Joint production and maintenance planning with machine deterioration and random yield

Production, yield and maintenance are three key components for sustaining the competitiveness of a manufacturing firm. In this paper, we investigate a joint production and maintenance planning problem in a periodic review environment subject to stochastic demand and random yields. The manufacturing system deteriorates from period to period according to a discrete-time Markov chain. The objective is to find an integrated lot sizing and maintenance policy for the system such that the aggregate cost associated with production, holding, backlogging and maintenance is minimised. We formulate this integrated planning problem as a Markov decision process and analyse the structural properties of the optimal policies. We prove that the optimal production and the maintenance policies both exhibit a control limit structure and show that the solution to the finite-horizon problems converges to that of the infinite-horizon problem.     

Integrating occupational health and safety in facility layout planning,part I: methodology

An influential factor affecting the efficiency of a manufacturing facility is its layout. In a production facility, measure for efficiency can be based on the total cost of transporting the items between different departments and throughout the facility. However, other factors may influence efficiency of the manufacturing facility too. As such are: supporting the organisation's vision through improved material handling, material flow and control; effectively assigning people, equipment, space and energy; minimising capital investment; adaptability and ease of maintenance; as well as providing for employee safety and job satisfaction. By incorporating health and safety measures in the initial design of a facility layout, the organisation may avoid money and manpower loss resulting from industrial accidents. This paper proposes a facility layout planning methodology which integrates the occupational health and safety (OHS) features in the early design of a facility layout. The model considers transportation cost in the facility as well as safety concerns. By this means, the OHS issues are reflected prior to the construction of a facility.     

Selection of management accounting systems in Just-In-Time and Theory of Constraints-based manufacturing

In today's competitive business environments, a firm's long-term survival rests heavily on its ability to sustain manufacturing superiority over its competitors. To provide the firm with detailed guidelines for sustaining manufacturing superiority, this paper examines the impact of different management accounting systems, manufacturing control systems and time horizon on manufacturing performance in an enterprise resource planning integrated environment. These management accounting systems include traditional costing, activity-based costing and throughput accounting. The manufacturing control systems include Just-In-Time- and Theory of Constraints-based manufacturing. Through a series of simulation experiments, it was found that activity-based costing provided higher short- and long-term profit, better customer service and lower work-in-process inventory than traditional costing and throughput accounting in situations where firms have high overhead costs and relatively low labour and material costs, while carrying ending inventories because of demand uncertainty. Traditional costing also outperformed throughput accounting by exploiting the real-time information sharing capabilities of an enterprise resource planning system. Just-In-Time manufacturing outperformed Theory of Constraints with respect to short- and long-term profitability, customer service, and work-in-process inventory because of differences in buffer inventory policies and sequencing rules. However, time horizon and its interaction with management accounting systems had no impact on the manufacturing performance. In addition, the results suggest that a management accounting system that depicts the manufacturing process tended to provide more accurate product cost information and resulted in a better system performance than the others.     

Combined parameter and tolerance design optimization with quality and cost

The need to remain competitive for survival in the current world market has led manufacturing sectors to consider the low cost and high quality of product and process design. Production of quality products at low cost in today's manufacturing industry requires simultaneous consideration of product design and process planning, particularly in the early stage of design and planning. During product design, parameter design determines the design target (design setting) and tolerance design determines design tolerance. During process design, the parameter design determines the process mean (process setting) and tolerance design determines process tolerance. This study provides a mathematical relationship to link the elements of design target, design tolerance, process mean and process tolerance in one equation. By following this equation, manufacturability for all possible combinations of product and process design can be ensured, which increases the flexibility of both product design and process planning. With this in mind, an analysis model that includes manufacturing cost and quality loss simultaneously has been developed to determine the optimal values of design tolerance, process mean and process tolerance. The proposed model provides a method of combining the optimization of parameter and tolerance design over product/process in the early stage of design.     

Linking Project Team Performance with Team Health

Abstract

The effectiveness of using teams to improve an organization's performance has been well documented in both the public and private sectors. Typically, however, an assessment of how well a team is functioning is based solely upon external quantitative measures such as the number of customers served, the number of defective units produced, and other cost, schedule, and performance numbers. While these traditional measures are important to management's assessment of a team's performance, they do not give a complete picture of the team's overall long-term performance potential. In this article, the internal “team health” of a team is defined and postulated to have an impact on the team's long-term performance. Current research is documented that seeks to determine if a positive relationship exists between a team's health and its performance.     

