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The human factor in cellular manufacturing
JOURNAL
OF OPERATIONS
MANAGEMENT
Vol. 5. No. 2. Fchruary IYKS
The Human Factor in Cellular Manufacturing VANDRA L.HUBER* NANCY LEA HYER**
EXECUTIVE SUMMARY Recently, Group Technology (CT) as a batch manufacturing innovation has commanded much research attention and pragmatic interest. This approach to small lot production is based on identifying and exploiting similarities. By grouping items which share common traits, GT facilitates the rationalization of activities in a wide variety of functional areas including purchasing, design, and manufacturing. When GT is used in manufacturing one potential application involves the creation and operation of production cells. A production or manufacturing cell is a group of functionally dissimilar machines that are placed together and dedicated to the manufacture of a specific range of component parts. The usefulness of cellular manufacturing is demonstrated by the impressive catalog of benefits reported by its users both in the US and abroad. Reductions in work-in-process and finished goods inventories, decreases in production lead time, better delivery performance, improved product quality, and an overall increase in productivity are but a few of the benefits reportedly accruing to the use of cells. While it appears that cellular manufacturing can significantly improve the operation of batch production, an important component of the CT cellular production system has, unfortunately, been overlooked. Little study has been devoted to the human aspects of the use of production cells. The research reported in this paper attempts to fill this void by systematically examining the effect of cellular production on batch manufacturing employees. The research site was a medium size plant in which a portion of the functionally arranged facilities had recently been converted to a cellular layout. Both functional and cellular workers responded to a questionnaire designed to assess employee perceptions of their jobs, their job satisfaction, and their performance. In contrast to the findings of earlier (ethnographic) studies, cellular manufacturing employees did not perceive greater autonomy, significance, identity, or cohesiveness in their jobs than workers in traditional functional jobs. Cell workers also were as satisfied with their jobs, supervision, and advancement opportunities as non-cell workers, but were more satisfied with their pay. Supervisory ratings of performance did not vary between groups. The major contributions of this article are threefold. First, this research represents the first attempt to scientifically evaluate the human impact of cellular manufacturing. Second, in contradicting the findings of earlier descriptive studies, all of which emphasize the very positive human consequences of cellular production, the need for additional research which challenges initial intuitive presumptions is clearly indicated. Third, and perhaps most importantly, the findings of this exploratory study suggest that cellular manufacturing does not have a negative impact on worker performance, attitudes, or satisfaction. A ramification of this is that reductions in work-in-
* Cornell University, Ithaca, New York. ** University of North Carolina-Chapel
Journal of Operations Management
Hill, Chapel
Hill, North
Carolina.
213
process and finished goods inventories, decreases in production lead time, and improved overall productivity which reportedly accompany the implementation of cellular manufacturing may be achieved without any human fallout.
INTRODUCTION Recently, Group Technology (GT) as a batch manufacturing innovation has commanded much research attention and pragmatic interest [2, 5, 11, 26, 27, 28, 29, 30, 421. This multifaceted innovation has as its guiding principle a relatively simple directive: identify and exploit the similarities which exist among a set of items. Once similarities have been recognized, GT suggests that items with like characteristics be brought together into what are termed families. Common approaches are then developed for dealing with the requirements or problems shared by family members. This simple notion may be employed to rationalize a wide variety of small lot functions including design, manufacturing, and purchasing activities. When GT is used in manufacturing one potential application involves the creation and operation of manufacturing cells. A manufacturing cell is a group of functionally dissimilar machines that are physically placed together and dedicated to the manufacture of a specific range of component parts [36]. Such an arrangement differs from the traditional configuration employed in batch manufacturing. Historically, small lot (batch) manufacture has taken place in a functional layout or job shop where similar facilities are grouped together. During production, batches of component parts travel from machine center to machine center according to a specific set of required operations. The material flow which results is both complex and difficult to control, which explains why an excessively low percentage (typically not more than 5%) of the time a component spends in a job shop is devoted to actually performing manufacturing operations [42]. Queue and transport times account for the remaining 95%. With production cells the material flow is simplified since each cell deals with only a small segment of the part population. Figure 1 illustrates the difference between a job shop and cellular layout. Concerning the usefulness of GT cellular manufacturing, an impressive catalog of benefits has been reported in the (primarily British) literature [4, 5, 9, 11, 27, 30, 36, 371. Reductions in work-in-process and finished goods inventories, decreases in production lead time, and improved productivity and quality performance are frequently cited. These benefits are summarized in Table 1. The U.S. experience also confirms that cellular manufacturing can make a positive impact on firm operations. Respondents to a recent survey reported better delivery performance, shorter lead times, increased personal accountability, improved product quality, and reduced work-in-process inventories as some of the most important benefits accruing to the use of cells [26]. While it appears that cellular manufacturing can significantly improve the operation of batch production, an important component of the GT cellular production system unfortunately has been overlooked. Little study has been devoted to the human aspects of the use of production cells. Knowledge concerning these human variables is important for two reasons. First, as Hyer [25, 261 found, regardless of the type of GT application, labor-related problems and worker resistance were the most serious impediments to successful implementation of GT. Second, job redesign such as occurs with GT has been found to affect employee performance and satisfaction. Unfortunately, to the authors’ knowledge, no studies have been conducted in which the effect of cellular manufacturing
214
APES
FIGURE Functional
1a. Functional
lb. Group
1
And Group
Layout
Layout
Layout (Flow-Line
Reprinted courtesy of the Society of Manufacturing Engineers “MRP and GT Applications” by Lawrence J. Panzone.
Cell)
from SME technical
paper
MS79-967
entitled
on employees has been systematically examined. The purpose, therefore, of this study is to compare the attitudes, perceptions of job characteristics, performance, and satisfaction of employees involved in cellular manufacturing to those of employees involved in the traditional functional batch production process.
