Learning Objectives • Define the relationship between Cause and Effect • Explain use and construction of: • Fishbone Diagram • Guidelines for Brainstorming • Cause and Effect Matrix • Learn how to integrate Fishbone Diagram and Cause & Effect Matrix into your Company SOPs
What do you mean by “ Cause & Effect”? A PROBLEM WHICH HAS OCCURED A POTENTIAL FUTURE PROBLEM (FMEA) EFFECT Symptoms that provide evidence of the problem EFFECT Symptoms that would result from the problem CAUSE Events/conditions that led to the problem CAUSE Events/conditions that would lead to the problem Dave Wessel, “An Ounce of Prevention”, Quality Progress, Dec, 1998
A PROBLEM WHICH HAS OCCURED EFFECT Symptoms that provide evidence of the problem CORRECTIVE Eliminates the CAUSE of a problem ADAPTIVE Limits the EFFECT of a problem or deviation ACTION Cause - Effect Relationship CAUSE Events/conditions that led to the problem Dave Wessel, “An Ounce of Prevention”, Quality Progress, Dec, 1998
C/N/X Materials Methods C C N N Problem/ Desired Improvement N N N C C C Machinery Manpower What is a Fishbone Diagram? A visual tool used to identify, explore and graphically display all the possible causes related to a problem to discover root causes. A Fishbone diagram is also known as a Cause and Effect Diagram or Ishikawa Diagram.
Dr Kaoru Ishikawa • Quality control statistician • Professor in University of Tokyo • One of the pioneers of Japan’s quality revolution in the 1940s • Played major role in growth of QC circles • Best known for formalizing use of Cause-and-Effect Diagram • Won the Deming Prize and Shewhart Medal • ASQ established the Ishikawa Medal to recognize the human side of quality
Why Use Fishbone Diagrams? • To discover the most probable causes to a problem (or effect) • Sometimes, the effect can be a desirable effect. • When something desirable has happened, it is useful to find out what caused it so that you can make it happen again • To visual possible relationships between causes for a given problem under investigation
Constructing a Fishbone Diagram • Establish what the problem (effect) is • It must be stated in clear and concise terms, agreed by everyone. • Write the effect on the head of the fish • Decide the major categories of causes • Brainstorming • Use standard categories such as 5M+E (Machines, Materials, Methods, Manpower, Measurement & Environment) • Use major steps in the process if the effect is resulted from a recognizable process • See example???? Let’s create a Fishbone Diagram using Minitab
Constructing a Fishbone Diagram StatðQuality Tools ðCause-and-Effect
Constructing a Fishbone Diagram Fishbone Diagram for Surface Flaws List specific causes in each category Measurements Materials Man Surface Flaws Problem (effect) at the “head of the fish” Environment Methods Machines Major categories of causes (or sometimes call major bones) Why do we need to group the causes?
Constructing a Fishbone Diagram • 4. Identify possible causes through Brainstorming • Identify specific causes within each major category that may be affecting the problem. Fishbone Diagram for Surface Flaws Measurements Materials Personnel • 3. Continue asking: ‘Why is this happening?’ until you no longer get useful information. • 2. Repeat this procedure with each specific cause to produce sub-causes. Micrometers Calibration Method Alloys Shifts Calibration Interval Precision Accuracy Lubricants Supervisors Suppliers Training Microscopes Operators Inspectors Surface Flaws Machine feedrate Speed Machine rpm Brake Lathes Brand of bit Condensation Engager Bits Sizeof bit • 1. The team should ask : ‘What are the machine issues affecting/causing the problem?’ Moisture% Angle Sockets Environment Methods Machines When do we know we have reached the root cause ?
Analyzing a Fishbone Diagram 5. When brainstorming session is completed, every cause should be labeled as either a “C”, “N” or “X”. C variables that must be held as constant as possible and require standard operating procedures to insure consistency N variables that are noise or uncontrolled variables and cannot be cheaply/easily held constant X variables considered to be KPIVs and need to be experimented to determine what influence each has on the output and what their optimal settings should be to achieve customer-desired performance
Analyzing a Fishbone Diagram • 6. The team should analyze and zoom in those “most likely causes”. • Helpful Hint • Look out for causes that appear in more than one category. They may be the “most likely causes”. • 7. The most likely causes should be prioritized for further investigation.
Integrating Fishbone Diagram into SOPs Example of how fishbone diagram can be used in SCAR. Section of SCAR Procedure Received complaint/reject from customer, in-house or supplier. Generate report for management review Fishbone diagram can be used here to brainstorm/ identify root causes QA personnel verify the defects. Follow up on CAR Issue CAR to production. -receive CAR reply from production - reply to customer Purge in-house stock Hold meeting with relevant departments (if necessary) • Fishbone diagram can be used here to brainstorm/ identify root causes. • To prioritize and work on most likely causes. Should also update Fishbone diagram
Integrating Fishbone Diagram into SOPs Example of how fishbone diagram can be used in SPC control Section of SPC Control Procedure Fishbone diagram can be used here to brainstorm/ identify root causes
Link Tools Integration Tasks to Work Breakdown Structure The effort to integrate Fishbone Diagram into SPC and SCAR procedures should be translated into specific tasks in the Work Breakdown Structure.
