imple me ntation of zero defect through poka yoke … · imple me ntation of zero defect through...

IMPLEMENTATION OF ZERO DEFECT THROUGH POKA YOKE APPROACHES

IN THE ASSEMBLY LINE OF COMPRESSOR MANUFACTURING INDUSTRY

1Dr.R.Vinayagasundaram,

2Dr.C.Velmurugan,

1Associate Professor, Department of Management, Kumaraguru College of Engineering,

Coimbatore, Tamil Nadu, India,

2Professor, Department of Mechanical Engineering, Kumaraguru College of Technology,

Coimbatore, Tamil Nadu, India

[email protected]

ABSTRACT

Any company, to survive in this competitive world must have known the importance

of reducing the operational cost. It can be further explained in the way that Operational cost

of a company has an inverse relationship with the profit return of the Company. Having

business is different from earning profit out of it. Hence, to earn profit out of business, the

only direct and effective way is to reduce operational cost. Operational cost not only incurs

machine, material and manpower costs but also rejection and reworks cost which is hidden

and severely affects the reputation and profit of the business, once taken place. This has been

understood by many business experts and researchers all over the world and started

introducing many techniques like Kaizen (Continuous improvement).Lean manufacturing,

Total Quality Management, Total Productive maintenance, Zero Defect, Six sigma, Just-In-

Time, 7 quality tools, Robust design, SS, 7 Midas and so on.One among these techniques is

“Poka-yoke” which means “Mistake proofing”. This is considered to be the most cost and

time effective technique to reduce RPN, reworks and rejections. The concept of mistake

proofing explains us that employees are not only the reason for errors happening in the

workplace, it is the system that should provide aplat form where there is no chance for the

employee to make errors.

Keywords: Lean manufacturing, Total Quality Management, Total Productive maintenance,

Zero Defect, Six sigma, Just-In-Time, Poka yoke and Kaizen

International Journal of Pure and Applied MathematicsVolume 119 No. 17 2018, 2319-2332ISSN: 1314-3395 (on-line version)url: http://www.acadpubl.eu/hub/Special Issue http://www.acadpubl.eu/hub/

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1. Introduction

„Poka Yoke‟, otherwise called „Mistake Proofing‟ is the mechanism used in thisproject

to reduce rejection and rework percentage. Poka-yokes ensure that proper conditionsexist

before actually executing a process step, preventing defects from occurring in the firstplace.

Where this is not possible, poka-yokes perform a detective function, eliminatingdefects in the

process as early as possible. Naturally, this technique has the economicalcharacteristic of

“sow less, reap more‟. It is found to be reliable and produces great resultsin

processes.Developing Zero Defect through Poka Yoke approaches helps to improve assembly

quality during two stages of their production assembly design: early design of tasks, fixtures

and tooling; and during early ramp-up of new assembly lines at outsourcing sites.

Researchers worked in an action research approach with company engineers and ergonomists

to integrate PokaYoke into both design stages. This reseaqrch paper presents the Poka Yoke

approaches and discusses the challenges of using Poka Yoke to improve assembly quality.

For the first stage of early design, a Poka Yoke-design for assembly operation which has

higher RPN values (200-500 RPN). Items included physical risks, such as grip size and force,

movement risks, such as re-grasping or re-orienting, visual risks, such as visual accuracy and

inspection difficulty, and cognitive issues such as ability to detect a problem and risk of

damage to part or component. High RPN were associated with assembly tasks that were both

reported as difficult by operators, and also had quality problems.

The Process Document (PFC, PFMEA, QC, and SOP) was adopted as a controlled

engineering document and used to proactively score assembly tasks prior to final design of

tasks, fixtures and tooling. has been linked to assembly quality. PokaYoke approaches were

developed to help improve quality in early design stages and during early ramp-up of

assembly lines. Companies are encouraged to develop and evaluate Poka Yoke approaches

for improving assembly quality.

2. Need and Scope of the Study

In compressor manufacturing industries the major problem is during assembly and

mistakes occurs and which needs rectification.Based on defect prevention analysis and

monitoring of each activity in the process and implementation of Kaizen and Poka yoke at

each stage of the process safeguards against appearance of a problem. Poka-Yoke technique

International Journal of Pure and Applied Mathematics Special Issue

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can be applied both to prevent causes, which will result in subsequentoccurrences of errors

and to carry out inexpensive control determining whether to adopt orreject the product. It is

not always 10 % probability elimination of all errors, in such casesit is the task of Poka-Yoke

methods is detection as soon as possible.

3. Objective of study

Primary objective:

The main objective of the research is to help produce zero defect products, i.e.

improving product and process quality by implementing preventive tool - Poka Yoke.

Secondary objective:

In order to provide a logical approach to the RPN reduction the following objectives are

set up for this study:

To provide an extensive Poka-yokemethodology and problem solving models

To provide recommendations for zero quality failures based on the development of

PFC, PFMEA, Control Plan, SOP and then finally implementing principles of Poka-

yoke methodology

To develop a prototype for the systematic utilization of mistake-proofing efforts in

EPSAC S1 line.

