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Application of optimisation techniques to planning and estimating decisions in the building processLaptali, Emel January 1996 (has links)
An integrated computer model for time and cost optimisation has been developed for multi-storey reinforced concrete office buildings. The development of the model has been based on interviews completed with Planners, Estimators and Researchers within 2 of the top 20 (in terms of turnover) UK main contractors, and on published literature, bar charts and bills of quantities of concrete framed commercial buildings. The duration and cost of construction of a typical multistorey reinforced concrete office building is calculated through the first part of the integrated model, i.e. the simulation model. The model provides a set of choices for the selection of materials and plant and possible methods of work. It also requires the user to input the quantities of work, gang sizes and the quantity of plant required, lag values between activities, output rates, unit costs of plant, labour costs and indirect costs. A linked bar chart is drawn automatically by using the data available from the simulation model. The second part of the model, (optimisation) uses the data provided by the simulation part and provides sets of solutions of time vs. cost from which the minimum project cost corresponding to the optimum project duration is calculated under the given schedule restrictions. Linear programming is used for the optimisation problem. The objective function is set to be the minimisation of the project cost which is the total of the direct costs of all the activities creating the project and the indirect costs of the project. The constraints are formulated from the precedence relationship, lag values, and normal and crash values of time and cost for the activities supplied by the simulation model. The simulation part has been validated by comparing and contrasting the results with those methods and practices adopted by commercial planners and estimators. The validation of the optimisation part has been undertaken by plotting time-direct cost curves from the results and checking the convexity of the curves. Additionally, the validation procedures included taking account of the opinions of practitioners in the industry on the practical and commercial viability of the model.
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Cost modelling for manufacturing of aerospace compositesMa, Weitao January 2011 (has links)
The application of composites has been increasing dramatically in aerospace structures recently, for example, composites have contributed over 50 percent of the structure mass of large transport airplanes Boeing 787 and Airbus 350XWB. However, the further usage has been restricted because of the high material and manufacturing costs. Hence, it is essential to utilize cost estimation tools for accurate cost estimation in the early design stages, and then efficient decisions and design optimizations could be made to reduce the cost of composite products. This research project aims to develop a cost model for aerospace carbon fibre reinforced plastic (CFRP) composites, which will help designers and cost engineers with the cost estimation for composites manufacturing in the early development stages. The main objectives of the research are to: (i) recognise the standard manufacturing stages and activities of CFRP components; (ii) identify the cost drivers of composites manufacturing; (iii) identify the cost estimation relationships; (iv) develop a cost model that can assist designers and engineers with manufacturing cost estimation for CFRP components; (v) validate the developed cost model through case studies and expert judgements. The process of model development was carried out through four main steps: firstly, conducting an integrated understanding of cost modelling for composites manufacturing; secondly, collecting data for cost modelling from industry and existing literature and databases; thirdly, developing the cost model with several function modules and databases; and finally, taking a validation of the developed model. The developed cost model consists of several modules: material selection, process planning, cost estimation, cost reporting and a user friendly interface. Moreover, the selection and planning modules are combined with databases including material and process. The developed model enables the user to estimate the manufacturing cost and process time of CFRP composites, and it can also help designers realize the impact of design changes on the manufacturing cost. The process planning can efficiently help estimators with manufacturing process understanding and accurate time estimation. Quality control activities are time consuming and investment sensitive in composites manufacturing.
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Cost model for rapid manufacturingTuomi, J., Karjalainen, J. January 2006 (has links)
Published Article / At Helsinki University of Technology rapid prototyping, rapid tooling and rapid manufacturing technologies and applications have been researched since late 1980s. The Integrated Design and Manufacturing research group has concentrated on new industrial Rapid Prototyping and Manufacturing (RP&M) applications within product development and manufacturing. This paper is based on research projects realized in 2001 - 2004 in cooperation with several industrial companies. New developments within industrial product development paradigms and processes will be discussed. The paper attempts to link current industrial management sciences research with latest developments within rapid manufacturing technologies. Product platforms, product customization and networked manufacturing have become common product development management paradigms in many industrial sectors. These paradigms have lead to an increasing number of product configurations and variations. Traditionally cost comparisons between RP&M processes and conventional manufacturing processes have been based on break even point calculations. The latest product development and manufacturing paradigms places agility in production and efficient prototyping technologies among others in an important role. Conventional cost per part comparison methods to value rapid manufacturing need to be re-engineered. In those comparisons the first break even point does not describe the overall rapid manufacturing economy. For example, effects of neccesity for product change, tool wear or tool defect have to be taken into consideration. In this paper the new cost modeling technology and some industrial case studies will be described.
