Batch Race: why smaller batches ship sooner
A print shop has to deliver 12 invitation kits. You pick the size of the tray that carries kits from one station to the next and watch your line race a batch of 12. The difference in lead time shows on the clock.
Your call
A customer ordered 12 personalized invitation kits. Pick a tray size and run the line.
Shop rule: kits only move to the next station once the tray is full.
How it works
Every kit goes through four stations: Print, Cut, Fold and Pack. Each station has one person and takes one minute per kit. The shop rule is simple: kits only move to the next station once the tray is full. You drag a tray of 12, 6, 3, 2 or 1 kit onto your line (or tap it, or use the keyboard) and run the line.
Both lines run on the same clock. You can see stations sitting idle while they wait for the previous tray, kits piling up halfway and the moment the customer gets the first kit. At the end of each round, the comparison shows first kit, all kits, average time per kit, work in progress and idle time.
What you learn in each round
- Round 1: batch sizeYour call. With a batch of 12, the first kit arrives at minute 48. With a tray of 1, it arrives at minute 4, and each kit spends only its work time in the shop.
- Round 2: single-piece flowThe customer wants the first kit within 6 minutes. The math is simple: with a tray of b, the first kit ships after b × 4 minutes.
- Round 3: fast feedbackThe print file for one tray has the wrong date and only Pack checks the kits. With a batch of 12, all 12 kits go back to Print. With a tray of 1, only one does.
Who it is for
For anyone who wants to understand in a few minutes why teams that ship in small pieces get feedback sooner, for people who need to explain Little’s Law without writing a formula on the board, and for Kanban users who want to feel the cost of piling up work before passing it on.
Using it in a class or workshop
Have everyone play round 1 with no guidance and write down the tray they picked. Then compare as a group: when did the people with the biggest tray get their first kit? Close with the game’s question: what is your team’s batch of 12? It is often a release bundle, a review that waits for several tasks or testing left to the very end.
What the game simplifies
Changing tray size has no setup time, moving a tray takes no time and every station works at the same pace (in round 3, some kits have a special fold). In real life, setup cost is what pushes batches up, and cutting it is what makes small batches workable.
Keep practicing
- See how WIP changes lead time →The gap between the time the customer feels and the working time.
- Measure what the system delivers →Throughput: the basis of every delivery forecast.
- Run the kitchen at Kanban Pizzaria →Six nights at a pizzeria to feel WIP limits, bottlenecks and classes of service. No sign-up.
- Practice WIP limits →Watch flow change as work in progress goes up or down.
- Analyze my real flow →Upload your board CSV; nothing leaves your browser.
Frequently asked questions
What is batch size?
It is how much work piles up before it moves to the next step. In the print shop, it is the number of kits in a tray. In software teams, it can be the number of tasks waiting together for a review, a test or a release.
Why does a batch of 12 take so long if each kit needs only 4 minutes of work?
Because each kit waits for the other 11 at every station. The work is the same, but waiting in the tray multiplies each kit’s time in the shop: 42.5 minutes on average, against 4 with a tray of 1.
How does the game measure lead time?
From the moment a kit starts printing until it reaches the customer. That is when the shop starts working on that kit. In the Kanban Method, lead time starts at the commitment point; here, to isolate the batch effect, we count from the start of production.
Where does Little’s Law come in?
In the campaign summary. The game shows that average work in progress equals throughput times average lead time, using the numbers from your round 1.
Do I need an account to play?
No. Your best result is saved in your browser. With a free account, your score goes to My Progress.
Take flow to a product team
The Kanban Game uses the same ideas with a software squad, more decisions, a leaderboard and seasons.