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TABLE 1 Reported Benefits Associated l l l l l l l l l l l l l l
Sources:
[9,
RESEARCH
52% 10% 30% 60% 20% 45% 80% 69% 70% 82% 42% 62% 60% 33%
with GT
reduction in new parts designed reduction in number of drawings through standardization reduction in new shop drawings reduction in industrial engineering time reduction in production floor space required reduction in scrap reduction in production and quality control costs reduction in set-up time reduction in throughput time reduction in overdue orders reduction in raw materials inventory reduction in work-in-process inventory reduction in finished goods inventory increase in employee output per unit time
I I]
BACKGROUND
In assessing the human factor in GT cellular manufacturing, it is important first to determine how various job aspects affect the behavior of individuals in organizations. While several theories have been proposed by behavioral scientists and human engineers (see [22] for reviews), the Job Characteristics Model (JCM) proposed by Hackman & Oldham is perhaps the most prominent 121, 231. Based on the earlier work of Turner & Lawrence [46] and Hackman & Lawler [20], this model is concerned with task design primarily from a motivational point of view. The model suggests that five core job characteristics lead to critical psychological states that influence the motivation to work. According to this job enrichment approach, three objective job characteristics-skill variety, task identity, and task significance-lead to experienced “meaningfulness of work.” A fourth characteristic, autonomy, is associated with experienced “responsibility for outcomes of the work.” Finally, “feedback from the job” leads to “knowledge of the actual results of the work activities.” The three psychological states, in turn, lead to positive outcomes (e.g. motivation, satisfaction and work effectiveness) in the work place. Thus, the overall potential of a job to evoke internal motivation is greatest when the job is high on feedback, autonomy, and at least one of three dimensions leading to experienced meaningfulness. According to the theory, the effectiveness of job enrichment is, however, moderated by the knowledge and skill of employees (deficiencies in either can lead to a sense of failure), their need for growth (low need will negate job enrichment), and their satisfaction with the context of the job including pay, job security, coworkers and supervision. All of these can moderate or influence the effect of job redesign. High dissatisfaction in one or more of the job conditions also may thwart job enrichment and design efforts [23]. Research indicates that job redesign, such as occurs with cellular manufacturing, can produce increased employee satisfaction and performance. For example, at Corning Glass
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APES
where teams of employees assemble hot plates, reject rates have dropped from 23 to 1% in the first six months [47]. Additionally, absenteeism fell from 8 to 1%. These desirable reductions were accompanied by an increase in productivity. Job redesign at AT & T yielded a decrease in total employees, higher productivity, and lower absenteeism [ 161. Locke reviewed a number of job redesign studies and found that in 11 of 13 cases performance improved as a consequence of altering the job configuration [32]. The changes in performance ranged from -1 to +63%, with a median of +17%. However, after studies which employed questionable research designs were eliminated, the median performance improvement was 9%. Another review found that increases in both quality and quantity performance dimensions were observed in only one of five job redesign studies [24]. Here, Heineman, Schwab, Fossum & Dyer concluded that where performance is improved, quality is the facet most likely to be positively affected. They also stressed, however, that job redesign is more likely to have a positive impact on employee satisfaction than on any aspect of employee performance. GT Cellular
Enrichment
Regarding cellular manufacturing as a job enrichment tool, greater skill variety, task identity, task significance, autonomy, and feedback all are claimed to result when cells are used in lieu of a traditional functional layout. In a functional layout, a line employee is a member of one department (e.g., the milling department) and, as such, is responsible for operating only one type of machine (e.g., milling machine). Thus, the employee performs only a certain type of operation that is one of many operations required to complete the item. As a consequence, task variety and the sense of task significance are typically low. There is generally little opportunity or need to interact with other members of a worker’s own or other departments. In addition, feedback on task performance is far from immediate. When an individual has completed the task, the item travels to another department (e.g., grinding) where it is, with few exceptions, placed at the end of the queue of items already awaiting processing in that department. Hours, days and sometimes weeks may transpire before the item reaches the head of the queue. Any feedback relating to a prior operation will thus be separated from the actual performance of that operation by a considerable period of time. Cellular manufacturing proposes an alternative worker arrangement. A group of workers is assigned to a cluster of dissimilar machines, physically placed together and capable of manufacturing a subset of the total parts spectrum. The cell workers, as a group, are responsible for a wide range of operations required by a given class of components. And individual cell workers, as a rule, perform tasks involving a variety of machines. In terms of job design, it has been argued that in such a configuration there is greater task variety. Individuals are now responsible for performing operations involving not just one, but a number of distinct machine tools. Furthermore, cell workers are able to perceive more clearly the significance of their activities: in cells, they are able to view and participate in the entire conversion process (or some significant portion of it). In many instances cell workers actually see the finished product. Because queue times are dramatically reduced, feedback concerning performance is also improved. In the event that deficiencies are discovered, the component can be returned to the answerable
Journal of Operations
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machinist in minutes or hours instead of days. A heightened sense of responsibility and accountability is said to accompany such situations in which feedback is immediate or nearly so. Research aimed at evaluating the validity of these propositions has been sparse. Ranson in his early case study of Serck Audco Valves (a British valve manufacturer) reported significant improvements in labor relations from the use of GT cells [37]. He concluded: Not only is through-put (total lead time) dramatically reduced, but there is undoubtedly far better job satisfaction since the operator is concerned with a complete article rather than an isolated part of it. Burbidge drew similar conclusions. He noted that job satisfaction is increased with the use of cells because working conditions within cells are more acceptable to human beings than the present system of batch production, namely functional layout [4]. He attributed the elevation of job satisfaction to increases in task complexity, work diversity, participation in job decision-making and a reduction in run quantity. He also noted that the parameters of job responsibility broaden for both direct and indirect workers. While the results of these two studies were positive, they are unfortunately equivocal. A drawback of both studies as well as several other studies (e.g., [ 1, 31) is that systematic data collection and analysis did not occur. Neither the workers’ reactions to cellular manufacturing nor their satisfaction was ever empirically measured. Instead, the conclusions were based upon the researchers’ reactions to and perceptions of cellular manufacturing, both of which could be biased by demand characteristics. Using questionnaires, open-ended interviews and participant observation, Fazakerley concluded that the use of cellular manufacturing itself does not create greater job flexibility [ 14, 151. Special training and union regulations may prevent operators from changing jobs. Similarly, she argued that job variety was not a product of GT cells because operators work with components which are all very similar. However, because the machines within a group are each different, workers are exposed to a wide variety of activities which create a “sense of variety.” She also concluded that, because workers were more aware of their contribution to the finished good, task significance was greater. And because work teams were utilized, task interdependence and cohesiveness were higher. Based upon these findings, Fazakerley concluded that significant social benefits are realized when a change from functional to group layout is implemented. There are, however, several criticisms of her studies. First, only brief mention is made of the methodologies employed. The number, size, and type of plants included in the survey, the number of workers and managers interviewed, and the national location of participating firms is not discussed. Nor does the author describe the specific tools used to analyze the data. Without such information, it cannot be determined whether the perceived benefits resulted from the cellular job redesign or other factors. Second, as Campbell and Cook & Campbell note, the minimum of useful scientific information requires at least one formal comparison [6, 71. Unfortunately, Fazakerley’s studies fail to juxtapose the cellular and functional employees and thus lack such a comparison. Based on the result of these studies, it must therefore be concluded that the human significance of cellular manufacturing has not been proven conclusively. However, based on the research that has been conducted, it is hypothesized that:
218
APICS
1. Cell workers will perceive that their jobs have greater ski11 variety, task significance, autonomy, and feedback than do non-cell jobs. 2. Perceived job ambiguity tional units. 3. Cell workers
and conflict
will be less in the cellular
will report greater group cohesiveness
4. Satisfaction with job, supervision, than functional, unit employees.
and
than non-cell
fellow workers
5. Because they perform more work for the same pay, dissatisfied with their pay than functional workers. 6. Supervisory workers.
reports
of performance
than
in the func-
workers.
will be higher cell workers
will be higher for cell workers
task identity,
for cellular, will be more
than for non-cell
METHOD Research Site The research site was a medium size batch manufacturing plant in the Southeast. The plant, which was part of the corporation’s trucking division, employed a total nonunionized work force of more than 100. However, because the study was concerned with the effects of cellular manufacturing and job redesign, only the fabrication department was studied. The fabrication department consisted of two units. As Figure 2a indicates, the functional unit consisted of four groups of machines. As illustrated, all milling, drilling, cutting, and special processing machines were grouped together. Workers assigned to the functional unit operated a specific piece of equipment. The same operation was performed repeatedly on parts passing through the process. Job titles for this unit included set-up technician, fabrication machine operator, material handlers, prime painter and welder. As Figure 2b depicts, the cellular manufacturing unit consisted of five cells. The cells included from three to five dissimilar machines, grouped together so a complete process could be performed on an item. Working in teams of two to three persons, cell workers operated more than one piece of equipment simultaneously. Cell units were physically separated in the plant from the functional unit. It should be noted that to prevent treatment contamination, two physically separated (different plants), and matched samples, would have been preferred [7]. However, the research site was chosen because: (1) it was the only one of the 30 known U.S. users of group technology available for study and in which manufacturing operations were arranged functionally as well as in cells; and (2) it had a sufficient number of cells and workers in cells to study empirically. Because no other data exist in which the attitudes of cell and non-cell workers have been compared, it was felt that the possibility of a smaller treatment effect due to communication between members of the cell and functional groups would have to be risked. To have confounded the treatments with differences in equipment, operations, organizational procedures, and job responsibilities between organizations would have been more unacceptable.
