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With value stream mapping, you are mapping the flow from raw material to the customer, including all value- and non-value-added processes. Mapping this flow highlights many improvement opportunities. However, value stream mapping is originally set up for high- and medium-volume environments. Mapping a product that is not made very often may sound illogical.
The main reason of value stream mapping is to improve the company processes and activities. So, before you even start with any mapping tool, you already described the main organizational problem and goal, and you decided that value stream mapping helps you to solve the problem. Thereafter, the first step is to understand the current situation of the organization. What activities belong to the overall process? Which bottlenecks do you see in the process and which one affects your main problem? To give an answer on these questions, you have to focus on the flow and the value of the entire stream. With value stream mapping you see obstacles and opportunities to improve the process flow.
Having a clear view of the obstacles and opportunities to improve the process flow in an organization which operates in a high mix, low volume environment.
A couple of suggestions for a future state map in high mix, low volume environments are to put in pull systems wherever possible (focusing on expensive inventories). Besides, work with customers that want to change their large quantity orders into smaller orders and therefore split delivery days (this will help to work closer to one-piece flows for example). And finally, focus on long changeover times, since this might happen more often in a high mix, low-volume environment. These are only three suggestions, and of course there are more. However, it is not possible to clarify all the differences between high volume and low volume environment.
A couple of strategies are recommended to use for value stream mapping in low-volume departments or businesses. First of all, it is important to decide on what you are going to base your value stream map, e.g. based on the following five:
1. Product families
2. High running parts. So, which parts (or products) go through production most often? Or said differently, high volume parts in the low volume environment.
3. A general value stream map for the basic processes you have, and a few total product cycle time lines (TPCT) for some of the higher volume parts.
4. Individual value stream maps for each high-value part number. In this case, we assume that each runner follows a different path or uses different materials.
5. Individual maps for critical components (or subassemblies).
Second, when you start mapping the future state
of value streams in high mix, low volume environments, it is important to focus
on the basic differences between high volume and low volume environments, such
as: shared processes – partly utilized processes, varying type of orders, size
of orders, the inability to calculate and plan based on takt time and so on.
There is a specific symbol that can be used for low-volume environments. It is
the symbol for shared processes, you see below.
This symbol is especially useful for low volume operations since you often have a process or machine that is shared among different product. When this is the case, it helps to show the percentage of capacity utilized by the value stream that you are mapping, as well as the total current percentage the process or machine is utilized by all products. These data clarifies if it is a bottleneck process/ machine. Imagine when the total utilization is 90% and the process or machine is utilized by many different products or value streams. This result in a many challenges such as planning and control. Therefore, visual management at shared processes and machines is critical to understand its status.