Inspection in China. Piece By Piece Inspection or Partial Inspection?

In today’s industry, manufacturers select materials and suppliers from around the world to meet market demands. Importing from China suppliers is a cost-effective approach. However, there is an increased risk that the quality of products and materials might not meet agreed standards and specifications.

Inspection is a service related to ensuring the quality of goods. There are two main types of inspection in China: piece-by-piece and partial. Piece By Piece inspection checks each product before shipment, while partial inspection only selects specific samples for inspection. You can consider which method to go for based on the batch’s quantity, budget, type of product, and time available.

This article will explain the difference between these two inspection methods. By the end of this article, you will know their pros and cons, inspection processes, and what you should choose. Let’s get started.

What is Piece by Piece Inspection?

Piece-by-piece inspection is known as 100% inspection, simply put, it inspects every product one by one before shipment.

After picking out the unqualified products, the rest are all qualified products. Although this quality inspection method is suitable for large-size products with small production quantities, it is not ideal for most products with large production batches, such as electronic components.

When there are many inspection items or the process is complicated, full inspections will cost a lot of workforce and material resources. When the quality inspection is destructive, such as the life test of TV sets, the strength test of material products, etc., 100% inspections are impossible.

You can do a piece by piece inspection before and after packaging, whether at your place, your suppliers’ place, or the China warehouse before shipment.

By this approach, buyers ensure their products meet the quality to avoid complaints of malfunction. Some online marketplaces require inspection before shipping out, such as Amazon FBA products that often requires full inspection service.

What is Partial Inspection?

Partial inspection randomly selects an appropriate amount of product samples for quality inspection from a batch of products. It uses judgment standards to determine whether the product is qualified or needs to be subject to another inspection. Thus, it is also called a random inspection or sampling inspection.

The quality can be assured if the inspector can adequately inspect each product. However, if the nature inspection is destructive, it is impossible to carry out piece by piece inspections as the cost is very high. You will need to consider a partial inspection.

Although partial inspection cannot guarantee the quality of each product, it can ensure the quality of each batch under a certain “probability.” It is advantageous from an economic point of view because it can save inspection costs. Therefore, you can apply partial inspection to many situations.

Acceptance Quality Limit (AQL)

AQL is also referred to as “acceptance sampling.” It is a statistical measurement of the maximum acceptable number of defective goods in a particular sample size.

The quality characteristics of a product randomly selected from a batch of products are compared with the pre-specified quality limits to decide whether to accept or reject the product batch.

Some simulators are online to determine the correct sample size and acceptance number to best suit your needs. The result, illustrated as the number, will be your AQL figure. For example, AQL 3.0 determines the acceptable level of defective products is 3.0% of the total quantity.

Pros and Cons: Piece by Piece Inspection and Partial Inspection

1） Advantages of the piece-by-piece inspection:

• Every product is checked before shipment.
• Provide complete product inspection data
• More sufficient and reliable quality information

2）Disadvantages of the piece-by-piece inspection:

• Consume a lot of human and material resources
• High inspection cost
• The inspection timeline is extended

3）Advantages of the partial inspection:

• Save the inspection cost.
• Suitable for destructive testing
• Fewer inspectors are required.
• Since the whole batch of products is rejected instead of just returning substandard products, it can more effectively promote product improvement.

4）Disadvantages of the partial inspection:

• There is a risk of accepting “inferior” batches and rejecting “high-quality” batches;
• The product information provided by the sample is generally less than that of the complete inspection.

The Inspection Process

Both types of inspection share a similar inspection process. Let’s dive deep.

1.   Preparation for Inspection

Preparation includes familiarity with the requirements, inspection methods, and inspection specifications.

You shall stipulate the determined inspection methods and plans in the form of technical documents, inspection procedures, and instructions.

In the preparation stage of the inspection, the inspection personnel should be trained and assessed on the relevant knowledge and skills to confirm whether they can meet the requirement.

2.   Start Measurement and Inspection

Quantitative observation, measurement, and product quality testing are carried out according to the established inspection methods. Before and after inspection, the inspector should confirm that the equipment and the inspected item are in normal condition to ensure correctness and validity.

What to Inspect?

The range is vast, and the inspection might vary based on the product types. In standard practice, the inspection covers the following:

• Product Safety
• Quantity
• Function
• Color
• Size
• Appearance
• Packing

3.   Record Result

The measurement conditions, the measured values​​, and the observed result are recorded. The quality inspection record is the evidence to confirm the quality of the product. Therefore, the data must be objective and accurate, and any changes that need to be made must be handled following the prescribed procedures and requirements.

The quality inspection record should record inspection data, date, and shift. Ensure the inspector signs it to facilitate traceability and clarify responsibility.

However, humans are the ones who do the inspection. So, there might be human-made errors or inaccuracies in product quality assurance. Here are the factors that might cause the errors:

Factors that affect errors in the piece-by-piece inspection:

• The size of the product batch;
• The level of unqualified product rate;
• To examine the nature of the work;
• How to use the inspection tools;
• The inspectors’ technical level and sense of responsibility

Decision Making: Piece by Piece Inspection or Partial Inspection?

After reviewing the pros and cons of both inspection methods, you might think, which should I choose? You may refer to the below in making your decision:

Our suggestion is to choose piece by piece inspection if:

• The number of inspections is small.
• Low inspection cost
• You have more margin in inspections.
• Newly introduced products that are not stable enough in manufacturing
• Expensive, high-precision, or heavy-duty products
• Products and components with special requirements
• Products and components that can apply automated inspection methods

In contrast, you may choose partial inspection if:

• Destructive tests are required for product performance inspection
• The batch is too large to be fully inspected
• Longer inspection time and higher inspection costs are required
• Allow a certain degree of defective products to exist

In summary, below are the factors to choosing either piece by piece inspection or partial inspection is suitable for you:

a. Quantity

The price between the two types of inspections is comparable if you have a lower quantity of goods. You may go for a partial inspection for a lower price or a piece by piece inspection for more guaranteed quality assurance. However, random inspection will be more cost-effective if you have bulk products pending to inspect.

b. Type of Product

A 100% inspection is a safe way to ensure quality for high-value or high-risk products. As the customers are paying higher for the products, the inspection should be gone thoroughly. However, random inspections are good enough for daily usage products with lower prices for quality assurance.

c. Available Time

Piece by piece inspections take longer time to conduct than partial inspections. If you are rushing the timeline, the partial inspection may be the way to go for an effective inspection process. Thus, you will need to allocate an inspection period in the production schedule.

Final Words

Inspection is the product quality control process before shipment. China suppliers do inspections during production, but it is better to do another inspection before shipment to achieve better customer satisfaction.

Both piece by piece inspection and partial inspections are practical ways to ensure product quality. To ensure every product meets the same quality, check on your inspection timeline and cost to allocate for a piece by piece inspection. In comparison, partial inspection is a practical and cost-effective choice.

We are a team of inspection professionals in China, providing quality inspection services to our clients worldwide. We monitor the production down the supply chain, from product development, sourcing, and quality control, to shipping and delivery. Talk to us today about more business solutions!

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Author: AQI Service as a professional quality control service company in China specialized in providing a complete range of quality inspection and testing and certification services in China & Asia for global importers, buyers, retailers, and sellers.