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FIGURE 2 Cellular (Group)
and Functional
2a. Layout of Machinery
Layout at Research
in the Functional
Site
Unit
MILLING
T T I
DRILLING
t
L-l
SPECIAL
b
2b. Layout of Machinery
1 -
I n
PROCESSES
in the Cellular Unit
I
CELL 1 I!-,
1
;--jCEE
Sample The questionnaire (described in the next section) during the final hour of one work day. Management
220
was administered at the work site provided release time from regular
APICS
duties so that all the fabrication shop employees could participate in the study. A total of 42 of 53 fabrication department employees returned usable surveys. Surveys were excluded that did not identify in which of the two work units (functional or cellular) the worker was employed. Of the employees who responded, 19 (43 percent) were assigned to the manufacturing cells on a full- or part-time basis. While employees were not randomly assigned to groups, an analysis of demographic data indicates that the two groups did not vary significantly in age, length of employment with the company, or job tenure. The subjects were overwhelming male (98%), an average of 32 years old, and had been employed by the company an average of 5.5 years. At the time of the study, the cellular units had been operational in the plant for six months. Dependent Variables The purpose of the questionnaire was to collect data that would permit the behavioral consequences of cellular manufacturing and traditional batch production to be compared. As such, measures on a variety of relevant dependent variables were gathered. In particular, the survey included series of items which focused on job characteristics, satisfaction, performance, and attitudes towards cells. Numerous items in the questionnaire dealt with a variety of job characteristics. Consistent with Schuler, Aldag & Brief [43], “role conflict” and “role ambiguity” were measured by eight items and six items respectively taken from Rizzo, House & Lirtzman [38]. Role conflict is conceptualized as the degree of incongruity of expectations associated with a role. Role ambiguity is conceptualized as the lack of clarity of role expectations and the degree of uncertainty regarding outcomes. The coefficient alpha for role conflict was .56 and for role ambiguity was .62. A four-item measure developed by DeCotiis & Koys was used to assess cohesiveness [lo]. Factor analysis yielded a single factor solution with a Cronbach alpha reliability coefficient of .72. Measures of four perceived job characteristics and two interpersonal dimensions were taken from the Job Diagnostic Survey (JDS) [22]. The job dimension perceptions gauged were skill variety, task identity, task significance, autonomy, and feedback from the job itself. The interpersonal dimensions considered were feedback from agents and dealing with others. Psychometric properties of the JDS have been examined by Dunham, Aldag & Brief [ 121. Five facets of job satisfaction were considered: satisfaction with work, supervision, fellow workers, pay, and opportunities for advancement. These were measured using the appropriate scales of the Job Description Index (JDI) [45]. Extensive research utilizing the JDI has found it to be a valid and reliable measure of job satisfaction. Its psychometric properties have been evaluated by Robinson, Althanasiou & Head [39]. Employee performance was assessed by having each subordinate’s immediate supervisor evaluate him in terms of the amount of work completed, quality of work, use of time, reject level, rework costs, absenteeism, tardiness, and overall performance. Responses were scaled from 1 (strongly disagree) to 7 (strongly agree). Cronbach alpha for the scale was .83. To determine the employees’ attitudes towards cellular manufacturing, eight single item scales were developed. Each item was scored on a 7-point Likert scale from (1) strongly disagrees to (7) strongly agree.
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RESULTS Job Characteristics The means and standard deviations for each of the perceived job characteristics are reported in Table 2. Cellular workers perceived their jobs as having greater skill variety and task significance than functional workers. However, the non-cell workers identified more with their jobs and perceived greater autonomy and feedback. The non-cell workers also reported less ambiguity, but more conflict in their jobs than cell workers. To determine if these differences in perceptions were significant, a one-way multivariate analysis of variance was used. MANOVA is the appropriate statistical method when the dependent variables are not independent 1331. An examination of the profiles formed by
Univariate
TABLE 2 Results Comparing Cellular and Functional of Job Characteristics Performance
Workers Perceptions
Group
Cellular
Functional
F
plevel
4.88” (1.25)b
4.38 (1.63)
,988
n.s.
Task Identity
4.56 (1.66)
5.00 (1.05)
,999
ns
Task Significance
5.54 (1.14)
5.46 (1.08)
2.22
n.s.
Autonomy
4.63 (1.32)
4.79 (1.14)
3.19
.08
Job Feedback
5.02 (1.30)
5.23 (1 .OO)
1.08
n.s.
Agent Feedback
4.17 (1.04)
4.88 (1.52)
4.34
.04
Dealing
5.02 (1.24)
5.22 (1.09)
1.042
n.s.
Ambiguity
4.94 (3.49)
5.32 (1.07)
,276
n.s.
Conflict
3.32 (3.21)
4.20 (1.27)
,982
ns.
5.94
5.53 (1.20)
.007
n.s.
Variable Job Dimensions Skill Variety
with Others
Cohesiveness
(.95) a Mean b Standard
222
Deviation
APICS
the mean score on each job characteristic variable showed no difference in the overall pattern of score (F = .860, p > .05). The results of the univariate comparisons were also generally nonsignificant. The comparison concerning task significance approached significance (p = .08) with cefl workers (M = 5.54) reported higher perceived task significance than non-cell workers (M = 5.46). A significant difference was found in the amount of feedback from agents received. Non-cell workers (M = 4.88) reported receiving more feedback than cell workers (M = 4.77). No other differences in self-reported job characteristics were significant. These results indicate that cell workers and non-cell workers generally perceive their jobs in a similar manner, Satisfaction Concerning job satisfaction, the MANOVA F ratio (F = 4.01, p = .Ol) was significant, indicating that the pattern of results between the cellular and functional groups differed. As Table 3 indicates, the univariate comparison for satisfaction with pay was also significant (p < .05). Cellular workers (M = 18.71) were found to be more satisfied with their pay than functional workers (M = 15.43). Functional workers (M = 17.04) were more satisfied with advancement opportunities than cellular workers (M = 15.29). However, this difference was not significant. Unexpectedly, little variability was found concerning job, fellow workers, or supervisor satisfaction. TABLE 3 Univa~ate Results of Job Satisfaction and Supervisory Performance Ratings for Cellular and Functional Workers Group Cellular N = 19
Variable Sarisfaciion Job
Functional N = 23
F
plevel
33.64a (5.2l)b
35.55 (1.61)
,314
n.s.
Supervision
46.65 (8.35)
46.07 (5.67)
,501
n.s.
Fellow Workers
39.00 (4.61)
39.64 (5.39)
.033
ns.
Pay
18.71 (3.70)
15.43 (4.18)
6.10
.02
Advancement
15.29 (4.12)
17.09 (4.23)
.476
n.s.
52.74 (7.4)
49.29 (32.66)
,450
ll.S.
Pe~or~ance
a Mean b Standard Deviation
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Performance As expected, job performance as measured by the supervisory rating was lower in the functional (M = 49.24) than in the cellular (M = 52.74) group. It was also found that the variation in performance was much less in the cellular (S.D. = 7.4) than functional (S.D. = 52.66) group. While these differences were not significant, the findings suggest that supervisors consider cell workers to be slightly better, as well as more consistent, performers than their functional counterparts. Attitudes
Towards
Cells
Concerning employee attitudes towards cellular manufacturing, no significant differences were found. As Table 4 reports, cell workers were more convinced that working in a cell required more training and more skill than were non-cell workers. They (M = 4.94) also perceived their work in the cells as being more complex than functional employees (M = 4.74) perceived it to be. Employees, regardless of their work unit, did not believe job assignments should be based on seniority. Cell workers felt more strongly that only the most skilled workers should be assigned to cells. They also were less confident that any individual could be trained to work in cells. This suggests that workers not involved in
A Comparison
TABLE 4 of the Attitudes of Cellular and Functional Towards Cellular Manufacturing Cellular
Functional
Significance
5.41= (1.5)b
4.8 (1.58)
ns
4.17
4.30 (2.05)
ns.
