A cross-sector review on the use of value stream mapping

Value Stream Mapping (VSM) has become a popular method for lean thinking and implementation in recent years. Previous reviews related to VSM are limited to individual sectors due to varied research objectives. The lack of studies which focus on cross-sector review of VSM studies is impeding the implementation of VSM by both lean researchers and practitioners. The paper aims to determine the-state-of-the-art development of VSM in five sectors, including manufacturing, health care, construction, product development and service sectors. A total of 131 journal articles are reviewed and analysed from the period of 1999–12/2016. The analysis covers the complete implementation cycle of VSM, including metrics for current state map, improvement techniques for future state map, benefits and achievements of VSM application, and critical success factors for VSM implementation. Cross-sector comparisons and investigations are conducted to understand the differences of VSM implementations in various sectors to facilitate VSM development and increase the number of successful VSM implementation. The results suggest that understanding value and waste in a diverse value stream environment and ensuring the suitability and usability of traditional lean metrics/techniques within the different flow settings are central to the VSM development.     

A comparison of focused cellular manufacturing to cellular manufacturing and job shop

The purpose of this study is to compare a focused cellular manufacturing environment with traditional cellular manufacturing, and job shop environments. We define focused cellular manufacturing as a configuration scheme that groups components by end-items and forms cells of machines to fabricate and assemble end-items. In addition, this research includes three levels of batch sizes and two levels of set-up times in its performance criteria which few researchers in this area have done. The results indicate that the focused cellular manufacturing scheme has a batching advantage. This advantage dominated the balanced machine utilization benefit of the job shop configuration scheme and out weighed the set-up time reduction advantage of the cellular manufacturing scheme for average end-item completion times and average work-in-process inventory levels. The cellular manufacturing and job shop schemes overcame the batch size advantage only when batch sizes were small or set-up times were large.     

A simulation-enhanced value stream mapping approach for optimisation of complex production environments

Value stream mapping (VSM) is a widely adopted method for transformation of production environments into a lean operational state. The straightforwardness as well as the completeness, with which processes are analysed and optimised, are key to the success of the method originating from the automotive industry. However, these attributes of the ‘paper and pencil’ approach result in limitations when applying VSM in complex production environments. This research paper targets to overcome these limitations, specifically in production environments involving significant demand variability, complex routing and cost factors which potentially increase with lean implementation. For this purpose, an enhanced VSM method is developed, which utilises discrete event simulation (DES). The method features a feasibility and trade-off analysis which is incorporated into the VSM procedure. A case study covering a process of exhaust gas purification catalyst production is then conducted to test the newly developed method. The VSM project yields a shop floor lead time reduction from 11.4 to 1.4?d. The additional DES feasibility and trade-off analysis determines customer demand fulfilment and quantifies the monetary benefit of the future state. In that way, potential iterative implementation which is inherently oppositional to the lean philosophy is avoided.     

Tools and techniques for enabling sustainability through lean initiatives

There has been a paradigm shift in the manufacturing systems. Lean manufacturing is a manufacturing system that is focused on the elimination of wastes thereby facilitating process streamlining and waste reduction. In the recent days, the need for environmental consciousness is very much realized. The environmental waste is regarded as the ninth waste. This article focuses on the exploration of various issues of sustainability using lean initiatives. Also, some of the strategies/techniques that would enable the achievement of sustainability objectives using lean initiatives are presented.     

A production scheduling plan for a diversified product line

This paper describes a production control plan which may be -used in a shop whose product line consists of numerous items which vary extensively in their demand pattern.

The plan is capable of: (a) stabilizing production by allowing inventories to fluctuate with moderate demand fluctuations; (b) minimizing inventories of finished goods while providing protection against serious Btockout; (c) detecting significant changes in demand patterns and revising production schedules accordingly; and (d) scheduling production economically.

Employing several well-known concepts, such as the control limits principle used in quality control, the plan considers simultaneously forecasted demand, forecast error, inventory position and shop capacity to arrive at production decisions. For this purpose, control limits are applied to both demand and inventory, and production is stabilized with a simple production smoothing procedure. Simulation results, based on data taken from a medium size production shop, demonstrate the plan effectiveness.

