View
217
Download
0
Category
Tags:
Preview:
Citation preview
Just-In-Time
Chapter 3
JIT Overview
JIT is both a management philosophy and
a set of operational techniques.
• An element of the Toyota’s Production System
(VBW, Figure 3.17)
The philosophy is based on:
• Planned elimination of all waste
• Continuous improvement of productivity
Sources of Waste
Overproduction (inventory) Defects Personnel Equipment Space Time (inefficiency) Utilities
Major Elements of JIT
Carry inventory only when needed Improve quality to zero defects Reduce setup times and lot sizes. Focus on continual improvement. Make efforts to involve workers and use
their knowledge to a greater extent. Achieve improvement at minimum cost
JIT in Manufacturing
JIT makes major changes in the actual
practice of manufacturing by reducing:
• Complexity of detailed material planning.
• Need for shop-floor tracking.
• Work-in-process inventories.
• Transactions associated with shop-floor and
purchasing systems.
JIT in Services
Synchronize and balance information and
workflow
Increase process visibility
Continuously improve processes
Eliminate all waste (including paperwork)
Increase resource flexibility
JIT and MPC: the System(VBW, figure 3.1)
Resourceplanning
Productionplanning
Demandmanagement
Master productionscheduling
Detailed capacityplanning
Detailed materialplanning
Material andcapacity plans
Shop-floorsystems
Vendor systems
Front end
Engine
Back end
JIT and MPC
Front end:• Level capacity loading
Engine:• Reduce number of part numbers planned.
• Reduce number of levels in the BOM.
Back end:• Focus on simplicity—shop-floor and purchasing.
• Backflushing.
JIT and MPC Building Blocks (Table 3.1, VBW, p. 77)
Product design
• Standard parts, product simplification, modular design, robust design, scheduled design changes, design quality
Process design
• Band width—surge capacity to accommodate product mix and demand variations.
• Process flexibility
• Setup time reduction
• Cellular system
JIT and MPC Building Blocks (Table 3.1, VBW, p. 77)
Human/organizational elements
• Whole person concept—continual learning and improvement.
• Cross-training
• Motivation and empowerment
Manufacturing planning/control
• Pull system
• Visibility
• Simplified planning and control
JIT Example—Muth Pots
Leveling the production Pull system introduction
• Material movements and production authorized by signal of need from a “downstream” work center.
• Schedule must be “frozen” for a period of time.
• Determine the container size/capacity/number. Product design Process design Bill of materials implications
JIT Applications
Single-card kanban system (Figure 3.16, p. 90) Two-card kanban system (Toyota)
• Transport, or conveyance, card.
• Production card.
Two-bin or three-bin system Kanban cards replace all work orders and move
tickets. Kanban cards may be used with suppliers.
Calculating Number of Kanbans
a
DLy
1 Y=no. of kanbans D=demand/unit of time [800/day] L=lead time [2 hours=0.25 days] a=container capacity [20] =safety stock [25%]
cards135.12
20
25.125.0*800
Control Through Signaling
Simplicity Use different methods – kanban, container,
tennis balls, computerized display board (Andon board), etc.
Planning to schedule/producing to pull signal
• Make or move only with an authorized signal
• First-in, first-out
Workplace Organization
Is referred to as housekeeping Is a means to identify and maintain an
orderly environment Is a prerequisite for inventory management Prevents errors and contamination Basic concepts: simplification, organization,
discipline, cleanliness, participation
Six (6) S’s
Seiri – organization
Seiton –tidiness
Seiso –purity
Seiketsu – cleanliness
Shitsuke – discipline
Shikkari-yarou – let’s try hard
Setup Time
Internal versus external setup time (setup time when the machine is not running)
Reduce the setup time by studying:
• The machine itself
• Attachments
• Tools
• Workplace organization
• Transfer of internal setup to external setup
Maintenance
Focus on preventive maintenance Develop a total productive maintenance
system (TPM) Train and assign workers to carry out
preventive maintenance on their machines Provide technical assistance for workers Develop a set of measurements for
improving the maintenance system
Flexibility
Mobility
Variable output rate
Multipurpose
Flexible capability
Simplicity
Surge capacity
Transportation Strategies
Repetitive schedules
Mixed loads
Milk run
Freight consolidation
Local warehouses
Local suppliers
Implication of JIT in Repetitive Systems
Use production rates instead of work orders Gross-only explosions for MRP No lead-time offset is required Cumulative MRP format may be used No need for due dates on individual lots Planning buckets are usually in days or
weeks
Implications of JIT in Job Shop
Visual control of queues The level of BOM is reduced Manage the total load of the shop Use rate-based scheduling Use mixed-model scheduling Use cellular layout Emphasis part standardization
JIT in Purchasing
Basics:• Scheduling system producing reasonably certain
requirements.
• Achieving a stable schedule.
• Pursuing all JIT objectives and building blocks.
• Pruning the number of vendors.
• Controlling the cost of transportation. Lessons
• Don’t shift inventory-holding from the company to the vendor.
• Effectively manage vendor relationships.
Implication of JIT in Human Resources Management
Employee involvement and empowerment Motivation Suggestion systems Intra- and inter-functional teams Job design Compensation and rewards Education and training Relationships with unions
Changing Roles and Responsibilities - Management
Culture change – from maintain status quo to improvement
Supervisors as coaches Treat employees fairly Sharing information Provide support and motivation Provide extra time for improvement
Changing Roles and Responsibilities - Employees
Make decisions and solve problems
Help make improvement
Work with colleagues closely
Expanded job responsibilities
Responsibility at the source
Use scientific techniques
Concluding Principles
Stabilizing and in some cases leveling the production schedules are prerequisites to effective JIT systems.
Achieving very short lead times supports better customer service and responsiveness.
Reducing hidden factory costs can be at least as important as reducing costs more usually attributed to factory operations.
Implementing the whole person concept reduces distinctions between white- and blue-collar workers and taps all persons’ skills for improving performance.
Concluding Principles
Cost accounting and performance measurements need to reflect the shift in emphasis away from direct labor as the primary source of value added.
To achieve JIT’s benefits in nonrepetitive applications, some basic features of repetitive-based JIT must be modified.
JIT is not incompatible with MRP-based systems. Firms can evolve toward JIT from MRP-based systems, adopting JIT as much as or little as they want, with an incremental approach.
Homework Assignment
Problem 3.2 and 3.12
Due Tuesday, December 3
Recommended