An agent-based heuristics optimisation model for production scheduling of make-to-stock connector plates manufacturing systems

The manufacturing systems’ success directly relates to their accurate, reliable and flexible schedules, including how production is planned and scheduled and which constraints are considered in generating the schedules. The study's objective arises from the need to generate an optimal production scheduling system in a connecting plates manufacturing company that works on a Make-To-Stock basis. This research investigates the impact of demand and operational constraints on production schedules, including the facility capacity, operators and machines availability, raw materials availability, inventory level and warehouse capacity. A multi-agent-based optimisation model is developed to face the complexity of considering demand and operational constraints and reflects their impact on generating a reliable production schedule. This model involves a proposed heuristic algorithm that considers demand and operations constraints in such a manufacturing environment and optimises the production schedule based on these restrictions/requirements. A real-life case study based on a connecting plates manufacturer company is used as a test bench of the proposed agent-based heuristic optimisation model. The proposed algorithm is compared with other related approaches to check its superiority based on key criteria, including inventory levels, missed/unsatisfied orders and total production time. Results show that the proposed heuristics algorithm reduced the number of missed orders by 34% compared with similar approaches

On Production and Subcontracting Strategies for Manufacturers with Limited Capacity and Backlog-Dependent Demand

We study a manufacturing firm that builds a product to stock to meet a random demand. If there is a positive surplus of finished goods, the customers make their purchases without delay and leave. If there is a backlog, the customers are sensitive to the quoted lead time and some choose not to order if they feel that the lead time is excessive. A set of subcontractors, who have different costs and capacities, are available to supplement the firm's own production capacity. We derive a feedback policy that determines the production rate and the rate at which the subcontractors are requested to deliver products. The performance of the system when it is managed according to this policy is evaluated. The subcontractors represent a set of capacity options, and we calculate the values of these options

An agent-based heuristics optimisation model for production scheduling of make-to-stock connector plates manufacturing systems

The manufacturing systems' success directly relates to their accurate, reliable and flexible schedules, including how production is planned and scheduled and which constraints are considered in generating the schedules. The study's objective arises from the need to generate an optimal production scheduling system in a connecting plates manufacturing company that works on a Make-To-Stock basis. This research investigates the impact of demand and operational constraints on production schedules, including the facility capacity, operators and machines availability, raw materials availability, inventory level and warehouse capacity. A multi-agent-based optimisation model is developed to face the complexity of considering demand and operational constraints and reflects their impact on generating a reliable production schedule. This model involves a proposed heuristic algorithm that considers demand and operations constraints in such a manufacturing environment and optimises the production schedule based on these restrictions/requirements. A real-life case study based on a connecting plates manufacturer company is used as a test bench of the proposed agent-based heuristic optimisation model. The proposed algorithm is compared with other related approaches to check its superiority based on key criteria, including inventory levels, missed/unsatisfied orders and total production time. Results show that the proposed heuristics algorithm reduced the number of missed orders by 34% compared with similar approaches

Capacity flexibility of a maintenance service provider in specialized and commoditized system environments