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Cost modelling system for lean product and process developmentAhmad, Wasim January 2012 (has links)
This PhD project aims to develop a cost modelling system to support lean product and process development. The system enables the designers to assess the design along with associated manufacturing processes and provides decision support at an early development stage. Design assessment at early development stage can help designers to take proactive decisions, eliminate mistakes and enhance product value. The developed cost modelling system to support lean product and process development incorporates three lean product and process development enablers, namely set-based concurrent engineering, knowledge-based engineering, and mistake-proofing (poka-yoke). To facilitate above explained lean enablers, the system architecture contains six modules, six separate groups of database, a CAD modelling system, and a user interface. The system modules are: (i) value identification; (ii) manufacturing process/machines selection; (iii) material selection; (iv) geometric features specification; (v) geometric features and manufacturability assessment; and (vi) manufacturing time and cost estimation. The group of database includes: (i) geometric features database, (ii) material database, (iii) machine database, (iv) geometric features assessment database, (v) manufacturability assessment database, and (vi) previous projects cost database. A number of activities have been accomplished to develop the cost modelling system. Firstly, an extensive literature review related to cost estimation, and lean product and process development was performed. Secondly, a field study in European industry and a case study analysis were carried out to identify current industrial practices and challenges. Thirdly, a cost modelling system to support lean product and process development was developed. Finally, validation of the system was carried out using real life industrial case studies. The system provides a number of benefits, as it enables designers to incorporate lean thinking in cost estimation. It takes into consideration downstream manufacturable process information at an early upstream stage of the design and as a result the designer performs the process concurrently and makes decisions quickly. Moreover, the system helps to avoid mistakes during product features design, material and manufacturing process selection, and process parameters generation; hence it guides toward a mistake-proof product development. The main feature of the system, in addition to manufacturing cost estimation, is set-based concurrent engineering support; because the system provides a number of design values for alternative design concepts to identify the feasible design region. The major contribution of the developed system is the identification and incorporation of three major lean product and process development enablers, namely set-based concurrent engineering, knowledge-based engineering and poka-yoke (mistake-proofing) in the cost modelling system. A quantification method has been proposed to eliminate the weaker solution among several alternatives; therefore only the feasible or strong solution is selected. In addition, a new cost estimation process to support lean product and process development has been developed which assists above explained three lean product and process development enablers.
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Intermodal Transport Cost Model and Intermodal Distribution in Urban FreightKordnejad, Behzad January 2013 (has links)
This study aims to model a regional rail based intermodal transport system and to examine the feasibility of it through a case study for a shipper of daily consumables distributing in an urban area and to evaluate it regarding cost and emissions. The idea of an intermodal line train is that of making intermediate stops along the route thus enabling the coverage of a larger market area than conventional intermodal services, hence reducing the high cost associated with feeder transports, the congestion on the road network and generated externalities. The results of the case study indicate that the most critical parameters for the feasibility of such a system are the loading space utilization of the train and the cost for terminal handling. / <p>QC 20130531</p> / Regional kombitransportsystem i Mälardalen
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Robotic approach to low-cost manufacturing of 3D preforms with dry fibresSharif, Tahir January 2012 (has links)
High-performance fibres such as carbon, glass and kevlar are very promising for aerospace applications because of their high strength, stiffness, impact damage and excellent fatigue life. The high cost of the prepreg materials such as pre-impregnated fibre tape/tow and fabrics, and limitations of existing manufacturing processes are a big challenge for the aerospace industry to meet increasing performance demands. Their benefits can only be achieved by using low cost materials and manufacturing methods. In the past three or four decades, there have been substantial technological developments, which are governed by the new materials and their associated manufacturing techniques. The production of carbon fibre is slow and capital intensive, therefore, carbon manufactures produce higher tow counts (number of filaments) to increase production through-put in order to reduce its cost. In other words, 12k carbon tow is much cheaper than 6k or 3k carbon tow. In many applications finer tows are desirable. In this thesis, a fully automated laser feedback tow splitting line has been developed to split higher tow counts (12k spool) into smaller tow counts (split into 6k spools) in order to produce low cost material. The quality of the split tows has been evaluated by recording the data online during the splitting process. The recorded data was later analysed by statistical tools. A four axis modular gantry robotic system has been developed at the University of Manchester in order to deposit dry fibres in a completely flexible manner. To facilitate robotic preforming, an end-effector and mould have been designed and developed in this research. The tow placement program was written in the CoDeSys software which is then uploaded into the motion controller to perform specific motions. The cross-ply laminates have been manufactured by the proposed robotic system using split 6k (produced by the tow splitting process) and original 12k carbon tows. Mechanical test of both composites (12k and split 6k) are presented. A tufting process has been developed and conducted by the robotic system in order to manufacture 3D preforms. The tufted composite was compared with 3D woven and stitched 2D broadcloth in terms of the tensile and interlaminar shear strength properties. X-ray tomography has been conducted to investigate preform geometrical variations of manufactured composites. In addition, preforming cost models have been developed for robotic fibre placement and 3D weaving.
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Supporting system deployment decisions in public cloudsKhajeh-Hosseini, Ali January 2013 (has links)
Decisions to deploy IT systems on public Infrastructure-as-a-Service clouds can be complicated as evaluating the benefits, risks and costs of using such clouds is not straightforward. The aim of this project was to investigate the challenges that enterprises face when making system deployment decisions in public clouds, and to develop vendor-neutral tools to inform decision makers during this process. Three tools were developed to support decision makers: 1. Cloud Suitability Checklist: a simple list of questions to provide a rapid assessment of the suitability of public IaaS clouds for a specific IT system. 2. Benefits and Risks Assessment tool: a spreadsheet that includes the general benefits and risks of using public clouds; this provides a starting point for risk assessment and helps organisations start discussions about cloud adoption. 3. Elastic Cost Modelling: a tool that enables decision makers to model their system deployment options in public clouds and forecast their costs. These three tools collectively enable decision makers to investigate the benefits, risks and costs of using public clouds, and effectively support them in making system deployment decisions. Data was collected from five case studies and hundreds of users to evaluate the effectiveness of the tools. This data showed that the cost effectiveness of using public clouds is situation dependent rather than universally less expensive than traditional forms of IT provisioning. Running systems on the cloud using a traditional 'always on' approach can be less cost effective than on-premise servers, and the elastic nature of the cloud has to be considered if costs are to be reduced. Decision makers have to model the variations in resource usage and their systems' deployment options to obtain accurate cost estimates. Performing upfront cost modelling is beneficial as there can be significant cost differences between different cloud providers, and different deployment options within a single cloud. During such modelling exercises, the variations in a system's load (over time) must be taken into account to produce more accurate cost estimates, and the notion of elasticity patterns that is presented in this thesis provides one simple way to do this.
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