TMCnet News

A value stream map in motion [Industrial Engineer]
[May 20, 2013]

A value stream map in motion [Industrial Engineer]

(Industrial Engineer Via Acquire Media NewsEdge) Simulation makes static tool dynamic, increasing its usefulness A PICTURE IS WORTH A THOUSAND words, and a movie is worth a thousand pictures. The lines that follow are proof.

Imagine this short story: A happy family is smiling elegantly and showing their crystal white teeth as they pose for you. Say cheese! Click! The shutter of your Polaroid camera opens and closes. The developing image automatically outputs. Here is your instant photo of the family gathering.

Twenty years later, you are sitting by the piano where the photo was taken. You look at the photo and try to remember the details of the gathering. Everyone looks happy in the photo, but was everyone really happy Was it just an instant in which everyone was forced to smile before everything returned to normal, or was it a genuinely good day Digging out the video clips of the same event showed the group forming and provided an enriched narrative of that frozen moment in time captured by the photograph.

There is a parallel between this situation with the still photo and assessing the current state of a production system. It all depends on the precise time that the study was undertaken, which could be affected by the complexity and dynamics of the system, i.e., how many states the system can be in and how fast it changes from one state to the other.

This is what happens when you try and map a system using a value stream map, a static paper-and-pencil tool that is well-established in lean manufacturing. You can map a system using data you have gathered once, or you can be more accurate and collect the data more than once, average what you have gathered and use it as valid data on a value stream map.

This article is about making value stream maps more dynamic by putting them into motion through the benefits of simulation. The article introduces VSMSx - a tool that can develop numerous models of value stream maps. It explains the strengths and weaknesses of value stream maps and argues that these weaknesses can be overcome by using VSMSx or other tools you might develop that will apply simulation to the static maps.

Importance Value stream mapping is an integral part of lean manufacturing that identifies the activities that add value. They can let you know which activities the customer is willing to pay for and which ones they won't. It is a powerful tool used mainly for visualizing a system, whether this system produces a product or supplies a service. Value stream maps emerged in the 1990s. Since then they have been used in a range of industries, including production systems, banks, healthcare, maintenance programs, product development and distribution.

The unique feature of value stream maps is that they map both the flow of the product/service and the flow of information that triggers the flow of product/service. In production systems, information flow could relate to demand forecasting, customer requirements, checking inventory levels, orders to suppliers, and orders to the shop floor for the manufacturing of parts. Material flow is the sequence of processes for manufacturing a product/service from when the organization receives materials from suppliers into its stock all the way through the manufacturing processes and dispatch and shipping to customers Seeing how the information flow and material flow are linked together helps industrial engineers visualize how a production system works from when a customer initiates the order until when the order is fulfilled by delivery. Value stream maps show the key elements of a production system and how these elements interact with each other. A traditional value stream map includes, but is not limited to, customers, suppliers, production control, inventories, processes, mode of production (push/ pull) and shipment trucks (intervals and quantity ordered).

These elements are sketched using universal symbols so the value stream map can be understood easily by anyone who reads it: A process is a box, inventory is a triangle with the letter "I," and a shipping truck is a truck. Alterations to how the symbols look are common, but invariably they can be understood readily without the need for a key.

The essence of lean manufacturing is the elimination of wastes and the removal of activities that don't add value to the customer. Value stream maps focus on the issue of adding value and highlight, on a timeline, whether activities add value or not. The timeline indicates how long each activity takes and so shows the ratio of value-adding activities as a proportion of the total production time. This measure is called the value-added ratio and is a strong measure of the leanness of the system.

Knowing the non-value-adding activities is the first step in identifying a system's wastes. The map also indicates how long a product spends in inventory, the time needed to change over from one product to another and the distance traveled from one process to the next. Value stream maps not only identity the wastes in a system but also their sources, which is why they are highly regarded by managers as the starting point for system improvement plans.

Drawbacks The problem with value stream maps is that they are static representations and capture the state of a system at the single momentwhen the map was drawn. They completely neglect time and its effects. Parts of a system might be idle or overloaded for specific reasons; therefore, depending on static value stream maps to analyze a system in depth does not produce a reliable outcome.

Value stream maps are not only static and unchanging over time, they also are dangerously fixed. They show the inventory holding times as equal for each of the products manufactured on a particular production line. They also show that processing times arc the same for all workers, even though times will vary from one individual to another. Change is constant, but value stream maps don't show changes in a system's variables or sense delays in suppliers' shipments and their effect on the level of finished goods inventory. Value stream maps don't provide the values of utilization in the system, the level of arrears to customers, or the level of throughput through the production lines.

The relationships between variables in a traditional value stream map are linear - a situation that is not true in an open system, such as a production system where each variable directly and indirectly affects other variables. It is critically important that industrial engineers understand the complex interactions between variables in a system, as a change in one variable would affect the behavior of the whole system.

So while traditional value stream maps are powerful in visualizing whole systems, they don't give reliable measures of how systems actually are performing.

Simulation To help managers analyze systems in depth using value stream maps, organizations need to introduce simulation to make the static maps dynamic. Combining value stream maps with simulation would be a powerful analytic tool that would support decision makers who want to predict the impact of proposed improvements to a system before implementation. After being modeled and simulated, a value stream map no longer would be a snapshot of the system at a point in time. Instead, it would become the movie that is worth a thousand pictures.

