In a nutshell, Value Stream Mapping is the schematic description of physical and information flow of a process or a value chain. It helps understanding the current situation and analyzing the causes of issues and limitations. VSM is followed by a design of the desired future state, called Value Stream Design (VSD). The third implicit part of a VSM-VSD is the action plan, made of the necessary actions for changing from current situation to the desired future state.
VSM is therefore an excellent trigger for continuous improvement and used as such in Lean initiatives.
What lean enthusiasts using VSM look for is a smooth, fast and direct flow from customers’ needs or desires to customers satisfaction, using only the very necessary resources. This requires the process supporting the flow to be as free of wastes as possible.
It seems reasonable then to (re)visit the process and hunt down any waste in order to improve the flow.
Doing so is making an assumption, mostly unspoken and even unconscious, that the actual process is really useful and needs/deserves improvement.
Yet most of the lean enthusiast take a shortcut on the scientific thinking promoted by Lean, jumping too fast on Doing (read Mapping in this case) without giving enough time, if any, on Planning.
The Plan phase of the PDCA is meant to pose a hypothesis and to design an experiment carried out during the Do phase and assessed for validation or invalidation in the Check phase.
It therefore happens, more often than believed, that an unnecessary process gets attention, time and resources allocated for improvement when what was is really needed is simply to get rid of the whole process!
How can a process be useless?
It is common to setup a process in order to overcome a problem and literally forget to remove it once the problem is solved. Many processes are cluttered with sub-processes and procedures once created to bypass or overcome a problem that remain in place, consuming resources for absolutely no value creation.
In order to avoid such kind of embarrassing creation of muda (Value Stream Mapping an unnecessary process), each process candidate for a VSM should first be analysed for its purpose: what is the goal of this process? what problem this process is supposed to solve?
If there is no good reason for the process to exist, no need to map it, go for discarding it. (Note: good reasons may include “mandatory by regulation”)
For another variation on this subject, you may like to read VSM Pitfall: unnecessary process