Value stream mapping at a glance
- What it maps: one product family, door to door, from the supplier's delivery to the customer's receipt, including the information that tells each step what to make.
- Where it came from: Toyota's "material and information flow" diagrams, published for Western managers by Mike Rother and John Shook in Learning to See (Lean Enterprise Institute, 1999).
- What it produces: a current-state map, a future-state map and an improvement plan to get from one to the other.
- Who does it: a small cross-functional team led by the person who owns the whole value stream, walking the actual process with pencil and paper.
- How often: usually once to set direction, then again when the future state is reached or every six to twelve months.
What does a value stream map show?
A value stream map shows three things on one page. Along the middle is the material flow: each process step with a data box (cycle time, changeover time, uptime, operators) and the inventory waiting between steps. Across the top is the information flow: how orders and schedules travel from the customer through production control to each step, and whether work is pushed or pulled. Along the bottom is a timeline that adds up waiting time against processing time.
The timeline is usually the shock. In most value streams the product is worked on for seconds or minutes and waits for days, so lead time is dominated by queues, not by work.
How do you create a value stream map?
- Choose one product family. Pick products that pass through similar steps and equipment. Mapping everything at once produces a wall chart nobody can act on.
- Name the value stream owner. One person accountable for the flow across departments, not for one department's efficiency.
- Walk the process from the customer end. Start at shipping and walk upstream, so every step is seen in terms of what the next customer needs.
- Collect real data at each step. Cycle time, changeover time, uptime, operators, shifts and batch sizes, timed at the gemba rather than copied from the ERP system.
- Count the inventory between steps. Convert each pile into days of demand by dividing it by the daily customer requirement.
- Draw the information flow. Show how orders arrive, how the schedule is set and which steps are told what to make.
- Draw the timeline and total it. Waiting time on the upper line, processing time on the lower line, with lead time and value-adding time at the end.
- Design the future state and the plan. Decide where flow, pull and a single scheduling point should go, then turn the gaps into a dated list of improvements with owners.
What are the value stream mapping symbols?
| Symbol | Meaning |
|---|---|
| Factory outline | Supplier or customer |
| Process box with data box | A process step and its cycle time, changeover, uptime and operators |
| Triangle with an I | Inventory waiting between steps, in units or days |
| Striped or bold arrow | Push: material moved on whether the next step needs it or not |
| Supermarket and circular arrow | Pull: the next step withdraws what it uses and the supplying step replaces it |
| Dashed or lightning arrow | Information flow, manual or electronic |
| Truck | Shipments in and out, with frequency |
| Kaizen burst | An improvement needed to reach the future state |
| Stepped line at the bottom | The timeline of waiting and processing time |
Exact shapes vary between textbooks and software; what matters is that the team uses one set consistently.
Value stream mapping example
A current-state value stream map: 13.5 days of lead time, 130 seconds of work.
A beverage plant maps one bottling line. Production control issues a weekly schedule to every step, so each one makes to plan and pushes its output on. Bottles and syrup sit for five days before mixing; finished cases wait four days for the daily truck. Add the inventory between steps and lead time is 13.5 days, while the four steps together work on a case for 130 seconds.
With two 450-minute shifts and demand of 1,200 cases a day, takt time is 45 seconds. Mixing runs at exactly 45 seconds with a 60-minute changeover and 85 per cent uptime, so it is the constraint, and filling's 78 per cent uptime is the next problem. The map points the team at changeover reduction in mixing, reliability in filling and replacing the weekly push schedule with a single pull signal at packing.
Current state vs future state
The current-state map shows how the value stream works today, warts and all. The future-state map shows how it should work in six to twelve months, usually following the guidelines in Learning to See:
- Produce to takt time.
- Use continuous flow wherever steps can be linked.
- Use supermarket pull where they cannot.
- Send the customer schedule to one pacemaker process only.
- Level the mix and volume of production over time.
The gap between the two maps becomes the improvement plan: a set of kaizen events, projects and daily improvements, each with an owner and date.
Value stream mapping vs process mapping
A process map (flowchart or swimlane) shows the sequence and decisions in one process in detail. A value stream map is a higher-level, door-to-door view of one product family that adds inventory, information flow and time. Teams often use VSM to find where the problem is, then a detailed process map, a fishbone diagram or root cause analysis to fix it.
Common value stream mapping mistakes
- Mapping in a meeting room from memory or system data instead of walking the process.
- Mapping too many products at once, so no clear flow emerges.
- Stopping at the current state, which describes the waste but changes nothing.
- Treating the map as a consultant's deliverable rather than the owner's plan.
- Never checking whether the future state was reached.
Value stream mapping in office and service work
VSM works anywhere work flows through steps: order to cash, purchase approvals, maintenance work orders, patient admissions or engineering changes. The data boxes record touch time, waiting time and the share of work that arrives complete and accurate, because rework loops are often the biggest waste in transactional value streams.
Value stream mapping and daily management
A value stream map sets the direction; daily management keeps it. The future-state measures, such as lead time, inventory days, changeover time and uptime at the constraint, belong on the tier boards of the areas in the value stream, so drift is seen each day rather than at the next mapping workshop. The improvement plan becomes tracked actions reviewed at Tier 2 and Tier 3 until the future state is reached, and then it is time to map again.