Download
1 / 46
460 likes | 653 Views
Chapter 11. The 7 Classic Problem Solving Tools. Check sheets Pareto Charts Flow charts Cause and effect diagram Histograms Control Charts Scatter Diagrams. Project Charter. Teamwork.
E N D
The 7 Classic Problem Solving Tools • Check sheets • Pareto Charts • Flow charts • Cause and effect diagram • Histograms • Control Charts • Scatter Diagrams
Teamwork Teams should be comprised of key individuals directly involved with the process being addressed. Other functional representatives can be brought in as needed. Each individual brings unique expertise and perspective to the team and melds that with the talents of the other team members. The team process leads to decisions of higher quality than those arrived at by individuals. Moreover, members of a team are much more willing to take ownership in the resultant decisions and to actively pursue their successful implementation.
Launch #1 Using what you are given baseline the process for shooting the statapult. Remember: Customer desires a rapid-fire, precise, and accurate launcher that can launch projectiles over mountain ranges. Group Activity
Brainstorming 1. Clearly state the problem and make sure that all team members understand it 2. Allow each team member to present his or her ideas 3. Record each suggestion exactly as it was stated. Make no preliminary judgments on ideas 4. Decide which ideas should be acted upon first, which ones can wait, and which ones aren't applicable 5. Decide how each idea will be acted upon. Determine who is responsible and when those actions will be done by. 6. Document all results for use in future meetings, or as evidence that the problem is fixed. 7. Create a file somewhere in the department to document what problems have been fixed, and what problems still need to be worked on 8. If a project is generated from the Brainstorm session, before leaving the meeting make sure that everyone understands who is Responsible, who is Accountable, who are the key Contacts, and whom we should keep Informed throughout the project.
Defect check sheet Objective: Develop a check sheet for what you think is causing you problems with accuracy.
Pareto Chart Objective: Develop a Pareto Chart from the data you recorded on the check sheet.
Process Flow Chart Objective: Develop a process flow diagram that explains how to launch a ball.
Cause and Effect Diagram Objective: Develop a C&E diagram that explains the variability of the launching process. Label as C/N/X.
SOP Objective: Develop an SOP that accurately defines each controlled step of the launching process.
Why talk about error-proofing? • Demonstrate the importance of error proofing • Show error proofing is not difficult • Simplification and standardization is key • Make everyone’s job easier • Encourage you to recognize the opportunities for error proofing • Operator error rarely acceptable as root cause • Operator training rarely acceptable as corrective action • Incorporate into all of your improvement projects
Human Causes Relative Proportion of Accidents Frequency Machine Causes Time Aircraft Accident Causes Last 20 Years The reliability of the parts themselves have improved dramatically. What has not improved is the ability of humans to adequately comprehend and attend to the process of assembling and maintaining these dramatically more complex machines correctly. Source: FAA Human Factors Guide to Aviation Maintenance
Air Traffic Control Errors In response to a sharp increase in air traffic control errors nationwide and the near-collision of two planes over New York's La Guardia Airport, the FAA has: You make the call… A. Ordered retraining for 10,000 air traffic controllers. B. Hired a team of experts to pareto errors, look for trends, and find the root cause for the errors. C. Base future salary actions on controller’s performance. D. Rewrite the operating procedures placing messages and warnings in appropriate locations.
Nuclear Safety: Experts Blame Japanese Incident On Incorrect Equipment (Matthew L. Wald, New York Times, Oct. 23, 1999). -- CF After touring the site of last month's nuclear incident in Japan, three Energy Department experts said the plant's managers expected workers to follow safety rules but never explained why the rules were important.Frank McCoy, deputy manager of the DOE's Savannah River Operations Office, said technicians at the Tokaimura plant were using incorrect equipment to process nuclear fuel. McCoy: "Using the system in the right way was more difficult than anyone would have desired." The experts said the workers did not understand the reasons behind rules limiting the size of batches and containers.On Sept. 30, plant workers brought too much uranium together in one spot and created a chain reaction that lasted for 17 hours.
Examples: 1) Misses Hole 2) Worn drill 3) Wrong drill Errors are difficult to manage using statistics. Special causes Hole diameter 1 2 3 • Most of our processes are at a relatively high sigma, therefore sampling unlikely to catch abnormalities: sampling aimed at catching process drift not defects • Want to use error proofing to eliminate the tails of the distribution 1998, John R. Grout
Depending on task and environment humans are typically 2 to 3 sigma • Errors will occur the trick is preventing them from becoming defects and escaping to the field Error Probability Knowledge-based ( Perform theory based analysis) Skill- based (routine actions, perform on autopilot) Task TypeMean P(d)s level - Initial problem solving or 0.2 0.85 Troubleshooting - Detection of deviation or 0.07 1.45 inspection - Calculation 0.04 1.75 - Dial a 7 Digit phone number 0.021 2.05 - Alpha input per character 0.008 2.40 - Numeric input per character 0.003 2.75 - Control action per demand 0.001 3.10 - Assembly per task element 0.00007 3.80 Data from “Human Reliability Data - The State of the Art and the Possibilities” Jeremy C. Williams, 1989 CEGB
The concept of poka-yoke has existed for a long time but it was Japanese manufacturing engineer Shiego Shingo who developed the idea into a formidable tool for achieving zero defects. Shingo came up with the term poka-yoke which generally translates as “mistake-proofing” or “fail-safing” – to avoid (yokeru) inadvertent errors (poka). What is “POKA-YOKE”? • Generally, any manufacturing or transactional process is dependant on human intervention, look for ways to either minimize the intervention (automation, menu choices, mouse clicks vs. typing), or if human intervention cannot be reduced, look for ways/methods of…. • Mistake proofing the form/process (provide a template or overlay) • Color coding instructions or the form (certain functions only fill-in a certain color on the form) • Minimize the writing required (have repetitive or standard info hard printed onto the form) • If the form is electronic limiting access, blocking certain entries, having the computer verify information, or granting certain permissions may provide some relief.
