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A field study of productivity improvements in the manufacturing of circuit boards
International Journal of Industrial Ergonomics, 7 (1991) 207-215 Elsevier
207
A field study of productivity improvements in the manufacturing of circuit boards G e o r g e J. Burri, Jr. a a n d M a r t i n G. H e l a n d e r b a I B M Corporation, P.O. Box 9023, Boulder, CO 80301-9023, USA b Department of Industrial Engineering, 342 Bell Hall, State University of New York at Buffalo, N Y 14260, USA
(Received August 25, 1990; accepted in revised form February 1, 1991)
Abstract This paper describes the results of an ergonomics field study in a manufacturing environment. The study was performed primarily to improve the manufacturing yield in the production of electronic circuit board panels. A secondary objective was to improve operator comfort and job satisfaction. The project combined ergonomics and productivity assessments of several different tasks using analysis methodology such as ergonomic check lists, predetermined time and motion study operator assessment of ergonomic interventions and the rate of absenteeism. The project revealed a $1.7 million saving for modification costs of $16,000. This implies a hundred-fold rate of return of invested funds.
Relevance to industry This paper describes an ergonomics field study performed at a manufacturing plant belonging to IBM Corporation. The study was performed with the dual objective to increase productivity as well as job satisfaction. Several ergonomics improvements were undertaken. The manufacturing yield increased by 51 percent. The absenteeism decreased from 5 to 3 percent.
Keywords Ergonomics, manufacturing, quality control, illumination, training.
Introduction There is an increasing realization in industry that ergonomics is important, not only for worker's comfort, safety, and health, but also as a means to improve productivity and quality in manufacturing. Due to increased complexity in manufacturing environments, the need for ergonomic design has actually increased. Although many manufacturing tasks can be handled by computerized automated systems, the very existence of these systems makes performance of the human operator much more critical than previously. A human supervisor must be able to monitor the process using parameters for quality control and intervene when process parameters are out of bounds. The human 0169-1936/91/$03.50 © 1991 - Elsevier Science Publishers B.V.
operator must be able to assemble and monitor the quality of workpieces that are often difficult to delegate to automated systems. This study had a dual purpose. It was conceived by the medical department in the manufacturing plant, and the initial orientation was fairly traditional, concentrating on ergonomics problems such as biomechanics and materials handling. Later, management declared an interest in enhancing the productivity and quality of the manufacturing operation. Thus a very broad systems approach to ergonomics was taken. Figure 1 illustrates the major parameters that were studied and the types of dependent variables that were used to assess the problems. The production process can be illustrated using
G.J. Burri, M. G. Helander / A field study of productivity improvements
208
an environment-operator system. The environment is composed of four subsystems: equipment, process, ambient factors, and job procedures. The operator is composed of two subsystems: manufacturing/ assembly and quality control. The boxes at the bottom of the figure indicate the assessment of the dependent variables that were performed in this study. In the production environment checklists were used and measurements of ambient factors and anthropometric (workstation) measures were obtained. The other aspect related to quality control, and included information on process yield, defects and research. In addition, analyses of the productivity and reliability of machines and processes were assessed. On the operator side, much of the information was collected through interviews. This included issues such as evaluation of ergonomics improvements, job satisfaction, comfort, and absenteeism.
Description of the manufacturing environment Figure 2 shows an overview of the manufacturing environment. In this part of the plant, printed
Production Environment Equipment Machines Tools Computers Workstations Process Location Configuration Flow Material Handling Ambient Factors Lighting Noise Temperature Housekeeping Esthet cs
I
Job Procedures Training Shift Work Rest Breaks Job Rotation Assessment- Ergonomics: Checklists Measurements of Ambient Factors Anthropometric Design Assessment - Production: Production Analysis Reliability
Assessment - Ergonomics:
Job Satisfaction In uries Comfort Absentee sm
/ /
Assessment - Quality: Throughput Yield
I Defects L Rework
Fig. 1. A systems approach to assessment of ergonomics and productivity.
w
S~
NORTH
E Fig. 2. Layout of the 'Core Circuitize' manufacturing area.
circuit boards were manufactured for use in computers. The boards consisted of multiple layers of copper sheet and fiberglass with circuitry etched on the copper layers. Holes were drilled through the circuit board for insertion of components. Several of these tasks were automated or partially automated. However, there were m a n y tasks which could not be automated, including quality control of component parts and finished products. One of the primary measures of quality in manufacturing of boards is the percent of production yield. In our case, plant management had observed that the yield was consistently 5-10% below target. Most of the quality problems were described as 'internal', which means that there were defects inside the circuit board which in fact could have occurred at several different departments. It was therefore difficult to isolate any specific problems as occurring in any specific departments. For our study we decided to start the ergonomic assessment in a process area called 'core circuitize', which was located just prior to the determination of the percentage yields about half way through the manufacturing process. All together 132 individuals, mostly operators, and 59 workstations were involved.
