Introduction
Improving product quality is one of the shortest ways for companies to bring their products closer to customers, the strategy that brings the highest economic efficiency. Besides, it helps businesses develop stably and sustainably and is one of the golden keys to helping the company recover from the Covid-19 crisis In recent years, along with the development of industrial parks, commercial centers, and high-rise buildings, industrial fans have become more popular and necessary than ever because of their use and importance Along with the requirements of increasingly modern life, most human activities and work are carried out in a closed environment, and the opportunity to be immersed in the pure atmosphere of nature is extremely low That is why the ventilation fan industry is developing more and more, helping regulate and circulate air and removing toxic substances and gases, providing a clean environment for living and production.
With its equally important role and customers' needs, the TDA Series - Direct Driven Tube Axial Fan is considered one of the best-selling items and contributes a significant part to the revenue of Kruger Vietnam However, the quality control of products from input to storage is not strict and uneven, leading to alarmingly unsatisfactory products when leaving the warehouse, generating more errors and causing problems Orders are delayed and add more costs to the factory Therefore, the quality control department plays an equally important role as one of the decisive factors for the success or failure of the company Because of these reasons, during the internship at Kruger Ventilation Industry Co., Ltd., the author chose the topic
"Analysis of quality control at Kruger Vietnam factory." With this topic, the author hopes to help the company have an overview from which to identify some outstanding problems to eliminate the existing errors at the factory, aiming to improve productivity, high product quality, and efficiency in factory production.
Objectives of the study
- Analyze and evaluate the quality control status in the production area of TDA fans and identify some common quality inspection errors.
- Propose solutions to improve the product quality of TDA fans and some remaining errors in quality control of input and finished products
Research objective and research scope of the topic
- Research object: quality control process of TDA fan series at Kruger
- Research scope: TDA fan series at KVN
Research methodology
- Secondary data: Includes relevant documents from factory departments.
- Primary data: All data collected from experts survey and the QC department of the Kruger Vietnam factory
- Observing and monitoring the production process, interviewing and consulting with employees in the workshop.
- Apply the Delphi expert interview method.
- Using the AHP approach to rank each element's relevance, thereby picking the factors with the greatest influence on the errors encountered during the KVN quality control stage.
Chapter 1: Introduction to Kruger Vietnam company
Chapter 3: Analysis of the current situation of quality control of TDA fans at Kruger Vietnam factory
Chapter 4: Proposed some solutions to improve quality control of TDA series - direct driven tube axial fan at Kruger Vietnam company
CHAPTER 1: OVERVIEW OF KRUGER VENTILATION INDUSTRIES
VIETNAM CO., LTD 1.1 Business overview
Company name: Kruger Ventilation Industries Vietnam Co., Ltd
Short name: Kruger Vietnam (KVN)
Representative: Mr Nguyen Thanh Toan
Website: https://www.krugerfan.com/
Figure 1.1: Head office of Kruger Vietnam company
Line of business: Producing and processing ventilation equipment; exercising the right to export and import exhaust fans and accessories; Repairing machinery and equipment.
Main activities KVN: importing components and equipment from Kruger
Ventilation Industries Pte Ltd, assembling them into finished products, then selling them directly to construction projects within the territory of Vietnam, without intermediaries or agents.
Address: The company's head office is at Lot A7.2-4, Road C2, Thanh Thanh
Cong Industrial Park, An Hoa Ward, Trang Bang Town, Tay Ninh Province, Vietnam.
In addition, the company also has representative offices in provinces such as Ho Chi Minh City, Hanoi, and Da Nang.
Figure 1.2: Logo of Kruger Vietnam Ventilation Industry Co., Ltd
Vision: Kruger's will be an Asia regional ventilators supplier acknowledged as an innovative leader by our customers, workers, and shareholders, adopting an unwavering focus on producing value and a commitment to Total Excellence for our customers.
Mission: Kruger's is dedicated to arranging our strengths and resources via cooperation with honesty, effort, and adaptability to achieve Total Excellence.
History of formation and development
Established in Singapore in 1985, Kruger Ventilation Group is a full subsidiary of Soler & Palau Ventilation Group, headquartered in Spain Kruger is a leading provider of energy-efficient ventilation solutions for residential and commercial buildings and industrial and infrastructure applications Currently, Kruger has established 18 business units in the Asia Pacific Region Kruger Vietnam is one of Solar & Palau Ventilation Group's subsidiaries with 100% investment capital from Spain.
Table 1.1: The milestones of the formation and development of
Kruger corporation and Kruger Vietnam
01/1985 The first Kruger was established in Singapore
05/1988 Entered into cooperation with Kruger Holding AG Switzerland.
12/1988 Established Kruger Ventilation Company in Singapore.
03/2003 Soler & Palau Ventilation Group acquires a 25% stake in Kruger Asia
08/2004 Expanding factories in many countries in the Asia Pacific region.
12/2004 Established subsidiaries and manufacturing plants in 13 locations across the Asia Pacific Region.
01/2005 Established Kruger Research Group with Asia's First AMCA Certified
01/2006 Kruger Corporation officially opened a representative office and business in the Vietnam market
3/2007 Soler & Palau Ventilation Group acquired a 25% stake in Kruger Asia
Holding, raising its stake to 50%.
11/2009 Soler & Palau Ventilation Group acquires Kruger Asia Holdings as a full subsidiary.
12/2009 Kruger Vietnam Ventilation Industry Co., Ltd was established with a factory in Trang Bang town, ay Ninh province.
08/2015 Established a new headquarters in Bangkok, with an investment capital of
1.2 Product lines of the company Kruger Vietnam
Currently, Kruger Vietnam company is trading and producing many specific fan lines as follows:
Table 1.2: Typical fan lines at KVN, illustrations, and applications
Fan series Illustrating images Application
Commercial and industrial applications require a large volume of air at moderate to high pressure.
The Fans can be used for supply or exhaust in
Fans (HVAC) industrial HVAC systems.
Enhance your home's indoor air quality and durability by swiftly
Fans excess moisture that can cause health problems,mold development, and structural damage.
Appropriate for ventilation and smoke spill applications.
Suitable for ventilation and smoke spill applications Tunnel Fans
Suit It is capable of
Fans) sawdust and short hardwood chips; it has high efficiency.
Warehouses, industrial, green, commercial, and agricultural areas are
Figure 1.3: Organization chart of the company Kruger Vietnam
Source: Compiled by the author
The company's organizational structure included:
The whole factory is divided into two different blocks: office blocks and production blocks All blocks are under the main management and administration of the plant manager
The office block includes the Human Resources Department, Production Department, Operation Department, Accounting Department, Sales Department, and Operation Department.
The production block includes 3 Assembly workshops and 1 Packing Workshop.
CHAPTER 2: LITERATURE REVIEW 2.1 Some basic concepts of quality
Quality is a familiar and commonly used concept in all areas of human activities. However, quality is also a complex category of much controversy and disagreement. There are many different concepts and definitions, depending on the object of use and the time and approach for quality.
As a customer, a product is considered quality when it meets a need (Juran, 2003). This is the definition used throughout his career, emphasizing the characteristics of the
"Output" product of a production process and a service Feigenbaum (2005) states,
"Quality is when using a product or service, meeting customer expectations." To put it simply, quality is a basic term that reflects how well a customer's needs are met with a product or service A product or service can be considered low quality if it does not satisfy the customer's needs Determining the quality of a product or service involves a lot of objective and subjective customer reasons (Hoyle, 2007).
