Question

own777

value_stream_mapping_plus_lecture.ppt

Home >Business & Finance homework help >Management homework help >Question

Value Stream Mapping Plus

Learning to See Better

Know the Laws. Use the Tools. Profit.

www.factoryphysics.com

Databases:
FPI: LTS Current State

FPI: LTS Future State

Agenda

Overview
The basic steps

Choose a product flow

Create VSM & Current State Model

Validate model

Modify Current State model to get to optimal Future State

Implement cost effective improvements

VSM Plus Example
Review

Value Stream Mapping Plus

Mapping and understanding the flow of
Materials
People
Information

Plus Absolute Benchmarking and Optimization
What is current, best and marginal case performance
What is the source of variability and buffers
What is the optimal future state for your environment

The Value Stream

Two essential components

Demand

Transformation

Buffers develop when variability is present.

Only three buffers:

Inventory

Time

Capacity

A value stream is “lean” if it uses minimal buffering cost.

Production

Assembly

Distribution

Market Demand

Flow

Stock

Flow

Stock

Market Demand

Planned Demand

Where to Start?

If Design is done well, Planning becomes easeier.

If Planning is done well, Execution becomes easier.

Value Stream Mapping Plus is a practical application for value stream design analysis and improvement.

The basic steps are …

Choose a product flow in the value stream.

Develop current state map and model based on existing conditions.
Must validate that model reflects reality

Create a future state model and map to reach goals for improved performance.

Choose a Product Flow

Only a few
Part numbers make up most of the demand
Process centers are potential bottlenecks
Sources of variability really hurt

A Product Flow is a generic routing in which
Most parts follow essentially the same routing
Parts can go out and return
Parts can start inside
Parts on same level in a bill of material

Current state model

Walk-through of process to identify the pointless buffers
Where is the obvious waste?
Where is the time?

Draw value stream map to show:
Process Steps
WIP
Information Flow
Cycle Time

Current state model (continued)

Collect the following data for each Item and Process in the flow:
Number of tools needed
Number of workers needed for setup; needed for process
Process rate
Setup (changeover) time
Availability (MTTR, MTTF)
WIP
Scheduled time available
Transfer and Process Batch Sizes

Current state model (continued)

Use Flow Benchmarking to identify opportunities
Throughput (customer demand)
Work in process (WIP)
Raw Process Time (RPT)
Bottleneck Rate (BNR)
Critical WIP (CW = RPT * BNR)

Current state model (continued)

Process Debugging
Often model runs much better than actual system
Try to make the model run as poorly as the actual system
Can often make improvements by reversing the changes

Future state model

Use analysis tools and look for:
Utilization > 95%
Raw Process Time / Cycle Time ratio < 30%
Long, infrequent outages
High yield loss downstream causing high utilization upstream

Future state model (continued)

Consider optimization tools to determine
stocking levels
lot sizes
WIP/cycle time for given demand
product mix

VSM+
Example

Two brackets (L, R)
18,400 p/mo
Current cycle time is 23.6 days
Value added time is 188 sec

NOTE: This material is taken from LEI source material and belongs to Lean Enterprise Institute, Inc., who owns its copyright, and is used here with permission.

Current State Map (see handout)

Source: Lean Enterprise Institute

The basic steps are …

Choose a product flow in the value stream.

Develop current state map and model based on existing conditions.
Must validate that model reflects reality

Create a future state model and map to reach goals for improved performance.

Basic Factory Physics Model

Items represent Demand that follow a Product Flow through a Plant

Plants are composed of
Product Flows
Stock Points

Schedules relate Demand time to Plant time

Basic Factory Physics Model

Product Flow composed of
Routings assigned to Items containing

Steps involving

Process Centers (machines)

Work Groups (people)

Stock Point: where inventory accumulates between Flows

Data elements for any model

This data is available for company (or it wouldn’t be in mfg.)

Throughput > Bottleneck Rate (BNR)

Utilization > 100%

Something’s Wrong!

Could not meet demand in time allowed

Is actually clear from data …
Demand = 18400 units per month
7.67 h/s * 2 s/d * 20 d/m = 306.67 h/mo
= 18400 minutes per month
Takt time = 60 sec
Assembly # 1 takes 62 sec

Add More Time

Increase time available until we match observed cycle time

Requires 17.6 h/d that includes some overtime

Check Demand Analyzer again.

In practice, this validation is done by asking, “Why?”

Why does the data given provide results that are not reflected in reality?

