafer, we used a pyramidal structured polishing pad having alumina abrasives and aqueous KOH solution as the polishing fluid. We clarified that the optimum KOH solution concentration required to get a smooth surface 5 wt% and finished surface roughness of 80nmRz. The cutting edge was hardly worn and polishing performance was maintained without dressing.
Automation via the internet has recently received considerable attention. The prime objective of internet-based process automation underlies, among many others, the feasibility of remote monitoring and control of a wide range of distributed and collaborative experimental and manufacturing tools and machineries. Such emphasis would adopt the recent software and hardware development technologies. This paper investigates the minimal hardware and software requirements to design and implement a fully functional academic and industrial automation system that can be readily attached to the available internet/intranet infrastructure. Three tiers mainly constitute the proposed system, the instrumentation and measurement tier, the software platform (for data collection, processing, displaying, and communication), and the client-server tier. The common controller-based techniques, such as PLC (Programmable Logic Controllers), SCADA (Supervisory Control and Data Acquisition), and DAQ (Data Acquisition) platforms can be very well employed in such applications without sophistication burdens. Eventually, the ultimate intentions of having engineers and technical operators to monitor, control, maintain, and calibrate factory equipment, or students involved in lab experimentation, from local or remote distances can be successfully achieved around the clock. Previous and current practical implementation examples will be verified to assess the feasibility range of existing techniques and their implications.