An induction heating and cooling mold that can keep the surface temperature of the entire mold cavity uniform and has a new heating and cooling insert with a gas vent mechanism is designed and produced. The effects of the temperature of the mold cavity surface, of the cavity air during the melt filling process, and of the organic gas generated from the melt on the appearance and mechanical properties of an injection molded product made of high impact polystyrene are studied. It is found that the heating and cooling mold with a gas vent can suppress molding defects, such as a weld lines and gas burns, and can greatly increase the displacement ratio of molded products obtained in the tensile test. This means that the effects of the gas vent and the surface temperature of the cavity have been quantitatively clarified using this type of mold.
Injection molding has faults, or sinks, caused by the shrinkage of materials. Sinks should be inhibited since they greatly affect the dimensions of moldings. In this study, a mold that allows visual observation is employed, and the sink initiation process is analyzed and predicted based on the results of that analysis. This mold has two sections, one flat and one curved. The difference between the deformations in the flat and curved sections is investigated. Methods of inhibiting sinks are considered from the results of the analysis and injection molding experiments. Packing pressure is found to have a great effect on sinks.
A press die has a reciprocating motion with the movement of the press machine. There is a very strong force between the upper and lower die. Utilizing the reciprocating motion, the author’s laboratory developed a high-pressure air compression unit, which can be fixed inside a die set. The generated powerful air can successfully blow slugs that occur in punching from the die. Moreover, it can be used as an independent power source to perform auxiliary motions, such as material sheet feeding or second working on the products, during the pressing process. This study describes the development of the air compression unit; the experiment carried out to test slug removal; and provides the related reference data to promote the further deployment and application of this technology.
Micro milling tools made of Single Crystalline Diamond (SCD) have been developed to machine micro dies and molds made of ceramics. The milling tools of a cylindrical SCD having many sharp cutting edges are fabricated 3-dimensionally by scanning a laser beam. Flat shape of binder-less tungsten carbide mold was cut with the developed milling tool to evaluate the tool wears and its life. Some micro aspheric molds of tungsten carbide were cut with the milling tool at a rotational speed of 50,000 min-1. The ceramic molds were cut in the ductile mode. By cutting with the milling tool, the form accuracy obtained was about 100 nm P–V and the surface roughness 8 nm Rz.
Dual-arm industrial robots have been gaining attention as novel tools in the field of new automation. We therefore focus on them to flexibly control both the linear motion and the rotational motion of a working plate. However, the difficulty of measuring the synchronous accuracy of two rotary axes without a high-accuracy gyro sensor has been a problem. We therefore propose a novel method of using a ball to measure the synchronous accuracy of two rotary axes of a working plate. The plate uses dual-arm cooperative control to keep the ball rolling in a circular path on it. In this report, we investigate the effects of the rolling friction coefficient of the ball on its sensitivity and resolution to estimate the synchronous accuracy of two rotary axes.
Molding is an effective and efficient approach to producing highly functional optical elements with complex shapes. However, edge sharpness is a serious problem with molded microstructures. An Ultrasonic-Assisted Molding (UAM) device was developed to improve shape transferability. First, basic experiments showed that UAM induced a maximum temperature increase of 3.2°C for a polycarbonate substrate with a starting temperature of 170°C, and the stick-slip phenomenon was not observed with ultrasonic vibration. Second, UAM and conventional molding simulation models were constructed to compare the transferability of a microgroove; ultrasonic superimposed press movement demonstrated the highest transferability. Finally, micrograting was fabricated using UAM and conventional molding, and the UAM micrograting had better transferability with a 30-s molding time. Therefore, UAM may be an effective process for reducing molding time.
This paper describes an approach achieving process design based on sustainability evaluation by Life Cycle Assessment (LCA). The case study focuses on quenching steel products, which was evaluated by comparing laser quenching to conventional furnace quenching based on the proposed approach. We found that the break-even point depends on production volume as one of product features. The proposed approach shows promise as a strategy for decision making in process design.
An analytical force model is applied in order to predict the cutting force in drilling of unidirectional Carbon Fiber Reinforced Plastics (CFRP). Because a three-dimensional chip flow is interpreted as a piling up of the orthogonal cuttings, the shear angle, the shear stress on the shear plane and the friction angle in the orthogonal cutting are obtained in the cutting tests. Because the chip thickness and the cutting force of CFRP depend on the cutting direction for the fiber orientation, the orthogonal cutting data are associated with the relative angle of the cutting direction with respect to the fiber orientation. The cutting forces in drilling are predicted using the orthogonal cutting data. The force model considering the fiber orientation is verified in comparison of the predicted cutting forces and the measured ones.
This paper presents the development of a low cost Remotely Operated Vehicle (ROV) which consists of open source hardware and has three thrusters. First, the hardware of the vehicle, including the actuators, sensors, and control structure, is described. Second, to study the relationship between the thrust forces and the performance of the ROV, a mathematical model of the vehicle in the form of a kinematic and kinetic model is established. Next, a hybrid control algorithm consisting of two components, namely model-based and PID algorithms, is proposed for surge speed, depth, and heading control. The effectiveness of the hybrid control algorithm is then verified by the ROV mathematical model-based simulations. Finally, free running tests for depth control are conducted to verify the robustness and reliability of the control structure and proposed algorithms.
This paper investigates a novel underwater breathing apparatus which has no air tank. Instead, it uses centrifugal separation to collect dissolved air. First, a prototype collector is proposed and fabricated. Then, the basic characteristics of various shape parameters are experimentally investigated using tap water to ascertain the optimal design. Next, to confirm the validity of the proposed mechanism, CFD analysis on collection ratio is done using the commercially available STAR-CD tool. After that, a suction device without an additional power source is developed to improve the air collection ratio. Finally, the redesigned collector is tested at different water temperatures, and the air collection results obtained are compared with the results of analysis.
It is important to establish a new way of creating value-added products, such as craftwork objects or applied arts, different from traditional way of achieving high quality and low price. Such a machining technology that enables (1) extremely complex or small shape generation, (2) machining of hard or soft materials, and (3) machining of difficult-to-grasp or fix workpiece may be called “Dexterous Machining.” Thus, the study deals with the first attempt to create an artistic product shape out of soft objects that have low stiffness and high elasticity. It is generally difficult to machine soft objects precisely because of the deformation caused by not only the cutting force but also the clamping force itself. In order to solve this problem, flexible clamper employing an aqueous solution of sodium acetate is devised to fix a workpiece and to suppress the deformation. The workpiece is placed in a case filled with an aqueous solution of sodium acetate on a machine tool table. The aqueous solution is crystallized by applying a stimulus, and the solid sodium acetate clamps the workpiece. As a result of experimental machining, it is found that the proposed flexible clamper has the potential of realizing “Dexterous Machining” of soft objects.