Method of assessment Table 1 documents the types of data that were collected to assess ergonomics as well as production problems. Most information came from interviews with managers and operators, the use of a
G.J. Burri, M.G. Helander / A field study of productivity improvements
checklist and ergonomic measurements at workstations. The first step was to become familiar with the manufacturing operation. Management was interviewed with the purpose of providing insight into the types of improvements that would be feasible. Current and previous years measurements of productivity, including throughput, yield, and defects, were then analyzed to determine any specific problems that could be solved with ergonomics. This information was crucial since it addressed production questions that were of primary concern to management. In addition, statistics on injuries and absenteeism were obtained. The second step was a walk-through inspection in the plant using an ergonomics checklist. Notes were taken at individual workstations, and this information was later used as a background when interviewing operators. The third step was to interview operators and perform task analysis of the work at several different workstations. Photographs were taken to document workstations and potential ergonomic problems. A standardized questionnaire was also used and filled in by the experimenter during interviews with 28 operators. Although the tasks were different for the different operators involved, we would typically ask about issues such as possi-
209
ble ergonomic improvement of the workstation, the quality of lighting, noise and temperature, problems with housekeeping, level of comfort and convenience, operator job satisfaction, injuries and accidents. This information was then combined with our previous assessment of the workstations from the ergonomic checklists, and the measurements at the workstations. It was necessary to understand the manufacturing process in detail. To obtain this type of information, interviews were concluded with first-line supervisors concerning day-to-day operation. We were primarily interested in those aspects of production that could be enhanced by ergonomic improvements. This produced assessments of production problems at several different stages in the system. This information was crucial since it addressed those production problems that were of primary concern to management. The final step in collecting data involved field measurements of ambient environmental factors and measures of size and height of worksurfaces. The latter measures were related to anthropometric dimensions of the operators (Eastman Kodak Co., 1983). Through these discussions and measurements, data was gathered on the effectiveness of the operation. This provided the basis for a compre-
Table 1 Procedure for ergonomics and productivity assessment. Note that m a n y of the measures were collected both before and after the improvements. Source of information
Method
Data collected
1. Management
Unstructured interview Collection of statistics
Manufacturing and productivity Measures of productivity, yield, throughput, types of defects Job descriptions Rate of absenteeism Injury rate
2. Plant walk through
Ergonomics checklist
Investigator Observations on ergonomics and productivity. To be verified by operators, see 3
3. Operators
Unstructured interview Questionnaire Task analysis
Task analysis Job descriptions Ergonomics and productivity
4. First-line supervisors
Unstructured interview
Manufacturing process and technology Housekeeping
5. Field measurements
Photometer Sound level unit Workstations design measures
Measures of ambient environment Size of workstations
G.J. Burri, M.G. Helander / A fieM study of productivity improvements
210
Table 2 Example of protocol for task analysis. This illustrates ergonomic problems at the 'drills' operation. See also figure 3. Subtask
Purpose
Procedure
Feedback
Control problems
Display problems
Posture problems
Load/unload panel
Production
Move cart of panels to and from workstation Insert panel, Place on top sheet. Clip in place. Tape down. Remove on completion.
Visual kinaesthetic
Positioning tape with body extended. Arms at m a x i m u m reach,
Counting panels by hand without antilaceration gloves
Excessive reach 3 1 38" 20 times per setup
Collar on drills
Preparation
Obtain collar and correct drill size. Place in press to specified setting, Remove to WIP for machine.
Visual
Drills lack organization, Boxes underneath shelf.
Measure (1 per load)
Quality
Take panel to measurement machine. Take 13 readings using VDT. Log on machine history.
Cognitive visual
Of m a n y thousand holes only 24 are checked. Off location holes m a y not be detected.
Standing work - no chair
Visual inspection
Quality
Move panel to light table, Identify missing holes,
Visual
400 eye movements with 1" travel are required. This task should take 5 min., but inspector takes only 2 min.
Standing work - no chair
Clean drill spindle holder
Maintenance
Once per shift. Stop machine, Remove, clean and replace drill holders. Vacuum. Collect debris.
Visual
Difficult to see work area
Excessive reach 31". 38" with a lift to insert into spindle
Add coolant
Maintenance
About once per month
Visual
Check gauges
Maintenance
Back of machine. Observe proper readings.
Visual
hensive system and task assessments significant
opportunities
that revealed
for improvements.
Since most tasks were different from each other
Difficult to see control
Excessive reach 3 5 1 / 2 " to 3 6 1/2"
Difficult to read gauges
and
different
issues
were
investigated,
it is n o t
possible
to summarize
all of the data in a unified
format.
As an example
of the type of information
G.J. Burri, M.G. Helander / A field study of productivity improvements
collected table 2 shows a task analysis of the 'drills' operation which is also illustrated in figure 3.
Improvements of the manufacturing process and workstations Based on the information collected through interviews with management, supervision and operators, we identified 15 general problems. Some of these were solved through ergonomics methodology and some required redesign of the manufacturing process. In addition we identified some specific problems at individual workstations.
General problems (1) Illumination level This turned out to be the most important improvement of all. The discussion with m a n a g e r s / supervisors revealed that operators were performing relatively simple work by placing products into machines or removing them. However, interviews with the operators disclosed that they regarded themselves more as inspectors than as machine tenders, since they would inspect everything that they either placed into the machine or removed from the machine for possible defects. The ambient illumination level of 500 lux was inadequate for inspection work. Although some areas had a higher illumination level of 1000 lux, several were as low as 120 lux. It was decided to increase the illumination level to 1000 lux throughout the operation. This could be achieved by installation of fluorescent tubes, by switching on lights that had been turned off for energy conservation reasons, and by lowering light fixtures from high bay ceilings to a location closer to the workplace.
(2) Special lighting In addition, some special purpose lighting utilizing polarized light and diffused reflection was installed to make it easier to see imperfections (Eastman Kodak, 1983; Salvendy, 1982).
(3) Job rotation and rest breaks Since visual inspection tasks are usually associated with a great deal of monotony and subsequent problems in sustaining the attention throughout a work shift, it was decided to enrich
211
the task by using job rotation (Grandjean, 1985; Drury, 1981). Existing rest break patterns were evaluated, but it did not seem necessary to increase the rest breaks. The shift cross overlap was reduced from 30 to 12 minutes. The shift overlap generally fills the need of transferring information between shifts on the status of machines and processes. However, the existing amount of overlap of 30 minutes was proven to be excessive.
(4) Personal music An experiment was performed to introduce personal music in the workplace. However, the music was distracting to the task and was therefore not recommended (Eastman Kodak, 1983).
