Lean Manufacturing & JIT

8/8/2019 Lean Manufacturing & JIT

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Lean Manufacturing &JIT Production


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Just-in-time- A philosophy for optimizing performance of amanufacturing system.

- Originated from work of Taiichi Ohno at Toyota.

- After WWII, U.S needed large mass production tosatisfy demand for products.

- Japanese market was much smaller, so moreflexible systems were needed to produce smaller quantities of different items in the same equipment.


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Just-in-time After many years, Toyota established the followingstrategy:

1. Kanban based pull production.

2. Waste elimination is guide philosophy.3. Faith in importance and value of quality.4. Kaizen or continuous improvement as a daily

strategy.

5. Emphasis on setup reduction on all machines.6. Integrate suppliers and material acquisition intothe planning process.

7. Cellular layouts with balanced flow.


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Comments about Kanban - JIT

Note that Kanban systems are not the same as JIT.

The pull approach is only one aspect of the JITphilosophy.

The combination of the above factors transforms theshop into a lean facility.

They factors depend on one another.

A Kanban system without high quality or low setups

will not achieve expected benefits.


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B asic Tenets of Lean, JIT Production

CategoriesImp roving Production Environ ment

Quality Engineering

Imp roving Material Flow


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I. Improving Production Environment

1. Eliminate Waste

2. Employee Cross-Training and Job Rotation

3. Employee Empowerment and Involvement

4. JIT Purchasing

5. Reduction of Variability

6. Mistake-Proof Processes

7. Reduce Setup Times


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Some Terminology

Muda: Japanese term for any human activity which

abosrbs resources but creates no real value.

K aizen: process of continuous incremental improvementthrough the identification /elimination of m uda.

K aizen blitz: an event where a team of managers,

engineers and line workers coordinated by a facilitator

come together for three days to focus on improvements

on an area of a plant.


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Some Terminology

Typical strategy in Kaizen Event is asking why five

times until the root cause or motivation for an action is

discovered.

Golden Rule: Use everyones knowledge to identify and

implement improvements quickly and cost effectively.


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1. Eliminate Waste

Original scientific approach was to dissect a large system

into small pieces and make each piece optimal.

Japanese approach: develop a system that connects the

pieces.

Ex. Instead of tracking production statistics and

inspecting out defective products, eliminate any

production of defective items.


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Seven Types of Wastecommonly found in industry.

A . Waste fro m Overproduction

Why make products that wont be sold?

Before, supervisors were evaluated through quotas.

Machine utilization needed to be maximized.

New idea: machines and humans should only be busy

when they have useful tasks to accomplish.


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B. Waste of Motion

Eliminate motions that do not add value.

Look at workplace design, process planning,

detailed job procedures, material handling.


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C . Transportation Waste

Position work and storage areas such that

material moves are short.

Keep tooling near its point-of use.


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D . Processing Waste

Eliminate non-value added operations.

May need to go back to product design and

revise features and tolerances.


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E . Wasted Ti m e (queuing)

Plan for:

Small lot sizes

Ordered production and release of dependent Items

Good coordination will achieve small WIP and

throughput time.


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G . Ex cess Inventory yields added costs due to

Space, obsolescence, opportunity costs, handling, among

others.

Avoid excess inventory.

Can achieve via modular components.

Negotiate long term contracts with suppliers to ensure a

steady stream of high-quality parts.


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Can train over time to do variety of tasks in their work

area.

Can then rotate through different positions.B enefits:

Enhances worker flexibility and enthusiasm.

Prevents boredom, fresh perspectives and ideas for improvements.

Gives context of communication between workers on

same team.


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B enefits (continued):

Minimizes fatigue and repetitive stress injuries.

Can move workers around to eliminate temporary

bottlenecks.

In U-shaped cells, workers can operate more than onemachine at a time.


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3. Employee Empowerment andInvolvement

Why hire a body when it comes with a brain?

Employees are a great source of ideas for

improvement.

Employees must be allowed and encouraged to

do so.

This includes authority to stop production andcorrect a problem in production.

The goal is to identify problems early.


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A usual approach to empower is via a switch to stop

production.

This warning system is called J ikoda .

The warning light system is called andon .

Usually a bank of three lights is used: green , yellow and

red .


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One light is always on, indicating station status.

Red light signals a line stoppage and location of

problem to other workers. Nearby workers assist with the problem, get

additional help if necessary.

Identifier and solver of problemare rewarded.


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Employees should be involved in developing

procedures.

Workers take pride in job if they know they arehelping meet customer expectations.


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Worker area should also be kept clean and organized.

This helps in pride and dedication.

5Ss:

Sort, Straighten, Sanitize, Sweep and Sustain.

Organized workplace reduces:

Misplacing

Contamination

Brightens up atmosphere

Gives feeling system is under control.

Conveys that sloppiness is not tolerated.


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4. JIT Purchasing

Changes that can be implemented

1. Sole source vs. multiple supply sources.

- Idea: better negotiate long-term contracts with single

supplier.

- This encourages cooperation instead of competing over

terms.

- Suppliers long term interest is now to provide high

quality on time at a fair price to ensure customers

success.