(2.4)
3. Only the most skilled workers should be assigned to cells
4.94 (1.39)
4.63 (1.71)
n.s.
4. Workers should be assigned cells based on seniority
to
2.88 (2.08)
3.22 (1.86)
n.s.
are paid too much
3.44 (1.78)
2.81 (1.33)
n.s.
6. Cell work is complex
4.94 (1.82)
4.78 (1.31)
n.s.
7. Working in cells is only interesting because of the computer controlled machinery
3.47 (2.09)
4.54 (1.50)
ns.
8. I’d like the whole plant to be arranged in cells
2.87 (1.54)
3.57 (1.59)
ns.
1. It takes a lot of training cell worker 2. Anyone can be trained in a cell
5. Cell workers
a Mean b Standard
224
Unit Employees
to be a
to work
Deviation
APICS
cellular manufacturing who actually perform
may perceive the tasks.
the cell jobs as being easier than do the cell workers
DISCUSSION This study was conducted to test the effects of cellular manufacturing upon worker perceptions of and affective reactions to batch manufacturing jobs. The study was designed to offset methodological problems inherent in previous ethnographic research. Contrary to these earlier studies, few significant relationships were detected concerning perceived job characteristics, satisfaction, and performance. While the results do not generally support the experimental hypotheses, they are not without merit. As Greenwald [ 171 and Griffin, Bateman & Skivington [ 191 note, the tendency to reject null findings can be very detrimental to research progress. In fact, scientific advancement is most powerfully achieved by rejecting theories. Greenwald further argues that research should be judged not on the basis of results obtained, but the adequacy of procedures and the importance of findings [ 171. The findings of the current study are important because they represent the first systematic attempt to evaluate the human effects of cellular manufacturing. Job Characteristics Despite the fact that cell workers perform more varied tasks, are responsible for more equipment, work in teams, and receive more rapid feedback, their perceptions of job characteristics did not vary radically from those of employees working in the functionallyarranged unit. The one exception, however, was feedback from agents (supervisors). Cell workers reported that they received less feedback than other workers. The difference may, in part, be due to a decreased need for external feedback among cell workers. Because the jobs are designed to provide feedback, the need for external reinforcement may be reduced. Cell workers also perceived slightly less (only marginally significant) autonomy. This result is plausible because cellular manufacturing requires teamwork. In contrast, employees in the functional units did not necessarily have to cooperate with other workers to complete job assignments. Job Characteristics
and Social Realities
In explaining the pattern of results, the recent work of Salancik & Pfeffer is particularly useful [40, 411. They argue that job characteristics are socially constructed realities; that is, perceived job characteristics may not be fixed and objective, but are defined through the set of information cues about the job which are received by employees from others. According to their model, an individual’s social environment provides cues as to what dimensions are primary in the work environment or to how valued the work is. Thus, jobs which are objectively different in the amount of skill, feedback, and autonomy that is provided, can conceivably be viewed similarly-providing the social cues indicate that they should be. For example, O’Reilly & Caldwell found that the major determinant of perceived job characteristics and job satisfaction was the information cues that the task was either enriched or not enriched [34]. Schwab & Cummings make a similar but slightly different point [44]. They argue that problems arise when perceptions are used to measure environmental characteristics
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because an individual’s judgments concerning job characteristics are only partly determined by their objective properties. While cellular manufactu~ng actually involved restructuring jobs to include greater task variety and feedback, the job changes may not have been blatant enough for inexperienced workers, not trained in job analysis, to perceive. Based on this approach, cell and non-cell workers may have perceived their jobs similarly because the organizational cues indicated that the jobs were comparable. This explanation is plausible since the cell workers received the same pay, benefits, and privileges as non-cell workers. As interviews with management revealed, when cellular manufacturing was implemented, job content was examined. However, the decision was made to place the cell jobs in the same class as the highest paid functional jobs. A new higher-paying, job category was not created. Reasons given for the decision were: 1) to prevent friction among workers; 2) to allow workers to be rotated (if necessary) in and out of the cellular units without wage adjustments; and 3) to prevent the administrative overhead of adding a new pay cl~sification level. The decision, but not the rationale, was subsequently communicated to workers. Thus, the social cues provided by top management indicated that cell and non-cell jobs were comparable. Another reason for the low variability in perceptions of job characteristics relates to the timing of the study. The research was conducted after the jobs had been redesigned and workers had been performing in the positions for six months, While perceptions may have varied initially, the passage of time may have dissipated differences, replacing them with a common assessment. Additional research is indicated in which perceptions of workers are examined at multiple time periods. Such research would indicate how or if organizationally-produced cues affect behavioral perceptions and performance. Performance Concerning performance, cell workers were rated higher by their supervisors than noncell workers. The difference, however, was nonsignificant. Less variation in performance, as indicated by the standard deviation, was found among cell workers. This result suggests that cellular manufactu~ng has a positive impact on performance, stabilizing behavior to within a restricted range. While this finding is promising, the results should be interpreted cautiously. As noted by several researchers, supervisory ratings may suffer from problems of leniency, restriction of range or halo effects, all of which can create bias [S, 18, 311. Second, as already noted, the environmental cues provided by top management indicated that the two types of jobs (cell and non-cell) were comparable. Thus, supervisors, like subordinates, may have perceived the job as similar and consequently rated individuals within a similar range. Before definitive conclusions can be made conceding the effects of cellular manufacturing on individual productivity, additional research is needed. Supervisory perceptions of task dimensions should be examined to determine if they moderate their ratings of performance. More importantly, objective measures of productivity should be included in the future. Satisfaction Cell workers were found to be as satisfied with their jobs, supervision, fellow workers and advancement opportunities as were employees assigned to the functional unit. Surprisingly, they were significantly more satisfied with their pay. This finding is interesting for several reasons. First, based on the objective characteristics of their job, they should have been dissatisfied: they performed more complex work for the same pay. Second,
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APES
according to the Job Characteristics Model, they should have been equally, but not more, satisfied than functional workers because they perceived job characteristics similarly. One explanation for this result is that employee perceptions do not affect satisfaction. It is also possible that other unmeasured variables moderate the relationship between job perceptions and satisfaction. Finally, the cellular manufacturing jobs might have offered less tangible but reinforcing rewards. For example, the opportunity to master new equipment or release from the same boring routine might have been intrinsically rewarding. If such reinforcing, but unmeasured, rewards were present they may have made pay less valued and less salient as a reward. Thus, the same amount of pay would evoke higher satisfaction among cell workers than non cell workers. Again, additional research is needed to determine if other factors not measured moderate the job design satisfaction relationship. CONCLUSIONS While additional research involving cellular manufacturing systems in other organizations is needed, the results of this exploratory study are important. First, the study provided the first empirical test of the proposition that cellular manufacturing has human, as well as manufacturing process, payoffs. It was found that cellular manufacturing neither increases nor decreases employee performance or satisfaction over that achieved in the functionally-designed unit. On first blush, this conclusion may seem disheartening, indicating a less than desirable condition. In reality, the results are very encouraging. They suggest that cellular manufacturing may be implemented without any human fallout. A ramification of this is that reductions in work-in-process and finished goods inventories, decreases in production lead time, and improved overall productivity which reportedly accompany the implementation of cellular manufacturing may be achieved without any negative effects on employees. Additional research should, however, be conducted to determine if the findings of this study generalize to other work situations. REFERENCES 1. Astrop, A.W., “Group Technology as a Way of Life,” Machinery and Production Engineering, 1975, 126 (3241) 42-45. 2. Beeby, W.D. and A. Thompson, “A Broader View of Group Technology,” Computers and Industrial Engineering, 1979, 3(4), 289-3 12. 3. Bim, S.A., “Improving Motivation Through Job Design in the GT Workcell,” SME Technical Paper MS78-976, Computer and Automated Systems Association of SME, 1978, Dearborn, MI. 4. Burbidge, J.L., The Introduction of Group TechnoIogy. London: Heineman, 1975. 5. Burbidge, J.L., Group Technology in the Engineering Industry. London: Mechanical Engineering Publications LTD., 1979. 6. Campbell, D., “Factors Relevant to the Validity of Experiments in Social Settings,” Psychological Bulletin, 1957, 54, 297-3 12. 7. Cook, T.D. and D.T. Campbell, Quasi Experimentation: Design and Analysis Issues for Field Setting. Chicago: Rand McNally Co., 1979.