(5) Ergonomic chairs New ergonomic stools were provided that increased comfort. It also seemed to increase the productivity since operators could remain seated for longer periods of time. The stools provided here met anthropometric clean room and industrial requirements with forward tilting seat pan, adjustable arm supports, and was adopted as a company standard ( H u m a n Factors Society, 1988). For some operators, s i t / s t a n d types of chairs were also provided and recommended for occasional use.
(6) Floor treatment Soft cushioned floor mats were provided at the workstations.
(7) Operator communication and feedback In order to enhance the communication and feedback between operators on issues of quality control, pass-through windows were installed between some of the workstations. These windows did improve the communication significantly and were found to be adequate for the purpose (Bailey, 1982).
(8) Materials handling Guidelines were established with respect to permissible heights of storage racks and weight restrictions of parts. In addition, certain long-term plans were established for the purpose of replacing some of the machines with other machines that would reduce the requirement for materials handling (Drury, 1981).
(9) Automation of work Some operations were converted from manual work to r o b o t / a u t o m a t i o n . One of the jobs involved a mylar peel task where a protective tape was removed from the board. This was a highly
212
G.J. Burri, M.G. Helander / A field study ofproductwity improvements
repetitive and monotonous task and did not provide any job satisfaction. Now the operator tends a robot and performs in addition other varied and more interesting tasks while the robot peels mylar (Helander, 1983).
BEFORE \
(10) Metric and decimal measurements The conversion between metric and decimal measurements was confusing to several operators and a conversion chart was provided for each workstation.
(11) Housekeeping Through the collaboration with management, an example of good housekeeping was provided on the work floor. This enhanced the housekeeping in other areas as well. As part of the housekeeping effort, the manufacturing facility was converted to a 10,000-type clean room facility. Clean room clothing and smocks were evaluated and their use recommended.
AFTER "~
--~
(12) Noise reduction For several workstations, sound abatement covers were installed and the importance of enhancing operator communication was pointed out. This measure reduced the ambient noise level at the workstations from about 75 dBA to 60 dBA, a measure that generally enhanced the verbal communications between operators as well as their comfort (IBM, 1981).
(13) Ergonomics training An ergonomics training and awareness program was provided during departmental meetings.
Fig. 3. Before the modification of the machine the location of drill bits caused excessivereaching. After the modificationdrill bits were located close to drills, reducing reach.
Out of the 15 recommendations discussed above, all except 'personal music' were implemented.
(14) Continuous flow manufacturing Continuous flow manufacturing was implemented in several control groupings. This reduced the amount of space required for manufacturing. There are also important side benefits such as enhanced communications between nearby operators.
(15) Protective gloves For several of the operations, anti-laceration gloves are necessary to protect the operators from sharp edges and corners of the boards. At the same time, gloves may reduce the amount of tactile feedback and it may be more difficult to manipulate components (Grandjean, 1985). Several different types of gloves were evaluated and one type of glove was adopted for this operation that minimized increased grip strength necessary with gloves.
Specific problems In addition to the general problems there were specific problems at a few workstations. Since the problem solutions were different, we cannot summarize them here. As an example of the types of measures taken, figure 3 illustrates the workposture of the 'Drills' operation referred to earlier in table 2. Due to the awkward workposture the machines were replaced. The new machines significantly reduced the operator's reaching distance, which improved the workposture. Calculations using PTMS revealed a time saving at 0.0258 hours per set up. This translated into a saving of $270,000 per year. This design change was the most successful of the specific problems that were addressed.
G.J. Burri, M.G. Helander / A field study of productivity improvements 10
Results
Table 3 shows projected and actual savings. The projected savings were calculated assuming a 10% improvement in productivity, 20% fewer injuries, and a 10% improvement in the yield in the process which translated into savings at $1,699,000. As illustrated in table 3, the actual savings twelve months later were $1,639,400, which was very close to the projected estimate. The improvement in operator productivity was primarily attributed to increased comfort at the workstations. After the changes, workers spent more time at their job and absenteeism decreased from 5 to 3 percent. The amount of injury reduction ($74,000) was attributed to ergonomic factors. The improvement in yield was due to the improvements in ergonomics as well as the manufacturing process. The yield (quality) of the manufacturing was tested at several different points in the process. Figure 4 shows the improvement of yield immediately following 'core circuitize'. This quality control was not comprehensive, since the boards were not functional at this stage. The ergonomics assessment was finished by the end of February. By March 15 improved lighting had been installed which increased the illumination level by an average of 60%. Starting the second week of April training in Statistical Process Control (S.P.C.) was implemented. This training kept going for several months. In the third week of April Certified Operator Training (C.T.) was introduced with the intent of establishing job certification. Although these training courses were assumed to have favorable longterm effects, there were no immediate effects. In the first week of May, the 'knobby rollers' in one of the four conveyor sysTable 3 Projected and actual improvements in percent and dollars. Percent improvement Cost reduction Projected Yield improvement 10% Injury reduction 20% Operator productivity 10% Total
213
Actual
Projected
Actual
12%
$1,134,000
$1,175,000
21%
$
$
85~
70,000
74,000
$ 495,000 $ 390,000 $1,699,000
$1,639,000
-N~ 8 6 0
A = ErgonomicsAssessment B = Increased Lighting 60% C = S.P.C. D = C.T.
/
/ /
/
L3 4 2 0 _(3 0 <
-2
/ ~
B
Target Level
~
•- o -4 ._~
>- -6 -8
I
~'UA I
Dec Jan
I
I
Feb Mar
~
Apr
I
I
May Jun
I
Jul
I
Fig. 4. Yield after 'Core Circuitize'. Note that work in progress delayed quality control by 6 weeks.
tems were replaced by 'smooth rollers'. The impact of this change would also come later and would affect only 25% of the production. In this system, Work in Progress (WIP) from panel manufacturing until the products were tested was 6 weeks. Therefore any effect of the improved lighting could not be verified until after 6 weeks. Figure 4 shows that after 6 weeks there was an improvement in the yield from 2.8% below target to 5.8 percent above target. As explained above this quality control was not comprehensive. The final comprehensive testing of the finished, functional boards showed that the improvement sustained throughout the year correspond to an improvement of 51% in yield.
