Weaving Fabrics are textile products that are widely used in many areas from clothing to curtains, from upholstery to towels, from carpets to cord fabric, and have an important place in both daily life and technical fields.
In the preparation and production processes of woven fabrics, defects occur in the fabric due to various reasons.
Due to the flexible and variable structure of the fiber, which is the main raw material of textile products, and the nature of the transformation processes into yarn and fabric, variations and deviations on the product may increase even more. Therefore, it is inevitable that faulty products containing various defects will occur. These defects are anomalies and irregularities that completely or partially prevent the use of the fabric, and are caused by raw material input, incorrect machine setting, misalignment or human-induced reasons, etc. can occur.
Both controlled and uncontrolled inputs of the production process can lead to undesirable results. It is known that a significant part of the nonconformities detected in the ready-to-wear and apparel industry, which has to work with a focus on quality, are caused by defects in the fabric.
Fabric defect by Turkish Standards Institute (TSE);
It is defined as defects in fabrics that can be seen and evaluated due to raw materials, threads, auxiliary materials, workmanship, machine equipment or working method and spoil the appearance of the fabric.
Again, the definition of "defect in fabric" made by TSE is defined as a defect that reduces the expected performance of the fabric or is easily seen and not accepted by a prospective buyer when it occurs in a prominent position in a product made of fabric.
Textile and apparel manufacturers have to evaluate their defective products in order to compensate for the revenue losses caused by faulty production.
These defects, which lead to the cost of poor quality, are inevitable and have a critical impact on company profitability and image.
A proper and systematic classification method provides great convenience in order to control and monitor the minimum occurrence of defects in woven and knitted fabrics and to offer correct solution suggestions.
The standard descriptive characteristics of error names provide language and concept unity in industrial use.
It is inevitable for products that cannot reach the desired quality level due to various reasons in industrial enterprises, and products containing these errors are generally defined as defective or damaged products. Although the concepts of faulty, defective and defective product are often used interchangeably; In fact, they refer to products formed with different properties.
In general, they are products that do not comply with the technical conditions and standards stipulated due to the reasons arising at various stages of production or that malfunction during use.
Definition of error in the dictionary of Turkish Language Association
Involuntary and unintentional wrong, fault, mistake is given as.
Defect, which is a more specific word to describe the defects that occur in the product; It is defined as “incompleteness, inadequacy, unfavorable situation and knowingly or unknowingly not doing a job properly”.
Defect, in a more general sense from a quality point of view; It can be defined as an abnormality or inadequacy that reduces or destroys the use and benefit to be provided. It is the predicted quality level or the state of being deficient and inadequate, which is expressed by the concept of nonconformity.
Definitions and relationships of terms related to conditions and characteristics in production according to ISO 9001:2015 Quality Standard
- Object (Object) :
- Existence is anything that can be perceived and is reasonable. For example, a product, process, service, person, system is a resource object.
- Products:
- The output that is the result of a process (a set of interrelated or interacting activities that transforms inputs into outputs).
There are four general product categories.
- 1-Services (for example, transportation)
- 2-Software (eg computer program, dictionary)
- 3-Hardware (e.g. the mechanical part of the engine)
- 4-Treated materials (eg woven fabric, lubricating oil).
Quality:
It is the degree to which the set of characteristics inherent in an object satisfies the conditions. The term “quality” can be used with adjectives such as bad, good or excellent.
Terms (Requirement):
It is the set of generally desired or legal needs and expectations. It may be related to the product, system or customer; eg. customer requirements, legal requirements, quality management system standards, etc.
Relevance:
It is the fulfillment of a condition.
Unsuitability:
A condition where a condition is not met.
Mistake:
It is the non-fulfillment of a condition relating to an intended or specified use. The distinction between the concepts of defect and nonconformity is important, especially because of the legal connotations related to product liability issues. Therefore, the term “defect” should be used with the utmost care.
Characteristic:
They are distinguishing features and may be inherent in the product or assigned (post-defined). A characteristic can be qualitative or quantitative.
Physical (eg mechanical, electrical, chemical and biological characteristics); -
Sensory (for example, pertaining to smell, touch, taste, sight and hearing);
behavioral (for example, courtesy, honesty, truthfulness);
temporal (eg punctuality, reliability, availability);
Ergonomic (eg related to physiological characteristic or human safety);
Functional (for example, the maximum speed of an airplane, the breathing performance of the fabric).
