After my previous blog publication about “How to depict the Inventory or the Process Cycle Times on VSM when those are in parallel? The right way….” http://alexsibaja.blogspot.mx/2014/06/how-to-depict-inventory-or-process.html .
I have received some question; in regards of “what’s the best way to depict a process that has many different flows? And how calculate the Lead Time?” Obviously without any use of VSM Software.
First of all; I always teach to teams the manual method; if you have the capital to buy VSM software and it’s really needed; buy it and used it.
I understand that in many books about VSM and Lean Manufacturing; there is the classic example of VSM current state with just one Straight Flow, but we need understand that the authors of those books (very good books by the way) needs to give a clear and easy example; to their readers to understand the “Basic Concepts” of how to create and understand the VSM Current state and see the opportunities like Waste, Non – Value –Added, Overburden and Unevenness.
Even on some Lean Trainings (some of them very expensive by the way) always shown a VSM Current State easy and straight flow, but again it’s for academic purpose.
The problem starts, when you return to your company, to see the production floor, and you just not have any Idea where to start, because the real process is very complicated and when you compare it with your training courses notes (VSM example) it's just doesn't match.
On real life, when you are analyzing a company, the processes may be very bad with a lot cruises between them, and different process flows that goes and comes; and you could make the mistake to depict the Current process as in the books or in the Trainings (just one straight Flow) and not reflecting the reality; that at the end is the purpose of the VSM current state, to show the problems.
That’s why I always recommend depict the VSM as one Instantaneous Picture; as its is; that reflects all the process flows, mix of products, the comes and goes of products and flows etc. as much as possible. I also recommend to my teams; to read many books from different authors doesn't matter are from same subject; the authors experience and the examples can be very different from each other’s.
Here one example of VSM current state, that is not straight, please see, how it is draw.
Obviously; now is more complicated calculate the Lead Time right? But there is an easy way to do it:
Lead Time = [(Total WIP pcs X Takt Time)]+ [Total Cycle Time]
And must important, practice on real life, forget about, games or simulations, go to Genba and see real flow, go and see for your self to thoroughly understand the situation (Genchi Genbutsu).
You can at pictures to VSM if you want.
Then all you need to do is creates the Future VSM, remember; there is not just one Future State, there are phases.