There are many concepts and definitions of quality, but the ultimate goal is to create quality products and meet the requirements of consumers.
2.1.2 The concept of quality control
Depending on different perspectives and perspectives, there will be completely different concepts of quality assurance Here are some concepts:
According to Mitra et al (2016) quality control can generally be defined as a system for maintaining a desired quality level by providing feedback on product/service characteristics and performing corrective action when these characteristics differ from established standards.
The ISO 9001:2015 version also defines quality control as a part of quality management focusing on fulfilling quality requirements In order to control quality, it is necessary to control all factors that directly affect the quality process to prevent the production of defective products.
Quality control is a process by which a business needs to develop a solution to ensure that product quality is maintained or improved To do that requires the
10 company to create an environment where management and employees have a high sense of quality assurance In addition, quality control ensures that the manufactured product meets the specified specifications and characteristics The ultimate goal is to identify errors and take timely corrective actions to help businesses better meet the needs of customers and consumers.
1 Determine the quantity to be controlled
5 Compare and find the deviation
2.2 Some statistical process control (SPC) tools
The flow chart is one of 7 quality control tools used to identify error areas to find the cause and focus resources to improve that area The flowchart also provides an overview of the manufacturing and service delivery processes and identifies areas for improvement.
Based on the flow chart, viewers can easily and quickly grasp the entire process without reading the entire description document.
Give viewers an overall picture of the process, so when problems or errors occur based on the flowchart, viewers can easily and quickly:
- Zoning the area, area, or stage of the problem, thereby focusing resources on solving the problem
- Identify the problem area/stage for zoning and analysis
- Identify potentially affected areas/stages, then focus resources on handling and minimizing the negative effects of problems or errors.
Step 1: Define the start and end of the process
Step 2: Identify the steps in the process (activity, decision, input, output)
Step 3: Set up a flow chart
Step 4: Review the flowchart, verify, and improve the flowchart based on the review
Step 5: Record the date of making the flowchart for future reference and use 2.2.2 Cause – Effect Diagram
The cause-and-effect diagram, also known as the fishbone diagram, was introduced by Mr Kaoru Ishikawa in the 1960s According to Jayswal et al (2011), fishbone diagrams represent key issues in a process A cause-and-effect diagram is a method to determine the cause of poor-quality goods This tool helps to optimally detect the causes of failures, which are related to certain phenomena, quality characteristics, and defects, and helps us understand the overall relationship systematically.
Used to list and analyze cause-and-effect relationships, specifying causes, order of causes to be dealt with first, and order of work to be carried out to maintain process stability and improve the process.
Besides, the cause-and-effect diagram also helps to find the root cause of the problem, thereby combining it with several other tools to come up with solutions to overcome and improve the problem.
How to build a cause-and-effect diagram?
Step 1: Identify the issues that need to be analyzed to find the root cause
Step 2: Write the characteristics to be analyzed on the right and draw arrows from left to right
Step 3: Identify the main causes (level 1) Usually, people divide into four main causes (Man, Machinery, Materials, Methods), and can add the following causes: Measure, Environment Then plot the main causes on the chart.
Step 4: Identify all possible causes of the problem (sub-cause) and display them with arrows (sub-branch) connected to the main cause.
Step 5: After sketching the cause-and-effect diagram, it is necessary to discuss it with the relevant departments and departments to ensure that any factors likely to cause errors are not omitted.
Step 7: Evaluate and select the root causes and develop specific plans to fix the error.
Source: Compiled by the author
According to Magar and Shinde (2014), Italian economist Vilfredo Pareto states that about 80% of the effects are due to 20% of the causes in many events This is called the 80/20 rule or Pareto's law.
Then Joseph M.Juran put the 80/20 principle into quality Mr Joseph pointed out that 80% of quality loss comes from 20% of causes The numbers 80 and 20 are not completely understood as 80 and 20, and it's just a pair of numbers that represent what Juran means by focusing on "Vital - the vital few" (between 20%) to take measures to reduce errors and improve the most important issues.
OVERVIEW ABOUT KRUGER VENTILATION INDUSTRIES
Business overview
Company name: Kruger Ventilation Industries Vietnam Co., Ltd
Short name: Kruger Vietnam (KVN)
Representative: Mr Nguyen Thanh Toan
Website: https://www.krugerfan.com/
Figure 1.1: Head office of Kruger Vietnam company
Line of business: Producing and processing ventilation equipment; exercising the right to export and import exhaust fans and accessories; Repairing machinery and equipment.
Main activities KVN: importing components and equipment from Kruger
Ventilation Industries Pte Ltd, assembling them into finished products, then selling them directly to construction projects within the territory of Vietnam, without intermediaries or agents.
Address: The company's head office is at Lot A7.2-4, Road C2, Thanh Thanh
Cong Industrial Park, An Hoa Ward, Trang Bang Town, Tay Ninh Province, Vietnam.
In addition, the company also has representative offices in provinces such as Ho Chi Minh City, Hanoi, and Da Nang.
Figure 1.2: Logo of Kruger Vietnam Ventilation Industry Co., Ltd
Vision: Kruger's will be an Asia regional ventilators supplier acknowledged as an innovative leader by our customers, workers, and shareholders, adopting an unwavering focus on producing value and a commitment to Total Excellence for our customers.
Mission: Kruger's is dedicated to arranging our strengths and resources via cooperation with honesty, effort, and adaptability to achieve Total Excellence.
History of formation and development
Established in Singapore in 1985, Kruger Ventilation Group is a full subsidiary of Soler & Palau Ventilation Group, headquartered in Spain Kruger is a leading provider of energy-efficient ventilation solutions for residential and commercial buildings and industrial and infrastructure applications Currently, Kruger has established 18 business units in the Asia Pacific Region Kruger Vietnam is one of Solar & Palau Ventilation Group's subsidiaries with 100% investment capital from Spain.
Table 1.1: The milestones of the formation and development of
Kruger corporation and Kruger Vietnam
01/1985 The first Kruger was established in Singapore
05/1988 Entered into cooperation with Kruger Holding AG Switzerland.
12/1988 Established Kruger Ventilation Company in Singapore.
03/2003 Soler & Palau Ventilation Group acquires a 25% stake in Kruger Asia
08/2004 Expanding factories in many countries in the Asia Pacific region.
12/2004 Established subsidiaries and manufacturing plants in 13 locations across the Asia Pacific Region.
01/2005 Established Kruger Research Group with Asia's First AMCA Certified
01/2006 Kruger Corporation officially opened a representative office and business in the Vietnam market
3/2007 Soler & Palau Ventilation Group acquired a 25% stake in Kruger Asia
Holding, raising its stake to 50%.
11/2009 Soler & Palau Ventilation Group acquires Kruger Asia Holdings as a full subsidiary.
12/2009 Kruger Vietnam Ventilation Industry Co., Ltd was established with a factory in Trang Bang town, ay Ninh province.
08/2015 Established a new headquarters in Bangkok, with an investment capital of
Product lines of the company Kruger Vietnam
Currently, Kruger Vietnam company is trading and producing many specific fan lines as follows:
Table 1.2: Typical fan lines at KVN, illustrations, and applications
Fan series Illustrating images Application
Commercial and industrial applications require a large volume of air at moderate to high pressure.
The Fans can be used for supply or exhaust in
Fans (HVAC) industrial HVAC systems.
