GE6757 TQM UNIT control chartsand tptal productive maintainence

total quality concepts in control charts.control charts,total productive mainaatence

1. Control charts A control chart is a graph that displays data taken over time and the variations of this data. It is a tool to distinguish between chance and assignable causes of variations in a process. The control chart is used to check whether the process is controlled statically or not. Control chart makes possible the diagnosis and correction of the many production troubles. With the help of a control chart, one can find out the natural capability of a production process. The control chart is used to evaluate process stability and to decide when to adjust the process.

2. General form of control chart

3. Types of Control Charts Control charts for variables Control charts for variables require a measurement of the quality characteristic of interest . Control charts for attributes Control charts for attributes require a determination of whether a part is defective or how many defects are there in the sample

4. Rules for identifying out of Control Processes

5. Rules for identifying out of Control Processes

6. Rules for identifying out of Control Processes

7. Rules for identifying out of Control Processes

8. Rules for identifying out of Control Processes

9. Control Charts for Variables The quality characteristics which can be measured and expressed in specific units of measurements are called variables. Control charts based upon measurements of quality characteristics are called as control charts for variables . Types of variable control charts: The most commonly used variable control charts are: X- or average-charts, R- or range-charts, and S -or standard deviation-charts. The X-chart is used to monitor the centering of the process to control its accuracy. The R-chart monitors the dispersion or precision of the process. The s -chart shows the variation of the process

10. Construction of X - and R-Charts Step 1: Select the characteristics for applying a control chart. Step 2: Select the appropriate type of control chart. Step 3: Collect the data. Step 4: Choose the rational sub-group i.e., sample ϯ Step 5: Calculate the average ( x̅ ) and range (R) for each sample. For example, if a sub-group contains 5 items whose dimensions (say diameter or length or weight or etc ) are x 1 , x 2 , x 3 , x 4 ,and x 5 , then

11. Step 6 : Calculate the average of the averages ( ) and average of range ( ). Let N = Number of sub-groups Then , Step 7: Calculate the control limits for x̅ and R-charts .  

12. Step 8: Plot CL, UCL and LCL on the chart. Step.9: Plot individual X and R values on the chart. Step 10: Check whether the process is in control or not. Step 11: Revise the control limits if the points are out-of-control, by removing the out-of-control points.

13. Following table contains the data on the weight of a plastic component in grams. This component is manufactured using a plastic injection molding process. Mean and range charts are required to be established for this process. (i) Determine the trial central line and control limits, (ii) Draw the mean and range charts and plot the values. (iii ) State whether the process is under statistical control, (iv) If not assume that the deviation occurred due to assignable causes which are rectified now. Revise the central line and control limits, (v) Draw the revised mean and range charts and plot the values, (vi) State whether the process is now under statistical control[A . U., No v/Dec 2003]

14. Sample Number Measurements Xl X2 X3 X4 1 6.35 6.40 6.32 6.37 2 6.46 6.37 6.36 6.41 3 6.34 6.40 6.34 6.36 4 6.69 6.64 6.68 6.59 5 6.38 6.34 6.44 6.40 6 6.41 6.40 6.29 6.34 7 6.38 6.44 6.28 6.58 8 6.35 6.41 6.37 6.38 9 6.56 6.55 6.45 6.48 10 6.38 6.40 6.45 6.37

15. To check the process for statistical control: Since all the remaining points are within the revised control limits in both –X bar and R-charts, therefore it can be concluded that the process is in statistical control.  

16. The following table gives the average and range in kilograms for tensile tests on an improved plastic cord. The subgroup size is 4. Determine the trial central line and control limits for X- and R-charts. If any points are out-of-control, assume assignable causes, and determine the revised limits and central line.

17. Control chart for X bar and R are to be established on a certain dimension part measured in millimeters. Data were collected in subgroups sizes of 6 and are given below. Determine the trail central line and control limits .Assume assignable causes and revise the central line and limits. Sample Number Measurements X-bar R X-bar R 1 20.35 0.34 14 20.41 0.36 2 20.40 0.36 15 20.45 0.34 3 20.36 0.32 16 20.34 0.36 4 20.65 0.36 17 20.36 0.37 5 20.20 0.36 18 20.42 0.33 6 20.40 0.35 19 20.50 0.38 7 20.43 0.31 20 20.31 0.35 8 20.37 0.34 21 20.39 0.38 9 20.48 0.30 22 20.39 0.33 10 20.43 0.37 23 20.40 0.32 11 20.39 0.29 24 20.41 0.34 12 20.38 0.30 25 20.40 0.30 13 20.40 0.33

18. QUALITY FUNCTION DEPLOYMENT

19. QUALITY FUNCTION DEPLOYMENT QFD is a method to ensure quality by incorporating the customer requirements in the product from the design, Planning and development stages . It is an upstream process of determining the quality of design needed to satisfy the customer and at the same time improve the key Points for quality assurance . QFD can be viewed as a part of QA. QFD was evolved from QA

20. Objectives of QFD Understanding customer requirements (Customer’s voice) Translate the voice of the customer in Technical parameters in the product. Design the product incorporating the technical parameters of the voice of the customers. Make the system Robust in Design to achieve customer satisfaction in total. Achieve global Quality using strategic bench marking through QFD .

