Significance of “Quality Control” in Leather Goods and Garment Production

Abstract

The leather industry is one of the priority sectors that contribute to export income and economic development in the majority of African countries, in terms of creating job opportunities. Leather products need high care during manufacturing because their quality should never be compromised. Quality is a universal term used to evaluate the performance of a product or a service and the acceptance by the customer(s) in terms of customer satisfaction. As such, understanding quality concepts such as quality control (QC), quality standards, procedures, and documents related to leather goods and garment production in accordance with manufacturing company’s policy is deemed useful within the context of this paper. Supervisors, quality controllers, and operators in leather products manufacturing firms need to know required quality parameters and associated control mechanisms so that defect-free products will reach the end users. In order to achieve this, quality-influencing parameters such as performance, reliability, durability, serviceability, esthetics, features, and conformance are measured so as to verify set quality levels. Furthermore, factors that affect the quality of leather goods and garments as well as methods of identifying and isolating common defects and faulty pieces especially in the finishing activities of leather production are included herein. Hence, this paper covers quality control aspects on leather goods observed within the garment manufacturing subsector.

1. Introduction

The leather sector is regarded in most African countries as a major economy driver that highly contributes to a country’s economic growth by means of employment opportunities and foreign cash inflow. The leather sector includes tannery, footwear, leather gloves, and leather goods and garment subsectors. Leather by itself requires high care during the different phases of production, storage, and transportation. Hence, the issue of quality in leather manufacturing process is of paramount importance as most defects in leather and leather products are irreversible. Rework or correction of incurred damages during production of leather, leather goods, and garment leads to higher labor costs and sometimes to rejection of the products. Therefore, the implementation of quality control (QC) concepts in every production step is associated with a valuable impact on the finished products so that defect-free products reach end users.

Most of the Ethiopian companies specializing in the leather sector prefer visual inspections and simpler physical testing methods to control product quality. This preference may work for the local market as the latter may not draw too much focus on quality aspects due to it being less aware for various quality dimensions. However, for penetrating and competing on an international level, special privileges such as African Growth Opportunity Act (AGOA) from importing countries or producing goods with the required quality and at a competitive price are required. Nonetheless, consistent with descriptive statistics results, econometric findings also reveal that exporting firms were found rather less efficient compared to those which are either powerless or have totally given up looking for the international market with respect to income and market sustainability. Once basic international standards are met and market access is established through various mechanisms including participation in trade fairs, the use of the internet, and buyer contacts, exporting companies have continued to benefit from the market due to the natural superiority of Ethiopian leather in terms of fineness, thickness, flexibility, strength, and compactness of texture, according to UNCTAD (2000) [1].

But this is not true for export markets. All leather and leather products-related quality standards need to be implemented which in turn includes, but may not be limited to, physical and/or chemical testing and inspections. In a perfectly competitive market setup consisting of a high number of buyers and sellers (also referred to as a thick market), price signals would reward high quality, and hence, producers and traders of substandard quality would either be driven out of the market or would be relegated to a distinct low-quality-oriented market [2].

This chapter provides a background on quality control aspects for the production of leather products that directly reach end users. It covers quality control aspects applicable to leather products and goods and the garment manufacturing subsector.

1.1 Aims and objectives

The objective of this chapter is to provide a background on quality control aspects required in the production of leather products. In doing so, this research work aims to address the significance of quality control and quality aspects in the leather products manufacturing subsector.

2. Literature review

Quality is an absolute term. Concepts of quality and quality control with regard to the manufacture of leather goods and garments need to be viewed in accordance with the policies of the relevant specialty industries. The outcome thereof in conjunction with the application of quality control concepts listed herein will serve as the basis for supervisors, team leaders, and even operators in those companies with advanced know-how to the parameters, check points, and control mechanisms so that defect-free products will reach end users.

Most Ethiopian leather and leather products manufacturing firms had implemented various quality-related improvement tools and systems including, ISO 9001:2018, Environmental Management Systems (EMS ISO 14001:2018, Occupational Health and Safety Management Systems ISO 45001:2018), and a plethora of other quality management systems (QMSs) in order to enhance their local and global competitions. For instance, (ELICO) Ethiopian Leather Industries Company PLC, Pittards Glove Manufacturing Factory PLC, Modern Zege leather products and footwear Industry PLC had implemented these systems [3].

