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Int. J. Industrial and Systems Engineering, Vol. 4, No. 3, 2009 229 Developing a value stream map to evaluate breakdown maintenance operations Rapinder Sawhney, Soundararajan Kannan and Xueping Li* Department of Industrial and Information Engineering, University of Tennessee, 416 East Stadium Hall, ...

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Developing a value stream map to evaluate breakdown maintenance operations Rapinder Sawhney, Soundararajan Kannan International Journal of Industrial and Systems Engineering

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Int. J. Industrial and Systems Engineering, Vol. 4, No. 3, 2009

Developing a value stream map to evaluate breakdown maintenance operations Rapinder Sawhney, Soundararajan Kannan and Xueping Li* Department of Industrial and Information Engineering, University of Tennessee, 416 East Stadium Hall, Knoxville, TN 37996, USA Fax: 865-974-0588 E-mail: [email protected] E-mail: [email protected] E-mail: [email protected] *Corresponding author Abstract: Maintenance management has found new vigor and purpose to increase equipment capacity and capability due to increasing focus on lean manufacturing (lean) in today’s competitive environment. Tremendous efforts have been made to develop different types of maintenance strategies for enhancing the performance of equipment but nothing has been done to actually streamline Breakdown Maintenance Activities (BMA). This refers to systematically evaluating the Non-Value Added (NVA) activities within BM. The primary lean tool that provides insights on identifying and analysing NVA activities is Value Stream Mapping (VSM). However, traditional VSM cannot be utilised ‘as is’ because the BMA do not completely correspond with VSM terminology. Therefore, this paper develops a VSM to evaluate BM operations. Keywords: lean manufacturing; maintenance; VSM; value stream mapping. Reference to this paper should be made as follows: Sawhney, R., Kannan, S. and Li, X. (2009) ‘Developing a value stream map to evaluate breakdown maintenance operations’, Int. J. Industrial and Systems Engineering, Vol. 4, No. 3, pp.229–240. Biographical notes: Rapinder Sawhney is an Associate Professor and Associate Department Head in the Department of Industrial and Information Engineering at the University of Tennessee, Knoxville. He was the recipient of Lean Fellowship and was responsible for enhancing the competitiveness of Tennessee industry utilising the Lean Manufacturing concept. His research interests are developing lean methods to implement lean, which have resulted in various publications. His experience includes working for over 100 of organisations in implementing the lean concept. Soundararajan Kannan is pursuing his Master of Science Degree in the Department of Industrial and Information Engineering at the University of Tennessee, Knoxville. His areas of research interest include lean manufacturing, lean maintenance, supply chain management, quality management, and system reliability. He has been actively involved in sponsored research and industrial projects.

Copyright © 2009 Inderscience Enterprises Ltd.

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R. Sawhney et al. Xueping Li is an Assistant Professor of Industrial and Information Engineering and the Director of the Intelligent Information Engineering Systems Laboratory (IIESL) at the University of Tennessee – Knoxville. He holds a PhD from Arizona State University. His research areas include information assurance, scheduling, web mining, supply chain management, lean manufacturing, and sensor networks. He is a member of IIE, IEEE and INFORMS.

1

Introduction

Lean manufacturing has been adopted as one of the initiatives by many major businesses in order to remain competitive in the global market. As a generic process management philosophy mainly derived from the Toyota Production System (Womack et al., 1992), it focuses on reduction of the wastes and to improve overall customer value. With the modern manufacturers trying to strive for lean in order to reduce inventory, production lead time, direct labour, indirect labour, space requirements, quality costs and material costs (Moore, 2002; Agarwal et al., 2006; Shah and Ward, 2007), the emphasis on equipment availability has become even more critical in order for the manufacturers to successfully implement and sustain lean. One example is cellular manufacturing, a concept of lean, in which equipments are grouped together according to the process sequence to form a cell. These cells are extremely efficient in achieving single piece flow of product but at the same time extremely susceptible. The susceptibility is due to the fact that cells are highly dependent on equipment availability. When equipment breaks down in a manufacturing cell, it shuts down the entire production line, until the equipment is brought back to its normal working condition. Hence high amount of non-value added time between machine stoppage and completion of repair, compounds the production loss. Another dimension for streamlining breakdown maintenance activities is the cost associated with downtime. The cost of maintenance downtime, as stated in Cooper (2002a), is typically $500 per hour for a stand-alone machine, $1,500–$8,500 per hour for a cell or line of machines, and up to $3,500 per minute ($181,500 per hour) for an entire auto factory line. Further, the cost of downtime in lean manufacturing environment is 5 to 30 times more than other manufacturing environment as it directly and immediately results in lost opportunities (Cooper, 2002b). Maintenance cost is directly proportional to the downtime hours and hence increase in the downtime hours due to non-value added breakdown maintenance activities can alarmingly increase the maintenance costs. Thus, there is an immediate need for an approach that explicitly evaluates the breakdown maintenance function to eliminate any unnecessary time between machine stoppage and the completion of the repair function.

