The kinematic constraints used in a computerized numerical control (CNC) interpolator are one of the main factors determining a machine tool’s machining accuracy. The CNC generates velocity profiles by applying kinematic constraints such as jerk and acceleration. Therefore, changing the kinematic constraints values can adjust the cycle time and cornering error. This study proposes a method to adjust the kinematic constraint values. First, the relationship between CNC kinematic constraints and cornering errors were analyzed. The relationship between the kinematic constraints and the cornering error was expressed as an analytical solution. Kinematic constraint values that satisfy specific cornering error values were selected using the analytical solution of cornering error. Finally, a method was devised to apply the appropriate kinematic constraint values to each machining section within a part program. The analytical solutions for cornering errors and using different machining segments to control cornering errors were verified using tool path generation simulation.
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New Design of Smooth PSO-IPF Navigator With Kinematic Constraints Mahsa Mohaghegh, Hedieh Jafarpourdavatgar, Samaneh-Alsadat Saeedinia IEEE Access.2024; 12: 175108. CrossRef
E-Beam micro-hole drilling features high productivity of 2,000 holes per second and a high aspect ratio of 10 (depth/diameter). It can be used for the fabrication of nozzles and filters that require several holes. The hole-formation mechanism comprises 1) melting the sample by the energy exchange of e-beam and 2) removing the molten sample by the explosion of the backing material. Accordingly, hole-formation mechanism studies have focused on the effectiveness of backing material and the workpiece’s melting characteristic. This study investigated the melting depth characteristics depending on the beam current and exposure time that determines the E-Beam dose. The experiments were conducted without using the backing materials with an aim to investigate the melting characteristic of the workpiece itself. The results showed that the increase in the exposure current led to an improvement in the melting depth. The results were verified based on the comparison with the results of the process involving the backing material.
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Micro CT Analysis of Microholes Drilled by Focused Electron Beam Drilling Based on Image Noise Reduction Using Masking Layers Hyunmin Park, Joon-Goo Kang, Jin-Seok Kim, Eun Goo Kang, Hyung Wook Park, Jaewoo Seo Journal of the Korean Society of Manufacturing Technology Engineers.2022; 31(6): 388. CrossRef
As geometry of machined parts becomes complex the demands for more precise and faster machining using advanced computerized numerical control (CNC) are increased. Especially, recently improved computing power of CNC enables the implementation of the complicated control algorithms. Consequently a variety of intelligent control algorithms have been studied and implemented in CNC. This paper reviews the recent progress of control technologies for precision machining using CNC in the area of interpolation, contour control and compensation. In terms of interpolation several corner blending methods and parametric curves are introduced and the characteristics of each method are discussed. Regarding contour control algorithms recently developed multi-axis contour control methods are reviewed. Latest research efforts in compensation algorithms for geometric, thermal and friction induced errors in CNC machining are introduced.
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Improved Input Shaping Method for Circular Interpolation of a 2-Axis Positioning System Jin Uk Sim, Pil Kyu Choi, Sun-Woong Kwon, Seong-Wook Hong Journal of the Korean Society for Precision Engineering.2022; 39(4): 283. CrossRef
Computer numerical control (CNC) part programs generated by computer-aided manufacturing software are frequently composed of numerous G01 blocks. CNC interpolator applies acceleration and deceleration to generate velocity profile of each block. Therefore, the machining time is increased when the number of G01 blocks is increased. To reduce the machining time, corner blending has been used to smooth the corner shape of adjacent blocks. Because the tool path generated by corner bending dose not reach the commanded endpoint, error of the interpolated tool path exists. The objective of this study was to present a method to determine block overlap time to limit tool path error generated by corner blending. An algorithm to calculate tool path error with respect to block overlap time was also proposed. Performance of the proposed algorithm to limit tool path error was demonstrated in this study.
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Impact of broad ion beam center alignment and mask position on Si wafer cross-section milling rate Jong-Han Won, Ki-Hwan Kim, Dong-Young Jang, Geon-Yeong Park Micro & Nano Manufacturing.2025;[Epub] CrossRef
Block Overlap Based CNC Interpolator with Variable Time Constant Chan-Young Lee, Chang-Ju Kim, Seung Guk Baek, Segon Heo Journal of the Korean Society for Precision Engineering.2025; 42(2): 169. CrossRef
Process Monitoring and Part Program Optimization Using Virtual Machine Tools Chang-Ju Kim, Segon Heo, Chan-Young Lee, Jung Seok Oh Journal of the Korean Society for Precision Engineering.2022; 39(12): 879. CrossRef
Cycle Time Estimation of Block Overlap Based CNC Chan-Young Lee, Seung-Kook Ro, Chang Kyu Song, Jeong Seok Oh Journal of the Korean Society for Precision Engineering.2022; 39(7): 537. CrossRef
Improved Input Shaping Method for Circular Interpolation of a 2-Axis Positioning System Jin Uk Sim, Pil Kyu Choi, Sun-Woong Kwon, Seong-Wook Hong Journal of the Korean Society for Precision Engineering.2022; 39(4): 283. CrossRef
CNC Algorithms for Precision Machining: State of the Art Review Chan-Young Lee, Seong Hyeon Kim, Tae In Ha, Jaehong Min, Soon-Hong Hwang, Byung-Kwon Min Journal of the Korean Society for Precision Engineering.2018; 35(3): 279. 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.
