• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.2
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• pp.9-16
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• 2004

Because a generated heat during grinding operation makes a serious deformation on a ground surface as a convex form, a real depth of cut in deformed zone has larger than an ideal depth of cut. Consequently, the ground surface has a geometric error as a concave form after cooling the workpiece. In this study, the force and the geometric error of surface grinding were examined. From evaluating magnitude and mode of the geometric error according to grinding conditions, an optimal grinding condition was proposed to minimize the geometric error. In addiction the relationship between the geometric error and the grinding force was found out. Due to least square regression it was able to predict the geometric error by using the grinding force.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.7 no.3
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• pp.41-46
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• 2008

Generally optical components are fabricated by grinding, lapping and polishing processes. Those processes take long time to obtain optical high surface quality. In the case of large optical components, the on-machine measurement is strongly recommended because the workpiece is fragile and difficult to set up for fabricating and measuring. This paper is concerned about a swing-arm mechanism which can be used for on-machine measurement of a surface profile with a sensing probe end-effect, and also for grinding or lapping the surface with a corresponding tool. The measuring accuracy and uncertainty using a swing arm type profilometer have been studied. The experimental results show that this method is useful specially in lapping process with the accuracy of $5{\mu}m$. Those inspection data are provided for correcting the residual figuring error in next processes.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.3 no.2
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• pp.10-17
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• 2004

A real depth of cut in deformed zone has larger than an ideal depth of cut. So the heat generated during grinding operation makes the deformation of a workpiece surface as convex farm. Consequently the workpiece surface remains a geometric error as concave form after cooling In this study, the grinding force and the geometric error were examined in surface grinding. Through magnitude and mode of geometric error were evaluated according to grinding conditions, an optimal grinding condition was proposed to minimize the geometric error In addition, the relationship between the geometric error and the grinding force was examined. Due to least square regression, It was possible to predict the geometric error by using the grinding force.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.826-830
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• 2000

Sculptured surface machining plays a vital role in the process of bring new Products to the market place. A great variety of products rely on this technology for the production of the dies and moulds used in manufacturing. And, the use or CNC machines and CAD/CAM system has become a vital parts or product development process. But, cusp is inevitable by-product in sculptured surface machining, and it is very difficult to calculate the cusp height correctly. In this study, an analytical cusp height model is proposed considering the radius of the ball end mill, radius of machined workpiece and the inclined angle of convex or concave circular surface. Experiments were performed to check the validity of this proposed model and experimental results showed that the proposed cusp model were very effective.

• International Journal of Precision Engineering and Manufacturing
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• v.7 no.4
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• pp.51-56
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• 2006

This paper proposes a control algorithm, which is verified experimentally, for aspherical surface grinding and polishing. The algorithm provides simultaneous control of the position and interpolation of an aspheric curve. The nonlinear formula for the tool position was derived from the aspheric equation and the shape of the tool. The function was partitioned at specific intervals and the control parameters were calculated at each control section. The position, acceleration, and velocity at each interval were updated during the process. A position error feedback was introduced using a rotary encoder. The feedback algorithm corrected the position error by increasing or decreasing the feed speed. In the experimental verification, a two-axis machine was controlled to track an aspherical surface using the proposed algorithm. The effects of the control and process parameters were monitored. The results demonstrated that the maximum tracking error with tuned parameters was at the submicron level for concave and convex surfaces.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.5
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• pp.40-49
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• 2010

Conical involute gears are being used for marine gearboxes, automotive transmissions, and robots, and so on, but not much. As involute profile gear, conical involute gear not only can be engaged with spur and helical gear but also can be used for power transmission of parallel, crossed and skewed axis with small angle. Hence, conical involute gears are likely to develop in future. Through a study on the basic theory of conical involute gear, tooth surface compressive stress analysis was performed by using commercial modeling program, comparing before and after profile modification. As a result, it noticed that tooth profile modification is able to relieve more tooth surface compressive stress than before modification.

