For aiming at successful operation of directed energy deposition (DED) type additive manufacturing (AM) system, three different kinds of process elements, machine motion, powder supply and laser application, needs to be synchronously controlled for accurate shape creation of the work piece. In order to synchronize these elements, in this study, measurement method of these response delay time has been proposed. According to the method, using the specific DED type AM system, the response delay time has been identified as that of laser application is 0.72±0.2 second and the powder supply control has about 15 seconds response time delay while the evaluated response delay time of nozzle motion was negligible compared to that of other two elements. Using identified response characteristics, dead time compensation control has been adopted to absorb the response delay time of laser and powder application processes. Laser application commands were indicated prior to reaching targeted positions and a pseudo motion command was inserted to absorb the response delay time of powder supply before starting the subsequent actual deposition with the correct powder supplied amount. Performing experimental studies, target deposition shapes have been achieved without unintended deposition and effectiveness of the proposed optimization method has been confirmed.

Machining process is a typical example of the non-equilibrium phenomenon. The aim of this study is to investigate the influence of built-up layer (BUL) on the tool wear mechanisms of uncoated and coated carbide tools. To investigate how the BUL formation affects the tool wear mechanisms, dry cuttings of Inconel 718 with uncoated, PVD and CVD coated carbide tools were conducted. The worn cutting tools were analyzed using laser scanning microscopy, scanning electron microscopy and electron probe micro analyzer. It is found that BUL can for m on the tool rake face under different cutting conditions. At the beginning of cutting, the coating of coated carbide tool falls off quickly, then BUL forms on the tool rake face which can protect the tool from further wear. Concerning the flank wear, it is confirmed that the size of BUL has a great influence on the flank wear. In addition, the adhered material on the worn flank face, which is called as flank built-up (FBU), is also an important factor for the flank wear development. And the effects of the BUL/FBU formation should be considered into the cutting tool's flank wear model. To further understanding the experimental results, the thermodynamic discussion is conducted. The result shows that BUL/FBU can be considered as a form of “dissipative structure substance” which can reduce tool wear during cutting and tool wear formation is an irreversible energy dissipation process relating to entropy production.

This study provides an investigation of the cutting mechanisms and drilling characteristics of cemented tungsten carbide using a diamond-coated carbide drill under an ultrasmall feed rate. The thrust force, cutting edge shape, chip morphology, and drilled hole quality were evaluated. A diamond-coated carbide drill with two flutes, a diameter of 1.0 mm, and a coating thickness of 20 µm was applied. The thrust force was drastically decreased until the ∼10th drilling for various cutting conditions. Diamond coating flaking was only observed on the rake face immediately after the onset of cutting, and a sharp cutting edge was generated on the ridgeline of the diamond coating section on the flank face. The flaking region of the diamond coating on the rake face was extended from around the corner edge with increasing drilling number. The cutting performance was maintained until the ∼300th drilling, even though minimal flaking and chipping of the cutting edge also occurred on the flank face. The thrust force also sharply decreased when the diamond coating flaking around the chisel edge occurred. A sufficient inner surface integrity of the drilled hole was obtained, although the drilled hole diameter changed within the hole by transferring the contour of drill, which is flaking the diamond coating around corner edge and margin, to the drilled hole shape.

In this study a new method of gear cutting is proposed. The principle of involute gear generation is as follows: the rack cutter moves in a reciprocatory manner and feeds to the tangential direction of the gear. In the proposed method, a taper endmill is used as the cutter, and the rotating cutter feeds in both the axial and tangential directions of the work gear. By using only a taper endmill, the machining of gears with various specifications including the module, number of teeth, pressure angle, and addendum modification coefficient can be realized. The commonly used gear-cutting method is that of hobbing or gear shaping. In these methods, dedicated tools such as a hob or pinion cutter are used; with them, only gears with a predetermined module and pressure angle are machined. In other words, when gears with different modules or pressure angles are machined, changing the tool is necessary. A formed tool is used as a gear-cutting method that employs an end mill. However, this tool can only machine a predetermined module, pressure angle, and number of teeth. The most important feature of the proposed gear-cutting method is that no restrictions are placed on the gear specifications. In this study, the geometric mechanism of an involute gear cutting using a taper end mill is described. An example of actual machining with a 5-axis machining center or a general-purpose milling machine is also shown, and the utility of the new method is discussed.

During wire electrical discharge machining, the wire electrode is deflected by various forces like discharge reaction force. Since the generated deflection and vibration affect processing accuracy, it is necessary to accurately control the wire behavior during machining in real time. Thus in this research, the authors proposed a real-time simulation method to obtain data on the three dimensional wire behavior. The discharge reaction force was obtained from the inverse problem method in which the discharge reaction force was determined so that the two dimensional displacement of the wire electrode measured by an optical sensor coincides with the calculated displacement. A prototype of the simulation system was made, and the change of the wire electrode behavior was measured during rough machining with increasing cutting depth. In addition, the influence of the fluid flow on the wire behavior, which is not negligibly small compared to the discharge reaction force, was investigated using the optical sensor.

An internal surface of a deep hole is finished by internal grinding. Although the grinding wheel is fed to the axial direction of the workpiece with oscillation in the conventional internal grinding, the end of the wheel wears out. To prevent the intensive wheel wear, we proposed a new internal grinding method. In this method, the grinding wheel was fed to the radial direction and the plunge grinding was carried out by a slender grinding wheel. In this method, the grinding wheel should be retracted at the suitable moment to reduce the internal form error of the ground workpiece. The main cause of the form error is elastic deformation of the grinding wheel, and the wheel runout is also an error factor. The form error of the workpiece was improved with considering two kinds of error factor in the plunge internal grinding with a slender grinding wheel. Furthermore, the profile of the grinding wheel was modified to shorten the grinding cycle time.

