A value stream is the sequence of activities and information required to deliver a product or service to a customer. Value-stream mapping (VSM) visualizes that end-to-end flow so teams can see delays, inventories, queues, information triggers and handoffs that are difficult to understand from departmental KPIs alone.
Process Map vs Value-Stream Map
| Process map | Value-stream map |
|---|---|
| Shows process steps and decisions | Shows material and information flow across the value stream |
| Useful for detailed workflow analysis | Useful for end-to-end flow, delay and inventory analysis |
| Can focus on one department | Usually crosses functions and suppliers/customers |
How to Build a Value-Stream Map
- Select the product/service family. Avoid mapping everything at once.
- Define customer demand. Understand volume, mix, frequency and service requirement.
- Walk the current process. Capture actual flow rather than the documented ideal.
- Record process data. Cycle time, wait time, WIP, batch size, uptime, staffing and information trigger.
- Calculate end-to-end lead time. Distinguish active processing from waiting.
- Design the future state. Remove unnecessary steps, reduce queues, improve flow and introduce pull where appropriate.
- Create an implementation plan. Assign actions, owners and measurable targets.
Supply-Chain Example
A purchase requisition may take only 20 minutes to review, but wait two days for approval, one day for buyer assignment and three days for supplier quotation. A traditional task view sees less than an hour of work; a value-stream view sees nearly six days of elapsed time. The improvement opportunity is therefore usually in the queues and handoffs, not the typing speed.
Useful Metrics
- Total lead time
- Value-added / processing time
- Waiting time
- WIP or queue size
- First-pass yield
- Batch size
- Handoff count
Use VSM with TIMWOODS to identify waste and with process mapping when detailed step-level analysis is required.
Interview Question
Question: Why can a process with low task time still have a long customer lead time?
Answer: Because most elapsed time may be waiting between activities. VSM makes that non-processing time visible so improvement can target queues, batch delays and handoffs.
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