design & development of poka-yoke system for nut
TRANSCRIPT
DESIGN & DEVELOPMENT OF POKA-YOKE SYSTEM FOR NUT
IDENTIFICATION TO DEFECT PREVENTION
SARAH FATHIAH BINTI ALI
Thesis submitted in fulfillment of the requirements
for the award of the degree of
Bachelor of Manufacturing Engineering
Faculty of Manufacturing Engineering
UNIVERSITI MALAYSIA PAHANG
JUNE 2013
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ABSTRACT
Poka-yoke is a method in a lean manufacturing process that use sensor or other devices to
avoid and eliminate product defects by preventing, correcting or drawing attention of
human errors. The aim of this project is to design, develop and analyze Poka-yoke system
for nut identification to defect prevention. The development Poka-yoke systems start with
construct programming using Arduino IDE software and microcontroller ATmega328 is
used as interface between the system and hardware. Next process is to build and implement
the hardware using two proximity sensor named sensor 1 and 2 and trigger system. To
validate this system, size and thickness of the nut and different specimen’s material are
analyzed. Findings shows sensor 1 and 2 and trigger signal are working efficiency by
detecting missing nut. It can conclude that Poka-yoke system is very flexible, simple and
robust to detect and correct localization mistakes and it helps to reduce the number of error
occurring during the production processes.
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ABSTRAK
Poka-yoke merupakan satu kaedah dalam proses pembuatan lean yang menggunakan
sensor atau alat-alat lain untuk mengelakkan dan menghapuskan kecacatan produk dengan
mencegah, membetulkan atau menarik perhatian kesilapan manusia. Tujuan projek ini
adalah untuk mereka bentuk, membangun dan menganalisis sistem Poka-yoke untuk
pengenalan nut untuk pencegahan kecacatan. Pembangunan sistem Poka-yoke bermula
dengan pengaturcaraan membina menggunakan Arduino perisian IDE dan mikropengawal
ATmega328 digunakan sebagai antara muka di antara sistem dan perkakasan. Proses
seterusnya adalah untuk membina dan melaksanakan perkakasan menggunakan dua sensor
jarak yang dinamakan 1 dan 2 dan sistem mencetuskan. Untuk mengesahkan sistem ini,
saiz dan ketebalan nut dan bahan spesimen yang berbeza yang dianalisis. Penemuan
menunjukkan sensor 1 dan 2 dan isyarat mencetuskan bekerja kecekapan dengan mengesan
kehilangan nut. Ia boleh membuat kesimpulan bahawa sistem Poka-yoke adalah sangat
fleksibel, mudah dan mantap untuk mengesan dan membetulkan kesilapan penyetempatan
dan ia membantu untuk mengurangkan bilangan kesilapan yang berlaku semasa proses
pengeluaran.
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TABLE OF CONTENTS
Page
EXAMINER’S APPROVAL DOCUMENT iii
SUPERVISOR’S DECLARATION iv
STUDENT’S DECLARATION v
DEDICATION vi
ACKNOWLEDGEMENTS vii
ABSTRACT viii
ABSTRAK ix
TABLE OF CONTENTS x
LIST OF TABLES xiii
LIST OF FIGURES xiv
LIST OF SYMBOLS xvi
LIST OF ABBREVIATIONS xvii
CHAPTER 1 INTRODUCTION
1.1 Project Background 1
1.2 Problem Statement 3
1.3 Objectives 4
1.4 Scope of Project 4
CHAPTER 2 LITERATURE REVIEW
2.1 Introduction 5
2.2 An Overview of Poka-Yoke System 5
2.3 Applications and Implementations of Poka-Yoke System 10
2.4 Software for Implement in Poka-Yoke System 15
2.5 Nut Identification 17
2.6 Defect Prevention by Using Poka-yoke System 18
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2.7 Poka-Yoke System with Nut Identification 30
2.8 Summary 32
CHAPTER 3 METHODOLOGY
3.1 Introduction 35
3.2 Flow Chart Poka-yoke System 37
3.3 Design of Poka-yoke System 38
3.3.1 Auto- Computer-Aided Design (CAD) Software 38
3.3.2 NI Multisim Software 38
3.3.3 Transformer 39
3.3.4 Design of Driver Board (transmitter) 39
