LESSON 3 Analytical Tools 06January2014

Lesson Objectives Upon completion of this lesson, you should be able to: Identify two methods of statistical sampling Identify quality tools used in a manufacturing context Contrast Process Capability (Cp) and the Process Capability Index (Cpk) as measures of variation Recognize the concepts from the Design of Experiments applied to process improvement

Lesson Topics This lesson will cover the following topics: Statistical Sampling Seven Quality Tools Process Capability Analysis Design of Experiments

What’s In It For Me? Understanding continuous process improvement tools and analysis methods enables you quantitatively monitor your contractors’ manufacturing and supply chain management performance

Introduction How does the use of continuous process improvement tools and analysis methods help you to evaluate and monitor your contractors?

STATISTICAL SAMPLING Lesson Topics: Statistical Sampling Seven Quality Tools Process Capability Analysis Design of Experiments

Acceptance Sampling Testing a sample of products for defects Used to determine whether to accept or reject a production batch Batch is rejected if negative characteristics exceed limits for the batch

Statistical Process Control (SPC) Method to determine if a process is operating within acceptable limits Used in conjunction with process capability analyses and Continuous Process Improvement (CPI) plans

Question and Answer A contractor is testing a sample of fasteners to ensure that the batch conforms to acceptable limits. What quality control method is the contractor practicing? Standard Test Analysis Statistical Process Control Acceptance Sampling Conformance Adaption

Question and Answer Which quality method is used in conjunction with process capability analyses to determine if a process is operating within acceptable limits? Standard Test Analysis Statistical Process Control Acceptance Sampling Conformance Adaption

SEVEN QUALITY TOOLS Lesson Topics: Statistical Sampling Process Capability Analysis Design of Experiments

DoD Implementing CPI Continuous Process Improvement (CPI) tools have been used in industry for decades: Statistical Process Control Total Quality Management Six Sigma Lean DoD Continuous Process Improvement Transformation Guidebook

Seven Quality Tools Flowchart Cause and Effect Diagram Check Sheet Histogram Pareto Chart Run Chart Control Charts

Flowchart Pictorial representation showing all the steps of a process First identify, then analyze the actual process path Each step is evaluated to improve the overall process Other types of process charts: Spaghetti Diagram Swim Lane Chart Supplier-Inputs-Process-Outputs-Customers (SIPOC) Value Stream Map

Flowchart (cont.) Content match order? Goods are received at dock Goods are inspected Content match order? Notify purchasing No Yes Incoming quality check Receiving notifies warehouse = Entrance/exits = Process = Decision = Unknown process

Swim Lane Chart Type of process chart (flowchart) Distinguishes responsibilities for sub-processes of a process Grouped into horizontal or vertical lanes

Cause and Effect Diagram Identifies possible causes of an effect or problem AKA: Ishikawa Diagram or Fishbone Diagram Can be used for brainstorming sessions

Check Sheet Translates “opinions” into “facts” Gather data based on sample observations Detect patterns Defect Types Mon Tues Wed Thu Fri Total Parts rusted 18 Misaligned weld 5 Improper test procedure 1 Wrong part issued 3 Voids in casting 8 Incorrect dimension 12 10 40

Histogram Bar graph that displays frequency distribution Shows how often each different value in a set of data occurs Vertical axis Frequency (counts for each bin) Horizontal axis Response variable

Helps prioritize problems – which to solve first Pareto Chart Special form of vertical bar graph with bars arranged in descending order The left-hand vertical axis shows the impact of each item. In this case, 120 units were thrown away due to mis-aligned stacks. The units in this column can be counts, dollars, or whatever is appropriate. Helps prioritize problems – which to solve first

Also known as “Time Plots” for data taken over a period of time Run Chart Data points plotted on graph in sequence over time Displays trends or shifts in average Also known as “Time Plots” for data taken over a period of time

Control Charts Run chart with statistically determined “upper” and “lower” control limits The plot will help determine if the process is stable (in control) or unpredictable (out of control) Plotting variation allows us to determine how much variability exists in the process Common causes Special causes

Basic Control Chart Structure Measurement Scale Upper Control Limit (UCL) Mean Upper and lower control limits identify any process changes and the existence of variation present due to special causes Lower Control Limit (LCL) Observations from Process

Continuous (Variable) Data Control charts for continuous data: Weight Power Length Tensile strength Temperature, time, etc. Control Charts for continuous data are based on the Normal Distribution The X-Bar Chart and R-Chart are tools used to graphically show these types of data

Discrete (Attribute) Data There are separate control charts for discrete, or “count” type data: Defects per unit Defective solder joints per board Accidents per month Defective pins per connector, etc. Discrete data has less resolution because we are only counting if something specific occurs, not how close we are to a desired condition

Example: Statistical Process Control (SPC)   Approval Time for Documents (Doc) (Days) Week Doc 1 Doc 2 Doc 3 Doc 4 Doc 5 X(bar) R 1 36 33 43 51 39.2 18 2 31 50 54 35 40.6 23 3 41 46 26 37 38.6 20 4 40 56 29 40.4 27 5 34 42 28 32.6 16 6 59 47 65 32 7 52 38 21 8 46.8 9 25 61 47.8 10 48 49 48.2 24 X(dblbar) = 42.56 R(bar) = 24.4

