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Papers by Christian Hicks

Research paper thumbnail of Dynamic production scheduling and rescheduling for complex assemblies

Research paper thumbnail of Job release-time design for capital products with uncertain processing times and resource constrains

Research paper thumbnail of An ordinal optimization based evolution strategy to schedule complex make-to-order products

International Journal of Production Research, 2006

ABSTRACT This paper considers the problem of planning and scheduling a complex make-to-order prod... more ABSTRACT This paper considers the problem of planning and scheduling a complex make-to-order product with multiple levels of product structure. The work assumes finite capacity constraints and uncertain processing times. For planning such systems we define a schedule as a set of planned operation start times together with a set of priority rules (for individual resources) that are followed in implementing the schedule. An optimal schedule is determined by minimizing the expected total cost (the sum of work in progress holding costs, product earliness costs and product tardiness costs). A Stochastic Discrete-Event Based Evolution Strategy (SDEES) is first introduced to tackle the scheduling problem. However, SDEES is computationally demanding due to the multiplicative effect of the number of search iterations and the size of the evaluation samples required at each stage in the search. To reduce computation and improve search speed, an Ordinal Optimization Based Evolution Strategy (OOES) is developed. Quantitative examples covering a range of uncertainty levels are used to illustrate the effectiveness of the methods. Further, a case study using data from a collaborating company demonstrates the practical effectiveness. The Ordinal Optimization Evolutionary Strategy achieves a performance similar to the SDEES whilst reducing the computational time by around 60%.

Research paper thumbnail of Dynamic scheduling for complex engineer-to-order products

International Journal of Production Research, 2007

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Research paper thumbnail of Setting planned job release times in stochastic assembly systems with resource constraints

International Journal of Production Research, 2001

This paper considers a stochastic assembly system operating on a make-to-order basis with complex... more This paper considers a stochastic assembly system operating on a make-to-order basis with complex product structure and resource constraints. The problem is to ® nd the optimal planned job release times by minimizing the expected sum of the work-in-progress holding cost, product earliness cost and product tardiness cost. A perturbation analysis algorithm is developed to derive the gradient estimate of the cost function with respect to the job release times. This gradient estimate is shown to be unbiased and may lead to the optimal solution by using a stochastic approximation method. Moreover, a procedure is presented to adjust planned job release times to meet service level constraint for each individual job. Numerical examples, which use manufacturing and assembly data from a capital goods company, are given to demonstrate the results.

Research paper thumbnail of Stage due date planning for multistage assembly systems

International Journal of Production Research, 2001

Coordinating due dates of operations throughout all stages of manufacturing and assembly is a pro... more Coordinating due dates of operations throughout all stages of manufacturing and assembly is a problem especially for complex product structures with uncertainties in process times. A recursive procedure is described to estimate distributions of completion times for each operation. Stage due dates are then calculated to meet speci® ed service targets. Compared with plans from existing heuristic methods, there are considerable improvements in meeting service targets and reducing costs. Simulations demonstrate that the method is eOE ective for complex assemblies produced in low volumes by capital goods companies. Revision

Research paper thumbnail of Product due date assignment for complex assemblies

International Journal of Production Economics, 2002

A method is described to assign product due dates for multistage assemblies with uncertain manufa... more A method is described to assign product due dates for multistage assemblies with uncertain manufacturing and assembly process times. Earliest start times of operations are specified by a predetermined production plan and processing time distributions for operations are truncated at minimum processing times. The method systematically decomposes the complex product structures of multistage assemblies into two-stage subsystems. Both exact and approximate distributions of completion time for two-stage assemblies are developed. The latter is applied recursively to multistage assemblies to yield an approximate distribution of product completion time. Product due dates are assigned to either minimise earliness and tardiness costs or to meet a service target. This method is applied to examples which use manufacturing and assembly data from a capital goods company. The results are verified by simulation.