Therefore, they will be able to acquire and maintain quality concepts, agreed quality standards and procedures, and introduce quality control/quality assurance (QA) to organizational staff/personnel. Furthermore, they will apply these parameters in leather goods and garment production, identify accompanied issues, and provide related documents to employees in accordance with the organization policy.

To implement quality standards, the basic conditions of the customer are (a) the purpose and (b) the selling price of the product or service.

These basic conditions can be resolved in to the following 10 detailed conditions:

• specifications of dimensions,

• operating characteristics,

• life and reliability objectives,

• safety requirements,

• relevant standard,

• engineering,

• manufacturing and quality costs,

• production conditions,

• field installation,

• maintenance and service objectives,

• energy utilization and material conservation factors,

• environmental and other side effects, and

• cost of operation or use

2.1 Concept of quality

Quality is the totality of features and characteristics of a product or service that affect its ability to satisfy the specified or implied needs of a customer. Quality consistency requires from users to concentrate on the process rather than on the product alone. Quality gurus define quality as “conformance to requirement” and “fitness for use” [4]. Good quality will automatically result in productivity improvement. It is the author’s view that the best policy should be to do the things right first time.

Quality helps determine a firm’s success in a number of ways:

• customer loyalty: satisfied customers return, make repeat purchases, and recommend the product or service to others,

• strong brand reputation for quality: retailers want to stock the product; improved quality leads to fewer returns and replacements which in turn lead to reduced costs attracting thus and retaining good staff.

The term “Quality” can be measured aspects such as failure or reject rates, level of product returns, customer complaints, customer satisfaction, customer loyalty, evident from repeat purchases, or renewal rates and employee health and well-being.

2.2 Quality parameters

Quality is measured in a relative manner. It depends on how the user perceives or the way he/she get satisfied with that product/service. Once a product/service is accepted to customers, it can pull more new customers and may be produced/delivered in greater numbers, affecting in turn costs that are reduced and sales which will be increased. But, as quality has no universal meaning, the way users perceive it varies. Some users may like the performance or the reliability, while others may be happy with esthetic features and so on. What is reliable for a user may not be true for another. Hence, quality is an important factor which customers look for in a product or service in order to be rewarded with total satisfaction. Some of the important quality factors/parameters that customer considers in a product or services as stated by some quality gurus are listed as follows.

2.2.1 Dimensions (parameters) of quality

Performance: it evaluates if the product does the intended (planed or proposed) job or if the service delivered meets intended objective. Potential costumers usually evaluate a product to determine if it will perform certain specific functions and how well it will do them. For example, the production of a document holder or a leather bag with multifunction pockets would fall within this category.

Reliability: it indicates a product’s failure rate. Different products may need repair over their service life. The leather machineries should be also reliable so as to increase productivity, i.e. when leather garments are produced, greater attention ought to be placed during, e.g. the stitching procedure. As the needle is typically of a cutter edge type, sometimes it stitches the component by cutting the part. So, if proper stitching is not done, the product is either repaired or rejected.

Durability: it shows the duration that the product is expected to last for. This is the effective service life of the product that customer wants over a long period of time, e.g. a customer that orders a leather jacket may expect this to last for at least 5 years.

Serviceability: this parameter stands for how easy the product may be repaired. There are many industries where the customer’s view of quality is directly influenced by how quickly and economically a repair or routine maintenance activity can be accomplished’ in this case-study, dyeing or changing color of the leather jacket after a number of uses can be an example for this.

Esthetics: this dimension shows what the product looks like externally. This is the visual appeal of the product, often taking into account factors such as style, color, shape, packaging alternatives, and other sensory features.

Features: it means what features the product possesses. Usually, customers associate high quality with products that have added features (such as special color, design, handles, and decorations), which go beyond the basic performance of the competition.

Conformance: it is used to evaluate if the product or service conforms to the specification. This means, if it is developed based on a performance specification; will it actually perform as specified? If it is developed based on a design specification, does it possess all of the features defined?