Overall, the paper emphasizes operational features rather than theoretical concepts, However, it is shown that the plan is amenable to generalized treatment.     

Managing flexible manufacturing technology: Must parts in an FMS always move in a job-shop manner?

The literature typically assumes that an FMS consists of a number of machines of different processing capability. Furthermore, in view of the inherent flexibility of an FMS, many researchers believe that 'flexible' implies that a wide variety of parts can be, and should be, processed simultaneously in an FMS. To do otherwise will inevitably mean some machines are idle and hence the FMS may become a tremendous waste. This paper is an attempt to study this issue. Unlike a job shop, which is typically an eclectic collection of machines of different process capabilities, most flexible manufacturing systems consist of only one or two types of versatile programmable machines. We contend that the FMS machines are analogous to the multi-skilled workers in lean production. In lean production, workers work in teams. It is common for each team to work on one job at a time, from start to finish. Jobs are not passed around from worker to worker. Likewise, machines in an FMS can be assigned into 'teams', where each 'team' is dedicated to process a single part type (or family) at a time. Parts do not necessarily have to move from machine to machine in a job shop manner.     

Generating daily production plans for complex manufacturing facilities using multi-objective genetic algorithms

Modern production tracking and planning systems produce good inventory plans. Unfortunately, daily production problems often produce an inventory profile that is significantly different from that of the production plan. Several manufacturing objectives are available to remedy inventory profile problems, but a weighted combination of them can be more effective. We propose using genetic algorithms to search for best weight assignments in multi-objective daily production planning problems. This approach takes snapshots of a factory's inventory, equipment capacity and demands to generate a near optimal shop floor daily production plan. The implemented system runs on a daily basis at midnight for 40 min and generates the following day's production plan. Tests of this system in a large-scale semiconductor manufacturing facility show the proposed approach generates production plans of high quality in reasonable run times under many factory conditions.     

Evaluation of leagility in supply chains using fuzzy logic approach

In the changing business environment, manufacturing firms can survive by catering to the dynamic demands of the modern customers. Lean principles imply zero inventory and agile principles necessitate safety inventory to tackle volatile market conditions. The leagile paradigm is gaining importance in the contemporary scenario which includes both lean and agile principles. This article presents the conceptual model of leagility imbibed with lean and agile principles. A fuzzy logic approach has been used for the evaluation of leagility in supply chains. This article is used to compute the performance of supply chains using both lean and agile concepts as leagility supply chains using a fuzzy logic approach.     

Capacity allocation strategies in a hypothetical job-shop

In today's manufacturing environment, many companies are stressing due date performance and inventory levels as primary measures of shop performance. This is contrary to the traditional performance measure of resource efficiency. In response to this changing emphasis, and partly due to the success of many Japanese companies that emphasize inventory reduction and due date performance, companies may seek to add capacity cushions in an attempt to become more responsive to customer demands. In this paper, several strategies are studied to determine how best to allocate the additional capacity. Results suggest that the choice of allocation strategy is dependent on the level of fluctuations in the manufacturing process.     

Case Study of Lean in Hospital Admissions to Inspire Culture Change

Abstract

The hospital admissions process is a distinct experience for patients as this is where they start their journey for medical care, usually with a mix of anxiety and anticipation about what is to follow. This process also happens to be long and stressful, with numerous steps, frequent delays, and the occasional glitches along the way. In this study, we used lean thinking and discrete-event simulation to map and model the inpatient admissions process at a multi-specialty hospital in order to improve patient flow and reduce unnecessary waiting and handling by patients and staff. We found that by applying a combination of simple but complementary lean techniques, it was possible to reduce the total patient time in the system by up to 43%, without incurring additional costs or using more resources. The potential for achieving substantial improvements at low cost, combined with the approach of validation-prior-to-implementation adopted in this study, can both help process engineers and engineering managers to build support for any proposed lean initiative. This also makes it possible to sustain continuous improvement in the long term, which is at the heart of the lean approach.     