Discussion
It is difficult to quantify exactly how much of the productivity improvements should be attributed to ergonomic improvements. Many of the fine tunings of the production technology also contributed to the improvement. To isolate these effects, one should ideally perform controlled studies with two identical manufacturing organizations, where one is subjected to ergonomic redesign, and the other is used as control. Thereby it would be feasible to draw firm conclusions with respect to the impact of ergonomic redesign as opposed to other simultaneous changes in the p r o d u c t i o n process, organization, c o m p a n y climate, and so forth. Campbell and Stanley (1963)
214
G.J. Burri, M.G. Helander / A field study of productivity improvements
described several different types of experimental design that can be used in a field setting to distinguish the impact of such factors. In our case, a controlled study was not possible. There was no parallel manufacturing process utilizing the same type of machinery and the same type of tasks. Although this is unsatisfactory from a scientific perspective it is a problem that has no solution, since it is unlikely that one can find parallel organizations of this magnitude in any type of manufacturing. We were hence restricted to selective evaluation methods of the implementation without the possibility of objective comparisons. Fifteen managers and engineers were interviewed after the conclusion of this study. They agreed that approximately half of the savings could be attributed to the improved lighting conditions, while the remaining half were attributed to other process improvements. They were extremely positive about the ergonomics improvements and particularly the increased illumination levels and higher production yield. Although it is difficult to credit improvements in the productivity to any specific source, the manufacturing management at this plant agreed that ergonomic changes acted as a catalyst for improvements. Management also recognized that employee involvement was important for success. Employees were highly enthusiastic, and absenteeism was reduced from 5% to 3%. We regard this as an indication that job satisfaction improved substantially. In addition, several other manufacturing areas claimed benefits from the ergonomic redesign since it improved quality of output from CORE circuities. Suggestions for ergonomic improvements were also submitted to other departments, and several ergonomic improvements were implemented. Ergonomics in industry is nothing new (IBM, 1981; Eastman Kodak, 1983). There are many examples of successful implementation of biomechanics, materials handling and problems that concentrate on environmental factors such as noise elimination and climate. However, what is fairly new is implementation of ergonomics into the manufacturing process with the main purpose of improving productivity. This must take into consideration additional factors such as information flow and feedback between operators and machines, and requires a thorough understanding of
the manufacturing process. On the surface, it may seem that the suggested list of recommendations does nothing but address the traditional ergonomic approach to industry. However, in this application problem, it was crucial to consider the manufacturing process and types of equipment available. This requires an engineering approach to ergonomics, something that is not easy to implement unless the analyst has a background in both engineering and ergonomics. During the last ten years there has been an increasing number of human factors specialists graduating from programs of industrial engineering. Such background is desired. Medical doctors, physiotherapists, and occupational nurses would be less appropriate unless they thoroughly understand the manufacturing part of the problem. Likewise, individuals with a background in management would not have the desired prerequisites. DeKeyser (1991) pointed out that ergonomic field studies are necessary to validate methods developed in the laboratory. Field studies are particularly important for evaluation of productivity, since there are organizational and motivational parameters that cannot be replicated in the laboratory. In our case we had clear expectations, based on empirical data from laboratory studies, of what kind of ergonomic measures would be successful, and we also predicted the improvement in productivity. The problem is then to generalize from the present study to other contexts. This will require a description of the work domain, activities, decision and information processing (Rasmussen, 1991). In our case this may be fairly easy, because of the repetitive, fairly automated work performed. What is more difficult is the description of the management structure, competency of workers, and alleviation of decision roles. For this purpose we must develop a taxonomy that can be used for classification of these. Based on the enthusiasm and the encouraging results in the present study, we feel it is time to introduce ergonomic studies of productivity. With dual concerns for the operator as well as the manufacturing process, it is possible to increase productivity and quality of manufacturing as well as operator comfort and health. More research is needed to understand the potential for improvements in productivity, and to develop a task taxonomy for classification of field studies.
G.J. Burri, M.G. Helander / A field study of productivity improvements
References Bailey, R.W., 1982. Human Performance Engineering. A Guide for Systems Designers. Prentice-Hall, Inc., Englewood Cliffs, NJ. Campbell, D.T. and Stanley, J.C., 1963. Experimental and Quasi-Experimental Design. Houghton Mifflin, Boston. DeKeyser, V., 1991. Why field studies? In: M. Helander and M. Nagamachi (Eds.), Human Factors in Design for Manufacturability. Taylor & Francis, (in press), London. Drury, C.G., 1981. Human Factors in Manufacturing. International Business Machines, Training Department, Boulder, CO. Eastman Kodak Co., 1983. Ergonomic Design for People at Work, I. Van Nostrand Reinhold, New York. Grandjean, E., 1985. Fitting the Task to the Man, an Ergonomic Approach. Taylor and Francis, London,
215
Helander, M., 1983. Ergonomics in Automation. International Business Machines, Training Department, Boulder, CO. Human Factors Society, 1988. American National Standards for Human Factors Engineering of Visual Display Terminal Workstations. Santa Monica, CA. International Business Machines Corporation, 1981. IBM Ergonomics Handbook. Publication SV04-0024-01, IBM, Armonk, NY. Rasmussen, J., 1991. Use of the field studies for design at work stations for integrated manufacturing systems. In: M. Helander and M. Nagamachi (Ed.), Human Factors in Design for Manufacturability. Taylor & Francis, (in press), London. Salvendy, G. (Ed.), 1982. Handbook of Industrial Engineering. Wiley, London.
