ISQA 459 Mellie Pullman 1
Dec 25, 2015
ISQA 459 Mellie Pullman
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JIT can be defined as an integrated set of activities designed to achieve high-volume production using minimal inventories (raw materials, work in process, and finished goods).
JIT also involves the elimination of waste in production effort.
JIT also involves the timing of production resources (e.g., parts arrive at the next workstation “just in time”).
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Elimination of waste Efforts concentrated on shop floor
Respect for peopleQuality improvement focus
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(1) Waste from overproduction
(2) Waste of waiting time
(3) Transportation waste
(4) Inventory waste
(5) Processing waste
(6) Waste of motion
(7) Waste from product defects
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5
Customers
Sub
Sub
Fab
Fab
Fab
Fab
Vendor
Vendor
Vendor
Vendor
Final Assembly
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Final Assembly
CoordinationSystem Integration
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A
B
C
A
C
B
Sporadic and Infrequent
Deliveries from Individual Suppliers
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A
B
C
ABC
Regular and Frequent
Deliveries from Many Suppliers
Using Departmental Specialization for plant layout can cause a lot of unnecessary material movement.
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Saw Saw
Lathe PressPress
Grinder
LatheLathe
Saw
Press
Heat Treat
Grinder
Revising by using Group Technology Cells can reduce movement and improve product flow.
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Press
Lathe
Grinder
Grinder
A
2
BSaw
Heat Treat
LatheSaw Lathe
PressLathe
1
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Not uniform Jan. Units Feb. Units Mar. Units Total
1,200 3,500 4,300 9,000
Uniform Jan. Units Feb. Units Mar. Units Total
3,000 3,000 3,000 9,000
Suppose we operate a production plant that produces a single product. The schedule of production for this product could be accomplished using either of the two plant loading schedules below.
How does the uniform loading help save labor costs?
or
Company produces three products with a mixed model assembly line. Operates 16 hours
per day for 250 days/yr.
Determine the mixed model MPS for a daily batch.
Determine minimum batch MPS and the mix schedule for a day.
Products Forecasts (year)
1 20,000
2 10,000
3 5,000
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#1 #2 #3
Year Forecast 20000 10000 5000
Daily Batch divide by 250 80 40 20
Hourly Batch divide by 16 5 2.5 1.25
Minimum Batch MPS 4 2 1
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For every unit of #3 (minimum batch), we need twice as many #2 and 4 timesAs many #1 so for minimum batch:Produce during each day produce #1,1,1,1,2,2,3 - repeated 20 times
Company produces four products with a mixed model assembly line. Operates 8hours per
day for 250 days/yr. Determine the
mixed model MPS for a daily and hourly batch .
Determine mix schedule for a day.
Products Forecasts (year)
I 500
II 1500
III 4500
IV 6000
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• Management philosophy• “Pull” system though the plant
WHAT IT IS
• Employee participation• Industrial engineering/basics• Continuing improvement• Total quality control• Small lot sizes
WHAT IT REQUIRES
• Attacks waste• Exposes problems and bottlenecks• Achieves streamlined production
WHAT IT DOES
• Stable environment
WHAT IT ASSUMES
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Work in
process
queues
(banks)
Change
orders
Engineering design
redundancies
Vendor
delinquencies
Scrap
Design
backlogs
Machine
downtime
Decision
backlogsInspection
backlogs
Paperwork
backlog
Example: By identifying defective items from a vendor early in the production process the downstream work is saved.
Example: By identifying defective work by employees upstream, the downstream work is saved.
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Storage Part A
Storage Part AMachine
Center Assembly Line
Material Flow
Card (signal) Flow
Withdrawal kanban
Production kanban
Setting up a kanban system requires determining the number of kanbans (or containers) needed.
Each container represents the minimum production lot size.
An accurate estimate of the lead time required to produce a container is key to determining how many kanbans are required.
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19
C
SdL
k
)(1
container theof Size
stockSafety timelead during demand Expected
k = Number of kanban card sets (a set is a card)d = Average number of units demanded over some time periodL = lead time to replenish an order (same units of time as demand)S = Safety stock expressed as a percentage of demand during lead timeC = Container size
A switch assembly is assembled in batches of 4 units from an “upstream” assembly area and delivered in a special container to a “downstream” control-panel assembly operation.
The control-panel assembly area requires 5 switch assemblies per hour.
The switch assembly area can produce a container of switch assemblies in 2 hours.
Safety stock has been set at 10% of needed inventory.
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3or ,75.24
5(2)(1.1))(1
container theof Size
stockSafety timelead during demand Expected
C
SdL
k
Always round up!
Link operations
Balance workstation capacities
Re-layout for flow
Emphasize preventive maintenance
Reduce lot sizes
Reduce setup/changeover time
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Standard product configuration
Standardize and reduce number of parts
Process design with product design
Quality expectations 23
Level payrolls
Cooperative employee unions
Subcontractor networks
Inverted pyramid management style
Small group involvement activities
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Worker responsibility
Measure SQC
Enforce compliance
Fail-safe (Poke-yoke) methods
Automatic inspection
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Damaged parts Missing parts Reversed parts Wrong parts Wrong size or shape Wrong chemical
properties Wrong physical
properties Wrong item shipped Wrong label Wrong package Damaged finished
product
Omitting a part Omitting a process Performing a process
incorrectly Performing a process on the
wrong part Performing a process in
improper environmental conditions
Performing the wrong process
Setting up equipment incorrectly
Setting up a work piece incorrectly
Adjusting equipment incorrectly
Tooling set up incorrectly Tooling adjusted incorrectly Installing wrong part Installing part incorrectly 26
DEFECTSDEFECTS MISTAKESMISTAKES
Reduce lead times
Frequent deliveries
Project usage requirements
Quality expectations
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Look for other areas where inventory hides
Stores
Transit
Carousels
Conveyors
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• MRP is a planning system that MRP is a planning system that does not do detailed shop floor does not do detailed shop floor schedulingscheduling
• MRP requires fixed lead times MRP requires fixed lead times which might actually vary with which might actually vary with batch sizebatch size
• JIT excels at rapidly moving small JIT excels at rapidly moving small batches of material through the batches of material through the systemsystem
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1.1. MRP “buckets” are reduced to daily or hourlyMRP “buckets” are reduced to daily or hourly
• The most common planning period (time The most common planning period (time bucket) for MRP systems is weeklybucket) for MRP systems is weekly
2.2. Planned receipts are used internally to sequence Planned receipts are used internally to sequence productionproduction
3.3. Inventory is moved through the plant on a JIT Inventory is moved through the plant on a JIT basisbasis
4.4. Completed products are moved to finished goods Completed products are moved to finished goods inventory which reduces required quantities for inventory which reduces required quantities for subsequent planned orderssubsequent planned orders
• Back flushing based on the BOM is used to Back flushing based on the BOM is used to deduct inventory that was used in productiondeduct inventory that was used in production
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• Used in repetitive operationsUsed in repetitive operations
• MRP plans are executed using JIT MRP plans are executed using JIT techniques based on “pull” techniques based on “pull” principlesprinciples
• Flows are carefully balanced with Flows are carefully balanced with small lot sizessmall lot sizes
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• Items used by many products are Items used by many products are held in a common area often called held in a common area often called a supermarketa supermarket
• Items are withdrawn as neededItems are withdrawn as needed
• Inventory is maintained using JIT Inventory is maintained using JIT systems and proceduressystems and procedures
• Common items are not planned by Common items are not planned by the MRP systemthe MRP system