First, the common quality inspection of export products
Common inspection methods
(a) full and sampling inspection.
1, the full number of inspections is to be examined 100% of the product batch by batch inspection, also known as full inspection or 100% inspection.
This quality inspection method is applicable to the production of very small batches of large-scale electromechanical equipment products, most of the production of large batches of products, such as electronic components is very unsuitable. When the quality inspection is destructive, such as the life of the TV test, the strength of the material product test, etc., the full inspection is impossible.
2, sampling test is from a batch of products (overall), randomly select the appropriate amount of product samples for quality inspection, and then compare the test results with the determination of the standard, so as to determine whether the product is qualified or need to carry out another sampling after the verdict of a quality inspection method.
(ii) counting and measurement test.
1, counting test. Counting test of the count value of quality data can not be taken continuously, such as the number of unqualified, the number of defects, the number of defects.
2, measurement test. Metrological inspection of the measured value of the quality data can be taken continuously, such as length, volume, weight, concentration, temperature, intensity, etc.
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(C) physical and chemical and sensory inspection.
(1) physical and chemical inspection is the application of physical or chemical methods, relying on gauges, instruments and equipment and devices to test the inspected object. Physical and chemical tests are usually measured to test the specific value of the project, high precision, small human error. Physical and chemical inspection is the main body of a variety of inspection methods, especially by people's attention.
(2) sensory inspection is to rely on the human sensory organs to evaluate and judge the quality characteristics or features. Such as the shape of the product, color, smell, scars, stains, rust and aging, etc., often rely on the human sense organs to check and evaluate.
Therefore, the results of sensory inspection often rely on the experience of the inspector, and there is a greater volatility. In spite of this, but due to the limitations of the current development of physical and chemical inspection technology and the diversity of quality inspection issues, sensory testing in some occasions is still a choice of quality inspection methods or supplement.
(d) destructive and non-destructive testing.
Destructive testing, the inspected items no longer have the original function, such as life test, strength test and explosion test. Destructive testing can only be used in the form of sampling.
(e) fixed and mobile inspection.
(1) fixed inspection is centralized inspection, refers to the establishment of a fixed inspection station in the production enterprise, the work site after the processing of products sent to the inspection station centralized inspection.
(2) mobile inspection is by the inspector directly to the work site inspection.
(F) acceptance and monitoring inspection.
(1) acceptance inspection exists widely in the whole production process, such as raw materials, purchased parts, outsourcing parts and supporting parts of the incoming inspection, semi-finished goods warehousing inspection, factory inspection of finished products. The purpose of acceptance inspection is to determine whether the object is qualified, so as to make the decision to accept or reject.
(2) monitoring inspection, also known as process inspection, the purpose is to determine whether the production process is in a controlled state, in order to prevent the emergence of systematic quality factors that lead to the emergence of a large number of substandard products. Such as the production process quality control in a variety of sampling inspection is to monitor the test.
Second, the sampling test method
Sampling test is the most used form of quality inspection of foreign trade exports, China has so far developed a sampling method standard:
GBl0lll use of random numbers for random sampling methods; GBl3393 principles of sampling; GB6378 Failure rate of measurement sampling inspection procedures and charts (corresponding to ISO3951); GB8051 counting type sequential sampling inspection program. These sampling method standard normative documents, respectively, on the enterprise sampling test and the national industry quality sampling test method to make clear provisions, in the actual process of single need to understand and master.
(a) the basic terminology in the sampling inspection
1, batch: a certain number of products manufactured under the same conditions, known as ? batch? In 5M1E (that is, man, machine, material, method, measurement, environment) is basically the same production process in the continuous production of a series of batches is called a continuous batch; can not be designated as a continuous batch of batches is called an isolated batch.
