Overview. Elementary Quality Tools

Transcription

1 Overview 1. Planned procedure 2. Brainstorming 3. Cause-and-Effect Diagram (Ishikawa) 4. Checklist 5. Flow Chart 6. Data Collection 7. Tally List 8. Data Evaluation 9. Original Value Sequence 10. Histogram (Frequency Distribution Graph) 11. Stratification 12. Pareto Analysis (ABC Analysis) 13. Correlation Diagram 14. Good-Bad Comparison 15. Control Charts 16. Significance 17. Confidence Interval See also Bosch flyer: Elementary Quality Assurance Tools (EWQ) 1

2 Overview (cont'd) The Bosch flyer Elementary Quality Assurance Tools explains important processes and procedures which in practical application have been proven worldwide to be helpful and successful tools for process and quality improvement. These tools can be applied in the following cases: Procedure for improving understanding of processes Procedure for determining the causes of defects Procedure for data collection and analysis 2

3 Overview (cont'd) Quality tools are used to help understand, analyze and improve processes: Application in the problem solving process The correct tool for the relevant problem situation Data and facts prevent useless and time-consuming discussions Technically justified and targeted results aid determination of causes Using these basic tools and dedicated staff, over 90% of all problems can be solved. 3

4 Planned procedure leads to systematic and efficient solutions The literature also refers to this method as P-D-C-A. The name comes from the initial letters of the four sequential steps of the procedure. P D C A Plan Do Check Act A C P D 4

5 Brainstorming Is a technique for gathering ideas Many spontaneous thoughts on a topic are set down in writing and then evaluated. The objective is to find the best solution for a particular problem. Process steps Gathering of ideas Preparation of ideas Documentation Implementation 5

6 Cause-and-Effect Diagram Serves to show the connection between cause and effect Cause-and-effect diagrams are also often called fishbone diagrams or Ishikawa diagrams U R SA Material Solidity Surface Temperature Environment Air pressure Machine Cutting speed Clamping force W IR C H E Workpiece feed Maintenance Man Polishing Grinding Method (Process) Quality of the product K U N G Suggested structure Questions about the effects of man, machine, material, method and environment provide starting points for subclassification. 6

7 Checklist Sequence of written testing and operation procedures, which if followed ensures a planned and systematic procedure Checking off each step confirms that the correct procedure has been followed Example Example (incomplete): (incomplete): Prepare Prepare car car for for vacation vacation Check Check Parts Parts Important Important for for Safety Safety Lights Lights Tire Tire tread tread depths depths Brakes Brakes Clean Clean Car Car Inner Inner chamber chamber Windows Windows Check, Check, Fill Fill Fuel Fuel Cooling Cooling water water Tire Tire pressure pressure 7

8 Flow Chart Serves as graphical representation of step sequences and is often also referred to as a sequential plan of action 8

9 Data Collection Basis for decisions over quality improvement In order to ensure correct evaluation, data must be collected with the greatest of care The 7 questions Why? as a basis for evaluations Which? limitation to appropriate data How many? as many as necessary, as few as possible Where? Location reference Who? Associate reference When? Time reference What with? Measuring equipment reference 9

10 Tally List Is used for simple data collection Records the frequency of occurrence of events no. Result of vehicle - check en by dealer 1 No air in spare wheel 2 Low oil level 3 Wiper blades worn 4 First aid box missing 5 Vehicle exterior dirty 6 Vehicle interior dirty 7 User instructions missing Frequency 10

11 Data Evaluation Especially large quantities of data must be appropriately prepared (evaluated) mathematically and graphically Mathematically determined values for location Graphical representation: and spread: 11

12 Original Value Sequence Collection and representation of data in chronological order of sequence Day of the week Month of the year 12

13 Histogram Grouped data is represented by rectangular bars arranged in a row The lengths of the rectangular bars are proportional to the frequencies of the data falling in the relevant class 13

14 Stratification A technique used to separate data into defined differentials for analysis Machine Machine Event 100% bad A Problem 50% bad B Event 100% good 14

15 Pareto Analysis A technique used to arrange causes (influences) according to their importance 100 % A B C Reasons for late arrival 1. Tired, no desire to get up 45% 2. Alarm clock didn't go off 20% 3. Bus delayed 15% 4. No change for the bus 7% 5. Bus full 5% 6. Bus company on strike 4% 7. Bad weather 3% 8. Various reasons 1% 15

16 Correlation Diagram Enables assessment of a supposed technical relationship between two variables Correlation between cross section area of a nozzle and flow rate Cross section area Flow rate 16

17 Good-Bad Comparison Enables identification of significant differences between different assemblies or system conditions Component Replacement Prerequisite: At least one good and one bad unit are available. The units can be dismantled. Paired Comparison Prerequisite: Several good and several bad units are available. They do not necessarily have to be capable of being dismantled without being destroyed 17

18 Control Charts Record and graphical representation of measured values and/or statistical parameters or counted results in chronological sequence Through comparison with intervention limits, decisions can be made over measures which may be necessary 18

19 Significance "Significance" is generally understood to mean importance or essentiality Practical Significance Statistical Significance 19

20 Confidence Interval Some physical values are never arbitrarily accurate Statistics determined from random samples never correspond to the true values of the parent population Confidence Interval 99 % 95 % Measured value An area in which the true value is thought to lie, in all probability, is called a confidence interval