• Journal of Mechanical Science and Technology
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• 제15권2호
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• pp.160-171
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• 2001

Depending upon the method of the surface generation and the quality of the designed boundary curves, the resulting surfaces may have global or local irregularities in many cases. Thus, it would be necessary for the designer to evaluate the surface quality and to modify the surface. This is very important because the defect of the surface causes the rework of the dies, increasing cost and delivery time significantly. To simulate the reflection line test in the actual production line, a faster algorithm for generating reflection lines is presented. In this paper, among various surface interrogation methods using reflection lines, Blinn-Newell type of reflection mapping is applied to generate the reflection lines on the trimmed NURBS surfaces. The derivation of reflection lines is formulated as a surface-plane intersection problem (Jung 1994) and is solved by surface-contouring techniques. Also, for eliminating the discontinuity of reflection lines due to the configuration of reflection map, a modified reflection map is proposed. An efficient traced contouring technique is utilized for the computational efficiency and proves to be well suited for the real-time quality-assessment task.

• 대한산업공학회지
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• 제34권3호
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• pp.337-343
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• 2008

The problem of determining the optimum metal plating thicknesses on the plane and curved surfaces of an electronic part is considered. A lower specification limit for the plating thickness is usually pre-specified. In most applications, the plating thickness on the curved surface is proportional to that on the plane surface. The proportion can be adjusted by adding chemical catalysts to the plating fluid. From the economic point of view, nonconforming items with a thickness smaller than the lower specification limit incur rejection costs, such as rework and scrap costs, while a thicker plating may incur an excessive material costs. In this article, an economic model is proposed for simultaneously determining the target plating thickness and the ratio of the plating thickness on the plane surface to that on the curved surface. An illustrative example demonstrates the applicability of the proposed model.

• 한국소음진동공학회논문집
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• 제26권4호
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• pp.420-427
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• 2016

Diverse research on gearing systems have been made to resolve gear NVH problems for many decades, and transmission error (T.E.) has been identified as one of the main sources generating gear noises. While gear profiles and amounts of tooth modifications have influences on gear noise in the design aspect, it is found that bad manufacturing conditions such as burrs, bumps and damage, which result in improper gear operating conditions, produce gear noise with respect to manufacturing process. In this paper, T.E. measurement system was introduced to examine the gears damaged or improperly manufactured, while they are assembled, by comparing T.E. values and various gear conditions with theoretical ones. This T.E. measurement system, following grinding machining process, has been installed in a manufacturing line in 2014, and it results that the transmission rework to resolve manufacturing problems is not needed at the end of line.

• Journal of Construction Engineering and Project Management
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• 제5권2호
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• pp.24-34
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• 2015

The complexity arises in defining the construction quality due to its perception, based on inherent market conditions and their requirements, the diversified stakeholders itself and their desired output. A quantitative survey based approach was adopted in this constructive study. A questionnaire based survey was conducted, for the assessment of construction quality perception and expectations in the context of quality improvement technique. The survey feedback of professionals, from the leading construction organizations/companies of Pakistan were analyzed. The financial capacity, organizational structure, and construction experience of the construction firms formed basis for their selection. After statistical analysis of survey feedback it was found reliable and valid for the inferential purpose to the target population of construction professionals. The quality perception was found to be project scope oriented, considered as an excess cost for a construction project and keeping the rework minimum by qualifying the required quality tests, keeping the defects minimum by ensuring the specifications of supplied material. Any quality improvement technique was expected to address the financial aspects of the construction project for the employer and contractor, by increasing the profitability through reduction in overall cost, reduction in time, reduction in defects and improving the productivity in a construction project. The study is beneficial for the construction professionals to assess the prevailing construction quality perception and the expectations from implementation of any quality improvement technique in construction projects.

• 산업경영시스템학회지
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• 제18권34호
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• pp.155-159
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• 1995

For the relationship between conformance cost and the individual elements of non-conformance, an analysis was made of the relationship between inspection cost and training cost and scrap cost. As a result it was explained that there was all a positive correlation between training cost and scrap cost, and between inspection cost and scrap cost. Like this, training and inspection cost and scrap cost have a positive correlation. Judging from the fact that the coefficient of inspection cost is lower than that of training cost in the comparison of the coefficient of each cost, it can be analyzed that the change in scrap cost is influenced by the change in training cost more greatly than the change in inspection cost. If doing so, it can be interpreted that scrap cost and rework cost do not still decrease in spite of increasing in education and training cost and prevention cost. This result may represent the problem as to whether education and training cost is effectively expended for prevention activity. Accordingly, to cope with this situation, it is thought that scrap cost should be cut by establishing the effective prevention measure for causing the increase of scrap cost.

