This article summarizes the classification of 11 quality inspection methods, and introduces each type of inspection. The coverage is relatively complete, and I hope it can help everyone.
01 Sort by order of production process
1. Incoming inspection
Definition: The inspection conducted by the enterprise on the purchased raw materials, purchased parts, outsourced parts, supporting parts, auxiliary materials, supporting products and semi-finished products before storage. Purpose: To prevent unqualified products from entering the warehouse, preventing the use of unqualified products from affecting product quality and affecting the normal production order. Requirements: Full-time incoming inspectors shall conduct inspections in accordance with inspection specifications (including control plans). Classification: Including the first (piece) batch of sample incoming inspection and bulk incoming inspection.
2. Process inspection
Definition：Also known as process inspection, it is an inspection of product characteristics produced in each manufacturing process during the product formation process. Purpose: To ensure that unqualified products in each process will not flow into the next process, prevent further processing of unqualified products, and ensure normal production order. It plays the role of verifying the process and ensuring the implementation of process requirements. Requirements: Full-time process inspection personnel shall conduct inspection according to the production process (including control plan) and inspection specifications. Classification: first inspection; patrol inspection; final inspection.
3. Final test
Definition：Also known as finished product inspection, finished product inspection is a comprehensive inspection of products after the end of production and before the products are put into storage. Purpose: To prevent unqualified products from flowing to customers. Requirements: The quality inspection department of the enterprise is responsible for the inspection of finished products. The inspection should be carried out in accordance with the regulations in the inspection guide for finished products. The inspection of large batches of finished products is generally carried out by means of statistical sampling inspection. For products that pass the inspection, the workshop can handle the storage procedures only after the inspector issues a certificate of conformity. All unqualified finished products should be returned to the workshop for rework, repair, downgrade or scrap. The reworked and reworked products must be inspected again for all items, and the inspectors must make good inspection records of the reworked and reworked products to ensure that the product quality is traceable. Common finished product inspection: full size inspection, finished product appearance inspection, GP12 (customer special requirements), type test, etc.
02 Classified by inspection location
1. Centralized inspection The inspected products are concentrated in a fixed place for inspection, such as inspection stations. Generally, the final inspection adopts the method of centralized inspection.
2. On-site inspection On-site inspection, also known as on-site inspection, refers to inspection at the production site or product storage place. General process inspection or final inspection of large-scale products adopts on-site inspection.
3. Mobile inspection (inspection) Inspectors should conduct roving quality inspections on the manufacturing process at the production site. Inspectors shall conduct inspections in accordance with the frequency and quantity of inspections specified in the control plan and inspection instructions, and keep records. Process quality control points should be the focus of the itinerant inspection. The inspectors should mark the inspection results on the process control chart. When the tour inspection finds that there is a problem with the quality of the process, on the one hand, it is necessary to find out the cause of the abnormal process with the operator, take effective corrective measures, and restore the process to a controlled state; Before inspection, all processed workpieces are 100% retrospectively inspected to prevent unqualified products from flowing into the next process or the hands of customers.
03 Classified by inspection method
1. Physical and chemical test Physical and chemical inspection refers to the method of mainly relying on measuring tools, instruments, meters, measuring devices or chemical methods to inspect products and obtain inspection results.
2. Sensory test Sensory inspection, also known as sensory inspection, relies on human sensory organs to evaluate or judge the quality of products. For example, the shape, color, smell, scar, aging degree, etc. of the product are usually inspected by human sense organs such as vision, hearing, touch or smell, and judge the quality of the product or whether it is qualified or not. Sensory testing can be divided into: Preference sensory test: Such as wine tasting, tea tasting and identification of product appearance and style. It depends on the rich practical experience of the inspectors to make correct and effective judgments. Analytical sensory test: Such as train spot inspection and equipment spot inspection, relying on the feeling of hands, eyes, and ears to judge temperature, speed, noise, etc. Experimental use identification: Trial use identification refers to the inspection of the actual use effect of the product. Through the actual use or trial of the product, observe the applicability of the product’s use characteristics.
04 Classified by the number of inspected products
1. Full test
Full inspection, also known as 100% inspection, is a full inspection of all products submitted for inspection according to the specified standards one by one. It should be noted that even if all inspections are due to wrong inspections and missing inspections, there is no guarantee that they are 100% qualified.
2. Sampling inspection
Sampling inspection is to select a specified number of samples from the inspection batch according to a predetermined sampling plan to form a sample, and to infer whether the batch is qualified or unqualified through the inspection of the sample.
3. Exemption
It is mainly to exempt products that have passed the product quality certification of the national authoritative department or trustworthy products when they are purchased, and whether they are accepted or not can be based on the supplier’s certificate or inspection data. When exempting from inspection, customers often have to supervise the production process of suppliers. Supervision can be carried out by dispatching personnel or obtaining control charts of the production process.
05 Classification of data properties by quality characteristics
1. Measurement value inspection
The measurement value inspection needs to measure and record the specific value of the quality characteristics, obtain the measurement value data, and judge whether the product is qualified according to the comparison between the data value and the standard. The quality data obtained by the measurement value inspection can be analyzed by statistical methods such as histograms and control charts, and more quality information can be obtained.
2. Count value test
In order to improve production efficiency in industrial production, limit gauges (such as plug gauges, snap gauges, etc.) are often used for inspection. The obtained quality data are count value data such as the number of qualified products and the number of unqualified products, but the specific values of quality characteristics cannot be obtained.