Enhance your home's indoor air quality and durability by swiftly
Fans excess moisture that can cause health problems,mold development, and structural damage.
Appropriate for ventilation and smoke spill applications.
Suitable for ventilation and smoke spill applications Tunnel Fans
Suit It is capable of
Fans) sawdust and short hardwood chips; it has high efficiency.
Warehouses, industrial, green, commercial, and agricultural areas are
Company organization chart
Figure 1.3: Organization chart of the company Kruger Vietnam
Source: Compiled by the author
The company's organizational structure included:
The whole factory is divided into two different blocks: office blocks and production blocks All blocks are under the main management and administration of the plant manager
The office block includes the Human Resources Department, Production Department, Operation Department, Accounting Department, Sales Department, and Operation Department.
The production block includes 3 Assembly workshops and 1 Packing Workshop.
LITERATURE REVIEW
Some basic concepts of quality
Quality is a familiar and commonly used concept in all areas of human activities. However, quality is also a complex category of much controversy and disagreement. There are many different concepts and definitions, depending on the object of use and the time and approach for quality.
As a customer, a product is considered quality when it meets a need (Juran, 2003). This is the definition used throughout his career, emphasizing the characteristics of the
"Output" product of a production process and a service Feigenbaum (2005) states,
"Quality is when using a product or service, meeting customer expectations." To put it simply, quality is a basic term that reflects how well a customer's needs are met with a product or service A product or service can be considered low quality if it does not satisfy the customer's needs Determining the quality of a product or service involves a lot of objective and subjective customer reasons (Hoyle, 2007).
There are many concepts and definitions of quality, but the ultimate goal is to create quality products and meet the requirements of consumers.
2.1.2 The concept of quality control
Depending on different perspectives and perspectives, there will be completely different concepts of quality assurance Here are some concepts:
According to Mitra et al (2016) quality control can generally be defined as a system for maintaining a desired quality level by providing feedback on product/service characteristics and performing corrective action when these characteristics differ from established standards.
The ISO 9001:2015 version also defines quality control as a part of quality management focusing on fulfilling quality requirements In order to control quality, it is necessary to control all factors that directly affect the quality process to prevent the production of defective products.
Quality control is a process by which a business needs to develop a solution to ensure that product quality is maintained or improved To do that requires the
Some stastistical process control (SPC) tools
1 Determine the quantity to be controlled
5 Compare and find the deviation
2.2 Some statistical process control (SPC) tools
The flow chart is one of 7 quality control tools used to identify error areas to find the cause and focus resources to improve that area The flowchart also provides an overview of the manufacturing and service delivery processes and identifies areas for improvement.
Based on the flow chart, viewers can easily and quickly grasp the entire process without reading the entire description document.
Give viewers an overall picture of the process, so when problems or errors occur based on the flowchart, viewers can easily and quickly:
- Zoning the area, area, or stage of the problem, thereby focusing resources on solving the problem
- Identify the problem area/stage for zoning and analysis
- Identify potentially affected areas/stages, then focus resources on handling and minimizing the negative effects of problems or errors.
Step 1: Define the start and end of the process
Step 2: Identify the steps in the process (activity, decision, input, output)
Step 3: Set up a flow chart
Step 4: Review the flowchart, verify, and improve the flowchart based on the review
Step 5: Record the date of making the flowchart for future reference and use 2.2.2 Cause – Effect Diagram
The cause-and-effect diagram, also known as the fishbone diagram, was introduced by Mr Kaoru Ishikawa in the 1960s According to Jayswal et al (2011), fishbone diagrams represent key issues in a process A cause-and-effect diagram is a method to determine the cause of poor-quality goods This tool helps to optimally detect the causes of failures, which are related to certain phenomena, quality characteristics, and defects, and helps us understand the overall relationship systematically.
Used to list and analyze cause-and-effect relationships, specifying causes, order of causes to be dealt with first, and order of work to be carried out to maintain process stability and improve the process.
Besides, the cause-and-effect diagram also helps to find the root cause of the problem, thereby combining it with several other tools to come up with solutions to overcome and improve the problem.
How to build a cause-and-effect diagram?
Step 1: Identify the issues that need to be analyzed to find the root cause
Step 2: Write the characteristics to be analyzed on the right and draw arrows from left to right
Step 3: Identify the main causes (level 1) Usually, people divide into four main causes (Man, Machinery, Materials, Methods), and can add the following causes: Measure, Environment Then plot the main causes on the chart.
Step 4: Identify all possible causes of the problem (sub-cause) and display them with arrows (sub-branch) connected to the main cause.
Step 5: After sketching the cause-and-effect diagram, it is necessary to discuss it with the relevant departments and departments to ensure that any factors likely to cause errors are not omitted.
Step 7: Evaluate and select the root causes and develop specific plans to fix the error.
Source: Compiled by the author
According to Magar and Shinde (2014), Italian economist Vilfredo Pareto states that about 80% of the effects are due to 20% of the causes in many events This is called the 80/20 rule or Pareto's law.
Then Joseph M.Juran put the 80/20 principle into quality Mr Joseph pointed out that 80% of quality loss comes from 20% of causes The numbers 80 and 20 are not completely understood as 80 and 20, and it's just a pair of numbers that represent what Juran means by focusing on "Vital - the vital few" (between 20%) to take measures to reduce errors and improve the most important issues.
The aim is to determine the most important factors affecting the process results (Wilkinson, 2006), reducing the time to solve, saving effort, and improving the quality of the process products and services (Nicolae, Nedelcu & Dumitrascu, 2015) In addition, the chart also shows the results of quality improvement activities after implementing improvement activities
Basic steps to set up Pareto chart
Step 1: Determine how to categorize and collect data
Step 3: Sort the data in order from largest to smallest
Step 4: Calculate frequency and cumulative frequency
Step 6: Identify the most important items for improvement (according to the 80:20 rule and the break point principle)
McQuater (1995) states a checklist is a sheet or form used to record data This is one of the easiest ways to gather and identify trends and inform decision-making.
The purpose of using a check sheet is often used to: check the data distribution of an indicator in the production process, check the types of defects, check the location of defects, and check the sources of causes of defects of the product, verify the work. According to Magar & Shinde (2014), the data collected by the check sheet should be classified into meaningful groups The data classification makes it easy for the analyst to get a preliminary understanding of the relevance and dispersion of the data for further analysis.
Steps to build check sheets:
Step 1: Determine the goal of the test sheet
Step 2: Determine the method of data collection
Step 3: Design a form to record data
Step 4: Test the form by collecting and recording data
Step 5: Review and modify the form if necessary.
Some methods applied in the process of finding the cause of the error
This is a method of gathering the opinions of a group of experts on a particular issue This traditional Delphi method was developed by Dalkey & Helmer (1963) To save time and money, Murry and Hammons (1995) developed the modified Delphi approach, which uses a structured questionnaire to assist specialists in focusing on the subject (Min, 2015) Although this is the opinion of a group of experts, it is conducted anonymously, meaning that the experts know each other but not each other's answers, and the opinions obtained are kept completely confidential This is different from other methods, such as group discussion and brainstorming, so they will not be influenced by each other and have more accuracy and objectivity It's objective was to group decision-making by gaining consensus but without face-to-face interaction (Dalkey & Helmer, 1963, p63)
The anonymous interview will help experts give more accurate and objective answers without affecting each other.
