Methods Engineering. Methods Engineering

Transcription

1 Methods Engineering 1 Methods Engineering Part II Chapters: 8. Introduction to Methods Engineering and Operations Analysis 9. Charting Techniques 10.Motion Study and Work Design 2 1

2 Chapter 8 Introduction to Methods Engineering and Operations Analysis Sections: 1. Evolution and Scope of Methods Engineering 2. How to Apply Methods Engineering 3. Basic Data Collection and Analysis Techniques 4. Automation and Methods Engineering 3 Methods Engineering Analysis and design of work methods and systems, including the tooling, equipment, technologies, workplace layout, plant layout, and work environment 4 2

3 Other names for methods engineering Work study Work simplification Methods study Process re-engineering Business process re-engineering Methods Engineering is often associated with work measurement. 5 Objectives in Methods Engineering Increase productivity and efficiency Reduce cycle time Reduce product cost Reduce labor content Improve motivation and morale 6 3

4 Effectiveness Vs. Efficiency Effectiveness o Doing the right things (right: job, direction) o It constantly measures if the actual output meets the desired output o It focuses on achieving the end goal Efficiency o Doing things in a right manner (method) o Scientifically, it is defined as the output to input ratio and focuses on getting the maximum output with minimum resources o It is all about focusing on the process, importance is given to the means of doing things 7 o Ratio of actual output to standard output Other Objectives Improve customer satisfaction Improve product and/or service quality Reduce lead times and improve work flow Increase flexibility of work system Improve worker safety Apply more ergonomic work methods Enhance the environment (both inside and outside the facility) 8 4

5 Operations Analysis Study of an operation or group of related operations for the purpose of analyzing their efficiency and effectiveness so that improvements can be developed Objectives in operations analysis Increase productivity Reduce time and cost Improve safety and quality Same basic objectives as methods engineering Methods engineering places more emphasis on design 9 5

6 Evolution and Scope of Methods Engineering Initial research (late 19th century) - Frank Gilbreth: Motion study Scientific management (late 19th century-early 20th century)- Frederick W. Taylor: Motion and time study Primary concern: manual physical labor Today: methods engineering is applied to areas such as indirect labor, logistics, service operations, office work, and plant layout. 11 Methods Engineering Can be divided into two areas: 1. Methods analysis 2. Methods design 12 1

7 Methods Analysis Concerned with the study of an existing method or process o break the method (process) down into work elements or basic operations o examine the details of the elements: a systematic (= purposefully regular, methodical) search to improve the process o This involved checklists of questions and suggestions for improvements Objectives : o Eliminate unnecessary and non-value-adding work elements o Combine elements and operations o Rearrange elements into more logical sequence 13 o Simplify remaining elements and operations Methods Design Concerned with either of the following situations: 1.Design of a new method or process Required for new product or service and there is no existing precedent Method must be designed from scratch, using best existing practice for similar operations 2.Redesign of an existing method or process based on a preceding methods analysis 14 2

8 8.2.1 Systematic Approach in Methods Engineering 1. Define the problem and objectives 2. Analyze the problem 3. Formulate alternatives 4. Evaluate alternatives and select the best solution 5. Implement the best method 6. Audit the study (follow-ups) A systematic approach is more likely to yield operational improvements than an undisciplined approach 15 Step 1: Define the problem and objectives Problem: the reason for needing a systematic approach to determine its solution o low productivity, high cost, inefficient methods, the need for a new method/operation Objective: the desired improvement or new methods design that would result from the project. o Increase productivity, reduce labor content, improve safety, develop a new method The problem definition and the objectives must be specific to the problem under investigation. 16 3

9 Step 2: Analyze the problem Data collection and analysis. Kind of activities involved o Identify the basic function of the operation o Gather background information o Observe existing/similar processes o Collect data o Construct experiments on the process o Develop/utilize a mathematical model of the process o Perform a computer simulation of the process o Use charting techniques 17 Step 3: Formulate Alternatives There are multiple ways to perform a task or accomplish a process. Some of them are more efficient and effective than others Formulate all feasible alternatives 18 4