Journal of Operations Management
8. Cummings, L.L. and D.P. Schwab, Performance in Organizations: Determinants and Appraisal. Glenview, IL: Scott Foresman, 1973. 9. Dale, B. and P. Willey, “The Need to Predict the Potential for Group Technology in Manufacture,” Machinery and Production Engineering, 1977, 130, 9-15. 10. DeCotiis, T.A. and D.J. Koys, “The Identification and Measurement of the Dimensions of Organizational Climate,” Academy of Management Proceeding, 1980, 171-175. 1I. DeVries, M., et al., Group Technology: An Overview and Bibliography. Cincinnati, Ohio: The Machinability Data Center, 1976. 12. Dunham, R.B., R.J. Alday and A.P. Brief, “Dimensionality of task design as measured by the job diagnostic survey,” Academy of Management Journal, 1977, 20, 209-223. 13. Farh, J.L. and P.M. Podsakoff, “The Job Characteristics Model: A Critical Review,” Working paper, 1982, Indiana University.
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Research, 1976, 14(l), 123-134. 16. Ford, R.N., “Job Enrichment Lessons from AT&T,” Harvard Business Review, February, 1973, 51, 96-106. A.G., “Consequences 17. Greenwald, of Prejudice Against the Null Hypothesis,” Psychological Bul-
letin, 1975, 82, l-20. 18. Griffin, R.W., A. Welsh and G. Moorhead, “Perceived Task Characteristics and Employee Performance: A Literature Review,” Academy of Man-
agement Review, 1981, 6, 655-664. 19. Griffin, R.W., T.S. Bateman, and J. Skivington, “Social Cues as Information Sources: Extensions and Refinements,” O&e of Naval Research Technical Report (TR-ONR-D6-03) 1983. J.R. and E.E. Lawler, “Employee Re20. Hackman, actions to Job Characteristics,” Journal of Applied
Psychology Monograph, 197 1, 55, 259-286. 21. Hackman, J.R. and G.R. Oldham, “Development of Job Diagnostic Survey,” Journal of Applied Psychology, 1975, 60, 159-170. J.R. and G.R. Oldham, “Motivation 22. Hackman, Through the Design of Work: Test of a Theory,”
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H.G., D.P. Schwab, J.A. Fossum, and 24. Heineman, L.D. Dyer, Personnel/Human Resource Management. Richard D. Irwin: Homewood, IL, 1983. 25. Hyer, N., Group Technology: Development, D$ii-
sion and Application in the U.S. and International Context. Unpublished Ph.D. Dissertation, 1982, Indiana
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agement, 1984, 4(3), 183-202. 27. Hyer, N., ed., Group Technology at Work. Dearof Manufacturing
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“MRP/GT: A 28. Hyer, N. and U. Wemmerliiv, Framework for Production Planning and Control of Cellular Manufacturing,” Design Sciences, 1982, 13(4), 68 I-70 I. “Group Technology 29. Hyer, N. and U. Wemmerlov, and Productivity,” Harvard Business Review, 1984, in press. 30. Jackson, D., The Cell System of Production. London: Business Books, 1980. 31. Klimoski, R.J. and M. London, “Role of the Rater
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32. Locke, E.A., D.B. Feren, V.M. McCaIeb, K.N. Shaw, and A.T. Denny, “The Relative Effectiveness of Four Methods of Motivating Employee Perforand mance,” in K.D. Duncan, M.M. Gruenberg D. Walles (Eds.) Changes in Working It@. New York: John Wiley & Sons, 1980, 363-388. 33. Morrison, D.F., Multivariate Statistical Methods. New York: McGraw-Hill, 1967. Fit: Implications for 34. O’Reilly, C., “Personality-Job Individual Attitudes and Performance,” Orgnizational Behavior and Human Performance, 1977, 18, 36-46. 35. O’Reilly, C.A. and D.F. Caldwell, “Informational Influences as a Determinant of Perceived Task Characteristics and Job Satisfaction,” Journal of Applied Psychology, 1979, 64, 157-165. 36. Pullen, R., “A Survey of Cellular Manufacturing Cells,” The Production Engineer, 1977, 55(9), 45 l-
454. 37. Ransom, G., Group Technology. London: McGrawHill, 1972. 38. Rizzo, J.R., R.J. House and S.J. Lirtzman, “Role Conflict and Ambiguity in Complex Organizations,” Administrative Science Quarterly, 1970, 15, 150-163. and K.B. Head, 39. Robinson, J.P., R. Athanasiou
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ministrative Science Quarterly, 1977, 22, 427-456. 41. Salancik, G.R. and J. Pfeffer, “A Social Information Processing Approach to Job Attitudes and Task Design, Administrative Science Quarterly, 1978,
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nizational Behavior and Human Performance, 1977, 20, 11 l-128. “Impact of 44. Schwab, D.P. and L.L. Cummings, Task Scope on Employee Productivity: An Evaluation Using Expectancy Theory,” Academy of
Management Review, 1976, 1, 23-35. 45. Smith, P., L. Kendall and C. Hulin, The Measurement of Satisfaction in Work and Retirement. Chicago:
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46. Turner, A.N. and R.D. Lawrence, and the Worker. Boston: Harvard
Industrial Jobs
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APES
OF OPERATIONS
MANAGEMENT
Vol. 5. No. 2. Fchruary IYKS
The Human Factor in Cellular Manufacturing VANDRA L.HUBER* NANCY LEA HYER**
EXECUTIVE SUMMARY Recently, Group Technology (CT) as a batch manufacturing innovation has commanded much research attention and pragmatic interest. This approach to small lot production is based on identifying and exploiting similarities. By grouping items which share common traits, GT facilitates the rationalization of activities in a wide variety of functional areas including purchasing, design, and manufacturing. When GT is used in manufacturing one potential application involves the creation and operation of production cells. A production or manufacturing cell is a group of functionally dissimilar machines that are placed together and dedicated to the manufacture of a specific range of component parts. The usefulness of cellular manufacturing is demonstrated by the impressive catalog of benefits reported by its users both in the US and abroad. Reductions in work-in-process and finished goods inventories, decreases in production lead time, better delivery performance, improved product quality, and an overall increase in productivity are but a few of the benefits reportedly accruing to the use of cells. While it appears that cellular manufacturing can significantly improve the operation of batch production, an important component of the CT cellular production system has, unfortunately, been overlooked. Little study has been devoted to the human aspects of the use of production cells. The research reported in this paper attempts to fill this void by systematically examining the effect of cellular production on batch manufacturing employees. The research site was a medium size plant in which a portion of the functionally arranged facilities had recently been converted to a cellular layout. Both functional and cellular workers responded to a questionnaire designed to assess employee perceptions of their jobs, their job satisfaction, and their performance. In contrast to the findings of earlier (ethnographic) studies, cellular manufacturing employees did not perceive greater autonomy, significance, identity, or cohesiveness in their jobs than workers in traditional functional jobs. Cell workers also were as satisfied with their jobs, supervision, and advancement opportunities as non-cell workers, but were more satisfied with their pay. Supervisory ratings of performance did not vary between groups. The major contributions of this article are threefold. First, this research represents the first attempt to scientifically evaluate the human impact of cellular manufacturing. Second, in contradicting the findings of earlier descriptive studies, all of which emphasize the very positive human consequences of cellular production, the need for additional research which challenges initial intuitive presumptions is clearly indicated. Third, and perhaps most importantly, the findings of this exploratory study suggest that cellular manufacturing does not have a negative impact on worker performance, attitudes, or satisfaction. A ramification of this is that reductions in work-in-
* Cornell University, Ithaca, New York. ** University of North Carolina-Chapel
Journal of Operations Management
Hill, Chapel
Hill, North
Carolina.
