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Chapter 10. Lean Systems and Six-Sigma Quality. Lecture Outline. What is Lean? Lean Production Respect for People Total Quality Management (TQM) Statistical Quality Control (SQC) Six-Sigma Quality Lean Six-Sigma Supply Chain. What is Lean?.
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Chapter 10 Lean Systems and Six-Sigma Quality
Lecture Outline • What is Lean? • Lean Production • Respect for People • Total Quality Management (TQM) • Statistical Quality Control (SQC) • Six-Sigma Quality • Lean Six-Sigma Supply Chain
What is Lean? Lean is a management approach for creating value for the end customer through the most efficient utilization resources possible • Standard in many industries • Often results in: • large cost reductions • improved quality • increased customer service
Lean Six Sigma Combines the approaches of Lean and Six Sigma • Six Sigma • methodology to identify and eliminate causes of quality problems
Tenets of Lean There are six tenets of the Lean Philosophy: • Elimination of Waste • eliminate all non-value adding activities • A Broad View • decisions made for the success of the entire supply chain • all supply chain members responsible for adding value • Simplicity • the simpler the solution the better
Tenets of Lean Continued • Continuous Improvement • emphasis on quality and continuous improvement • called kaizen • Visibility • visible problems are identified and solved • Flexibility • easily switch from one product type to another, using flexible workers that perform many different tasks
Elements of Lean Lean is composed of three elements that work in unison: • Lean Production • Total Quality Management (TQM) • Respect for People
Lean Production Coordinated system for producing the exact products desired, delivered in right quantities to where needed Just-in-Time • The Pull System • Visual Signals • Small Lot Production • Uniform Plant Loading
The Pull System • Traditional approach • supply chains work as “push” systems • inventory carried to cover up problems • Pull approach • each stage in supply chain requests quantities needed from the previous stage • no excess inventory generated • reduced inventory exposes problems
Visual Signals Communication between workstations • Kanban • “signal” or “card” in Japanese • contains information passed between stations • authorizes production
Small Lot Production The amount of products produced at any one time is small • reduces inventory and excess processing • increases flexibility • shortens manufacturing lead time • responds to customer demands more quickly • setup time must be low
Uniform Plant Loading • Problem • demand changes are magnified throughout the supply chain • contributes to inefficiency and waste • Uniform Plant Loading • production schedule is frozen for the month • also called “leveling” • helps suppliers better plan own production
Respect for People Respect for all people must exist for an organization to be its best • flatter hierarchy than traditional organizations • ordinary workers given great responsibility • supply chain members work together in cross functional teams • Look at Role of: • workers, management, and suppliers
Role of Workers Workers have the ability to perform many different tasks and are actively engaged in pursuing company goals • Worker Duties • improve production process • monitor quality • correct quality problems • Work in Teams • quality circles
Role of Management Create the cultural change in the organization needed for Lean to succeed • provide atmosphere of cooperation • Empower workers to take action based on their ideas • develop incentive system for lean behaviors
Role of Suppliers Lean builds long-term supplier relationships • companies partner with suppliers • improve process quality • information sharing • goal to have single-source suppliers
Total Quality Management (TQM) TQM is an integrated organizational effort designed to improve quality at every level Look at: • Quality Gurus • Voice of the Customer • Costs of Quality • Quality Tools • ISO 9000
Voice of the Customer Quality is defined as meeting or exceeding customer expectations • Determine customer wants: • focus groups • market surveys • customer interviews
Quality Tools Lean requires workers to identify and correct quality problems • Seven Tools of Quality Control: • Cause and Effect Diagrams • Flowcharts • Checklists • Control Charts • Scatter Diagrams • Pareto Analysis • Histograms
Cause and Effect Diagrams Identify causes of a quality problem • sometimes called “fishbone diagrams”
Flowchart Diagrams the sequence of steps in an operation or process
Checklist Lists common defects and number of occurrences of the defects
Control Chart Determines whether a process is operating within expectations
Scatter Diagram Graph that visually shows how two variables are related to one another
Pareto Analysis Based on the premise that a small number of causes create the majority of problems • identifies problems based on degree of importance
Histogram Chart that shows the frequency distribution of observed values of a variable
ISO 9000 “Family” of standards for quality management • increased international trade developed a need • published by International Organization for Standards (ISO) in 1987 • concerns measuring and documenting the quality process • ISO provides a certification process • ISO 14000 • standards for environmental management
Statistical Quality Control (SQC) SQC is the use of statistical tools to measure product and process quality Three categories: • Descriptive Statistics • describe quality characteristics • Statistical Process Control (SPC) • a random sample of output is used to determine if characteristics are acceptable • Acceptance Sampling • sample determines if whole batch is acceptable
Sources of Variation All processes have variation • Assignable Variation • caused by factors that can be clearly identified and managed • Common Variation • inherent in the process • also called random variation
Process Capability Process Capability evaluates the variation of the process relative to product specifications • Product Specifications • ranges of acceptable quality characteristics • also called tolerances • Process Variation • all processes have natural variation • defects are produced when variation exceeds product specifications
Process Capability Index where: USL = upper specification limit LSL = lower specification limit • CpValues: • Cp = 1: process is minimally capable • Cp ≤ 1: process is not capable of producing products within specification • Cp ≥ 1: process exceeds minimum capability
Cp Example Given a process with three separate machines that are used to fill jars with pasta sauce. • specification range is between 30 and 34 ounces • process mean, μ, is 31 ounces Calculate the Cp for each machine to determine capabilities
Cp Example Continued • A: • B: • C: Machine A has a Cp > 1, however the process mean is not centered
Cpk Example Cpk addresses the lack of centering of the process over the specification range • Machine A: Cpk = min (1.66, 0.55) = 0.55
Process Control Charts Graph that shows whether a sample of data falls within the common range of variation • sample process output • plot result on the control chart • use to determine if process is in control • can monitor: • variables • characteristics that can be measured • attributes • characteristics that can be counted
Control Charts for Attributes A p-chart monitors the proportion of defective items in a sample • centerline: average value of p across all samples, p • UCL = p + z sp • LCL = p – z sp where: z = standard normal variable p = sample proportion defective sp = = standard deviation of avg. proportion defective
P-Chart Example Given the following five samples of data tracking incorrect procedures in a hospital
P-Chart Example Continued p = 5/10 = 0.10 UCL = p + z sp = 0.10 + 3(0.095) = 0.385 LCL = p + z sp = 0.10 - 3(0.095) = 0.185