Value stream mapping
Mapping flow, not hierarchy
A value stream is the sequence of activities an organization performs to create and deliver value to a consumer, from a triggering demand to the point value is delivered. Value stream mapping (VSM) is a Lean technique that visualises that flow so waste and delay become visible.
Approach: define scope and boundaries and identify the trigger and the consumer; select the value stream that matters; map the current state using real data gathered by walking the flow; measure each step - process time (time actually working), wait or queue time, lead time (total elapsed) and percentage complete and accurate (%C&A) at hand-offs; analyse to classify steps as value-adding, necessary non-value-adding, or waste; map the future state; implement; then repeat.
VSM's power comes from the timeline ladder beneath the process boxes, which exposes the ratio of wait time to work time. Typical symbols include process boxes, inventory or wait triangles, external sources and sinks, information flows and push/pull arrows.
Traps: mapping the organizational chart or technology architecture instead of the flow of work; confusing lead time with process time; omitting rework and hand-off failure (%C&A); trying to map everything at once rather than one value stream; producing a beautiful current-state map and never building the future state.
Rule of thumb: start at the customer and work backwards to the trigger; if a step neither makes the outcome more valuable nor more likely, ask why it exists.