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.
Design and application of hardware-in-the-loop simulation (HILS) for design of CNC-controlled machine tool feed drives is discussed. The CNC machine tool is a complex mechatronics system where the complexity results from the software-based controller composed of a variety of functionalities and advanced control algorithms. Therefore, using a real CNC controller in the control simulation has merits considering the efforts and accuracy of the simulation modeling. In this paper challenges in HILS for a CNC controlled feed drive, such as minimization of time delay and transmission error that are caused by discretization of the feed drive model, is elaborated. Using an experimental HILS setup of a machine tool feed drive applications in controller gain selection and CNC diagnostics are presented.
Control systems in machinery equipment provide correction signals to motion units in order to reduce or cancel out the mismatches between sensor feedback signals and command or desired values. In this paper, we introduce a simulator for control characteristics of machinery equipment. The purpose of the simulator development is to provide mechanical system designers with the ability to estimate how much dynamic performance can be achieved from their design parameters and selected devices at the designing phase. The simulator has a database for commercial parts, so that the designers can choose appropriate components for servo controllers, motors, motor drives, and guide ways, etc. and then tune governing parameters such as controller gains and friction coefficients. The simulator simulates the closed-loop control system which is built and parameter-tuned by the designer and shows dynamic responses of the control system. The simulator treats the moving table as a 6 degrees-of-freedom rigid body and considers the motion guide blocks stiffness, damping and their locations as well as sensor locations. The simulator has been under development for one and a half years and has a few years to go before the public release. The primary achievements and features will be presented in this paper.
The cold hollow cathode gas ion source is under development for multi aperture focused ion beam (FIB) system. In this paper, we describe the cold hollow cathode ion source design and the general ion source performance using Ar gas. The glow discharge characteristics and the ion beam current density at various operation conditions are investigated. This ion source can generate maximum ion beam current density of approximately 120 ㎃/㎠ at ion beam potential of 10 kV. In order to effectively transport the energetic ions generated from the ion source to the multi-aperture focused ion beam(FIB) system, the einzel lens system for ion beam focusing is designed and evaluated. The ions ejected from the ion source can be forced to move near parallel to the beam axis by adjusting the potentials of the einzel lenses.
Recently, focused ion beam (FIB) applications have been investigated for the modification of VLSI circuit, the MEMS processing, and the localized ion doping. A multi aperture FIB system has been introduced as the demands of FIB applications for high speed and large area processing increase. A liquid metal ion source has problems, a large angular divergence and a metal contamination into a substrate. In this study, a gas ion source was introduced to replace a liquid metal ion source. The gas ion source generated inductively coupled plasma (ICP) in a quartz tube (diameter: 45 ㎜). Ar gas fed into the quartz was ionized by a 2 turned radio frequency antenna. The Ar ions were extracted by 2 extraction grids. The maximum extraction voltage was 10 ㎸. A numerical simulation was used to optimize the design of extraction grids and to predict an ion trajectory. As a result, the maximum ion current density was 38 ㎃/㎠ and the spread of ion energy was 1.6 % for the extraction voltage.
In focused ion beam (FIB) fabrication processes the ion beam intensity with Gaussian profile has a drawback for high resolution machining. In this paper, the fabrication method to modify the beam profile at substrate using silt mask is proposed to increase the machining resolution at high current. Slit mask is utilized to block the part of beam and transmit only high intensity portion. A nano manipulator is utilized to handle the silt mask. Geometrical analysis on fabricated profile through silt mask was conducted. By utilizing proposed method, improvement of machining resolution was achieved.
Electrical discharge machining (EDM) is one of the most extensively used non-conventional material removal process. The recent trend in reducing the size of product has given micro EDM a significant amount of research attention. Micro EDM is capable of machining not only micro holes and micro shafts as small as a few micrometers in diameter but also complex three dimensional micro cavities. But, longitudinal tool wear by electrical discharge is indispensable and this affects the machining accuracy in micro EDM process. Therefore, newly developed tool wear compensation strategy called round trip method is suggested and verified by experiment. In this method, machining depth of cut, overlap effect and critical travel length are also considered.
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