The essential essence of Value Stream Mapping, (VSM) is to act as a tool to assist with planning and performance improvement. But there are two separate aspects to VSM, namely current state value stream mapping and future state value stream mapping.
The two are closely interlinked. If you only create a current state value stream map then you will have failed to address the transformation process (identified and set out in the future state map) that can lead to the improvements in processes that are integral to the purpose of value stream mapping.
The current state map looks essentially at what happens now (current) and the future looks at how things should be carried out, but there are more subtle differences than these but it is important to execute both forms of maps in order to facilitate real and tangible improvements.
Current State Value Stream Map
The current state value map enables the flow of processes to be identified and for those analysing the data to identify and then prioritise areas for improvement.
The value streams to be analysed have to be chosen carefully; they cannot all be done at once. The important element is to chart how material flows between different stages of production.
VSM always includes two flows – The material AND also the information flow. How is information disseminated and spread? What information do the machine operators have? This process should also include information that the operators have about what happens when something goes wrong. What information do they have about how to rectify any glitches in performance, or any defects?
When the current state value stream map is complete, there will be areas where improvements can be carried out. These improvements will be an integral part of the future state value stream map and are the basis for planning performance improvements.
Future State Value Stream Map
The future value stream map has as its main aim, the identification of improvements to the value stream that will lead to a shorter ‘lead’ time. In lean thinking this is the time taken from the raw materials being brought into the business, until the time they leave the facility destined for the customer.
Key to the development of a future value stream map are the following sections, thus enabling an efficient and effective map to be created:
Analysis of takt time as opposed to the cycle time. Takt time is the level of customer demand which is measured in terms of time. So you take the total number of working minutes that are in a working day and divide them by the average number of units that a customer requires per day. Cycle times are how frequently a part or component is completed by a specific process in the value stream. The takt times and cycle times should then be charted and compared for each process in the value stream. Takt should also be used within the pacesetter process which means that the actual performance and what is achieved needs to be compared to the planned performance. This is often summarised as being the stage of identifying the ‘reality versus planned’ performance.
When devising the future value stream the process boxes that are drawn up need to connect to the other process boxes immediately adjacent, so that there is a flow throughout the process.
Once the fundamentals of the current value stream map and the future map have been addressed, there is a strong need to ensure that the implementation of improvements is carried out in a structured and methodical fashion. Without someone driving forward the improvements, they are unlikely to happen and the improvements to performance will be negligible.