Research paper thumbnail of The development of genetic algorithms for the finite capacity scheduling of complex products, with multiple levels of product structure

European Journal of Operational Research, 2004

In this paper, the development of a genetic algorithms based scheduling tool that takes into acco... more In this paper, the development of a genetic algorithms based scheduling tool that takes into account multiple resource constraints and multiple levels of product structure is described. The genetic algorithms includes a repair process that rectifies infeasible chromosomes that may be produced during evolution process. The algorithm includes problem encoding, chromosome representation and initialisation, genetic operation, repair process, fitness measurement and chromosome selection. The data structure and algorithm are detailed step by step. The tool generates schedules that minimises the penalties caused by early and late delivery of for components, assemblies and final products. The method is applied using data obtained from a collaborating company that manufactures complex capital goods. It is demonstrated that the schedules produced perform significantly better than those produced by the company using a conventional planning method.

Research paper thumbnail of Dispatching rules for production scheduling in the capital goods industry

International Journal of Production Economics, 2006

Research on dispatching rules has focused upon deterministic job shop situations or small assembl... more Research on dispatching rules has focused upon deterministic job shop situations or small assembly environments and ignored operational factors. This work uses data obtained from a capital goods company that produces complex products. The paper first explores the influence of the data update period and the minimum setup, machining and transfer times under stochastic infinite capacity conditions. It then investigates the significance of these factors and the relative performance of eight dispatching rules with finite capacity and stochastic processing times. Dispatching rules and most operational parameters were statistically significant. With finite capacity, the 'best' dispatching rule was different at the component and product levels and varied according to the performance measure used. The shortest operation time first rule generally produced the best results, particularly at product level.

Research paper thumbnail of Planning Complex Engineer-To-Order Products

Recent Advances in Integrated Design and Manufacturing in Mechanical Engineering, 2003

The design and manufacture of complex Engineer-to-Order products is characterised by uncertain op... more The design and manufacture of complex Engineer-to-Order products is characterised by uncertain operation durations, finite capacity resources and multilevel product structures. Two scheduling methods are presented to minimise expected costs for multiple products across multiple finite capacity resources. The first sub-optimises the operations sequence, using mean operation durations, then refines the schedule by perturbation. The second method generates a schedule of start times directly by random search with an embedded simulation of candidate schedules for evaluation. The methods are compared for industrial examples.

Research paper thumbnail of Solving Multi-stage, Multi-machine, Multi-product Scheduling Problems

Abstract. Companies that produce capital goods need to schedule the production of products that h... more Abstract. Companies that produce capital goods need to schedule the production of products that have complex product structures with components that require many operations on different machines. A feasible schedule must satisfy operation and assembly precedence constraints. It is also important to avoid deadlock situations. In this paper a Genetic Algorithm (GA) has been developed that includes a new repair process that rectifies infeasi-ble schedules that are produced during the evolution process. The algorithm was designed to minimise the com-bination of earliness and tardiness penalties and took into account finite capacity constraints. Three different sized problems were obtained from a collaborating capital goods company. A design of experimental approach was used to systematically identify that the best genetic operators and GA parameters for each size of problem.

Research paper thumbnail of The development of a hierarchical forecasting method for predicting spare parts demand in the South Korean navy – a case study

In the South Korean Navy the demand for many spare parts is infrequent and the volume of items re... more In the South Korean Navy the demand for many spare parts is infrequent and the volume of items required is irregular. This pattern, known as non-normal demand, makes forecasting difficult. This paper uses data obtained from the South Korean Navy to compare the performance of various forecasting methods that use hierarchical and direct forecasting strategies for predicting the demand for spare parts. A simple combination of exponential smoothing models was found to minimise forecasting errors. A simulation experiment verified that this approach also minimised inventory costs.

Research paper thumbnail of A simulation model of hierarchical production control systems in make-to-order manufacturing

Research paper thumbnail of Planning design and manufacture in complex engineer-to-order products

Research paper thumbnail of A Multiple Criteria Genetic Algorithm Scheduling Tool for Production Scheduling in the Capital Goods Industry

International Journal of Engineering and Technology Innovation, 2014

Production planners usually aim to satisfy multiple objectives. This paper describes the developm... more Production planners usually aim to satisfy multiple objectives. This paper describes the development of a genetic algorithm tool that finds optimum trade-offs among delivery performance, resource utilisation, and workin-progress inventory. The tool was specifically developed to meet the requirements of capital goods companies that manufacture products with deep and complex product structures with components that have long and complicated routings. The model takes into account operation and assembly precedence relationships and finite capacity constraints. The tool was tested using various production problems that were obtained from a collaborating company. A series of experiments showed the tool provides a set of non-dominated solutions that enable the planner to choose an optimum trade-off according to their preferences. Previous research had optimised a single objective function. This is the first scheduling tool of its type that has simultaneously optimised delivery performance, ...