Perceived quality: The product or service may possess adequate or even superior dimensions of quality but still fall victim to negative customer or public perceptions. As an example, a high-quality product may get the reputation for being low quality based on poor service by installation or field technicians. If the product is not installed or maintained properly, and fails as a result, the failure is often associated with the product’s quality rather than the quality of the service it receives.

2.3 Quality control and quality assurance

Quality control (QC) is a procedure or a set of procedures intended to ensure that a manufactured product or performed service adheres to a defined set of quality criteria or meets the requirements of the client or customer. While quality assurance (QA) is defined as a procedure or set of procedures projected to ensure that a product or service under development (before the work is complete, as opposed to afterward) meets specified requirements. QA is sometimes expressed together with QC as a single expression. There is plenty of quality control types. The following are used in the leather-related production controls [5].

• Quality control of incoming material:

  • Ensuring the right materials are available in the right quantity at the right time.

  • Based on quality requirements, the purchase information such as specification, packing instruction, and transportation instruction should be clearly identified.

  • For example, in the garment industry for finished leather, the parameters such as color fastness, light fastness, tensile strength and softness need to be checked.

  • Physical characteristics such as lining, tensile strength and color fastness need to be checked. After finalizing the parameters to be assessed for each incoming material, the standards need to be met for each parameter of each incoming material.

• Process control:

Process control (PC) can be defined as any activity that adds value to the product to be supplied or the service to be rendered. The term “process” in the leather garments manufacturing industry may include – but not be limited to – unit processes such as cutting, assembling and stitching, and finishing. According to the process control steps, the parameters for each process need to be identified first. For example, in assembling and stitching, the needle to be used, i.e. the needle number and needle point have an influence on the final product. Further, the thread used in bobbin (lower thread) and the sewing machine (top thread) also affects the quality of the final product.

Process control is carried out by the following steps:

• Identification of process control parameters,

• Establishing the standards for each parameter of each process (internal process control standard/working standard for process control),

• Fixing the limits for each parameter.

Figure 1 shows the intended process control.

• Product control:

Figure 1.

Process control.

Product refers to the physical output produced by supplying in the inputs or raw materials and carrying out any production process. The final product is what is dispatched to the customer or the end users. Apart from this, there are components sometimes referred to as intermittent products. For a leather garment manufacturer, these are prepared sleeves, pockets, collars, etc. Therefore, the output after each operation or process is an intermediate product. Product control generally refers to the control of the final product. Control of intermediate products is equally essential. This is due to the fact that in each stage the product quality is ensured so as to produce the final product of desired quality [6].

2.4 Quality inspection and testing

Quality inspection: Industrial activities which ensure that manufactured products, individual components, and multicomponent systems are adequate for their intended purpose. Whereas inspection is the activity of examining the product or its components to determine if they meet the design standards, testing is a procedure in which the item is observed during operation in order to determine whether it functions properly for a reasonable period of time under given stress conditions. Inspection and testing are performed before, during, and after manufacturing to ensure that the quality level of the product is within acceptable design standards.

There are also various types of inspections. The following categories are used in leather goods and garment production:

• Incoming materials inspections: checking the quantity (finished leather, accessories, etc.), quality, rejection allowances, verification as per purchase order, lead time, etc.

• First-article inspections: QC inspects first-article samples prior to volume production. This verifies that product specifications are being met and avoids unnecessary re-engineering work later.

• In-process inspections: these on-site inspections evaluate samples of the products selected during the manufacturing process. This confirms the quality of the product and allows any necessary changes to be addressed early on reducing, hence, rework time and costs.

• Pre-shipment inspections: during a pre-shipment inspection, engineers verify that finished goods conform to set specifications.

• Sample inspections: samples are taken from inspection lots for end user evaluation, laboratory testing, or customer approval randomly, and processing QC can help for inspection. After this type of inspection, one can offer rapid service at a very affordable rate.

International standards are preferred to be used for testing leather products, especially in the garment industry. Table 1 shows this standard.

No.	Items	Standard
1	Elastic tapes	IS 9686
2	Metal buckles	IS 96986:1980
3	Threads	IS 1376/1803
4	Leather garment sizing system	IS 10397
5	Metallic slide fastener	IS 3148:1983
6	Garment quality guide	IS 12675
7	Leather for garments	IS 12718
8	Fur leather	IS 3840/2961
9	Fusible lining	IS 12806
10	Zip fasteners	IS 8894/3184/4829

Table 1.