Ability: It is the ability of an output performed by an object to meet the conditions stipulated for that output.
Traceability: It is the ability to track an object on the basis of history, application and location.
Reliability: It defines the ability to perform as and when required.
Innovation: Identifies a product that includes innovation or change that adds value.
Grade (Grade): It is the act of classifying or ordering according to the fact that an object with the same functional use meets different conditions.
Re-rating: It is a grade change made to make an unsuitable product suitable for conditions different from the initial conditions.
Quality characteristic:
The inherent structural characteristic of a product, process or system related to a condition. Structural means found in something as a particularly permanent characteristic. An assigned characteristic for a product, process, or system is not a quality characteristic of that product, process, or system (for example, the price or owner of a product).
Human factor:
It describes the characteristic of a person who has an effect on an object under study. The characteristics can be physical, perceptual and social.
Competence: It is the ability to apply knowledge and skills to achieve desired results. The demonstrated competency can sometimes be described as a qualification.
Metrological characteristic: Defines characteristic elements that can affect measurement results. Measuring devices often have various metrological characteristics.
Configuration: Interrelated functional and physical characteristics of a product or service contained in product configuration information.
product configuration information, It contains requirements (requirements) and other information required for product design, implementation, validation, and operation processes.
Configuration base value: It is the approved configuration information that defines the characteristics that will become the reference value in a time period for the activities that will take place during the life cycle of a product or service.
On the basis of the relationship between these definitions and concepts;
It is possible to clearly explain the concepts of suitable, inappropriate and defective products. However, it is necessary to explain the conceptual difference between error and defect separately. The concept of “error” was defined as an undesirable situation made during production. The result of a possible fault on the product is usually a nonconformity and often a defect. For example, it is an error for the operator to set the dimensions outside the standard during production, resulting in an unsuitable, or defective, product. Although it is possible to describe this product as a faulty or dimensionally faulty product, it would not be conceptually correct. In the production process, every event that does not comply with the procedure or does not meet the conditions is an error and the expected result in the product is the occurrence of a defect or production failure. In other words, there is an associative relationship between the concepts of error and the resulting defect, and mistakes usually lead to defect.
Suitability and nonconformity are dependent on overall conditions, hence characteristics. The set of characteristics is in general relationship with quality characteristics, human factor and metrological characteristics and is in an associative relationship with the concept of configuration. Since the situations that cause nonconformity are in the characteristic set and contrary to the stipulated conditions and configuration, it is possible to define these set components as the attributes of the error concept. There is a mutual interaction, an associative relationship between them.
Garvin defined quality thinking as focused on 5 sub-criteria.
These criteria are;
1-opinion criteria:
It is the criterion by which quality is associated with a universally recognized high standard or level of excellence. It is also called superiority criterion and is a subjective criterion.
2-Product Oriented Criteria:
It is the criterion by which quality is defined as a measurable variable. For example, the acceleration of a car or the breaking strength of a yarn.
3-User-oriented criteria:
Here, the quality is defined according to the scale of suitability for the desired use on the basis of the user. For example, the ease of driving of the vehicle or the attitude of a fabric.
4-Value-oriented criteria:
It is a criterion that evaluates quality on the basis of the relationship between the price of the product and the benefit and satisfaction measure it offers.
5-. Manufacturing-oriented criterion:
It defines quality in terms of conformity of manufactured parts to design specification. Unsuitable parts are reworked or scrapped. Although various definitions have been made for the perception of quality and its dimensions, studies on the concept of error are extremely limited.
It is undeniable that it would be practical to apply a universal approach to the identification and classification of defects or causing errors. However, in the defect classification, which differs on the basis of sector and product group, the most and detailed studies were made for software errors.
In the field of software, different studies have been carried out on the differences and nature of defects. It is possible to gather the categories in these studies under three main clusters.
These sets are;
- Defect genus classification (taxonomy)
- Root cause analysis
- Defect classification An IEEE [12] standard has also been developed that addresses software defects in various dimensions.
Collection of data necessary for classification; It starts with the process activity and continues with the analysis of the stage where the error was caught and suspicious causes.
