Unit 2: Quality Management System (QMS) & Process Quality Improvement

Basics of Quality Management System (QMS)

A Quality Management System (QMS) is a formalized system that documents processes, procedures, and responsibilities for achieving quality policies and objectives. It helps an organization improve its efficiency and satisfy customer requirements.

📌 Key Elements of QMS

ISO 9001:2015

One of the most popular QMS standards. It is based on 7 quality principles:

• Customer focus
• Leadership
• Engagement of people
• Process approach
• Improvement
• Evidence-based decision making
• Relationship management

7 QC Tools (Seven Basic Quality Tools)

These tools are used for problem-solving and process improvement.

Regression Control Charts

A regression control chart combines regression analysis with statistical process control (SPC). It is used when two or more variables are related, and you want to monitor the relationship between them over time.

📌 Purpose

• To monitor processes involving multiple variables.
• Detect special causes of variation not explained by the regression model.

📌 Example: Let’s say Output (Y) depends on Input (X). We use regression to establish a relationship:

Y = a + bX

We then monitor the residuals (differences between actual Y and predicted Y) on a control chart.

Summary Table

Process Capability and Analysis

Process capability is a statistical measure of a process's ability to produce output within specified limits (tolerance or specification limits). It tells us how well a process meets customer or design requirements.

📌 Key Terms

 Interpretation of Cpk Values

 Measurement System Analysis (MSA)

Measurement System Analysis evaluates the accuracy and reliability of the measurement system used to collect data. It checks whether the measurement system itself is introducing variation.

📌 Key Concepts

Goal: Ensure the variation in data is from the process, not from measurement tools or methods.

Design and Analysis of Experiment (DOE)

Design of Experiments (DOE) is a statistical method to plan, conduct, analyze, and interpret controlled tests to evaluate the factors that may influence a particular outcome.

📌 Why DOE?

To identify the key input variables (factors) that affect the output (response) and optimize process performance.

📌 Key Elements

 Types of DOE

Summary Table

 Acceptance Sampling Plan

Acceptance sampling is a quality control method where a random sample is taken from a batch (lot) of products to determine whether the entire lot should be accepted or rejected.

It is useful when:

• 100% inspection is too costly or time-consuming.
• Testing is destructive.
• There's a large quantity of products.

📌 Key Terms

Types of Sampling Plans:

Costs Associated with Quality

These are the different costs a company incurs to ensure and improve product quality. These are broadly classified into four types:

Focus: Assurance Cost

Assurance costs include both:

• Prevention Costs: Activities that ensure problems don’t occur
• Appraisal Costs: Activities that detect defects early.

So, Assurance Cost = Prevention Cost + Appraisal Cost

This cost ensures quality is built into the system before the product reaches the customer.

✅ Summary Table

Failure Cost

Failure cost refers to the cost that arises due to defects in products or services. It occurs after a defect has already happened.

Failure costs are divided into two types:

Goal: Minimize failure cost by improving prevention and detection systems.

Prevention Cost

Prevention cost refers to the money spent on avoiding defects from occurring in the first place. These are proactive measures taken during planning and production stages.

Prevention is better (and cheaper) than cure" – this cost helps reduce future failure and appraisal costs.

Rectification Cost

Rectification cost refers to the cost incurred to correct a defective product or service before it is delivered to the customer. It is considered a part of internal failure cost.

These costs don’t add value but are necessary to make the product acceptable before delivery.

Appraisal Cost

Appraisal cost is the cost associated with measuring, testing, and auditing to ensure that products or services meet quality standards.

These activities help in detecting defects before products are sent to customers.

These costs are necessary to maintain confidence in product quality, but they don’t eliminate root causes—that’s what prevention does.

✅ Summary Table

Why Understanding These Costs is Important?

• Helps in cost control and quality improvement.
• Shifts focus from reactive (failure) to proactive (prevention).
• Leads to higher customer satisfaction and lower total cost.