It is frequently proposed that value stream mapping  should be done entirely with paper and pencil.  This might be acceptable for current state mapping of simple systems.  For more complex systems, it is worthwhile asking, 'Do we really know that our map is accurate?'  Furthermore, there is a real risk that poor choices will be made when developing the future state map of any system, and that implementers will work hard on problems that fail to deliver the expected results.  What looks good on paper may not be what is really required.  Again, for simple value streams, it is possible to consider a variety of alternatives, but increasing complexity makes this a risky task.

READ THE BOOK ON VALUE STREAM MAPPING

To consider alternatives, and discover their advantages and disadvantages, simulation-modeling software (SMS) can be a great help.  While traditional VSM describes work centers and inventory statically, SMS uses statistical characterizations.  Capable of producing typical performance data, SMS can thus show the amount of variation at each stage of production, and in the overall system.  SMS also has the ability to test the system for the optimal configuration with respect to a given performance measure or set of measures.  This means that selecting, for example, the required reduction in setup time, or cycle time for a cell, is not guess work.

Simulation-Based Value Stream Mapping Workshop

The purpose of the workshop is to explore the current state of the production system, and develop scenarios for an improved state, using lean manufacturing and other improvement techniques. The workshop selects and describes improvement activities that will transform the current state into the selected future state.

Simulation is a process mapping tool that activates the value stream as work goes through it. During this process, it gathers statistics on such aspects of performance as queue time, process time, production lead time, equipment and resource utilization rates, and the various costs associated with processing of orders. It captures the variation that takes place in the system over time, rather than just giving a snapshot. We use a visual interactive computer simulation modeling application to map the value stream and test improvement scenarios.

There are a number of benefits to our approach over traditional value stream mapping, whether paper or computerized flow chart based:

•  Modeling tests the understanding of the current state, since it demands that the performance measures of the model match those of the real system.

• Modeling often alerts team members to overlooked near-bottle necks, resource imbalances, and various kinds of hidden waste, and tends to produce more and better improvement ideas.

• Modeling allows for quick testing of several scenarios and comparison of competitive proposals, based on accepted measures of performance.

• Modeling allows for precise calculation of payback.

•  The “fun” component of simulation building and testing engages team members more than traditional static methods tend to.

• Where Visio flow charts exist, they can be instantly converted to an interactive model.

• Modeling speeds up development of revised value stream maps, and allows the value stream manager to test out and anticipate performance of intermediate steps on the way to the fully fledged future state.

• There is no need to purchase simulation software, as all models can be used via a free player. Dialog interfaces allow team members to explore selected aspects of the model independently.

The workshop allows the improvement team to work as a group, or in smaller breakout sessions, with the workshop leader, to build a simulation of the current state, and test performance under various conditions and order profiles. The group can consider a number of improvement suggestions, and compare results with highly realistic performance measures, and choose a future state that has a high probability of meeting company goals. The team also learns what is involved in transitioning to the future state, including equipment modification and replacement, training plans, systems modifications, and other organizational changes required to support the improvements. Detailed improvement plans, with all projects justified based on return on investment, leads to better implementation.

© Gardiner Nielsen Associates Inc.                                       

Last modified on November 21, 2008