3.3.5 DC Motor 42
3.3.6 Proximity Sensor 43
3.3.7 Specimen 44
3.4 Phases 45
3.4.1 Phase I: Programming using Arduino IDE software 45
3.4.2 Phase II: ATmega328 47
3.4.3 Phase III: The Hardware 49
3.3.4.1 Start / Stop Button 51
3.3.4.2 Conveyor Start Working 51
3.3.4.3 Placed Nut on the Conveyor Belt 54
3.3.4.4 Analyzing Nut Detecting with Proximity Sensor 54
3.3.4.4.1 Sensor 1 54
3.3.4.4.2 Sensor 2 56
3.3.4.5 Trigger System (Output Signal) 57
3.5 Overall Installation for Phase 1, 11, and 111 58
CHAPTER 4 RESULTS AND DISCUSSIONS
4.1 Introduction 59
4.2 Troubleshoot 59
4.3 Analysis and verify of result 61
4.3.1 Capability sensor testing 61
4.3.2 Different thickness of nut 63
4.3.3 Different specimen’s materials 66
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CHAPTER 5 CONCLUSIONS AND RECOMMENDATIONS
5.1 Introduction 69
5.2 Conclusions 69
5.3 Problem Encountered 70
5.4 Recommendations 70
REFERENCES 72
APPENDICES
A1 Gantt Chart FYP I 75
A2 Gantt Chart FYP II 77
B1 Design of Poka-Yoke System 79
B2 The Whole Schematic Diagram of Poka-Yoke System 80
B3 Schematic Diagram of Transformer is Connected From 81
Power Supply and to Terminal Block
B4 Schematic Diagram of Dc Motor 82
B5 Overall Programming of Poka-Yoke System 83
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LIST OF TABLES
Table No. Title Page
2.1 Comparison of the Two Alternative 18
2.2 Coding Defects with Their Root Causes and Defect 25
Prevention Action
4.1 Trouble Shooting of Component 59
4.2 Result Trials of Capability Sensor 62
4.3 Result Trials of Different Size Nut 65
4.4 Result Trials of Different Specimen’s Materials 66
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LIST OF FIGURES
Figure No. Title Page
2.1 Layout of the proposed system 13
2.2 Example of Child Part 17
2.3 Streams Poka-Yoke Equipment 21
2.4 Used a Simple Device Poka Yoke for Bearing Shaft 21
2.5 Correct Direction of Bearing Shaft Flow 22
2.6 Incorrect Direction of Bearing Shaft Flow 22
2.7 Uncontrolled Concentrations Levels of CO2 and CO 23
2.8 Controller Outputs to DC-Motor of Fan1 and Fan2 23
2.9 Net Concentrations of CO2 and CO after Using the Controller 24
2.10 Comparative Graphs of Inspection for 3 Companies Over 5 27
Selected Projects
2.11 Comparative Graphs of Testing for 3 Companies Over 5 27
Selected Projects
2.12 The Patient Care Process 29
2.13 Frame Rail without Welded Nut 31
2.14 Frame Rail with Welded Nut Present 31
2.15 Cognex Checker Vision Sensor Inspects Frame Rail 32
3.1 Flow Chart for Poka-Yoke System 37
3.2 Transformer Connected to Terminal Block 39
3.3 Design of Driver Circuit 40
3.4 Terminal Block Component 41
3.5 Driver Circuit is Connecting With Other 42
Component Using Wire
3.6 DC Motor Connected with Convenyor Belt 43
3.7 Proximity Sensor with Convenyor 44
3.8 Sample of Nut 44
3.9 Flow Chart for programming Poka-Yoke system 46
3.10 Flow Chart the Interface 47
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3.11 ATmega328 into Arduino Uno board 48
3.12 Connection between Arduino port and driver board 49
3.13 Flow chart for hardware system 50
3.14 The Start / Stop button 51
3.15 Operation of conveyor 52
3.16 Mechanical conveyor 53
3.17 Signal yellow when conveyor is start working 53
3.18 Nut is Placed on the Conveyor Belt 54
3.19 SEN1 is Detecting Nut 55
3.20 Trigger System Triggers the Nut by SEN1 55
3.21 SEN2 is Detecting Nut 56
3.22 Trigger System Triggers the Nut by SEN2 57
3.23 Trigger System Component 57
3.24 Overall Installation for the Phase I, II, and III 58
4.1 Sample of Five Nut 62
4.2 3mm Thickness of Nut 63
4.3 6mm Thickness of Nut 64
4.4 9mm Thickness of Nut 64
4.5 Stainless Steel 67
4.6 Nickel Brass 67
4.7 PVC 68
4.8 Rubber 68
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LIST OF SYMBOLS
