Key Engineering Materials Vol. 625

Abstract: In this research, an automated robotic bin-picking system employing active vision for picking up randomly distributed plumbing parts is presented. This system employs an actively-controlled single eye-in-hand system to observe structured light projected onto a set of plumbing parts in a bin. By using image processing and iterative closest point (ICP) algorithms, a single plumbing part that could possibly be taken from the bin is detected. Specifically, by projecting stationary structured light patterns onto the set of plumbing objects, the features on the surfaces of plumbing parts can be reconstructed by actively moving the eye-in-hand camera while performing visual tracking of those features. An effective 3D segmentation technique is employed to extract the point cloud of a single plumbing part that can possibly be grasped successfully. Once the object point cloud is obtained, one needs to determine the coordinate transformation from the end-effector to the selected plumbing part for grasping motion. With the point cloud matching result based on utilizing the ICP algorithm, the position and orientation of the selected plumbing part can be correctly estimated if the deviation of the object point cloud from the model point cloud is small. The control command can thus be given to the robotic manipulator to accomplish the automated bin-picking task. To effectively expand the allowed deviation of the object point cloud, an approximate pose estimation algorithm is employed before performing the ICP algorithm. The proposed approach can virtually estimate any pose of the plumbing part and has been successfully experimented with an industrial manipulator equipped with eye-in-hand single-camera vision and a LCD projector fixed in the work space demonstrating the feasibility and effectiveness. The proposed automated bin-picking system appears to be cost-effective and have great potentials in industrial factory automation applications.

Abstract: Previous studies on the bending process of extruded aluminum alloys have focused on a high-precision bending process that controls various undesirable phenomena. In contrast, this paper proposes a new bending method in which undesirable deformations are intentionally occurred and can be deformed into an arbitrary cross-sectional shape. By bending the extruded section, we sought to establish a novel bending process, in which a curvature and cross-sectional shape are produced in a single process. Undesirable deformations that occur by bending channel materials with a removed tensile flange include both the outward and inward deformations of the webs. Based on such deformations, this report proposes several types of cross-sectional shapes that can be formed through simulations and press bending experiments.

Abstract: Products such as parts of die sets and cutting tool inserts are normally produced with complex shapes in materials of high hardness and wear resistance such as ceramics. Electro discharge machining (EDM) can be used to manufacture complex shapes in high hardness materials, but the material should be conductive. Being conductive, Aluminum oxide (Al₂O₃) based ceramics represent a good alternative for manufacturing hard complex shape parts. However, the integrity of the produced surfaces and the material removal rate need to be investigated. A full factorial experimental design was used to investigate the effect of some selected process variables, namely; pulse-on time, pulse-off time, and pulse current on specific EDM performance measures. The considered performance measures are; crater diameter (D), material removal rate (MRR), and average roughness value (Ra). An analysis of variance (ANOVA) test was carried out to evaluate the experimental results. Empirical models have been developed using DESIGN EXPERT V.8 to predict the average crater diameter (D), material removal rate (MMR), and average roughness value (Ra). Machining conditions that should result in optimum process performance measures have also been considered.

Abstract: Die-casting process is significantly used in the industry for its high productivity and less post-machining requirement. For high pressure die-casting, it needs well-design of gating and runner system; therefore, die cavity design and technology parameter calculations are essential. In the current paper of die-casting for automobile starter motor casing, the following issues are focused: filling simulation, defect analysis, and finally the use of the Taguchi multi-quality analysis method to find the optimal parameters and factors to increase the aluminum ADC10 die-casting quality and efficiency. When the casting speed is increased, the volume shortage detects due to solidification procedure can be reduced. However, if the casting speed exceeds a permissible level, the defects of gas volume and porosity will occur. After Taguchi method analysis, the results of the optimum parameters are: for the gate area of 40mm², group 2 of the gate location, the speed of the liquid metal at the gate 50 m/s, the temperature of molten aluminum 670° C.

Abstract: Electrical discharge phenomena in EDM occur in a very short time period and in a very narrow space, thus making both observation and theoretical analysis extremely difficult. For this reason, the material removal mechanism in EDM has yet to be understood clearly. EDM is a thermal process. Thermal energy is generated by a pulse discharge between the workpiece and the tool electrode. It results in melting and evaporating followed by removal of both the workpiece and tool electrode, forming a discharge crater on both surfaces. In this paper, the hydrostatic pressure distribution in melting area was simulated by Molecular Dynamics (MD) methods. The analysis shows that after discharge is ignited, extremely high pressure is generated inside the melting area. The pressure distribution along the central axis of the melting area at different times indicates that during the discharge duration, the hydrostatic pressure quickly increases to a peak value along the depth direction of melting area and then reduced to 0 GPa in the unaffected area. It was also found that with the passage of time, the depth of the point where the pressure peaks increases with the formation of the discharge crater, accompanied by the decrease in the peak pressure. In addition, the ejected material atoms at different times during the removal process were also analyzed. It was found that the material ablation occurs mostly during the discharge duration.