213
process and finished goods inventories, decreases in production lead time, and improved overall productivity which reportedly accompany the implementation of cellular manufacturing may be achieved without any human fallout.
INTRODUCTION Recently, Group Technology (GT) as a batch manufacturing innovation has commanded much research attention and pragmatic interest [2, 5, 11, 26, 27, 28, 29, 30, 421. This multifaceted innovation has as its guiding principle a relatively simple directive: identify and exploit the similarities which exist among a set of items. Once similarities have been recognized, GT suggests that items with like characteristics be brought together into what are termed families. Common approaches are then developed for dealing with the requirements or problems shared by family members. This simple notion may be employed to rationalize a wide variety of small lot functions including design, manufacturing, and purchasing activities. When GT is used in manufacturing one potential application involves the creation and operation of manufacturing cells. A manufacturing cell is a group of functionally dissimilar machines that are physically placed together and dedicated to the manufacture of a specific range of component parts [36]. Such an arrangement differs from the traditional configuration employed in batch manufacturing. Historically, small lot (batch) manufacture has taken place in a functional layout or job shop where similar facilities are grouped together. During production, batches of component parts travel from machine center to machine center according to a specific set of required operations. The material flow which results is both complex and difficult to control, which explains why an excessively low percentage (typically not more than 5%) of the time a component spends in a job shop is devoted to actually performing manufacturing operations [42]. Queue and transport times account for the remaining 95%. With production cells the material flow is simplified since each cell deals with only a small segment of the part population. Figure 1 illustrates the difference between a job shop and cellular layout. Concerning the usefulness of GT cellular manufacturing, an impressive catalog of benefits has been reported in the (primarily British) literature [4, 5, 9, 11, 27, 30, 36, 371. Reductions in work-in-process and finished goods inventories, decreases in production lead time, and improved productivity and quality performance are frequently cited. These benefits are summarized in Table 1. The U.S. experience also confirms that cellular manufacturing can make a positive impact on firm operations. Respondents to a recent survey reported better delivery performance, shorter lead times, increased personal accountability, improved product quality, and reduced work-in-process inventories as some of the most important benefits accruing to the use of cells [26]. While it appears that cellular manufacturing can significantly improve the operation of batch production, an important component of the GT cellular production system unfortunately has been overlooked. Little study has been devoted to the human aspects of the use of production cells. Knowledge concerning these human variables is important for two reasons. First, as Hyer [25, 261 found, regardless of the type of GT application, labor-related problems and worker resistance were the most serious impediments to successful implementation of GT. Second, job redesign such as occurs with GT has been found to affect employee performance and satisfaction. Unfortunately, to the authors’ knowledge, no studies have been conducted in which the effect of cellular manufacturing
214
APES
FIGURE Functional
1a. Functional
lb. Group
1
And Group
Layout
Layout
Layout (Flow-Line
Reprinted courtesy of the Society of Manufacturing Engineers “MRP and GT Applications” by Lawrence J. Panzone.
Cell)
from SME technical
paper
MS79-967
entitled
on employees has been systematically examined. The purpose, therefore, of this study is to compare the attitudes, perceptions of job characteristics, performance, and satisfaction of employees involved in cellular manufacturing to those of employees involved in the traditional functional batch production process.
Journal of Operations
Management
215
TABLE 1 Reported Benefits Associated l l l l l l l l l l l l l l
Sources:
[9,
RESEARCH
52% 10% 30% 60% 20% 45% 80% 69% 70% 82% 42% 62% 60% 33%
with GT
reduction in new parts designed reduction in number of drawings through standardization reduction in new shop drawings reduction in industrial engineering time reduction in production floor space required reduction in scrap reduction in production and quality control costs reduction in set-up time reduction in throughput time reduction in overdue orders reduction in raw materials inventory reduction in work-in-process inventory reduction in finished goods inventory increase in employee output per unit time
I I]
BACKGROUND
In assessing the human factor in GT cellular manufacturing, it is important first to determine how various job aspects affect the behavior of individuals in organizations. While several theories have been proposed by behavioral scientists and human engineers (see [22] for reviews), the Job Characteristics Model (JCM) proposed by Hackman & Oldham is perhaps the most prominent 121, 231. Based on the earlier work of Turner & Lawrence [46] and Hackman & Lawler [20], this model is concerned with task design primarily from a motivational point of view. The model suggests that five core job characteristics lead to critical psychological states that influence the motivation to work. According to this job enrichment approach, three objective job characteristics-skill variety, task identity, and task significance-lead to experienced “meaningfulness of work.” A fourth characteristic, autonomy, is associated with experienced “responsibility for outcomes of the work.” Finally, “feedback from the job” leads to “knowledge of the actual results of the work activities.” The three psychological states, in turn, lead to positive outcomes (e.g. motivation, satisfaction and work effectiveness) in the work place. Thus, the overall potential of a job to evoke internal motivation is greatest when the job is high on feedback, autonomy, and at least one of three dimensions leading to experienced meaningfulness. According to the theory, the effectiveness of job enrichment is, however, moderated by the knowledge and skill of employees (deficiencies in either can lead to a sense of failure), their need for growth (low need will negate job enrichment), and their satisfaction with the context of the job including pay, job security, coworkers and supervision. All of these can moderate or influence the effect of job redesign. High dissatisfaction in one or more of the job conditions also may thwart job enrichment and design efforts [23]. Research indicates that job redesign, such as occurs with cellular manufacturing, can produce increased employee satisfaction and performance. For example, at Corning Glass
216
APES
where teams of employees assemble hot plates, reject rates have dropped from 23 to 1% in the first six months [47]. Additionally, absenteeism fell from 8 to 1%. These desirable reductions were accompanied by an increase in productivity. Job redesign at AT & T yielded a decrease in total employees, higher productivity, and lower absenteeism [ 161. Locke reviewed a number of job redesign studies and found that in 11 of 13 cases performance improved as a consequence of altering the job configuration [32]. The changes in performance ranged from -1 to +63%, with a median of +17%. However, after studies which employed questionable research designs were eliminated, the median performance improvement was 9%. Another review found that increases in both quality and quantity performance dimensions were observed in only one of five job redesign studies [24]. Here, Heineman, Schwab, Fossum & Dyer concluded that where performance is improved, quality is the facet most likely to be positively affected. They also stressed, however, that job redesign is more likely to have a positive impact on employee satisfaction than on any aspect of employee performance. GT Cellular
Enrichment
Regarding cellular manufacturing as a job enrichment tool, greater skill variety, task identity, task significance, autonomy, and feedback all are claimed to result when cells are used in lieu of a traditional functional layout. In a functional layout, a line employee is a member of one department (e.g., the milling department) and, as such, is responsible for operating only one type of machine (e.g., milling machine). Thus, the employee performs only a certain type of operation that is one of many operations required to complete the item. As a consequence, task variety and the sense of task significance are typically low. There is generally little opportunity or need to interact with other members of a worker’s own or other departments. In addition, feedback on task performance is far from immediate. When an individual has completed the task, the item travels to another department (e.g., grinding) where it is, with few exceptions, placed at the end of the queue of items already awaiting processing in that department. Hours, days and sometimes weeks may transpire before the item reaches the head of the queue. Any feedback relating to a prior operation will thus be separated from the actual performance of that operation by a considerable period of time. Cellular manufacturing proposes an alternative worker arrangement. A group of workers is assigned to a cluster of dissimilar machines, physically placed together and capable of manufacturing a subset of the total parts spectrum. The cell workers, as a group, are responsible for a wide range of operations required by a given class of components. And individual cell workers, as a rule, perform tasks involving a variety of machines. In terms of job design, it has been argued that in such a configuration there is greater task variety. Individuals are now responsible for performing operations involving not just one, but a number of distinct machine tools. Furthermore, cell workers are able to perceive more clearly the significance of their activities: in cells, they are able to view and participate in the entire conversion process (or some significant portion of it). In many instances cell workers actually see the finished product. Because queue times are dramatically reduced, feedback concerning performance is also improved. In the event that deficiencies are discovered, the component can be returned to the answerable
