Six Sigma Quality and Defects per Million Opportunities

Six Sigma Quality

• Aims to achieve near quality perfection, with a statistical likelihood of non-defects of 99.99966% of the time.

Defects per Million Opportunities (DPMO)

• A metric used to describe the variability of a process.
• Requires three pieces of data: unit, defect, and opportunity.
• Formula: DPMO = (Number of defects / (Number of opportunities for error per unit × Number of units)) × 1,000,000

Six Sigma Methodology (DMAIC)

• Define: identify customers and their priorities, a project suitable for Six Sigma efforts, and CTQs (critical-to-quality characteristics).
• Measure: determine how to measure the process and how it is performing, and identify the key internal processes that influence CTQs.
• Analyze: determine the most likely causes of defects and identify the key variables.
• Improve: identify means to remove the causes of defects, confirm the key variables, and identify the maximum acceptance ranges of the key variables.
• Control: determine how to maintain the improvements and put tools in place to ensure that the key variables remain within maximum acceptance ranges.

Process Capability Analysis

• A tool for assessing the ability of a process to consistently meet or exceed a product's design specifications.
• Considers the tolerances allowed by product or service design specifications and the natural variability in the process.
• Formula: Cp = Specification width / Process width

Process Capability Analysis Examples

• Example 1: K Computers' medical equipment cart, where piping is cut internally and a scatter diagram shows a positive relationship between conveyor speed and cut length.
• Example 2: Deceptive Cp Value, where the process width and specification width are the same, but the center of the graph is not aligned with the design center, resulting in a Cp value that does not accurately reflect the process capability.

Adjusted Cp Metric (Cpk)

• Used to deal with non-centered process distributions.
• Formula: Cpk = Cp × (1 - K), where K is a correction term.
• Cpk is less than 1, indicating an unreliable process that cannot reliably meet design specifications.

Cpk, PPM, and Process Management

• Cpk values and their corresponding process implications:
  • 0.50: Process is incapable, 100% inspection may be needed.
  • 1.00: Process capable, normal sampling would be typical.
  • 1.33: Process capable, normal sampling would be typical.
  • 1.50: Process capable, no inspection may be needed.
  • 2.00: Process is very stable, no inspection may be needed.

Process Control Analysis

• Process Control Charts (SPC) are used to monitor process output to detect changes.
• Intelligent systems plot and compare outputs to a set of limits for the upper and lower boundaries of the process width.
• Process control charts identify when a process has deviated from its normal operation.

Process Control Charts (Xbar&R)

• An example of Xbar & R: tracking hard disk seek times to ensure the process of building the disks is under control.
• Steps to create an Xbar & R chart:
  1. Collect data samples.
  2. Calculate the sample mean (x) for each sample.
  3. Calculate the range (R) for each sample.
  4. Calculate the grand mean.
  5. Calculate the mean range.

Quality Definitions

• Product quality is a product's fitness for consumption, which is determined by both design quality and conformance quality.
• Design quality measures how well a product's designed features match up to the requirements of a given customer group.
• Conformance quality measures whether a delivered product meets its design specifications.

Dimensions of Quality

• Performance: the degree to which a product meets or exceeds certain operating characteristics.
• Features: presence of unique product characteristics that supplement basic functions.
• Reliability: length of time a product performs before it must be repaired.
• Durability: length of product life or the amount of use one gets before a product deteriorates.
• Conformance: the degree to which a product meets its design specifications.
• Aesthetics: subjective assessment of a product's look, feel, sound, taste, or smell.
• Support/Responsiveness: competence of product support in terms of installation, information, maintenance, or repair.
• Perceived Quality (Reputation/Assurance/Empathy): subjective assessment based on image, advertising, brand names, reputation, or other information indirectly associated with the product's attributes.

Total Quality Management (TQM)

• An integrated strategy aimed at embedding awareness of quality, aiming for near quality perfection (the statistical likelihood of non-defects: 99.99966% of the time).