Can get opinions from a group of experts from different geographical locations. Find group consensus.
The results can be described statistically.
Reliability depends a lot on the selection of experts, whether they have the knowledge and experience to see the problem to be solved.
To reach a consensus, the method may involve multiple rounds of interviews, which is time-consuming.
Respondents' participation is no longer enthusiastic when having to go through many rounds of answering
Steps to implement the Delphi method
Step 1: Define requirements for expert groups The experts selected for the interview must be experienced experts in the area being interviewed, know and can
15 answer interview questions because their answers are very important Step 2: Clearly define the problem to be solved
Step 3: Build a questionnaire and send it to experts Depending on the complexity of the problem presented, the interview process can take 2-3 rounds.
Step 4: Analyze the answers and devise plans for future risks and opportunities for the given problem.
The Analytic Hierarchy Process method (AHP) is a multi-objective decision- making method proposed by Saaty (1980) This is a quantitative method and is commonly used when it is necessary to evaluate many options based on many different criteria to choose the best option Over the decades, the AHP hierarchical method has constantly been evolving to apply in many fields This method helps implementers choose the most suitable option based on identifying and hierarchizing the effects and impacts on a problem to be solved, helping reduce risks when making implementation decisions.
Currently, the AHP method is applied across the fields of economics, science, and technology, society, health, agriculture, forestry, etc The following are some of the current popular applications of the AHP method:
According to Min and Melachrinoudis (1999), AHP distribution will be applied in two main groups: Locating a warehouse and multiple warehouses
Besides, AHP is also applied in quality management (Nguyen Thi Anh Van et al., 2022).
ANALYSIS OF THE CURRENT SITUATION OF QUALITY
Quality control of input materials at IQC department
Incoming quality control is one of the most important stages in ensuring the quality of the output product because once the raw materials are not of good quality, the enterprise has to spend a lot of money in the later stages High costs for substandard products lead to failure to meet customer needs.
At Kruger Vietnam, the process of controlling input materials (tole, motor, blade, screw, etc.) is also focused and is done through the process below:
Figure 3.3: The process of checking the quality of input materials
Establish input standards, including technical requirements on drawings of materials and customer standards, and this setting occurs when working with the supplier, agreeing before making a decision purchase For materials related to color or difficult to determine the quality visually, a Master sample or a Limit Sample must be set.
After the inspection standard has been established, the QC staff continues to check the attached documents before checking the quality of the raw materials At this step, the QC department staff will check the appearance, measure the dimensions, and check the documents related to the quality of delivery, such as: checking the supplier's products (inspection report before stocking the finished product/ supplier's delivery, Q_test results report), documents, if required by KVN to be attached, are not available or are not correct, the shipment will be considered as not meeting the input factors and will be required to return the goods, not accepted take care of delivery (pay supplier)
Next, check the quality of raw materials before stocking after fully checking the supplier's attached documents This will include the following tasks:
QC staff based on inspection standards, Master samples, test limit samples, and input material results If passed, it will be stamped or confirmed by QC on the label of the raw material In case of doubt about the report on the composition of the material compared to the order requirement, the sample will be cut and sent to Q_test ingredient.
When raw materials are defective due to the supplier, the QC department will issue a ―Nonconforming Product Report‖ (NCR) for short, purchasing department works with the supplier to take remedial measures (return or request a refund) and request a discount on the material downgrade for components with lower requirements If the shipment contains NG products, the purchasing manager or quality manager will base it on the AQL inspection standard table and make the final decision.
At the end of the inspection, the QC department will sign the confirmation to the department in charge on the available report form, then transfer it to the superior for review and approval If the product is not qualified, follow the nonconforming product control procedure and return it to the supplier If successful, the staff member in charge of transferring the report to the storekeeper and entering the warehouse
The storekeeper based on the Purchase Order (PO) and the invoice checks the number of materials, updates the actual quantity on the Warehouse Receipt Note, then asks the delivery staff to sign and receive at the same time as the receipt supplier inventory If the quantity is not enough, ask to return the goods to the supplier.
After checking the number of materials and completing the delivery and receipt procedures, the warehouse will be imported, where the warehouse keeper will import and store the warehouse according to the management process of importing, storing, and exporting.
Next is the quality statistics of input materials; every day, the assigned QC department staff is responsible for making statistics on the quality of input materials when recording in the error statistics table of input materials a month Finally, the records will be saved every day after completing the jobs; the QC and purchasing staff will store the records in the File in the department.
3.2.1 Tole quality check at the factory
To produce complete fans, promote all uses, and meet customers' needs, the most important thing is that the quality of input materials must be guaranteed, meeting the strict factory standards For industrial fans in general and TDA fans in particular, tole is a material that accounts for the majority of the total material of the whole fan. Therefore, the factory's input quality control (IQC) department plays an undeniably important role Each imported batch of tole will include many different types, sizes, and functions, and they will be used to produce components to serve the assembly process of finished products behind, so the quality inspection quantity is necessary If the enterprise does not comply with the input quality inspection principles or ignores them, it will have to pay a huge cost due to the lack of raw materials to produce components, leading to failure to meet the delivery time requirements Losing customers' trust since then takes a lot of money and time to fix At KVN, the process of checking the input quality of tole lots will be carried out in 4 areas as follows:
After receiving the tole from the supplier, the warehouse department will receive the order and perform its duty to put it in the waiting area for inspection, where the order will be placed on wooden pallets and waiting for the order to be placed The warehouse department counts the actual quantity received against the previously placed order Next, the warehouse staff will report to the superior for approval before the IQC department checks the input criteria The purchasing department will contact the supplier to resolve this.
Next, when sufficient parts are reached, IQC will conduct a quality check of the tole through the appearance, size, and necessary specifications.
- Appearance: after receiving the tole from the warehouse, IQC will conduct a visual inspection of the color, scratch, and rust of the tole The IQC department will conduct sampling and quality checks using the Acceptance Quality Limit (AQL) method.
- Regarding the sampling procedure, the sampling plan will be followed as follows:
Table 3.1:Tole sampling plan table
Lot size Sample size Ac Re
Lot size: means the same product was received in the same period
Here IQC will conduct sampling Samples will be taken randomly and strictly follow the sampling plan table Samples taken randomly will be compared with the standard samples stored by IQC from previously obtained samples Specifically, for a tole order with a quantity of 2 to 10 samples, IQC will take out two samples to check.
If there is one defective sample, the entire tole shipment will be recorded by IQC and asked to return the goods provided The same goes for orders from 11 to 42.000 units.But from orders from 42001 to 800000 samples, randomly pick up from 45-55 samples; if 1 of the above samples is defective, the order is still accepted; from 2 or more defective samples will proceed to make a record and return it to the supplier.And so, for orders over 800001 samples, 70 samples will be randomly removed; if the number of defective samples is less than or equal to 2, the shipment will be accepted.Conversely, if the number of defects after inspection exceeds 2, the IQC department will make a record and return it to the supplier.
The samples taken will be tested for the following criteria:
Table 3.2: Input Tole Quality Control Process
Criteria/Requi Control standards Test method rement
Galvanized General No rust, no By eyes steel sheet conditions deformation
- Steel No deep scratches on
Cold Rolled roller lines, and no
Size According to the order Ruler/roll ruler
Specifications As in Mill Test, View vendor
Certificate of Origin, analytics Certificate of Quality certifications
If the criteria of appearance and size have been met, the IQC department will check technical parameters such as the Milk test, Certificate of Origin (CO), and Certificate of Quality (CQ), JIS G3302 through the certificates Certification from the supplier without direct testing at the factory; if the tole batch has all the documents and meets all the requirements for size and appearance, IQC will make a receipt of the goods and deliver them to the employee warehouse staff to conduct storage.