Master production scheduling make-to-stock products: a framework for analysis

Excessive changes in MRP system schedules, commonly referred to as 'nervousness’, is frequently an obstacle in implementing an effective MRP based manufacturing planning and control system. This paper is concerned with the design of methods for freezing the master production schedule (MPS) as a way of controlling MPS stability under rolling planning conditions for make-to-stock products. It presents a framework for the design of MPS freezing methods and compares their performance when the design parameters of these methods are varied. Simulation experiments are reported that demonstrate important differences in performance considering criteria involving both the cost of lot-sizing the MPS and the stability of the master production schedule.     

Structural and infrastructural practices as elements of content operations strategy. The effect on a firm's competitiveness

Some extant theoretical studies and different empirical results have demonstrated that a firm's behaviour explains several notable competitiveness microeconomic foundations, based on a wide bundle of elements. Firms can directly control most of these elements; in this paper, we will focus on those related to operations management. Therefore, products, processes, technology, equipments or quality control systems will centre our attention. These, and some additional elements, constitute decisions within the operations management area that must be included in the content of operations strategy. Operations strategy can be conceptualized as a set of decisions or practices with regard to structure and infrastructure variables. On the one hand, these strategic decisions influence a firm's abilities successfully to reach some competitive priorities such as cost, quality, delivery and flexibility, and, on the other hand, to obtain the expected performance. This research analyzes which are the main structural and infrastructural practices that constitute operations strategies in manufacturing companies, and investigates the effect of these decisions on some firm competitiveness indicators.     

Optimal process parameter determination for computer‐aided manufacturing

Producing high‐quality products at low cost is one of the key factors to survival for manufacturing sectors in today's intense global competition environment. One way to gain competitiveness is to integrate product design and process planning into one activity. This study attempts to determine optimal process parameters for a manufacturing process under given design parameters. The process parameters to be determined in this study include process means and process tolerances for particular manufacturing process sequences. The problem is formulated in constrained non‐linear optimization, considering both quality‐ and manufacturing‐related costs. The proposed application evaluates alternative product designs and process sequences so that the best associated process parameters can be determined during the early stages of design and planning. This makes the link between CAD and CAM systems more useful and effective. As a result, optimal integration of product design and process planning with minimal production costs and maximal product quality is possible. Copyright © 1999 John Wiley & Sons, Ltd.     

Production planning system for a combination of make-to-stock and make-to-order products

This paper deals with the problem of designing a production planning system for a combination of make-to-stock (MTS) and make-to-order (MTO) products where the production facility produces both types of products. Important management points in such production systems are to design an efficient production planning system which can shorten the manufacturing time of MTO products as well controlling the unfilled rate of MTS products to the market demand at a low level. A hierarchical production planning model is introduced in order to design the production planning system. The buffer capacity is set as a design variable for determining production capacity at a higher planning level, and the rule for allocating the production capacity to types of products is adopted as a design variable at a lower level. First, we analyse how these two design variables affect the unfilled rate of MTS products and the average manufacturing time of MTO products. Second, we clarify the relationship of the buffer capacity with the manufacturing time of MTO products and with the required buffer inventory level of MTS products which can maintain the unfilled rate of MTS products to the market demand within an acceptable limit. Third, we show an example of the range of design variables which can control the unfilled rate of MTS products and the manufacturing time of MTO products within their acceptable limits, if the individual limits of the performance measure is given to respond to customer orders quickly.     

Bivariate tolerance design for lock wheels by considering quality loss

In the design of tolerance allocation the cost–tolerance function is usually employed to represent the objective function which is to be minimized. The traditional cost–tolerance functions in the literature are concerned with only one characteristic. In this paper we obtain a bivariate cost–tolerance function to describe the relationship between the cost and tolerances of two characteristics (i.e. the thickness and inner diameter) of a lock wheel. Then the bivariate loss function is combined with the bivariate cost–tolerance function to determine the optimal tolerances for the thickness and inner diameter of a lock wheel such that the user's potential loss/cost may be evaluated. When the quality loss is considered, the tolerances of both characteristics become tighter. By including the effect of product degradation, the present work of expected bivariate quality loss is then introduced as a quality performance measure. By assuming linear drifts on both the thickness and inner diameter of the lock wheels, the model with the present worth of quality loss leads to tighter tolerances of both characteristics. In addition, a longer planning horizon (or a longer useful life of the product) leads to tighter tolerances and a larger user's discount rate results in looser tolerances for both characteristics. Copyright © 2000 John Wiley & Sons, Ltd.     