Six Sigma Quality

• Defects per Million Opportunities (DPMO): a metric used to describe the variability of the process, requiring three pieces of data: unit, defect, and opportunity.
• Six Sigma Methodology (DMAIC):
  • Define: identify customers and their priorities, a project suitable for Six Sigma efforts, and critical-to-quality characteristics.
  • Measure: determine how to measure the process and how it is performing, and identify the key internal processes that influence critical-to-quality characteristics.
  • Analyze: determine the most likely causes of defects and identify the key variables.
  • Improve: identify means to remove the causes of defects, confirm the key variables, and identify the maximum acceptance ranges of the key variables.
  • Control: determine how to maintain the improvements and put tools in place to ensure that the key variables remain within maximum acceptance ranges.

Process Capability Analysis

• A tool for assessing the ability of a process to consistently meet or exceed a product's design specifications, considering tolerances allowed by product or service design specifications and the natural variability in the process.
• Cp = Specification width / Process width, where Cp is a measure of process capability.

Process Control Analysis (p Chart)

• A chart that plots the proportion of defectives in each sample, with the proportion of defectives (p) on the vertical axis and the sample number on the horizontal axis.
• The graph has the upper limit at 0.09 and the lower limit at 0.00, and p-bar at 0.0335.
• Interpreting Control Charts:
  • Trends: successive points seem to fall along a line moving upward or downward.
  • Runs: run of points that indicate systemic changes in process.
  • Hugging: points appear so closely grouped that they seem to show no variation.
  • Periodicity: plotted points show the same pattern of change over equal intervals.

Quality Management

• Hyundai's brand turnaround involved increasing the quality control team from 100 to 850 workers, instituting mandatory seminars, and involving the CEO in quality comparisons with rivals.
• Hyundai invested $30 million in a computer center to test electronic systems and made capital investments in problem areas.

Brand Turnaround at Hyundai - Results of Changes

• Hyundai's brand loyalty surpassed that of Honda and Toyota, with five Hyundai cars among the "Best Bets" for safety, reliability, and fuel efficiency.
• Genesis models made Hyundai a strong competitor in the luxury market, where excellent quality is imperative.
• In 2014, Hyundai placed first in the J.D. Power Initial Quality Study, with an average of 90 problems per 100 vehicles, 20% fewer problems than those found in European, Japanese, and American cars.

Six Sigma Quality

• Defects per Million Opportunities (DPMO) is a metric used to describe the variability of a process.
• DPMO requires three pieces of data: unit, defect, and opportunity.
• The formula for DPMO is: Number of defects / (Number of opportunities for error per unit × Number of units) × 1,000,000

Six Sigma Methodology (DMAIC)

• Define: identify customers and their priorities, a project suitable for Six Sigma efforts, and CTQs (critical-to-quality characteristics).
• Measure: determine how to measure the process and how it is performing, and identify the key internal processes that influence CTQs.
• Analyze: determine the most likely causes of defects and identify the key variables.
• Improve: identify means to remove the causes of defects, confirm the key variables, and identify the maximum acceptance ranges of the key variables.
• Control: determine how to maintain the improvements and put tools in place to ensure that the key variables remain within maximum acceptance ranges.

Process Capability Analysis

• Process capability analysis is a tool for assessing the ability of a process to consistently meet or exceed a product's design specifications.
• Specification width (S) is the design specification for a product.
• Process width (P) is the actual range of outcomes generated by the production process.
• Cp is the ratio of the specification width to the process width.
• Cp = USL - LSL / 6σ ( Upper Specification Limit - Lower Specification Limit / 6 standard deviations)

Process Control Analysis

• Process control charts or statistical process control (SPC) are tools used to monitor process output to detect changes.
• Intelligent systems plot and compare outputs to a set of limits for the upper and lower boundaries of the process width.
• Process control charts identify when a process has deviated from its normal operation (when it is "out of control").
• Xbar & R is an example of process control analysis, where sample means and ranges are used to track the process.

Xbar & R

• Xbar & R is used to track the process of building hard disks and ensure that the seek times are under control.
• The process involves collecting data samples, calculating the sample mean and range, and calculating the grand mean and mean range.