| 1. |
- Björklund, Stefan, et al.
(författare)
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Compensation of systematic errors in five-axis high-speed machining
- 2002
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Ingår i: International Journal of Production Research. - : Informa UK Limited. - 0020-7543 .- 1366-588X. ; 40:15 SPEC., s. 3765-3778
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Tidskriftsartikel (refereegranskat)abstract
- A method is described for the compensation of errors associated with tool path generation, particularly during five-axis high-speed machining (HSM). Information on machine tool performance and its dynamic features is used to calculate possible errors and convenient modifications of the NC program, thereby avoiding errors when parts are actually being machined. This 'preprocess method' by means of postprocessing with NC software is presented. The errors dealt with are mainly servo lag errors, but the explored approach can support most systematic errors associated with machine tool performance. These are briefly summarized. Research so far has largely been aimed at the implementation of compensation routines in the CNC controller and at corrections in real time. The problem is that most applications are only available for three-axis milling. The presented approach (compensation before machining by using software routines in a specially designed postprocessor) is based on a fuzzy logic expert system. The benefits can be summarized as data reduction, data improvement, precontrol of feed, and improved component accuracy. The applied procedure is also convenient for implementation in an industrial environment by retrofitting existing equipment. The suggested method provides improved control over machine dynamics, permitting high-speed machining centres to maintain a maximum or near-maximum feed rate despite axis reversals and tool path changes, even at corners. Two categories of results are presented, namely the management of NC data related to expected performance of the machine tool and improvements of the machine tool performance in terms of productivity and accuracy of the machined test components.
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| 2. |
- Christmansson, Marita, et al.
(författare)
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Modified method time measurements for ergonomic planning of production systems in the manufacturing industry
- 2000
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Ingår i: International Journal of Production Research. - : Taylor & Francis. - 0020-7543 .- 1366-588X. ; 38:17, s. 4051 - 4059
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Tidskriftsartikel (refereegranskat)abstract
- The paper reports on an evaluation of a method called ErgoSAM. This method is based on SAM, a higher-level method-time-measurement (MTM) system, and is for use by production planners, e.g. production engineers. In addition to the SAM information, the ErgoSAM method considers information on weight handled or forces applied, and work zone. The method is designed to predict the physical demands of work postures, force and repetitivity, according to a scientific model, the Cube model. In co-operation with the Volvo Car Corporation, six workstations of an assembly line, were analysed by a production engineer using ErgoSAM. The total assembly time analysed was about 17 minutes. The results were compared to results from ergonomic analyses made by an ergonomist using the Volvo Car Corporations standards. The results showed that ErgoSAM predicts work situations of high physical stress for the workers. However, the method does not consider stressful positions for the hand, wrist and neck or mental stress. The production engineer judged the ErgoSAM analyses to require about 5% more time than SAM analyses alone. It is concluded that the method shows considerable promise for predicting physically stressful work situations, but needs to be further evaluated and refined.
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| 3. |
- Disney, S. M., et al.
(författare)
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Economic consequences of a production and inventory control policy
- 2004
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Ingår i: International Journal of Production Research. - : Informa UK Limited. - 0020-7543 .- 1366-588X. ; 42:17, s. 3419-3431
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Tidskriftsartikel (refereegranskat)abstract
- The economic performance of a generalized Order-Up-To policy is investigated in response to an Auto Regressive stochastic demand process. Focus is on the case where the physical production/distribution lead time is one period and where demand is forecasted with simple exponential smoothing. Two sets of convex piece-wise linear costs are considered. The first set is the traditional inventory holding and backlog costs. The second set of costs is piece-wise linear and increasing convex costs associated with the production order rate within and above a capacity constraint. Numerical investigations reveal that the classical Order-Up-To policy is no longer optimal when a broader range of costs is considered in the objective function.
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| 4. |
- Grubbström, Robert W., et al.
(författare)
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Introducing capacity limitations into multi-level, multi-stage production-inventory systems applying the input-output/Laplace transform approach
- 2000
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Ingår i: International Journal of Production Research. - : Informa UK Limited. - 0020-7543 .- 1366-588X. ; 38:17, s. 4227-4234
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Tidskriftsartikel (refereegranskat)abstract
- The Laplace transform and Input-Output Analysis have been used to formulate a theoretical basis for Material Requirements Planning (MRP). In this paper, as a first step to incorporating capacity limitations into this theory, we introduce alternative formulations of a model for capacity-constrained production-inventory systems in a deterministic environment applying the same approach. We focus our attention on the way in which the balance equations constraining the system need to be modified. A numerical example is given to explain the model.
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| 5. |
- Johansson, Eva, et al.