Journal of Operations
Management
217
machinist in minutes or hours instead of days. A heightened sense of responsibility and accountability is said to accompany such situations in which feedback is immediate or nearly so. Research aimed at evaluating the validity of these propositions has been sparse. Ranson in his early case study of Serck Audco Valves (a British valve manufacturer) reported significant improvements in labor relations from the use of GT cells [37]. He concluded: Not only is through-put (total lead time) dramatically reduced, but there is undoubtedly far better job satisfaction since the operator is concerned with a complete article rather than an isolated part of it. Burbidge drew similar conclusions. He noted that job satisfaction is increased with the use of cells because working conditions within cells are more acceptable to human beings than the present system of batch production, namely functional layout [4]. He attributed the elevation of job satisfaction to increases in task complexity, work diversity, participation in job decision-making and a reduction in run quantity. He also noted that the parameters of job responsibility broaden for both direct and indirect workers. While the results of these two studies were positive, they are unfortunately equivocal. A drawback of both studies as well as several other studies (e.g., [ 1, 31) is that systematic data collection and analysis did not occur. Neither the workers’ reactions to cellular manufacturing nor their satisfaction was ever empirically measured. Instead, the conclusions were based upon the researchers’ reactions to and perceptions of cellular manufacturing, both of which could be biased by demand characteristics. Using questionnaires, open-ended interviews and participant observation, Fazakerley concluded that the use of cellular manufacturing itself does not create greater job flexibility [ 14, 151. Special training and union regulations may prevent operators from changing jobs. Similarly, she argued that job variety was not a product of GT cells because operators work with components which are all very similar. However, because the machines within a group are each different, workers are exposed to a wide variety of activities which create a “sense of variety.” She also concluded that, because workers were more aware of their contribution to the finished good, task significance was greater. And because work teams were utilized, task interdependence and cohesiveness were higher. Based upon these findings, Fazakerley concluded that significant social benefits are realized when a change from functional to group layout is implemented. There are, however, several criticisms of her studies. First, only brief mention is made of the methodologies employed. The number, size, and type of plants included in the survey, the number of workers and managers interviewed, and the national location of participating firms is not discussed. Nor does the author describe the specific tools used to analyze the data. Without such information, it cannot be determined whether the perceived benefits resulted from the cellular job redesign or other factors. Second, as Campbell and Cook & Campbell note, the minimum of useful scientific information requires at least one formal comparison [6, 71. Unfortunately, Fazakerley’s studies fail to juxtapose the cellular and functional employees and thus lack such a comparison. Based on the result of these studies, it must therefore be concluded that the human significance of cellular manufacturing has not been proven conclusively. However, based on the research that has been conducted, it is hypothesized that:
218
APICS
1. Cell workers will perceive that their jobs have greater ski11 variety, task significance, autonomy, and feedback than do non-cell jobs. 2. Perceived job ambiguity tional units. 3. Cell workers
and conflict
will be less in the cellular
will report greater group cohesiveness
4. Satisfaction with job, supervision, than functional, unit employees.
and
than non-cell
fellow workers
5. Because they perform more work for the same pay, dissatisfied with their pay than functional workers. 6. Supervisory workers.
reports
of performance
than
in the func-
workers.
will be higher cell workers
will be higher for cell workers
task identity,
for cellular, will be more
than for non-cell
METHOD Research Site The research site was a medium size batch manufacturing plant in the Southeast. The plant, which was part of the corporation’s trucking division, employed a total nonunionized work force of more than 100. However, because the study was concerned with the effects of cellular manufacturing and job redesign, only the fabrication department was studied. The fabrication department consisted of two units. As Figure 2a indicates, the functional unit consisted of four groups of machines. As illustrated, all milling, drilling, cutting, and special processing machines were grouped together. Workers assigned to the functional unit operated a specific piece of equipment. The same operation was performed repeatedly on parts passing through the process. Job titles for this unit included set-up technician, fabrication machine operator, material handlers, prime painter and welder. As Figure 2b depicts, the cellular manufacturing unit consisted of five cells. The cells included from three to five dissimilar machines, grouped together so a complete process could be performed on an item. Working in teams of two to three persons, cell workers operated more than one piece of equipment simultaneously. Cell units were physically separated in the plant from the functional unit. It should be noted that to prevent treatment contamination, two physically separated (different plants), and matched samples, would have been preferred [7]. However, the research site was chosen because: (1) it was the only one of the 30 known U.S. users of group technology available for study and in which manufacturing operations were arranged functionally as well as in cells; and (2) it had a sufficient number of cells and workers in cells to study empirically. Because no other data exist in which the attitudes of cell and non-cell workers have been compared, it was felt that the possibility of a smaller treatment effect due to communication between members of the cell and functional groups would have to be risked. To have confounded the treatments with differences in equipment, operations, organizational procedures, and job responsibilities between organizations would have been more unacceptable.
Journal of Operations Management
219
FIGURE 2 Cellular (Group)
and Functional
2a. Layout of Machinery
Layout at Research
in the Functional
Site
Unit
MILLING
T T I
DRILLING
t
L-l
SPECIAL
b
2b. Layout of Machinery
1 -
I n
PROCESSES
in the Cellular Unit
I
CELL 1 I!-,
1
;--jCEE
Sample The questionnaire (described in the next section) during the final hour of one work day. Management
220
was administered at the work site provided release time from regular
APICS
duties so that all the fabrication shop employees could participate in the study. A total of 42 of 53 fabrication department employees returned usable surveys. Surveys were excluded that did not identify in which of the two work units (functional or cellular) the worker was employed. Of the employees who responded, 19 (43 percent) were assigned to the manufacturing cells on a full- or part-time basis. While employees were not randomly assigned to groups, an analysis of demographic data indicates that the two groups did not vary significantly in age, length of employment with the company, or job tenure. The subjects were overwhelming male (98%), an average of 32 years old, and had been employed by the company an average of 5.5 years. At the time of the study, the cellular units had been operational in the plant for six months. Dependent Variables The purpose of the questionnaire was to collect data that would permit the behavioral consequences of cellular manufacturing and traditional batch production to be compared. As such, measures on a variety of relevant dependent variables were gathered. In particular, the survey included series of items which focused on job characteristics, satisfaction, performance, and attitudes towards cells. Numerous items in the questionnaire dealt with a variety of job characteristics. Consistent with Schuler, Aldag & Brief [43], “role conflict” and “role ambiguity” were measured by eight items and six items respectively taken from Rizzo, House & Lirtzman [38]. Role conflict is conceptualized as the degree of incongruity of expectations associated with a role. Role ambiguity is conceptualized as the lack of clarity of role expectations and the degree of uncertainty regarding outcomes. The coefficient alpha for role conflict was .56 and for role ambiguity was .62. A four-item measure developed by DeCotiis & Koys was used to assess cohesiveness [lo]. Factor analysis yielded a single factor solution with a Cronbach alpha reliability coefficient of .72. Measures of four perceived job characteristics and two interpersonal dimensions were taken from the Job Diagnostic Survey (JDS) [22]. The job dimension perceptions gauged were skill variety, task identity, task significance, autonomy, and feedback from the job itself. The interpersonal dimensions considered were feedback from agents and dealing with others. Psychometric properties of the JDS have been examined by Dunham, Aldag & Brief [ 121. Five facets of job satisfaction were considered: satisfaction with work, supervision, fellow workers, pay, and opportunities for advancement. These were measured using the appropriate scales of the Job Description Index (JDI) [45]. Extensive research utilizing the JDI has found it to be a valid and reliable measure of job satisfaction. Its psychometric properties have been evaluated by Robinson, Althanasiou & Head [39]. Employee performance was assessed by having each subordinate’s immediate supervisor evaluate him in terms of the amount of work completed, quality of work, use of time, reject level, rework costs, absenteeism, tardiness, and overall performance. Responses were scaled from 1 (strongly disagree) to 7 (strongly agree). Cronbach alpha for the scale was .83. To determine the employees’ attitudes towards cellular manufacturing, eight single item scales were developed. Each item was scored on a 7-point Likert scale from (1) strongly disagrees to (7) strongly agree.