% Percentage
₂ Two
☺ Strong Positive Effect/Interaction
☼ Moderate Effect/Interaction
☻ Weak Effect/Interaction
X Company
Y Company
µF Micro Farade
++ Plus Sign
/ Solidus
L Light
C Computer
Ds Dimensions
V Voltage
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LIST OF ABBREVIATIONS
AC Alternative Current
A/D Analog to Digital
AVR Automatic Voltage Regulator
CAD Computer-Aided Design
CMM Capability Maturity Model
CO Carbon Dioxide
CO₂ Carbon Monoxide
COM Component Object Model
CPU Central Processing Unit
DC Direct Current
DMAIC Measure-Analyze-Improve-Control
DP Defect Prevention
FMEA Failure Mode Effects Analysis
GM General Motors
IDE Integrated Development Environment
ICSP In-Circuit Serial Programming
I/O Input to Output
KB Kilobyte
KPA Key Process Area
LED Mega Hertz
Mm Millimeter
MPLAB Microchip’s Programmable Interface Controller
MQA Malaysian Qualifications Agency
ms Millisecond
MultiMCU Microcontroller Co-simulation User
NI National Instrument
O₂ Oxygen
OE Original equipment
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OEM Original Equipment Manufacturer
ORs Operating Rooms
PCB Printed Circuit Board
PIC Programmable Interface Controller
PL Project Leader
PLC Programming Logic Circuit
PM Project Manager
PVC Polyvinyl chloride
PWM Pulse-width Modulation
QC Quality Control
QRQC Quality Response Quality Control
RX Receive
SEN1 Sensor 1
SEN2 Sensor 2
SOP Standard Operation Procedure
SQC Statistical Quality Control
SW1 Switch 1
SW2 Switch 2
TB Terminal Block
TX Transmit
TQM Total Quality Management
USB Universal Serial Bus
WBS Work Breakdown Structure
ZQC Zero Quality Control
ZDQC Zero Defect Quality Control
2D 2 Dimensions
3D 3 Dimensions
5D 5 Dimensions
CHAPTER 1
INTRODUCTION
1.1 PROJECT BACKGROUND
Shigeo Shingo was one of the industrial engineers at Toyota who has been credited
with creating and formalizing Zero Quality Control (ZQC) (Grout. John R et al., 2009). It is
a device used in manufacturing as part the Zero Quality Control method. The Zero Quality
Control System (ZQC) is a mistake-proofing approach that prevents defects by monitoring
processing conditions at the source and correcting errors that cause defects. Since it is
human nature to make mistakes, ZQC does not blame people for errors, but instead finds
ways to keep errors from becoming defects. In this breakthrough approach, mistake-
proofing devices called Poka-yoke are used to check and give feedback about each product
or operation in the process, not just a sample (Shingo, 1986).
A Poka-yoke is any mechanism in a lean manufacturing process that helps an
equipment operator avoid (Yokeru) mistakes (Poka). Its purpose is to eliminate product
defects by preventing, correcting, or drawing attention to human errors as they occur (Chen
J C et al., 1996). Poka-yoke (pronounced “POH-kah YOH-kay) or mistake proofing was
first identified by Shigeo Shingo in the 1960s when, as a statistical process control
engineer, he became frustrated that he could not achieve zero defects in manufacturing
processes. Shingo realized that there was a clear distinction to be made between a mistake
and a defect. He also realized that “mistakes” were not always the fault of the operator
particularly as the consequent defect becomes visible only at a later stage of the
manufacturing processes (Bekenn et al., 2009).
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In this study, based on the above mentioned definition, a Poka-yoke is defined as
a device that either prevents or defects abnormalities, which might be detrimental either
to product quality or to employees. Otherwise, it is a quality improvement methodology
to prevent mistakes from happening to minimize the negative consequences (Saurin et
al., 2012).
