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CLT10: Value stream mapping and process analysis

CLT10 · Work through your exam, one topic at a time.

All guide sections

Value stream mapping and process analysis

Value stream mapping and process analysis examines whether you can see material and information flow end to end, quantify delay, and design a future state with a plan. Questions often ask you to calculate lead time, takt, and value-added ratio, or to select the next kaizen.

Core rules

  • A current-state map shows customer demand, information flow, process boxes (cycle time, changeover, uptime, batch), inventory triangles, and the timeline. Walk the actual flow; do not map from memory.
  • Lead time is the sum of inventory days plus processing time, not just processing. Value-added ratio = value-added time / total lead time; use consistent time units.
  • Mark kaizen bursts only where evidence shows a constraint or delay. The future state should be driven by takt, continuous flow where possible, pull where flow is impossible, and heijunka.
  • Process analysis separates value-added, necessary non-value-added, and pure waste. Check capacity against demand before redesigning flow.
  • A future-state map without an implementation plan, owners, and dates is a poster, not a plan.

Worked example

Demand is 150 units/day over one 450-minute shift. Three inventory triangles hold 300, 150, and 450 units. Inventory days are 300/150 = 2.0, 150/150 = 1.0, and 450/150 = 3.0, totaling 6.0 days. Processing time across the three processes is 9 minutes. Lead time = 6 days × 450 minutes + 9 minutes = 2,709 minutes. Value-added ratio = 9 / 2,709 = 0.33%. The reasoning matters: inventory dominates lead time, so cutting batch sizes or introducing FIFO/pull between processes will reduce delay more than speeding a 3-minute operation.

Traps

Do not average inventory days when demand differs by product family; calculate per family. Do not use annual demand when takt uses daily available time. Do not omit information flow, changeover, or uptime. Do not set a future state that assumes perfect uptime or zero variation.

Key points

  • Map actual material and information flow, not memory.
  • Lead time includes inventory wait plus processing; VA ratio uses consistent units.
  • Design future state from takt, flow, pull, and heijunka.
  • A future-state map needs owners, dates, and kaizen actions.