The Orthogonal Defect Classification (ODC) approach developed by IBM also;
- defect type,
- Source,
- Effect,
- trigger,
- Detected stage
- Severity
It has been handled with 6 different dimensions.
CLASSIFICATION OF WOVEN FABRIC DEFECTS
One of the few studies on the classification of woven fabric defects; which considers and analyzes fabric irregularities on the basis of an approach based on linear mass variation in yarns. Wegener's work.
In this study, which models ideal and real fabric unevenness, the factors that cause variation in fabric mass are discussed in 3 groups.
- Irregularity of the warp thread
- Irregularity of the weft yarn
- Irregularities caused by the weaving process.
When the studies on the classification of woven fabric defects are examined; it is often seen that defects are misrepresented or confused. This conceptual confusion, which occurs due to the inability to clearly define the distinguishing features of errors, is encountered both in the literature and especially in the error naming of industrial organizations.
There are inconsistencies such as giving the same name to different errors and different definitions for the same error. In fact, each error has its own attributes. Defining these attributes correctly plays an important role in preventing mistakes made in error classification. When talking about a thickening seen along the weft yarn in the fabric, the fact that the defect is in the weft direction is one attribute, and the thick place in the fabric is another attribute.
Therefore, such when evaluating an error;
Two separate attribute values related to the location or direction of the fabric and the physical appearance of the defect need to be addressed and examined. Therefore, different characteristics or criteria can be used to classify fabric defects.
Ancak If classification is made using two or more attributes together; Misclassification becomes inevitable.
Due to the fact that such an approach is not applied in general beyond the fact that the attributes cannot be determined correctly;
encountered in woven fabric error occurrences, causes and solutions Confusion and misconceptions are common in assessments made on In the existing sources on the classification of woven fabric defects, the differences in defect characteristics have not been taken into account in general. In other words, they are not classified on the basis of a single characteristic cluster criterion, but in a way to include several different characteristics.
Classifications that consider the source and direction of fabric defects are more common..
TS 471 ISO 8498 standard classified the woven fabric defects according to both direction and source, on the basis of two different characteristics:
- Yarn defects in woven fabric
- Errors in weft direction
- Errors in the warp direction
- Errors caused by or after dyeing, printing or finishing processes
- Fabric edge defects or faults associated with the fabric edge
- Common mistakes
TS 471 ISO 8498 standard When examined, defects in the class of “thread defects in woven fabric” and in the class of “defects arising due to or after dyeing, printing and finishing processes”;
It covers faults arising from yarn and finishing processes, respectively. Errors in the categories of "errors in the weft direction" and "errors in the warp direction" include the errors classified according to which direction they are located on the fabric surface.
As you can see some errors to the source some errors by to the direction classified accordingly. There was a mixed grouping involving two separate classification criteria.
Some of the errors included in the "Common errors" class:
- machine welded
- Some foreign matter
Because of this, it would be more meaningful to classify these errors according to their source. In addition, since the temple fault, which is also in the "general faults" class, occurs on the fabric edge, it would be more accurate to include it in the "fabric edge faults or faults associated with the edge".
One of the first studies on fabric defects Goldberg It is a book that contains fabric faults and ways to eliminate them.
Errors in this study:
- Raw Fabric Operating Errors
- Thread Errors
- Paint and Finishing Errors
- Defects in Clothing Fabrics
- Various Irregularities
It has been categorized as As subsets of the raw fabric business class;
- Weaving preparation
- Faulty machine operation
accidental material mix - weaving process,
- Various damages on the counter
- Do not damage woven fabric
The titles are defined.
A systematic approach has not been observed in the general error classification.
In the "Fabric Control Training Module" prepared by MEGEP, some errors that may occur in woven fabrics are classified as follows.
Errors Caused by the Weaving Machine
Finishing Errors: Dyeing errors, Printing errors and Finishing errors
Weaving Preparation Errors
· Errors in Surface Construction: Errors in the warp direction and errors in the weft direction
As can be seen, the error clusters defined according to 3 different criteria such as the source of the error, the direction of the error and the stage at which the defect occurs, are classified together.
One of the rare sources where fabric defects are made on the basis of a single criterion has divided the defects into three main classes.
Warp directional errors
Weft direction errors
· Errors with no obvious direction dependence.
There are other publications where woven fabric defects are similarly classified as warp oriented and weft oriented according to the fault direction.