Nut identification is one or more nuts or fastening that used to identify the
missing part. Design for efficient joining and fastening which is threaded fasteners
(screws, bolts, nuts and washers) are time-consuming to assemble and difficult to
automate. Where they must be used, standardize to minimize variety and use fasteners
such as self threading screws and captured washers. Consider the use of integral
attachment methods (snap-fit). Evaluate other bonding techniques with adhesives.
Match fastening techniques to materials, product functional requirements, and
disassembly/servicing requirements (Crow K, 1998)
Fastening is one area where the concept of Poka-yoke can yield huge gains.
Assembly Magazine’s capital spending survey found that 91% of plants using threaded
fasteners in their products mount these fasteners manually, making them potential
breeding grounds for operator mistakes. To error-proof manual screw driving
operations, engineers can reduce the number of different screws required by assemblies
as well as set up the line so that one operator takes care of installing one type of screw
(Arebe et al., 2004).
Poka-yoke system is important to industry because Poka-yoke helps people and
processes work right the first time. Poka-yoke refers to techniques that make it
impossible to make mistakes. These techniques can drive defects out of products and
processes and substantially improve quality and reliability. It can be thought of as an
extension of failure mode effect analysis (FMEA). It can also be used to fine tune
improvements and process designs from six-sigma Define-Measure-Analyze-Improve-
Control (DMAIC) projects. The advantage of Poka-yoke device is simple Poka-yoke
ideas and methods in product and process design can eliminate both human and
mechanical errors, cheap and easy to implement within a production line, and that errors
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are detected either before they occur, or before they become costly to correct (Bekenn et
al., 2009).
Poka-yoke also have disadvantages such as not 100% effective, as it cannot
eliminate all defects. Otherwise, it is not effective as the source inspection approach.
This is however more effective than statistical sampling and does provide feedback in
reducing defects. The goal of a Poka-yoke is to eliminate defects by preventing
mistakes from occurring or at least detecting them at source rather than correct, at much
greater cost, when they become defects or errors (Bekenn et al., 2009).
1.2 PROBLEM STATEMENT
In this project, Poka-yoke system depends on factors can be used wherever
something can go wrong or an error can be made. It is a technique, a tool that can be
applied to any type of process be it in manufacturing or the service industry. The
problems that occur in the selected production line. Selected tools and techniques is
important to identity major problems. The main type of defects found was mis-location,
missing nut indication and half insert. Some possible causes for these three problems
are workers not able to follow or are not following the standard operation procedure
(SOP), inadvertent error, carelessness and no sensing device. Since human cause is the
major factor in this problem, as well as method and machine factor, attempt will be
made to employ Poka yoke or a mistake proofing technique.
However, this system can increase the productivity and eliminate or decrease
defect but it is not always 100% probability elimination of all errors, in such cases it is
the task of Poka-Yoke methods is detection as soon as possible. On the other hand,
effective Poka-yoke devices make possible by reducing the time and cost of inspection
to near zero. Many researchers using a Poka-yoke system to improve their productions
such as in an automotive industry likely General Motors (GM), electronic industry and
also in the management system.
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1.1 OBJECTIVES
The main objectives of this project are:
i. To design a Poka-yoke system using Arduino IDE software
ii. To construct prototype of Poka-yoke system
iii. To verify the result of Poka-yoke system for nut identification to defect
prevention.
1.4 SCOPE OF PROJECT
To develop the Poka-yoke system it consist of two phase. The first phase
involves programming which is also called software development. The process starts by
writing the program, assembling the program file, simulating the program and loading
the program into the microcontroller. For software programming that will use in this
project is Arduino IDE programming, an assembly language was used in constructing
the command in order to get the best result with the least expensive micros.
The construction of prototype hardware has been developed regarding to the
concept design of Poka-yoke device. The hardware consists of four parts which are the
power supply, input (sensor), processor and output (indicator and motor). A unit of
Arduino is used to process all inputs. This microcontroller is used to control the
automated mechanism based on the signal received from sensor. The proximity sensor
is used to detect the objects or goods when in production line. The mechanical conveyor
is function as to move the object on it. Outputs from the microcontroller are connected
to the motor circuit in order to control light emitting diode (LED) which use to guide
the conveyor. The trigger system is used to emit the output signal. DC motor is selected
for this system. The system only detected one nut at one time.
