The demand for inspection of high-speed systems for machined Carbon Fiber Reinforced Plastics parts for automobileindustry and aviation industry is constantly rising. One of the factors that degrade the performance of an inspection system is micro-vibration from the ground or structure where is placed. Various isolation systems that suppress the vibration have been studied classified as either passive or active system. The passive system is composed of a spring and a damper while the active system suppresses the vibration through an electronic control system using sensors and actuators. In this study, a voice coil motor (force constant 55N/A) acting as the actuator is optimally designed using permeance method and sequential quadratic programming algorithm to suppress the vibration and reaction force by a specimen moving stage. The two optimized voice coil motors are attached to a pneumatic mount that has an advantage in design based on the force and size constraints required by the user for an active vibration isolator with velocity sensors (GS-11d). The active vibration isolation system with the four active vibration isolators -23 dB and -20 dB at resonance frequencies in horizontal and vertical transmissibility performs better than a passive vibration isolation system.
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An Active Geophone Sensor with Optimized State Variable Filter for Measuring Low-Band Frequencies Jinsoo Choi, Hongki Yoo, Eunjong Choi, Kihyun Kim, Hyo-Young Kim International Journal of Precision Engineering and Manufacturing.2024; 25(5): 981. CrossRef
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Transportation industries, such as aerospace and automotive demand high efficiency using lightweight parts. Carbon Fiber Reinforced Plastics (CFRP) present promising materials for transportation industry parts due to their lightweight and highstrength properties. Forming and machining processes are required to manufacture parts from carbon fiber composite materials. The near-net shaping process forms the parts, and the final accurate shape and hole are accomplished using the machining process. However, high-strength carbon fiber chips and dust from the machining process cause cutting tool wear and low productivity. The hybrid CRD (Cutting, Routing and Drilling)/water-jet machine improves tool life and productivity because its water-jet process, employed before the mechanical machining process cuts roughly without chips and dust. In this study, the hybrid CRD/water-jet machine we developed was introduced and its machining performance was evaluated using a drilling process. The delamination factor and surface roughness of drilled holes were compared with the results from a conventional machine tool.
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Lightweight parts are necessary to improve fuel efficiency and reduce environmental impacts in transportation industry. As a result, there has been a shift away from using conventional metals toward using lighter materials with superior mechanical strength. These new materials typically include titanium alloys, nickel alloys, carbon fiber reinforced plastics (CFRPs), and CFRP-metal stacks, which are classified as advanced materials. However, due to the unique properties of these materials (e.g., high strength, low thermal conductivity, carbon fiber-induced hardness, etc.), the cutting process can be difficult. As a result, various manufacturing issues can occur during the cutting process, such as high tool wear, surface quality deterioration, delamination of the CFRP layer, fiber pull-out, and thermal deformation. In this paper, difficult-to-cut advanced materials were reviewed with regard to the influence of the physical properties of the materials and various defect issues that can occur during the mechanical cutting process. In addition, various approaches to improve the cutting process are introduced, including protecting tools with coatings, altering tool features, using high pressure or cryogenic cooling, extending tool life via ultrasonic vibration machining, and improving product quality and machinability.
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Tool wear is an essential parameter in determining tool life, machining quality and productivity. Current or power signals from motor drivers in machine have been used to estimate tool wear. However, accuracy of tool wear estimation was not enough to measure the amount of tool wear. In this study, flank wear of a drill tool was measured using vision sensor module which has zoom lens, CCD camera and image processing technique. The vision module was set up in the machine tool. Therefore, the image was acquired without ejecting the tool from the machine. Image processing techniques were used to define the cutting edge shape, tool diameter, and the wear edge on cutting rips with the proposed measuring algorithm. The automatically calculated wear value was compared with a manually measured value. As a result, the difference between the manual and the automatic methods was below 4.7%. The proposed method has an advantage to decrease the measuring time and improve measuring repeatability because the tool is measured holding chuck in a spindle.
Carbon Fiber Reinforced Plastics (CFRP) is an encouraging material for aerospace and automotive industries due to its light weight and high strength. Aerospace parts require precise dimensional tolerance and high machined surface quality for safety and reliability. Routing process is needed to produce satisfactory dimensional accuracy of CFRP parts. Machining defects of routing process are related to the cutting mode with respect to cutting angle and bonding strength between carbon fibers and polymer matrix. When the polymer matrix is transformed from polymer to amorphous state, bonding strength is declined. Therefore, cutting temperature is a critical parameter for CFRP machining process because glass transient temperature is relatively low. In this paper, cutting temperature was measured using thermal imaging camera. Machined surface roughness and maximum fiber pull-out depth were analyzed with respect to feed, spindle speed, and laminate structure.
