Principle #2 of Toyota Way is: “Create a continuous process flow to bring problems to the surface.”
In the ideal state for any process, there is zero time for the product/service/work-in-process (WIP) to be spent between steps of a process, this means that there is zero waiting between steps, and as one step is completed it immediately flows into the next step with no stops.
Continuous flow features stability, continuity and doesn’t waste time. No time wasted on waiting between steps or different processes means time is being maximized for its capabilities.
Continuous flow is very hard to achieve, process steps are not generally balanced, and all process contain inherent waste activities and intermediate stocks which most of the times are not avoidable. When a company starts out to achieve continuous flow, many process problems will appear and come to the surface. The optimal process features continuous flow, and any problems that appears in your way from achieving continuous flow are problems that are now visible and can be solved.
By trying to force continuous flow on a process, the insulation goes away and the problems come to the surface – this means you have to attack those problems instead of ignoring them.
Example: A manufacturing manager thought about studying and analysing the process flow by using VSM (Value Stream Mapping) which is a lean-management tool that focus on describing the process flow including added and non-added value activities. By this study the manager could choose which activities created “waste” to the process and be able to eliminate them maintaining and boosting those activities which added value to the final product.
After the VSM was created by the manufacturing manager and his/her team they found different types of points to be studied: muda, muri and mura.
MUDA, waste, can be defined in eight types. These are: Defects, Overproduction, Waiting, Non-used Talent, Transport, Inventories, Motion and Excess processing.
There are numerous tools available to identify and remove waste from your process, which include Poke Yoke, Kanban, Takt Time, SMED and One-Piece flow.
MURI, overburden, can result from Mura, and from removing too much Muda (waste) from the process. When operators or machines are utilized for more than 100% to finish their task, they are overburdened. This means breakdowns when it comes to machines and absenteeism when it comes to employees. To optimize the use of machines and make sure they function properly, preventive and autonomous maintenance can be implemented. To prevent overworked employees, safety should be the focus of all process designs and all standard work initiatives.
MURA, unevenness, can be found in fluctuation in customer demand, process times per product or variation of cycle times for different operators. In production environments with low-volume, high product variation, flexibility is more important than in high-volume, low-product variation environments. When Mura is not reduced, one increases the possibility for Muri and therefore Muda. Mura can be reduced by creating openness in the supply chain, change product design and create standard work for all operators.
Muda is the direct obstacle of flow. There are 8 distinctive types of muda which all lead to waiting times, and therefore longer lead times in a process. Simply taking out the muda does not work. Usually, there is a reason why the muda is there and this reason often has to do with the other two enemies: muri and mura. This means the three enemies of Lean areinterrelated and should therefore be taken into account simultaneously.
The aforementioned VSM can be applied to manufacturing, service or any process company-related. By this study and the implementation of the reduction or elimination of mura, muri and muda, the process is cleaner and results in better operational results, reducing downtime and scrap, boosting yield and creating standardised operations.