CHAPTER 2
LITERATURE REVIEW
2.1 INTRODUCTION
This project title is design & development of a Poka-yoke system for nut
identification to defect prevention. A mistake was something that would inevitably lead to a
defect unless one had a method to prevent or detect it within the manufacturing process.
This chapter describe about an overview of Poka-yoke system, applications and
implementations of Poka-yoke system, nut identification, defect prevention by using Poka-
yoke system and Poka-yoke with nut identification. Summary is also included in this
chapter to summarize all the literature review.
2.2 AN OVERVIEW OF POKA-YOKE SYSTEM
The literature presents a number of similar definitions of Poka-yoke, even though
they use different key terms and are often far from precise. According to Shingo (1986) a
Poka-yoke is a mechanism for detecting errors and defects, which is it inspect 100% of the
piece, working independently on the operator’s attention span. His stressed on the
identifying mistakes at a glance is essential and his mentions that, “The causes of defects
lie in worker errors, and defects are the results of neglecting those errors. It follows that
mistakes will not turn into defects if worker errors are discovered and eliminated
beforehand." He later continues that "Defects arise because errors are made; the two have a
cause-and-effect relationship. ... Yet errors will not turn into defects if feedback and action
take place at the error stage...”
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R. Anthony Inman (2007), in an article entitled “Poka-yoke” presented the meaning
of Poka-yoke is a technique for avoiding simple human error in workplace. It also known
as mistake-proofing, goof –proofing and fail-safe work methods, Poka-yoke is simply a
system designed to prevent inadvertent errors made by workers or operators performing a
process. The idea is to take over repetitive tasks that rely on memory o vigilance and guard
against any lapses in focus. He mentioned that Poka-yoke can be seen as one of the three
common components of ZDQC performed by Japanese companies (source inspection and
feedback are the other two).
Grout John R. (2007) and has presented a Poka-yoke is the use of process or design
features to prevent errors or the negative impact of errors or defects of non-conformances.
He also points out that mistake-proofing often involves the creation of process stoppages,
and provides tools and methods for designing them. In study Chen et al. (1996), he also
considers that a Poka-yoke is a mechanism for detecting, eliminating, and correcting errors
at their source, before they reach the customer. Other study simply defines a Poka-yoke by
means of examples, either by simply substituting this label with others, such as sensors and
jigs, or by translations such as mistake proofing or error proofing. Poka-yoke is most
effective in case of human errors. Human errors aren‟t prone to the application of SPC for
prevention. Human errors are prevented by raising awareness to the chance for mistakes.
There‟s a simple rule of thumb: one error is human, two errors are a warning, and three
errors require the quick application of Poka-yoke. The person making mistakes or the
design engineer must understand what sequence of events caused the repeated human error
(Gupta P, 2005).
Manivannan S. (2007), have presented the ideally, Poka-yoke techniques ensure that
the right conditions exist to make a good assembly, before a joining process is actually
executed. Thus, there should be only one way two parts can be joined before they are
snapped, welded, bonded or fastened together. Where this is impossible, Poka-yoke
techniques detect defects as soon as they are made, preventing faulty assemblies from being
passed to the next station. Many people think of Poka-yoke mechanisms as limit switches,
optical inspection systems, guide pins or automatic shutoffs that can only be implemented
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by the engineering department and this is a very narrow view. These mechanisms can be
electrical, mechanical, procedural, visual, human, or any other form that prevents the
incorrect execution of a process. Poka-yoke techniques can also be implemented in areas
other than production, such as sales, order entry, purchasing or product development, where
the cost of mistakes is much higher than on the shop floor. Truly, Poka-yoke techniques for
preventing, detecting and removing defects have widespread applications in most
organizations.
A Poka-yoke approach utilizes automatic devices or methods to detect problems
before or as they occur using a Poka-yoke device to minimize the negative consequences.