Red flags for error proofing Technique Inadvertent Willful Excerpted from: Poka-yoke Improving Product Quality by Preventing Defects
Error Proofing Excerpted from: Poka-yoke Improving Product Quality by Preventing Defects
What can we do? • Demand vigilance • ask designers and workers to “be more careful!” • continue the “blame and train cycle”
A New Attitude toward Preventing Errors • Eliminate the chance of making the error • Provide automatic feedback to sense and fix the error • Make incorrect actions correct • Make wrong actions more difficult • Make it easier to discover the errors that occur • Make it possible to reverse actions - to “undo” them - or make it harder to do what cannot be reversed • Source inspection • 100% inspection • Immediate feedback and corrective action.
I. Error Elimination - Prevention - The opportunity to make the error no longer exists in the process. II. Automatic Feedback “Poke-Yoke” devices - The error is automatically detected and the process halted prior to making a defect. III. Defect Detection and process adjustment -”Source Inspection” Defect is discovered at the operation where generated. Error Proofing Process Improvement IV. Make it easier to do it right. Colors, color coding, shapes, symbols, kitting, checklists, forms, procedures, process simplification Subsequent Inspection, Audits, Perfection Reviews, TPM Error Proofing - Process Improvement Best
Make it easier to do it right! Provide clues about what to do through the use of: natural mappings visibility feedback Put “Knowledge in the World” Source: The Design of Everyday Things, by D.A. Norman, 1988, Doubleday
Which dial turns on the burner? Natural mappings: Stove A Stove B
Visibility and feedback • Visibility means making relevant parts visible(kitting) and effectively displaying system status • Feedback means providing an immediate and obvious effect for each action taken. • This is how you can error proof anything. If you can provide immediate feedback to the human operating the process, he/she will correct the error before a defect is generated.
Benefits of error proofing • Customer Satisfaction - Process variation hurts customers but it is normally the special causes which cause them the most pain • Must detect errors and prevent defects from escaping • Reduces production disruption along the supply chain and the associated cost and liability • Cost reduction - scrap and rework and fixing downstream problems are reduced dramatically
Takeaways • Error proofing is of critical importance internally and at the customer • Addresses the outliers and affects what the customers see • Whenever dealing with processes look for the red flags and excessive operator intervention • Process walks are easy to perform and effective • You must error proof in the control phase • Don’t accept operator error as root cause or operator training as the only corrective action To achieve zero defect levels you must error proof
Failure Mode and Effects Analysis • Overview • Why • How • FMEA Types • FMEA Steps • The FMEA Process • Severity Table
FMEA overview • Identifies potential product related process failure modes. • Assesses the potential customer effects of the failures. • Identifies the potential manufacturing or assembly process causes and identifies process variables on which to focus controls for occurrence reduction or detection of the failure conditions. • Develops a ranked list of potential failure modes, thus establishing a priority system for corrective action considerations. • Documents the results of the manufacturing or assembly process.
FMEA terms • Failure Mode – The manner in which a part or process can fail to meet specification. It is usually associated with a defect or nonconformance. • Effect – The impact on a customer if a failure mode is not prevented or corrected. The customer can be an immediate one or one downstream. • Cause – A deficiency that results in a failure mode. Causes are sources of variability associated with key process input variables. • A FMEA is best when a team prepares it. The team should be made up of people from all areas impacted by the process.The FMEA is useful in a number of applications: in determining X’s, helping to define process improvements and controls, and others.
Types of FMEA’s • A System FMEA is used to analyze systems and subsystems in early concept and design stages. It focuses on potential failure modes associated with the functions of a system caused by design. • A Design FMEA is used to analyze products before they are release to production. • A Process FMEA is used to analyze manufacturing, assembly, and transactional processes. • A Product FMEA is used to analyze failure modes that could occur to the product once it gets into the customers hands.
FMEA process steps Preparation • A FMEA begins with a process map. Identify the process and map its key steps. • List the key process outputs to satisfy customer requirements. • List the key process inputs for each process step. • Define a matrix relating product outputs to process variables . • Rank inputs according to their importance. The goal in your preparation is to have a complete understanding of the process you are analyzing. What are its steps? What are its inputs and outputs? How do they relate? **Information for this section taken from: GE Six Sigma Playbook and the AIAG Reference Manual.**
FMEA Risk Priority No. Calculate the Risk Priority Number (RPN). This is a calculation of the relative risk of a particular failure mode given the ratings assigned for severity, occurrence, and detection. To calculate, apply the following equation: RPN = SEV * OCC * DET The higher the RPN, the greater the risk for a failure mode! Careful analysis provides a priority for action. Improvement Avoid analysis paralysis. The object of a FMEA is to initiate action. Select the trouble areas that cause the top few causes. Determine what action will reduce RPN’s and establish time frames for their completion. Assign responsibilities. Once action brings about results, recalculate RPN’s and put controls into place.