207
A field study of productivity improvements in the manufacturing of circuit boards G e o r g e J. Burri, Jr. a a n d M a r t i n G. H e l a n d e r b a I B M Corporation, P.O. Box 9023, Boulder, CO 80301-9023, USA b Department of Industrial Engineering, 342 Bell Hall, State University of New York at Buffalo, N Y 14260, USA
(Received August 25, 1990; accepted in revised form February 1, 1991)
Abstract This paper describes the results of an ergonomics field study in a manufacturing environment. The study was performed primarily to improve the manufacturing yield in the production of electronic circuit board panels. A secondary objective was to improve operator comfort and job satisfaction. The project combined ergonomics and productivity assessments of several different tasks using analysis methodology such as ergonomic check lists, predetermined time and motion study operator assessment of ergonomic interventions and the rate of absenteeism. The project revealed a $1.7 million saving for modification costs of $16,000. This implies a hundred-fold rate of return of invested funds.
Relevance to industry This paper describes an ergonomics field study performed at a manufacturing plant belonging to IBM Corporation. The study was performed with the dual objective to increase productivity as well as job satisfaction. Several ergonomics improvements were undertaken. The manufacturing yield increased by 51 percent. The absenteeism decreased from 5 to 3 percent.
Keywords Ergonomics, manufacturing, quality control, illumination, training.
Introduction There is an increasing realization in industry that ergonomics is important, not only for worker's comfort, safety, and health, but also as a means to improve productivity and quality in manufacturing. Due to increased complexity in manufacturing environments, the need for ergonomic design has actually increased. Although many manufacturing tasks can be handled by computerized automated systems, the very existence of these systems makes performance of the human operator much more critical than previously. A human supervisor must be able to monitor the process using parameters for quality control and intervene when process parameters are out of bounds. The human 0169-1936/91/$03.50 © 1991 - Elsevier Science Publishers B.V.
operator must be able to assemble and monitor the quality of workpieces that are often difficult to delegate to automated systems. This study had a dual purpose. It was conceived by the medical department in the manufacturing plant, and the initial orientation was fairly traditional, concentrating on ergonomics problems such as biomechanics and materials handling. Later, management declared an interest in enhancing the productivity and quality of the manufacturing operation. Thus a very broad systems approach to ergonomics was taken. Figure 1 illustrates the major parameters that were studied and the types of dependent variables that were used to assess the problems. The production process can be illustrated using
G.J. Burri, M. G. Helander / A field study of productivity improvements
208
an environment-operator system. The environment is composed of four subsystems: equipment, process, ambient factors, and job procedures. The operator is composed of two subsystems: manufacturing/ assembly and quality control. The boxes at the bottom of the figure indicate the assessment of the dependent variables that were performed in this study. In the production environment checklists were used and measurements of ambient factors and anthropometric (workstation) measures were obtained. The other aspect related to quality control, and included information on process yield, defects and research. In addition, analyses of the productivity and reliability of machines and processes were assessed. On the operator side, much of the information was collected through interviews. This included issues such as evaluation of ergonomics improvements, job satisfaction, comfort, and absenteeism.
Description of the manufacturing environment Figure 2 shows an overview of the manufacturing environment. In this part of the plant, printed
Production Environment Equipment Machines Tools Computers Workstations Process Location Configuration Flow Material Handling Ambient Factors Lighting Noise Temperature Housekeeping Esthet cs
I
Job Procedures Training Shift Work Rest Breaks Job Rotation Assessment- Ergonomics: Checklists Measurements of Ambient Factors Anthropometric Design Assessment - Production: Production Analysis Reliability
Assessment - Ergonomics:
Job Satisfaction In uries Comfort Absentee sm
/ /
Assessment - Quality: Throughput Yield
I Defects L Rework
Fig. 1. A systems approach to assessment of ergonomics and productivity.
w
S~
NORTH
E Fig. 2. Layout of the 'Core Circuitize' manufacturing area.
circuit boards were manufactured for use in computers. The boards consisted of multiple layers of copper sheet and fiberglass with circuitry etched on the copper layers. Holes were drilled through the circuit board for insertion of components. Several of these tasks were automated or partially automated. However, there were m a n y tasks which could not be automated, including quality control of component parts and finished products. One of the primary measures of quality in manufacturing of boards is the percent of production yield. In our case, plant management had observed that the yield was consistently 5-10% below target. Most of the quality problems were described as 'internal', which means that there were defects inside the circuit board which in fact could have occurred at several different departments. It was therefore difficult to isolate any specific problems as occurring in any specific departments. For our study we decided to start the ergonomic assessment in a process area called 'core circuitize', which was located just prior to the determination of the percentage yields about half way through the manufacturing process. All together 132 individuals, mostly operators, and 59 workstations were involved.