Warehouse and storage area tole
Quality control in production and assembly areas
Check the quality of the axial fan Tube-Casing
Figure 3.8: Tube Casing finished product
After receiving the tole from the warehouse department, the production workers will conduct production based on the provided standard samples as well as information about the length, width, and radius of the fan shell to proceed with production according to the specifications of the following process:
First, production workers will check to see if the tole has quality in terms of appearance, such as scratches, dents, and rust, to proceed or not for production.
After receiving the quality tole, the production worker will measure the size of the product as required with a special tape measure and ruler, and at the same time, apply anti-scratch glue to the tole to limit scratches when walking In the following stages, the next step is to use a chopping machine to cut off the unnecessary excess and move on to the next stage Here, QC staff will randomly pick up a sample to check the accuracy of the size because during the measurement process, if the measurement is redundant or insufficient, it will lead to the later stages of producing products that do not meet the quality requirements quantity.
Figure 3.9: Tole received from warehouse staff before putting into production
After receiving the sheet cut to the required size from the cutter worker, the production worker will punch the hole as required from the drawing board Production workers will use a brush to determine the positions that need to be punched before they are put into the stamping machine, here while the production workers are punching holes, the QC staff will be responsible for loading 100% of the samples products in terms of size, position, and number of holes as required.
If the tole has reached the standard in quantity, size, and location of the drill holes, it will proceed to the stamping stage into the fan shell After the hole-cutting stage, the fan shell bending stage is performed; here, the onion production worker receives the tole from the hole-cutting unit and then proceeds to put it into the bending frame; after bending the fan shell, it will move to the welding stage The fan is fixed, sticky, and aesthetically pleasing, according to the model given After that, the fan cover painting department will repaint the cover according to the original paint color from the work order of the planning department, and this process is done manually and based on the instructions of the control manual The quality of the paint film is provided by the quality control department After welding, the QC department will be responsible for re-checking the weld and the problems of rust, rust, and scratches on the fan shell with a bond before bringing the semi-finished products into the warehouse.
For bonded conditions, QC will evaluate through the following criteria:
For deep scratches: scratches ≤ 2mm accept defects, normal production, and vice versa; scratches> 2mm; rework or product type is suggested.
For welds: if there is an open position, it will be returned for re-welding; if the weld is not the same as the sample, make a record and propose solutions to the superior.
Next, QC staff will re-check the dimensions of the fan housing through the provided technical drawing Finally, QC staff will check the thickness of the paint film through a thickness tester, and the minimum requirement for the film thickness is 70 -
After checking the above issues, the QC department will make an inspection report and statistics of the number of errors that occur in the fan casing production department, report it to the superior, and proceed to store semi-finished products to serve the assembly of finished products later.
Figure 3.10: Pareto chart showing errors at the Tube Casing assembly area in the first three months of 2022
Based on the Pareto chart and following the 80:20 principle, we can see that the common errors in the Tube Casing production department are Scratched on the Surface (48.9%) and Joint weld (12.8%) errors accounting for 61.7%, although. However, both these errors occur at a low level because, for industrial fans like TDA, visual errors will easily occur during movement However, it does not directly affect the quality of the product, these errors only take time to rework, but QC staff also have to come up with some solutions to limit the two errors above Errors in the size and width of holes will directly affect product quality, so the QC department must also pay attention to these errors.
Figure 3.11: Technical drawing of TDA propeller
The propeller is the main component that helps the fan do its job, so here the quality check of the propeller takes up more time and labor Propeller has two main production stages, which are propeller production and propeller assembly; each stage will be performed as follows:
The production stage of propellers
After receiving the production order from the planning department, the production workers will also receive the tole from the warehouse staff, where they must check the quality of the tole for scratches and burrs before it is put into production export. Similar to the production of the fan cover: if the tole has scratches ≤ 2mm, accept the error, normal production; if the scratch is > 2mm, remove it and return it to the warehouse and receive another sheet Next, QC staff will proceed to receive technical drawings of propellers to determine the size, number of blades, and relative position of each blade.
When receiving information about dimensions from QC, production workers will cut the tole according to the assigned size and move to the forming stage by machine to produce individual propellers After the propeller has been shaped from the forming machine, QC will measure the dimensions of the wing again to compare with the
32 requirements set forth by the superior If the size of the propellers is different from the actual size, the propeller forming machine will be immediately asked to stop, and all unsatisfactory propellers will be disqualified, and QC staff will make a record, find the cause if no problem arises and the propellers have reached the quality of the size, the propeller forming department will transfer the semi-finished products to the propeller assembly for assembly complete.
When receiving the propeller from the previous production team, workers at the complete propeller assembly stage begin their work, where they will also proceed to assemble the propeller according to the requirements of their superiors Once the propeller has been completed, QC staff will assess the semi-finished product according to regulations.
For propellers, QC will conduct 100% inspection of products made according to the following requirements:
The propeller is not warped or deformed If the ball is warped or deformed, the product will be rejected
The impeller is not yellowed or oxidized If either or both are affected, the product will also be disqualified
Nuts must be fully set and tightened in all required positions If missing, QC will prompt and return to complete; if the nut size is incorrect, the product will also be returned and required to be redone Next, QC will use a wrench/pipe to check in the direction of tightening / wrench to measure the tightening force; if the tightening force is not guaranteed, the product will also be returned to ask for a rework.
Regarding the size, QC will use a rolling ruler to measure all required dimensions and must match the above dimensions If the size is skewed or incorrect, QC will make a record of the product and product type
Check the quality of the motor base, motor supt
Figure 3.12: Image of the motor base, motor supt
Quality control at the finished product warehouse area
At Kruger factory, after the products have been inspected by the quality control department at the assembly department, the warehouse department will continue to inspect the products for their appearance before packaging and transferrin them to the finished goods warehouse Prior to being received at the warehouse, the products must go through a quality control process according to established regulations, which will be carried out as follows:
Table 3.3:Quality control process in finished product warehouse area
Criteria/Require standards method Frequency action ment
-Fan Specifications - Follow SA - Do not use
- No rust, no conditions stains, no deformation.
- Smooth paint gloss / no peeling By eyes / correct color.
- Labels, Logos - No damage, By eyes peeling
- Accessory - No rust, no - By eyes deformation.
By eyes oil By eyes /
-The fan tightens on the pallet & wraps the stretch film
Finished products will be 100% inspected before being put into a warehouse or after shipment; after QC has checked the packing stage, they will continue to check the finished goods, and the inspection criteria will be focused on Focus on technical specifications based on the SA ticket and criteria on logo, accessories, and packaging.
If the goods do not meet, QC will also issue NCR to return the goods for rework After the products have met the standards, they will be imported or exported according to the proposal from the superior.
Evaluation of quality control activities at Kruger Vietnam factory
In general, the quality control at the Kruger Vietnam factory is quite tight and flexible, and there are many quality control processes and stages through each stage and department to want the products to achieve the best quality to meet customers' needs.