(författare)
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The information gap between design engineering and materials supply systems design
- 2004
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Ingår i: International Journal of Production Research. - : Informa UK Limited. - 0020-7543 .- 1366-588X. ; 42:17, s. 3787-3801
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Tidskriftsartikel (refereegranskat)abstract
- This paper focuses on the design of materials supply systems in product development projects. In order to design the materials supply system in parallel with the product, product data must be available to the materials supply systems designers. The aim of this paper is to analyse the information quality of the required product data and to indicate how this information quality can be increased. Empirical data have been gathered through case studies conducted within the Manufacturing Industry. The empirical data show that it is possible to identify the product data required for materials supply systems design. It is also shown that there is an information gap between design engineering and materials supply systems design. The information quality of the required product data for the materials supply systems design has many imperfections, mainly in terms of accessibility, ease of operation, timeliness, understandability, interpretability, relevancy, and completeness. The information quality can be improved by the use of PDM systems, which are especially useful for facilitating an increase in accessibility, ease of operation, and timeliness.
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| 6. |
- Li, Xiaoqian, et al.
(författare)
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Machine Vision Based Surface Finish Inspection for Cutting Tool Replacement in Production
- 2004
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Ingår i: International Journal of Production Research. - : Informa UK Limited. - 0020-7543 .- 1366-588X. ; 42:11, s. 2279-2287
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Tidskriftsartikel (refereegranskat)abstract
- A quick and reliable assessment of machined surface finish is required for quality control in shop floors. This paper presents a machine-vision-based approach to inspect the turned surface in finishing operations. The distribution pattern from a laser scattering image is used to characterize the topography of the surface finish and to set criteria for cutting tool replacement. Compared with conventional surface inspections, this approach gives a feasible solution to assure machined surface finish and to establish reasonable criteria for cutting tool replacement in production.
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| 7. |
- Neumann, Patrick, et al.
(författare)
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A case study evaluating the ergonomic and productivity impacts of partial automation strategies in the electronics industry
- 2002
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Ingår i: International Journal of Production Research. - : Informa UK Limited. - 0020-7543 .- 1366-588X. ; 40:16, s. 4059-4075
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Tidskriftsartikel (refereegranskat)abstract
- A case study is presented that evaluates the impact of partial automation strategies on productivity and ergonomics. A company partly automated its assembly and transportation functions while moving from a parallel-batch to a serial line-based production system. Data obtained from company records and key informants were combined with detailed video analysis, biomechanical modelling data and field observations of the system. The new line system was observed to have 51% higher production volumes with 21% less per product labour input and lower work-in-process levels than the old batch-cart system. Partial automation of assembly operations was seen to reduce the total repetitive assembly work at the system level by 34%. Automation of transportation reduced transport labour by 63%. The strategic decision to implement line-transportation was found to increase movement repetitiveness for operators at manual assembly stations, even though workstations were constructed with consideration to ergonomics. Average shoulder elevation at these stations increased 30% and average shoulder moment increased 14%. It is concluded that strategic decisions made by designers and managers early in the production system design phase have considerable impact on ergonomic conditions in the resulting system. Automation of transport and assembly both lead to increased productivity, but only elements related to the automatic line system also increased mechanical loads on operators and hence increased the risk for work-related disorders. Suggestions for integrating the consideration of ergonomics into production system design are made.
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| 8. |
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| 9. |
- Persson, Jan, 1972-, et al.
(författare)
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A Tabu Search Heuristic for Scheduling the Production Processes at an Oil Refinery
- 2004
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Ingår i: International Journal of Production Research. - : Taylor & Francis. - 0020-7543 .- 1366-588X. ; 42:3, s. 445-471
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we present a tabu search heuristic which can be used for scheduling the production at an oil refinery. The scheduling problem is to decide which production modes to use at the different processing units at each point in time. The problem is a type of lot-sizing problem where costs of changeovers, inventories and production are considered. In the suggested tabu search heuristic we explore the use of variable neighbourhood, dynamic penalty and different tabu lists. Computational results are presented for different versions of the heuristic and the results are compared to the best-known lower bound for a set of scheduling scenarios.
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| 10. |
- Segerstedt, Anders
(författare)
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Frequency approach for treating capacity-constrained multilevel production
- 2004
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Ingår i: International Journal of Production Research. - : Informa UK Limited. - 0020-7543 .- 1366-588X. ; 42:16, s. 3119-3137
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Tidskriftsartikel (refereegranskat)abstract
- An idea about how to tackle and solve the difficult problem of determining economic order quantities in capacity-constrained multilevel production is presented. The idea is based on frequencies during a variable time interval as variables instead of explicit order quantities. The presented heuristic model handles assumed constant demand for several items and calculates fixed-order quantities assumed to be possible to repeat in a cyclic pattern. In the model, every item is supposed to be manufactured at least once per year, or during another maximum period, to stop order quantities that are too large and therefore hinder inventories that are exceedingly large and/or obsolete. During a time interval, it was decided how many times each item should be produced. The paper starts with a common frequency for all items, i.e. the highest frequency possible for all items during this maximum time interval considering the capacity restrictions of the different machines. Thereafter, the frequency for items with high set-up costs compared with the inventory holding costs is reduced if it decreases the total cost of set-ups and inventory holding. Only frequencies in multiples of two are used to make a cycle policy easier to establish, to prevent remnant stocks and to make the used cost approximation fit more accurately.
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| 11. |
- Tang, Ou, et al.
