Every manufacturing business has a vested interest in maintaining the highest possible quality control for its customers. However, that can be especially challenging for service providers of low-volume prototypes or custom parts because they deal with a constantly changing array of designs, materials, and processes.
The good news is that there are some fundamental best practices for applying quality control for manufacturing that smart managers and business owners need to consider, regardless of the type of products being made or the industries being served.
We want to take a closer look at how quality control in production is defined and implemented in a factory environment and what the benefits are for both the supplier and the end user.
What is Quality Control in Manufacturing?
Quality control in production is the method for monitoring and controlling all the process steps used to transform raw material into a finished product. Although the specific applications will differ slightly, most QC programs will control one or more of the following common characteristics:
- Surface textures and roughness
- Physical dimensions and tolerances
- Visual appearance
- Engineering properties
- Material properties
It’s important to note, however, that quality control by itself doesn’t determine how fit the product is for an intended application – that’s entirely up to the product designer. In fact, contract manufacturers, the people making the parts to order, often don’t know what the component is for. They’re simply responsible for making it to the client’s specifications.
Whatās the Difference Between Quality Assurance and Quality Control?
Quality assurance is not the same as quality control, and itās important to understand the distinction between the two related terms.
Quality assurance in manufacturing is process-oriented and focuses on best practices to avoid defects. It refers to proactive measures meant to achieve optimal, measurable performance.
Quality control, on the other hand, is primarily reactionary and takes place during inspection. The goal is to identify any defective products and remove or re-work them before they can be shipped to the customer.
Both quality assurance and quality control are important components of any good factory quality control system.
What is a Quality Management System?
Quality management systems tie together multiple departments and technical experts to ensure the performance of every manufacturing process. Depending on a company’s structure, quality systems may involve input from supply chain managers, purchasers, material inspectors, machine operators, management executives, and quality control specialists.
This interdisciplinary team creates standardized best practices to be followed throughout the organization.
What are the Quality Control Procedures for Manufacturing?
Manufacturing quality control means more than just inspecting a semi-finished product as it moves through the factory. To be effective, the results of these inspections are then fed back into the manufacturing processes to help further refine them. Quality control feedback is essential to identify non-conformances and establish a benchmark for performance that a manufacturer should always try to surpass.
Here are the key features that every manufacturing quality control program should have.
Document Control
Document control ensures accountability and traceability, which makes it one of the most essential quality control procedures for manufacturing. Suppose a product fails in the field due to non-conforming raw materials. In that case, you’d need to trace the material back to the original supplier to see what verification tests were performed. A transparent document control procedure makes this possible while helping the manufacturer implement immediate corrective actions where and when necessary.
In-Process Inspection
Semi-finished goods are evaluated in process for conformance to the customer’s specifications. Depending on the complexity of the design and the number of processing steps involved, there may be many of these checks along the way.
In-process inspections help manufacturers verify that their factory quality control and production methods are working properly and are yielding predictable results. They also help to spot defects before additional time and energy is wasted upon what will ultimately become a reject.
Equipment Control
Production equipment inspections collect relevant data about machine performance, which then becomes part of the overall document control system. Factory equipment should be subject to regular equipment quality control checks during manufacturing so that potentially faulty products can be traced back to the machine(s) used to process them, and the manufacturer can identify the root cause.
Material Inspection
Positive material identification, or PMI, is used to verify all manufacturing materials before they’re put into production. This methodology employs scientific testing equipment to confirm their exact physical and chemical composition.
Without these tests, a manufacturer is forced to rely on labels and documentation from the material supplier, which may prove unreliable. More importantly, PMI identifies fake, non-conforming, or illegally sourced materials that can expose manufacturers to serious legal jeopardy if they aren’t purged from the supply chain.
Quality Sampling
Random sampling is one of the important quality control procedures for manufacturing. This step can reveal when a process has gone out of control and is routinely making parts out of tolerance. If this occurs, the process must be stopped, and the root cause must be determined before production can restart. It’s also necessary to perform a 100% inspection of all semi-finished goods that might have been affected by the out-of-control condition.
