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Chapter 6 Just-in-Time
1 Introduction The term Just-in-time is used to refer to a repetitive production system in which both the movement of goods during production, and delivers from suppliers, are carefully timed so that at each step of the process the next (usually small) batch arrives for processing just as the preceding batch is completed.
Origin of JIT • The JIT approach was developed at the Toyota Motor Company of Japan by Mr. Taiichi Obno and several of his colleges. Taiichi became eventually vice president of manufacturing. • The development of JIT in Japan was influenced by the fact Japan is a crowed country with few natural resources. • The JIT and supermarkets.
Benefits of JIT (1) • Inventory levels are drastically reduced. • The production period is greatly reduced. • Product quality is improved. And cost of scrap and rework is reduced. • Reduced space with inventory and materials-handling equipment.
Benefits of JIT (2) • Reduced manufacturing lead-time. • Fewer workers. • Promotes teamwork: Workers are closer together so that they communicate more easily, work out problems more efficiently. • Greater flexibility in work assignments and in changing production mix
3. Key thought ---eliminating waste • Waiting waste • Transportation waste • Work-in-process waste • Inventory waste • Waste of unneeded production steps • Waste of unnecessary human motions (motion and effort) • Defective products • Overproduction waste
eliminating waste figure • Figure 14.3 ( P.546)
4.1 A pull system （1） • In a push system, when work is finished at a workstation, the output is pushed to the next station: or in the case of the final operation, it is pushed on to final inventory. • Traditional production systems use the push approach.
4.1 A pull system （2） • In a pull system, control of moving the work rests with the following operation; each workstation pulls the output from the preceding station as it is needed; output of the final operation is pulled by customer demand or master schedule. • JIT systems use the pull approach to control the flow of work, with each workstation gearing its output to the demand presented by the next workstation.
4.2 Kanban production control • Kanban means card. • Types of Kanban There are two types of Kanban cards: a conveyance card (C-kanban) and a production card (P-Kanban). • Figure 14.4 (p. 548) • Knaban operation • Kanban operation Rules. • Figure 14.5 (p.549)
4.3 Small lot sizes • Small lot sizes yield a number of benefits that enable JIT systems to operate effectively. • Less work-in-process inventory • Reduce carrying costs, space requirements and clutter in the workplace • Less quality cost • Greater flexibility in scheduling • Ideal lot size is one unit.
4.4 Few, reliable suppliers （1） • Supplier development and suppliers undergo fundamental changes. ------ Subcontractor networks and co-producers. • Long-term relationships with suppliers. • Delivery schedules, product quality, and mutual trust and cooperation become the primary basis for supplier selection. • Suppliers are encouraged to extend JIT methods to their own suppliers.
4.4 Few, reliable suppliers （2） • Suppliers are ordinarily located near the buying firm's factory. • Shipments are delivered directly to the customer's production line. • Exact quantities. • Near-perfect quality
4.5 Quick, low-cost setups （1） • Small lots and changing product mixes require frequent setups. Unless these are quick and relatively inexpensive, the time and cost to accomplish them is prohibitive.
4.5 Quick, low-cost setups （1） • Suitable setup tools and equipment • Simplify setup procedures and methods • Transform inside-setup-work to outside-setup-work • Group technology • Multipurpose equipment • Train workers
6. Conditions • Stabilize production schedules • Make the factories more focused • Improve product quality • Good cross-train workers • Good and reliable suppliers • Good delivery conditions • Preventive maintenance, etc.
