- A value stream map shows material and information flow for one product family, with data at each step and the waiting between steps.
- The waiting between boxes is the finding. Most maps show under 5% of total time as value-added.
- Map the current state by walking it, not from memory or from the ERP.
Everyone already knows the process steps. What nobody can see without the map is that the product spends three days between two operations that each take four minutes. The timeline strip at the bottom is the whole point of the exercise.
Pick a scope you can finish
One product family, one facility, door to door. Attempting a whole business produces a map nobody finishes and nobody uses. A family is a group of products that pass through broadly the same steps.
What to record at each process box
- Cycle time, measured not estimated.
- Changeover time.
- Uptime or availability.
- Number of operators.
- Batch or transfer size.
- Inventory sitting before the step, in units and in days of demand.
Draw the information flow too
Half of most value streams is how the work is triggered: forecasts, schedules, expediting calls, the daily meeting where priorities change. Mapping only material flow misses why the queues form, which is usually a scheduling behaviour rather than a capacity limit.
Reading the finished map
- Compare total lead time against total value-added time. The ratio is usually startling.
- Find the largest inventory piles; they sit in front of the real constraints.
- Look for where the schedule is injected at multiple points, which produces conflicting priorities.
- Identify the single step whose improvement would shorten the timeline most, and start there.
Current state, then future state
Map what happens now, including the workarounds. A map of the official process is worthless. Only once the current state is honest is a future state worth drawing, and it should be an achievable next state, six to twelve months out, not an ideal.