Post on 03-Apr-2018
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JIT (Just In Time)
JIT manufacturing is a philosophy ofmanufacturing based on plannedelimination of waste & continuousimprovement of productivity.
Just in time is a pull system ofproduction, so actual orders provide asignal for when a product should be
manufactured. Demand-pull enables afirm to produce only what is required, inthe correct quantity and at the correcttime.
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Advantages of JIT
1. Lower stock holding means a reduction in storage space whichsaves rent and insurance costs
2. As stock is only obtained when it is needed, less working capital istied up in stock
3. There is less likelihood of stock perishing, becoming obsolete orout of date
4. Avoids the build-up of unsold finished product that can occurwith sudden changes in demand
5. Less time is spent on checking and re-working the product ofothers as the emphasis is on getting the work right first time
Disadvantages of JIT
1. Production is very reliant on suppliers and if stock is notdelivered on time, the whole production schedule can be delayed
2. 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
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JIT elements1.
Product design element2. Process design element
3. Personnel/organizational elements4. Manufacturing planning and controlThree elements of product design are key to JIT systems:1. Standard parts
2. Modular design3. Quality
Personnel Organizational Elements-1. Workers as assets2. Cross-trained workers3. Continuous improvement4. Cost accounting
5. Leadership/project management
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Process Design element-1. Small lot sizes2. Setup time reduction3. Manufacturing cells
4. Limited work in process5. Quality improvement6. Production flexibility
7. Little inventory storage
Manufacturing Planning and ControlFive elements of manufacturing planning and control are
particularly important for JIT systems:
1. Level loading
2. Pull systems3. Visual systems4. Close vendor relationships
5. Reduced transaction processing
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Kanban
Kanban is the J apanese word for card
The card is an authorization for the nextcontainer of material to be produced
A sequence of kanbanspulls material throughthe process
Many different sorts ofsignals are used, butthe system is still calleda kanban
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Kanban
1. User removes astandard sizedcontainer
2. Signal is seen bythe producingdepartment asauthorization toreplenish
Part numbers
mark location
Signal markeron boxes
Figure 16.8
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Kanban
Figure 16.9
Workcell
RawMaterialSupplier
Kanban
PurchasedParts
Supplier
Sub-assembly
Ship
Kanban
Kanban
Kanban
Kanban
Finishedgoods
Customerorder
Finalassembly
Kanban
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More Kanban
When the producer and user are not invisual contact, a card can be used
When the producer and user are in visual
contact, a light or flag or empty spot onthe floor may be adequate
Since severalcomponents may
be required,several differentkanban techniquesmay be employed
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More Kanban
Usually each card controls a specificquantity or parts
Multiple card systems may be used ifthere are several components ordifferent lot sizes
In an MRP system, the schedule can
be thought of as a build authorizationand the kanban a type of pull systemthat initiates actual production
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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 safetystock needed
Number of kanbans(containers)
Demand during Safety
lead time + stockSize of container
=
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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 cakes
Demand during lead time = 2 days x 500 cakes = 1,000
Number of kanbans = = 51,000 + 250
250
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Advantages of Kanban
Allow only limited amount of faulty ordelayed material
Problems are immediately evident Puts downward pressure on bad
aspects of inventory
Standardized containers reduceweight, disposal costs, wasted space,and labor