1,722,620 research outputs found
Study on the characteristics of III-Nitride semiconductor laser diodes
No full text학위논문(박사) - 한국과학기술원 : 물리학과, 2001.2, [ vi, 125 p. ]한국과학기술원 : 물리학과
THE PREDICTION OF THE CUTTING FORCE IN BALL-END MILLING WITH A FLEXIBLE CUTTER
No full textIn some situations, such as machining sculptured surfaces with long or slender ball-end mills, the cutter deflection in ball-end milling is a main factor affecting the machining accuracy. In this paper, a mechanistic cutting force prediction model of ball-end milling in consideration of cutter deflection is presented and its machining characteristics are discussed with experimental results. This model takes account of the changes in chip thickness by the deflection of a cutter and the cutter deflection is obtained by solving an equilibrium equation between cutting force and reaction force. The model was verified from the measurements of cutting forces for different machining conditions
PRECISION POCKETTING IN THE BALL END MILLING PROCESS
No full textMany die/mold parts including sculptured surfaces are usually completed by pocketting with ball end mill. Therefore the precision machining in pocketting is important. It has been noted that the tool deflection produced by the cutting force is a main cause of machining error in pocketting. The instantaneous deflection is dependent upon the static stiffness of tool and the instantaneous cutting force. In this study, the stiffness of holder was obtained by experiment and the stiffness of cutter was analyzed by the discrete elements along cutter length. The instantaneous cutting force was obtained by using the iteration method with the linear interpolation of basic machining data. By predicting the tool deflection in pocketting, a method improving the machining accuracy is suggested
A tool deflection compensation system for end milling accuracy improvement
No full textIn an effort to reduce machining surface errors due to tool deflection in the end milling process, methods regulating cutting forces have been implemented with online feed rate controls. Such schemes are able to improve the parts dimensional accuracy, but unfortunately they can exhibit undesirable aspects in which the alleviation of the cutting conditions deteriorates the productivity. In addition the frequent changes of the feed rate would spoil the surface quality. As a new approach to achieve the precision machining efficiently, this paper introduces a tool deflection compensation system. This compensation system is a computer controlled special tool adapter which is capable of measuring the cutting forces and minutely adjusting the position of the tool without interfacing with the NC controller of the milling machine. Such a system allows for on-line estimation of the teal deflections and reduction of the surface errors. Experimental investigations for typical shaped workpieces representing various end milling situations are performed to verify the ability of the system to suppress the surface errors due to tool deflections in more productive machining condition
An optimum 2.5D contour parallel tool path
No full textAlthough conventional contour parallel tool paths obtained from geometric information have successfully been used to produce desired shapes, they seldom consider physical process concerns such as cutting forces and chatter. In this paper we introduce an optimized contour parallel path that maintains a constant material removal rate at all times. The optimized tool path is based on a conventional contour parallel tool path. Additional tool path segments are appended to the basic path to achieve constant cutting forces and to avoid chatter vibrations over the entire machining area. The algorithm was implemented for two-dimensional contiguous end milling operations with flat end mills, and cutting tests were conducted to verify the performance of the proposed method
Dwell time algorithm for computer-controlled polishing of small axis-symmetrical aspherical lens mold
No full textWe describe a dwell time algorithm for the polishing of small axis-symmetrical aspherical surfaces. The dwell time distribution of the scanning polishing tool on the rotating workpiece is calculated to reduce the residual surface error. The dwell time at each discrete grid is calculated as an integer multiple of the workpiece rotation period, which is also useful for the spatially varying case in the local polishing area. A spherical polyurethane tool with abrasives is adopted for a computer-controlled polishing process. A linear algebraic equation of removal depth, removal matrix, and dwell time is derived by convolution of the removal depth at the dwell positions. The nonnegative least-squares method gives a solution to minimize residual error. Parametric effects such as the dwell grid interval are simulated. Finally, an experiment for tool mark removal is performed and the dwell time algorithm is evaluated to be valid. (C) 2001 Society of Photo-Optical Instrumentation Engineers
A CAD/CAM SYSTEM FOR PRECISION CAMS WITH 3 CNC INTERPOLATION METHODS
No full textDesign and manufacture of cams are complicated engineering tasks usually performed independently of each other. Therefore, a CAD/CAM system for cams would be very useful. The mathematical cam profile must be interpolated at some increment to create the numerical data for CNC machining. The interpolation method has significant effects on the dynamic performance. The focus of this paper is to develop a methodology of computer-aided design and manufacturing for precision cams by consideration of three CNC interpolation methods: linear, circular and R-Theta. Various aspects of the features of the interpolation method are explained and compared. The presented software can simulate a roughing and finishing sequence on a given cam blank. The computerised procedure is detailed with accompanying examples
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