SIM03 · 起源 / 超市补货变成生产许可SIM03 · Origin / From supermarket replenishment to production authorization
没有看板，上游还该不该投料？Should upstream release material without a Kanban?
年，大野耐一从美国超市“拿走多少、补回多少”的机制得到启发，并把它带进丰田现场。下游取走一件，青色看板就返回上游，成为下一件的生产许可。卡不回来，上游就停；看板数 K 则直接卡住工序间在制品上限。 In , Taiichi Ohno adapted the American supermarket rule—replenish only what was taken—for Toyota's shop floor. When downstream withdraws one part, a cyan Kanban travels upstream and authorizes one replacement. No returned card means no build; the card count K sets a hard ceiling on interprocess WIP.
🎬 盯住青色卡：物流向右，看板向左🎬 Follow the cyan card: parts move right, Kanban moves left
0
WIP0.0
—
看板回流Kanban return
绿 <1 节拍Green <1 takt
琥珀 <3Amber <3
红 ≥3Red ≥3
💡 跑完看数据：卡数越多，在制品和周期越高💡 Run it, then read the numbers: more cards raise WIP and lead time
四档均由同一 DES 的 stats() 计算All four modes come from the same DES stats()| 模式Mode | 120 秒产量Output / 120 sec | 平均在制品Average WIP | 平均周期Average lead time |
|---|---|---|---|
| K=2 | — | — | — |
| K=4 | — | — | — |
| K=8 | — | — | — |
| K=∞ · 推动式K=∞ · Push | — | — | — |
平均周期按 Little 定律计算：平均在制品 ÷ 产出率。K=∞ 时取消看板许可和缓冲上限，投料一次压入产线，立即退回推动式。Average lead time uses Little's Law: average WIP ÷ throughput rate. At K=∞ the authorization signal and buffer cap disappear, so material is released as a push batch.
🎯 现场规则🎯 Shop-floor rule
无看板不生产；看板总数就是在制品上限。No Kanban, no build. The card count is the WIP limit.
⚠ 常见误区⚠ Common mistakes
✗ 看板就是一张卡片✗ Kanban is just a card
✓ 看板是“允许生产”的信号，没有它就不许做。✓ A Kanban is authorization to produce. Without it, do not build.
✗ 上限放松点更保险✗ A looser limit is safer
✓ 上限放松到无限，就是推动式。✓ Remove the limit entirely and the system becomes push.
✗ 老缺料就多发看板✗ Add cards whenever the line starves
✓ 先解决造成停线的问题，再调整 K。✓ Fix the cause of starvation first, then tune K.