Weaving fabric faults by source as well as a study that categorizes it according to the stages in which it occurs;
- spinning,
- warp preparation,
- size,
- Weaving,
- Paint,
- Printing
Completion
There is also another study that classifies it on the basis of production processes. A Standard Fabric Defect Glossary [194] has been prepared by Cotton Incorporated, which defines and displays a total of 28 different defects on its website.
The defect classes divided into six main groups in this study are:
Warp line – Vertical lines
Weft line – Horizontal lines
Discrete (isolated) defects
Pattern errors
· Finishing errors
· Printing errors
As can be seen, fabric defects in this dictionary are subject to a mixed classification that includes defect clusters defined according to direction, form and weld characteristics.
Fabric defects can also be classified under “Major” and “Minor” groups. However, this classification is a subjective criterion based on the evaluation and experience of the fabric quality control personnel. In addition, it is expected that the relevant fabric will differ according to the place of use and customer standard.
ERROR CLASSIFICATION METHOD
To identify and classify errors, it is necessary to identify systematic sub-attribute sets and values that characterize common characteristics. With the help of these mandatory or optional feature sets, it would be a more objective and scientific solution to categorize all defects within the framework of a standard and systematic approach.
Each error will have its own characteristics and will reveal their characteristic differences on the basis of their respective attribute values. With the help of similar studies in the literature, it would be appropriate to define the following fields as attribute sets of the error concept.
1. Intensity: It expresses the criticality of the failure to meet the conditions related to the product or to prevent use. For example, minor major.
2. Source (root cause): It expresses the characteristics and details of the inputs or processes and stages that caused the defect. It is one of the important features in error identification.
3. Physical characteristics: It is an attribute by which the error is decomposed on the basis of its physical characteristics.
It can be evaluated under two sub-headings.
Visual features: Visual characteristics of the defect on the surface
Location features: The location of the defect on the product or surface and its characteristics according to its location
4. The stage at which it is detected: It defines the stage at which the defect is noticed and detected on the product or system.
5. Symptoms: The possible signs (symptoms) and effects of the error related to the production or usage processes of the product may be different. Therefore, this property can also be used as a parsing attribute.
6. Fabrication features: Considering that the product can be produced or developed in different environments and machines, the characteristics of these variable inputs related to production will also be a subset that should be included in the defect definition.
7. Dimensional size: The size of the visually noticeable defects (the area covered) on the product surface or body is also important. These values are generally the characteristics of the product to be considered in the quality classification.
CLASSIFICATION CRITERIA OF WOVEN FABRIC DEFECTS
Classification by severity
In defect classification, one of the generally accepted criteria regardless of the product type is the severity of the defect. This classification criterion considers the degree to which the defect in the fabric affects the quality of the fabric, that is, the severity.
The same fault in the fabric does not always have the same effect. This criterion is taken as a basis for the pass or fail evaluation of the product, especially during the quality control process.
Errors are divided into three main classes according to their severity.
Minor Error:
There is a deviation from the stipulated conditions and standards, and this situation does not significantly affect the use or function of the object, but can reduce the saleability of the product by remaining below the defined standard. On the basis of the ISO 9000 standard, it is contrary to any article of the standard or the procedures in the audited unit and does not affect the entire system.
Major Error:
These are the defects that the object fails to fulfill its use or functions, or that are clearly and distinctly noticeable in the appearance of the product and that really adversely affect the salability of the product.
Critical Error:
It is the presence of a defect that may lead to an unsafe or dangerous situation that does not largely comply with the requirements foreseen for the users. Cases with significant deviations from product configuration data are classified as critical defect. RED can be considered as a criterion.
Even if it does not affect the functionality of the fabric, the errors that cause the customer to reject it, for example, color difference, are called critical errors.
Although errors are not always defined in terms of metrics; are evaluated on the basis of these three classes qualitatively.
A defect may be minor or major, depending on customer or product requirements. Therefore, this criterion may not be the invariant characteristic of errors in all cases, but rather a variable attribute value to be considered during quality classification.
In the quality control process; The Acceptable Quality Limit, referred to as AQL, is a commonly used method for measuring or evaluating specific production samples to find out whether the entire product order meets customer or product requirements.