In the last decades, after-sales services have become increasingly important since service is a source of differentiation as well as a lucrative business opportunity due to the substantial amount of revenue that can be generated from the products in use throughout their life cycle. Following this trend, many after-sales service providers have emerged in the market or evolved as semi-autonomous units within the OEM (Original Equipment Manufacturer) companies. In this thesis, we focus on the maintenance aspect of after-sales services. We assume that a maintenance service provider (MSP) is running a repair shop in an environment with numerous operating systems that are prone to failure. The MSP is responsible for keeping all systems in an environment up and working. We mainly focus on two types of environments: 1) Specialized System Environment 2) Commoditized System Environment. The systems in the first environment are highly customized. They are designed and built specifically following the owners’ precise requirements. Defense systems, specific lithography systems, mission aircrafts or other advanced/complex, engineer-to-order capital goods are examples of such specialized systems. Due to the diversity of owners’ requirements, each system develops many unique characteristics, which make it hard, if not impossible, to find a substitute for the system, in the market as a whole. In the second environment, the systems are more generic in terms of their functionality. Trucks, cranes, printers, copy machines, forklifts, computer systems, cooling towers, some common medical devices (i.e. anesthesia, x-ray and ultrasound machines, etc…), power systems are examples of such more commoditized systems. Due to the more generic features of the owners’ requirements, it is easier to find a substitute for a system in the market, with more or less the same functionality, for short-term hiring purposes. Upon a system breakdown, the defective unit (system/subsystem) is sent to the repair shop. MSP is responsible for the repair and also liable for the costs related to the down time. In order to alleviate the down-time costs, there are chiefly two different downtime service strategies that the MSP can follow, depending on the environment the repair shop is operating in. In the specialized system environment, the MSP holds a spare unit inventory for the critical subsystem that causes most of the failures. The downtime service related decision in such a case would be the inventory level of the critical spare subsystems. On the other hand, in the commoditized system environment, rather than keeping a spare unit inventory, the MSP hires a substitute system from an agreed rental store/3rd party supplier. The downtime service related decision in this case is the hiring duration. Next to the above downtime service related decisions, repair shop’s capacity level is the other primary determinant of the systems’ uptime/availability. Since maintenance is a labor-intensive industry, the capacity costs constitute a large portion of the total costs. Increasing pressure on profitability and the growing role of External Labor Supplier Agencies motivate service provider firms to scrutinize the prospects and possibilities of capacity flexibility by using contingent workforce. For various reasons, flexible capacity practices in real life are often periodic, and the period length is both a decision parameter and a metric for flexibility. A shorter period length implies more frequent adapting possibilities and a better tailoring of the capacity. On the other hand, the flexible capacity cost per unit time is higher for shorter period lengths due to the compensating wage differentials, which models the relation between the wage rate and the unpleasantness, risk or other undesirable attributes of the job. Certainly, short period length in this context is an undesirable attribute for the flexible capacity resource, as it mandates the resource to switch tasks and to be ready/available more frequently, without the guarantee that s/he will be actually employed. Therefore, we propose several empirically testable functional forms for the cost rate of a flexible capacity unit, which are decreasing with the period length and, in the limit, approaches to the cost rate of a permanent capacity unit from above. In the light of discussions above, we investigate three different capacity modes in this dissertation: ¿ Fixed Capacity Mode: In this mode, all of the capacity is permanent and ready for use in the repair shop. This mode serves as a reference point in order to assess the benefits of other flexible capacity modes. The relevant capacity decision in this mode is the single capacity level of the repair shop. ¿ Periodic Two-Level Capacity Mode: In this mode, we assume two levels of repair shop capacity: permanent and permanent plus contingent capacity levels. The permanent capacity is always available in the system, whereas the deployment of the contingent capacity is decided at the start of each period based on the number of units waiting to be repaired in the shop. The relevant capacity decisions in this mode are the permanent and contingent capacity levels, the period length and the states (in terms of number of defective units waiting) where the contingent capacity is deployed. ¿ Periodic Capacity Sell-Back Mode: In this mode, the failed units are sent to the repair shop at regular intervals in time. Due to this admission structure, when the repair of all the defective units in the repair shop are completed in a period, it is known that no new defective parts will arrive to the shop at least until the start of the next period. This certainty in idle times allows for a contract, where the repair shop capacity is sold at a reduced price to the capacity agency where it is assigned to other tasks until the start of the next period. The original cost of the multi-skilled repair shop capacity per time unit is higher than the permanent capacity cost that is mentioned in previous modes due to the compensation factors such as additional skills, frequent task switching and transportation/transaction costs. Similar to the previous capacity mode, the compensation decreases with the length of the period length. The relevant capacity decisions in this mode are the capacity level and the period length. The primary goal of this thesis is to develop quantitative models and methods for taking optimal capacity decisions for the repair shop in the presence of the capacity modes described above and to integrate these decisions with the other downtime service decisions of the MSP for two different types of system environments (specialized vs. commoditized). After the introduction of the problem, concepts and literature review are given in Chapters 1. In Chapter 2, we focus on the use of capacity flexibility in the repair operations of the MSP in specialized system environment. The capacity related decisions are integrated with the decision on the stock level of the spare unit inventory for all three capacity modes. In Chapter 3 we investigate the same three capacity modes in a (partially) commoditized system environment, where hiring a substitute system for a pre-determined, uniform duration becomes the conventional method upon a failure. In this chapter the decision on the hiring duration is integrated with the other capacity related decisions. Then we provide some preliminary analysis and give the early results on the hybrid strategy where both "keeping stock" and "hire substitute" strategies are followed. Finally in Chapter 4, we summarize our results, give the conclusion and discuss the topics covered in this thesis with a brief exploration on the future research. The numerical results reveal that, in both specialized and commoditized system environments, substantial cost savings (up to 70%) can be achieved under periodic two-level capacity and periodic capacity sell-back modes compared to the fixed capacity mode. However, both period length and the compensation scheme of the capacity resources greatly influence the savings, even in some cost instances, flexible modes (periodic two-level and capacity sell-back) become less economical compared to the fixed capacity mode. Cost parameter instances in which each of the 3 capacity modes becomes cost-optimal, the characteristics of the cost savings and the sensitivity analysis of cost/policy parameters are investigated in both of the system environments in Chapter 2 and Chapter 3, respectively. In the commoditized system environment, under the same cost parameter settings, the hiring substitute from an external supplier for a fixed duration causes a better, more refined and certain control compared to keeping an inventory. Hybrid strategy, in which a substitute is hired after a stock-out instance, is applicable in commoditized as well as commoditizing (previously specialized systems that are in the ongoing commoditization process) system environments. Hybrid strategy outperforms both "only keeping stock" and "only hiring substitute" alternatives; however, in the commoditized system environment, a MSP may still have a proclivity to employ the "hiring substitute" strategy only, because it does not require any initial investment, which is convenient for SMEs. These issues will be explicated further in Chapter 5. We believe that the framework, the design and analysis of the problems addressed as well as the results and the insights obtained in this dissertation can help and motivate other researchers/practitioners to further investigate the cost saving prospects from capacity flexibility in maintenance service operations. We also anticipate that the commoditization framework described in this thesis will be increasingly useful in the future, since the commoditization of the parts/machines will be much more widespread, pushing all the after-sales service providers to compete on the efficiency of their operatio