Simulation would add the dimension of time to a value stream map and would overcome its static nature. By reflecting the time factor, changes in the state of the system over time would be understood. Simulation would show how inventory levels fluctuate, when they fluctuate and, most importantly, why they fluctuate. It would show not just the average utilization of equipment but high and low utilization patterns. It also would show the effects and consequences of delays in transmitting information.

A major problem in any production system is variability, including inconsistent deliveries by suppliers, variations in processing times between workers or machine downtimes. Simulation would reflect variability better than the once deterministic values used for traditional value stream mapping.

A major benefit of modeling and simulating value stream maps would be the ability to analyze the effect of both minor and major changes to a system. Decision makers could see the effect on throughput of adding a new machine or compare a preventive maintenance program with a corrective maintenance program. Major strategic changes might include changing the inventory rules, altering the production mode from push to pull, changing the facility layout or shifting to a single supplier. These are critical decisions that would consume vast resources. Thus, they need to be assessed carefully prior to actual implementation.

The need for a tool, not a model A tool that can simulate multiple models of different states of value stream maps is needed to support suggested future states of the system and to assess different improvement scenarios. Reusability within the simulation permits the building of numerous models, with each model representing a phase in a complete lean transformation project.

Value stream maps are generic in nature and can be used in any industry regardless of the nature of the product/ service. Building on this powerful feature to develop a tool that builds simulation models for different industries would be an appropriate approach to integrating simulation with value stream maps. Rather than having models that are industry specific and lack the flexibility to be altered, a more convenient way of building simulation models of value stream maps would be a tool that has the ability to generate different models easily. This tool would integrate the power of simulation to overcome the drawbacks of value stream maps and pave the way for more successful lean implementations.

VSMSx, a value stream map simulator using ExtendSim, was developed as part of successful research for a Master of Science degree in the Department of Industrial and Management Engineering at the Arab Academy for Science and Technology in Alexandria, Egypt. It's a generic multiple-use tool for building simulation models of value stream maps. It is supported by a database for inputs and outputs that can be manipulated remotely.

Although this tool was developed with ExtendSim Suite version 7.0.6, organizations and research institutions could devise value stream map simulators using other software packages as well. Just make sure to include the necessary infrastructure such as a library, drag-and-drop functionality and a database.

The VSMSx has a library of process or inventory building blocks, which represent and look identical to the symbols used in traditional value stream maps. These building blocks can be assembled into a model that interacts with other blocks in the simulation environment.

Blocks can be dragged and dropped from the library into the simulation environment and connected in sequence to represent the value stream map being modeled.

A complete model developed using VSMSx would look identical to a traditional value stream map developed on paper. This preserves the communication language understood by users of traditional value stream maps.

The value stream map of the system is underpinned by a database comprising simple tables for data input and output. Data inputs collected from the system can be entered so that after the model is run the outputs can be reported to the database. The database manipulation is as simple as using an Excel table. Although VSMSx is a powerful tool, it requires only average computer skills to operate it.

The advanced processing power achieved by incorporating simulation with paper-and-pencil value stream maps enables a number of key performance measures to be extracted, including utilization of workers, utilization of processes, overall equipment efficiency, late deliveries, throughput, inventory fluctuation levels and time spent as work-in-process. Thus, managers and decision makers can see the impact of a lean transformation prior to implementation by predicting how a system would behave. It literally puts a value stream map in motion.

The future of value stream simulation VSMSx or other value stream simulators are just one element in a potential suite of strategic system analysis tools. It uses component-based modeling and provides a useful foundation for further research.

Component-based modeling divides a whole system simulation into a number of smaller simulation models that can be modeled individually as self-contained, reusable and replaceable blocks. Component-based modeling allows the remote alteration of input data and values without the need for the user to learn a new modeling language. Input and output databases allow the average computer-literate person to build and run any model and output numerically and graphically. The level of reusability offered by component-based modeling is extremely useful in relation to building value stream maps - each component can incorporate a number of complex models within it.

The way forward with this research would be to broaden the scope of the tool to incorporate the dynamics of the customers, suppliers and of the production system itself.

SPACE COLONIES AND SIMULATION Simulation doesn't have to involve just using computers.

In March, MSN New Zealand reported that a group of scientists are using a base in the Utah desert to simulate life on Mars. The research is backed by The Mars Society, a nonprofit that aims to send humans to the red planet. According to the researchers, the Utah desert's Mars-like terrain simulates working conditions on the fourth planet from the sun.

The website reported that scientists, students and enthusiasts are working to develop field tactics and study the terrain while wearing simulated spacesuits.

According to The Mars Society, the Mars Desert Research Station allows scientists to launch programs of long-duration geology and biology field exploration conducted much like they would be conducted on Mars. The red planet has all the elements needed to support life, so colonization there is a prerequisite to finding out if humanity "can expand from its globe of origin to enjoy the open frontiers and unlimited prospects available to multiplanet spacefaring species." Mohamed A. Shararah is a Ph.D. student researching the designing of high-performance socio-technical systems and management of enterprise transformation in the Centre for Lean Enterprise, Applications and Research (CLEAR) in the CardiffSchool of Management in the United Kingdom. He has a B.S. in industrial and management engineering and an M.S. in lean manufacturing. He presented at the HE Engineering Lean and Six Sigma Conference 2011 and has worked as a part-time consultant for the Welsh Lean Management Institute.

(c) 2013 Institute of Industrial Engineers-Publisher

[ Back To's Homepage ]