10 Step 4: Evaluate alternatives and select the best Methodical assessment of the alternatives with respect to the original problem definition and the objectives. Selecting the best one with respect to the objective (but this is not a simple task) 19 Step 5: Implement the best method Install the selected solution o Introduce/institute changes proposed in the existing method o Pilot studies and trials of the new (revised) method o Documentation of the revised method 20 5

11 Step 6: Audit the study Continuous improvement (follow-ups) Fine-tune the organization s problem solving and decision making skills o How successful was the project in terms of the original problem definition and the objectives? o What were the implementation issues? o What should be done differently in the next study? The Techniques of Methods Engineering The following techniques are mostly accociated with the analysis step in the methods engineering. o Charting and diagramming techniques o Motion Study and Work Design o Facility Layout Planning o Work Measurement Techniques o New approaches 22 6

12 Charting & Diagramming Techniques They are available mainly for collecting, displaying and analyzing data Network diagrams Traditional industrial engineering charting techniques o Operation charts o Process charts o Flow diagrams Other (alternative) diagrams o Block diagrams o Process maps 23 Operation Chart for Subassembly 24 7

13 Flow Process Chart 25 Flow Diagram 26 8

14 Block Diagram 27 Basic Process Map 28 9

15 Motion Study and Work Design Concerned with basic motions of a human worker while performing a given task 17 basic motion elements, like reach, grasp, move, release Principles of motion economy - guidelines for work design o Use of human body in developing the standard method (e.g., design the work so that both hands are fully utilized) o Workplace layout o Design of tooling used in the task 29 Motion Study and Work Design -Objective Unnecessary motions can be eliminated. Some of the motion elements can be combined. The method can be simplified. In your project 30 10

16 Facility Layout Planning Facility layout refers to: o Size and shape of a facility o Arrangement of the different departments and equipment within the facility The layout plays an important role in determining the overall efficiency of the operations Problem area includes: o Design of a new facility o Installing new equipment, retiring old equipment o Expanding (or contracting) an existing facility 31 Work Measurement Techniques Four basic work measurement techniques: 1. Direct time study {13} 2. Predetermined motion time systems (PMTS) {14} Use of normal times of basic motion elements to determine standard times 3. Standard data systems {15} Normal times of work elements 4. Work sampling {16} Statistical technique To determine proportion of time spent in activities They can be used in methods engineering to make improvements in the work methods 32 11

17 New Approaches Lean production Based on the Toyota production system Embraced by U.S. companies due to its success at Toyota Six Sigma and other quality-focused programs Widely adopted in industry for improving quality of work processes 5S: The 5-step work organization: Seiri (Sort), Seiton (Set in order), Seiso(Shine), Seiketsu (Standardize), Shitsuke (Sustain) Most of the tools used are adaptations of the old IE principles. 33 Selecting Among Alternative Proposals Need for a systematic procedure to decide among alternative proposals To begin, list the technical features and functional specifications for the application Must features Some features and specifications that should be guaranteed at the minimum level. Desirable features Not must features Criteria matrix to evaluate alternatives Proposals are evaluated against the features and specifications Eliminate candidates that do not satisfy must features Develop scores for desirable features 34 12

18 Evaluation of Robots for Welding Must features: Industrial Robot Candidates Model A Model B Model C Model D Continuous path control OK OK OK OK Six-axis robot arm OK OK Not OK OK Walkthrough programming OK OK OK OK Desirable features: Ease of programming (0-9) Capability to edit program (0-5) Multi-pass features (0-4) Work volume (0-9) Repeatability (0-5) Lowest price (0-5) Delivery (0-3) Evaluation of vendor (0-9) Totals: Evaluation of Robots for Welding Must features: Industrial Robot Candidates Model A Model B Model C Model D Continuous path control OK OK OK OK Six-axis robot arm OK OK Not OK OK Walkthrough programming OK OK OK OK Desirable features: Ease of programming (0-9) Capability to edit program (0-5) Multi-pass features (0-4) Work volume (0-9) Repeatability (0-5) Lowest price (0-5) Delivery (0-3) Evaluation of vendor (0-9) Totals: Eliminate C because, it doesn t satisfy one of the must features Select D because, it has the highest score among desirable features