06 Classification according to the status of the sample after inspection
1. Destructive inspection
Destructive inspection means that the inspection results (such as the blasting ability of shells, the strength of metal materials, etc.) can only be obtained after the sample to be inspected is destroyed. After the destructive test, the tested samples completely lose their original use value, so the sample size is small and the risk of testing is high. 2. Non-destructive inspection Non-destructive inspection refers to the inspection that the product is not damaged and the quality of the product does not change substantially during the inspection process. Most inspections, such as the measurement of part dimensions, are non-destructive inspections.
07 Classification by inspection purpose
1. Production inspection
Production inspection refers to the inspection conducted by the production enterprise at each stage of the entire production process of product formation, with the purpose of ensuring the quality of the products produced by the production enterprise. Production inspection implements the organization’s own production inspection standards.
2. Acceptance inspection
Acceptance inspection is the inspection carried out by the customer (demand side) in the inspection and acceptance of the products provided by the production enterprise (supplier). The purpose of acceptance inspection is for customers to ensure the quality of accepted products. The acceptance criteria after the acceptance inspection is carried out and confirmed by the supplier.
3. Supervision and inspection
Supervision and inspection refers to the market random inspection supervision and inspection conducted by independent inspection agencies authorized by the competent departments of governments at all levels, according to the plan formulated by the quality supervision and management department, by sampling commodities from the market or directly sampling products from manufacturers. The purpose of supervision and inspection is to control the quality of products put into the market at a macro level.
4. Verification test
Verification inspection refers to the inspection that the independent inspection agency authorized by the competent government departments at all levels takes samples from the products produced by the enterprise, and verifies whether the products produced by the enterprise meet the requirements of the implemented quality standards through inspection. For example, the type test in the product quality certification belongs to the verification test.
5. Arbitration test
Arbitration inspection means that when there is a dispute between the supplier and the buyer due to product quality, the independent inspection agency authorized by the competent government departments at all levels will take samples for inspection and provide the arbitration agency as the technical basis for the ruling.
08 Classification by supply and demand
1. First party inspection
The first-party inspection refers to the inspection conducted by the manufacturer itself on the products it produces. The first-party inspection is actually the production inspection carried out by the organization itself.
2. Second party inspection
The user (customer, demand side) is called the second party. The inspection carried out by the purchaser on the purchased products or raw materials, purchased parts, outsourced parts and supporting products is called the second-party inspection. The second-party inspection is actually the inspection and acceptance of the supplier.
3. Third party inspection
Independent inspection agencies authorized by government departments at all levels are called third parties. Third-party inspection includes supervisory inspection, verification inspection, arbitration inspection, etc.
09 Classified by inspector
1. Self-test
Self-inspection refers to the inspection of the products or parts processed by the operators themselves. The purpose of self-inspection is for the operator to understand the quality status of processed products or parts through inspection, so as to continuously adjust the production process to produce products or parts that fully meet the quality requirements.
2. Mutual inspection
Mutual inspection is the mutual inspection of processed products by operators of the same type of work or the upper and lower processes. The purpose of mutual inspection is to timely discover quality problems that do not conform to the process regulations through inspection, so as to take corrective measures in time to ensure the quality of processed products
3. Special inspection
Special inspection refers to the inspection conducted by personnel who are directly led by the quality inspection agency of the enterprise and are engaged in quality inspection full-time.
10 Classification according to the components of the inspection system
1. Batch by batch inspection Batch-by-batch inspection refers to the batch-by-batch inspection of each batch of products produced in the production process. The purpose of batch-by-batch inspection is to judge whether the batch of products is qualified or not.
2. Periodic inspection
Periodic inspection is an inspection carried out at a certain time interval (quarter or month) from a certain batch or several batches that have passed the batch-by-batch inspection. The purpose of periodic inspection is to judge whether the production process in the cycle is stable.
3. The relationship between periodic inspection and batch-by-batch inspection
Periodic inspection and batch inspection Constitute a complete inspection system of the enterprise. Periodic inspection is an inspection to determine the effect of system factors in the production process, while batch-by-batch inspection is an inspection to determine the effect of random factors. The two are a complete inspection system for launching and maintaining production. Periodic inspection is the premise of batch-by-batch inspection, and there is no batch-by-batch inspection in the production system without periodic inspection or failed periodic inspection. The batch-by-batch inspection is a supplement to the periodic inspection, and the batch-by-batch inspection is an inspection to control the effects of random factors on the basis of eliminating the effects of system factors through periodic inspections. In general, batch-by-batch inspection only checks the key quality characteristics of the product. The periodic inspection is to test all the quality characteristics of the product and the influence of the environment (temperature, humidity, time, air pressure, external force, load, radiation, mildew, insects, etc.) on the quality characteristics, even including accelerated aging and life tests. Therefore, the equipment required for periodic inspection is complicated, the cycle is long, and the cost is high, but periodic inspection must not be performed because of this. When the enterprise has no conditions to conduct periodic inspection, it can entrust inspection agencies at all levels to do periodic inspection on its behalf.
11 Classified by the effect of the test
1. Deterministic test Deterministic inspection is based on the quality standard of the product, and it is a conformity judgment to judge whether the product is qualified or not through inspection.
2. Informative test
Informative inspection is a modern inspection method that uses the information obtained from inspection for quality control.
3. Causality test
The cause-finding test is to find the possible unqualified reasons (cause-seeking) through sufficient prediction in the design stage of the product, design and manufacture the error-proofing device in a targeted manner, and use it in the manufacturing process of the product to eliminate unqualified product production.
Post time: Nov-29-2022