5M1E refers to:
① People (man), including human quality awareness, responsibility, technical and business level, operational proficiency, physical conditions. ② instrumentation (machine), has been tested and calibrated, whether the normal operating conditions, whether there is a strict management and use of the system and so on. ③ material (material) including reagents, drugs, experimental animals, etc. whether the standard is valid. Reagents and drugs are labeled manufacturer, expiration date, content; experimental animals are clear, species, grade, age, sex, adaptation, feeding and so on. Measurement (measure), including the precision of the test instrument and measurement methods, etc., whether there are clear provisions, and strictly enforced. ⑤ method (method), including process technology routes, operating procedures, organizational and management methods, such as standardization, standardization, procedural; job responsibility and assessment is sound; ⑥ environment (environment), including temperature, humidity, dust content, noise, vibration, lighting, sanitation, and other conditions, the control of the conditions have been controlled
2, unit product : For the implementation of sampling needs to be divided into basic units called unit products.
3, batch and sample size: batch is the number of units contained in the batch of products, expressed in terms of N. The sample size is the number of units contained in the batch of products. Sample size refers to the number of unit products in the randomly selected samples, expressed in n.
4, samples and sample units: from the inspection batch for the inspection of the unit product is called a sample unit. And the sample unit of the whole is called the sample. Sample size is the number of sample units contained in the sample.
5, Acceptable Quality Level (AQL) and Unacceptable Quality Level (RQL): In the sampling inspection, the process average of consecutive submissions of the inspection lot is considered acceptable upper limit value, known as the acceptable quality level. The process average is the average quality of a series of initial submissions to check the average quality of the batch, it is expressed in the number of defective products per 100 units of product or per 100 units of product failure; the specific value of the two sides by the production and demand negotiation to determine the general sign by the AQL symbols; in the sampling inspection, that is unacceptable batch of the quality of the lower limit, known as the level of quality of the unqualified, with the symbol of the RQL said.
6, inspection and inspection level (IL): measurement, test or other methods, the unit of product and technical requirements of the comparison process is called inspection. Inspection has a normal check, tighten the check and relax the check.
7, two types of risk a and ? : Because of the randomness of the sampling test, the original qualified batch, the probability of misjudgment for the rejection, which is unfavorable to the production side, and therefore known as the first type of risk or producer risk, expressed as a; and originally unqualified batch, there is a possibility of misclassification of the acceptance of the use of the party will be unfavorable to the probability of the type of risk known as Type II risk or the risk of making use of the party, to ? expressed.
8, sampling program
Sample size or sample size series and judgment array combined, known as the sampling program. And the judgment array is a series of qualified judgment number and unqualified judgment number or qualified judgment number series and unqualified judgment number series combined together.
Sampling program has a primary, secondary and quintuple sampling program.
A primary sampling plan is a sampling plan that consists of a combination of sample size n and a set of determinations (Ac, Re).
Ac is the number of passing judgments. Judgment batch qualified, the sample contains the maximum number of nonconforming products (d) is called qualified judgment, also known as the number of acceptance (d? Ac).
Re for the number of unqualified decisions, is to determine the batch of unqualified, the sample contains the smallest number of unqualified products, also known as the number of rejections (d?Re).
Secondary sampling program is the first sample size n1, the second sample size n2, ? and the judgment array (Ac1;Ac2, Re1;Re2) combined together to form a sampling scheme.
A five-sample scheme, on the other hand, is one that consists of a first sample size n1 a second sample size n2, ? fifth sample size n5 and the judgment array
(A1, A2, A3, A4, A5, R1, R2, R3, R4, R5) combined together to form the sampling scheme.
(ii) Classification of sampling methods
1, according to the product quality indicator characteristics classification
Quality indicators can be divided into two categories according to their measurement characteristics of metrological indicators and counting indicators. Measurement indicators are such as the purity of the material, the size of the processed parts, the chemical composition of steel, product life and other quantitative data indicators. Counting indicators can be divided into counting indicators and counting indicators of two kinds, the former to the number of defective products to measure, the latter refers to the number of defects in the product, such as a square meter of fabric on the number of defects in the appearance of a casting on the number of bubbles and trachoma, and so on. According to the classification of quality indicators, product quality inspection of sampling inspection method is also divided into counting sampling and measurement sampling method of two categories.
