Grading of quality and diagnostics of defects in goods...

Chapter 12. Grading of quality and diagnostics of defects of goods

Product quality gradations are categories that rank products of one name from the highest to lowest quality grades based on quality and defect values.

In GOST R ISO 9000-2001 Quality management systems. Basic Terms and Dictionary the following definition is given: "Gradations are a class, grade, category or category assigned to different quality requirements for products, processes or systems that have the same functional application."

Products, depending on the presence of defects are divided into standard and non-standard, fit and unfit for consumption or operation.

The annual product satisfies all established requirements; the unfit does not meet the requirements, is recycled or recycled.

Defect - each individual non-compliance of the goods with the established requirements, i.e. local or widespread violations of the structure, appearance of materials and finished products; natural defect of goods, and also appeared when using raw materials, processing, packaging, transportation or storage. These can be holes, cracks, stains, shells, impurities, disruptions in the structure of the material or finished product, etc. Defects are characterized as obvious, critical, significant, insignificant, disposable, unrecoverable, small and large, local and common.

Explicit defects are defects, in order to identify which in the normative documentation required for this type of control, appropriate rules, methods and tools are provided. They are usually determined by a visual method - by inspecting the product and locating the location, the number and size of the defects.

For example, the presence of cracks and fallen knots on the facial lacquered surfaces of furniture.

Hidden defects are not detected by the usual methods. In products made of metals - it's internal voids: shells, cracks; in wood - knots and rot.

In terms of the degree of influence on the state of the goods, critical, significant, minor defects are identified.

If the critical defect is used, the use of the product for its intended purpose is almost impossible and unacceptable (the color TV tuner inoperability, shoe design defects affecting the anthropometric properties).

A significant defect significantly affects the use of the product for its intended purpose and (or) its durability, but is not critical. For example, the formation of carbon deposits on the spark plug of a gasoline engine of a car is a significant defect, since it indicates a malfunction of the engine and causes a decrease in its life. Large internal stresses, inclusions, bubbles in glassware, lowering thermal stability and strength can also be attributed to this type of defects.

A minor defect does not significantly affect the use of products for their intended purpose and its durability. Let's admit, deviations in the form, size, coloring of fruits and vegetables. To insignificant defects can be considered pollution and stains on clothing, which worsen the appearance of products.

If possible, the defects are divided into removable and unrecoverable. Eliminate Defect is a defect whose elimination is technically possible; irremovable - defect, the removal of which is technically impossible or economically impractical.

A product that has at least one defect is called defective.

When determining the quality of a product within a manufacturing plant, the defectiveness factor may be the average weighted number of defects per unit of product.

The presence of defects in the product reduces the quality. The degree of reduction in each particular case depends on the size, number, significance of defects, locations, etc.

Some defects worsen only the appearance of the products, but do not affect the wear resistance and other properties of the product, for example, pattern disturbance, local contamination, stains that do not affect strength, etc. The significance of these defects is determined by the purpose of the products, their main function. So, for artistic and decorative goods (decorative vases, carpets, etc.), appearance defects sharply lower the use value of products, for household goods their presence is less significant.

Defects affecting the operational properties of the product, on the hygienic properties, strength, reliability in use, most significantly reduce the level of product quality. These include defects in the design of shoes, affecting the hygienic properties of the product, defects in the glass, reducing the heat resistance and strength of products, etc.

Defect detection methods are used to determine or diagnose defects, which is a set of methods for determining the macrostructure of homogeneous substances, foreign inclusions, shells, voids and cracks in materials. Most often this diagnosis is used in the study of the quality of building materials and household goods made of metals and alloys, plastics. The main and most common methods are magnetic and ultrasonic flaw detection.

The method of magnetic flaw detection is that when you magnetize metal products, the places under which defects are located, are magnetized differently than a solid metal product. Then, the degree of magnetization is determined and the locations, sizes and shape of the defects are established.

Ultrasonic flaw detection is based on the use of ultrasonic waves, which are reflected almost completely at the solid-air interface. Analysis of reflected sound waves shows the location of defects.

In some cases, X-ray flaw detection is based on the different X-ray permeability through different materials and air voids. This method uses radioactive isotopes to analyze the composition, structure and various properties of materials and products. Without dwelling in detail on the description of the areas of application of β-particles and γ-rays, we note

the successful use of β-particles in the analysis of alloys, the use of γ-rays in the study of corrosion processes, to determine the density of various substances, etc.

Many goods are divided into varieties, brands, classes of complexity.

Product Variety - is the compliance of products produced by their technical and economic parameters and consumer properties to certain quality groups (grades), provided by applicable standards and specifications.

Product grade is the grading of a certain type of goods according to one or more quality indicators established by the regulatory documentation.

Typically, varieties are divided into food, light, textile and woodworking industries. The grade of the goods characterizes the degree of conformity of the product quality indicators with the established standards. Depending on the compliance of the product with the standards, one or another grade of goods is established and is indicated by the serial number - 1, 2, 3, 4; with the letters a, b, c; terms - extra & quot ;, "luxury", "prima", "higher", selected or with symbols and signs.

Abroad, the product grade ratio (Product grade ratio) is used abroad to characterize the quality of products manufactured by the enterprise - the ratio of the total cost of products produced during the considered time interval to the total the cost of the same products in terms of the highest grade. This coefficient characterizes the quality of the entire volume of the various products manufactured by the enterprise.

