Quality Control:Definition, Significance, and Methods

1. Establishing Standards

First, clear and measurable quality standards are set for the product or service. These standards may be based on industry norms, customer expectations, or internal company goals, forming the foundation for the QC process.

2. Inspection and Testing

Throughout and after production, products undergo regular inspections and tests. These may include visual inspections, functional tests, and specific measurements to verify that each item meets the established quality criteria.

3. Sampling

Rather than inspecting every unit, random samples from production batches are selected for testing. This helps detect defects or inconsistencies in the products, allowing QC to efficiently monitor quality without testing each individual item.

4. Defect Identification

Any flaws or defects found during inspections are identified and documented. These defects could range from faulty designs to issues with materials or workmanship. This step ensures that every problem is tracked for future improvements.

5. Corrective Actions

When defects are identified, corrective actions are immediately implemented to address the issues. This may include adjusting the production process, retraining staff, or repairing equipment to eliminate the root cause of the defect.

6. Documentation and Reporting

QC results are thoroughly documented, with reports generated to track performance over time. These reports help identify recurring issues, allowing for targeted interventions to prevent similar problems in future production runs.

7. Final Approval

Before any products are released to the market, they undergo a final review to ensure they meet the required standards. Only products that pass all QC checks are approved for distribution, ensuring that customers receive high-quality, defect-free items.

Inspection

Inspection is the most common QC method. It involves examining products or services visually or through measurements to detect any defects or inconsistencies. Inspections can be done at different stages of production or at the final product.

Statistical Process Control (SPC)

SPC uses statistical techniques to monitor and control a process. It involves collecting data, such as product measurements, and plotting it on control charts to detect variations. If the process goes out of control, corrective action is taken to bring it back to the desired state.

Six Sigma

Six Sigma has been gaining momentum in industry. This method focuses on reducing defects to fewer than 3.4 per million opportunities. Six Sigma uses a data-driven approach to identify and eliminate causes of defects, aiming for near-perfect production.

In article The Evolution of Six Sigma , Six Sigma has four stages:

• Measure
• Analyze
• Improve
• Control

And Industry implements them as:

• Measure: Collect data on current processes to establish a baseline and identify problems.
• Analyze: Use data analysis to identify root causes of defects or inefficiencies in processes.
• Improve: Develop and implement solutions to eliminate causes of defects and optimize processes.
• Control: Implement controls to sustain improvements and monitor the process to ensure consistency.

Total Quality Management (TQM)

TQM is a company-wide approach that focuses on continuous improvement. It involves all employees at every level working together to improve processes, products, and services.

Pareto Analysis

Pareto Analysis identifies the most significant problems in a production process by applying the 80/20 rule. It suggests that 80% of the problems come from 20% of the causes, so businesses should focus on addressing those top 20% to make the biggest impact on quality.

The Pareto diagram is a bar graph, usually with vertical bars, placed from the left to the right by decreasing height. The Pareto graphs are very popular in SQC. The heights of the bars often represent the frequency of the problems in the production process (number of defects, accidents, failures, . . . ). Since the bars are placed by decreasing order of height, it is then easier to identify the areas with the most severe problems.

Control Charts

Control Charts are graphical representations used to monitor the performance of a process over time. Control charts track the variance in a product’s attributes, allowing operators to identify trends and take corrective action if necessary. Key types of control charts used for quality control:

• X-bar Chart (Mean Chart)
• R-chart (Range Chart)
• P-chart (Proportion Chart)
• NP-chart (Number of Defective Items Chart)
• C-chart (Count of Defects Chart)
• U-chart (Defects per Unit Chart)
• Individual/Moving Range (I-MR) Chart

Scatter Diagram

A scatter diagram (or scatter plot) is a graphical representation used in quality control to show the relationship between two variables. Scatter diagrams are commonly used to identify potential causes of defects, variations, or performance issues by visually mapping data points. If a strong correlation is found, it can inform the decision to focus on improving specific aspects of the process or system.

Acceptance Sampling

Acceptance sampling involves testing a random sample of products from a batch to determine if the entire batch meets quality standards. It’s typically used when testing every single product is impractical or too expensive.

Fishbone Diagram (Ishikawa)

Fishbone Diagram (Ishikawa) is a visual tool that helps identify the root causes of problems by categorizing potential causes in a structured way. It’s also known as the "cause and effect" diagram.

FMEA (Failure Mode and Effect Analysis)

FMEA is used to identify potential failure points in a product or process and assess the severity, likelihood, and consequences of each failure. This helps prioritize risks and determine where improvements are necessary.
Must read: FMEA (Failure Mode and Effects Analysis) - A Quick Guide

Taguchi Method

The Taguchi Method of quality control is an approach that prioritizes research, product design, and development in minimizing defects and failures. Traditional methods focus on manufacturing processes, while the Taguchi Method emphasizes the importance of design in ensuring quality. By identifying potential variances early in the product development phase, it seeks to eliminate issues before they arise during production, leading to more consistent and reliable products.

Quality Audits

Regular audits are conducted to assess the effectiveness of the quality control system. Auditors check whether quality standards are being adhered to and recommend areas for improvement.

Qualifications for Quality Control Inspectors

• For entry-level quality control positions, a high school diploma is typically the minimum educational requirement.
• For more senior or specialized quality control positions, a bachelor’s degree may be necessary. Degrees in fields such as engineering, industrial technology, or business management are commonly preferred in industries.
• Industry-specific experience is often highly valued. Certain sectors, such as electronics, aerospace, or automotive manufacturing, may prioritize candidates who have experience in the specific field.

Certifications

Certifications are often required or highly recommended to demonstrate competence in quality control practices and industry standards. Some widely recognized certifications include:

• Certified Quality Inspector (CQI)
• Six Sigma Certification
• ISO 9001

Skills and Traits for Quality Control Professionals

Quality control specialists must possess specific skills and characteristics, including:

• The ability to spot small discrepancies or flaws.
• Knowledge of calculations, mechanics, and measurement tools.
• The ability to perform physical tasks as required by the role.
• Strong problem-solving skills to analyze and resolve issues.
• Ability to perform well under pressure and meet deadlines.

Career Path in Quality Control

The career progression in quality control varies by industry but generally follows a few key steps. Entry-level employees typically start as quality control associates or assistants, learning the skills through hands-on experience and training. As you gain industry knowledge and skills, you can advance to roles such as senior specialist or team leader, overseeing a group of quality control professionals.

To advance further, you may be required to pursue professional certifications like Six Sigma or Certified Quality Inspector. Continuous professional development is essential for career growth in quality control.

Quality Control Salaries

According to the Bureau of Labor Statistics, the average salary for quality control professionals in different industries is:

• Science and Technology: $46,280 per year
• Manufacturing: $40,020 per year
• Wholesale Trade $37,800 per year
• Administrative and Office Support Services: $30,070 per year