Method of assessment Table 1 documents the types of data that were collected to assess ergonomics as well as production problems. Most information came from interviews with managers and operators, the use of a
G.J. Burri, M.G. Helander / A field study of productivity improvements
checklist and ergonomic measurements at workstations. The first step was to become familiar with the manufacturing operation. Management was interviewed with the purpose of providing insight into the types of improvements that would be feasible. Current and previous years measurements of productivity, including throughput, yield, and defects, were then analyzed to determine any specific problems that could be solved with ergonomics. This information was crucial since it addressed production questions that were of primary concern to management. In addition, statistics on injuries and absenteeism were obtained. The second step was a walk-through inspection in the plant using an ergonomics checklist. Notes were taken at individual workstations, and this information was later used as a background when interviewing operators. The third step was to interview operators and perform task analysis of the work at several different workstations. Photographs were taken to document workstations and potential ergonomic problems. A standardized questionnaire was also used and filled in by the experimenter during interviews with 28 operators. Although the tasks were different for the different operators involved, we would typically ask about issues such as possi-
209
ble ergonomic improvement of the workstation, the quality of lighting, noise and temperature, problems with housekeeping, level of comfort and convenience, operator job satisfaction, injuries and accidents. This information was then combined with our previous assessment of the workstations from the ergonomic checklists, and the measurements at the workstations. It was necessary to understand the manufacturing process in detail. To obtain this type of information, interviews were concluded with first-line supervisors concerning day-to-day operation. We were primarily interested in those aspects of production that could be enhanced by ergonomic improvements. This produced assessments of production problems at several different stages in the system. This information was crucial since it addressed those production problems that were of primary concern to management. The final step in collecting data involved field measurements of ambient environmental factors and measures of size and height of worksurfaces. The latter measures were related to anthropometric dimensions of the operators (Eastman Kodak Co., 1983). Through these discussions and measurements, data was gathered on the effectiveness of the operation. This provided the basis for a compre-
Table 1 Procedure for ergonomics and productivity assessment. Note that m a n y of the measures were collected both before and after the improvements. Source of information
Method
Data collected
1. Management
Unstructured interview Collection of statistics
Manufacturing and productivity Measures of productivity, yield, throughput, types of defects Job descriptions Rate of absenteeism Injury rate
2. Plant walk through
Ergonomics checklist
Investigator Observations on ergonomics and productivity. To be verified by operators, see 3
3. Operators
Unstructured interview Questionnaire Task analysis
Task analysis Job descriptions Ergonomics and productivity
4. First-line supervisors
Unstructured interview
Manufacturing process and technology Housekeeping
5. Field measurements
Photometer Sound level unit Workstations design measures
Measures of ambient environment Size of workstations
G.J. Burri, M.G. Helander / A fieM study of productivity improvements
210
Table 2 Example of protocol for task analysis. This illustrates ergonomic problems at the 'drills' operation. See also figure 3. Subtask
Purpose
Procedure
Feedback
Control problems
Display problems
Posture problems
Load/unload panel
Production
Move cart of panels to and from workstation Insert panel, Place on top sheet. Clip in place. Tape down. Remove on completion.
Visual kinaesthetic
Positioning tape with body extended. Arms at m a x i m u m reach,
Counting panels by hand without antilaceration gloves
Excessive reach 3 1 38" 20 times per setup
Collar on drills
Preparation
Obtain collar and correct drill size. Place in press to specified setting, Remove to WIP for machine.
Visual
Drills lack organization, Boxes underneath shelf.
Measure (1 per load)
Quality
Take panel to measurement machine. Take 13 readings using VDT. Log on machine history.
Cognitive visual
Of m a n y thousand holes only 24 are checked. Off location holes m a y not be detected.
Standing work - no chair
Visual inspection
Quality
Move panel to light table, Identify missing holes,
Visual
400 eye movements with 1" travel are required. This task should take 5 min., but inspector takes only 2 min.
Standing work - no chair
Clean drill spindle holder
Maintenance
Once per shift. Stop machine, Remove, clean and replace drill holders. Vacuum. Collect debris.
Visual
Difficult to see work area
Excessive reach 31". 38" with a lift to insert into spindle
Add coolant
Maintenance
About once per month
Visual
Check gauges
Maintenance
Back of machine. Observe proper readings.
Visual
hensive system and task assessments significant
opportunities
that revealed
for improvements.
Since most tasks were different from each other
Difficult to see control
Excessive reach 3 5 1 / 2 " to 3 6 1/2"
Difficult to read gauges
and
different
issues
were
investigated,
it is n o t
possible
to summarize
all of the data in a unified
format.
As an example
of the type of information
G.J. Burri, M.G. Helander / A field study of productivity improvements
collected table 2 shows a task analysis of the 'drills' operation which is also illustrated in figure 3.
Improvements of the manufacturing process and workstations Based on the information collected through interviews with management, supervision and operators, we identified 15 general problems. Some of these were solved through ergonomics methodology and some required redesign of the manufacturing process. In addition we identified some specific problems at individual workstations.
General problems (1) Illumination level This turned out to be the most important improvement of all. The discussion with m a n a g e r s / supervisors revealed that operators were performing relatively simple work by placing products into machines or removing them. However, interviews with the operators disclosed that they regarded themselves more as inspectors than as machine tenders, since they would inspect everything that they either placed into the machine or removed from the machine for possible defects. The ambient illumination level of 500 lux was inadequate for inspection work. Although some areas had a higher illumination level of 1000 lux, several were as low as 120 lux. It was decided to increase the illumination level to 1000 lux throughout the operation. This could be achieved by installation of fluorescent tubes, by switching on lights that had been turned off for energy conservation reasons, and by lowering light fixtures from high bay ceilings to a location closer to the workplace.
(2) Special lighting In addition, some special purpose lighting utilizing polarized light and diffused reflection was installed to make it easier to see imperfections (Eastman Kodak, 1983; Salvendy, 1982).
(3) Job rotation and rest breaks Since visual inspection tasks are usually associated with a great deal of monotony and subsequent problems in sustaining the attention throughout a work shift, it was decided to enrich
211
the task by using job rotation (Grandjean, 1985; Drury, 1981). Existing rest break patterns were evaluated, but it did not seem necessary to increase the rest breaks. The shift cross overlap was reduced from 30 to 12 minutes. The shift overlap generally fills the need of transferring information between shifts on the status of machines and processes. However, the existing amount of overlap of 30 minutes was proven to be excessive.
(4) Personal music An experiment was performed to introduce personal music in the workplace. However, the music was distracting to the task and was therefore not recommended (Eastman Kodak, 1983).