2, according to the number of sampling inspection classification (slightly)
According to the number of sampling inspection can be divided into a one-time, two-time, multiple and sequential sampling inspection methods.
① A sampling method. The method is the simplest, it only requires sampling a sample can make a batch of products whether qualified 'judgment.
② secondary sampling method. First sampling the first sample for inspection, if you can make a batch of products according to the judgment of qualified or not, the test is terminated. If you can not make a judgment, then take a second sample, and then again after the test to make a judgment on whether it is qualified.
③ multiple sampling method. Its principle is the same as the secondary sampling method, each time the sample size is the same, that is, n, = n2 a n.? = n but the number of sampling is more, the number of qualified judgments and unqualified judgments are also more. IS () 2859 standard provides 7 times sampling program. China GB2828, GB2829 are implemented 5 times sampling program. GB/?r?2828.1 is a counting sampling inspection standard, only applicable to counting sampling inspection occasions, mainly used for continuous batch-by-batch inspection can also be used for isolated batch inspection. But for isolated batch occasions, the user should carefully analyze the OC curve, from which to find the required protection ability of the program. GB/T 2828.1 sampling program is mainly applicable to the following inspection scope: final product; parts and raw materials; operations; in-process; inventory; maintenance operations; data or records; management procedures.
④ sequential sampling method. Equivalent to the limit of multiple sampling methods, each time only a unit of product randomly selected for inspection, inspection, that is, according to the rules of the decision to make qualified, unqualified or re-draw the next unit of product judgment, once the batch can be made qualified or unqualified judgment, the termination of the test.
3. According to the sampling method form classification
Sampling method can first be divided into two categories of adjustable and non-adjustable. Adjustment type is a few different sampling program and transfer rules linked together to form a complete sampling system, and then according to changes in product quality of each batch, according to the transfer of rules to replace the sampling program that is normal, toughened or relaxed sampling program conversion, ISO2859, ISO3951 and GB2828 standard belongs to this type of adjusted sampling method is applicable to the quality of each batch of linked Quality inspection of consecutive batches of products. Non-adjustable single sampling inspection program does not take into account the quality of the product batch history, the use of no transfer rules, so it is easier for the quality inspectors to master, but only on the quality of the isolated batch inspection is more appropriate.
Third, the export of products counting sampling method
1. counting sampling method
According to the number of samples, divided into one, two and more counting sampling inspection methods.
(1) counting a sampling inspection method. This is one of the most basic and simplest sampling inspection method, it is the overall N to take n samples for inspection, according to the n in the number of defective products d and pre-specified number of permissible defective products C (can also be recorded as A.) Comparison, so as to determine whether the batch of products are qualified.
(2) counting the second sampling inspection method. This sampling method is developed on the basis of a sampling method. It is the delivery of the batch of two samples n1, n2 (GB2828 in the provisions of n1 = n2) corresponds to the number of two qualified judgement C1, and C2:, the number of unqualified judgement for ?1, ?2 two samples of the number of unqualified were d1, and d2:, the sampling and judgment process
The first step: first take the first sample n1, after the inspection, such as the number of non-conforming products is d1, ? C1, judged to be qualified; such as d1?1, judged to be unqualified, when C1?d1?1, it is necessary to determine the second sample.
The second step: n2 in the number of substandard products d2, by d2 and d1 added together with C2?2 for comparison, such as d1 + d2?C2, judged qualified; when d1 + d2?2. judged unqualified.
(3) counting multiple sampling inspection. Counting multiple sampling inspection procedures and counting the second sampling similar, but the number of sampling more, qualified and unqualified number of judgments and unqualified number of judgments is also more, because each time you take the same size of the sample, so sampling more than the sample is small. Our GB 2828 and GB 2829 regulations are five sampling program.