4. Research Methodology

Defects Data Collection

Through the above research instruments both primary and secondary data are

collected forin-depth analysis of the problem domain. Since quality related issue takes place

in the shopfloor, high attention given to data received from shop floor process,

productiondepartment and quality department.

Primary Data Source

Primary data are collected through observation in assembly line, brainstorming

sessions, hourly PDCA, 90 days customer complaint and even through the reports from

quality assurance team like IPRR (In-Process Rejection Report), CAPA (Corrective

andPreventive Action report).


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Secondary Data Source

The existing defects stored in defects management system, literature reviews, articles

and web sources regarding assembly line defects and Poka yoke implementations for various

defects based on RPN considered to be the secondary data sources for thisproject.

ProcessFlow Methodology/Methodology of Poka yoke

Identify problem from DMS

Observation at work stations

Brainstorming for ideas

Select best ideas

Implementation plan and implementation

Analysis and Interpretation

Analysis of Risk Priority Number

These are defects incurred in the assembly line whose Risk Priority Number

valuesscale ranges from 400 to 600 hence special preference is given to reduce these

defects.

Based on the defects data the RPN values with higher priority are scaled.

420

420

420

480

448

560

480

500

400

400

400

400 420 440 460 480 500 520 540 560 580

Human error

Operator ignorance

Torque not defined

Human error

Operator ignorance

Process in consistency due to tolerance stack up

Torque facility not available

Torque not defined

Human error

Lifting facility not available

Operator ignorance

Torque not defined

(blank)

67

81

0

(bl

an k)

RPN

De

fect

s (S

tage

Wis

e)


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Defects with high RPN

These are defects incurred in the assembly line whose Risk Priority Number values

scale ranges above 150

Process with higher RPN

The idea is to decide that the defects in assembly line mainly occur due to Operator

ignorance such as wrong assembly process, missing operation, handling damage and Torque

not define for tightening issues.

Analysis on Pick To Light

Process Flow

Problem Description

In the moisture seperator O ring missing occurs periodically and reason behind this

operator ignorance that was suspected to the reason behind .The above description is the O

ring missing which results in frinction in moisture seperator. above is the case of breakage

and associated cost which also increases operational cost. G. Vishnuvardhan Rao ,

Madhusudhana Reddy Barusu ,Praveen Kumar.E, Sakana.G (2017) Hence, for root cause

71 62

28 26

6 4

0

20

40

60

80

Wrong Assemblyprocess

Tightening Issues Missingoperation

Thread sealentapplication

Fittment issues Handlingdamage

Failure mode category above 150RPN

Tightening of flange coupling with MOD

Fixing flange coupling on MOS

Applying grease on ‘O’ rin g way in flange coupling

Placing MOS in fixture


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analysis of this problem, one of the seven qualitytools that is Fish Bone diagram and 4M-

4WHY is used and then planning to apply poka yokemechanism for it.

Cause

And

Effect

Diagra

m:Analy

sis and

Intrepre

tation

The O ring missing defects which occurs frequently in the shop floor due to various

reasons such as taking wrong O ring, Human intervention, wrong grades of grease and O ring

not properly placed.

4M-4WHY

Analysis on Scavenging pipe length


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Process Flow

4.1.2.2 Problem Description

In the F3, F4, F5 Scavenging pipe length variation occurs periodically and the reason

behind this reffering wrong part drawing for measuring, error in supplier quality, error in

measuring instruments, improper communication with supplier these could be the reasons

behind .The above description results in oil carry over in moistue air seperator. The leakage

and associated cost which also increasesoperational cost. Hence, for root cause analysis of

this problem, one of the seven qualitytools that is Fish Bone diagram and 4M-4WHY is used

and then planning to apply Poka yoke mechanism for it.

4.1.2.3 Fish Bone Analysis & Interpretation

Fixing scavenging pipe and filter in tank

Measuring the distance

pre-setting of measuring instruments

placing Scavenging pipe


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4M-5WHY Method

The Scavenging pipe length variation defects which occurs frequently in the shop floor due to

various reasons such as referring wrong part number while measuring, error in measuring

instrument, defects in supplier, improper communication with supplier which leads to

variation in length of scavenging pipe.

4.1.3 Analysis on Motor Connection Testing

4.1.3.1 Process Flow:


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Problem Description

The motor wire wrong connection occurs periodically and the reason behind this wrong

connection between the terminals, error in supplier quality, no proper testing mechanism,

variation in wire length, wrong control panel connection these could be the reasons behind .

The above description results in major damage in Air Compresssor.Which also

increase in cost. Hence, for root cause analysis of this problem, one of the seven quality tools

that is 4M-4WHY is used and then planning to apply Poka yoke mechanism for it.