Standards related to leather garments industry and related items.

Source: Leather Industry Development Institute, Advanced Garment Production, Level IV Training Materials, June 11, 2016.

3. Results and analysis

3.1 Leather goods common quality parameters

In addition to the eight quality parameters of any product like durability, feature, performance, conformity, esthetics, serviceability, perceived quality, and reliability, there are also other leather goods-specific quality parameters.

3.2 Most commonly used types of testing

Leather testing: it includes wet rub fastness, dry rub fastness, tool test, stress strain test, and plaster test fastness.

Leather goods and garments testing: it encompasses handbags and small luggage, wherein the strength – say – of strap fastenings is an important consideration in the quality assessment of handbags and luggage. A large number of companies in Ethiopia are able to carry out all strength tests utilizing state-of-the-art equipment to assess the risk of strap failures, whether at fastenings (e.g. buckles) or where the strap is attached to the body of the item itself. The other one is the leather belt testing, from an assessment of the components of a belt for labeling purposes. Also, specialty companies can perform further tests in order to satisfy all clients’ requirements such as the color fastness (wet and dry rub fastness test) to tarnishing of buckles and metal components, to ensure the products are fit for the purpose they are intended for.

A few examples of tests used in leather products manufacturing firms are as follows:

Smell test: the smell test is an important part of every inspection. To avoid illegal toxins, the most reliable way to check it is to perform chemical tests as per ASTM D1296 in an accredited Leather Industry Development Institute (LIDI) laboratory.

Function test: the objective is to check if the product works as designed or anticipated. In the case of the leather bag, an inspector will wear it and test the zippers’ direction and strength.

Color fastness check on leather: excessive dye may be rubbed off during a color fastness check. On leather, this is a frequent problem. The test may be repeated 10 times with a dry cloth and 10 times with a wet cloth.

Abuse and fatigue tests: pulling on straps and zippers with stronger-than-usual force helps to understand the manufacturing quality of leather bags.

Seam strength test for leather bags: this test is similar to the abuse test but focuses on the seams. It uses a tension gauge to check seam strength.

Load test: the inspector loads the leather bag with weights (depending on the model between 2 and 20 kg for backpacks (bag type) most of the time. Then the bag is lifted at least 20 times and is hanged on a hook for 4 h. This is an internal company policy similar to that of color fastness check.

Zipper twisting test: this type of test is used to check both the strength of the zipper and the seams holding it in the open middle and closed position. The QC pulls the zipper sideways for 10 s in each direction. Low-quality zippers tend to open and bend beyond repair. Extensive laboratory equipment test products (e.g. opening and closing zippers 5000 times) could be used also. However, most of small and medium leather products manufacturing companies use the manual test.

Carton humidity check: This test is performed in order to assess the behavior of the product in rainy conditions, while avoiding the buildup of mold or fungus, aiming at maintaining a humidity level below 12%. In particular, during the rainy season, the inspector should check the humidity of the export cartons with a humidity tester. As such, it ought to be ensured that sufficient desiccant (calcium oxide absorb water) is placed in the right spots.

3.3 Factors that influence the quality of leather goods and garments

Factors that influence quality aspects make bags and garments good and/or cheap. The following aspects are commonly experienced in leather products manufacture:

3.3.1 Designs and materials

The design room is where quality starts in leather goods manufacturing companies. Bag design is a system, which is not only the combination of the technique, knowledge, and the art, but also the connection of design and craft from the choice of the theme to grasp the inspiration and the accomplishment of the finished product. Through the design effect of a product, a bag or a garment should become a bridge between designers, technicians, and consumers. In that sense, it would be common language among them. The designers should identify the materials like type of leathers, accessories, colors, and hardware that will be used in the production process. A well-designed bag or a garment should include all information about its design. As an example, a good leather goods design should have at least the following information:

• leather type (color, thickness, and feeling),

• origin (cow, sheep, goat, buffalo, etc.)