Regarding human resources: Workers who are directly involved in the production process and quality control employees always comply with and are aware of labor safety and hygiene regulations, possess high levels of professional expertise, exceptional problem-solving skills, and maintain timely cooperation between departments to effectively address any situation.
The quality control process begins with the inspection of incoming materials,including the various components of the fan, such as motors, bolts, nuts, sheet metal,and sub-assemblies Each component is checked to ensure that it meets the standards established by the factory Any parts that do not meet these requirements are immediately rejected and returned to the supplier or disposed of.
The process of checking the quality of finished products is strict, synchronous, and thorough: each fan before being shipped from the warehouse or before being delivered to customers through many checks; this helps in quality work is guaranteed, avoiding defective goods and unqualified goods to customers.
In addition to the advantages, the quality control process at the Kruger Vietnam factory still has some limitations, as follows:
At the Hub semi-finished processing stage, the author noticed some remaining limitations as follows:
- The quality of the Hub's semi-finished products depends on 100% of the experience and skill of the assembly staff, so the creation of defective products is common.
- The quality control of products depends on QC staff; they are responsible for quality control of the whole factory, so they cannot control all the products made but only focus on checking the final product together Therefore, it is possible to ignore the defective Hub semi-finished product.
During the whole assembly stage, the author noticed some remaining limitations as follows:
- At KVN, workers often assemble various types of fans within a period ranging from a week to a month Therefore, the lack of instruction sheets at the assembly positions for each type of fan, especially the TDA fan - the best- selling type - is one of the causes leading to confusion about the size of bolts and nuts during the assembly process.
- The boxes containing bolts and nuts have different sizes but share the same shape and color, leading to frequent confusion among workers during assembly.
When discovered by QC, the bolts and nuts with the wrong sizes have to be removed and reassembled, causing time waste If these errors are not detected,the product quality will be affected, especially when it reaches customers.
PROPOSED SOME SOLUTIONS TO IMPROVE QUALITY
Using statistical tools to assess the status of quality control at KVN
Below is a list of the number of fans produced from July to September 2022 at KVN
Table 4.1: Statistical table of the number of fans produced in KVN
(In which TDA series - directly driven tube) 410
Table 4.1 shows the error statistics table from July to September 2022, based on the situation of quality inspection and assembly of the TDA fan line at the factory
Table 4.2: Statistical table of common errors at KVN (unit: 1 piece)
Confusion about bolt and nut size when assembling 70
Boring Hub size is wrong, uneven 42
Wrong weld at Tube Casing department 8
Figure 4.1: Pareto chart of common types of errors at KVN
Based on the Pareto chart and the 80:20 principle, we can see that 80% of errors occurred in the quality control process of the KVN factory because workers mistakenly quoted the bolt-nut size when assembling (49%) and at the same time, boring Hub size is wrong, uneven (29.4%), accounting for 78.3% of the total number of major errors leading to affecting the quality of the fan Therefore, at the above stages, production workers, assembly workers, and the quality control department must pay special attention to well control the quality of the products before moving to another stage and before arriving customer's hand In this section, the author will focus on analyzing the above errors in detail and using statistical tools in quality to find the root cause of these errors.
The root cause of the error was that the employee confused the bolt nut when assembling
Observing the Pareto chart, we can see that the error of employees confusing bolts and nuts when assembling TDA fans accounts for the highest percentage, each worker has the same percentage of assembling the same fan over a long time is not happening because KVN produces many lines of fans and they all have different sizes, so it is common for workers to assemble the wrong bolt-nut size, which seriously affects product quality and at the same time causes damage to the product should be wasted due to errors to rework, thereby affecting the overall production time of the factory. Cases of mixed bolt-nut such as confused screw length and confused screw type code.
To find the root cause, the author lists some of the main causes of bolt-nut confusion by using a cause-and-effect diagram.
Figure 4.2: Cause-and-effect diagram of the causes of the error of bolt-nut confusion when assembling
The human factor: At the assembly stage, employees often put bolts and nuts of different sizes in the same container due to inattention In addition, employees are not
46 aware of the importance of quality and the consequences of installing the wrong size bolts and nuts, and employees are not properly trained in knowledge and skills. Moreover, after finishing assembling a certain fan family to move to another fan series assembly, the staff only changed the bolt-nut model to match the fan without cleaning the remaining bolt-nuts remnants of the old fan line Besides, after each day of the assembly, employees do not clean their positions carefully because there are old bolts and nuts left behind, and employees will easily confuse bolts and nuts when continuing to assemble on the next day next.
Method factor: The arrangement of boxes containing bolts and screws by employees is not reasonable; placing them in the wrong order for assembly leads to confusion and results in taking the wrong ones during the assembly process Additionally, when employees suspect that the length of the bolts is incorrect, they must use specialized measuring equipment to check it again, but they often overlook this step, and it leads to mistakes in the assembly of bolts and screws.
Document element: In the assembly area, the assembly personnel's bolt-nut cases are only a certain black color with no distinguishing stickers At the same time, assembly workers are not equipped with instruction manuals at each assembly location but only receive training when they receive the job, which is characteristic of the KVN factory in that there are many different types of fans, and these fans are assembled Not according to a certain rule but based on orders, so it is inevitable that employees do not remember the size of each mounting position In addition, the lack of tables of regulations, reminders, and dangerous warnings about the wrong size of bolts and nuts at work is also one of the causes of staff confusion about bolts and nuts when assembling.
Environmental factors: in the process of assembling or testing products, workers have to work in a noisy environment from assembly and production, so employees' lack of concentration and fatigue are also obvious, and this is one of the reasons causing employees to mistake the bolt-nut when assembling.
The root cause of the boring hole with incorrect, uneven Hub size.
At the assembly department, after receiving the Hub from the warehouse and completing the second assembly stage, the employees will proceed with the boring process for the Hub This is because when attaching the Hub to the motor drive shaft, it can be difficult to fit tightly, so the employees will bore the Hub hole according to the radius of the motor shaft Due to the characteristics of manual work, firstly, for new inexperienced employees, it will lead to low accuracy Secondly, due to the characteristics of KVN producing many different types of fans, the size of each type of Hub and the implementation process is also not the same In the end, assembly staff do not follow specific size parameters but only rely on perception Besides, after the Hub boring operation is completed, QC staff sometimes skip the inspection due to forgetting or not paying attention, leading to unqualified semi-finished products being put into the assembly, evenly which will seriously affect the quality of the product To proceed to find the root cause of the error, the author proceeds to list some of the main causes of incorrect, uneven Hub size by using a cause-and-effect diagram.
Figure 4.3: Cause-and-effect diagram of the causes of incorrect and uneven Hub size reaming errors.
Human factors: During assembly, staff often skip the dimensional check according to the manual before reaming and do not compare the width of the bore with the motor shaft during reaming Also, they don't realize the importance of quality in avoiding the wrong Hub size reaming error Finally, because the factory QC staff have to check from semi-finished production to assembly, it is a common occurrence for Hub semi- finished products to be overlooked.
Environmental factors: During the assembly process, employees have to work all the time in a noisy environment, which leads to employees not paying attention, leading to errors in reaming the Hub with the wrong size.
Mechanical factors: The drill machine frequently experiences eccentricity during the drilling process, which can result in the Hub being wrongly shaped or even broken if not discovered by the operator.
