The Psychology of Quality and More
Value Stream Mapping
Value stream mapping is a tool that is often used in lean manufacturing but which can also be used in other areas of the company. Overall, it is a mapping of all the product actions that are required to go from raw material to delivery to the customer, done with the goal of identifying and eliminating all of the waste in this process.
The advantage of working with value streams is that it combines both ‘big picture’ that enables a broad understanding and widespread communication with detailed data that enables implementable actions to be planned.
A common diagram that is used for mapping value streams is shown below, and is sometimes called a ‘Learning to See’ map or a ‘Process Cartoon’.
Fig. 1. Value Mapping
This is clearly a complex diagram and needs some interpretation.
· The top row shows forecast and order flows. The main control process is shown between these. Suppliers and customers are shown as ‘factory’ pictures. Electronic flows may be shown as zig-zags (vs. direct lines as manual flows).
· The second row shows inputs and outputs from and to the top row. In the diagram it includes deliveries and requirements numbers. Note how already you can see differences between the Monday and Friday deliveries from suppliers and daily deliveries to customers. What if the customer sent a rush order on Tuesday and you ran out of coils of steel?
· The third row shows the main process. In this example it is Stamping, Welding, Assembly and Shipping. Around these are the Inventory triangles plus the inventory levels found (this may be a snapshot or may include a statistical distribution). Movement arrows with bars in indicate a ‘push’ (vs. white arrows which are ‘pull’. Other elements such as kanbans may also appear here.
· The fourth row shows timing data from each stage, with such as changeover time, cycle time and uptime. Other data may include such as shift patterns, operating equipment effectiveness (OEE) and time available.
· The fifth row shows value-adding time and non-value-adding time (and hence the opportunities for improvement).
Once the process is made visible, including the actual data about it, then this allows you to either find a focus on improve on key areas, such as bottlenecks, or redesign large parts of the process. The first diagram is often called a ‘Current State Diagram’ and the design for the improvement is called a ‘Future State Diagram’.
Maintaining this big picture view helps to ensure that improvements you make result in real savings or benefits to customers, as opposed to the apparent savings to which a tunnel-vision part-of-the-process change could lead.
This article first appeared in Quality World, the journal of the Institute for Quality Assurance
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