• reinforcement (EVA sheet, water proof, fusing, foam, etc.),

• lining (velvet, cotton fabric, nylon, and polyester),

• accessories (eyelet and rivet),

• zipper, in terms of size (3, 5, and 8 mm), finishing (silver, gold, and bronze), and type (metallic, plastic chain, and plastic molded),

• stitching (seam type and seam length per centimeter),

• thread size (for needle thread and bobbin thread), type (cotton, nylon, polyester, silk, and polyester spun cotton), each dimension, (volume, height, and base, handling length, and width),

• edge finishing (raw edge, folded, and edge color) and hard ware’s (buckle, color, and adjustable size) [7].

3.3.2 Material selection

Material selection refers to the materials selected for the manufacture of – say – a bag including the hardware and the accessories, as well as the processes involved.

3.3.3 Pattern making and cutting

The pattern making, which is also referred to as a sample making process is an important aspect and is regarded as a bridge of transforming the graphic designs into the products. The maximum permissible error (acceptable level) of pattern is 1/32 inches (1 inch error of 32 inches length), as by reference to any bag, or in accordance with international standards, such as SATRASumm, which is an industry standard package concerning the efficient cutting of leather and synthetic materials. In pattern making, usually major parts (shape and size of the bag) are made first, and then relatively smaller parts are followed and so on.

3.3.3.1 Fixing product size standards

Unlike leather garment and foot wear products, leather bags have no fixed specifications such as height, depth, and width and may therefore be easy to categorize as small bags, medium bags, and large bags. One could remember Galileo Galilei’s quote: “Measure what can be measured, and make measurable what cannot be measured.” From a quality management point of view, this means that “we cannot manage what we cannot measure.” In short, the clearer the specification, the better the possibility of creating and delivering quality products.

3.3.3.2 Construction

Construction is the matter of how everything or patterns have been put together. Figure 2 shows pattern alignment variations.

Figure 2.

Pattern alignment variations: (a) and (b).

3.3.3.3 Technology

The manufacturing process is a key factor to leather products’ quality. A different technology represents a different style of leather products. The quality of bags is as good as the people that make it. That is why the best stitchery, leather workers, and quality control technician or experts are required. In order to have best-quality products and workers, it is important to put a lot of resources into training or hiring the most qualified staff and paying them well fostering their commitment and creative minds.

3.4 Defects in goods and garments manufacturing

3.4.1 Defects and their types

Defects are deviations/nonconformities of processes, products, or materials from the requirements/standards. Causes of defects may be man-made (assignable causes) or common/natural causes. Assignable causes can be removed, while common causes can only be reduced. For example, a poorly build knife maybe a cause for cutting defects/human fault, while loose leather is a cause for less durability of the garments.

3.4.2 Methods of identifying and isolating faulty pieces

• Defects in the cutting section can be identified by various bodies operating therein that are briefly presented as follows:

Cutting supervisors: they are the cutting supervisors that issue leather from raw material store where defects like loose leather, under substance, wrong color/shape, poor nap on nubuck, poor color fastness, and poor knife can be visually identified, and the leather is thereafter sorted accordingly. Only leather bundles that meet specifications are issued and allocated among cutting operators by the supervisors.

Cutting operators: they can identify during cutting minor defects like grains not matched pair wise, wrong direction of cutting, cuts/flaws in component, open defect, wrong size cut, and color variations to name but a few. These operators, in addition to cutting operations, have the responsibility to take care of component quality. As such, items ought to be cut in line with the parameters stated earlier and the data be posted to the operators.

• Defects in the stitching (sewing) section can be identified by various bodies operating therein.

1. Bench workers can identify defects like notch marks not matched, edge folding inaccurate, improper alignment, wrong components placement, too much hammering, and too much glue.

Stitching operators: they can identify minor defects like uneven stitching length, skipped stitches, stitches not locked at the end, wrong needle/thread used, stitches too far or too close to the edge, stitches not as per the marking, broken stitches, top tension tight, and seam puckering.