Research paper thumbnail of Stategic issues in make-to-order manufacturing

Research paper thumbnail of Using Genetic Algorithms for scheduling the production of capital goods

Research paper thumbnail of A tool for generating optimum facilities layouts under demand uncertainty with/without machine breakdown

Manufacturing systems are subject to many uncertainties including variability in demand and machi... more Manufacturing systems are subject to many uncertainties including variability in demand and machine breakdown. The layout of manufacturing facilities has a large impact on lead-times, inventory, costs and delivery performance. The distance travelled by materials is a commonly used proxy for the efficiency of layouts. It is common for planners to avoid production interruptions by adopting alternative routings if machines are unavailable due to breakdown or maintenance. Demand uncertainty and rerouting both have an impact on material flow. The objective of layout design is to produce a block plan that shows the relative positioning of resources. A block plan can then be translated into a detailed layout drawing. The facility layout problem is an NP complete combinatorial optimisation problem, which means that the time taken to solve problems using enumerative search increases exponentially with problem size. This paper presents the development of the Genetic Algorithm (GA) based layou...

Research paper thumbnail of Using a Genetic Algorithm layout design tool to optimise facility layout designs in the capital goods industry

Research paper thumbnail of An analysis of knowledge management activities in the provision of customised goods

Research paper thumbnail of Dynamic production scheduling and rescheduling for complex assemblies

Research paper thumbnail of Job release-time design for capital products with uncertain processing times and resource constrains

Research paper thumbnail of An ordinal optimization based evolution strategy to schedule complex make-to-order products

International Journal of Production Research, 2006

ABSTRACT This paper considers the problem of planning and scheduling a complex make-to-order prod... more ABSTRACT This paper considers the problem of planning and scheduling a complex make-to-order product with multiple levels of product structure. The work assumes finite capacity constraints and uncertain processing times. For planning such systems we define a schedule as a set of planned operation start times together with a set of priority rules (for individual resources) that are followed in implementing the schedule. An optimal schedule is determined by minimizing the expected total cost (the sum of work in progress holding costs, product earliness costs and product tardiness costs). A Stochastic Discrete-Event Based Evolution Strategy (SDEES) is first introduced to tackle the scheduling problem. However, SDEES is computationally demanding due to the multiplicative effect of the number of search iterations and the size of the evaluation samples required at each stage in the search. To reduce computation and improve search speed, an Ordinal Optimization Based Evolution Strategy (OOES) is developed. Quantitative examples covering a range of uncertainty levels are used to illustrate the effectiveness of the methods. Further, a case study using data from a collaborating company demonstrates the practical effectiveness. The Ordinal Optimization Evolutionary Strategy achieves a performance similar to the SDEES whilst reducing the computational time by around 60%.

Research paper thumbnail of Dynamic scheduling for complex engineer-to-order products

International Journal of Production Research, 2007

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Research paper thumbnail of Setting planned job release times in stochastic assembly systems with resource constraints

International Journal of Production Research, 2001

This paper considers a stochastic assembly system operating on a make-to-order basis with complex... more This paper considers a stochastic assembly system operating on a make-to-order basis with complex product structure and resource constraints. The problem is to ® nd the optimal planned job release times by minimizing the expected sum of the work-in-progress holding cost, product earliness cost and product tardiness cost. A perturbation analysis algorithm is developed to derive the gradient estimate of the cost function with respect to the job release times. This gradient estimate is shown to be unbiased and may lead to the optimal solution by using a stochastic approximation method. Moreover, a procedure is presented to adjust planned job release times to meet service level constraint for each individual job. Numerical examples, which use manufacturing and assembly data from a capital goods company, are given to demonstrate the results.