2

Literature review

One of the primary lean tools that was found in the literature and has been effectively used in evaluating non-value added activities is Value Stream Mapping (VSM). It is a tool that helps in visualising a system by the representation of information and

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material flow. It also creates a common language about a process, by which purposeful decisions can be made to eliminate the non value adding activities. A collection of all actions (value-added and non-value-added) are included in a value stream and are required to bring products through the main flows, starting from raw materials and ending with the customers (Rother and Shook, 1999). The ultimate goal of VSM is to identify and eliminate the waste in the stream. VSM uses a predefined set of standardised icons to describe a highly complex system in a tractable 2-D format, which simplifies the system wide facilities insight and understanding and thus provides a common language for communication of the insight (McManus and Millard, 2002). A ‘three-step’ approach is commonly adopted. The first step is to identify a particular product or product family for potential improvement. The second step is to construct a current state map which captures how things are currently done as a snapshot by walking along the actual processes. The future state map in created in the third step to illustrate how the system behaves after the inefficiencies are removed. The future state map is the basis to make necessary changes. Seven different VSM tools namely, big picture mapping (Rother and Shook, 1999), supply chain response matrix (Jones et al., 1997), production variety funnel (New, 1974), quality filter mapping (Hines and Rich, 1997), demand amplification mapping (Hines and Taylor, 2000), decision point analysis (Jones et al., 1997) and physical structure mapping (Hines and Rich, 1997) were developed to optimise individual operations within a supply chain. However, most of them fall short of the linkage and visualisation of the material flow and information flow throughout the entire supply chain. Moreover, none of them directly correspond to the breakdown maintenance operations and hence cannot be applied ‘as is’. This clearly illustrates the need of a value stream map that is specific to breakdown maintenance and which in turn can be used to evaluate the non-value added activities within breakdown maintenance operations. It is nontrivial to raise the question that how to make lean and VSM viable. Many companies find it is difficult to gain the management commitment to implement lean relying on traditional approaches (Abdulmalek and Rajgopal, 2007). Differences exist in many aspects including raw material procurement, inventory control, human resource management, and product control. Quantifiable evidences are needed to convince the decision makers to adopt lean (Detty and Yingling, 2000). Simulation is an obvious choice to quantify the gains in early planning and assessment stages of VSM. It is capable of handling uncertainty, maintaining the operational details, and creating dynamic views of inventory levels, lead times, and machine utilisation and breakdowns (Rahn, 2001; McDonald et al., 2002; Kelton et al., 2006). This paper will develop a value stream map to evaluate breakdown maintenance operations using simulation.

3

Metrics for measuring breakdown maintenance operations

Analogous to concept of lead time in manufacturing, the concept of Mean Maintenance Lead Time (MMLT) is being suggested for breakdown maintenance measurement. MMLT can be defined as the time between recognising the need for maintenance on a particular piece of equipment to the actual performance of such maintenance and the subsequent production of good product. MMLT takes the maintenance activities into account from an operational level. Unlike the existing indicators for measuring the maintenance performance, it does not examine the impact of poor or lack of maintenance

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strategy on the manufacturing front; instead it acts as a powerful tool to measure the breakdown maintenance activities themselves. The delineation of MMLT is shown in Figure 1. Figure 1

Delineation of MMLT

MMLT is given by the following equation. MMLT = MTTO + MTTR + MTTY where MTTO: Mean time to organise (Time required to coordinate tasks to initiate the maintenance repairs) MTTR: Mean time to repair (Time required to repair and maintain of the equipment) MTTY: Mean time to yield (Time required to yield a good part after maintenance). Within this MMLT delineation, the only time component that adds value to the breakdown maintenance is MTTR, since this is the only time component that involves the actual performance of the maintenance repair task. The other time components MTTO and MTTY are non-value added time. Value added time and non-value added time are given by, Value added time = MTTR Non-value added time = MTTO + MTTY.

4

Research methodology

The methodology that will be utilised for developing a Maintenance Value Stream Map (MVSM) is categorised into two distinct phases. The first phase involves developing a framework for MVSM. This framework includes all the necessary symbols that will be employed for the mapping process. These symbols are also categorised to the corresponding MMLT category. The second phase involves establishing a step by step standard mapping process by which maintenance practitioners in industry could baseline maintenance activities and form a current state map of the breakdown maintenance function. This current state map will also contain the results of the evaluated breakdown maintenance operations in terms of MMLT, MTTO, MTTR, MTTY, Value added time and Non-Value added time.

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Framework

In this first phase, a general framework (as shown in Table 1) is introduced for developing the MVSM. Within this framework there are seven categories that are utilised

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to represent the actual breakdown maintenance function. These are a combination of newly developed symbols as well as symbols adopted from big picture mapping (Rother and Shook, 1999). Definitions for each of the seven categories are provided in Table 1. Table 1

Framework (see online version for colours)

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Table 1

Framework (see online version for colours) (continued)

[5]: Denotes symbol adopted from big picture mapping. Source: Rother and Shook (1999)

6

Mapping process

This phase describes the mapping process involved in developing MVSM. The process is presented in the seven steps provided below: Step 1: Involves the following tasks associated with the equipment that has been shut down as presented in Figure 2. •

Place the ‘Equipment breakdown’ symbol at the top left hand corner of the MVSM page.

