• Journal of the Korean Society for Precision Engineering
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• v.21 no.11
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• pp.99-109
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• 2004

This paper proposes precision evaluation method for the positioning error of three-DOF translational parallel mechanism. The proposed method uses conventional CMM as metrology equipment to measure the position of end-effector. In order to obtain accurate measurement data from CMM, the transform relationship between the coordinate system of the parallel mechanism and the CMM coordinate system must be identified. For this purpose, a new coordinate referencing (or coordinate system identification) technique is presented. By using this technique accurate coordinate transformation relationships are efficiently established. According to these coordinate transformation relationships, an equation to calculate error components at any arbitrary position of the end-effector is derived. In addition, mathematical fitting models to represent the position error components in the two-dimensional workspace of the parallel mechanism are also constructed based on response surface methodology. The proposed error evaluation method proves its effectiveness through the experimental results and its application to real three-DOF parallel mechanism.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.6
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• pp.68-73
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• 2009

One of the traditional optical methods to monitor a tool is a CCD sensor-based vision system which captures an aspect of the tool in real time. In the case using the CCD sensor, specific lens-modules are necessary to monitor the tool with higher resolution than its pixel size, and a microprocessor is required to attain desired data from captured images. Thus theses additional devices make the entire measurement system complex. Another method is to use a pair of an optical source and a detector per measuring axis. Since the method is based on the intensity modulation, the structure of the measurement system is simper than the CCD sensor-based vision system. However, in the case measuring the three dimensional position of the tool, it is difficult to apply to micro machine-tools because there may not be space to integrate three pairs of an optical source and a detector. In this paper, in order to develop a tool-origin measurement system which is employed in micro machine-tools, the improved method to measure a tool origin in x, y and z axes is introduced. The method is based on the intensity modulation and employs one pair of an optical source radiating divergent beams and a quadrant photodiode to detect a three dimensional position of the tool. This paper presents the measurement models of the proposed tool-origin sensor. The models were verified experimentally The verification results show that the proposed method is possible and the induced models are available for design.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.11
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• pp.134-141
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• 2003

An industrial product is designed and fabricated, followed by the inspection process in order to check whether it is dimensionally tolerable or not. The machining process produces a part such as a mold or die, in which the three-dimensional coordinate might be measured by a CMM (Coordinate Measuring Machine) for assessment of its dimension. It is not ignorable, however, that a CMM measurement requires a lot of operating time and cost, which has led to many studies on the OMM system. The OMM system can be categorized into contact and non-contact types, and each of which has its own strengths and weaknesses. Non-contacting types generally utilize structured lights, sounds or magnetic fields. Though they show rather poor performance in positional accuracy, the measuring speed is faster than the contacting probes. This paper presents the development of an OMM system based on a non-contacting laser displacement sensing apparatus and CAD model. The system is composed of software modules of center-aligning and measuring, which has been operated and verified on a NC machining center on a shop floor.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.2
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• pp.191-203
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• 2005

Statement of problem. In Korea, the preliminary impression trays for dental and edentulous maxillae are manufactured on the base of the statistical value of Westerners. There had been less study on the dental and edentulous arches of Koreans. Purpose. The purpose of this study was to evaluate an average dental cast, preliminary impression trays, three-dimensional relation of dental and edentulous maxilla of Koreans Material and methods. The subjects for this study were 173 dental casts of maxilla (dental: 52, edentulous : 146) with ages $18\{\sim}60$ years old. Each of the master casts was measured 69 measuring points on the dental cast or maxilla, and 46 measuring points on the edentulous cast of maxilla with three-dimensional digital measuring machine. Each measuring points were analysed and were overlapped, that three dimensional dental graphic manufactured by CAD/CAM system. Results. 1. A standard of distribution to alveolar bone were width between left and right buccal border lines of the standard 3/4 line. The mean value of dental and edentulous casts were 67.27mm, 63.49mm respectively. 2. Morphological classification of dental casts were divided into three groups or V-shape, O-shape, U-shape, that proportion of distribution were 17%, 16%, 67%, respectively. Dimensional classification of the dental casts were divided into five groups of less than 63mm, 63 up to 65mm, 65 up to 67mm. 67 up to 69mm, more than 69mm, respectively. 3. Morphological classification of edentulous casts were divided into three groups or V-shape, O-shape, U-shape, that proportion of distribution were 18%, 17%, 65%, respectively Dimensional classification of the edentulous casts were divided into five groups of less than 57mm, 57 up to 61mm, 61 up to 65mm, 65 up to 69mm, more than 69mm, respectively. 4. Mean dental and edentulous cast of maxilla were overlapped, the proportion of bone resorption to alveolar bone is higher than that of palatal bone, its difference were higher anterior 2/4 area than posterior 3/4 area. Conclusion. It obtains information of preliminary impression trays for dental and edentulous maxilla of Koreans.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.3
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• pp.56-62
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• 2022