21. House of Quality The house of Quality is a matrix for QFD that relates the customer needs to the product features through technical evaluation and competitive benchmarking. The components of the house of are, Quality Customer voice Product Characteristics Competitive Evaluation Technical Evaluation Relationship matrix Correlation matrix

22. Section I: Customer Requirements The exterior walls of the house are the customer requirements. On the left hand side, the voice of the customer i.e., what the customer expect from the product is listed. Section II: Prioritized Customer Requirements On the right hand side, the prioritized customer requirements or planning matrix are listed . Some of the listed items include customer benchmarking, customer importance rating, target value, scale-up factor, and sales point. Section III: Technical Descriptors The second floor, or ceiling, of the house contains the technical descriptors. Product design characteristics, expressed in engineering terms, are located in this ceiling. Section IV: Relationship Matrix The interior walls of the house are the relationships between customer requirements and technical descriptors. This relationship matrix correlates customer requirements with product characteristics.

23. Section V: Trade-off Matrix The roof of the house is the interrelationship between technical descriptors. Trade-offs between similar and/or conflicting technical descriptors are identified. Section VI: Prioritized Technical Descriptors The foundation of the house is the prioritized technical descriptors . Some of the items included are the technical benchmarking, degree of technical difficulty, and target value

24. QFD Methodology Step 1. List Customer Requirements (WHATs) Define the customer and establish full identification of customer wants and dislikes. Measure the priority of these wants and dislikes using weighing scores. Summarise these customer wants into a small number of major (primary) wants, supported by a number of secondary and tertiary wants . Step 2. List Technical Descriptors (HOWs) Translate the identified customer wants into corresponding ' hows ' or design characteristics. Express them in terms of quantifiable technical parameters or product specifications . Step 3. Develop a Relationship Matrix Between WHATs and HOWs Investigate the relationships between the customers' expectations (WHATs) and the technical descriptors (HOWs ). If a relationship exists, categorise it as strong, medium or weak (or by assigning scores). Step 4. Develop an Interrelationship Matrix Between HOWs Identify any interrelationships between each of the technical descriptors. These relationships are marked in the correlation matrix by either positive or negative. Here a positive correlation represents a strong relationship and a negative correlation represents a weak relationship.

25. Step 5. Competitive Assessments Compare the performance of the product with that of competitive products. Evaluate the product and note the strong and weak points of the product against its competitors' product according to the customer. This competitive assessment tables include two categories: customer assessment and technical assessment. Step 6. Develop Prioritized Customer Requirements Develop the prioritized customer requirements corresponding to each customer requirement in the house of quality on the right side of the customer competitive assessment. These prioritized customer requirements contain columns for importance to customer, target value, scale-up factor, sales point, and an absolute weight. Step 7. Develop Prioritized Technical Descriptors Develop the prioritized technical descriptors corresponding to each technical descriptor in the house of quality below the technical competitive assessment. These prioritized technical descriptors include degree of technical difficulty, target value, and absolute and relative weights. At the end of house of quality analysis, the completed matrix contains much information about which customer requirements are most important, how they relate to proposed new product features, and how competitive products compare with respect to these input and output requirements.

26. QFD PROCESS Phase 1: Product Planning Step 1. List customer requirements (WHATs). Step 2. List technical descriptors (HOWs). Step 3. Develop a relationship matrix between WHATs and HOWs. Step 4. Develop an interrelationship matrix between HOWs. Step 5. Do competitive assessments. Step 6. Develop prioritized customer requirements. Step 7. Develop prioritized technical descriptors Phase II : Part Development Step 8. Deploy QFD process down to sub-components level both in terms of requirements and characteristics. Step 9. Deploy the component deployment chart. Relate the critical sub­component control characteristics.

27. QFD PROCESS Phase III: Process Planning Step 10. Develop the relationship between the critical characteristics and process used to create the characteristics. Step 11. Develop the control plan relating critical control to critical processes. Phase IV : Production Planning Step 12. Tabulate operating instructions from process requirements. Step 13. Develop prototype and do testing. Step 14. Launch the final product to the market.

28. Benefits of QFD QFD is a communication and planning tool that Promotes better understanding of customer demands Improves customer satisfaction Promotes team work Facilitates better understanding of design interactions Involves manufacturing in the design process Breaks down barriers between functions and departments Concentrates on design effort Minimises the number of later engineering changes Introduces new design to the market faster Provides better documentation of the design and development process Reduces the overall costs of design and manufacture.

29. A XYZ company that manufactures bicycle components such as cranks, rims and so forth wants to expand their product line by also producing handlebar stems for mountain bikes. Construct the house of quality (the initial matrix in QFd ) for a handle bar stem by first listing the customer requirements. Then identify the corresponding technical features of the product and develop the various correlations.

30. Total Productive Maintenance “TPM is a management technique that involves every one in a plant or facility in equipment or asset utilization”. “Total productive maintenance permanently improves the overall effectiveness of equipment with the active involvement of operators”. “A partnership between the maintenance and production organizations to improve the product quality, reduce waste, reduce manufacturing cost, increase equipment availability, and improve the company’s overall state of maintenance”.