19 Basic Data Collection & Analysis Tools 1. Histograms 2. Pareto charts 3. Pie charts 4. Check sheets 5. Defect concentration diagrams 6. Scatter diagrams 7. Cause and effect diagrams 37 Histogram A statistical graph consisting of bars representing different values, in which the length of each bar indicates the frequency or relative frequency of each member A useful tool because the analyst can quickly visualize the features of the data, such as: Shape of the distribution (theoretical form, Normal, Gama etc.) Any central tendency in the distribution (single or multimodal) Approximations of the mean and mode (numerical value of the centre) Amount of scatter in the data (variance or risk) 38 14

20 Number of individual parts 39 Histogram for Data Display Normal distribution 40 15

21 Pareto Chart Special form of histogram in which attribute data are arranged according to some criterion such as cost or value Based on Pareto s (XIXth century economist who was trying to analyze the distribution of wealth in Italy) Law: the vital few and the trivial many also known as 80%-20% rule 80% of a nation s wealth is owned by 20% of the population 80% of sales are accounted for by 20% of the SKUs (stock keeping unit or items in stock) 41 Pareto Distribution 42 16

22 Pareto chart as a cumulative frequency distribution 43 Pareto cumulative distribution Can be modeled by where 1 A x y A x for 0 y 1and 0 x 1 y=cumulative fraction of the value variable (e.g., wealth, inventory value, revenue), x=cumulative fraction of the item variable (e.g., population, inventory items, customers) A is a constant determines the shape of the distribution (shape parameter). 17

23 To determine A: A x(1 y) y x 45 Example: Pareto Cumulative Distribution Given: 20% of the total inventory items in a company s warehouse accounts for 80% of the value of the inventory. Determine: (a) The parameter A in the Pareto cumulative distribution equation. (b) Given that the relationship is valid for the remaining inventory, how much of the inventory value is accounted for by 50% of the items? 46 18

24 Example: Solution a) x=0.2, y=0.8 A=(0.20(1-0.8))/( )= x(1 y) A y x b) y=( )(0.5)/( )= A x y for 0 y 1and 0 x 1 A x 50% items in inventory account for 94.1% of the value of the inventory Pie Charts Example: Annual sales revenues and customer distributions for two years 48 19

25 Check Sheet Not check lists Data collection tool generally used in the preliminary stages of a study of a quality problem To recogize the trends Diagnose the problem Identify areas of further study Data often entered by worker as check marks in a given category Examples: Process distribution check sheet - data on process variability Defective item check sheet types and frequencies of defects on the product Defect location check sheet - where defects occur on the product 49 It is clear from the check sheet that the third shift is reponsible for much of the variability in the data. Make an investigation to determine the causes of this variability 50 20

26 The average daily production rate for the third shift is below the daily rate for the other two shifts. 51 Defect Concentration Diagram A drawing of the product (all relevant views), onto which the locations and frequencies of various defect types are added Useful for analyzing the causes of product or part defects By analyzing the defect types and corresponding locations, the underlying causes of the defects can possibly be identified 52 21

27 Defect Concentration Diagram Case study involving final assembly of refrigerators Four views of refrigerator showing locations of surface defects Defects here 53 Defect Concentration Diagram Defects here The defects were clearly shown to be concentrated around the middle section of the refrigerator. Upon investigations, it was learned that a belt was wrapped around each unit for material handling purposes. The defects were caused by the belt. The necessary correction action was taken