Lean Implementation and Organizational Transformation: A Literature Review

Manufacturing organizations are constantly striving to develop more effective and flexible means for managing challenges due to globalization and increasing customer expectations. This has led to increased efforts by the business community to research and implement the Toyota Production System, or lean manufacturing, to address these challenges. These efforts have resulted in numerous publications on lean manufacturing, including research reports, scholarly articles, and trade magazine articles. However, the existing body of knowledge on lean manufacturing is disperse and diverse in nature with respect to the application and implementation of lean tools and practices, making it difficult for researchers and practitioners to gain a real grasp of this topic. In this article, we have comprehensively organized the existing work on implementation of lean manufacturing in a more structured way, enabling engineering management practitioners to more easily identify knowledge and best practices and enabling researchers to identify gaps in the extant literature. Lastly, drawing from the organizational science literature, this article also provides important insights on lean manufacturing from the perspective of organizational learning, innovation, and \culture.     

A practical approach to scheduling a multistage,multiprocessor flow-shop problem

This paper describes a rubber manufacturing system and the numerous technological, operating and quality constraints governing its scheduling process. The complex system resembles a flow-shop problem where all jobs share the same general processing order on a progression of machines. The manufacturing system is defined in terms of production stages and parallel processing lines. One stage can process two or more jobs simultaneously. Jobs are often split on the last stage so that two or more parallel processing lines process the same job simultaneously. The scheduling for such a multistage, multiprocessor flow shop is dominated by the quality constraints. A pragmatic approach is provided in which a schedule is constructed through extensive iterations of analysis and simulation.     

Challenges and trends in the allocation of the workforce in manufacturing shop floors

This paper presents a critical and focused review of definitions, challenges and developments of the workforce allocation system in manufacturing shop floors with a particular emphasis on response to changes and disturbances. The continuously changing requirements in production environments have been the driving force behind several stages of evolution experienced by management of workforce allocation. The paper includes an in-depth examination of the phenomena of changes and disturbances in the production shop floor. This is followed by an assessment of the readiness of workforce allocation systems to respond to such events with respect to both workforce perception and system architecture. Recent developments of the workforce allocation models suggest that the use of intelligent and distributed systems and techniques offer solutions that are responsive, flexible, and multi-criteria. To this end, an overview of a recent study in the application of the principles of holonic manufacturing systems, as an example of intelligent system approach to develop a flexible workforce allocation model, is presented.     

Synchronized manufacturing at final assembly and feeder shops

Many manufacturing environments consist of a final assembly shop that receives components from various feeder shops. Suppose the final assembly shop assembles a mix of products, each requiring varying amounts of different components. Thus, the sequence in which products are assembled imposes time-dependent demands on the feeder shops. Such problems are often found in the assembly of high-tech telecommunications systems and in the assembly of mixed models of automobiles. We develop a variety of models that link the work-in-process inventory in the feeder shop and the finished component inventory to the component production interval and the final assembly sequence. The manufacturing disciplines considered include push, look-ahead and kanban. Feeder shops are assumed to manufacture components continuously, periodically, or at a fixed lot size. Simple performance characteristics of the feeder shop are derived to provide insight into synchronized manufacturing issues and to help evaluate the effect of different final assembly sequences on feeder shops.     

A time-based quantitative approach for selecting lean strategies for manufacturing organisations