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A Study on the Improvement of Bonding Strength of Heterojunctions by Applying Laser Surface Treatment to Carbon Fiber Reinforced Plastics Huan Wang, Seong Cheol Woo, Chung-Ki Sim, Seong-Kyun Cheong, Joohan Kim Journal of the Korean Society for Precision Engineering.2022; 39(9): 683. CrossRef
Comparison Study on Side Milling of CFRP with AlCrN-based, Diamond-Like-Carbon(DLC), and Diamond-Coated End Mill Min-Woo Sa Journal of the Korean Society of Manufacturing Process Engineers.2020; 19(4): 9. CrossRef
Fabrication of Micro Tool Electrode by Micro EDM using Wear Ratio In Yong Moona, Do Kwan Chung, Bo Hyun Kim Journal of the Korean Society of Manufacturing Technology Engineers.2018; 27(1): 1. CrossRef
Titanium alloy has been widely used in the aerospace industry because of its high strength and good corrosion resistance. During cutting, the low thermal conductivity and high chemical reactivity of titanium generate a high cutting temperature and accelerates tool wear. To improve cutting tool life, cryogenic machining by using a liquid nitrogen (LN2) jet is suggested. In cryogenic jet cooling, evaporation of LN2 in the tank and transfer tube could cause pressure fluctuation and change the cooling rate. In this work, cooling uniformity is investigated in terms of liquid nitrogen jet pressure in cryogenic jet cooling during titanium alloy turning. Fluctuation of jet spraying pressure causes tool temperature to fluctuate. It is possible to suppress the fluctuation of the jet pressure and improve cooling by using a phase separator. Measuring tool temperature shows that consistent LN2 jet pressure improves cryogenic cooling uniformity.
Recently, concerns about the environment are becoming more important because of global warming and the exhaustion of earth’s resources. In the aviation and automobile industries, the application of light materials is increasingly important for eco-friendly and effective. Carbon Fiber Reinforced Plastics is a composite material which great formability and the high strength of carbon fiber. CFRP, which is both light and strong, is hard to manufacture. In addition, CFRP machining has a high chance of defects. This research discusses the development of a manufacturing system package for CFRP machining. It involving CFRP Drilling/Water-jet Manufacturing Machines, Inspection/Post-processing Systems, CNC platform for an EtherCAT servo Communication, Flexible Manufacturing Systems and CFRP machining Processes.
CFRP (Carbon Fiber Reinforced Plastic) and CFRP-metal stacks have recently been widely used in the aerospace and automobile industries. When CFRP is machined by a brittle fracture mechanism, defect generation behaviors are different from those associated with metal cutting. The machining quality is strongly dependent on the properties of CFRP materials. Therefore, process control for CFRP machining is necessary to minimize the defects of differently manufactured CFRPs. In this study, defects in drilling of CFRP substrates with a variety of fiber directions and resin types are compared with respect to thrust force. An experimental study on material interface detection is carried out to investigate its benefits in process control.
Recent trends in the flexible manufacturing systems are morphing cell control for the shop-wide production operation system and providing the integrated operation and execution system together with vendor-specific FMC/FMS platform. In these requirements, the shop-floor level operation system plays a role of coordinating the control activity of each cell, and has to provide flexibility for the complexity of mixed operations of various cells. This paper suggests a system architecture for the mixed environments of multi-cells and job shop, its corresponding enabling technologies based on comparative studies with other related studies and commercialized systems. This approach includes a process definition model considering the integration with upper BOM-BOP and external service modules, and reconfigurable device-level interface which provides dynamic interconnections with machine tools and cell controllers. The function modules and their implementation results are also described to provide the feasibility of the proposed approaches as the flexible shop-floor operation system for the multi-cell environments.
The application of focused ion beam (FIB) technology in micro/nano machining has become increasingly popular. Its use in micro/nano machining has advantages over contemporary photolithography or other micro/nano machining technologies such as small feature resolution, the ability to process without masks and being accommodating for a variety of materials and geometries. In this research, fabrication of micro plasma electrode was carried out using FIB. The one of problems of FIB-sputtering is the redeposition of material including Ga+ ion source during sputtering process. Therefore the effect of the redeposition was verified by EDX. And the micro plasma electrode of copper was fabricated by FIB.
With the acceleration of the miniaturization of products, especially in recent years, machining technologies for these products is in need of improvement. Conventional technologies have limitations in realizing the miniaturization due to the downsizing effects of the tools, which lack sufficient cutting stiffness during machining. The application of ultrasonic vibration is one of the most useful solutions in dealing with the problem. This study focused on the difference of ultrasonic drilling from conventional one in geometrical machining mechanism and the corresponding machining results. In detailed, some mathematical equations for drill cutting edge paths during drilling were extracted and new method to find uncut chip thickness from above equations was suggested. The experiments were carried out through the comparison between the results (disposed chips and internal surface states of holes) of conventional drilling and those of ultrasonic drilling. It was determined that the geometrical paths of cutting edges and analyzed uncut chip thickness agree with the appearance of disposed chips. Furthermore, the change in tool path by ultrasonic vibration resulted in the improvement of surface statement.
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