Throughput < Bottleneck Rate (BNR)

Utilization < 100%

Flow benchmarking

TH	920	Brackets/day
WIP	21,730	Brackets
BNR	1,021.85	Brackets/day
RPT	.0653	days

Current TH and CT are on the marginal case

Fat zone

Lean zone

A high-level design assessment – too much WIP.

The basic steps are …

Choose a product flow in the value stream.

Develop current state map and model based on existing conditions.
Must validate that model reflects reality

Create a future state model and map to reach goals for improved performance.

Drill down on the components of cycle time

To get the components of cycle time for a product

Time factor is the largest component of queue time

Drill down into Batch Cycle Time

Batch Time is the largest component

What if we reduce the process batch to 200 for each product?

Cycle Time reduced from 25 days

Is there still room for improvement?

Future state modeling

Saw that Batch size was big driver of cycle time.

Reduced batch size with huge improvement in cycle time

What about the additional setups?

No setups at Assembly #1 so increased setups did not affect throughput.

Assembly # 1 is still the bottleneck

Balance Assembly #1 and #2

Current Processing Times
Assembly # 1 = 1.03 min
Assembly # 2 = 0.67 min

Average Processing Time = .85 min
Average Process Rate = 70.59 units/hr

Balancing the two lines adds more time (waste?) to Assembly #2. Is it worthwhile?

Change Process Rate on Assembly # 1 and Assembly # 2

Cycle Time reduced from 2.17 days

The rebalancing of the Assembly work station increased output and the bottleneck moved.

Weld #2 becomes bottleneck

Bottleneck rate increased from 1021 units/day.

BNR WENT UP, NEW BN BECAUSE STAMP HAS SHORTER SETUP TIMES

Can we improve the availability?

Reduce MTTR from 7.2 to 3 hours

Availability increases by about 10%

Cycle Time reduced from 1.85 days

We continue …

Stamping has a large setup time of one hour.
Lets decrease it by ½ and see what affect it has on the cycle time

Reduce setup time to 0.5 hrs

Cycle Time reduced from 1.27 days

We continue …

We already decreased the process batch size to 200.
Lets decrease it again by ½ and see what affect it has on the cycle time.

Reduced from 10 to 5

99% reduction of Cycle Time and WIP

Capacity has increased 9% from 1,021.86 units/day

Recap Improvement Steps

Reduce batch size to 200

Balance Assembly #1 and #2

Reduce MTTR at Weld #2 to 3 hrs

Reduce setup at Stamping to 0.5 hr

Reduce batch size to 100

Recap Results

Cycle time reduced 99%
Customer service should increase
Raw material inventory should decrease

WIP reduced 99%
Should reduce scrap
Should improve quality

Capacity increased 9%
Reduce overtime or take on more demand

Sounds good but here’s where the “rubber meets the road.”

The basic steps are …

Choose a product flow in the value stream.

Develop current state map and model based on existing conditions.
Must validate that model reflects reality

Create a future state model and map to reach goals for improved performance.

Implement the most cost-effective improvements

Implement Improvements

Reduce batch size to 200.

Policy change – minimum expense

Balance Assembly #1 & #2

Standard work design – minimum expense

Reduce MTTR at Weld #2 to 3 hrs.

SMED approach to repairs, maybe stock replacement parts – moderate expense

Day to day management decisions clarified, prioritized.

Implement Improvements (continued)

Reduce setup at stamping to 0.5 hr.

SMED techniques – cost depends heavily on type of changes required to achieve reduction, e.g. setup carts vs. new fixtures.

Reduce batch size to 100

Policy change – minimum expense

Focused effort, predictable results.

The basic steps are …

Choose a product flow in the value stream.

Develop current state map and model based on existing conditions.
Must validate that model reflects reality

Create a future state model and map to reach goals for improved performance.

Implement the most cost-effective improvements

Review

Value Streams are composed of Demand, Transformation and Buffers.

There are only three buffers for addressing variability

The three buffers are:
Inventory, Capacity and Time
It’s “pay me now or pay me later”

Review (continued)

LeanPhysics Tools provide applications for optimizing each of the three buffers.

We worked with practical optimization of the WIP/Time and Capacity buffers.

Optimization of the Inventory buffer covered by the Stock Optimizer.

Review (continued)

Advantages of analytic modeling over Value Stream Mapping
Provides additional information building on VSM
Can easily handle multiple products and complex flows
Much faster than VSM for initial analysis
Provides financial optimization capability

Review (continued)

Advantages of analytic modeling over simulation:
fewer data requirements
quicker
enables iteration to narrow down options if simulation required later