1、2002/9/26,SMT Training for Productivity,1,Industrial Engineering : Work Design,Prepared by Ken Leung,2002/9/26,SMT Training for Productivity,2,Work Design,Methods Improvement Ergonomics Assembly line balancing Principles of motion economy Various type of charts Work measurement Time study Activity s
2、ampling,2002/9/26,SMT Training for Productivity,3,Ergonomics,Definition Apply information about human behavior, abilities, limitations, and other characteristics to the design of tools, machines, system, tasks, jobs, and environments for productive, safe, comfortable, and effective human use.,2002/9
3、/26,SMT Training for Productivity,4,Objectives,To enhance the work effectiveness and efficiency. Increased convenience of use Reduced errors Increased productivity To enhance human values. Improved safety Reduced fatigue and stress Increased comfort Greater user acceptance Increased job satisfaction
4、 Improved quality of life,2002/9/26,SMT Training for Productivity,5,Twelve Principles of Ergonomics,1. Work in neutral postures eg. Wrist rests for keyboard and mouse.2. Reduce excessive forces eg. Boxes with handholds for carrying.,2002/9/26,SMT Training for Productivity,6,Ergonomics Principles,3.
5、Keep everything in easy reach eg. Keep materials within the “reach envelope” of the arm.,2002/9/26,SMT Training for Productivity,7,Ergonomics Principles,4. Work at proper heights eg. Heavy work should be performed lower than elbow height; precision work should be higher.,2002/9/26,SMT Training for P
6、roductivity,8,Ergonomics Principles,5. Reduce excessive motions eg. Use power screwdriver.6. Minimize static load eg. Use a pencil grip.,2002/9/26,SMT Training for Productivity,9,Ergonomics Principles,7. Minimize pressure points eg. Provide padding for hand grips.8. Provide clearance eg. Provide vis
7、ual access (carton delivery).,2002/9/26,SMT Training for Productivity,10,Ergonomics Principles,9. Move, exercise, and stretch eg. Change adjustments of the chair for those sit for a long time. 10. Maintain a comfortable environment eg. Consider the quantity and quality of light at the workstation.,2
8、002/9/26,SMT Training for Productivity,11,Ergonomics Principles,11. Make displays and controls understandable eg. Clicking is easier than memorizing commands. 12. Reduce stress eg. Design task to fit people.,2002/9/26,SMT Training for Productivity,12,Anthropometry,Definition Measurement of the human
9、 body and its biomechanical characteristics. Biomechanical refers to the mechanical (machine-like) capabilities of the human skeleton-muscular systems. Measures our sizes and how we move and move easily. Need of Anthropometry We are not in the same size. Poor design for mechanical abilities of the h
10、uman body can lead to discomfort or injury. Eg. Height of keyboard for a computer.,2002/9/26,SMT Training for Productivity,13,Anthropometric Data,Static measures are used to determine size and spacing requirements of work space, eg., height, weight, seat to elbow height, and wing span. Dynamic measu
11、res are used to match the dynamic characteristics of controls to user, eg., range of motion for various joints, and strength of fingers.,2002/9/26,SMT Training for Productivity,14,Anthropometric Data,The anthropometric data is performed in normal distribution. 50th percentile is the most of the popu
12、lation. 5th and 95th percentiles are the extremes.,2002/9/26,SMT Training for Productivity,15,How to use anthropometric data,Design for extremes A standard is to design to fit 5th or 95th percentiles of the population. Design for most of the population 50th percentile of the population should be use
13、d. Make the design adjustable The design can fit 5th to 95th percentiles of the population.,2002/9/26,SMT Training for Productivity,16,Examples,2002/9/26,SMT Training for Productivity,17,Assembly Line Balancing,Equalize workload among the assemblies. Identify the bottleneck operation. Establish the
14、speed of the assembly line. Determine the number of work stations. Determine the labor cost of assembly. Establish the percent workload of each operator. Assist in plant layout. Reduce production cost.,2002/9/26,SMT Training for Productivity,18,Table for Assembly Line Balancing,Major items: operatio
15、n description, R-value, cycle time, number of stations, average cycle time, percent load, hours per 1000 pieces, and number of pieces per hour.An example is as follows.,1,2,3,4,5,6,7,2002/9/26,SMT Training for Productivity,19,Items for Assembly Line Balancing Table,R-value (plant rate): Takt time or
16、 time needed to produce a product. = effective production time / required production volume. Cycle time: Standard time for operation. Collected from time study. # stations: = Cycle time / R-value Average cycle time: = Cycle time / # stations,1,2,3,4,2002/9/26,SMT Training for Productivity,20,Items f
17、or Assembly Line Balancing Table,% Load: Tell how busy each work station is compared to the busiest work station. % Load = Avg. cycle time / highest avg. cycle time. Highest avg. cycle time (100% station) is the bottleneck. 100% station is reduced by 1%, then we will save 1% for all stations. The le