Abstract: Recently, the concern for the environment has been increasing rapidly. In machining processes, the treatment of water-soluble coolants waste has caused environmental problems. Water-soluble coolants contain surfactants, preservatives, and corrosion inhibitors for maintaining the stability and performance of the coolants. To reduce the management cost and environmental effect of water-soluble coolants, the authors have been studying a recycling system for water-soluble coolants. In the recycling system, oil-free recycle water is isolated from the coolant waste and reused as a diluent of the new coolant. The authors have been developing different types of water recovery methods for the recycling system, and the recovered water from the coolant waste has potential as a diluent for a new coolant. In this report, we focused on the amine (alkanolamine) -free water-soluble coolant. Some amine-free water-soluble coolants have been developed and are commercially available. A reduction in the environmental effect in the waste treatment of coolants is expected with amine-free coolants. We have demonstrated that the amine-free water-soluble coolant has equal or better cooling and lubricating performance compared with the conventional amine-containing coolant. In addition, the amine-free coolant shows good recyclability for the recycling system. The processing time of the recycling treatment of the amine-free coolant has been decreased by half with our recycling process compared with the conventional amine-containing coolant. In this report, we examined the stability, cooling performance and lubricating performance of the recycle amine-free water-soluble coolant in long term operation. The recycle amine-free water-soluble coolant is operated in a 3-axis machining center for several months. We observed concentration, pH, corrosion inhibition performance, cooling performance, and lubricating performance of the coolant. The results from these experiments show the amine-free water-soluble coolant has the advantage to use in the recycling system for water-soluble coolant.

Abstract: Lower extremity exoskeleton is a mechanical device mainly for augmenting the performance of a healthy person or assisting the people with lower limb pathology. In this study technology evolution of lower extremity exoskeletons was analyzed from the patent perspective. Patent citation analysis based on a specific patent issued by USPTO in 2011 was carried out to trace the evolution of technology concepts in the past four decades. The technologies of control system, sensor, actuator and mechanism applied were compared from the viewpoint of hip, knee and ankle movement, and the most or relatively more cited patents were selected as the representatives of technology. Several trends of design concept with respect to the hip, knee and ankle movement were presented in the paper. For example, for the design of subsystem hip joint, the considerations were taken gradually from prevention of subluxation or dislocation of hip joint alone at the early days to reducing metabolic energy associated with walking/running as well as reducing the incidence of falls caused by the insufficient leg thrust recently. For the design of subsystem knee joint, articulated splints with hinge pivot, articulate notch or spring at the beginning were replaced by the piston and cylinder assemblies with adjustable valves to resist the flexion and extension of the joint, and later by the damping member with control unit for detecting the force, knee angle and acceleration.

Abstract: This paper proposes a novel process strategy for micro-cutting edge fabrication. Micro-cutting edges need a hardening process for the ridgeline parts that requires abrasive resistance, as well as edge sharpness and shape accuracy, based on their applications. Micro-cutting edge shapes also vary greatly in ridgeline profile and section. The proposed method is shape fabrication after laser hardening, which easily addresses these issues. In the present paper, effects of the proposed method are discussed and the results of a demonstration test are introduced.

Abstract: Plasma chemical vaporization machining (PCVM) is a high-speed plasma etching method using atmospheric-pressure plasma. Although it does not leave an affected layer on the processed surface because of the small ion energy owing to the small mean free path of gas molecules, it is not suitable for planarization because of its isotropic etching. Thus, a combination of PCVM and a mechanical machining process is proposed. The convex parts of a substrate surface are considered to be affected by mechanical machining and are removed preferentially by PCVM. In this report, it is investigated whether etching rate of the affected layer becomes larger or not. As a result, it was found that the etching rate increased in the first 100 nm depth of the mechanically polished substrate, which corresponds to the thickness of the heavily damaged layer observed by cross-sectional transmission electron microscopy.

Abstract: Electrical discharge machining (EDM) is a process of removing material by electric discharge in an insulating working fluid. The material is melted by discharge, the material is thought to blown off by the vaporizing explosion of the working fluid. The removal of the material is affected by the expansion and contraction of a bubble. When the power of the vaporizing explosion is large, the amount of material removed increases, and surface roughness decreases. However, when the power of the vaporizing explosion is small, the amount of material removed decreases and surface roughness increases. The power of the vaporizing explosion is determined by the input energy, and the amount of material removed is determined by the degree of the power of the vaporizing explosion. This study considers the changes in the characteristics of EDM by using a working fluid mixed with micro-bubbles. A micro-bubble is defined as a bubble having a diameter of less than or equal to 50 μm. They have special characteristics of causing an increase in the interior gas pressure, resulting in an increase in ion concentration around the gas–water interface. The vaporizing explosion seems to be weakened by the use of a working fluid mixed with micro-bubbles, and surface roughness seems to be improved. Therefore, we performed EDM using pure water and a micro-bubble mixed fluid to clarify the characteristics of EDM.