• 산업경영시스템학회지
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• 제37권4호
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• pp.231-238
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• 2014

Optimum lot size calculation for real world manufacturing environment has been focused since last few decades. Several extensions have been made to the basic economic order and production order quantity models to realize the possible practical situations in industry. However, focus on work-in-process inventory has been ignored relatively. This paper provides a comprehensive review of the models developed for group technology based manufacturing environment focusing on work-in-process inventory. Models have been extended from a perfect manufacturing conditions to an imperfect manufacturing situation considering rework, rejection and inspection. Optimum lot size has been evaluated using a simple algebraic optimization approach. Significant parameters are highlighted using sensitivity analysis for the developed models. Numerical example is used to illustrate the utilization of such models in day-to-day production setups and the impact of significant factors' variation on total cost and optimum lot size.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2001년도 Proceedings of 6th International Joint Symposium on Microeletronics and Packaging
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• pp.27-34
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• 2001

The BGA Package has been the area array package of choice for several rears. Recently, the transition has been to finer pitch configuration called Chip Scale Packages (CSP). Several of these package types are available at 0.5 mm pitch, requiring surface mount assemblers to evaluate and optimize various elements of the assembly process. This presentation describes the issues associated with making the transition from BGA to CSP assembly. Areas addressed will include the accuracy of pick and piece equipment, printed wiring board lines and spaces, PWB vias, in-circuit test issues, solder paste printing, moisture related factors, rework and reliability. The transition to 0.5 mm pitch requires careful evaluation of the board design, solder paste selection, stencil design and component placement accuracy. At this pitch, ball and board pad diameters can be as small as 0.25 mm and 0.20 mm respectively. Drilled interstitial vias are no longer possible and higher ball count packages require micro-via board technology. The transition to CSP requires careful evaluation of these issues. Normal paste registration and BGA component tolerances can no longer achieve the required process levels and higher accuracy pick and place machines need to be implemented. This presentation will examine the optimization of these critical assembly operations, contrast the challenges at 0.5 mm and also look at the continuation of the process to incorporate smaller pitch flip chip devices.

• 한국CDE학회논문집
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• 제19권4호
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• pp.368-389
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• 2014

There are many agendas and discussion subjects for BIM-based Criteria Design phase. At that time, some problems are occurred by software compatibility, simple repetitive tasks, rework caused by missing information etc. In this study, we focus on solving that problems by applying API(Application Programming Interface) method. For effective study, we construct Criteria Design process by using DSM (Dependency Structure Matrix) and study applicability of API. It will be effective for time-consuming task and simply labor-intensive tasks by applying API. we expect improving BIM-based Design Process and Data quality, work productivity without missing information and shapes for using API.

• Journal of Construction Engineering and Project Management
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• 제6권1호
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• pp.11-19
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• 2016

Most of the Indian contractors are not well equipped to handle the growing demand of infrastructure development; hence construction projects frequently run in to time and cost overruns, disputes and quality issues. This study aims to improve the construction industry in India by implementing lean principles to eliminate non-value adding activities (wastes). The purpose of this study is to 1) identify the wastes and their sources affecting the construction process, and 2) to identify problems and document lessons by applying a Last Planner System (LPS) to a sample project. First, the researchers identified that Delays, Rework, and Interruptions were the most critical wastes affecting the construction process and Poor management control, Poor Planning and Shortage of Resources were the major sources of the above mentioned wastes. Second, the researchers report the Percent of Planned Complete (PPC) analysis results and experienced problems after implementation of LPS at the sample project. It was observed that much more improvement could have been achieved if there was consensus between the owners and the contractor on the implementation of the LPS in its entirety. Some of the problems experienced in the implementation of the LPS like lack of scheduling, resource and material shortage were found to be similar to those in developed countries.

• Design & Manufacturing
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• 제16권1호
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• pp.21-26
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• 2022

In the CNC machining process, problems such as lowering of machine operation rate, setting errors, and machining precision occur due to the increase in setting time and preparation time. These machining errors cause delays in delivery and increase in cost due to an increase in the number of mounting and dismounting of the workpiece, an increase in measurement and reprocessing time, and an increase in the finishing time in the assembly process. Therefore, in this study, by automating the setting of the work piece using OMV (On Machine Verification), which is a meteorological measurement system, the preparation time for machining the work piece and the setting accuracy were improved, the rework rate was reduced, and the mold manufacturing process was shortened. Through the advancement, standardzation, and automation of the mold part manufacturing process, we have improved productivity by minimizing low-value-added repetitive tasks. In addition, the measurement time was reduced by more than 50% and the machining measurement rate was improved by more than 20%, eliminating repetitive work for correcting machining defects, and reducing the work preparation time by more than 15% through automatic setting.