•

Write the equipment name at the top rectangular box.

Developing a value stream map to evaluate breakdown Figure 2

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Step 1 of MVSM (see online version for colours)

Step 2: Involves identifying the boundary of the process. Specifically this involves identifying the first process after a machine is shut down and the last process when a first good part is produced. •

The first process is associated with symbol ‘communicate the problem’. Place this symbol to the left hand side of the page under the ‘equipment breakdown’ symbol.

•

The last process is associated with symbol ‘finish work order’. Place the finish work order symbol to extreme right hand side of the page such that it is aligned with ‘communicate the problem’ symbol as shown in Figure 3.

Figure 3

Step 2 of MVSM (see online version for colours)

Step 3: Involves identifying the intermediate processes between the first process ‘communicate the problem’ and the last process ‘Finish work order’. •

Place all the intermediate process symbols namely, ‘Identify the problem’, ‘Identify the resources’, ‘Locate the resources’, ‘Generate work order’, ‘Repair equipment’ and ‘Run the equipment’ right next to each other according to the process sequence as shown in Figure 4.

Figure 4

Step 3 of MVSM (see online version for colours)

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Step 4: Involves recording the information associated with each maintenance process. •

Place the data box symbol underneath each process.

•

Enter the process time value for each process in the data box. Arbitrary process time values are assigned for the purpose of illustration as shown in Figure 5.

Figure 5

Step 4 of MVSM. Since the ‘Finish work order’ process does not contribute to MMLT, its process time is not recorded (see online version for colours)

Step 5: Involves recording the delay time between maintenance processes. •

Place the delay symbol between all the processes.

•

Write the appropriate numbers inside the delay symbol to indicate the type of delay. If there are two or more types of delays associated with a process, write all the numbers corresponding to the delay type separated by comma as shown in Figure 6.

•

Write the delay time below the delay symbol. Arbitrary delay time values are assigned for the purpose of illustration.

Figure 6

Step 5 of MVSM (see online version for colours)

Step 6: Involves creating the physical flow and information flow for maintenance processes. •

Connect the ‘equipment break down’ symbol with the first activity in the value stream using the down arrow symbol.

•

Connect all the processes with physical flow (dashed lines) and information flow (continuous line) arrows as shown in Figure 7.

Developing a value stream map to evaluate breakdown Figure 7

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Step 6 of MVSM (see online version for colours)

Step 7: Involves the following tasks associated with the calculation of MMLT, MTTO, MTTR, MTTY, Value added time and Non-value added time. •

Draw the time line at the bottom of the page.

•

Write down all the non-value added times at the top of the time line and all the value added times at the bottom of the time line as shown in Figure 8.

•

Calculate MTTO by summing up all the delay and process time values before ‘Run the equipment’ process.

•

Calculate MTTR as the process time of ‘Run the equipment’ process.

•

Calculate MTTY by summing up all the delay and process time values after ‘Run the equipment’ process.

•

Finally, calculate MMLT, Value added time and Non-value added time using the formula provided in Section 3 of this paper.

Figure 8

7

Step 7 of MVSM (see online version for colours)

Case study

Tungsten powder production process as shown in Figure 9 was used as a case study to demonstrate the practical application of the proposed MVSM. The raw material used for the powder production is tungsten oxide powder. This powder is fed in to the furnace, which converts tungsten oxide into tungsten. The tungsten powder obtained from the furnace is sent to lab (Inspection 1) for determining the grain size of the powder. Various different grain sizes of tungsten powder are blended in the blender to get the

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appropriate mix of grain size. The tungsten powder from the blender is then sent to the lab (Inspection 2) for a final inspection of the grain size. The inspected tungsten powder is then stored in drums for shipping. Figure 9

Tungsten powder production process (see online version for colours)

The bottleneck process within this production process is the furnace operation. Since the downtime of the furnace will impact the production the most, it was decided to develop a MVSM for the furnace to evaluate breakdown maintenance operation of the furnace. Using the framework symbols and the seven step standard mapping process, the MVSM developed for the furnace is shown in Figure 10. The subsequent results obtained from the MVSM are shown in Table 2. The result suggests very high MMLT; this is predominantly due to the high amount of non-value added activities within the breakdown maintenance operations. The majority of non-value added activity is due to the delay between ‘Locate the resources’ and ‘Generate work order’ processes. This delay is caused due to the unavailability of tools and parts to issue the work order to perform the necessary maintenance task. This clearly indicates that the focus point of the maintenance personnel should be to have a proper mechanism such as a supermarket pull system (an inventory control strategy of lean) as this will ensure the availability of parts and tools at all times and will significantly stream line the breakdown maintenance activities, thereby enhancing the availability of the furnace. Figure 10

MVSM of furnace (see online version for colours)

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Developing a value stream map to evaluate breakdown Table 2

MVSM results

Metrics

Results (min)

MMLT

2780

MTTO

2497

MTTR

150

MTTY Non-value added time Value added time

8

133 2630 150

Conclusion

This paper systematically e...