Research paper thumbnail of Stage due date planning for multistage assembly systems

International Journal of Production Research, 2001

Coordinating due dates of operations throughout all stages of manufacturing and assembly is a pro... more Coordinating due dates of operations throughout all stages of manufacturing and assembly is a problem especially for complex product structures with uncertainties in process times. A recursive procedure is described to estimate distributions of completion times for each operation. Stage due dates are then calculated to meet speci® ed service targets. Compared with plans from existing heuristic methods, there are considerable improvements in meeting service targets and reducing costs. Simulations demonstrate that the method is eOE ective for complex assemblies produced in low volumes by capital goods companies. Revision

Research paper thumbnail of Product due date assignment for complex assemblies

International Journal of Production Economics, 2002

A method is described to assign product due dates for multistage assemblies with uncertain manufa... more A method is described to assign product due dates for multistage assemblies with uncertain manufacturing and assembly process times. Earliest start times of operations are specified by a predetermined production plan and processing time distributions for operations are truncated at minimum processing times. The method systematically decomposes the complex product structures of multistage assemblies into two-stage subsystems. Both exact and approximate distributions of completion time for two-stage assemblies are developed. The latter is applied recursively to multistage assemblies to yield an approximate distribution of product completion time. Product due dates are assigned to either minimise earliness and tardiness costs or to meet a service target. This method is applied to examples which use manufacturing and assembly data from a capital goods company. The results are verified by simulation.

Research paper thumbnail of The development of genetic algorithms for the finite capacity scheduling of complex products, with multiple levels of product structure

European Journal of Operational Research, 2004

In this paper, the development of a genetic algorithms based scheduling tool that takes into acco... more In this paper, the development of a genetic algorithms based scheduling tool that takes into account multiple resource constraints and multiple levels of product structure is described. The genetic algorithms includes a repair process that rectifies infeasible chromosomes that may be produced during evolution process. The algorithm includes problem encoding, chromosome representation and initialisation, genetic operation, repair process, fitness measurement and chromosome selection. The data structure and algorithm are detailed step by step. The tool generates schedules that minimises the penalties caused by early and late delivery of for components, assemblies and final products. The method is applied using data obtained from a collaborating company that manufactures complex capital goods. It is demonstrated that the schedules produced perform significantly better than those produced by the company using a conventional planning method.

Research paper thumbnail of Dispatching rules for production scheduling in the capital goods industry

International Journal of Production Economics, 2006

Research on dispatching rules has focused upon deterministic job shop situations or small assembl... more Research on dispatching rules has focused upon deterministic job shop situations or small assembly environments and ignored operational factors. This work uses data obtained from a capital goods company that produces complex products. The paper first explores the influence of the data update period and the minimum setup, machining and transfer times under stochastic infinite capacity conditions. It then investigates the significance of these factors and the relative performance of eight dispatching rules with finite capacity and stochastic processing times. Dispatching rules and most operational parameters were statistically significant. With finite capacity, the 'best' dispatching rule was different at the component and product levels and varied according to the performance measure used. The shortest operation time first rule generally produced the best results, particularly at product level.

Research paper thumbnail of Planning Complex Engineer-To-Order Products

Recent Advances in Integrated Design and Manufacturing in Mechanical Engineering, 2003

The design and manufacture of complex Engineer-to-Order products is characterised by uncertain op... more The design and manufacture of complex Engineer-to-Order products is characterised by uncertain operation durations, finite capacity resources and multilevel product structures. Two scheduling methods are presented to minimise expected costs for multiple products across multiple finite capacity resources. The first sub-optimises the operations sequence, using mean operation durations, then refines the schedule by perturbation. The second method generates a schedule of start times directly by random search with an embedded simulation of candidate schedules for evaluation. The methods are compared for industrial examples.

Research paper thumbnail of Solving Multi-stage, Multi-machine, Multi-product Scheduling Problems

Abstract. Companies that produce capital goods need to schedule the production of products that h... more Abstract. Companies that produce capital goods need to schedule the production of products that have complex product structures with components that require many operations on different machines. A feasible schedule must satisfy operation and assembly precedence constraints. It is also important to avoid deadlock situations. In this paper a Genetic Algorithm (GA) has been developed that includes a new repair process that rectifies infeasi-ble schedules that are produced during the evolution process. The algorithm was designed to minimise the com-bination of earliness and tardiness penalties and took into account finite capacity constraints. Three different sized problems were obtained from a collaborating capital goods company. A design of experimental approach was used to systematically identify that the best genetic operators and GA parameters for each size of problem.

