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1、Kanban Scheduling SystemsThe Challenge of SimplicityPage 7MQIP Management Consultants Co. LTD Your Professional Quality Improvement Partnerwww. Tel: 020-33689262, 38761191What Is Kanban SchedulingKanban scheduling systems are among the most simple, effective and inexpensive means for manufacturing
2、production and inventory control. The concept is proven. From Nagoya to Wichita Falls; from Windsor to Geelong; from microelectronics to heavy steel Kanban scheduling systems reduce inventory, eliminate stockouts, displace massive computers and slash overhead. They improve both service and quality.S
3、o why doesnt every manufacturer employ this miracle? In many situations, it is inappropriate other methods work better. Even When Kanban is an excellent choice, firms may ignore it. Kanban scheduling often evokes strong emotional responses from both proponents and detractors and sets a variety of or
4、ganizational phenomena at work against it.Kanban scheduling systems operate like supermarkets. A small stock of every item sits in a dedicated location with a fixed space allocation. Customers come to the store. They visually select and purchase their items. An electronic signal goes to the supermar
5、kets regional warehouse which details which items have sold. The warehouse prepares a (usually) daily replenishment delivery of the exact items sold.In large, modern supermarkets Kanban signals come from checkout scanners. They travel electronically (usually once each day) to the warehouse. Some sto
6、res still use a visual system. Here, a clerk walks the aisles daily. From empty spaces he deduces what sold. The clerk then orders replacements. This signal might go by telephone, FAX or courier. Often it travels on the returning delivery truck.Another variation is the bread truck. Here drivers foll
7、ow a fixed route from store to store. They have a supply of bakery items in their truck. At each stop, they examine the stock and replenish what has been sold.A Manufacturing ExampleKanban scheduling in manufacturing works in the same way. The essential elements of a system are: Stockpoint(s) Withdr
8、awal Signal Immediate Feedback Frequent ReplenishmentIn the manufacturing kanban system shown below, a machine shop supplies component parts to final assembly. Assembly is a manual operation with little setup. Assembly produces in lot sizes of one according to customer requirements.Machining is more
9、 automated than assembly and has significant setup costs. Machining must produce in batches to amortize the setup and sequence parts to minimize tool changes.A small quantity of every part is maintained at the machine shop. By observing the remaining quantities, the machinists know what products nee
10、d to be made next.Kanban and Other MethodsProduction Control coordinates multi-step processes, often with multiple products. Kanban is just one of several ways to achieve this coordination.Physical Linking is another way to coordinate. Here, each part in the process moves in synchronization and each
11、 step starts simultaneously. Processes must have the same lot size and co-location.In Broadcast, a final assembly operation builds directly to schedule. The schedule is simultaneously Broadcast to upstream subassembly and supply operations. They build the needed parts in Line-Set Order with a small
12、time offset for delivery. This system does not require co-location. It does require identical lot sizes (usually one) for all processes.Kanban scheduling systems are useful when lot sizes differ between process steps, processes are unbalanced or when distance introduces time lag or variability. Thes
13、e systems slightly de-couple the processes.Materials Requirements Planning (MRP) works from Bills Of Material (BOM), routings, inventory records and forecasts. It plans each process step for each product, subassembly and item. The system accumulates demand for each work center and each time period.
14、MRP allows effective scheduling under the most difficult conditions.This ability to connect a disjointed production comes with a price. MRP permits some forms of sloppy engineering. The administrative costs are high. Throughput times are long and inventory turns low. Errors in inventory, BOMs or lea
15、d times disrupt the system. About 50%-80% of installed MRP systems do not meet their users needs.Re-Order Point (ROP) systems store each item and issue to downstream work centers on request. ROP signals a resupply when the inventory is just sufficient to cover the resupply time.ROP systems are simpl
16、e. They require steady and predictable withdrawal rates and predictable replenishment times. But, these conditions are rare. Typical systems have very high inventories and experience frequent stockouts.Kanban CartA Hierarchy Of MethodologyThe figure below shows how the methods form a hierarchy of simplicity and flexibility. The best system is the simplest.Where the
