JIT-32p

Grinder
Heat Treat
Lathe
Lathe
Lathe
Press
Press
Press
9
Minimizing Waste: Group Technology
• Revising by using Group Technology Cells can reduce movement and improve product flow.
• 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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The Number of Kanban Card Sets
Expected demand during lead time + Safety stock k= Size of the container dL(1 + S ) = C
k = Number of kanban card sets (a set is a card) d = Average number of units demanded over some time period L = lead time to replenish an order (same units of time as demand) S = Safety stock expressed as a percentage of demand during lead time C = Container size
Final Assembly
6
Traditional Conveyance
A
B
C
Sporadic and Infrequent Deliveries from Individual Suppliers 7
Mixed-Load Delivery
A
B
C
Regular and Frequent Deliveries from Many Suppliers
4
DemandJIT Demand-Pull Logic
Fab Sub Fab Customers Vendor Vendor
Final Assembly
Sub Fab Vendor
Fab
5 Vendor
Minimizing Waste: Focused Factory Networks
Coordination System Integration
Products I II III IV
Forecasts (year) 500 1500 4500 6000
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Just-InMinimizing Waste: Just-In-Time Production
WHAT IT IS • Management philosophy • “Pull” system though the plant WHAT IT DOES • Attacks waste
For every unit of #3 (minimum batch), we need twice as many #2 and 4 times As many #1 so for minimum batch: Produce during each day produce #1,1,1,1,2,2,3 - repeated 20 times
Withdrawal kanban
Machine Center
Storage Part A
Storage Part A
Assembly Line
Production kanban
Material Flow Card (signal) Flow
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Determining the Number of Kanbans Needed
8
Minimizing Waste: Group Technology
• Using Departmental Specialization for plant layout can cause a lot of unnecessary material movement.
Saw
Saw
Saw
Grinder
20
Example of Kanban Card Determination: Calculations
Products 1 2 3
Forecasts (year) 20,000 10,000 5,000
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Calculations
#1 Year Forecast Daily Batch Hourly Batch Minimum Batch MPS divide by 250 divide by 16 20000 80 5 4 #2 10000 40 2.5 2 #3 5000 20 1.25 1
• Stable environment
15
Minimizing Waste: Inventory Hides Problems
Machine downtime Scrap Work in process queues (banks) Vendor delinquencies Change orders Design backlogs
Grinder Saw Lathe
1
2
Lathe
Press
Heat Treat
Grinder Saw Lathe
A
B
Lathe
Press
10
Minimizing Waste: Uniform Plant Loading
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.
(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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Mixed Batch Example
• 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.
JIT
ISQA 459 Mellie Pullman
1
Defined
Just-InJust-In-Time (JIT)
• 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”).
• Exposes problems and bottlenecks • Achieves streamlined production
WHAT IT REQUIRES
WHAT IT ASSUMES
• Employee participation
• • • • Industrial engineering/basics Continuing improvement Total quality control Small lot sizes
2
The Japanese Approach to Productivity
• • • •
Elimination of waste Efforts concentrated on shop floor Respect for people Quality improvement focus
3
Waste in Operations
Example: By identifying defective items from a vendor early in the production process the downstream work is saved.
Engineering design redundancies