Human unintentionally make mistakes due to absentmindedness; misunderstanding because
of lack of knowledge with a process or procedures; and delay in judgments (Al-Araidah O
et al., 2010). A Poka yoke might be two approaches are utilized in manufacturing which
regulate the production process and prevent defects (Saurin et al., (2012).
i. Control approach, if when an error was detected, the process will shut down and
keeps the “suspect” part in place when an operation is incomplete. Base on Stewart
Anderson (2002), in control method Poka-yoke devices are regulatory in working
which are installed on process equipment and/or work pieces which make it
impossible to produce defects and/or to flow a nonconforming product to the next
process. As like shut down method control method gives 100% defect free products.
Otherwise, from M. Dudek Burlikowska et al. (2009) has review the control makes
certainty that if there is any defect; it‟s not coming outside the production line and
does not reach to the customer. E.g. To avoid wrong job loading in reverse direction
on machine we can provide work rest for the job which will avoid wrong job
loading.
ii. Warning approach is a signal the operator to stop the process and correct the
problem. Stewart Anderson (2002) has presented a review of the mechanism or
simple idea is generated in such a way that Poka-yoke devices indicate or shows to
a worker that a defect has been produced. When operator gets such warning then he
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must immediately interfered the process to correct the process responsible for
causing the defect. In case of irresponsible behavior of operator irrespective of
getting warning notice the next products will continue the same defect and produce
nonconforming products. In short again this method depends on human nature and
behavior. It is concluded that alert method gives 30% of the guarantee of good
products. Actually this method tells about existence of defect but does not assure
and does not produce 100% quality (S. Patil. Parikshit et al., 2013).
Based on researched by Stewart Anderson (2002), Poka-yoke devices work because
a nonconformity can only be in one of two states, which is it is about to occur or has
already happened. A simple Poka-yoke device to eliminate the problem was developed. The
devices of Poka-yoke consist of three basic methods to prevent product defects:
i. Shutdown. Poka-yoke devices monitor critical process conditions and shut down the
process immediately when the parameter moves of the desirable range, indicating
that a defective product has either been produced or is about to be produced
ii. Control. The devices are installed on process equipment and/or workplaces, making
it possible to produce defects and/or to flow a nonconforming product onto the next
process.
iii. Warning. This method works when the devices signal to a worker that a defect has
been produced. The worker must intervene to correct the processes responsible for
causing the defect, since otherwise the processes will output further nonconforming
product.
According study done by Shingo (1986) a Poka-yoke can be divided into three
categories of devices. They are:
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i. Physical contact, as work by physically touching something and depending on the
process, this signal can shut down the operation or give an operator a warning
signal.
ii. Energy sensing, as a transmission and reflecting method.
iii. Condition change sensing, is a detect changes in physical conditions.
Based on study by Harry Robinson (2004) has presented good Poka-yoke devices,
regardless of their implementation, share many common characteristics. For example, they
are typically:
i. Simple and inexpensive
ii. Useable by any operator
iii. Placed close to where the mistakes occur, providing quick feedback to the operator
so that the mistakes can be corrected
iv. Part of the process
Grout John R. (2007) and S. Patil. Parikshit (2013) have performed that Poka-yoke
can be used wherever something can go wrong or an error can be made. It is a technique, a
tool that can be applied to any type of process be it in manufacturing or the service
industry. The types of errors are:
i. Processing error. Process operation missed or not performed per the standard
operating procedure.
ii. Setup error. The workers were use the wrong tooling or setting machine adjustments
incorrectly.
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iii. Missing part. This problem happened when not all parts included in the assembly,
welding or other processes.
iv. Improper part/item. This problem happened during wrong part used in the process.
v. Operations error. It is carrying out an operation incorrectly, which is it has the
incorrect version of the specification.
vi. Measurement error. It is happened when the machine is under maintenance, test
measurement or dimensions of a part coming in from a supplier.
2.3 APPLICATIONS AND IMPLEMENTATIONS OF POKA-YOKE SYSTEM
Legendary manufacturing guru Deming WE. (2007) said, “Quality comes not from
inspection, but from improvement of the process.” Technically, “mistake-proofing” applies
to the assembly line, while “error-proofing” applies to product design. Thus, a good
example of mistake-proofing is a power tool that flashes a red light when a screw has not
been tightened to the correct torque. A good example and result of error-proofing is to
design the joint to snap together, thereby obviating the need to monitor torque altogether.