(5) Ergonomic chairs New ergonomic stools were provided that increased comfort. It also seemed to increase the productivity since operators could remain seated for longer periods of time. The stools provided here met anthropometric clean room and industrial requirements with forward tilting seat pan, adjustable arm supports, and was adopted as a company standard ( H u m a n Factors Society, 1988). For some operators, s i t / s t a n d types of chairs were also provided and recommended for occasional use.
(6) Floor treatment Soft cushioned floor mats were provided at the workstations.
(7) Operator communication and feedback In order to enhance the communication and feedback between operators on issues of quality control, pass-through windows were installed between some of the workstations. These windows did improve the communication significantly and were found to be adequate for the purpose (Bailey, 1982).
(8) Materials handling Guidelines were established with respect to permissible heights of storage racks and weight restrictions of parts. In addition, certain long-term plans were established for the purpose of replacing some of the machines with other machines that would reduce the requirement for materials handling (Drury, 1981).
(9) Automation of work Some operations were converted from manual work to r o b o t / a u t o m a t i o n . One of the jobs involved a mylar peel task where a protective tape was removed from the board. This was a highly
212
G.J. Burri, M.G. Helander / A field study ofproductwity improvements
repetitive and monotonous task and did not provide any job satisfaction. Now the operator tends a robot and performs in addition other varied and more interesting tasks while the robot peels mylar (Helander, 1983).
BEFORE \
(10) Metric and decimal measurements The conversion between metric and decimal measurements was confusing to several operators and a conversion chart was provided for each workstation.
(11) Housekeeping Through the collaboration with management, an example of good housekeeping was provided on the work floor. This enhanced the housekeeping in other areas as well. As part of the housekeeping effort, the manufacturing facility was converted to a 10,000-type clean room facility. Clean room clothing and smocks were evaluated and their use recommended.
AFTER "~
--~
(12) Noise reduction For several workstations, sound abatement covers were installed and the importance of enhancing operator communication was pointed out. This measure reduced the ambient noise level at the workstations from about 75 dBA to 60 dBA, a measure that generally enhanced the verbal communications between operators as well as their comfort (IBM, 1981).
(13) Ergonomics training An ergonomics training and awareness program was provided during departmental meetings.
Fig. 3. Before the modification of the machine the location of drill bits caused excessivereaching. After the modificationdrill bits were located close to drills, reducing reach.
Out of the 15 recommendations discussed above, all except 'personal music' were implemented.
(14) Continuous flow manufacturing Continuous flow manufacturing was implemented in several control groupings. This reduced the amount of space required for manufacturing. There are also important side benefits such as enhanced communications between nearby operators.
(15) Protective gloves For several of the operations, anti-laceration gloves are necessary to protect the operators from sharp edges and corners of the boards. At the same time, gloves may reduce the amount of tactile feedback and it may be more difficult to manipulate components (Grandjean, 1985). Several different types of gloves were evaluated and one type of glove was adopted for this operation that minimized increased grip strength necessary with gloves.
Specific problems In addition to the general problems there were specific problems at a few workstations. Since the problem solutions were different, we cannot summarize them here. As an example of the types of measures taken, figure 3 illustrates the workposture of the 'Drills' operation referred to earlier in table 2. Due to the awkward workposture the machines were replaced. The new machines significantly reduced the operator's reaching distance, which improved the workposture. Calculations using PTMS revealed a time saving at 0.0258 hours per set up. This translated into a saving of $270,000 per year. This design change was the most successful of the specific problems that were addressed.
G.J. Burri, M.G. Helander / A field study of productivity improvements 10
Results
Table 3 shows projected and actual savings. The projected savings were calculated assuming a 10% improvement in productivity, 20% fewer injuries, and a 10% improvement in the yield in the process which translated into savings at $1,699,000. As illustrated in table 3, the actual savings twelve months later were $1,639,400, which was very close to the projected estimate. The improvement in operator productivity was primarily attributed to increased comfort at the workstations. After the changes, workers spent more time at their job and absenteeism decreased from 5 to 3 percent. The amount of injury reduction ($74,000) was attributed to ergonomic factors. The improvement in yield was due to the improvements in ergonomics as well as the manufacturing process. The yield (quality) of the manufacturing was tested at several different points in the process. Figure 4 shows the improvement of yield immediately following 'core circuitize'. This quality control was not comprehensive, since the boards were not functional at this stage. The ergonomics assessment was finished by the end of February. By March 15 improved lighting had been installed which increased the illumination level by an average of 60%. Starting the second week of April training in Statistical Process Control (S.P.C.) was implemented. This training kept going for several months. In the third week of April Certified Operator Training (C.T.) was introduced with the intent of establishing job certification. Although these training courses were assumed to have favorable longterm effects, there were no immediate effects. In the first week of May, the 'knobby rollers' in one of the four conveyor sysTable 3 Projected and actual improvements in percent and dollars. Percent improvement Cost reduction Projected Yield improvement 10% Injury reduction 20% Operator productivity 10% Total
213
Actual
Projected
Actual
12%
$1,134,000
$1,175,000
21%
$
$
85~
70,000
74,000
$ 495,000 $ 390,000 $1,699,000
$1,639,000
-N~ 8 6 0
A = ErgonomicsAssessment B = Increased Lighting 60% C = S.P.C. D = C.T.
/
/ /
/
L3 4 2 0 _(3 0 <
-2
/ ~
B
Target Level
~
•- o -4 ._~
>- -6 -8
I
~'UA I
Dec Jan
I
I
Feb Mar
~
Apr
I
I
May Jun
I
Jul
I
Fig. 4. Yield after 'Core Circuitize'. Note that work in progress delayed quality control by 6 weeks.
tems were replaced by 'smooth rollers'. The impact of this change would also come later and would affect only 25% of the production. In this system, Work in Progress (WIP) from panel manufacturing until the products were tested was 6 weeks. Therefore any effect of the improved lighting could not be verified until after 6 weeks. Figure 4 shows that after 6 weeks there was an improvement in the yield from 2.8% below target to 5.8 percent above target. As explained above this quality control was not comprehensive. The final comprehensive testing of the finished, functional boards showed that the improvement sustained throughout the year correspond to an improvement of 51% in yield.
