Visit Value Stream Mapping (VSM), or Value Chain Mapping (or Mapping material and information flows), is a visual analysis tool for the Lean Management. It provides a comprehensive representation of all stages (from customer order to delivery) required for a product or service to be created.
In-depth definition : Developed and popularized by Toyota, the objective of the VSM is to clearly show the Value added (VA) and, above all waste (Muda) and inefficiencies (irregularities, overloads) lurking in the process. It's the tool that transforms a simple process analysis into an analysis of’Operational Excellence strategic.
A VSM map shows two main flows:
- Physical Flow: Product movement (cycle time, waiting time, stock).
- The Information Flow : Signals that tell people and machines what to do (planning ERP, commands, instructions).
The VSM is always carried out in two stages: the Current State Map (Current State Map) to visualize problems, and the Future State Map (Future State Map) to define improvements (KAIZEN).
VSM Key Components
A standard VSM is built around two timelines to distinguish the useful from the useless, fundamental concepts for the Industrial Engineering :
1. The Upper Time Line (Physics)
It represents the stages in the transformation process (cutting, assembly, baking, etc.). Each stage is measured by KPI crucial :
- Cycle time (CT) : The time taken by the operator or machine to complete a unit.
- Changeover time (SET UP) : The time required to switch from one product to another (e.g. the SMED aims to reduce this time).
- TRS : Visit Synthetic yield equipment.
- Inventory : The level of stock (or WIP – Work In Process) between stages (major source of Muda).
2. The Lower Time Line (Delay)
It represents the flow of total time:
- Value-added time (VA Time) : The sum of the Cycle Times (CT) of all stages. This is the actual transformation time for which the customer is willing to pay.
- Non-Value-Added Time (NVA Time) : The sum of all waiting, transport and storage times. This is the Muda total.
- Lead Time : Total time from start to finish (VA Time + NVA Time).
The objective of VSM is to reduce the Crossing time by tackling the Time without added value, and increase’Flow efficiency (VA Time / Lead Time).
The VSM Process in Continuous Improvement
- Define Product Family : The analysis focuses on a group of products that share the same processing steps.
- Drawing the Current State: The KAIZEN (often in the field - Gemba) collects actual data and draws the flow, insisting on standard icons to represent stocks, lead times and information flows (systems ERP or Kanban).
- Designing the Future State: The team eliminates Mudas identified (usually targeting overproduction, inventories and expectations). It defines how the process will be driven from now on (moving from a Flux Poussé to a Pulled Flow).
- Plan the Action: The action plan (often based on the Pareto method of the greatest waste) is defined to move from the Current state to the Future state (Phase Plan from PDCA).
In conclusion, the VSM is the visual tool par excellence. It enables teams to see the whole system at a glance, and to move from detecting local problems to optimizing global flows, thus maximizing the efficiency of the system. ROI (Return on Investment) efforts to’Continuous Improvement.