問28
頻出度★★☆
ジャストインタイム生産方式を説明したものはどれか。
平成21年度 春期 ITパスポート試験 問28
This question's explanation and your answers so far.
解説
問 28
Incorrectア
This describes cell production (also called the one-person-build or “yatai” method). One worker, or a few workers, handle all the steps from assembly to inspection at a single workbench (a cell), which makes it easy to cope with high-mix low-volume production and with specification changes. It is a matter of how the work is divided — who covers which steps — whereas JIT is about timing and quantity, that is, when and how much to make. The focus is different.
Incorrectイ
This describes make-to-order production. Production starts only after a customer order is received, so unsold stock is unlikely, but the delivery time becomes longer by the length of the production period. JIT may look similar in that it also reduces inventory, but JIT does not turn on whether an order exists; it prescribes synchronization between processes — letting only the necessary quantity flow at the necessary time — and it can be applied to a make-to-stock line as well. As a definition it is a different thing, so this is wrong.
Incorrectウ
This describes make-to-stock (planned) production. The quantity is decided in advance from a demand forecast and the goods are built ahead of time, so the delivery time can be short; but if the forecast is off, excess inventory or shortages occur. The idea is to build extra in advance and hold it as stock, which is in fact the opposite of JIT, which tries to eliminate the waste of inventory.
- エ
正解 The correct answer is エ. Just-in-time (JIT) production is one of the pillars of the Toyota Production System, and it means producing and supplying only the necessary items, at the necessary time, in the necessary quantity. As the name “just in time” suggests, things are made so that they are ready exactly when needed, so as few parts and work-in-process items as possible are left sitting as stock, which cuts the waste of overproduction, inventory costs, and storage space. The representative way of achieving this is the Kanban method: the later process uses a kanban card to tell the earlier process to hand over exactly the amount it has used, producing a pull-type flow in which the later process withdraws what it needs from the earlier process. エ states this definition itself, so it is correct.
ここがポイント
- Just-in-time (JIT) production = make only the necessary items, at the necessary time, in the necessary quantity. Its aim is to eliminate the waste of inventory and overproduction, and the means of achieving it is the Kanban method, which circulates instruction cards to run a pull-type flow where the later process withdraws from the earlier one.
- Production methods can be sorted by what decides the quantity and timing of production: JIT produces only the amount needed, in sync with need; make-to-order produces after an order is received; make-to-stock produces in advance from a demand forecast; and cell production is a way of organizing the work so that a few people cover all the steps (it is not about quantity or timing).
用語