Possible defects during the final inspection stage may be:

• trimming,

• thread burning,

• glue erasing,

• leaving uneven stitching length,

• pattern vs. assembly correspondence,

• measurement and alignment,

• grain structure checking,

• component checking,

• color and size matching,

• ironing dimension,

• seem puckering,

• proper feeding system,

• thread tension,

• leaving broken stitches and skipped stitches,

• stitches too far or too close to the edge,

• top tension tight, thickness, and not ±0.2 mm allowances [8].

3.5 Part five: Finishing in leather products manufacturing

Finishing is the final process given to a garment or goods in order to achieve good appearance, desirable feel and look and to impart some important, and durable and functional properties.

3.5.1 Classification of finishing

Finishing in leather products manufacturing can be classified according to the nature of the finish such as Kawabata’s Evaluation System for Fabric-KES-FB and the degree of performance (ISO11644:2009). Figure 3a and b show these classifications.

Figure 3.

Classifications based on (a) the nature of finish (KES-FB) and (b) the degree of performances as per ISO11644:2009.

3.5.2 Edge coloring

Sand edges: this is done by using emery paper to sand the edges and to arrange many belts/straps of the same size side by side on a flat table and sand simultaneously. This will ensure that all the leather layers are even and square and that any residual glues or finishes have been removed. Figure 4 shows edge coloring in industry.

Figure 4.

Edge coloring in practical.

Applying color: this is done either by using a machine or manually. For manual operation, the use of dye box like Fiebing’s dye will make it simpler. Keeping the dyed edge by facing up for air-drying before applying on the opposite edge is worthy. After the other side got dried, one can paint the opposite one and keep the same way one has done previously. It can also be applied during the second round if necessary. This method is used everywhere globally even though manual coloring is preferably practical in Ethiopian leather products manufacturing firms. Figure 5 indicates the application of color with the aid of a machine.

Figure 5.

Applying color with machine.

Applying filler: the leather filler paste is a white compound that can be air- or heat-dried and requires re-coloring with a leather repair pigment after its application. The leather filler remains flexible, durable, and natural to the existing leather surface. It is used to fill the edge surface and results in smoothness to the edge’s surface (see Figure 6).

Figure 6.

Leather filler paste.

Wet and soap: the edge of the leather can be wetted using a sponge or piece of trimmed woolskin. The outcome will be a slick/polished rounded edge.

Burnishing: this is accomplished by briskly rubbing the canvas against the edge of the belt until the edge is smooth. A canvas wrapped around a motorized wood burnishing wheel which speeds up the process could be used herein. However, care should be taken not to over-burnish, which will result in a rough edge.

Hand burnishing: this is done by means of a clean cloth that rubs the edges removing hence, any residual dye and determining thus, if the second coat is necessary.

Polish: at this point, paraffin is applied to the edge of the belt and burnished again and again. Denim works well here if burnishing is done by hand. Once one is satisfied with the finish, one can polish to a high luster with a dry cloth [9].

Finish: after the edges are polished, final finish is applied.

3.5.3 Trimming: Hand trimming and trimmer machine

It is preferred to use thread trimmer machines as it reduces trimming costs, increases production, uses unskilled help, eliminates scissor damage, keeps trimming area clean, and reduces cleanup cost. One can choose between different clipper blades and motor control for diverse material. Scissors can be used for trimming (Figure 7).

Figure 7.

Scissors for trimming.

Thread burning: it can be manual with a candle or by means of soldering iron (Figure 8).

Figure 8.

Soldering iron used for thread burning.

4. Discussion

The quality control concept is very useful especially for exports of branded products. Apart from the general knowledge and experience of the author in the sector, secondary sources were used from institutions such as the Ethiopian Leather Industry Development Institute (LIDI), Ethiopian Leather Industry Associations, and medium- and large-scale leather products manufacturers. The LIDI laboratory was accredited from SANAS (South African National Accredited System) so as to support the leather sector with various laboratory testing (i.e. physical, mechanical, and chemical) services in 2012. Furthermore, the LIDI laboratory was also accredited from the Ethiopian National Accreditation Office (ENAO) in the same year.