However, most people use the terms interchangeably (Manivannan S. 2007)
The example that performed by Manivannan S. (2007), a recent error-proofing at
Ford shows how these techniques are put into practice. On one of our engine assembly
lines, assemblers are required to install one of two sensors, depending on the model of
engine. A DC electric nutrunner is use to install the sensors, which are threaded on one end.
Although one of the sensors is long and the other is short, it is possible for assemblers to
install the wrong one. Before engineers can prevent errors during assembly, they first need
to know what errors to expect and how those errors occur. One solution way to do that is
through failure mode effects analysis (FMEA).
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For the first and third practices regarding using simple visual control systems to
help people determine the standard conditions and to support process flow and pull, both
assembly plants have emphasized the 5‟s and every piece of inventory is assigned a specific
place to be stored, and “shadows” are painted for tools at each work station. As for the
second practice of avoiding the use of computer screens, some of the visual control tools
for improving value-added flows at both plants are based on modern computer
technologies. As a result, along each assembly line, there are computer screens at each
station that signal workers what tasks to perform on the next vehicle. While management in
each plant maintains that workers are trained not to be distracted by computer screens, our
observation suggests that the second practice is not implemented. Overall, both assembly
plants appear to have implemented the use of visual control tools with differences
concerning the use of computer screens and emphasis on paperwork reduction
(Manivannan S. 2006).
An example by Grout John R. (2007), suppose a worker must assemble a device
that has two push-buttons. A spring must be put under each button. Sometimes a worker
will forget to put the spring under the button and a defect occurs. A simple Poka-yoke
solution that used is install the device to eliminate this problem was developed. The worker
counts out two springs from a bin and places them in a small dish. After assembly is
complete, if a spring remains in the dish, an error has occurred. The operator knows a
spring has been omitted and can correct the omission immediately. The cost of this
inspection (looking at the dish) is minimal, yet it effectively functions as a form of
inspection. The cost of rework at this point is also minimal, although the preferred outcome
is still to find the dish empty at the end of assembly and to avoid rework even when its cost
is small. This example also demonstrates that Poka-yoke performs well when corrective
action involves trying to eliminate oversights and omissions. In such cases, Poka-yoke
devices are often an effective alternative to demands for greater worker diligence and
exhortations to "be more careful."
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Otherwise, researched done by M. Dudek Burlikowska et al. (2009) the example
that their taken are Automotive Company which used Poka-Yoke method. This company
that their researched taking into account that the engine shall consist of approximately 310-
350 part, they are very useful in just such as companies concerned with putting together of
elements and manufacturing of parts. The produced elements must have a large precision
therefore should be to minimize in the processes possibility of appearance a large risk
omissions "something" or errors. As a solution to solve this problem, they use Statistical
Quality Control (SQC) technique to measure the defect. They are working to ensure the
highest quality manufactured products. Alongside such tools and philosophy as QC story,
QRQC, MQA, 5D and basic tools quality (diagrams, histograms, research systems of the
sample, graph Pareto-Lorenza, charts of quality control process) are also used Poka-Yoke
techniques.
Base on Grout John R. et al. (2009) have presented the tutorial of an example of a
Poka-yoke device at General Motors (GM) was described by GM‟s manager. They state
that "We have an operation which involves welding nuts into a sheet metal panel. These
weld nuts will be used to attach parts to the car later in the process. When the panel is
loaded by the operator, the weld nuts are fed automatically underneath the panel, the
machine cycles, and the weld nuts are welded to the panel. These nuts are fed automatically
and out of sight of the operator, so if the equipment jams or misfeeds and there is no part
loaded, the machine will still cycle. Therefore, the processes have some probability of
failure. An error of this nature is sometimes not detected until the car welded together and
are about to attach a part where there is not a nut for the bolt to fit into and sometimes
results in a major repair or rework activity."
To correct this problem, they use simply drilled a hole through the electrode that
holds the nut that is attached to the panel in the welding operation. They put a wire through
the hole in the electrode, insulating it away from the electrode so as it passes through it will
only make contact with the weld nut. Since the weld nut is metal, it conducts electricity and
with the nut present, current will flow through, allowing the machine to complete its cycle.