Eight Basic Quality Improvement Tools – Part 2 Quality Engineering and Quality Management 1 © University of Wisconsin-Madison

2 What are Flowcharts? A flowchart is a pictorial representation of a logical decision process, which identifies all of the major steps and decision points involved in progressing from the beginning to the end. Flowcharts provide a global overview of a “procedure” clearly identifying how each step is related to the others in order to accomplish a particular objective. Begin Step 1 Decision 1YesNo Step 2End Etc.

3 Why Use Flowcharts? To better understand and agree on what the process is in terms of actions and decision points To communicate the flow” of complex processes To determine how the process currently works To determine how the process should work To identify “waste” and opportunities for improvement

4 When to Use Flowcharts? Frequently the first or second step a project team uses. Particularly important for service areas. Flowcharts are typically used during the planning phase of the PDCA problem solving process.

5 What are Cause and Effect (CE) Diagrams? A cause-and-effect diagram is used to show the relationship between some “effect” (problem) and all the possible causes influencing it. By organizing the possible causes in this way, the team can IDENTIFY, EXPLORE, and DISPLAY all of the possible causes of a specific problem or condition.

Example: CE (Fishbone) Diagram Order Entry Error Rate MethodManpower MaterialMachinery Procedures Not Defined Five Depts. Are Involved Poor Communication Second Shift Errors No Customer Call Back Lack of Training No Team Spirit Supervisor #2 Attitude Problem Order From Not Current Purchase Rep. Retired Replacement Not Trained Terminal Key Sticking Lack of Maintenance Printed Orders Hard to Read Old Printer CAUSESEFFECTS

7 Why Use a CE Diagram? Creating a cause and effect diagram is educational It helps a team focus on the issue at hand. It results in an active search for causes. It presents a good graphical layout of the “whole” problem. It’s a way to get at the possible causes of a problem.

8 When to Use a CE Diagram Cause & effect diagrams can be used for defining the causes of any kind of problem! They are used primarily in the planning phase of a problem solving process:

9 What are Scatter Diagrams? Scatter diagrams show the relationship between two factors in a process. Values for one factor are listed on the vertical axis; values for the other factor are listed on the horizontal axis. Points are plotted where their values meet, and the pattern is analyzed to determine the relationship, or correlation, between the factors.

10 Why Use Scatter Diagrams? Scatter diagrams are used to determine if relationships between variables exist in a process. e.g., Are the time it takes to get to work and the time I leave for work related?

Scatter Diagram of Commuting Time 6:00 15 min. 25 min. 10 min. 20 min. 30 min. Time leaving house Travel time to work 7:008:009:00

12 When to Use Scatter Diagrams Scatter diagrams are typically used during the planning phase of the PDCA problem solving process to analyze factors (variables of interest) and determine their relationships (if any).

13 Example of Scatter Diagram Gas Time Core Tensile Strength SO 2 Core Making on Redford 16

14 Compactability Mold Hardness G.S. Molding Example of Scatter Diagram

COMMON PITFALLS: Failing to properly stratify the data Stratified Unstratified x x y y First shift Second shift                             

COMMON PITFALLS: Failing to identify range related correlation –A Correlation may exist in a smaller or larger range than the data set. X Y Correlation

Peaks and Troughs x y x y A' A A

18 Green Sand Compactability LSL USL Stratification Example #2

Green Sand Compactability LSL USL nd Shift USL LSL 1st Shift Stratification Example #2

20 What are Run Charts? Production Days in May Number of castings scrapped due to blows Average

21 Why Use Run Charts? Shows the past, present, and what is “expected” in the future. It focuses attention on trends (compares past performance to present and predicts future) and ranges (how stable our performance is). Can be very motivating, attention-getting, and used to emphasize points which are important and provide feedback on project progress!

22 Why Use Run Charts? Helps us see the effect of improvements over time on process performance. Easy to visualize and understand. Shows us how well we are doing in reaching a desired target level. “A picture is worth a thousand words.”

23 When to Use Run Charts Run charts are typically used during the plan and check phases of the PDCA problem solving process. During the planning phase, run charts are useful when collecting data to look for trends, ranges, and potential causes affecting performance. During the check phase, run charts are useful to help monitor results, display process goals, inform and motivate people.

What to Look for in Run Charts TRENDS CYCLES

What to Look for in Run Charts Runs

26 What are Process Control Charts? Product Quality Characteristic Measurement over Time UCL LCL X Out of Control

27 Process Control Charts X-Bar Chart Time Upper Control Limit = UCL Lower Control Limit = LCL 3x3x 2x2x 1x1x X-bar 1x1x 2x2x 3x3x

28 Why Use Control Charts? Learn About Process – Gain process information and knowledge – Improve process productivity Achieve Stable, Predictable Process Performance – Shifting from what has happened to what will happen – Reduce waste (scrap, rework, etc.) Control charts determine statistically (based on data) when the process is out of control and when some type of controlling action should be taken. This has many benefits:

29 Why Use Control Charts? Measures the Results Against Realistic, Meaningful Measures of Past Performances – Not somebody’s idea of what the performance should be – Take emotion out of the decision-making process, e.g.,

30 When to Use Control Charts Control charts are typically used during the plan, check, and act phases of the PDCA problem solving process to gain insight into how a process is performing and why. They are extremely useful for monitoring critical quality characteristics of a process in order to prevent defects from occurring… ”Do it right the first time!”