Application of the Delphi method and AHP method to find out the cause of bolt-nut confusion error when assembling
During the internship at KVN, the author had the opportunity to access most of the quality control stages, from the input to the finished product of the TDA fan line. Certain parts affect product quality The company has many lines, but in this topic, the author only focuses on the error that often occurs in the assembly department, which is the mistake of screwing up bolts and nuts when assembling Next, the author will use the Delphi method - expert interview method to determine the factors that cause the error of bolt-nut confusion when assembling, then use the AHP hierarchical ranking method to evaluate and select the three factors with the highest ranking are also the factors that have the most influence to create the above error.
4.2.2 Research process and application of the Delphi method
Here, the author will proceed to implement the Delphi method in a 3-step sequence.Because this is a problem that has happened in KVN, the author will also conduct a review of the documents before the author goes into the survey; this is called theDelphi correction method.
Step 1: Build a set of indicators
At this step, the author conducts a review of documents related to the issue mentioned earlier; here, the author gives four influencing factors and uses the Likert scale to conduct interviews with experts who have experience and knowledge of the subject Because the reliability and accuracy of the method depend largely on the expert answering the question, the author selected and invited several experts to participate in the survey, including two quality engineers, 2 QA specialists, and two assembly staff with five years of experience in the assembly department Due to using the Delphi method, experts who will participate in closed interviews will answer independently according to their knowledge and experience without being influenced by another person, ensuring accuracy and objectivity in the aspect of the method.
Question: Here are ideas on what causes bolt-nut confusion in the assembly area.
Please mark (X) the answer that you think is most appropriate.
The survey will have five different levels respectively, from 1 (Strongly disagree) to
5 (Strongly agree) After conducting a survey and experts suggested two more factors: The bolt-nut boxes do not have a sticker to distinguish the size; after changing the fan flow, the staff did not clean up the remaining screws The author collected the following answers:
Table 4.3: Questionnaire to survey experts' opinions with factors suggested by the author
1 Employees are not aware of the importance of quality X
2 Employees mix up bolts and nuts of different sizes in the X same box
3 After changing the fan flow, the staff did not clean up the X remaining screws
4 At the end of the working day, the employee does not clean X the worksite
5 Employees are not properly trained in knowledge and skills X
6 The arrangement of the boxes is not reasonable and messy, X leading to confusion during the assembly process
7 Employees do not measure again when they suspect that X the bolt nut is the wrong size
8 Bolt-nut cases do not have stickers to distinguish the size X
9 There is no instruction manual at the assembly site X
10 Lack of regulatory boards, reminders at the place of X assembly
11 The working environment is noisy, leading to unfocused X and tired employees
12 The missing warning sign of danger when wrong size bolt- X nut
Step 2: Calculate the average value and Content validity ratio (CVR) for each factor:
Formula to calculate Content Validity Ratio (CVR) = (Wong et al., 2020)
Where: Is the number of panelists indicating "essential," and N is the total number of panelists (Lawshe, 1975)
Lawshe (1975) assumes three options for each item, including necessary, important but unnecessary, and unnecessary; in this study, the author uses a five-point Likert scale, so the two scales need to match fit together At a score of 1.2, it is rated as unimportant, at level 3 as important but not necessary, and at a level of 4.5 as important.
After conducting the first round of the survey, the author obtained the following data table:
Table 4.4: Table of first-round Delphi interview results
According to (Min, 2015; Nguyen et al., 2022), the mean value of the scale is evaluated as follows:
The average value of the scale > 4, then the variable is successful
The average value of the scale of 3.50 - 3.99, then conduct a round 2 survey
The mean value of the scale < 3.50; the variable does not pass
And according to Lawshe (1975), the value of CRV will depend on the number of experts interviewed, specifically as follows:
Thus, in this round of interviews, the author conducted interviews with six experts, so if CVR < 0.99 and Mean < 3.5, the author can conclude that the variable does not meet the criteria.
Based on Table 4.4, after the completion of the first round of expert interviews, the above results were obtained The results show that experts have made separate and objective judgments from which to identify factors such as: at the end of the working day, employees do not clean up their working positions; employees are not properly trained in knowledge and skills; employees do not measure again when suspecting that the bolt-nut is wrong size; noisy working environment, leading to unfocused staff, fatigue are factors that do not seriously affect the process error, so the author removed the above four factors.
Conclusion: From Table 4.4, the author found that the Mean value of the remaining eight factors is greater than 4, so the author does not need to conduct the Delphi round
4.2.3 Rank the importance of each factor based on the application of the AHP method.
In order to assess the importance of the remaining factors after using the Delphi method to remove unnecessary elements, the author conducts the AHP method to continue to evaluate the importance and influence The influence of each factor that causes errors, employees confuse bolts - nuts in the assembly process, thereby ranking the priority from high to low for each factor to find the right solution.
Step 1: Establish a Pair-wise comparison matrix
In this step, the author compares the importance of pairs of criteria with each other based on the answers of experts.
Question: In your opinion, the factor "Bolt-nut cases do not have stickers to distinguish the size" and the factor "Employees mix up bolts and nuts of different sizes in the same box" is the more important factor?
At this step, experts make suggestions according to the level of assessment as follows:
Table 4.6: Typical pairwise comparison scale for the AHP method
If factor A is as important as factor B, then choose number 1 If factor A is more important than factor B, choose a number from 2 to 9 points (choose in the direction of A) Otherwise, choose B Score 9 is the most important level.
Table 4.7: Priority assessment table for criteria pairs
Bolt-nut Employees cases do mix up bolts not have and nuts of stickers to different distinguish sizes in the
Bolt-nut After cases do changing not have the fan flow, stickers to the staff did distinguish not clean up
The arrangement of the boxes
Bolt-nut is not cases do reasonable not have and messy, stickers to leading to distinguish confusion the size during the assembly process 3
Bolt-nut Employees cases do are not not have aware of the stickers to importance distinguish of quality
Bolt-nut There is no cases do instruction not have manual at stickers to the distinguish assembly
Bolt-nut Lack of cases do regulatory not have boards, stickers to reminders at distinguish the place of
Bolt-nut cases do not have stickers to distinguish the size
The missing warning sign of danger when wrong size bolt-nut
After conducting a survey from the expert, the author obtained the Pair-wise comparison matrix table as follows:
Table 4.8: Pair-wise comparison matrix
Looking at table 4.8, we can see the yellow value is 1, equivalent to comparing with itself, the value "4'" in row 2 column 3 means the criterion "The bolt-nut boxes there is no sticker to distinguish the size four times compared to the criterion "Employees mix up bolts and nuts of different sizes in the same box After summarizing the values, the author also calculated the sum for each column
Step 2: Normalized Pair-wise comparison matrix
The author calculates the normalized matrix table by taking the value of each cell in the column divided by the sum of the column by each factor After the normalized values are obtained, the author proceeds to calculate the weights of the indicators, which will be calculated by the average of the values by row.
Table 4.9: Normalised Pair-wise comparison matrix
Step 3: Calculate the Consistency Rate
After calculating the weight of each indicator, the author calculates the Consistency rate (CT) using the following formula:
CR is the Consistency ratio According to Saaty (2008), if the consistency ratio is less than or equal to 10%, it is acceptable; if it is less than 10%, the table of values is inconsistent and needs to be evaluated and recalculated.