Facility layout optimization using simulation and genetic algorithms

Traditionally, the objective of a facility layout problem has been to minimize the material handling cost of the manufacturing system. While it is important to reduce the amount of material handling, the traditional methods do not address the actual time at which the material is transported. In today's short cycle time production environments, the timing of material movement may have a bigger impact on the productivity of the system than its cost. In this paper, a facility layout optimization technique is presented that takes into consideration the dynamic characteristics and operational constraints of the system as a whole, and is able to solve the facility layout design problem based on a system's performance measures, such as the cycle time and productivity. Each layout solution is presented in the form of a string that is suitable for analysis by a genetic algorithm technique. These solutions are then translated into simulation models by a specially designed automated simulation model generator. Genetic algorithms are used to optimize the layout for manufacturing effectiveness while simulation serves as a system performance evaluation tool. Combined with a statistical comparison technique to reduce the simulation burden, the test results demonstrate that the proposed approach overcomes the limitations of traditional layout optimization methods and is capable of finding optimal or near optimal solutions.     

Product flexibility in selecting manufacturing planning and control strategy

The manufacturing systems capable of producing several products simultaneously are frequently subject to changes in product types due to demand fluctuations. In such systems a product flexible manufacturing planning and control (MPC) strategy is needed to change from one product type to another with minimum deterioration to system performance levels. The objective of this research is to develop a systematic analysis and evaluation approach in order to compare the MRP-push and JIT-pull strategies quantitatively based on a product flexibility measure. A new product flexibility measure is developed based on the sensitivity to change concept and presented together with the implementation in a real manufacturing system. Simulation is used to compare the performance of a JIT-pull with an MRP-push strategy based on performance measures, e.g. manufacturing lead time, work-in-process inventory, backorders, machine utilization and throughput. The performances of the two strategies are evaluated in two scenarios: (i) a single product; (ii) a second product is added (the first product being simple and the second being complex in terms of processing). The impacts of adding the second product on the performance measures for the push and pull strategies are then assessed. A multi-attribute evaluation scheme is used to compare the two strategies where the attribute values are the change in performance measures as the second product is added. The proposed product flexibility measure is utilized in the interpretation of the results.     

Integration of occupational health and safety in the facility layout planning,part II: design of the kitchen of a hospital

Facility layout design has an important effect on the performance of manufacturing systems. It intends to determine relative location of departments and machines within a plant. A good layout design must ensure that a set of criteria and objectives are met and optimised, e.g. area requirements, cost, communication and safety. The most common objective used in facility planning methods is to minimise the transportation cost. However, factors such as the plant safety, flexibility for future design changes, noise and aesthetics must be considered as well. In this paper, a case study is carried out to investigate the safety concerns in facility layout design. In this regard, a facility layout planning methodology, integrating occupational health and safety (OHS) is presented. This methodology considers transportation cost as well as safety in the facility design. By this means, OHS issues are considered at the design stage of the facility. In other words, this research demonstrates the improvements in the layout design by integrating safety aspects.     

Product and employee development in advanced manufacturing: Implementation and impact

As competitive intensity increases and the need for rapid, responsive and efficient production rises, manufacturers need to develop effective strategies that lever all a firm's resources into a competitive weapon. One challenge managers face in today's dynamic global economy is to choose appropriate manufacturing practices and then to integrate them into a cohesive value-added strategy that will yield enhanced competitive performance. The sheer number and range of manufacturing 'strategies' that have emerged over the past 20 years exacerbate the challenge. The goal of this study is therefore to look at four highly publicized manufacturing strategies and then examine their interrelationships and impact on firm performance: (1) integrated product development, (2) employee development, (3) just-in-time manufacturing and (4) manufacturing automation. The responses of 158 managers from randomly selected US manufacturing firms were used to develop a covariance matrix to facilitate the use of a structural equations model via LISREL. The analysis indicates that employee and product development strategies are important antecedents of just-in-time and automation strategies. All four advanced manufacturing practices have significant, positive impacts on organizational competitiveness.     

Designing a collaborative supply-chain plan using the analytic hierarchy process and genetic algorithm with cycle-time estimation

Collaboration management has become a key issue for supply-chain management and can improve the overall production/manufacturing performance and value. This paper aims to conduct collaborative supply-chain planning and establish supplier selection, as well as production and distribution planning. This study uses an Analytic Hierarchy Process with Rough Sets Theory to establish a supplier purchasing value rating system. Also, a cycle-time estimation procedure is developed to effectively estimate the operating time of a collaborative supply chain. Assembly-line balancing technology is also introduced to guarantee smooth production and distribution in a supply chain. A multi-objective optimisation mathematical model, including purchasing value, cost, cycle time, and smoothness index, is constructed to complete the supplier selection and production-distribution planning. To efficiently solve this mathematical model, this paper proposes a genetic algorithm (E_ctGA) combined with a cycle-time estimation procedure. Finally, it presents a case study for validation. The results show that a better collaborative supply chain plan could be achieved by combining the proposed cycle-time estimation procedure.     