Research paper thumbnail of The development of a hierarchical forecasting method for predicting spare parts demand in the South Korean navy – a case study

In the South Korean Navy the demand for many spare parts is infrequent and the volume of items re... more In the South Korean Navy the demand for many spare parts is infrequent and the volume of items required is irregular. This pattern, known as non-normal demand, makes forecasting difficult. This paper uses data obtained from the South Korean Navy to compare the performance of various forecasting methods that use hierarchical and direct forecasting strategies for predicting the demand for spare parts. A simple combination of exponential smoothing models was found to minimise forecasting errors. A simulation experiment verified that this approach also minimised inventory costs.

Research paper thumbnail of A simulation model of hierarchical production control systems in make-to-order manufacturing

Research paper thumbnail of Planning design and manufacture in complex engineer-to-order products

Research paper thumbnail of A Multiple Criteria Genetic Algorithm Scheduling Tool for Production Scheduling in the Capital Goods Industry

International Journal of Engineering and Technology Innovation, 2014

Production planners usually aim to satisfy multiple objectives. This paper describes the developm... more Production planners usually aim to satisfy multiple objectives. This paper describes the development of a genetic algorithm tool that finds optimum trade-offs among delivery performance, resource utilisation, and workin-progress inventory. The tool was specifically developed to meet the requirements of capital goods companies that manufacture products with deep and complex product structures with components that have long and complicated routings. The model takes into account operation and assembly precedence relationships and finite capacity constraints. The tool was tested using various production problems that were obtained from a collaborating company. A series of experiments showed the tool provides a set of non-dominated solutions that enable the planner to choose an optimum trade-off according to their preferences. Previous research had optimised a single objective function. This is the first scheduling tool of its type that has simultaneously optimised delivery performance, ...

Research paper thumbnail of Stategic issues in make-to-order manufacturing

Research paper thumbnail of Using Genetic Algorithms for scheduling the production of capital goods

Research paper thumbnail of A tool for generating optimum facilities layouts under demand uncertainty with/without machine breakdown

Manufacturing systems are subject to many uncertainties including variability in demand and machi... more Manufacturing systems are subject to many uncertainties including variability in demand and machine breakdown. The layout of manufacturing facilities has a large impact on lead-times, inventory, costs and delivery performance. The distance travelled by materials is a commonly used proxy for the efficiency of layouts. It is common for planners to avoid production interruptions by adopting alternative routings if machines are unavailable due to breakdown or maintenance. Demand uncertainty and rerouting both have an impact on material flow. The objective of layout design is to produce a block plan that shows the relative positioning of resources. A block plan can then be translated into a detailed layout drawing. The facility layout problem is an NP complete combinatorial optimisation problem, which means that the time taken to solve problems using enumerative search increases exponentially with problem size. This paper presents the development of the Genetic Algorithm (GA) based layou...

Research paper thumbnail of Using a Genetic Algorithm layout design tool to optimise facility layout designs in the capital goods industry

Research paper thumbnail of An analysis of knowledge management activities in the provision of customised goods

Research paper thumbnail of Leadership and transformational change in healthcare organisations: A qualitative analysis of the North East Transformation System

Health Services Management Research, 2013

The research project &amp... more The research project 'An Evaluation of Transformational Change in NHS North East' examines the progress and success of National Health Service (NHS) organisations in north east England in implementing and embedding the North East Transformation System (NETS), a region-wide programme to improve healthcare quality and safety, and to reduce waste, using a combination of Vision, Compact, and Lean-based Method. This paper concentrates on findings concerning the role of leadership in enabling tranformational change, based on semi-structured interviews with a mix of senior NHS managers and quality improvement staff in 14 study sites. Most interviewees felt that implementing the NETS requires committed, stable leadership, attention to team-building across disciplines and leadership development at many levels. We conclude that without senior leader commitment to continuous improvement over a long time scale and serious efforts to distribute leadership tasks to all levels, healthcare organisations are less likely to achieve positive changes in managerial-clinical relations, sustainable improvements to organisational culture and, ultimately, the region-wide step change in quality, safety and efficiency that the NETS was designed to deliver.