Tell apart types of production method (生産方式) by what triggers production and how the work is organized.
Explain how JIT and the kanban method (かんばん方式) relate, following the replenishment instruction as it travels from the downstream process back upstream.
Follow the MRP procedure to calculate a part's net requirement and when to place the order.
A production method (生産方式) is the umbrella term for the patterns of making things that decide when, how many, and under what setup a product is made.
Basis for dividing
Example production methods
What triggers production
Make-to-order (build after the order) / make-to-stock (build ahead of forecast demand)
How the work is organized
Line production (processes split and passed along) / cell production (a small team handles every process)
For example, make-to-order production, which starts only after an order comes in, and make-to-stock production, which builds ahead based on forecast demand, differ in what triggers production. By how the work is organized, there is line production, where a conveyor carries work through divided processes, and cell production, where one person or a small team handles every process.
AnalogySome restaurants cook only after you order, while others set out dishes made in advance. The term refers to that cooking policy, not to the food itself.
Exam points
ExamCell production (セル生産) is a production method (生産方式) in which one person or a small team handles every process from start to finish, and it suits high-mix, low-volume output.
ExamMake-to-order production (受注生産) starts only once an order is confirmed, so there is no risk of finished goods going unsold and piling up as stock. The trade-off is that nothing can ship the moment the order arrives.
ExamCAM is not a production method itself but a system that uses computers to create the machining data that drives machine tools, supporting manufacturing work.
JIT (just-in-time, ジャストインタイム) is a production method in which each process makes and delivers parts or products to match when and how much the next process uses, keeping inventory between processes to a minimum.
It has been the core idea behind the production systems of Japanese carmakers, and the same thinking is applied to sourcing raw materials and parts. With fewer half-finished items (work in process) and parts sitting between processes, wasted storage space and overproduction shrink. On the other hand, the line tends to stop right away if the parts supply is interrupted.
AnalogyThink of a convenience store shelf restocked several times a day with exactly what sold. The shelf never goes empty, even without a big stockroom in the back.
How to rememberJust In Time is like reaching the platform right as the train leaves. Too early and you become inventory; too late and you have a stockout.
Exam points
ExamUnder JIT, every process produces in response to requests from the next process, so the work in process (仕掛品) and parts that pile up between processes decrease.
Mix-upBTO (build to order) keeps stock as parts and assembles to the ordered specification, a type of make-to-order production (受注生産). JIT is an idea about flowing work without stock building up between processes, so the two focus on different things.
The kanban method (かんばん方式) puts JIT into practice on the shop floor by passing a kanban (instruction card) showing the part number and quantity from the downstream process back upstream, so only what was used gets made and moved.
Downstream process uses parts
Removed kanban returns upstream
Upstream makes only the kanban amount
Parts go downstream with the kanban
Finished parts go out with a kanban attached, and the same cycle repeats.
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When the downstream process uses parts, the kanban comes off and becomes the instruction to the upstream process to replace that amount. Because the upstream process never makes more than the number of kanban cards, overproduction is unlikely. Besides paper cards, the same instruction can also be sent as electronic data.
AnalogyIt is like using empty milk cartons as your shopping list and buying only as many as are empty. No empty cartons, no trip to the store.
How to rememberA kanban is originally a shop sign that tells customers something. In the factory it becomes the signal that tells the upstream process what to make.
Exam points
ExamThe kanban method is a pull-type (引取り型) mechanism that tells the upstream process how much was used so it makes that amount, and it is one way of achieving JIT.
ExamThe replenishment instruction carried by kanban goes not only to upstream processes inside the company but also to the suppliers that deliver parts.
Lean production (リーン生産方式) is an approach in which Western researchers reorganized the Toyota Production System, aiming to remove waste that adds no value from processes and produce efficiently with fewer resources.
What to review in business improvement
Muda: work or motion that adds no value
Muri: load beyond capacity
Mura: unevenness in load or results
Lean is an English word meaning without excess fat, and the approach takes in the inventory reduction of JIT and the kanban method. It identifies waste such as overproduction, transport, and waiting, and keeps improving. Business improvement also reviews muri (ムリ), load beyond capacity, and mura (ムラ), unevenness.
AnalogyLike packing for a move by getting rid of things you don't use, cutting the number of trips, and smoothing out the plan, it works toward traveling light.
How to rememberLean means slim. Picture a factory that has trimmed the fat of inventory and idle waiting.
Exam points
ExamIn lean production (リーン生産方式), muda (ムダ) means work or motion that does not raise a product's value, such as overproduction or unneeded transport. It is a separate angle from muri (ムリ), excess load, and mura (ムラ), unevenness.
ExamLean production takes in the ideas of JIT and the kanban method (かんばん方式), arranging parts to match when they are used and keeping work in process at a suitable level.
MRP (material requirements planning, 資材所要量計画) is a method that calculates the quantities of parts and materials needed and when to order them, based on the product's production plan and bill of materials.
Production plan (product and quantity)
Gross requirement from the bill of materials
Subtract stock for net requirement
Order earlier by the lead time
If Y takes 2 weeks to procure, order 26 two weeks before the week they are used.
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A bill of materials is a table that shows, in levels, which parts one unit of a product uses and how many of each. MRP multiplies the number of products needed by the quantities in the bill of materials to get the gross requirement, then subtracts usable stock to find the net requirement. It then counts back by the lead time needed for procurement or processing to set when to order or start work.
AnalogySay you decide to make boxed lunches for 30 people on Friday. You work out the rice and fillings from a one-serving ingredient list, subtract what is already in the fridge, and pick the order date from how many days delivery takes.
How to rememberThe letters stand for Material, Requirements, and Planning, and the Japanese name is a direct translation of those words.
Exam points
ExamMRP (資材所要量計画) works out how many component parts are needed from a product's due date and quantity, keeping parts stock at neither too much nor too little.
ExamThe net requirement (正味所要量) is the gross requirement (総所要量) minus usable stock. When parts are stacked in several levels, subtract the upper-level part's stock first and then calculate the lower level's requirement.
ExamParts are arranged by counting back from when they are used by the lead time (リードタイム). When some parts can be arranged in parallel, the total time needed is set by the longest path.
An FMS (flexible manufacturing system, フレキシブル生産システム) is an automated setup that uses computers to control NC machine tools, robots, automated guided vehicles, and the like together, so it can flexibly handle high-mix, low-volume production.
Dedicated automated line
FMS
Suited to
Making one product in large volumes
Making many product types a little at a time
Switching product types
Requires rebuilding the line
Handled by switching programs
Even when the product changes, machining programs and tools are swapped automatically, so the next product can be made without a major rebuild of the line. Automated guided vehicles and robots also handle moving the workpieces.
AnalogyLike a kitchen appliance that switches between baking, boiling, and steaming at the press of a button, it changes what it makes without swapping machines.
How to rememberF stands for Flexible, as in flextime at work: not tied to one fixed pattern.
Exam points
ExamAn FMS automates the manufacturing (製造) process of machining and assembly, and the labor savings and efficiency gains from adopting it show up in that process.
A production method is the umbrella term for patterns of making things, and its types divide by angles such as what triggers production and how the work is organized.
Under the kanban method, the upstream process makes only as many as there are kanban cards, so overproduction is unlikely.
Lean production is an improvement approach that keeps finding and removing waste that adds no value.
In MRP, the net requirement is the gross requirement minus usable stock, and orders are placed by counting back the lead time.
An FMS uses computer control to make switching product types easy and automates high-mix, low-volume production.