Anarchic manufacturing

This paper introduces anarchic manufacturing, an extremely distributed planning and control philosophy, as the methodology for planning and controlling future smart factories. Anarchic manufacturing delegates decision-making authority and autonomy to the lowest level of entities in system elements with no centralised control or oversight. It is often postulated that traditional hierarchical structures may not be well suited to manage the state-of-the-art hyper-connected smart factories due to their reliance on communication between management layers. Distributed systems, on the other hand, are commonly perceived to be inherently more flexible, robust and adaptable than hierarchical systems due to their structure. This paper characterises distributed systems by evaluating the relative flexibility of a representative hierarchical system against an anarchic system in a job shop scenario. Multi-agent-based simulation is used to model both hierarchical and anarchic systems, which are tested for flexibility following the Taguchi method and compared against Taillard's benchmark job shop problems for overall performance. The results show that the anarchic system performs as well as the hierarchical system when subjected to unforeseen disruption, refuting the argument that hierarchical systems are too rigid and distributed systems are inherently more flexible. However, anarchic manufacturing systems, which show adaptability and self-optimising traits, provide a platform to potentially enable the emerging digital manufacturing paradigm through the free market structure especially when bandwidth for communications is limited.     

Linking manufacturing strategy decisions on process choice with manufacturing planning and control systems

For any manufacturing firm, theory suggests that the firm is better off if the manufacturing planning and control (MPC) system supports the market strategy as well as the manufacturing strategy. Typically, the strongest link between market requirements and manufacturing strategy concerns the process choice, i.e. choosing a manufacturing process that supports a firm's competitive priorities. The general aim of this paper is to examine the role of the MPC system in a manufacturing strategy. More specifically, the purpose is to link market requirements, product characteristics, and the process choice to the MPC system. A special focus will be placed on the link between the process choice and the design of the MPC system. Two key factors are identified as major processspecific elements influencing the MPC system design: the number of planning points, and set-up times at individual resources. The process choice affects the lower planning levels of the MPC systems, where the physical reality of the plant becomes apparent. This is especially true for production activity control, but also for requirements planning (material and capacity). Concerning the MPC system design for longer-term planning, such as sales and operations planning and master scheduling, the impact from market requirements and product characteristics dominates.     

Automated diagnostic aids: The effects of aid reliability on users' trust and reliance

We examined the effects that different levels of, and changes in, automation reliability have on users' trust of automated diagnostics aids. Participants were presented with a series of testing trials in which they diagnosed the validity of a system failure using only information provided to them by an automated diagnostic aid. The initial reliability of the aid was either 60, 80 or 100% reliable. However, for participants initially provided with the 60%-reliable aid, the accuracy of the aid increased to 80% half way through testing, whereas for those initially provided the 100%-reliable aid, the aid's reliability was reduced to 80%. Aid accuracy remained at 80% throughout testing for participants in the 80%-reliability group. Both subjective measures (i.e. perceived reliability of the aids and subjective confidence ratings) and objective measures of performance (concurrence with the aid's diagnosis and decision times) were examined. Results indicated that users of automated diagnostic aids were sensitive to different levels of aid reliabilities, as well as to subsequent changes in initial aid reliabilities. However, objective performance measures were related to, but not perfectly calibrated with, subjective measures of confidence and reliability estimates. These findings highlight the need to distinguish between automation trust as a psychological construct that can be assessed only through subjective measures and automation reliance that can only be defined in terms of performance data. A conceptual framework for understanding the relationship between trust and reliance is presented.     

Flexibility in manufacturing enterprises

A manufacturing enterprise is a collection of interrelated, flexible, optimized business processes delivering value to the customers through high quality products and services, faster than competition. This view of an enterprise enables one to consider the entire business system including the suppliers, product development, manufacturing, logistics, distribution, and retailing and to smoothen out the interfaces between them. Performance measures and performance measurement are important for monitoring, control and management. We identify and discuss eight performance measures for generic business processes. These include lead time, customer service, dependability, quality, flexibility, cost, capacity, and asset utilization. In this paper, we concentrate on flexibility of business processes with special emphasis on the supply chain and order-to-delivery processes. We attempt to provide clear definitions and measures of various types of flexibilities as well as discuss the relationship between product structure and supply chain flexibility. The relationship between uncertainties, flexibility, technology, and product structure is clearly brought out in this paper.