28 Scatter Diagrams An x-y plot of data collected on two variables, where a correlation between the variables is suspected It is useful to identify a possible relationship that exists between two processes. The data are plotted as pairs; for each x i value, there is a corresponding y i value The shape of the collection of data points often reveals a pattern or relationship between the two variables 55 Scatter Diagram Effect of cobalt content on wear resistance for a cemented carbide cutting tool Negative correlation: As cobalt increases wear resistance decreases

29 Dr. Mazen arafeh, CSSBB 57 Cause and Effect Diagrams Cause: what makes something happen Effect : what happens (Usually stated in terms of a problem) AKA: Fishbone diagram, Ishikawa Diagram First used by Dr. Kaoru Ishikawa of the University of Tokyo in Used to identify all of the contributing root causes likely to be causing a problem. Dr. Mazen arafeh, CSSBB 58 24

30 Two major formats Dispersion Analysis Type o Constructed by placing individual causes within each major cause category Process Classification Type o Uses the major steps of the process in place of the major cause categories. Then asking of each individual cause Why does this cause (dispersion) happen? Dr. Mazen arafeh, CSSBB 59 Major cause bones that are used Production Process : Service Process : o Machines (equipment) Policies (higher-level decision rules) o Methods (how work is done) Procedures (steps in a task) o Materials (components or raw materials) o Manpower People (the human element) Plant (equipment and space) People (the human element) In both types of processes Mother nature Environment (buildings, logistics, and space) Measurement (calibration and data collection) Dr. Mazen arafeh, CSSBB 60 25

31 Production Process Dr. Mazen arafeh, CSSBB 61 Service Process Dr. Mazen arafeh, CSSBB 62 26

32 Cause and Effect Diagram A graphical-tabular chart used to list and analyze the potential causes of a given problem Can be used to identify which causes are most consequential (related) and how to take corrective action against them Also known as a fishbone diagram or spray diagram 63 Cause and Effect Diagram Six general categories of causes 5M + 1P Machines Equipment, tools etc. Materials Mother nature Enviromental factor such as air temperature, humadity etc. Methods Procedures, sequence of activities etc. Measurement Validty and accuracy of the data collection procedure People 64 27

33 Cause and Effect Diagram 65 Methods Engineering and Automation USA Principle Ten Strategies for Automation Automation Migration Strategy

34 USA Principle 1. Understand the existing process 2. Simplify the process 3. Automate the process 67 Understand the Existing Process What are the inputs? What are the outputs? Number and placement of inspections Number of moves and delays experienced by the work unit Time spent in storage 68 29

35 Mathematical Models What are the important output variables? How are these output variables affected by inputs to the process? Develop mathematical model of the process 69 Simplify the Process What is the purpose of this operation or this transport? Can this step be eliminated? Is the most appropriate technology being used? How can this step be simplified? Can steps be combined? Can steps be performed simultaneously? Can steps be integrated into a manually operated production line? 70 30

36 Automate the Process If simplification is successful, automation may not be necessary If auromation seems to be a feasible soltion, ten strategies provide a road map to search for improvements. Ten strategies for automation Although we refer to them as strategies for automationi same are applicable for just simplification isuues. Automation migration strategy 71 Ten Strategies for Automation 1. Specialization of operations (special punch press) 2. Combined operations (bend both sides) 3. Simultaneous operations (bend and blank) 4. Integration of operations (cut to size, press, snap fit, spot weld) 5. Increased flexibility (cut multiple sizes) 6. Improved material handling and storage 7. On-line inspection (install sensors) 8. Process control and optimization (feedback) 9. Plant operations control (central monitoring) 10. Computer integrated manufacturing (CIM) 72 31

37 Automation Migration Strategy If demand becomes high, more than one single set of workstation is required. Then it makes sense for the company to automate. The following items are the phases encountered by such companies. Phase 1: Manual production using single station manned cells operating independently Phase 2: Automated production using single station automated cells operating independently. Phase 3: Automated integrated production using a multi-station automated system with serial operations and automated transfer of work units between stations. 73 Automation Migration Strategy 74 32