Discussion
It is difficult to quantify exactly how much of the productivity improvements should be attributed to ergonomic improvements. Many of the fine tunings of the production technology also contributed to the improvement. To isolate these effects, one should ideally perform controlled studies with two identical manufacturing organizations, where one is subjected to ergonomic redesign, and the other is used as control. Thereby it would be feasible to draw firm conclusions with respect to the impact of ergonomic redesign as opposed to other simultaneous changes in the p r o d u c t i o n process, organization, c o m p a n y climate, and so forth. Campbell and Stanley (1963)
214
G.J. Burri, M.G. Helander / A field study of productivity improvements
described several different types of experimental design that can be used in a field setting to distinguish the impact of such factors. In our case, a controlled study was not possible. There was no parallel manufacturing process utilizing the same type of machinery and the same type of tasks. Although this is unsatisfactory from a scientific perspective it is a problem that has no solution, since it is unlikely that one can find parallel organizations of this magnitude in any type of manufacturing. We were hence restricted to selective evaluation methods of the implementation without the possibility of objective comparisons. Fifteen managers and engineers were interviewed after the conclusion of this study. They agreed that approximately half of the savings could be attributed to the improved lighting conditions, while the remaining half were attributed to other process improvements. They were extremely positive about the ergonomics improvements and particularly the increased illumination levels and higher production yield. Although it is difficult to credit improvements in the productivity to any specific source, the manufacturing management at this plant agreed that ergonomic changes acted as a catalyst for improvements. Management also recognized that employee involvement was important for success. Employees were highly enthusiastic, and absenteeism was reduced from 5% to 3%. We regard this as an indication that job satisfaction improved substantially. In addition, several other manufacturing areas claimed benefits from the ergonomic redesign since it improved quality of output from CORE circuities. Suggestions for ergonomic improvements were also submitted to other departments, and several ergonomic improvements were implemented. Ergonomics in industry is nothing new (IBM, 1981; Eastman Kodak, 1983). There are many examples of successful implementation of biomechanics, materials handling and problems that concentrate on environmental factors such as noise elimination and climate. However, what is fairly new is implementation of ergonomics into the manufacturing process with the main purpose of improving productivity. This must take into consideration additional factors such as information flow and feedback between operators and machines, and requires a thorough understanding of
the manufacturing process. On the surface, it may seem that the suggested list of recommendations does nothing but address the traditional ergonomic approach to industry. However, in this application problem, it was crucial to consider the manufacturing process and types of equipment available. This requires an engineering approach to ergonomics, something that is not easy to implement unless the analyst has a background in both engineering and ergonomics. During the last ten years there has been an increasing number of human factors specialists graduating from programs of industrial engineering. Such background is desired. Medical doctors, physiotherapists, and occupational nurses would be less appropriate unless they thoroughly understand the manufacturing part of the problem. Likewise, individuals with a background in management would not have the desired prerequisites. DeKeyser (1991) pointed out that ergonomic field studies are necessary to validate methods developed in the laboratory. Field studies are particularly important for evaluation of productivity, since there are organizational and motivational parameters that cannot be replicated in the laboratory. In our case we had clear expectations, based on empirical data from laboratory studies, of what kind of ergonomic measures would be successful, and we also predicted the improvement in productivity. The problem is then to generalize from the present study to other contexts. This will require a description of the work domain, activities, decision and information processing (Rasmussen, 1991). In our case this may be fairly easy, because of the repetitive, fairly automated work performed. What is more difficult is the description of the management structure, competency of workers, and alleviation of decision roles. For this purpose we must develop a taxonomy that can be used for classification of these. Based on the enthusiasm and the encouraging results in the present study, we feel it is time to introduce ergonomic studies of productivity. With dual concerns for the operator as well as the manufacturing process, it is possible to increase productivity and quality of manufacturing as well as operator comfort and health. More research is needed to understand the potential for improvements in productivity, and to develop a task taxonomy for classification of field studies.
G.J. Burri, M.G. Helander / A field study of productivity improvements
References Bailey, R.W., 1982. Human Performance Engineering. A Guide for Systems Designers. Prentice-Hall, Inc., Englewood Cliffs, NJ. Campbell, D.T. and Stanley, J.C., 1963. Experimental and Quasi-Experimental Design. Houghton Mifflin, Boston. DeKeyser, V., 1991. Why field studies? In: M. Helander and M. Nagamachi (Eds.), Human Factors in Design for Manufacturability. Taylor & Francis, (in press), London. Drury, C.G., 1981. Human Factors in Manufacturing. International Business Machines, Training Department, Boulder, CO. Eastman Kodak Co., 1983. Ergonomic Design for People at Work, I. Van Nostrand Reinhold, New York. Grandjean, E., 1985. Fitting the Task to the Man, an Ergonomic Approach. Taylor and Francis, London,
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Helander, M., 1983. Ergonomics in Automation. International Business Machines, Training Department, Boulder, CO. Human Factors Society, 1988. American National Standards for Human Factors Engineering of Visual Display Terminal Workstations. Santa Monica, CA. International Business Machines Corporation, 1981. IBM Ergonomics Handbook. Publication SV04-0024-01, IBM, Armonk, NY. Rasmussen, J., 1991. Use of the field studies for design at work stations for integrated manufacturing systems. In: M. Helander and M. Nagamachi (Ed.), Human Factors in Design for Manufacturability. Taylor & Francis, (in press), London. Salvendy, G. (Ed.), 1982. Handbook of Industrial Engineering. Wiley, London.