The tank engine clutch flange constitutes a tank on which the engine and transmission of the tank are mounted. The engine clutch flange is fabricated using a difficult-to-cut material that exhibits high strength and hardness. It is difficult to process and requires considerable processing expertise. In addition, the engine clutch flange for the tank requires high machining precision because it is a system in which the connection is detachable. Because it requires high processing precision, the measurement of products equally important as processing. However, productivity is low owing to the significant amount of time required to measure each product using a three-dimensional coordinate measuring machine. Hence, this study is conducted to improve the productivity of the female tank engine clutch flange. Dedicated hobs and jigs are designed and manufactured to convert the existing end-mill cutting processing into hobbing cutting processing. An engine clutch for the tanks is manufactured using the manufactured dedicated hob and jig, and the shortening time is verified by measuring the processing time. In addition, a jig for inspection is designed and manufactured to measure the precision of the product. To verify the inspected product, the product precision is measured using a contact-type three-dimensional coordinate measuring machine and a surface roughness measuring instrument. The study confirmed that the productivity of the engine clutch flange product for tanks can be improved by simplifying the process, reducing the processing time, and simplifying product inspection.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.6
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• pp.918-924
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• 1997

A method for measuring the accuracy of rotating objects was studied. Rotating axis errors are significant; such as the spindle error of a manufacturing machine which results in the surface roughness of machined work pieces. Three capacitance type displacement sensors were used to measure the rotating master ball position. The sensors were mounted to the three orthogonal points on the spindle axis. The measurement data were analyzed and shown for rotating spindle accuracy, not only for average roundness error but also for spindle volumetric positional error during the revolutions. This method is simple and economical for industrial field use with regular inspection of rotating machines using portable equipment. Measuring and analyzing time using this method takes only a couple of hours. This method can also measure microscopic amplitude and 3-dimensional direction of vibrating objects.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.1
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• pp.144-149
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• 2008

This study presents the selection of cutting conditions in high speed pipe cutting machine for the better quality. A high speed pipe cutting machine which uses a rotary knife can make good quality products in short time. But, the machine is much sensitive by cutting conditions because of the complicated mechanism. In this reason, many experiments for cutting condition selection are necessary to improve quality of production. This study carried out cutting experiments with the three factors that are cutting RPM, cutting force and pooling force. 2-dimensional profile measuring instrument is used to measure which is represented by ${\Delta}h$, a sum of burr and collapse height. The effects of factors are analyzed by using MINITAB, the commercial software.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.371-374
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• 2002

From reverse-engineering's point of view, the main step is the digitizing or gathering three-dimensional points on the target physical model. As well known, the touch or scanning probe gives higher accuracy, while the non-contact digitizing apparatus by use of laser or structured light can rapidly obtain digitized points of great bulk without contacting onto the part surface of the physical model. We propose a digitizing methodology by use of the LK-031 laser displacement sensor, which was tested with a physical model.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.1
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• pp.73-79
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• 2013

In this study, NIMAX material has been processed using the three-dimensional measuring instrument and white light interferometer. they were tested to roundness and surface roughness and results are as follows: As for a cutting characteristic, it indicated that F4 showed a lower result than 2F showed due to the high hardness of the material and showed a good result when spindle rotation speed and tool feed were low. As for the measurement of roundness through 3-Dimensional measuring machine, it indicated that 4F showed a good result like the condition of cutting component and that roundness showed a good result when spindle rotation speed of 1,700 rpm and tool feed speed of 85 mm/min were applied. As for the surface roughness of processing surface, Surface roughness showed better 4F than 2F and conditions of spindle rotation speed 1,700 rpm, tool feed rate 55 mm/min showed good results in the Ra $0.4025{\mu}m$.

• The Journal of Korean Academy of Prosthodontics
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• v.37 no.3
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• pp.358-374
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• 1999

This study measured the relative displacements of the five-unit fixed partial dentures as cast with the same fixed partial dentures sectioned and assembled by investment-soldering, solder-ing stand-soldering, and cast-joining techniques A total of fifteen specimens using a type IV gold alloy were one-piece cast as control and then sectioned and assembled five test specimens for each method were prepared. A computerized three dimensional coordinate measuring machine and specially designed cylinder for this study were used. Displacement was defined by six displacement variables for the each of cylinders incorporated in each casting: three component displacements(${\Delta}Lx,\;{\Delta}Ly,\;and\;{\Delta}Lz$) and rotational displacements(${\Delta}{\theta}x,\;{\Delta}{\theta}y,\;{\Delta}{\theta}z$). The global displacement was computed using the mathematical formula ${\Delta}R$ = Global displacement =$\sqrt{{(x'-x)}^2+{(y'-y)}^2+{(z'-z)}^2}$ Under the conditions of this study, the following conclusions were drawn: 1. The investment-soldering group showed the largest mean value of final global displacements, followed by stand-soldering group, cast-joining group and one-piece cast group. However, between the mean values of final global displacement for the cast-joining group and one-piece cast group, there was no significant difference. 2. For investment-soldering and stand-soldering groups, the greater global displacements were recorded in soldering phase than in indexing or investing phase. 3. For one-piece cast group, the displacements occured mostly in the casting phase. And for cast-joining group, there was no significant difference in global displacements among the fabricating procedures. 4. Intercentroidal distance decreased in framework-patterning, solder-indexing, solder-standing, and soldering phases, but increased in investment block-investing and casting phases. 5 Specially designed cylinder for touch-trigger type coordinate measuring machine was validated.