VSM Quick Reference (symbols, lead time, takt, wastes, quick checklist)

VSM Quick Reference

Use this single-page guide during a value-stream mapping session to keep the team aligned on symbols, essential data to capture, quick calculations, and practical checks for common wastes.

1. Common Symbols (legend)

• Process box — operation or work center (capture cycle time, uptime, operators, changeover)
• Inventory / Waiting triangle — material or WIP between processes
• Shipment / Supplier icon — external supplier or customer
• Information flow arrow — push/pull signals, schedules, kanban
• Data box — numeric data for a process (see standard fields below)
• Kanban — card/authorization for replenishment
• Supermarket — controlled inventory buffer
• Timeline — separate process time (PT) and lead/wait time (LT) rows

2. Standard data to capture in each process box

• Process name / brief description
• Cycle time (CT) — time to produce one unit (seconds/minutes)
• Changeover time (SMED) — minutes to switch product
• Uptime / availability (%) — percent of scheduled time process is available
• Batch size or run quantity
• Number of operators
• Yield / first-pass quality (%)
• Average WIP between this and next step

3. Quick formulas (common & reliable)

1. Available time / shift = Shift length − breaks − planned meetings (express in minutes or seconds)

   Example: 8 hr shift = 480 min − 30 min breaks = 450 min = 27,000 sec

2. Takt time = Available time / Customer demand (in same time units)

   Example: 27,000 sec / 900 pieces per day = 30 sec per piece

3. Process cycle time (CT) = measured time to produce one unit at that step (average)
4. Total Lead Time (LT) = Sum of all process times + Sum of all wait times + transport

   When mapping, place process times on the Process Time row and waits/inventory-converted-times on the Lead Time row.

5. Lead Time Efficiency = (Total Process Time / Total Lead Time) × 100%

   Higher % = more of lead time is value-adding. Typical inefficient value streams often show < 10%.

6. Throughput or Capacity per Hour = 3600 sec / CT (if CT in sec)

4. Example lead time calculation (mini)

Three processes: A CT=20s, B CT=40s, C CT=30s. Wait times: between A–B = 2 hrs (7,200s), B–C = 1 hr (3,600s). Available units = 1 unit per process timescale.

Total Process Time = 20 + 40 + 30 = 90s. Total Wait Time = 7,200 + 3,600 = 10,800s. Total Lead Time = 90 + 10,800 = 10,890s (~3.03 hours). Lead Time Efficiency = 90 / 10,890 = 0.8%.

5. The 8 wastes (checklist + spotting prompts)

• Transport — unnecessary movement of materials (look for back-and-forth flows)
• Inventory — excess WIP or finished goods (large inventory triangles, long wait times)
• Motion — unnecessary worker movement (operators reaching, walking)
• Waiting — queues, idle time between steps (long waits on timeline)
• Overproduction — producing ahead of demand or big batches (big runs, supermarkets hiding problems)
• Over-processing — doing more work than customer needs (extra inspections, redundant steps)
• Defects / Rework — scrap or rework loops (notes on yield %, rework steps)
• Under-utilized talent — not using people’s skills (repetitive manual tasks that could be improved)

6. Quick mapping rules / tips

• Start with the customer and work upstream. Map material & information flow in parallel.
• Use real, time-based observations for CT and waits. Ask “how long does it actually take?”
• Convert inventory to time for the timeline (Inventory / daily demand → days of supply → seconds/minutes)
• Prefer averages for CT but capture variation (min/max or observed % downtime) where possible.
• Be explicit about assumptions (shift length, scrap rates, available hours) and capture them on the map.

7. Common workshop pitfalls

• Collecting only estimates — missing measured cycle/wait times wastes follow-up work.
• Local optimization — fixing a single step without checking downstream/upstream effects (see domain Mal-Hunger).
• Ignoring uptime and changeover — gives false capacity impressions.
• Missing quality/yield data — rework often hidden in process times or separate flows.

8. Quick next-step checklist after mapping

1. Calculate takt time and compare to cycle times to identify immediate bottlenecks.
2. Compute lead time and lead time efficiency to prioritize waste-reduction targets.
3. List top 3 improvement experiments (one upstream bottleneck, one queue reduction, one quality action).
4. Define measurable metrics and owners (e.g., reduce lead time by X% in Y months).
5. Plan a short PDCA/Kaizen to test a change and re-measure CT and LT.

9. Fast reference conversions

• Minutes to seconds: × 60
• Hours to seconds: × 3,600
• Inventory days = Inventory units / daily demand

Keep this sheet handy during mapping: Capture measured CT, WIP, uptime, and yield for each process, convert inventory to time for the timeline, compute takt and lead time efficiency, and use the wastes checklist to spark improvement experiments.