Optimal control of production and maintenance operations in smart custom manufacturing systems with multiple machines

Enterprises equipped with IoT (Internet of Things) are the new generation of manufacturing industry. There is a need for new optimization models which incorporate the advantages of IoT. In this paper, a new mathematical model and heuristic algorithm are developed to minimize the total cost in a multiple machine environment which enables the industries to take economically better decisions and effectively use their resources. A heuristic algorithm is developed for identical machines which process with the same tool. A system in which jobs with stochastic workloads arrive randomly and upon arrival, their workload is facilitated by IoT. The proposed algorithm determines the assignment of workload to the machine and processing speed. The algorithm works for both online and offline frameworks

A Framework for Firm-Level Critical Material Supply Management and Mitigation

Organizations of all sizes are vulnerable to critical material supply disruptions. Although there is a significant body of literature that examines how large entities such as nations and governments can assess and mitigate criticality, there is very little work that addresses firm-level criticality in a way that is actionable for businesses. This work uses literature review and case study analysis to understand the impact of critical material supply risk at the firm level, and to determine salient internal indicators. A total of 42 criticality studies were reviewed and the findings were used to develop a framework to assess and monitor criticality risk using internal firm-specific data. The framework incorporates three categories of risk including product concept viability, production, and profitability. It also contains four key business functions including finance, procurement, marketing, and production. These aspects were chosen because they are relevant to all businesses that produce and sell manufactured goods, and because they represent dynamics that are within the control of an individual firm. Unlike the global and national level indicators emphasized in most current research, the indicators proposed in this research are derived from data such that firms can compile it with reasonable ease. Finally, this work considers the role of the organization in criticality risk assessment and mitigation through an examination of the data needed to complete the aforementioned framework and the likely sources of that information. The findings of this analysis elucidate the gap between internal and external and micro and macro criticality assessment, as well as provide a framework for firm-level criticality mitigation

Customer Information Driven After Sales Service Management: Lessons from Spare Parts Logistics

Over the years, after sales service business in capital goods and high tech sectors has experienced significant growth. The drivers for growth are higher service profits, increased competitions, and primary market contractions. The enablers for growth include information driven service processes and a move from one size fit all oriented warranty contracts to service level agreement offerings that differ in service prices and response guarantees. Although, these trends provide an opportunity to the service providers to match their service resources to the time varying service requirements of a heterogeneous customer base, the tools and techniques to support decision makers are lacking as of to date. In this thesis, we aim to make a small contribution in closing this gap. We gain business environment related insights of after sales service by studying it at a major computer equipment manufacturer. After sales service is a complex task that is accomplished by making a series of strategic, tactical, and operational decisions in maintenance services management, spare parts logistics management and spare part returns management. We exclusively focus on operational and tactical decisions in spare parts logistics management. We identify that customer information, or more specifically installed base information is a valuable source to support spare parts logistics decisions at the operational and tactical levels. We present an execution technique for spare parts logistics that uses installed base information to provide differentiated service to a heterogeneous customer base and results in additional profits for the service provider. Finally, we study execution decisions in spare parts logistics and spare part returns management for their interrelation. We highlight that explicit consideration of this interrelation yields additional benefits

Creating a Market Economy in Eastern Europe: The Case of Poland

macroeconomics, market economy, Eastern Europe, Poland

An Empirical Investigation Of Information Technology Mediated Customer Services In China

Information technology mediated customer service is a reality of the 21st century. More and more companies have moved their customer services from in store and in person to online through computer or mobile devices. Using 208 respondents collected from two Chinese universities, this paper investigates customer preference over two service delivery model (either in store or online) on five type of purchasing (retail, eating-out, banking, travel and entertainment) and their perception difference in customer service quality between those two delivery model. Results show that a majority of Chinese students prefer in store and in person for eating out. For ordering tickets for travel and entertainment, they prefer computer/mobile device. For retail purchasing and banking, less than half of the students prefer in person services. In general, the results show that ordering through computer/mobile devices has become more popular in China and has received higher rating for most of customer service quality except security compared to ordering in store. In addition, it is found that there exist a gender difference in purchasing preference and perception in service delivery quality in China