CI is a consistency index and will be calculated by the formula:
CI = where It is the maximum eigenvalue of the pairwise
57 comparison matrix, and n is the number of selected factors The value of is calculated as the average of the Consistency vector
RI is the Random index, and according to Saaty (1987), this index is determined according to the following table:
Table 4.10: RI values for the different values of n n 1 2 3 4 5 6 7 8 9 10
That is, the Random index will depend on the number of factors that the author conducts the survey In this study, the author uses eight factors to survey, so the Random index will be 1.4.
To calculate the Consistency vector, the author proceeds to divide the weighted sum value by the criteria weights Which criteria weight will be calculated as the average of the weights of the criteria multiplied by the value of each row in the original matrix?And the weighted sum value will be the average of the criteria weights multiplied by the value of each row in the original matrix.
Table 4.11: Summary of the weights of the criteria, the weight of each criterion, and consistent vector
From the table of values 4.11, the author can calculate the following:
CR = = = 0.087 (1.4 look up from table 4.10) < 0.1
The above results are suitable, accept the results, and the author conducts the ranking of the criteria for the factors.
Table 4.12: Ranking of weights for each indicator in terms of importance
1 There is no instruction manual at the assembly site 0.30
2 Bolt-nut cases do not have stickers to distinguish the size 0.15
3 Employees are not aware of the importance of quality 0.13
4 Lack of regulatory boards, reminders at the place of assembly 0.12
The arrangement of the boxes is not reasonable and messy, leading to
5 confusion during the assembly process 0.11
6 After changing the fan flow, the staff did not clean up the remaining screws 0.08
7 Employees mix up bolts and nuts of different sizes in the same box 0.06
8 A missing warning sign of danger when wrong size bolt-nut 0.05
Proposed solutions
4.3.1 Build documentation, visualize bolt-and-nut boxes
Understanding the assembly process steps and screw sizes at various locations on the same fan is critical since it directly influences product quality and saves the company time and money in disassembling and reassembling if the wrong screw sizes are identified As a result, the author suggests that in each assembly location, employees be given assembly instructions that include the type of fan, assembly sequence, inspection method, and illustrated visuals so that employees can easily recognize and comply with the procedure The author advises that employees be given the assembly instructions listed below.
Illustrating graphics, assembly sequence, and the number and code of bolts and nuts will assist assemblers in seeing and operating simply, allowing them to rapidly identify typical assembly problems Assembly not only helps them run more efficiently and precisely, but it also helps firms save time and money on reworking defective product items From there, assemblers can contribute new improvements to the assembly process that they feel is done faster, as well as eliminate unnecessary operations In addition, the quality department should conduct a survey 1-2 times a year on the suitability of the process as well as collect small improvement comments from the assembly staff to make appropriate adjustments because they are directly implementing the process and directly creating quality products for customers.
Table 4.13: Assembly manual recommended by the author
Source: Recommended by the author
In additionto building and sending documentation down to the assembly department, the company needed to visualize the bolt-nut containers by pasting the bolt-nut codes with different images and colors, plastic pressing and gluing between one side of the box/container of different sizes of bolts and nuts, to provide
61 helping them to identify the type and stage codes of bolt-nut easily and quickly, avoiding the case of confusing bolt-nut types with each other At the same time, when assembling each stage, if the bolts and nuts are left over, it will help employees distinguish the locations of the boxes to put them in to avoid confusion and mess in the same box, causing difficulties in the next steps next assembly.
Figure 4.4: Bolt-nut identification sticker at the assembly suggested by the author
Source: Recommended by the author
These stickers will be affixed directly to the bolt-nut housing, including information such as:
- TDA - 01: In which TDA is the fan line symbol that will help staff distinguish the bolt-nut box for the fan line to be installed, and 01 is the assembly stage of the fan.
- Code: in addition to distinguishing fan lines, it will help employees distinguish different fan codes, thereby helping them identify faster.
- 1-4: these are the numbers representing the steps and types of screws that employees assemble in the same stage For example, TDA-01, code: TDA560-
V, 1 means TDA fan series assembly stage 1 with code TDA560-V and number
1 represents the type of bolt-nut to be installed for the first assembly stage of the device state 1.
By applying the method of visualizing the process and labeling the boxes containing bolts and nuts in the assembly department, the training time for new employees will be shortened and the error rate will be significantly reduced This not only helps workers see more clearly when assembling to avoid confusion with bolts but also helps them see the boxes more easily, thereby facilitating faster and more accurate recognition and operation Additionally, this practice helps the business reduce assembly time and costs.
4.3.2 Set up and apply the check sheet in Hub semi-finished product quality inspection stage
To better control the quality status of the Hub when processing semi-finished products at the assembly stage and to limit the situation that the Hub does not pass through other stages such as packaging or when it arrives at the customer's hands seriously affect the labor, cost, and reputation of the company, the author proposes to establish and apply a check sheet at the assembly department Specifically, the stage of semi-finished Hub products because the number of QC staff at the company is limited, the author only proposes to make a check sheet at the location where the percentage of errors is not of high quality.
The Hub inspection needs to be done before the staff carries out the 3rd stage of the assembly, which is to attach the Hub to the motor shaft; QC staff will conduct the inspection when the semi-finished products are finished after being drilled by the staff.Check will be done via check sheet Every day, QC staff will inspect according to the check sheet table After being assessed as passing from QC, the new staff will assemble this to help prevent the semi-finished Hub products from being passed to the next stage of quality
Table 4.14: Hub semi-finished test sheet suggested by the author
Note: check all, and put an X in the selection box.
The hub diameter does not fit the motor shaft
Hub is deformed Total Conclude
Source: Recommended by the author
The Hub quality check process is done as follows:
- The assembly staff will proceed to receive the Hub from the warehouse and check it carefully If the Hub has a problem, they must report it immediately and receive a new semi-finished product.
- After receiving the semi-finished products, employees will proceed to ream the Hub according to the company's regulations and instructions for each type of fan.
- Next, before going through the next stage, QC staff will conduct a Hub inspection through a Check sheet; if successful, QC will record, and staff will proceed to the next stage If not, the staff will proceed to remove the Hub and re-remove the new semi-finished product until it passes This will limit the situation in that employees ignore the quality requirements and proceed to the next stages.
Performing a Hub semi-finished product inspection not only helps to limit the risk of making an error in making the wrong and uneven Hub size but also helps the company to promptly detect low-skilled employees in the manufacturing process TheHub then focuses on training for the right people, besides it also contributes to ensuring product quality and reducing the factory's error rate.
Quality system management is always a difficult problem for businesses, especially for manufacturing companies, because quality is a long journey, a persistent goal and should be given top priority if Businesses want to grow sustainably To create a truly quality product for customers, Kruger Vietnam has constantly improved and improved the quality assurance work, step by step, bringing itself deeper and broader integration to difficult customers.
During the internship at the company and implementing the project " Analysis of quality control at Kruger Vietnam factory" under the enthusiastic guidance of the quality control staff, the author had the opportunity to experience the quality evaluation process of the TDA fan series from the assessment of input materials to the finished product, accumulating useful knowledge and experiences, and through which the author has looked at recognize and detect some outstanding problems in product quality control from input to finished product Thanks to the collected information,research materials from the quality department, and especially the dedicated help and guidance from lecturers, the author has applied methods such as interviewing Delphi experts and the Analytic Hierarchy Process (AHP), then identifies the causes of errors and proposes some solutions to improve quality assurance at the factory However, the solutions proposed by the author still have some limitations, it takes a lot of time to test and deploy simultaneously, but this is one of the first experiences and lessons to help the author have a stepping stone to further my passion for quality.
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