(författare)
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Economic evaluation of disassembly processes in remanufacturing systems
- 2004
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Ingår i: International Journal of Production Research. - : Informa UK Limited. - 0020-7543 .- 1366-588X. ; 42:17, s. 3603-3617
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Tidskriftsartikel (refereegranskat)abstract
- A model to deal with the disassembly processes in remanufacturing systems is presented with focus being on evaluating their economic consequences. More specifically, the model assists decisions such as to which degree and for the sake of which components should the returned items be disassembled. Consequently, using the economic values of recoverable items, the inventory holding costs of these items are obtained. This information is further used to determine the inventory control policy. To access such economic values, the above average cost approach is compared with the net present value method. The latter is often considered a more 'correct' way in remanufacturing systems from the viewpoint of inventory control. The results from the economic evaluation model are intended to aid companies in systematically evaluating current as well as projected remanufacturing systems.
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| 12. |
- Tang, Ou
(författare)
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Modelling stochastic lead times in a production-inventory system based on the Laplace transform method
- 2000
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Ingår i: International Journal of Production Research. - 0020-7543 .- 1366-588X. ; 38:17, s. 4217-4226
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Tidskriftsartikel (refereegranskat)abstract
- Stochastic properties of a multi-period production-inventory system have been studied in several papers by applying the Laplace transform. However, the source of uncertainty has been limited to external demand and the production/replenishment lead time has been assumed to be constant. In this paper, we investigate the situation when the lead time is a random variable. Transform methods are again used to capture the stochastic properties of the system, such as stockout functions. With the objective of maximizing the net present value of the cash flow, we derive conditions for optimal production decisions in this system. The properties of cash outflow due to stockouts will also be discussed.
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| 13. |
- Tang, Ou, et al.
(författare)
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The impact of information transparency on the dynamic behaviour of a hybrid manufacturing/remanufacturing system
- 2004
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Ingår i: International Journal of Production Research. - : Informa UK Limited. - 0020-7543 .- 1366-588X. ; 42:19, s. 4135-4152
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Tidskriftsartikel (refereegranskat)abstract
- A combined manufacturing/remanufacturing system is modelled and its dynamic behaviour is investigated using a control engineering approach. The model is an extension of the automated pipeline, inventory and order based production control system (APIOBPCS), which is well understood from a dynamic perspective. It is assumed that the remanufacturing process is based on a PUSH policy. Utilising different levels of information transparency from the remanufacturing process, three system types are developed and compared. Mathematical and simulation analyses of the system types were undertaken and their robustness to remanufacturing process uncertainties were tested. Our analysis indicates that the greater the degree of information transparency, the greater the robustness of the hybrid system.
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| 14. |
- Wikner, Joakim
(författare)
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Continuous-time dynamic modelling of variable lead times
- 2003
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Ingår i: International Journal of Production Research. - : Informa UK Limited. - 0020-7543 .- 1366-588X. ; 41:12, s. 2787-2798
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Tidskriftsartikel (refereegranskat)abstract
- Dynamic modelling of production-inventory systems usually involves lead time models since this is one of the most important aspects of these systems. Many different models are possible and this paper presents an overview and some ideas for how the models may be interpreted. Three different approaches to continuous-time dynamic modelling of variable lead times based on Control Theory are discussed. Two of the models can easily be incorporated into linear models based on the Laplace transform. The models are shown to be three instances of a generic delay model, which by careful selection of two parameters can be adapted to a wide variety of systems. Also the relation between waiting line theory concepts and the generic delay model is analysed, establishing an interpretation of the models as generating the concept of expected dynamic behaviour.
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| 15. |
- Wiktorsson, Magnus, 1971-, et al.
(författare)
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A note on the specification of assembly systems
- 2000
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Ingår i: International Journal of Production Research. - : Taylor & Francis. - 0020-7543 .- 1366-588X. ; 38:16, s. 3997-4002
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Tidskriftsartikel (refereegranskat)abstract
- Although the characteristics and cost of any technical system are highly influenced by the early design phases, little focus has been on the structure and use of the specification in manufacturing system design, in this paper exemplified by assembly systems for large, high-volume products. This paper proposes a framework for elaborating such specifications. The framework is based on a division in qualifying and winning criteria, and is structured into four classes: functional requirements; internal design constraints; external design constraints; and winning criteria. Defining the specification by these terms is justified and explained by comparing standard mathematical formulation for this kind of problem to the framework. Future research efforts are pointed out where the framework is used throughout the development project for goal-focus, as the specification is used and refined in an iterative manner.
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| 16. |
- Zanoni, Simone, et al.
(författare)
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A note on an industrial strategy for stock management in supply chains : modelling and performance evaluation
- 2004
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Ingår i: International Journal of Production Research. - : Informa UK Limited. - 0020-7543 .- 1366-588X. ; 42:20, s. 4421-4426
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Tidskriftsartikel (refereegranskat)abstract
- An analytic formulation of consignment stock (CS) policy has been proposed in Braglia and Zavanella (2003, International Journal of Production Research 41, 3793) where an implicit analytical solution is given. In this note it is shown that this solution has properties that enable it to be developed intoa completely explicit form, allowing for a joint optimization of all decision variables governing the delivery management.
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