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4. JIT Purchasing


2. Frequent delivery of small lots vs quantity discounts.

- Traditional approach: occasional deliveries of large

quantities of parts.

- Parts were inspected via sampling.

-Now, no inspection is needed since vendor product

quality has been certified and meets requirements. (If

not, get a new supplier).


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4. JIT Purchasing


3. Flexible ordering vs. paperwork.

- Contracts usually call for steady flow of product +/-

10%

- Customer can change order quantity on short notice

with little hassle.

- Requires some reserve capacity by vendor.


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4. JIT Purchasing


4. Vendor owns and manages inventories.

-Vendor can hold inventory on customers site.

- Customer gets billed only when extracting parts.

- Supplier has responsibility to keep enough inventory

level.


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5. Reduction of Variability

Variability reduces efficiency.

If supplies, yields or machine availability are

unpredictable, the tendency is to have large safety stocks

of inventory.

Idea:

Eliminate variability from production processes.


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This involves eliminating opportunities for errors.

Idea:

Design processes to avoid producing defective items.

Be able to detect defects before more production steps

are done.

Poka-Yoke: mistake proofing a process.


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Basic ideas:

100% of units should be inspected.

Identify defects as close to the source as possible.

Stop production immediately and take corrective action

right after a defect is detected.

Design processes to avoid producing defects.


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Some Poka-Yoke Techniques

Checklists and worker source inspection.

Worker checks his own work.

Problem: humans tend to approve their own work.

Checklists help ensure all steps have been completed

in station.


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Successive check systems

Worker checks incoming parts from previous station

before starting his own operation.

Worker must approve work by previous worker or

defects must be communicated to previous worker

right away.


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Mistake-proof part and fixture design.

Design parts so that they can only fit in a tooling

fixture in proper orientation.

Reshape symmetrical parts to exaggerate

asymmetries easier to detect misalignments.


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7. Reduce Setup Times

Usually the MOST productive investment that can be made toimprove production system performance.

Techniques (*):

- Design parts for manufacturability

- Design parts for standard tools.

- Develop standard methods for setups.

- Divide setup activities into external/internal tasks.

- Design procedures to perform setup tasks in parallel.

- Modular fixturing

- Eliminate adjustments.

- Use power clamps.


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Transitioning from Traditional to Lean

1900s Philosophy

Worker was immigrant, uneducated, spoke little English.

Worker is like a machine designed to perform a limited set of

tasks well.

Product customization was not an issue for customers (all model

Ts were the same).

2000 Lean Philosophy

Worker: most flexible machine.

If properly educated, worker can solve problems and adapt to

new situation.

The customer expects customization.


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Old Production Mentality:

Process-Based Organization

Economic Order Quantities

Large Unit Handling Loads

Receiving Inspection

Maximize Equipment Use


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New Lean Thinking

Product Cell Layouts

Single-Unit mixed model production

Continuous material flow

Mistake proofing

Balanced production line


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Problems in Implementing Lean

Cannot make it happen without the support of floor operators.

Culture change needs to happen.

Old philosophy: run large batches to amortize setup costs of the

largest number of parts and products.

New philosophy: demand based production.

Management not fully involved.

Loss of interest by top management and workers.

After initial implementation, no hard benefits seen in bottom

line.

Might have implemented Lean in wrong areas.


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Pros & Cons of Cell Manufacturing

ProsShorter Lead times

Reduced WIP

Space Savings

Higher Quality End Product

B etter team

communications

Employee ownership and

can do attitude

Supports pull operation

ConsLower equipment utilization of non-bottleneck cells.One piece of the cell breaksdown, the whole cell is out (noredundancy of equipmentwithin a cell)Loss of employee dedicatedexpertiseIf demand falls and cell outputis below cell capacity, per unitcosts are higher.Multi-product cells may not besuitable for higher volumeorders, becoming thebottleneck.


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Transition Stages in Lean Thinking(Ford Motor Company)

Phase 1: Process Stabilization

Improve production environment; predictable/reliable processes; total

productive maintenance, total quality, poka-yoke, setup time reduction,

standard procedures, clean & organize the workplace. Train employees

in lean thinking.

Phase 2: Continuous FlowReduce WIP and batch sizes. No need to run machines at full capacity.

Unit parts can plow in small or single quantities between workstations.


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Transition Stages in Lean Thinking(Ford Motor Company)

Phase 3: Synchronous production.Follow weekly production schedules.

Phase 4: Pull authorizationTo authorize production, parts must be pulled by successive

workstations. Kanbans dictate production.

Phase 5: Balanced productionAll process produce at a constant level and continuous rate.

Every part type is made daily; parts flow continuously.


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Short Articles on Lean Implementations

www.sme.org

Manufacturing Engineering Magazine

September 2003 Issue

Lean by Design and by Necessity

http://www.sme.org/cgi-bin/get-

mag.pl?&&03sem002&000007&2003/03sem002&ARTME&SME&

Lean pays Off at Ariens

http://www.sme.org/cgi-bin/get-

mag.pl?&&03sem005&000007&2003/03sem005&ARTME&SME&

Documents

Lean Manufacturing & JIT