1 leveling: tortoise not hare. 2 ohno, 1988 the slower but consistent tortoise causes less waste and...
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Leveling: Tortoise not
Hare
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Ohno, 1988The slower but consistent tortoise causes less waste and is much more desirable than the speedy hare that races ahead and then stops occasionally to doze. The Toyota Production System can be realized only when all the workers become tortoises.
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The Leveling Paradox
The Leveling Paradox
Leveling provides a standardized core for Resource Planning Why do this to yourself ? Smoothing demand for upstream processes
How to Level Initial efforts to level production and mix Incremental leveling
Slice & Dice Product families and subfamilies
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Leveling: Core for Resource Planning
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ExampleCustomer Demand
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Heijunka1. Level, smooth production: product
volume
Customer Demand
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Monday Tuesday Wednesday Thursday Friday
Customer Demand
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Monday Tuesday Wednesday Thursday Friday
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Heijunka 2. Level, smooth production: product mix
Customer Demand
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Monday Tuesday Wednesday Thursday Friday
Rake Shovel Spade
Customer Demand
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Monday Tuesday Wednesday Thursday Friday
Rake Shovel Spade
Traditional production Level production
Rake Shovel Spade
Monday 100 50 25
Tuesday 100 50 25
Wednesday 100 50 25
Thursday 100 50 25
Friday 100 50 25
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Heijunka3. Level, smooth production: product
sequence
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Leveling High Variety Product Mix
High volume parts --> built-to-stock signal --> supermarket --> replenished by Kanban
Low volume parts --> built to customer order
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Why Leveling?
Problems: Small batches --> Frequent changeovers/change in material --> Lost production --> Missed schedule
Traditional solution: Large batches Less changeovers/change in material
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Why Leveling?
Toyota solution: Lifting the “cloud” Setup time reduction (SMED)
Increased flexibility Level material demand
Read Toyota Atsushi Niimi Interview
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Cell Design
Tool for one-piece flow
Cell: Group of workstations, machines or equipment arranged such that a product can be processed
progressively from one workstation to another w/o waiting for a batch to be completed and w/o additional handling between operations
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Traditional Layout
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Lean Cell Layout
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U-shaped Cell Example
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Designing Cells1. Group similar products into families that can be
processed on the same equipment in the same sequence
2. Calculate takt time
3. Determine the work elements and time required for making one piece
4. Determine equipment cycle time
5. Organize machines in order or processing (U-shaped)
6. Balance the cell
7. Determine how the work will be divided among operators
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Manage Change Process
Operators Crosstraining Job rotation Solve production problems Improvement suggestions Plan coordinate, and control their work Group setting
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Manage Change Process
Managers Planning Supervisors
Accounting
Reward system
Plan for demand changes
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Advantages Decreased
Transportation Waiting time WIP Floorspace Lead time
Increases flexibility (Variety and customization)
Better communication between operators --> improved quality and coordination
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Value Stream Mapping
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What is Value Stream Mapping
Value stream: Actions required to bring a product through the main flows essential to every product: Production flow from raw material to customer
delivery Design flow from concept to launch
Information flow as important as material flow
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Using the Mapping Tool
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Current-State Map
Material Flow Icons
General Icons
Information Flow Icons
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Material Flow Icons 1
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Material Flow Icons 2
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Information Flow Icons 1
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Information Flow Icons 2
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General Icons
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Characteristics of a Lean Value Stream
Produce to your takt time Takt time= rate of customer demand
Develop continuous flow wherever possible
Use supermarkets to control production where continuous flow does not extend upstream
Try to send the customer schedule to only one production process
Level the production mix
Level the production volume
Develop the ability to make “every part every day” (Level production sequence)
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The Future-State Map Goal:
Built a chain of production where the individual processes are linked to the customer and
Each process gets as close as possible to producing only what its customer needs when they need it
First pass: What can we do with what we have?
Later: Address product design, technology, and location issues
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Key Question for Future-State Map
Will you build to a finished goods supermarket from which the customer pulls, or directly to shipping?
What is the takt time?
At what single point in the production chain will you schedule production
Where will you need to use supermarket pull systems in order to control production of upstream processes
How will you level the production mix
What increment of work will you consistently release
What process improvements will be necessary
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Future-State Mapping Example
ACME Stamping Stamped-steel steering brackets
Hold the steering column to the body of a car Two versions: Left-hand side and right-hand-side
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Achieving the Future-State Map
Plan for achieving future-state map Future-state map Any detailed process-level maps or layouts that
are necessary A yearly value-stream plan
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Breaking Implementation into Steps
Divide into value-stream loops The pacemaker loop
Flow of material and information between your customer and your pacemaker process
Most downstream loop Impacts all the upstream processes in the value
stream Additional loops
Between pulls Each pull-system supermarkets separate loop
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The Value-Stream Plan
Shows: Exactly what to do when, step-by-step Measurable goals Clear checkpoints with real deadlines and
named reviewer(s)
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Determine Starting Point
Look for loops where: Process is well-understood by people Likelihood of success is high Big bang for the buck
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Improvement Pattern Develop a continuous flow that operates based
on takt time
Establish a pull system to control production
Introduce leveling
Practice kaizen to continually eliminate waste, reduce batch sizes, shrink inventory, and extend the range of continuous flow
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Conclusion
VSM cycle not one-time activity
Heart of day-to-day management
Serve the customer
Change in people
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Homework
Develop Future State Map for TWI
Due: 03/02/09 Before class
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