What is Inspection and Why is It Important?
Quality inspection is a very important and common control method in quality management

What are the inspection methods? What is the purpose of inspection?
What are the types of inspection?

Quality inspection is a very important and common control method in quality management. It detects failure modes to prevent substandard products from flowing into the next link. 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.

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, accessory parts, auxiliary materials, accessory products and semi-finished products before storage.

Purpose: to prevent unqualified products from entering the warehouse, to prevent the use of unqualified products from affecting product quality and affecting the normal production order.

Requirement: The inspection shall be carried out by a full-time incoming goods inspector according to the inspection specification (including the control plan).

Classification: Including the first (piece) batch sample purchase inspection and batch purchase inspection.

2. Process inspection

Definition: Also known as process inspection, it is an inspection of the product characteristics produced in each manufacturing process during the product formation process.

Purpose: To ensure that the unqualified products of each process cannot flow into the next process, prevent the continued processing of the unqualified products, and ensure the normal production order. Play the role of verifying the process and ensuring the implementation of process requirements.

Requirements: The inspection shall be carried out by full-time process inspectors according to the production process (including control plan) and inspection specifications.

Classification: first inspection; patrol inspection; final inspection.

3. Final inspection

Definition: Also known as finished product inspection, finished product inspection is a comprehensive inspection of the product after the end of production and before the product is put into storage.

Purpose: To prevent substandard 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 of the finished product inspection guide. The inspection of large-scale finished products is generally carried out by statistical sampling inspection.

Products that pass the inspection shall be issued by the inspector before the workshop can go through the warehousing procedures. All finished products that fail the inspection shall be returned to the workshop for rework, repair, downgrade or scrapping.

The reworked and reworked products must be inspected for the whole project again, and the inspector must prepare the inspection records of the reworked and reworked products to ensure the traceability of the product quality.

Common finished product inspection: full size inspection, finished product appearance inspection, GP12 (customer special requirements), type test, etc.

Inspection location classification

1. Centralized inspection

The inspected products are concentrated in a fixed place for inspection, such as an inspection station. Generally, the final inspection adopts the method of centralized inspection.

2. On-site inspection

On-site inspection, also known as in-situ inspection, refers to inspection at the production site or where the product is stored. General in-process inspection or final inspection of large-scale products adopts the method of on-site inspection.

3. Flow inspection (inspection)

Inspectors should conduct quality inspection tours of the manufacturing process at the production site. Inspectors shall conduct inspections in accordance with the inspection frequency and quantity specified in the control plan and inspection instructions, and make records.

Process quality control points should be the focus of inspection tours. The inspector shall mark the inspection result on the process control chart.

When the patrol inspection finds that there is a problem with the quality of the process, on the one hand, we must work with the operators to find out the reason for the abnormality of the process, take effective corrective measures, and restore the process to a controlled state; All processed workpieces are 100% traceable and fully inspected before inspection to prevent unqualified products from flowing into the next process or the hands of customers.

Classification by inspection method

1. Physical and chemical inspection

Physical and chemical inspection refers to a method that mainly relies 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 sense organs to evaluate or judge the quality of products. For example, the shape, color, smell, scar, aging degree of the product, etc., usually rely on human senses such as vision, hearing, touch or smell to test, and judge the quality of the product or whether it is qualified.

Sensory testing can be further divided into:

Hobby sensory inspection: 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 inspection: such as train inspections and equipment inspections, relying on the senses of hands, eyes, and ears to judge temperature, speed, noise, etc.

Experimental use identification: Experimental 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.

Classified by the number of products inspected

1. Full inspection

Full inspection, also known as 100% inspection, is a full inspection of all products submitted for inspection according to the specified standards.

It should be noted that even if all inspections are due to errors and omissions, 100% compliance cannot be guaranteed.

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 infer that the batch is qualified or unqualified through the inspection of the sample.

3. Exemption from inspection

Mainly, the products that have passed the product quality certification of the national authoritative department or the trustworthy products are exempted from inspection when they are purchased.

When exempting from inspection, the customer often has to supervise the production process of the supplier. The supervision method can be carried out by dispatching personnel or requesting the control chart of the production process.

Classification by data nature of quality characteristics

1. Measurement value inspection

The measurement value inspection needs to measure and record the specific values of the quality characteristics, obtain the measurement value data, and compare the data value with the standard to judge whether the product is qualified.

The quality data obtained by the measurement value inspection can be analyzed by statistical methods such as histogram and control chart, and more quality information can be obtained.