18、ss percent loaded, the more desirable to be sub-assembled or combined.,5,2002/9/26,SMT Training for Productivity,21,Items for Assembly Line Balancing Table,Hours / 1000 : The hours per 1000 units produced. Choose the bottleneck station. = (Avg. cycle time / 60 mins) x 1000 For more than one workers
19、at the station, “hrs/1000” = # workers x “hrs/1000” of bottleneck. Because everyone on an assembly line must work at the same rate. Pcs. / hr : Number of units produced hourly by one worker at the station. = 1 / “Hrs/1000” X 1000,6,7,2002/9/26,SMT Training for Productivity,22,Improve Assembly Line B
20、alancing,Calculate the Line Balance rateReducing the bottleneck station. Combining the bottleneck station with an operation in front or behind. Combining other operations to eliminate one of them.,2002/9/26,SMT Training for Productivity,23,Example: Original Line Balance,Producing new plastic charger
21、; 1200 units per 8-hrs shift (with 300 mins effective).,2002/9/26,SMT Training for Productivity,24,Example: Original Line Balance,Original line balance rate= total cycle time / highest cycle time station x no. of stations= 1.354 / (0.25 x 7) = 77.4% Pcs./hr = 60 / 0.25 = 240 Improve the bottleneck s
22、tation by combining with an operation in front or behind. Combine and eliminate work steps. Re-design the jig & fixture.,Operations,Bottleneck or 100% load station,2002/9/26,SMT Training for Productivity,25,Example: Improved Line Balance,Improved line balance,2002/9/26,SMT Training for Productivity,
23、26,Example: Improved Line Balance,Improved line balance rate= total cycle time / highest cycle time station x no. of stations= 0.878 / (0.229 x 4) = 95.9% Pcs/hr = 60 / 0.229 = 262 Increase in output with decrease in no. of workstations.,Operations,Bottleneck or 100% load station,2002/9/26,SMT Train
24、ing for Productivity,27,Principles of Motion Economy,Guidelines for efficient and effective work station design. Summarized to 4 major elements: Elimination Combination Rearrangement Simplification,2002/9/26,SMT Training for Productivity,28,Elimination,Eliminate all possible jobs, steps, or motions.
25、 Eliminate irregularities in job. Eliminate the use of hand as holding device. Eliminate abnormal motions. Eliminate the use of muscles to maintain a fixed position. Eliminate muscular force by using power tools. Eliminate danger. Eliminate idle time.,2002/9/26,SMT Training for Productivity,29,Combi
26、nation,Replace with one continuous short motion. Combine tools, controls, and motions. Rearrangement Distribute the work evenly between two hands. Shift work from the hands to the eyes. Arrange for a straight forward order of work.,2002/9/26,SMT Training for Productivity,30,Simplification,Reduce eye
27、 travel. Keep work in the normal work area. Shorten motions. Adapt handles, levers, pedals, buttons, etc., to human dimensions and musculatures.,2002/9/26,SMT Training for Productivity,31,Applying the Principles of Motion Economy,1. Move both arms in unison or move them symmetrically, but do not mov
28、e just one arm at a time.Eg. Take the cap off an ink bottle.,2002/9/26,SMT Training for Productivity,32,Applying the Principles of Motion Economy,2. To minimize body movement by limiting movements to body parts with low time rankings.The following illustration shows the correlation between arm movem
29、ent and working time.,2002/9/26,SMT Training for Productivity,33,Applying the Principles of Motion Economy,3. Minimize fatigue by repeating motions with a natural feeling of rhythm and by making your curved movements as smooth as possible.Do as little holding or adjusting of materials as you can.Use
30、 stands or jigs to hold your materials or tools for you.,2002/9/26,SMT Training for Productivity,34,Applying the Principles of Motion Economy,4. Keep materials and tools in specified places in front of and around you.5. Try to keep from fighting gravity with the materials you are handling; move them
31、 down, not up.Eg. Use a chute to transport the products by its own gravity.,2002/9/26,SMT Training for Productivity,35,Applying the Principles of Motion Economy,6. Try to set your chair or desk at the most comfortable position and make sure your lighting is bright enough and at a good angle.7. If yo
32、u utilize your legs and feet, you can lighten the load on your arms and hands.,2002/9/26,SMT Training for Productivity,36,Applying the Principles of Motion Economy,8. Side-to-side eye movements are less tiring than up-and-down ones.9. Whenever possible, combine procedures, using your tools as extens
33、ions of your hands and feet. Try to combine two or more tools into one.,2002/9/26,SMT Training for Productivity,37,Various types of charts,Used as record techniques Outline process charts: Overview of a process with graphical representation. Show principal operations () and inspections (). Assist in