Control Charts for Continuous Data

Question and Answer What quality tool uses pictorial symbols to show all the steps in a process? Flowchart Cause and Effect Diagram Check Sheet Histogram

This graph displays frequency distribution in a bar graph format. Question and Answer This graph displays frequency distribution in a bar graph format. Control Chart Cause and Effect Diagram Check Sheet Histogram

Question and Answer This quality tool is also called a Fishbone Diagram and is used for brainstorming sessions to sort ideas into useful categories. Control Chart Cause and Effect Diagram Pareto Chart Swim Lane

PROCESS CAPABILITY ANALYSIS Lesson Topics: Statistical Sampling Seven Quality Tools Process Capability Analysis Design of Experiments

Variation: Common & Special Causes If only common causes of variation are present, the output of a process forms a distribution that is stable over time and is predictable Prediction Prediction? Time Time If special causes of variation are present, the process output is not stable over time and is not predictable

Process Control A process must first be brought into statistical control. The process mean (X-Bar) and range must be known CONTROLLED STABLE PROCESS (No Special Causes, Only Common causes) Time OUT-OF-CONTROL PROCESS (Special Causes of Variation Present)

Process Stability IN CONTROL AND CAPABLE (Acceptable Variation from Common Causes) IN CONTROL BUT NOT CAPABLE (Excessive Variation from Common Causes) Time UPPER SPECIFICATION LIMIT LOWER SPECIFICATION LIMIT

Process Capability (Cp) Decision Table Cp Value Decision Cp < 1.00 Not Capable Cp = 1.00 – 1.33 Marginally Capable Cp > 1.33 Capable Cp ≥ 2.00 6σ Quality Cp Computation: T = Tolerance = Upper Specification Limit (USL) – Lower Specification Limit (LSL) Cp = T 6 s

Capable Process? T A process may appear to be capable with one set of sample data… = X But how does the process perform over time? LSL Mean Time Down (MTD) USL PQM-201B CPI Tools OCT 2012

Process Performance Index (Cpk) Decision Table Cpk Value (Lower of the 2 values) Decision Cpk < 1.00 Not Meeting Specification Cpk = 1.00 – 1.33 Marginally Meeting Specification Cpk > 1.33 Meeting Specification Cpk ≥ 1.50 6σ Quality Cpk Computation: OR

Process Performance Index (Cpk) Comparison LSL = 16 USL = 24 LSL = 16 USL = 24 Cp= 1.33 Cpk= -0.5 Cp= 1.33 Cpk= 1.00 MTD MTD LSL = 16 USL = 24 LSL = 16 USL = 24 Cp= 1.33 Cpk= 1.33 Cp= 1.33 Cpk= 0 MTD MTD

Cp and Cpk Results Review Cp - simple indicator of process capability potential Cpk - measures how close a process is running to its specification Both analytical tools are useful for understanding if a process is capable of fitting into the specifications or not

Question and Answer For a process to be brought into statistical control, what first must be known? Weight, power, and length Sample size and production batch Root cause and manufacturing process steps Process mean (X-Bar) and range

What analytical tool measures process capability? Question and Answer What analytical tool measures process capability? T Cp Cpk 6σ

Question and Answer What indicator measures how close a process is running to its specification? T Cp Cpk 6σ

DESIGN OF EXPERIMENTS Lesson Topics: Statistical Sampling Seven Quality Tools Process Capability Analysis Design of Experiments

Design of Experiments (DOE) A formal method of analyzing how factors, parts or ingredients in a manufactured product affect its quality, performance or other attributes Components: Factors (inputs to the process) Levels (settings for each factor) Responses (output of the experiment)

Example: DOE Analysis

Benefits of Experimentation Compare alternatives Identify significant inputs affecting an output Separating “the vital few from the trivial many” Achieve an optimal process output Reduce variability Minimize, maximize or target an output Improve process or product robustness Balance tradeoffs

DOE: Seven Steps Define the problem Gather all of the background information Design the test program Plan and carry out the experiment Analyze the data Interpret the results Report conclusions

What is the purpose of the Design of Experiments (DOE) tool? Question and Answer What is the purpose of the Design of Experiments (DOE) tool? Analyzes how factors in a product affect its quality, performance or other attributes Investigates each output factor and how they influence a product’s ingredients

Which of the following is not a step in the DOE process? Question and Answer Which of the following is not a step in the DOE process? Define the problem Gather all of the background information Plan and carry out the experiment Implement the solution

Summary Having completed this lesson, you should now be able to: Identify two methods of statistical sampling Identify quality tools used in a manufacturing context Contrast Process Capability (Cp) and the Process Capability Index (Cpk) as measures of variation Recognize the concepts from the Design of Experiments applied to process improvement

Summary (cont.) Understanding continuous process improvement tools and analysis methods enables you quantitatively monitor your contractors’ manufacturing and supply chain management performance.