Lean strategies have been developed to eliminate or reduce waste and thus improve operational efficiency in a manufacturing environment. However, in practice, manufacturers encounter difficulties to select appropriate lean strategies within their resource constraints and to quantitatively evaluate the perceived value of manufacturing waste reduction. This paper presents a methodology developed to quantitatively evaluate the contribution of lean strategies selected to reduce manufacturing wastes within the manufacturers’ resource (time) constraints. A mathematical model has been developed for evaluating the perceived value of lean strategies to manufacturing waste reduction and a step-by-step methodology is provided for selecting appropriate lean strategies to improve the manufacturing performance within their resource constraints. A computer program is developed in MATLAB for finding the optimum solution. With the help of a case study, the proposed methodology and developed model has been validated. A ‘lean strategy-wastes’ correlation matrix has been proposed to establish the relationship between the manufacturing wastes and lean strategies. Using the correlation matrix and applying the proposed methodology and developed mathematical model, authors came out with optimised perceived value of reduction of a manufacturer's wastes by implementing appropriate lean strategies within a manufacturer's resources constraints. Results also demonstrate that the perceived value of reduction of manufacturing wastes can significantly be changed based on policies and product strategy taken by a manufacturer. The proposed methodology can also be used in dynamic situations by changing the input in the programme developed in MATLAB. By identifying appropriate lean strategies for specific manufacturing wastes, a manufacturer can better prioritise implementation efforts and resources to maximise the success of implementing lean strategies in their organisation.     

Conceptions and operational use of value and waste in lean manufacturing – an interpretivist approach

In this article, we explore how the key concepts of lean manufacturing, value, value adding and waste are conceived and operationally used by Lean trainers in operational work processes. A comparative case study with a mixed method approach, using an explanatory sequential design, was conducted. This means that a set of quantitative data were collected, which was followed by the collection of qualitative data with the purpose of explaining and understanding the quantitative measures. An interpretivist approach is used as a framework, which implies a perspective on contemporary operations management paradigms, such as lean manufacturing, as a continuous construction of inter-subjective experiences. What becomes evident in the empirical findings is that there are both similarities and differences in the Lean trainers conceptions and use of value adding and waste. The similarities and differences can be explained by variations in two dimensions: (a) the character of the work process, which ranges between mechanical and craftsmanship, and (b) Lean trainers approach to key concepts, which ranges between being rule-based and reflective. By using a research design where the concepts of value adding and waste were used simultaneously, and adopting an interpretivist approach on lean manufacturing, we were able to reveal conditions that in other cases remain hidden.     

Integrated optimisation of scheduling and ordering based on semi-finished goods delayed differentiation

The implementation of dynamic ordering policies is becoming increasingly important for the competitiveness of modern manufacturing systems. However, existing models on dynamic ordering pay little attention to production scheduling, which greatly affects the fulfilment of dynamic ordering, especially in complex manufacturing systems. Therefore, it is imperative to establish a new model which integrates both dynamic ordering and production scheduling. Accordingly, a quantitative measurement method for integration is needed. To this end, this paper proposes a semi-finished goods delayed differentiation (SFGDD) model by taking into account integration of the scheduling inventory control and dynamic ordering simultaneously. The objective of this model is to study the relationship between the shop floor inventory and the ordering control based on the semi-finished goods dynamic dispatching mechanism. In addition, the days of inventory (DOI) and a backorder penalty exponential function are developed to quantitatively measure such a relationship. To obtain the optimal results, this paper employs a heuristic genetic algorithm (HGA) with a heuristic encoding scheme to synchronise the generation and selection of inventory variables coherently. A case study on a semiconductor assembly and test manufacturing (ATM) is presented, and a significant revenue enhancement and inventory reduction are achieved accordingly.     

Stochastic economic lot sizing and scheduling problem with pitch interval,reorder points and flexible sequence

This paper presents a solution for a class of the stochastic economic lot sizing scheduling problem that is typical of the replenishment pull system proposed by the lean manufacturing approach. In this class, lots of any product are produced in fixed intervals called pitch. The proposed solution uses flexible production sequences and reorder points that are compatible with the concepts of supermarket and level production. It adopts the queuing discipline obtained from a fluid model that approximates the stochastic process of arrival and production orders. Given the queuing discipline, an iterative algorithm returns a near-optimal solution for the system. The proposed approach allows us possible to differentiate inventory cost and service levels by product, and the stock required is lower than that required by the discipline ‘first stock out, first out’. The algorithm is fast and stable, allowing its frequent use in real-world instances.