A Lean Analysis Methodology Using Simulation February 20, 2009

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A Lean Analysis Methodology Using SimulationFebruary 20, 2009

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What is “Lean” / Why Simulation?

The term goes back to the Toyota Production System’s Just-in-Time techniques

Lean Manufacturing expanded to Lean Six Sigma & Lean Supply Chain: to optimize cross-functional processes

Simulation allows us to: Evaluate things other tools cannot, such as impacts of product mix and

setups, for complex operations with many products

Analyze impacts of variability in processes and demand, with real-world time sensitive parameters

Develop replenishment & inventory strategy across locations,

Analyze impacts of process and capacity changes on performance.


Simulate Replenishment Planning


Key Metrics Can Be Compared For Multiple Scenarios

Results of Multiple Simulations are

Compared on the Same Graph

Cycle Times

Inventory Levels


Repair Centers

Repair Centers

Case Study: Lean Simulation Model Test a New Demand Pull Process

ExtrusionLaminating

& cutting PackagingDemand60 +finished products

MRP Push 3 Passes on the same equipment

Limitedstorage space

5 days/week 7 days/week 7 days/week

Each work center operates on a different work schedule.

Before Model for Laminated Plastic Manufacturing Process


Lean Techniques in Model

KanbansOne-Piece Flow

EPEI (Every Part Every Interval) Constant Work In Process (CONWIP)

Batch Schedules

When to Authorize Production

DowntimeSetups / Changeovers

YieldScrap

Lead Times

Incorporate Variability

Setup ReductionShared Equipment Resources

Skilled LaborWork Center Schedules

Test Factory Changes

Takt Times / RatesOEE (Overall Equipment Effectiveness)

Cycle Times

Metrics


Pull Process: Scheduling & Structured Replenishment Rules

Repair Centers

CuttingExtrusion Laminating Packaging FillOrders

Triggered by KANBAN replenishment

Rhythm Cycle Product Group Allotment

LIGHT 80

LIGHT 55

LIGHT 25

FULL 80

FULL 55

FULL 25

5 days/week 7 to 6 days/week

7 days/week

Schedule to maintainCONWIP

EPEI Rhythm

Cycle

Tested & modified work schedule

Packaging is the constraint operation.

Repair Centers

CuttingExtrusion Laminating Packaging FillOrders

Triggered by KANBAN replenishment

Rhythm Cycle Product Group Allotment

LIGHT 80

LIGHT 55

LIGHT 25

FULL 80

FULL 55

FULL 25

5 days/week 7 to 6 days/week

7 days/week

Schedule to maintainCONWIP

EPEI Rhythm

Cycle

Tested & modified work schedule

Packaging is the constraint operation.

After Model with Best Practice Just-in-Time Techniques


“Every Product Every Interval” (EPEI)

EPEI Cycle Product Group Allotment

LIGHT 80

LIGHT 55

LIGHT 25

FULL 80

FULL 55

FULL 25

~60 total products; in 6 product groups

As demand arrives for each product, the production order is assigned to the next available cycle spot

Fairly complex setup rules between product groups

Make every product within this cycle: -Sets the maximum lead time-Dictates inventory turns & working capital


Before: throughput/service problem

Packaging operation is sometimes starved

Not meeting demand


After: Increased & consistent flow

Improvement in Packager utilization

Better Demand fulfillment


Some Real Benefits

Postponement strategy ( the Dell method ) - 30% inventory reduction; with service improvement to 97+%

Synchronized flow - reduced cycle time 18 to 13 weeks

Kanbans – inventory reduced 20% across a network

Demand pull – delayed need for major capacity upgrade

Focus on continuous improvement A traditional method such as value-stream mapping becomes

dynamic A model is a tool for kaizen teams and six sigma black belts


Hierarchical blocks for each plant or work

center

Each work-center has flow logic for

material, and schedule input

Each line has logic for each equipment set

Hierarchical Model Building

Excel interfaces for all inputs & outputs provides ease of use


Job Shop Simulation Model

Setup ProcessJobs from multiple sources

Each Job assigned a Job Type

Each Job Type creates a series ofJob IDs to be executed

Test ID Resource Requirements Skill Equipment Time Hold Time

10 3 101 4 hrs 24 hrs20 2 102 8 hrs 030 4 206 .5 hrs 6 hrs40 4 210 3 hrs 1 week

Each Job ID has parameters that define resources & duration

Skills Equip

Resources

Job Type Job Sequence Job IDs in the Sequence to be Performed. These Correspond to Job IDs in the Job ID to Resource WorksheetCode Nbr of Ops 1 2 3

2 3 10 20 303 2 20 304 1 405 3 20 10 40

Completed Jobs


Job Shop Example Statistical Outputs

Confidence intervals for results, e.g., end-to-end time

& utilization


A Takeaway

Documents

A Lean Analysis Methodology Using Simulation February 20, 2009