JIT (Just In Time)JIT manufacturing is a philosophy of manufacturing based on planned elimination of waste & continuous improvement of productivity.Just in time is a ‘pull’ system of production, so actual orders provide a signal for when a product should be manufactured. Demand-pull enables a firm to produce only what is required, in the correct quantity and at the correct time.
Advantages of JIT1. Lower stock holding means a reduction in storage space which saves rent and insurance costs2. As stock is only obtained when it is needed, less working capital is tied up in stock3. There is less likelihood of stock perishing, becoming obsolete or out of date4. Avoids the build-up of unsold finished product that can occur with sudden changes in demand5. Less time is spent on checking and re-working the product of others as the emphasis is on getting the work right first time Disadvantages of JIT1. Production is very reliant on suppliers and if stock is not delivered on time, the whole production schedule can be delayed2. There is no spare finished product available to meet unexpected orders, because all product is made to meet actual orders – however, JIT is a very responsive method of production
JIT elements1. Product design element2. Process design element3. Personnel/organizational elements4. Manufacturing planning and controlThree elements of product design are key to JIT systems:1. Standard parts2. Modular design3. Quality Personnel Organizational Elements-1. Workers as assets2. Cross-trained workers3. Continuous improvement4. Cost accounting5. Leadership/project management
Process Design element-1. Small lot sizes2. Setup time reduction3. Manufacturing cells4. Limited work in process5. Quality improvement6. Production flexibility7. Little inventory storage Manufacturing Planning and ControlFive elements of manufacturing planning and control are particularly important for JIT systems:1. Level loading2. Pull systems3. Visual systems4. Close vendor relationships5. Reduced transaction processing
Kanban Kanban is the Japanese word for card The card is an authorization for the next container of material to be produced A sequence of kanbans pulls material through the process Many different sorts of signals are used, but the system is still called a kanban
Kanban 1. User removes a standard sized container 2. Signal is seen by the producing department as authorization to replenish Signal marker on boxesFigure 16.8 Part numbers mark location
Kanban Kanban Finished Customer goods order Work cell Ship Raw Kanban Final KanbanMaterial assemblySupplier Kanban Kanban Sub- Purchased assembly Parts Kanban Supplier Figure 16.9
More Kanban When the producer and user are not in visual contact, a card can be used When the producer and user are in visual contact, a light or flag or empty spot on the floor may be adequate Since several components may be required, several different kanban techniques may be employed
More Kanban Usually each card controls a specific quantity or parts Multiple card systems may be used if there are several components or different lot sizes In an MRP system, the schedule can be thought of as a build authorization and the kanban a type of pull system that initiates actual production
The Number of Kanban Cards or Containers Need to know the lead time needed to produce a container of parts Need to know the amount of safety stock needed Demand during SafetyNumber of kanbans lead time + stock (containers) = Size of container
Number of Kanbans Example Daily demand = 500 cakes Production lead time = 2 days (Wait time + Material handling time + Processing time) Safety stock = 1/2 day Container size = 250 cakesDemand during lead time = 2 days x 500 cakes = 1,000 1,000 + 250 Number of kanbans = 250 =5
Advantages of Kanban Allow only limited amount of faulty or delayed material Problems are immediately evident Puts downward pressure on bad aspects of inventory Standardized containers reduce weight, disposal costs, wasted space, and labor
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