Lecture 8 Flashcards
What is the main focus of Quality Control (QC)?
QC focuses on detecting poor quality in manufactured products and taking corrective actions. Traditionally, QC involved manual inspection, but with Industry 4.0, it now includes statistical process control (SPC), cloud-based monitoring, smart manufacturing, and data analytics.
What are the two aspects of Quality Control (QC) in manufacturing?
- Product Features: Characteristics that result from the design of an item, determining its functionality, aesthetics, and appeal to users.
- Freedom from Deficiencies: Ensuring the manufactured product conforms to design specifications and is free of defects or missing components.
What are the two types of variations in manufacturing processes?
- Random Variations: Caused by human precision, material variations, or machine vibrations. They follow a normal distribution and occur when the process is under statistical control.
- Assignable Variations: Abnormal variations due to operator mistakes, defective materials, or machine failures. These cause deviations from normal distribution and signal that the process is out of statistical control.
What is Process Capability (PC), and how is it expressed?
Process Capability (PC) refers to the normal variations inherent in a process when it is in statistical control. It is usually expressed as PC = μ ± 3σ, where μ is the mean and σ is the standard deviation. This means that 99.73% of parts produced will have output values within ±3σ.
What is the Process Capability Index (PCI), and how is it calculated?
The Process Capability Index (PCI) is the ratio of the specified tolerance to the natural tolerance limit (6σ). PCI = T/6σ, where T is the tolerance range (upper limit - lower limit). PCI helps determine if the process is capable of meeting design specifications.
What is Statistical Process Control (SPC)?
SPC is the use of statistical methods to analyze variations in a manufacturing process. It helps determine if a process is stable and whether it meets design specifications. SPC tools include process capability analysis, histograms, and control charts.
What are control charts, and how are they used?
Control charts plot sample values of a process characteristic against upper and lower control limits (UCL and LCL). If a sample value falls outside the control limits, the process is considered out of statistical control, requiring corrective action.
What are the two types of control charts?
- Control Charts for Variables: Measure specific process characteristics (e.g., shaft diameter). These include x̅ charts (mean), R charts (range), and s charts (standard deviation).
- Control Charts for Attributes: Determine if a part is defective (e.g., p chart for fraction defect rate, c chart for number of defects). These charts are based on binomial and Poisson distributions.
What is Total Quality Management (TQM)?
TQM is a management approach that aims to achieve customer satisfaction by involving the entire workforce in quality efforts, from top executives to production workers. It emphasizes continuous improvement of quality and problem-solving by teams of experts.
What is Six Sigma, and how does it differ from TQM?
Six Sigma is a quality program focused on reducing defects by using six standard deviations (rather than the typical three) to measure process variation. Like TQM, it involves the entire workforce and uses SPC, but it specifically quantifies and identifies defect causes.
What are some challenges faced in modern Statistical Process Control (SPC)?
Challenges include early detection and prediction of processes going out of control, handling large amounts of data, real-time analysis, efficient collaboration between teams, automation of quality control, and incorporating new technologies like machine vision.
What are Taguchi methods, and what are the two key concepts?
- Loss Function: The loss due to deviation from a target value increases as the deviation increases, even if the product is within tolerance limits.
- Robust Design: Designing products and processes to be insensitive to variations (noise factors) in manufacturing or environmental conditions.
What is ISO 9000, and how can it be implemented?
ISO 9000 is a family of standards that establish procedures for quality management systems. It can be implemented formally, through registration, which is often required by customers, or informally, to improve product quality and reduce mistakes.