Why Does Quality Control in Manufacturing Matter?
Good manufacturing quality control directly and indirectly supports:
- Brand Reputation: Consistently high standards increase the likelihood of repeat customers and also enhance a brandās reputation through word-of-mouth marketing. A reputation for excellence has long-term benefits for customer retention and attracting new business.
- Competitive Advantage: Businesses without oversight run the risk of being replaced by competitors.
- Cost Reduction: Poor quality is expensive. It wastes raw materials, energy, labor, and time. Therefore, improving product quality – even if it means investing in better equipment – ultimately yields cost savings.
- Preventing Defects: Defects often result in serious and costly consequences. Manufacturers should constantly aim to eliminate these issues completely through closely monitored and analyzed processes on an ongoing basis.
- Product Consistency: Consistency is key to building trust, thus upholding customer satisfaction and cultivating a lasting positive reputation. Consistent production of high-value products tends to promote success.
- Regulatory Compliance: Standards are set externally by regulatory bodies and internally by organizations. Both serve as a testament to the company’s commitment to factory quality control. Failure to comply can result in expensive legal complications and delays that harm the brand.
- Risk Mitigation: By evaluating processes to identify and address all potential risks, companies ensure the delivery of top-quality productsāa critical asset for any manufacturer who wishes to avoid accidents and errors.
Mastering Manufacturing Quality Control Techniques
Inspection
A complete, 100% inspection of every part would be ideal, and this is usually the case for complex designs or low volumes. However, it’s just not a practical manufacturing quality control technique for large volumes of comparable items coming quickly off a production line.
Instead, manufacturers use periodic inspections at regular intervals, and they may invest in automated equipment, such as high-speed optical scanners, to perform quality checks in manufacturing much faster than the human eye could ever do.
Just in Time (JIT)
The Just In Time (JIT) manufacturing discipline is meant to reduce or eliminate any production delays by having material arrive precisely when it’s needed for production – no sooner and no later. Delays are costly, as is the expense of storing and handling semi-finished goods that take up floor space without providing any value to the customer.
Six Sigma (6Ļ)
Motorola developed one of the early factory quality control methodologies, Six Sigma. It sets targeted goals, like eliminating variance and reducing defects to less than a specific threshold. It’s highly dependent on statistical process control, so manufacturers must constantly acquire and analyze empirical data to limit any deviation in their processes.
Statistical Quality Control
Statistical quality control means using sampling and mathematical probabilities to determine whether the manufacturing processes are under control. These techniques tend to be cheaper and faster than 100% inspection.
Taguchi Method
Originally developed by a Japanese statistician and engineer named Genichi Taguchi, this factory quality control method emphasizes research and development as well as product design. By eliminating production variance, the Taguchi method attempts to lower the rate of failures and defects.
Total Quality Management (TQM)
Total Quality Management, or TQM, aims to improve all stages of production and the work environment that may impact quality. This involves the entire workforce and company culture because it’s important that everyone is enabled and encouraged to report any quality defects they find.
X-Bar Chart
X-bar charts are one visual representation example that clearly shows defect rates and patterns. By using consistent sample sizes over a prolonged period of time, characteristics can be mapped and closely analyzed.
How are Quality Control Measures Implemented in Manufacturing?
Now that we’ve established the importance of a factory quality control system and examined its major components, it’s time to explore how best to apply these tools on the factory floor.
Regulations and Standards
Quality control in manufacturing can only be effective when it’s applied systematically and logically. That’s why one of the best ways to maintain consistency is by aligning with recognized international standards such as ISO.
Remember that ISO standards, for example, don’t control how manufacturers measure their product’s quality. Instead, third-party independent auditors will determine if a supplier is employing best practices consistently according to the discipline recommended by ISO.
