AQL Sampling in the Philippines: How ISO 2859 Testing Reduces Defects in Manufacturing

Why AQL Sampling Is Widely Used

• It is cost-effective
• It is statistically reliable
• It is internationally recognized
• It provides objective pass/fail results
• It reduces inspection time without compromising quality

In the Philippines, AQL sampling is commonly used during pre-shipment inspections, during production checks, and final random inspections.

Key Features of ISO 2859

• Standardized sampling tables
• Defined inspection levels
• Clear acceptance and rejection criteria
• Defect classification system
• Consistent methodology across industries

By using ISO 2859, buyers sourcing from the Philippines ensure inspections are fair, repeatable, and aligned with global quality expectations.

Common Manufacturing Challenges Addressed by AQL

• Batch-to-batch quality variation
• Inconsistent workmanship
• Manual assembly errors
• Packaging and labeling mistakes
• Supplier interpretation differences

By applying ISO 2859 sampling, these issues can be detected early and managed before shipment.

Step 1: Define the Lot Size

The lot size refers to the total number of units in the production batch or shipment. This could be the total quantity in one purchase order, container, or shipment.

The lot size determines how many samples will be selected for inspection.

Step 2: Select the Inspection Level

ISO 2859 defines several inspection levels, which control sample size.

• General Inspection Level I (less strict)
• General Inspection Level II (most commonly used)
• General Inspection Level III (more strict)
• Special inspection levels (S1–S4)

In the Philippines, General Inspection Level II is the default for most pre-shipment inspections unless otherwise specified by the buyer.

Step 3: Determine Sample Size

Using ISO 2859 sampling tables, inspectors determine the sample size based on the lot size and inspection level.

For example:

• A lot of 5,000 units may require a sample of 200 units
• A lot of 10,000 units may require a sample of 315 units

This ensures the sample is statistically representative of the entire batch.

Step 4: Classify Defects

Defects are classified into three categories:

Step 5: Apply AQL Limits

Each defect category has its own AQL value. Common AQL settings used in the Philippines include:

• Critical: 0.0
• Major: 2.5
• Minor: 4.0

Inspectors compare the number of defects found in the sample against ISO 2859 acceptance and rejection limits.

If defect counts exceed the allowed limit, the shipment fails inspection.

Encourages Supplier Accountability

When suppliers know inspections are based on ISO 2859 standards, they are more likely to maintain consistent quality throughout production. Repeated inspection failures create pressure to improve internal processes.

Detects Systemic Issues Early

Patterns in inspection results often reveal deeper production problems, such as:

• Poor training
• Inadequate quality controls
• Equipment calibration issues
• Weak packaging procedures

Early detection allows corrective action before defects multiply.

Reduces Costly Rework and Returns

Finding defects before shipment is far less expensive than dealing with returns, recalls, or customer complaints in destination markets.

AQL sampling helps stop defective goods before they leave the factory.

Balances Quality and Efficiency

100% inspection is rarely practical for large-scale manufacturing. AQL sampling provides a scientifically balanced approach that controls risk without slowing production or increasing costs excessively.

AQL Does Not Guarantee Zero Defects

AQL is a risk-based system. It reduces the probability of defects but does not eliminate them.

Not Suitable for High-Risk Products Alone

For products with strict safety or regulatory requirements, AQL sampling should be combined with:

• Laboratory testing
• Certification verification
• Process audits

Requires Proper Implementation

Incorrect sampling methods, biased selection, or misclassification of defects can compromise inspection accuracy. This is why experienced inspectors are essential.

Use the Correct Inspection Level

Always define the inspection level before production or inspection begins. General Inspection Level II is the most commonly used and provides a good balance between risk and cost. Higher inspection levels may be required for complex or high-risk products.

Set Clear AQL Limits

Clearly agree on AQL limits for critical, major, and minor defects with your supplier. Common limits are 0 for critical defects, 2.5 for major defects, and 4.0 for minor defects. These limits should be stated in purchase orders or quality agreements.

Define Defects Clearly

Defect definitions must be clear and measurable. Vague descriptions lead to inconsistent inspection results and disputes. Use photos, samples, or written criteria to define what counts as critical, major, and minor defects.

Ensure Random Sampling

Samples must be selected randomly across the entire batch. Avoid allowing suppliers to choose samples. Random selection ensures the inspection reflects actual production quality and prevents biased results.

Combine AQL with Other Quality Checks

AQL sampling works best when combined with other quality control activities, such as during-production inspections, factory audits, and laboratory testing. This layered approach reduces risk more effectively than relying on final inspection alone.

Inspect at the Right Time

Conduct AQL inspections only when production is complete and goods are packed. Inspecting too early may result in unrepresentative samples and unreliable results.

Work with Experienced Inspectors

Accurate AQL sampling depends on inspector expertise. Inspectors must understand ISO 2859 tables, defect classification, and product-specific requirements. Experienced inspectors reduce errors and improve report reliability.

Use Inspection Results to Drive Improvement

Inspection results should not be treated as one-time pass or fail outcomes. Track defect trends across shipments and use the data to address root causes with suppliers. This leads to continuous quality improvement.