Thanks to this method, which is applied with reference to the TS ISO 2859-1 standard; a statistically conscious decision can be made for the customer to accept or reject the lot. In choosing the AQL value, which of these three classes the error is in and the lot size are the determining criteria.
Classification by source
An important characteristic in parsing errors; is the classification of the error causing the nonconformity according to its source or root cause. Considering all the processes in fabric production; The stage at which the error occurs is referred to as the root cause. These stages are listed below;
- Yarn production, which is the main input of fabric,
- weaving preparation,
- Weaving,
- Paint
- finishing operations,
- Oppression,
- Finishing operations
- Other
When they are listed as, the machines used, the people performing the production and the environmental conditions in which the production is carried out are defined as sub-classifications.
The raw material in the weaving process is the fiber, the basic component that also forms the yarn used to obtain the fabric. Considering the fiber diversity, it can be classified as natural and artificial according to its source. Natural and artificial fibers may cause different errors due to their way of obtaining and their structure.
for example with woolen thread in woven fabric felting error in fabric obtained from polyester yarn. texturing error visible.
Therefore, knowing the fabric raw material and its properties is extremely important in classifying the fault according to its source.
The machines used in the production of woven fabric are according to the weft insertion system:
- with shuttle
- with shuttle
- Hooked
- water jet
- air jet
It is divided into five subclasses.
These machine types have their own characteristics. For example, while the shuttle weaving machine is the only machine type that creates a real edge, different edge knitting and apparatus are used in other machines.
Therefore, the faults occurring on the fabric edge in shuttle and other weaving machines show differences.
Weaving machines can also be classified according to the shedding system. In this case:
- Cam / Eccentric,
- dobby
- jacquard
Three subclasses should be mentioned.
Errors caused by the shedding system during the weaving of the fabric machine-related errors belongs to the group. After the fabrics are woven, they are subjected to dyeing and/or printing processes in a number of finishing machines. During the operations on these machines, the machine setting, the machine part and the errors encountered. machine-related errors is included in the group.
Unnecessary interventions to the machines during the production of woven fabrics and carelessness in the transportation of the fabric, etc. caused by circumstances human error Errors arising from the environment caused by the effects of conditions such as dirt in the environment where the production is made and humidity of the environment are also included as a subclass in the classification of the errors according to their source.
Classification of errors by direction
One of the important criteria taken into account in classifying defects is the location or direction of the defect on the fabric.
These errors:
in weft direction
in warp direction
Edge
random way
They are divided into four subclasses.
The basis of classification of defects according to their direction is based on determining the direction in which the defect appears by looking at its appearance on the fabric surface.
In weaving, the threads that make up the width of the fabric are called weft, and the threads that make up the length of the fabric are called warp.
If the error in the fabric is examined, if it is seen that it occurs along the width of the fabric, this error in the weft direction visible errors are included in the subclass.
Again, if the error in the fabric is examined, if it is seen that it occurs along the fabric, this error in warp direction visible errors are included in the subclass.
If the faults on the edge of the fabric are edge defects in the subgroup.
Some faults are seen in both the width and the length of the fabric. While these errors sometimes appear neatly in a circle, they are usually
they do not have a specific shape. Such errors are in the subclass called random directional errors.
Classification of errors according to the stage in which they are detected
It is also possible to differentiate according to the stage at which fabric defects occur or are detected. This criterion is mainly used for woven fabrics. raw fabric ve finished fabric It deals with two basic classes as (manufactured fabric).
But faults in the finished fabric:
It can also be separated on the basis of pre-treatment dye-printing and finishing processes.
Classifying errors by size
The effect of fabric defect on the usability of the product may vary according to the general characteristics of the defect as well as the size or dimensions of the area it covers on the fabric. Therefore, it is necessary to evaluate the errors according to their dimensions. In fact, this analysis is a characteristic value to be considered during quality classification rather than a defect classification.
Of all characteristic error properties, it is an attribute value whose value is variable. However, here too, a standardization was made by evaluating the size of the error between the predetermined lower and upper ranges.
There will also be an error point value based on the physical dimensions of the error indicating the severity level. It will receive an error score, which can vary depending on the control method applied. When the faults are classified according to their size, the distance covered by the fault on the fabric in the width and length direction is taken into account. Accordingly, it is possible to classify errors on the basis of error points. Errors seen on the fabric can be evaluated according to the four-point system or the ten-point system. The error dimensions and predicted scores for both methods are shown below. Fabric type and customer
According to the threshold values that can change according to the demands, the fabric balls are subjected to quality classification on the basis of the total error points they receive.