31. TPM is based on three major concepts. Maximizing equipment effectiveness Autonomous maintenance by operators Small group activities. Seiichi Nakajima as father of TPM It aims at getting the most efficient use of equipment ( ie . Overall efficiency) It establishes a total (company-wide) PM system encompassing maintenance prevention, preventive maintenance and improvement related maintenance. It requires the participation of equipment's designers, . equipment operators and maintenance department workers. It involves every employee from top management to down. It promotes and implements PM, based on autonomous, small group activities .

32. The Objectives of TPM Maximize Overall Equipment Effectiveness (OEE). Establish a thorough system of preventive maintenance for the entire life span of equipment. Implement every TPM by involving all departments (Engineering , Operations, maintenance etc.) Involve every single employee, from top management to worker on the floor. Promote TPM through motivation management- Autonomous small group activities.

33. Pillars of TPM

34. s. No Losses Definition Seven Major losses that impede Overall Equipment Efficiency 1 Failure Losses Losses due to failure. Types of failures include sporadic function stopping failures and function reduction failures in which the function of the equipment drops below normal levels. 2 Set up and adjustment loss Stoppage losses that accompany set up changeovers. 3 Cutting blade change over losses Stoppage losses caused by changing the cutting blade due to breakage 4 Start up losses When starting production the losses that arise until equipment start-up, run-in and production processing conditions stabilize. 5 Minor stoppage and idling losses Losses that occur when the equipment temporarily stops or idles due to sensor actuation or jamming of the work. ,The equipment will operate normally through simple measures (removal of the work and resetting) 6 Speed losses Losses due to actual operating speed falling below the designed speed of the equipment. 7 Defects and rework losses Losses due to defects and reworking.

35. Losses Definition Losses that impede equipment loading time Shutdown (SD) Losses Losses that arise from planed equipment stoppages at the production planning level in order to perform periodic inspection and statutory inspection. Five major losses that impede worker efficiency Management losses Waiting losses that are caused by management, such as waiting foe repair of breakdowns etc. Motion losses Man-hour losses arising from difference in skills involved in steps and adjustment work, cutting blade change work, etc. Line organization losses Idle time losses when waiting for multiple processes or multiple platforms Distribution losses Distribution man-hour losses due to transport of materials, products (processed products) and dollies. Measurement and adjustment losses Work losses from frequent measurement and adjustment in order to prevent the occurrence and outflow of quality defects.

36. Losses Definition Three major losses that impede efficiency use of production subsidiary resources Energy losses Losses due to ineffective utilization of input energy (electric, gas, fuel, oil etc.) Die, Jig and tool losses Financially losses (expenses incurred in production, regrinding, renitriding etc) which occur with production or repairs of dies, jigs and tools due to aging beyond service life or breakage Yield losses Material losses due to difference in the weight of the input materials and weight of the quality products.

37. NEEDS OF TPM Internal Needs Increased production and quality problems resulting from frequent equipment failures. Declining equipment caused by continuous high - load operation. Increase failure in equipment with design weakness. Lack of awareness and expertise in equipment maintenance among operators. Decline in work place morale resulting from dissatisfaction with equipment maintenance. External Needs Truly and effective production of new products. Flexible response to fluctuations in demand. Reduction in price of quality Guaranteed high level of quality. Conservation of materials and energy. Overall needs To transform every ones awareness through activities that reduces costs increase the overall economic effectiveness of equipment. To eliminate breakdowns and defects by practicing PM on a company under basis

38. Aims of TPM To restructure and improve the corporate culture through improvement of human resources and plant equipment. Improving Human Resources: Educate and foster employees so that they can respond to the needs of failure analysis. Operator: Ability to perform ‘ Jishu Hosen’ Maintenance man: Ability to perform high quality maintenance. Production Engineer : Ability to execute maintenance free Equipment plan Improving Plant equipment. Attain efficiency through restoring of the existing equipment. Low cost component (LCC) - considered design of new equipment and minimizing their run up time.

39. Goal of TPM The dual goal of TPM is zero breakdowns and Zero Defects . When breakdowns and defects are eliminated, equipment operation rate improve , costs reduced, inventory can be minimized and as a significance labour productivity increases. TPM can be used as an effective tool for achieving this.

40. Overall Equipment Effectiveness OEE is calculated as follows = Availability x Performance x Quality . Availability = ( Loading time — Down time) / Loading time Loading time = (Working time in a shift – shut down time ) shut down time = Planned equipment stoppage for cleaning & inspection Performance rate = Standard Cycle Time X Product Units Produced Operating Time The factors affecting performance are, Minor stoppage Speed. Quality rate = Product Units Produced - Defective Units Product Units Produced

41. Benefits of TPM Greater equipment effectiveness through skilled workers. Increased productivity, quality, life cycle cost, and have better skill and knowledge of employee. Total elimination of breakdown and losses and continuous productive maintenance . Assured reliability in functions and ease of maintenance. Everyone in the organization work towards a common goal. Skills are shared and everyone grows in understanding and expertise .