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Quality Control Measures Used by Contract Manufacturers

More than 60% of business leaders surveyed said that higher quality is a frequent customer demand. Meeting that demand is essential for your company to thrive.

Global manufacturing is in a period of transition. Economic conditions pose challenges. Opportunities still exist, though.

Many companies are taking advantage of contract manufacturing to lower costs and reduce production time. Quality control measures are an important consideration for supply outsourcing. You need assurance that your manufacturer has tight adherence to standards.

Learn more about what contract manufacturers can do to ensure the quality of your products.

Quality Control, Quality Assurance, and Quality Management

Your contract manufacturer should have a robust quality management plan. Quality management includes quality control and quality assurance.

Quality control helps ensure that products from your contract manufacturer meet your quality standards. It focuses on finding, recording, and categorizing any product flaws.

Quality assurance puts processes in place to meet quality standards and avoid product defects. It’s proactive and preventive. Quality control measures check to be sure that those processes are working as intended.

Quality Management Certification

Your contract manufacturer should have a quality management certification. ISO 9001 is one of the top-quality certifications. It’s an international standard.

Following ISO 9001 gives a manufacturer the foundation for an effective quality management system.

Any organization of any size can use ISO 9001. ISO 9001 involves an auditing process that the manufacturer must repeat every three years. It helps ensure you get consistently high-quality products.

100% Inspection Quality Control Method

As the name suggests, the 100% inspection method examines every item in a production run. This method is very effective. It helps remove almost any product that isn’t exactly in spec.

However, inspecting each item is time-consuming and expensive. This method is only cost-effective when the consequences of a defective product are very serious. It may also be necessary if you are reasonably certain that a batch has flawed items.

Acceptance Sampling Method

Acceptance sampling randomly inspects a certain number of items in the lot. The number of units you need to test depends on the size of the lot. The sample must be large enough to allow an accurate conclusion.

If the number of flawed products in the sample is low, you accept the lot. If the number of flaws is too high, you reject the lot.

Acceptance sampling relies on statistical inference. This makes it less accurate than the 100% inspection method. It tells you whether a lot is likely to be acceptable, not the quality of the lot.

However, acceptance sampling is faster and less expensive than 100% inspection. It’s also a good option if testing destroys the product.

Statistical Quality Control (SQC)

Statistical quality control goes beyond acceptance sampling. It uses sampling inspections, data analysis, and control charting. The quality control tools include:

  • Check sheet
  • Histogram
  • Pareto chart
  • Control chart
  • Cause-and-effect diagram
  • Scatter diagram
  • Stratification

A manufacturer may use some or all of these statistical techniques.

Check Sheets

Check sheets help the manufacturer gather data. They help ensure that data collection is effective and efficient.


A histogram is a bar chart. It represents the frequency distribution of data. It helps the manufacturer understand where and when a product’s characteristic varies.

Pareto Charts

A Pareto chart is a combination of a bar chart and a line graph. It highlights the relative importance of different production parameters. This helps the manufacturer focus on the factors that will resolve the most problems.

Control Charts

A control chart documents when unusual process variations occur. It helps the manufacturer determine whether specific factors are affecting the current process. It helps to predict process performance.

Cause-and-Effect Diagrams

A cause-and-effect diagram helps the manufacturer identify the causes of a problem. These diagrams are also called fishbone diagrams because of how they look. The diagram has a quality-related problem on one side and root causes and sub-causes on the other side.

The technique uses structured brainstorming to try to find less-obvious causes for the problem. 

Scatter Diagrams

A scatter diagram represents the relationship between two variables. It’s another way to identify cause-and-effect relationships.

However, a scatter diagram doesn’t prove causality. The manufacturer needs to conduct an experiment to determine if a potential factor is the cause of the problem. They can then implement a more focused solution for the problem.


Stratification is used with other data analysis techniques. It separates data, objects, and people into different groups. It helps reveal patterns that might not be visible otherwise.

Six Sigma and Lean Six Sigma

Six Sigma is a methodology for quality management. The goal is to reduce defects and errors by minimizing variance in the manufacturing process. Six Sigma uses a process of steps called DMAIC:

  • Define the problem
  • Measure current performance
  • Analyze the process
  • Improve the process by eliminating the causes of any problems
  • Control the process to ensure problems don’t reoccur

This approach is data-driven. It goes beyond basic quality control to optimize total business processes.

Lean Six Sigma

Lean Six Sigma combines Six Sigma with the lean manufacturing method. Lean manufacturing focuses on minimizing production waste and maximizing efficiency. In addition to reducing defects, it aims to minimize:

  • Overproduction
  • Wait time
  • Non-utilized talent
  • Inefficient transportation
  • Excess inventory
  • Unnecessary movements
  • Excessive processing

Lean Six Sigma is a comprehensive approach to process management.

The Importance of Quality Control Measures in Contract Manufacturing

Robust quality control measures are essential for a contract manufacturer.

Quality control helps you better manage costs. It results in lower scrap levels. Labor costs are lower through less handling and rework.

Minimizing defective products protects your brand. You improve customer loyalty. You protect yourself from liability.

Your contract with the manufacturer should define the manufacturing standards for your product. It should outline their specific quality control processes to meet those requirements.

Finding a Contract Manufacturer with the Right Quality Control Measures

A variety of quality control measures can help your contract manufacturer meet your production standards. Finding a manufacturer who has the right measures in place is the key.

Shield Works Precision Manufacturing is reinventing contract manufacturing. Our British-owned and managed facilities are located in the rapidly developing South China Greater Bay Area.

We hold ISO 9001 certification. You can rely on our adherence to standards and transparency. You benefit from our competitive cost structure and international experience.

Contact Shield Works today to discuss your manufacturing needs. We look forward to exceeding your expectations.