2. Count value test

In industrial production, in order to improve production efficiency, limit gauges (such as plug gauges, calipers, etc.) are often used for inspection. The obtained quality data is count value data such as the number of qualified products and the number of unqualified products, and the specific values of the quality characteristics cannot be obtained.

Classification by condition of samples after inspection

1. Destructive inspection

Destructive inspection means that the inspection result (such as the blasting ability of the projectile, the strength of the metal material, etc.) can only be obtained after the sample to be inspected is destroyed. After the destructive inspection, the inspected sample completely loses its original use value, so the sample size is small and the inspection risk is high.

2. Non-destructive inspection

Non-destructive inspection refers to the inspection in which 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.

Classification by inspection purpose

1. Production inspection

Production inspection refers to the inspection carried out by the production enterprise at each stage in 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 performed by the customer (purchaser) in the acceptance of the products provided by the manufacturer (supplier). The purpose of the acceptance inspection is for the customer to ensure the quality of the accepted product.

Acceptance inspection is the acceptance criteria confirmed with the supplier.

3. Supervision and inspection

Supervision and inspection refers to the market spot-check supervision and inspection conducted by independent inspection agencies authorized by the competent government departments at all levels, according to the plan formulated by the quality supervision and management department, to extract commodities from the market or directly extract products from production enterprises.

The purpose of supervision and inspection is to macro-control the quality of products put into the market.

4. Verification inspection

Verification inspection refers to the inspection by independent inspection agencies authorized by the competent government departments at all levels to take samples from the products produced by the enterprise and verify 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 inspection

Arbitration inspection means that when there is a dispute between the supplier and the demander over 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 award.

Classified by supply and demand

1. First-party inspection

First-party inspection refers to the inspection of the products produced by the manufacturer itself. First-party inspection is actually the production inspection carried out by the organization itself.

2. Second-party inspection

The user (customer, demander) is called the second party. The inspection performed by the buyer on the purchased products or raw materials, purchased parts, outsourced parts and ancillary products is called 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 competent government departments at all levels are called third parties. Third-party inspections include supervisory inspections, verification inspections, arbitration inspections, etc.

Sort by inspector

1. Self-check

Self-inspection refers to the inspection of the products or parts processed by the operator himself. The purpose of self-inspection is that the operator understands the quality of the 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 the processed products by the operators of the same type or the upper and lower processes. The purpose of mutual inspection is to detect quality problems that do not meet the requirements of the process regulations in time through inspection, so that corrective measures can be taken in time to ensure the quality of processed products.

3. Special inspection

Special inspection refers to the inspection carried out by the personnel who are directly led by the quality inspection agency of the enterprise and are engaged in full-time quality inspection.

Classification by inspection system components

1. Batch inspection

Batch-by-batch inspection refers to the batch-by-batch inspection of each batch of products produced during 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 (quarterly or monthly) from a batch or several batches that have passed the batch inspection. The purpose of cycle inspection is to judge whether the production process is stable within the cycle.

3. The relationship between periodic inspection and batch-by-batch inspection

Periodic inspection and batch-by-batch inspection constitute the complete inspection system of the enterprise. Periodic inspection is to determine the role of systematic factors in the production process, while batch-by-batch inspection is to determine the role of random factors. Both are complete inspection systems for putting into production and maintaining production.

Periodic inspection is the premise of batch-by-batch inspection, and there is no batch-by-batch inspection for a production system without periodic inspection or unqualified periodic inspection. Batch-by-batch inspection is a supplement to periodic inspection. Batch-by-batch inspection is an inspection that controls the effect of random factors on the basis of eliminating the effect of systematic factors through periodic inspection.

In general, batch-by-batch inspection only examines the key quality characteristics of the product. The periodic inspection should check 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, and even include accelerated aging and life test.

Therefore, the equipment required for periodic inspection is complex, the cycle is long, and the cost is high, but it must not be avoided for periodic inspection. If the enterprise does not have the conditions to conduct periodic inspection, it can entrust inspection agencies at all levels to do periodic inspection on its behalf.

Sort by the effect of the test

1. Deterministic test

Judgmental inspection is a conformity judgment to judge whether a product is qualified or not through inspection based on the quality standards of the product.

2. Informative inspection

Informative inspection is a modern inspection method that uses the information obtained by inspection for quality control.

3, causality test

The causal inspection is to find out the possible causes of unqualified (cause-seeking) through sufficient prediction in the design stage of the product, and design and manufacture error-proof devices in a targeted manner, which is used in the production and manufacturing process of the product to prevent unqualified products. production of goods.

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