Automation
Automated systems are used to augment the work of human inspectors by performing repetitive tasks much more quickly and without the possibility of fatigue, injury, or human error. Automated systems have their limitations, though. First, they can only do exactly as they were programmed, so they must be set up very carefully. They also lack the flexibility needed when facing any unexpected conditions that fall outside their programming. That’s why the factory quality control system must always monitor the automation.
Quality Metrics and KPIs
Key performance indicators (KPIs) quantify and evaluate progress toward achieving production goals, and theyāre crucial for assessing whether operations are on track. Examples of KPIs might be the number of rejects per million pieces or the On-Time Delivery (OTD) percentage.
Statistical Process Control Methods
Initially outlined by Walter A. Shewhart in the early 20th century, statistical process control methods were inspired by Dr. W. Edwards Deming and other early productivity and efficiency researchers.
In manufacturing, this quality control technique applies statistical methods for obtaining real-time data and then representing this data as a plot graph with pre-set control limits to isolate any variation.
Statistical process control methods consider the processes that precede the final product, relying heavily on prevention and early detection.
Supplier Quality Management
Manufacturers are responsible for vetting and managing their supply chain from start to finish, ensuring the quality and quantity of available materials.
Systems to monitor an organizationās supply chain, including supplier quality management (SQM), help keep all processes visible. Using verified suppliers cuts down on the time needed for PMI verification of raw materials and is another way to reduce the possibility of defects.
Team Training
Quality systems are only as good as the people deploying them, so all personnel who perform any tasks that can impact product quality should be trained and tested regularly. In addition, quality control specialists must stay abreast of the latest technological developments and international standards, which are constantly being updated and improved upon.
What are the Best Practices in a Quality Control Program?
When applying these disciplines and tools to a production environment, the best factory quality control practices help ensure not only superior products but also better overall company performance.
Kaizen
Continually introduce process improvements through the Kaizen approach. It highlights commitment and cooperation rather than top-down or radical adjustments. Kaizen values the input of every worker to make small, incremental improvements regularly. Over time, small adjustments to a process, which might seem very minor by themselves, can eventually add up to big gains in quality.
Lean Manufacturing
Multiple quality control methods have converged to form a hybrid system dubbed Lean Six Sigma. It integrates the fundamentals of Six Sigma with lean inventory and enterprise strategies.
Lean manufacturing means reducing waste in every aspect of a production environment while maintaining or even improving lead time and quality. As with Kaizen, minor changes add up to major gains.
Audit and Collect Data
Data collected at many points in the production process yields information not just about the presence of non-conformities but also about their root cause. This data can then be used to implement corrective actions.
Relevant data is essential for documenting that a manufacturer follows their obligations under international law, such as with RoHS certification for goods sold to the EU.
Clean Workspace
Maintaining a clean and orderly workspace doesn’t just look good; it’s also a great way to immediately see when something is out of place. Missing tools, excess or unnecessary materials, or even spilled liquids are all quickly revealed if the workplace is normally neat and tidy. An orderly workplace arrangement also helps to avoid injuries by relieving worker stress and fatigue.
Total Productive Maintenance
Another comprehensive manufacturing quality control methodology is Total Productive Maintenance (TPM).
Founded using lean manufacturing principles with a focus on improving safety, reliability, and productivity, TPM targets waste reduction and defect prevention through proper maintenance of vital equipment.
Key Takeaways on Quality Control in Manufacturing
The first step in effective components manufacturing is to understand the many tools and strategies companies use to establish their production quality control systems. These methods combine testing and measuring equipment, data collection and analysis, and human resource training and skills development to form a comprehensive methodology for monitoring and controlling all value-added steps.
The advantages of manufacturing quality controls when making custom parts extend far beyond merely avoiding product defects. Progressive companies that use these methods also reduce waste, protect workers’ health and safety, and are ultimately more competitive in the marketplace.
If you found this article helpful, we strongly encourage you to explore our other useful resources for even more detailed manufacturing insights on the Star Rapid Blog.
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