• Korean Journal of Materials Research
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• v.22 no.10
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• pp.552-561
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• 2012

Diamond-like carbon (DLC) films have been widely used in many industrial applications because of their outstanding mechanical and chemical properties like hardness, wear resistance, lubricous property, chemical stability, and uniformity of deposition. Also, DLC films coated on paper, polymer, and metal substrates have been extensively used. In this work, in order to improve the printing quality and plate wear of polymer printing plates, different deposition conditions were used for depositing DLC on the polymer printing plates using the Pulsed DC PECVD method. The deposition temperature of the DLC films was under $100^{\circ}C$, in order to prevent the deformation of the polymer plates. The properties of each DLC coating on the polymer concave printing plate were analyzed by measuring properties such as the roughness, surface morphology, chemical bonding, hardness, plate wear resistance, contact angle, and printing quality of DLC films. From the results of the analysis of the properties of each of the different DLC deposition conditions, the deposition conditions of DLC + F and DLC + Si + F were found to have been successful at improving the printing quality and plate wear of polymer printing plates because the properties were improved compared to those of polymer concave printing plates.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.12 s.255
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• pp.1164-1172
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• 2006

Measurements of the local heat transfer coefficients on hemispherical convex and concave surfaces with a turbulent impinging jet were made. The Reynolds number used was 11000, 23000, 50000 and the nozzle- to- surface distance was L/d=2, 4, 6, 8, and 10 and the jet angle was a = $0^{\circ}$, $15^{\circ}$, $30^{\circ}$ and $40^{\circ}$. In case of concave surface, the Nusselt number at the stagnation point decreases as the jet angle increases and has the maximum value for L/d=6. The X-axis Nusselt number distributions exhibit secondary maxima at $0^{\circ}$ $\leq$ a $\leq$ $15^{\circ}$, L/d $\leq$ 4 for X/d<0(upstream) and at $0^{\circ}$ $\leq$ a $\leq$ $40^{\circ}$, L/d $\leq$ 4 and at $30^{\circ}$ $\leq$ a $\leq$ $40^{\circ}$, 4 < L/d $\leq$ 6 for X/d<0(downstream). The secondary maximum occurs at long distance from the stagnation point as the jet angle increases or the nozzle-to-surface distance decreases. In case of convex, correlations of the stagnation point Nusselt number according to Reynolds number, jet-to-surface distance ratio and dimensionless surface angle are presented. In the stagnation point, in term of Ren, n ranges from 0.43 in case of 2 $\leq$ L/d $\leq$ 6 to 0.45 in case of 6 < L/d $\leq$ 10, there agrees roughly appears to be laminar boundary layer result. The maximum Nusselt number, in this experiment, occurred in the direction of upstream. The displacement of the maximum Nusselt number from the stagnation point increases with increasing surface angle or decreasing nozzle-to-surface distance. On this condition about surface curvature D/d=10, the maximum displacement is about 0.7 times of the jet nozzle diameter. The ratio of the maximum Nusselt number to the stagnation Nusselt number increases as the jet angle increases.

• 한국전산유체공학회:학술대회논문집
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• 1997.10a
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• pp.131-135
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• 1997

Effect of wall curvature on flow characteristics is studied for mildly and strongly curved duct flows. The ducts are S-shaped, and the flow is partially blocked at the rear of the downstream. The presence of blockage in combination with curvature generates secondary flows on the concave surface; the magnitude of the secondary flow being dependent on the degree of wall curvature. Objectives are to compare the flow structures for mild and strong cases and to illuminate the changes in flow structure as the flow turns. Sensitivity on numerical solutions due to different inflow boundary conditions is also examined.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.9
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• pp.2089-2104
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• 1995

A novel and efficient cutter path planning method for machining intricately shaped curved surfaces, called the steepest directed tree method, is presented. The curved surface is defined by triangular facets, the density and structure of which are determined by the intricacy and form accuracy of the surface. Geometrical form definition and recognition of the topological features are used to connect the nodes of the triangulated surface meshes for the successive and interconnected steepest pathways, which makes good use of end milling characteristics. The planetary cutter centers are determined to locate along smoothly changing paths and then the height values of the cutter are adjusted to avoid surface interference. Several machined examples of intersecting and intricate surfaces are presented to illustrate the benefits of the new approach. It is shown that due to more consistent geometry matching between cutter and surface(in comparison with the current CC Cartesian method) surface finish can be typically improved. Moreover, the material in concave fillets which is difficult to be removed by ball mills can be removed efficiently. The built-in positioning of cutter to avoid interference runs minutely in the sharp and discontinuous regions. The steepest upward movement of the cutter gives a stable dynamic cutting state and allows increase in the feedrate and spindle speed while remaining the stable cutting state.