According to the four-point system, errors are examined in four subgroups. These groups are:
- Errors in fabric width or length up to 7,5 cm,
- Its length is 7,5 cm. - 15 cm. between errors,
Its length is 15 cm. - 23 cm. 23 cm in length with errors between The longer ones are classified as errors.
Errors in these ranges receive error points in the range of 1 - 4.
On the ten point system in general:
- Errors in width and length up to 2,49 cm
- Errors between 2,5 - 12,49 cm in length
- Its length is 12,50– 24,99 cm. errors between
- Its length is 25 cm. - 90 cm. errors between
It is classified into 4 different groups.
For wide-width fabrics, a different There is another scoring method. Here:
While the intervals of 0-2,49 and 2,50-12,49 remain unchanged, they are divided into four sub-classes as 12,50 - defects up to half the fabric and faults whose length is half the fabric and full width.
With the proposed classification study, a classification systematic was obtained by separating the woven fabric defects on the basis of different criteria and creating subsets. On this systematic basis, there is a system that will enable the diagnosis of all fabric defects. expert system development work is also carried out]. expert system In its structure, definitions of errors, alternative names, causes of errors and alternative solutions are also included.
takes. Titles offered to the user to choose:
- The direction of the error
- The appearance/form of the error,
- The stage of the error,
- weaving machine type,
- fabric type,
- Thread type
It consists of six categories.
As a result of the classification based on the direction of the errors mistakes:
- seen in the weft direction,
- Seen in the warp direction,
- seen on the fabric edge
- Random directional errors that are not seen in one direction
It is divided into four classes.
In fault diagnosis to be made with or without an expert system, first of all, choosing the direction of the fault will be one of the first basic steps. After the error direction is selected; The physical appearance / form of the defect on the fabric, the stage of the defect, the type of weaving machine used, the type of fabric woven and the type of yarn used are examined and matched with other characteristic features in the database.
it will be possible to find the cause.
For the characteristic features that can be made under the title of physical appearance/form of the error: gap, color difference, pattern, point, trace, band, curvature, fuzz, type and other ten different attribute values are presented.
Space,
thread loss from the fabric for any reason, perforation of the fabric by rubbing it etc. It is the attribute value that should be preferred for the openness formed on the fabric surface and the hollow structure formed in the fabric texture as a result of the conditions.
Colour difference,
It is an attribute that should be selected from the beginning to the end of the fabric or formed at certain points, when the color completely differentiates or differs in tone.
pattern set,
It is an attribute that should be preferred in cases such as choosing the wrong color yarn in the weaving of the fabric, printing the wrong pattern in the printing, and inaccuracy of the design.
Dot, reminiscent of the dot shape in shape and size seen on the fabric neps, knot, loop It is the attribute value that should be selected when point errors such as
In order to distinguish the defects related to the traces seen on the fabric, the trace option has also been added to the existing attribute values.
Tape,
It is an attribute that should be selected when an error is encountered in the form of a regular and a certain width stripe across the width or width of the fabric.
If the curvature is,
While the patterns on the yarn or fabric that make up the fabric should be straight, it is an option that should be preferred when it is shaped in a bias or arc form.
Pubescence
The option is an attribute that the user should prefer when there is an undesirable hairiness or more or less hairiness than desired.
It does not affect the appearance and functionality of the fabric, but is not desired by the customer. bad smell, weight For errors such as type attribute is defined. In the event that none of these nine feature sets are sufficient to define the error, it is thought to help the expert system to find the error correctly by defining the tenth option, the other option.
Thanks to the options under the appearance / format of the error; The root cause of the error can be accessed more quickly and easily.
In the detection of woven fabric defects; Another characteristic that can be used as a parsing filter is the attributes of the stage where the error appears.
These attribute values are;
raw fabric
Painting
Printing
Other operations
Provided as options.
If the fabric defect occurred during the weaving process or in a fabric that has finished weaving but has not undergone any further processing raw fabric option should be selected.
If the fault in the fabric is detected after dyeing paint option, if it appeared after printing baskı option will come into play as the decisive criterion.
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