Description: Cause and Effects Matrix • Simple QFD (Quality Function Deployment) matrix. • Used to relate and prioritize X’s to customer Y’s through numerical ranking using the process map as the primary source. • Y’s are scored as importance to the customer • X’s are scored as to relationship to outputs • This is the team’s first stab at determining Y = f(X) • Results • Pareto of Key Inputs to evaluate in the FMEA and Control Plans • Input into the Capability Study • Input into the initial evaluation of the Process Control Plan
Constructing a Cause & Effect Matrix 1. List key outputs (Y’s)
Constructing a Cause & Effect Matrix 2. Rank Y’s with respect to customer importance
Constructing a Cause & Effect Matrix 3. List key inputs (X’s) Input Variables
Constructing a Cause & Effect Matrix • You are ready to correlate customer requirements to the process input variables • Avoid confusion and inconsistency by establishing scoring criteria: 0 = no correlation 1 = the process effect only remotely affects the customer requirement 4 = The input variable has a moderate effect on the customer requirement 9 = The input variable has a direct and strong effect on the customer requirements Note: Not recommended to use more than 5 different criteria.
Constructing a Cause & Effect Matrix 4. Relate X’s to Y’s X’s Y’s
Constructing a Cause & Effect Matrix 5. Cross-multiply and add Key inputs are now ranked in importance with respect to the key outputs So??
How Cause & Effect can Fit into Process Improvement Activities C&E Matrix The Big Picture Outputs Inputs Capability Summary Control Plan Summary FMEA The Key Outputs are evaluated ability to meet customer spec. The Key Inputs are evaluated for process control Key Inputs are explored while evaluating process for potential failure
Integrating Cause & Effect Matrix into SOPs Example of how Cause and Effect Matrix can be used in SCAR. Section of SCAR Procedure Received complaint/reject from customer, in-house or supplier. Generate report for management review Cause and Effect Matrix can be used in conjunction with fishbone diagram to identify, rank and prioritize the key causes. QA personnel verify the defects. Follow up on CAR Issue CAR to production. -receive CAR reply from production - reply to customer Purge in-house stock Hold meeting with relevant departments (if necessary) Cause and Effect Matrix can be used in conjunction with fishbone diagram to identify, rank and prioritize the key causes.
Integrating Cause & Effect Matrix into SOPs Example of how Cause & Effect Matrix can be used in SPC control Section of SPC Control Procedure Cause and Effect Matrix can be used in conjunction with fishbone diagram to identify, rank and prioritize the key causes.
Link Tools Integration Tasks to Work Breakdown Structure The effort to integrate Cause & Effect Matrix into SPC and SCAR procedures should be translated into specific tasks in the Work Breakdown Structure.
Transactional Example Estimated Ship Date Change - CAUSE & EFFECT / FISHBONE WCSC PRACTICES MDC CAPACITY MDC PRACTICES SCHEDULE CHANGES - Unrealistic Del. Req Dates - Customer Order Priority Changes - B.O.. Consol. - SC late - Firm - Planned - Receiving - Picking - PC delays - Off shift support ORDER CANCELLATION Estimated Ship Date Changes - Bad IT days - Table Maint. - Waiting for Delivery Appt. PLANNED SHIP DATE ALGORITHM - No Delivery Constraints After initial PSD - Back Ord. Release Logic - Cust Priority vs. availability -Future orders at AP - Availability Overrides - No Stocks IN TRANSIT TIMES - Late PT print - Late EDI data ESD ALGORITHM ANOMALIES APPOINTMENT CUSTOMER INVENTORY ACCURACY LDSS
Brainstorming ? A technique to generate a large number of ideas or possibilities in a relatively short time frame. ? ? ? ? ? • Why Use Brainstorming? • A tool for the Team (not individual) • A method to generate a lot of ideas • Two persons’ knowledge and ideas are • always more than an individual’s • Input for other C&E tools • Active participation
How to Conduct a Brainstorming Session Team Makeup • Experts • “Semi” experts • Implementers • Analysts • Technical staff who will run the experiment • Operators Discussion Rules • Suspend judgement • Strive for quantity • Generate wild ideas • Build on the ideas of others Leader’s rules for Brainstorming • Be enthusiastic • Capture all the ideas • Make sure you have a good skills mix • Push for quantity • Strictly enforce the rules • Keep intensity high • Get participation from everybody
Products are failing for contamination Base castings leak at mounting screw hole WHY? Suppliers leak test may not detect porosity leak WHY? WHY? Suppliers have different leak test processes Can I cause the break if I stop here? No standard process for supplier leak test WHY? Root Cause How do we know when we have reached ROOT CAUSE ? Root Cause is the lowest cause in a chain of cause and effect at which we have some capability to cause the break • It’s within our capability to unilaterally control, or to influence, changes to the cause
SPHERE OF INFLUENCE (Influence or persuasion only) SPAN OF CONTROL (Full authority) Span of Control / Sphere of Influence Before we begin, we must establish the context in which the Cause-Effect will be used. Span of Control- areas where we have a high degree of control over parts or functions, virtually complete authority to change anything Sphere of Influence- areas where we can influence things to varying degrees but don’t have direct control. Outside Environment- where we have neither control nor influence OUTSIDE, UNCONTROLLED ENVIRONMENT
Points to Note for Fishbone Diagram • Treat the cause-and-effect diagram as a living document • As new variables are discovered, update the cause-and-effect diagram • After your experimental investigations, when you have optimized the “X” factors, and implemented control, update them to “C”. • Therefore, ideally, when the fishbone diagram has more “C”s, the better we can control the effect and improve its performance measure.