4M-5WHY

Covering the top plate of motor wiring and tightening

Placing nuts in wiring box and tightening

Fixing motor wire terminals in wiring box

Removing nuts in motor wiring box

Inserting Motor wire terminals in motor wiring box

Opening the top plate of Motor wiring


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The trial and error method is not efficient for motorcontinuity testing and the operator should

be very keen in connecting the wire terminals

Findings

Missing of operation in assembly

The missing of operation is due to operator ignorance which could frequently occur in

Station 1, 6, 7 and in Testing. By leaving an operation possibly occur defects in both short

and long run. It is also consist of higher RPN values

Power wiring at motor

The motor wire wrong connection occurs periodically and the reason behind this wrong

connection between the terminals, error in supplier quality, no proper testing mechanism,

variation in wire length, wrong control panel connection these could be the reasons behind .

Implemention of Pick to light mechanism

Pick-to-light systems organize products to be picked in rows and columns, with the

products supported in boxes or containers, for example, in flow racks. Pickers or operators

are prompted by lights (hence the name pick-to-light), which are illuminated one at a time to

indicate which product is to be picked. In response to the light, the operators pick and place a

product in a tote that is supported in front of the flow rack. When the product is picked

sequence is activated and it moves to the next bin for picking product. Another light will then

be activated to indicate when another product in that picking location is to be picked.

Poka yoke Implementation

When this pick to light mechanism implemented the missing operation will be

reduced in all stages leads to decrease in overall RPN level.


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Working of Scavenging Pipe

By using ultrasonic sensor, the distance between top and bottom edge of scavenging

pipe can be measured. The sensor was placed at the movable nylon plate(fixture) and

scavenging pipe was placed at the base of the fixture, the sensor will transmit sound waves, it

will hit the flange and it get received by the receiver of the sensor by which the distance can

be measured. Here ultrasonic sensor can be controlled by Ardunio (microcontroller).

Ardunio controller was pre-programmed by PC (Ardunio software). The output of measured

values are displayed in LCD display.

Causes Time increases due to the usage of height vernier gauge for measuring the length of

scavenging pipe.

Poka yoke implementation:

Scavenging line fixture

The accurate distance could be measured by using this Poka yoke hence the complaint

which arrived in 90 days has been eliminated

Implementation for motor testing kit

By connecting 6 terminals of motor with copper wire by using fixture.The copper

wire was connected with battery and LED. If the continuity of pair of terminals are

connected, LED blinks green. If it is mismatched, LED blinks red.

Causes; Wrong wiring connection (human error)

Thermal block positioning fixture


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Working of thermal block fixture

Placing the thermal block in the fixture to guide the correct orientation. Based on that

thermal block, it can be connected with tank.

Causes

Increasing time while using sprit level. Wrong orientation may occur (human error)

Fixture implemented:

Thermal block fixture

5. Conclusion

This research study was to define ways and methods how totackle against continuous

and increasing number of quality failures. For this purpose the Poka-yoke methodology was

chosen. In the organizational point of view raising mistake-proofing efforts as a

commonconcept in Elgi of utmost importance. It is not only a method for production

andquality departments but also for other interest groups to start thinking in a

preventivemode in quality related issues.Methodology is just one among many others quality

control techniques. Bestresults in quality improvement activities can be achieved by

combining best practicesfrom different methods and applying lean manufacturing tools and

techniques

6. Bibliography

1. Anil S. Badiger, R. Gandhinathan, V. N. Gaitonde, Rajesh S. Jangaler

“Implementation of Kaizen and Poka-yoke to Enhance Overall Equipment

Performance - A case study”


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2. 9th CIRP Conference on Intelligent Computation in Manufacturing Engineering -

CIRP ICME '14 -Zero Defect Manufacturing: Detection of Cracks and Thinning of

Material during Deep Drawing Processes - Dr. rer. nat. Antje Zoescha, Dipl.-Inf.

Thomas Wiener b,Dr.-Ing. Michael Kuhlb

3. 8th CIRP Conference on Intelligent Computation in Manufacturing Engineering -

Monitoring systems for zero defect manufacturing submitted by S. Ferrettia, D.

Caputoa*, M. Penzaa, D.M. D‟Addonab.

4. 2016 International Conference on Industrial Engineering and Operations Management

,Detroit, Michigan, USA, September 23-25, 2016© IEOM Society International - A

guideline of quality steps towards Zero Defect submitted by M.Sc. Ragnhild J.

Eleftheriadis, Dr. Odd Myklebust.

5. G. Vishnuvardhan Rao , Madhusudhana Reddy Barusu ,Praveen Kumar.E,

Sakana.G,” Comparative Analysis Of Eye Detection And Tracking Algorithms For

Surveillance”, International Journal of Pure and Applied Mathematics , vol 117, No.

22 - 71-75, 2017.

6. Towards zero-defect manufacturing (ZDM)—a data mining approach submitted by

Ke-Sheng Wang - Received: 10 July 2012 / Accepted: 12 October 2012 / Published

online: 14 March 2013 ,Shanghai University and Springer-Verlag Berlin Heidelberg

2013.


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