To satisfy the miniaturization requirements of semiconductor manufacturing and metrology, orthogonal Z-axis stage controllability of equipment using highly accurate position detectors are necessary in addition to fundamental XY-axes stage movement control. The Z-axis position detector must have high accuracy, high resolution, and high stability against environmental changes in temperature, humidity, and air pressure. In this paper, a two-dimensional encoder based on a grating interferometer detection method is presented. A prototype XZ-axes encoder was built and evaluated for long-term stability against variations in environmental conditions as well as short-range linear accuracy. The evaluation results show that it is feasible to integrate the encoder with a highly accurate two-dimensional (XZ or YZ) stage control with sub-nanometer resolution. The performance of the encoder as a Z-axis position detector satisfies the demands of industry. By applying the methods developed to the third axis, it can be possible to upgrade the position detection system to three dimensions.

Service life of ball screws for high-load drive is typically determined by rolling fatigue failure of screw shaft and/or nut raceways. For well lubricated, properly installed ball screws, failure usually results from damage originating on raceway surfaces due to sliding friction in ball-raceway contact because of the structure of ball screws (e.g., helical raceway and ball recirculation system), eventually forming “peeling” or “flaking” damage structures on raceway surfaces. The authors investigated failures of conventional ball screws using life test data. As a result, the authors developed guidelines for improving durability considering the mode of failure of the ball screw. To extend the life of the ball screw, it is effective to increase the retained austenite amount γ_R of the material. It can be estimated how much to increase γ_R for each part of the ball screw by considering ball load distribution and number of stress cycles. Based on the above, new ball screws were fabricated and durability testing was conducted under high load conditions. The rated life L₁₀, indicating the estimated time at which 10% of a population of ball screws made with high-γ_R materials will have failed, was more than three times that of the conventional products.

Currently, robots that support people are needed, e.g., nursing robots. They need quick motions and high power, depending on the situation. One solution for this is a hydraulic system; however, conventional hydraulic systems are difficult to control precisely because they use pumps. Therefore, we propose a smart hydraulic system with a compact hydraulic source driven by electric motors. It includes two functions: a dual-state transmission mechanism and a simultaneous position control of multi-cylinder. This system is useful to drive a robot's arms based on reciprocating motions. The dual-state transmission is realized by using valves that block or allow the flow of oil between two sides of the power-source cylinder. The output cylinders for a multi-joint robot arm should be controlled simultaneously from one electro-hydraulic source. To prevent counter-flow to other cylinders, the output cylinders are moved by switching solenoid valves one after another in a short cycle such that only one is moved at a certain moment. It is also important to decrease the overshoot of the cylinders when it is moving toward the load direction. We control sending the oil into the cylinder and also sucking it out of the cylinder. We experimentally verified the effectiveness of these abilities.

Currently, laser-scanned point clouds in urban areas can be obtained efficiently by Mobile Mapping Systems (MMS). The purpose of this study is to develop an automatic generation method of building models from point clouds in urban area acquired by MMS for city planning and disaster simulations. In this paper, we propose a point cloud segmentation method and a Level-Of-Detail (LOD) modeling method of buildings. First, an accurate building segmentation method is proposed based on overlap evaluation of occupied regions in each floor of the building. The method realizes accurate building segment extraction from complex urban areas where buildings are often very close to each other, and some buildings are connected by attached objects such as fences and sign boards near or at ground level. Then, an automatic building modeling method considering LOD and regular pattern of windows and verandas is proposed based on point projection and regular line fitting. The LOD of the resulting models can be controlled depending on the applications, and the models have regular pattern windows and verandas, which can support compact model representation. The building segmentation and modeling methods are evaluated using MMS point clouds in dense and complex urban areas.

This paper describes the evaluation and optimization of the inner shape of three-dimensional small glass holes using a replica method and mathematical programming with a stepwise procedure. The glass holes were made by rotary ultrasonic machining with a diamond grinding tool which had 1 mm diameter. The hole characteristics to evaluate were radius and roughness. The replica method had enough accuracy to evaluate the desired characteristics. We first executed 12 runs of our experiment following the “Plackett-Burman Design” (PBD) to select the appropriate grinding tool. Next we did a “Central Composite Design” (CCD) experiment to construct models of each characteristic and evaluate them for order of effect. Finally we optimized those multiple characteristics using mathematical programming. We focused on efficiency, and prioritized the characteristics for optimization so that we optimized each characteristic step by step. We reviewed and confirmed the result of the optimization was effective. In conclusion, our approach to the evaluation and optimization of small glass holes machining is effective and practical.

Training systems for manual machine tools using virtual reality have been developed for high safety and economy. Using these systems, a trainee can safely work on virtual machines to manipulate input interfaces modeled after devices in real-world machines. However, a trainee cannot completely learn how to use the target machine because the interface lacks all the necessary devices. Because safety is ensured even if the trainee performs dangerous actions, these virtual systems cannot teach safety measure. Therefore, after training with these systems, a trainee needs instructors when operating actual machines. This study describes a training system that does not require instructors. By training with the proposed system, a trainee can safely work on virtual machines as the input interface to manipulate the actual lathe. This system constantly monitors the position of all operating devices, handles and levers on the actual lathe, and the user’s body parts (the head, both hands and upper body of the trainee) by motion capture. The behavior of the virtual lathe and the cutting of the virtual workpiece are simulated from the manipulated variables. This system can detect whether the trainee is in danger from the movement of his body parts.