Goods that do not meet the requirements for the highest quality category are transferred to a lower category, and not meeting the requirements of the lowest grade, are marred.

Marriage is a product, the transfer of which to the consumer is not allowed due to defects. There are goods that do not divide by grade.

The product variety is installed by the manufacturer's controllers and checked by representatives of trade organizations that purchase and sell products to consumers, as well as experts from the Federal Service for Consumer Protection during inspections.

The methodology for determining the category of product quality is based on establishing the presence of defects, clarifying their location, counting the quantity, measuring their size or determining the values ​​of the criterial quality indicators of goods.

There are point and restrictive methods for establishing the type of goods.

The ball method is based on the establishment of the grade by the number of points. In this case, each defect or deviation from the norm is assessed by a certain number of points, taking into account its significance and the magnitude of the deviation from the norm.

The restrictive method is based on establishing for each variety a list of defects, their size, location, quantity. If the defect differs according to the types and characteristics with the established requirements, the goods are transferred to the lower grade.

For example, garments are divided according to the level of production performance in the 1st and 2nd grade; Fur skins, depending on the condition of the hair and skin tissue, are divided into 1st, 2nd, 3rd grades: 1st grade skins are full-bodied with flat awn and thick down, and third-grade skins are semi-hair.

Defects of knitted products are divided into defects of the appearance of the canvas and production-sewing. Products of the 1st grade comply with the requirements of normative documents and standard samples. Exceptional (hardly noticeable) defects of the canvas and manufacturing defects that do not affect the consumer properties of the goods are allowed. Products of the 2nd class may have defects permitted by regulatory documents.

Defects of garments by nature of origin are divided into defects of production and non-productive nature. Defects of a production nature, in turn, are divided into production-sewing and defects in the appearance of materials.

In the process of making garments, defects may occur (trimmed, shortened or skewed parts), the mismatch of the pattern lines in the symmetrical parts of the product from the materials with the pattern, the defects in joints (seams, stitches, stitches), defects in wet-heat treatment and final finishing operations.

Defects in the appearance of materials found in finished products are subdivided into local materials located on a limited area (for example, in fabrics - thickened threads, whiteness, knocked-down pattern, etc.), and common, inherent in the whole product or individual its details.

Toilet soap, depending on the formula, is divided into neutral, child, extra, ordinary.

The paper for printing, depending on the fibrous composition, is divided into numbers.

Wood materials are also divided into varieties depending on the species, number and size of defects. Defects of wood are divided into nine groups: knots, cracks, the shape of the trunk, the structure of wood, mushroom damage, insect damage, foreign inclusions, deformations, chemical stains. Each group is divided into species and varieties.

On the quality category, there are video tapes, audio and video recordings. Video quality categories: super (SH), extra (H), prima (P), standard (ST).

Photos taken by digital cameras, too, can be divided into categories: SHQ, HQ, SH1, SH2, which are due to different photography resolutions. For example, the camera can provide the following image options (Table 12.1).

Table 12.1

Image quality categories and image format

Image Quality Category

SHQ

HQ

SH1

SH2

Image size (pixels horizontally - vertical)

2560 for 1920

2048 to 1536

640 by 480

320 by 240

The European Organization for Standardization adopted the classification and the system based on it for the coding of electrical household appliances and appliances. The goods are divided into classes (A, B, C, D, E, F) depending on the economy and efficiency of functioning. For example, for household electric washing machines, classes are established based on the values ​​of electricity consumption, washing efficiency, water consumption per wash.

At manufacturing enterprises, in a number of cases, an assessment is made of the level of quality of the product's manufacturing, i.e. degree of compliance with the requirements of regulatory and technical documentation of the actual values ​​of the quality indicators of the goods prior to the commencement of its operation or consumption. To characterize the defectiveness of the goods, the defectiveness coefficient, is determined as follows. A sample is taken from n units of production and counts all the defects broken up in advance into a species.

For each type of defect, the weighting coefficient r i is set, where i = 1, 2, 3, α . The coefficient of defect weight is determined by the expert method or by the cost of eliminating the defect of this type.

(81)

where m i - the number of defects of each type of sample.

Let's consider an example and we will make calculations proceeding from the data of tab. 12.2. From a batch of power tools (electric drills) of 1000 pieces, a sample of 20% is taken. Inspection and testing were carried out.

Table 12.2

Power tool defects

The following defects are installed:

Number of products

The weight of the defect, r i

Obloy on the case

328

0.05

The fastening screws are not tightened

19

0.05

The motor does not turn on

2

0.4

The free path of the start button is broken

48

0.15

Lashing on the power cord plug

490

0.05

Backlash of the chuck

1

0.3

ri = 1

D = (382-0.05 + 19 0.05 + 2 - 0.4 + 48 - 0.15 + 200 - 0.05 + 1 x 0.3): 200 = 19.1 + 0.95 + 0.8 + 7.2 + 10 + 0.3 = 0.19.

Also We Can Offer!

Other services that we offer

If you don’t see the necessary subject, paper type, or topic in our list of available services and examples, don’t worry! We have a number of other academic disciplines to suit the needs of anyone who visits this website looking for help.

How to ...

We made your life easier with putting together a big number of articles and guidelines on how to plan and write different types of assignments (Essay, Research Paper, Dissertation etc)