34、 the plant layout design, design of product, or machinery processes.,2002/9/26,SMT Training for Productivity,38,Various types of charts,Flow process chart: Activities of men, material or equipment. Two or more subjects can be presented alongside each other to show their interdependence. Activities a
35、re divided by 5 functions, operation (), transport (), storage (), delay (D), inspection (). Only the activities of particular subject, either man, material, or equipment, are recorded on a single chart.,2002/9/26,SMT Training for Productivity,39,Example,Flow process chart:Inspecting and markinginco
36、ming parts(original method),2002/9/26,SMT Training for Productivity,40,Example,Flow process chart:Inspecting and markingincoming parts(improved method),2002/9/26,SMT Training for Productivity,41,Various types of charts,Tow-handed process chart: Useful in showing idle time by either hand. Activities
37、of a workers two hands. Simultaneous movements by both hands appear opposite each other. Description of the activities represented by the symbols should be inserted.,2002/9/26,SMT Training for Productivity,42,Example,Two-handed process chart:Cutting glass tubes(original method),2002/9/26,SMT Trainin
38、g for Productivity,43,Example,Two-handed process chart:Cutting glass tubes(improved method),2002/9/26,SMT Training for Productivity,44,Various types of charts,Multiple activity charts: Consider on the activities of a subject in relation to one or more others. Show up clearly ineffective time within
39、the process. Useful in finding the best sequence of carrying out the various parts of the work. Operation / machine chart shows the interrelationship of the operator and the machine.,2002/9/26,SMT Training for Productivity,45,Example,Multiple activity chart worker and machine:Finish mill casting (or
40、iginal method),2002/9/26,SMT Training for Productivity,46,Example,Multiple activity chart worker and machine:Finish mill casting (improved method),2002/9/26,SMT Training for Productivity,47,Time Study,Most common technique for setting time standards. Useful for repetitive work. Provide standard rate
41、 of working. A means of assessing the amount of rest that should be associated with the job.,2002/9/26,SMT Training for Productivity,48,Time Study: Procedures,1. Select the job to study. 2. Collect information about the job. 3. Divide the job into elements. 4. Do the actual time study. 5. Extend the
42、 time study.,6. Determine the number of cycles to be timed. 7. Rate, level, and normalize the operators performance. 8. Apply allowances. 9. Check logic. 10. Publish the time standard.,2002/9/26,SMT Training for Productivity,49,Time Study: Focus Points,Extend the time study Calculate average observe
43、d time. Determine performance rating. Calculate normal time: - Normal Time = average observed time x performance rating Find out frequency (how many times a task is performed within a time period). Calculate unit normal time.,2002/9/26,SMT Training for Productivity,50,Time Study: Focus Points,Determ
44、ine the number of cyclesN = number of cycles R = range of the sample of observations (in minutes) A = required precision (+/- 5% or 10%) d2 = statistical constant (3.078 for 95% confidence level) x = average time (in minutes),2002/9/26,SMT Training for Productivity,51,Time Study: Focus Points,Perfor
45、mance rating Rating is the process of adjusting the time taken by an individual operator to what could be expected from a normal operator. Four major factors: skill, consistency, working conditions, and effort. Effort is the most important. Effort is the operators speed, and is measured based on the
46、 normal operator working at 100%.,2002/9/26,SMT Training for Productivity,52,Time Study: Focus Points,Relaxation allowance It is the allowance for the periodic stops for personal needs or fatigue. Example: going to washroom; getting a drink. Contingency allowance It is a small allowance of time whic
47、h may be included in a standard time to meet expected items of delays. Occurs infrequently or irregularly. Example: interruptions by supervisors; changing materials.,2002/9/26,SMT Training for Productivity,53,Time study: Example,Example: Hand soldering for PWB of MPF82C.Identify the operations.Time
48、first 10 cycles for each operation.Calculate the required no. of cycles to be taken.,2002/9/26,SMT Training for Productivity,54,Determine No. of Cycles,Take the follows as an example, consider first 10 findings.By N = 4R2 / A2(d2)2(x)2R= (140-102) / 60 = 0.633Avg. (x) = 123.2 / 60 = 2.053For 95% con
49、fidence level, A = 0.05, d2 = 3.078N = 4 (0.633)2 / (0.05)2(3.078)2(2.053)2 = 166 additional cycles should be time taken.,2002/9/26,SMT Training for Productivity,55,Extend the Time Study,Determine performance rating for each operation.Normal time = avg. time X performance rating eg. For M15, normal time = 122.25 X 0.9 = 110.03sIdentify frequency and manpower for each operation.Unit normal time = normal time / (frequency x manpower) eg. Unit normal time = 110.03 / (8 X 1) = 13.75s,eg.,2002/9/26,SMT Training for Productivity,
