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See lean thinking in motion

This simulator lets you run both one-piece flow and batch production side by side — and watch in real time why lean manufacturers choose flow over batch every time.

It takes about 2 minutes to run through. By the end, you'll understand the mechanics behind lead time, WIP, and process cycle efficiency — not just the theory.

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Two systems, one goal

Both systems are making the same product, with the same number of steps and the same process times. The only difference is how units are grouped as they move through production.

One-Piece Flow — 1 unit moves at a time
→ step 1 → step 2 → step 3 →
Batch — entire group waits between steps
→ waits → step 1 → waits → step 2…
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What the metrics mean

The simulation tracks four core lean measurements. These are the same numbers your improvement team should be monitoring on the shop floor.

Lead Time

Total elapsed time from first unit entering the process to the last unit leaving. The lower the better.

PCE — Process Cycle Efficiency

Value-added time ÷ total lead time × 100. Most batch systems run at 5–30%. World-class flow systems hit 80%+.

WIP — Work in Progress

Units stuck inside the process at any moment. High WIP hides problems, consumes cash, and delays defect detection.

NVA — Non-Value-Added Time

Time the product spends waiting, queuing, or being transported. Customers don't pay for this — it's pure waste.

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Adjust the variables

Five sliders control the simulation. Changing them reveals different lean principles in action.

Batch Size

Bigger batches = longer lead time, more WIP, later defect detection. Try 20 vs 2 to feel the impact.

Queue / Wait Time

Set this to 0 and both systems converge. The queue is the enemy — not the process itself.

Process Steps

More steps amplify the batch penalty. Each added step multiplies how long the whole batch waits.

Units to Produce

Increase this to see how the completion gap between OPF and batch widens at scale.

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You're ready to run it

Hit ▶ Run and watch both systems go simultaneously. After the simulation completes, scroll down for a full breakdown of why the results differ — with real-world context.

Try these experiments after your first run:

Experiment 1

Set batch size to 16, queue to 5s. Watch WIP pile up and PCE collapse.

Experiment 2

Set queue time to 0. Notice both systems become identical — queues are the root cause.

Experiment 3

Max out process steps to 6 with a large batch. The batch lead time becomes extreme.

Experiment 4

Shrink batch size to 2. Notice how close it gets to one-piece flow performance.

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Interactive Learning Tool

One-Piece Flow vs
Batch Production

Watch units move through both production systems in real time. Adjust batch size, steps, and wait times — see lead time, WIP, and process cycle efficiency change instantly.

Live Animation VA vs NVA PCE Calculator 6 Lean Metrics
Lead Time
Start-to-finish elapsed time
Total time from when the first unit enters the process to when the last unit exits. Includes both value-added time and all waiting/queue time. Reducing lead time is a primary goal of lean.
PCE
% of time actually adding value
Process Cycle Efficiency = VA time ÷ Lead time × 100. Most batch processes score 5–15%. Lean flow systems typically achieve 25–80%. A PCE below 10% means 90% of lead time is waste.
WIP
Units trapped inside the system
Work In Progress — all units that have entered the process but haven't yet left it. High WIP hides defects, consumes floor space and cash, and makes problems harder to trace. Little's Law: Lead Time = WIP ÷ Throughput.
NVA
Time customers don't pay for
Non-Value-Added activities are anything a customer wouldn't pay for — waiting, moving, inspecting, reworking. The 7 wastes (TIMWOOD) are all forms of NVA. Eliminating NVA is the core of kaizen.

Simulation Controls

Adjust variables · then press Run

Speed 3×
Batch size: 8
Process steps: 4
Process time: 2s
Queue / wait: 3s
Units to produce: 16
One-Piece Flow Lead time: —
OUTPUT →
0 done
Batch Production Lead time: —
OUTPUT →
0 done
Process Cycle Efficiency — VA time as % of total lead time
Value-added
Non-value-added
Remaining
OPF
PCE: —%
Batch
PCE: —%
Press ▶ Run to start — watch units move through both production systems in real time

Why did OPF win? Understanding the results

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The three root causes behind every result

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The Queue Multiplier

In batch production, every unit in a batch must wait for all others to be processed before moving forward. With a batch of 10 and 4 steps, a single unit waits for 9 others at each step — that's 36 units worth of idle time per unit produced.

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Defect Exposure

In batch production, a defect introduced at step 1 isn't discovered until the whole batch reaches inspection — potentially after all 4 steps. In one-piece flow, defects surface immediately and affect only 1 unit, not the whole batch.

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Cash & Space Cost

Every unit sitting in WIP represents tied-up capital — material, labour, and overhead costs already spent but not yet recovered. Batch systems can carry 10–50× more WIP than flow systems, creating significant cash flow pressure.

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Little's Law

Lead Time = WIP ÷ Throughput. Reducing WIP by half — without touching process speed — cuts lead time by half. One-piece flow minimises WIP structurally, making lead time reduction automatic, not a goal to chase.

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First Unit Out

OPF delivers its first completed unit much earlier. In a customer service context, this means faster response times, earlier revenue recognition, and better ability to respond to demand changes mid-production.

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Why Batch Persists

Batch production feels efficient because machines appear busy. But machine utilisation ≠ system efficiency. Batch optimises local steps at the cost of system-wide flow. Lean optimises the whole value stream, not individual stations.

Real-world benchmarks

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Healthcare

Hospitals that moved from batch (process all forms → then triage → then treat) to flow reduced patient wait times by 40–60% without adding staff or beds.

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Manufacturing

Toyota's Camry line runs at near-zero WIP between stations. Batch competitors in the same sector carry 3–8 days of WIP and suffer 15–40% longer lead times.

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Software / Services

Agile sprints are one-piece flow for knowledge work. Organisations that shifted from large project batches to small continuous delivery reduced time-to-market by 50–80%.

Ready to apply this in your workplace?

Our TPS & Lean Fundamentals course covers flow, WIP, takt time, and value stream mapping — with practical tools you can use immediately.

Explore the Course →