With this responsibility, LIDI has been serving Ethiopian leather manufacturing firms by laboratory testing, technical training, quality management system (QMS), and quality control and quality assurance tools implementations. Under the Twinning program, which was made between LIDI and the Federal Democratic Republic of Ethiopia, FDRE, Ministry of Industry on Ethiopian side, and CSIR – Central Leather Research Institute-Council of Scientific and Industrial Research, India, in association with Footwear Design and Development Institute (FDDI), India, LIDI’s R&D laboratory state of the art was created to meet the requirements and demands of leather and leather products in order to meet and ensure international quality standards [10].

Most of leather goods and garment manufacturing companies in Ethiopia use smell test, function test, and color fastness check on leather accepting it as internal company policy, as it matches with some of global/international standards in this aspect (ASTM D1296, ISO 11640, ISO 11641, SLF 401, IUP 470).

Apart from common quality parameters, there are also other leather goods-specific quality parameters. Items made from real leather or imitations, such as PU, which are very popular, should be treated accordingly. However, leather goods and garment manufacturing companies prefer to use simpler (by observation and manual tests) methods, whereas other manufacturers in footwear subsectors could use more test methods as per international standards in order to check, for example, grain structure, thickness, apparent density, shrinkage, flex resistance, water resistance, and so on as per ISO 2589:2002, ISO 2420, ISO 5402, ISO 3380, ISO 5403. That is because, footwear products are highly vulnerable to damage, and hence, their suitability to use needs to be assured before reaching the end users. Table 2 provides a summary of physical testing standards for leather that could be recommended by the author to be used so as to improve productivity and reduce defect rates, rework, and waste.

S.No.	Types of test	Test method
1	Determination of thickness	ISO 2589:2002
2	Determination of apparent density	ISO 2420
3	Determination of tensile strength and percentage elongation	ISO 3376
4	Determination of tearing load (single and double)	SO3377---1/3377---2
5	Determination of distension and strength of grain ball burst	ISO 3378
6	Determination of flex resistance by flexometer method	ISO 5402
7	Determination of shrinkage temperature up to 1150°C	ISO 3380
8	Water absorption (Kubelka) after 2 and 24 h	SATRA TM/ISO SLP 19
9	Determination of water resistance test for light leather	ISO 5403
10	Determination of water resistance of heavy leather	ISO 5404
11	Determination of water vapor permeability	ISO 14268
12	Determination of cold crack resistance leather finish	SLP 34
13	Determination of sole/upper adhesion tester	Internal
14	Measurement of shoe flex (walk meter)	Internal
15	Determination of dry heat resistance of leather	Internal
16	Determination of adhesion of leather finish	SLF 11
17	Color fastness to artificial light (xenon)	SLF 401
18	Determination of fastness to water spotting	ISO 11642
19	Color fastness to perspiration	ISO 11641
20	Determination of fastness of leather finish to (to and from rubbing)	ISO 11640
21	Determination of fastness to ironing (fastness to heat)	IUP 470
22	Determination of static water absorption	ISO 2417

Table 2.

Leather physical testing.

Source: Leather Industry Development Institute’s Physical Laboratory, March 23, 2016.

Regarding the effect of human factors in product quality, it is the author’s view that most quality problems are caused primarily by a lack of interest or care on the part of the worker in the production department. However, it is usually not only the worker who is responsible for this but also the conditions necessary to carry out the work correctly often do not exist. For example, instructions may be inadequate, the incoming material may be defective, the machines may not be capable of producing goods of the required quality, and proper conditions for conducting inspection of the product are not given to the workers, and so on. The study done by joint consultancy of Ethio-Indian twinning project in collaboration with the Leather Industry Development Institute (LIDI) and the Footwear Design and Development Institute (FDDI) of India approves this fact [11]. Figure 4 (in Section 4.1) shows that inadequate instructions, which accounts for about 28% caused the rest effects. Effective understanding of the worker to the instructions in every step of production will surely lead to more pleasant effects on the product quality. However, although workers may not have control over these factors, they may though lead to defective work. Figure 9 shows Pareto analyses of one factory.

Figure 9.

Result of Pareto analysis for ELICO-universal leather products unit. Source: Twinning report [11].

In Japan, it is generally believed that 40% of quality problems are caused by poor product design, 30% of quality problems are due to wrong or defective materials being purchased from suppliers, and the remaining 30% are due to errors made during the manufacturing process [12]. One could argue that any other quality problems in manufacturing are caused in equal proportion by managers (by not providing adequate training for workers) and by workers (by not paying adequate attention to machine settings).

