Browsing by Subject "Manufacturing processes -- Data processing"
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Item An investigation of parts flow in the flexible manufacturing system(Texas Tech University, 1983-05) Napierala, ElzbietaA certain Flexible Manufacturing System was investigated. The line of the system consists of four machines, a queueing area, and a material handling system represented by a cart. The main objective of this study was to investigate the effects of different levels of cart utilization, local storages, and the size and design of the queueing area on the FMS performance. Additionally, the examination of different scheduling rules was conducted in order to see their impact on the FMS performance. Simulation was the chosen methodology for investigating the above stated issues. The GPSS/H simulation language was used to simulate the model of the examined FMS and to investigate the stated problems. Cart utilization was defined as the ratio of the total time that the cart was in use to the total time of the system operation. Different levels of cart utilization were obtained by changing the processing times of the part mixes manufactured in the system. The main criteria for the FMS examined were the number of parts and operations completed, as well as the machine utilization. The experimental results showed that the FMS was strongly affected by increasing cart, or generally speaking, material handling utilization. When a high level of cart utilization was experienced, this caused machine utilization and therefore, system productivity to decline. Cart utilization is a dependent variable in any FMS, an effect of several factors in the FMS design. The major components of material handling utilization are travel times, number of machines in the system, and part processing times. A ratio factor R, taking into account the above factors was proposed and the curve between the ratio R and cart utilization was developed. The FMS proposed by the General Dynamics in Fort Worth, Texas was used to test the ability of the developed curve to predict the material handling utilization for a different system. The theoretical cart utilization based on the ratio R and the developed curve, was very close to the material handling utilization obtained through the simulation. Adding local storages to the system configuration reduced the machine idleness due to the lack of cart service. The highest improvement in the system productivity after installing local storages was observed for the FMS operating with a cart utilization of 75% - 97%. The experimental results showed that the system was very sensitive to any changes in the configuration which caused cart utilization to increase. Providing more queueing stations by expanding the line length, and therefore increasing cart utilization, resulted in poorer performance of the FMS. The effects of the number of parts in process on the system productivity was examined by changing the size of the queueing area. The experimental results indicated that a given FMS provided the best performance with a certain number of parts in process. Expanding the queueing area above this level did not produce the better system output; on the other hand too few parts in process led to lower machine utilization. The experimental results showed that for the FMS examined, such rules as SPT, SPT*TOT or FCFS to system, provided the most balanced demands for all machines and therefore the highest system output. It was noted that the scheduling problem in the FMS should be carefully investigated for any system developed in terms of the production and configuration characteristics.Item Form feature and tolerance transfer from a three-dimensional solid model to a setup planning system(Texas Tech University, 1996-08) Zhou, FengProcess planning, like most other computer-aided engineering applications, requires the definition of product geometry as input (Shah and Mantyla, 1996). But the geometric information alone is insufficient. Process planning needs additional data on the shapes, such as their dimensions, locations, tolerances, and surface finish. The information should also cover more specialized factors including tool accessibility, fixturing possibihties, and inspectability. Therefore, product data transfer is important and necessary in automated process planning. However, most CAD systems, even the feature-based design systems which was developed as the need of CAPP, cannot provide exact information, such as dimensions and tolerances, of an object. Until now, most CAD modelers care more about the geometry of a part than other product information, but in fact, the product data, including tolerance information, is absolutely cmcial to CAPP. To realize product data transfer, feature-based design is very instmmental although it has not fulfiUed its promises yet One of objectives in this research is to modify a product data file, which is an exported file of a feature-based CAD system, in order to obtain exact product information which can be used by a CAPP system.Item The methodologies of system analysis and design for computer integrated manufacturing (CIM)(Texas Tech University, 1986-12) Scoggins, Shwu-yan ChangThis paper investigates the methodologies of system analysis and design for a CIM system from the software engineer's point of view. The hypotheses of this research are: 1) particular methodologies are likely to be suitable for a specific application system, 2) a combination of methodologies generally can make analysis and design more complete, and 3) analysis of their characteristics can be used to select a methodology capable of providing system specifications for software development and system implementation. To confirm the hypotheses, nine design methodologies are chosen to analyze five application systems. Each methodology and application system has its own characteristics. If the hypotheses are true, it will be possible to match the characteristics of the methodologies with corresponding characteristics of a particular system. Also, once the methodologies are used, they should yield information that provides a set of usable system specifications, and lead to a successful programming environment and implementation of the system. The nine methodologies are SD (Structured Design), MSR (Meta Stepwise Refinement), WOD (Warnier-Orr Design), TDD (Top-Down Design), MJSD (Michael Jackson Structured Design), SADT (Structured Analysis and Design Technique), PSL/PSA (Problem Statement Language/Analyzer), HOS (Higher Order Software), and HIPO (Hierarchy-Input-Process-Output). The five application systems are an overall CIM system, shop floor control subsystem, product design subsystem, production planning/scheduling subsystem, and inventory control subsystem. The characteristics of the methodologies include: system complexity, data structures, data flow, functional structures, process flow, decoupling structure clash recognition, logical control, and data flow control. The characteristics of the application systems include: system complexity, functional structures, process flow, data structures, logical control, data flow control, cohesion, and coupling. The contributions of this research include a technique for applying Information Technology to manufacturing information problems, and a set of rules for combination of different methodologies to improve the results of analysis and design efforts.