Regarding defects observed in goods and in garments manufacturing listed in the following section are common examples of deficiencies in leather products manufactured in Ethiopia:

Sewing defects: open seams, wrong stitching techniques, non-matching threads and missing stitches, improper creasing of the garment, erroneous thread tension and raw edges are some of the sewing defects which can affect the garment quality adversely. Firms mitigate these types of defects by providing continuous on-the-job trainings for sewing operators.

Color defects: this category includes color variations between the sample and the final garment, wrong color combinations, and mismatching dyes’ that should always be avoided. Leather issuers check this in store for every order with the help of leather sorter or in-process quality inspector.

Sizing defects: this refers to wrong gradation of sizes and difference in the measurement of various parts of garment-like sleeves of XL size for a body of L size garment that can deteriorate the garments beyond repair. Though tanneries use leather grading machine during production, Ethiopian leather goods and garment manufacturing firms usually identify and mitigate these defects by cross-checking cut components visually.

Other defects: this group entails broken or defective buttons, snaps, stitches, different shades within the same garment, dropped stitches, exposed notches and raw edges, fabric defects, holes, faulty zippers, loose or hanging sewing threads, misaligned buttons and holes, missing buttons, needle cuts or chews, pulled or loose yarn, stains, unfinished buttonhole, short zippers, inappropriate trimmings, etc. These defects, unless tackled at the very beginning, and/or quality assurance is undertaken in every step, could lead leather products manufacturing companies to be less competitive and affect in turn their existence. Due to globalization and acceptance of Ethiopian leather products to export markets, manufacturers of leather products are obliged to implement various quality improvement tools including QC/QA. Thus, respective process and final quality checking parameters have been posted in front of operators in each section along with visual defective and free cut components. This method encourages operators to think about quality issues in addition to their duties of – say – cutting, table work, sewing, and finishing.

Concerning defect control at the finishing section, various final quality control parameters are used that include trimming, thread burning, glue erasing, pattern vs. assembly correspondence, thread tension, leaving broken stitches and skipped stitches, and stitches too far or too close to the edge.

As for Ethiopian leather products manufacturers, the defect control parameters during the final inspection stage include aspects such as:

• leaving uneven stitching length,

• measurement and alignment,

• grain structure checking,

• component checking,

• color and size matching,

• ironing dimension,

• seem puckering,

• proper feeding system,

• top tension tight and thickness, etc., are inspected prior to this stage.

5. Conclusion and further work

The leather sector’s contribution is very high with respect to export incomes and economic development, especially on creating job opportunities. For instance, according to the Central Statistical Agency (CSA) of Ethiopia, export of leather and leather products, which was US $23 million in 2013, reached US$133 million in 2018. Hence, leather goods and garment to be exported need high care during all manufacturing stages in order to increase competitiveness in the global market.

This book chapter discussed quality control concepts and quality standards for leather goods and garment. In doing so, it highlighted applicable procedures and documents enabling supervisors, quality controllers, and operators in those companies to get detailed knowledge about quality parameters and control mechanisms so that defect-free products reach end users. Furthermore, it will allow readers to familiarize themselves with quality concepts in this sector. It is the author’s view that this research work may prompt readers to confront themselves with quality control aspects and to research more about these aspects in this specialized manufacturing area.

Moreover, leather goods and garment quality parameters and factors that influence the quality of leather goods and garment were included. In addition to the earlier-mentioned ones, commonly occurring defects, methods of identifying and isolating faulty pieces, and some finishing types in leather products production were discussed.

Studying the application of QC/QA on the whole leather sector (leather processing, footwear industry, glove making, and other related subsectors) will be the next tasks of the researchers and book writers. This may include subsector-specific inspection and control mechanisms starting from designing, cutting, table work (preparation), sewing, inspection and testing, packing, and shipping that need to be further analyzed.

Acknowledgments

The author would like to express his gratitude to his wife for her patience and assistance.

Further reading

To get more practical explanation of quality aspects, readers are advised to read of the work of David Garvin (1988) – Eight Dimensions of Quality.