Journal of Operations
Management
221
RESULTS Job Characteristics The means and standard deviations for each of the perceived job characteristics are reported in Table 2. Cellular workers perceived their jobs as having greater skill variety and task significance than functional workers. However, the non-cell workers identified more with their jobs and perceived greater autonomy and feedback. The non-cell workers also reported less ambiguity, but more conflict in their jobs than cell workers. To determine if these differences in perceptions were significant, a one-way multivariate analysis of variance was used. MANOVA is the appropriate statistical method when the dependent variables are not independent 1331. An examination of the profiles formed by
Univariate
TABLE 2 Results Comparing Cellular and Functional of Job Characteristics Performance
Workers Perceptions
Group
Cellular
Functional
F
plevel
4.88” (1.25)b
4.38 (1.63)
,988
n.s.
Task Identity
4.56 (1.66)
5.00 (1.05)
,999
ns
Task Significance
5.54 (1.14)
5.46 (1.08)
2.22
n.s.
Autonomy
4.63 (1.32)
4.79 (1.14)
3.19
.08
Job Feedback
5.02 (1.30)
5.23 (1 .OO)
1.08
n.s.
Agent Feedback
4.17 (1.04)
4.88 (1.52)
4.34
.04
Dealing
5.02 (1.24)
5.22 (1.09)
1.042
n.s.
Ambiguity
4.94 (3.49)
5.32 (1.07)
,276
n.s.
Conflict
3.32 (3.21)
4.20 (1.27)
,982
ns.
5.94
5.53 (1.20)
.007
n.s.
Variable Job Dimensions Skill Variety
with Others
Cohesiveness
(.95) a Mean b Standard
222
Deviation
APICS
the mean score on each job characteristic variable showed no difference in the overall pattern of score (F = .860, p > .05). The results of the univariate comparisons were also generally nonsignificant. The comparison concerning task significance approached significance (p = .08) with cefl workers (M = 5.54) reported higher perceived task significance than non-cell workers (M = 5.46). A significant difference was found in the amount of feedback from agents received. Non-cell workers (M = 4.88) reported receiving more feedback than cell workers (M = 4.77). No other differences in self-reported job characteristics were significant. These results indicate that cell workers and non-cell workers generally perceive their jobs in a similar manner, Satisfaction Concerning job satisfaction, the MANOVA F ratio (F = 4.01, p = .Ol) was significant, indicating that the pattern of results between the cellular and functional groups differed. As Table 3 indicates, the univariate comparison for satisfaction with pay was also significant (p < .05). Cellular workers (M = 18.71) were found to be more satisfied with their pay than functional workers (M = 15.43). Functional workers (M = 17.04) were more satisfied with advancement opportunities than cellular workers (M = 15.29). However, this difference was not significant. Unexpectedly, little variability was found concerning job, fellow workers, or supervisor satisfaction. TABLE 3 Univa~ate Results of Job Satisfaction and Supervisory Performance Ratings for Cellular and Functional Workers Group Cellular N = 19
Variable Sarisfaciion Job
Functional N = 23
F
plevel
33.64a (5.2l)b
35.55 (1.61)
,314
n.s.
Supervision
46.65 (8.35)
46.07 (5.67)
,501
n.s.
Fellow Workers
39.00 (4.61)
39.64 (5.39)
.033
ns.
Pay
18.71 (3.70)
15.43 (4.18)
6.10
.02
Advancement
15.29 (4.12)
17.09 (4.23)
.476
n.s.
52.74 (7.4)
49.29 (32.66)
,450
ll.S.
Pe~or~ance
a Mean b Standard Deviation
Journal of Operations
Management
223
Performance As expected, job performance as measured by the supervisory rating was lower in the functional (M = 49.24) than in the cellular (M = 52.74) group. It was also found that the variation in performance was much less in the cellular (S.D. = 7.4) than functional (S.D. = 52.66) group. While these differences were not significant, the findings suggest that supervisors consider cell workers to be slightly better, as well as more consistent, performers than their functional counterparts. Attitudes
Towards
Cells
Concerning employee attitudes towards cellular manufacturing, no significant differences were found. As Table 4 reports, cell workers were more convinced that working in a cell required more training and more skill than were non-cell workers. They (M = 4.94) also perceived their work in the cells as being more complex than functional employees (M = 4.74) perceived it to be. Employees, regardless of their work unit, did not believe job assignments should be based on seniority. Cell workers felt more strongly that only the most skilled workers should be assigned to cells. They also were less confident that any individual could be trained to work in cells. This suggests that workers not involved in
A Comparison
TABLE 4 of the Attitudes of Cellular and Functional Towards Cellular Manufacturing Cellular
Functional
Significance
5.41= (1.5)b
4.8 (1.58)
ns
4.17
4.30 (2.05)
ns.
(2.4)
3. Only the most skilled workers should be assigned to cells
4.94 (1.39)
4.63 (1.71)
n.s.
4. Workers should be assigned cells based on seniority
to
2.88 (2.08)
3.22 (1.86)
n.s.
are paid too much
3.44 (1.78)
2.81 (1.33)
n.s.
6. Cell work is complex
4.94 (1.82)
4.78 (1.31)
n.s.
7. Working in cells is only interesting because of the computer controlled machinery
3.47 (2.09)
4.54 (1.50)
ns.
8. I’d like the whole plant to be arranged in cells
2.87 (1.54)
3.57 (1.59)
ns.
1. It takes a lot of training cell worker 2. Anyone can be trained in a cell
5. Cell workers
a Mean b Standard
224
Unit Employees
to be a
to work
Deviation
APICS
cellular manufacturing who actually perform
may perceive the tasks.
the cell jobs as being easier than do the cell workers
DISCUSSION This study was conducted to test the effects of cellular manufacturing upon worker perceptions of and affective reactions to batch manufacturing jobs. The study was designed to offset methodological problems inherent in previous ethnographic research. Contrary to these earlier studies, few significant relationships were detected concerning perceived job characteristics, satisfaction, and performance. While the results do not generally support the experimental hypotheses, they are not without merit. As Greenwald [ 171 and Griffin, Bateman & Skivington [ 191 note, the tendency to reject null findings can be very detrimental to research progress. In fact, scientific advancement is most powerfully achieved by rejecting theories. Greenwald further argues that research should be judged not on the basis of results obtained, but the adequacy of procedures and the importance of findings [ 171. The findings of the current study are important because they represent the first systematic attempt to evaluate the human effects of cellular manufacturing. Job Characteristics Despite the fact that cell workers perform more varied tasks, are responsible for more equipment, work in teams, and receive more rapid feedback, their perceptions of job characteristics did not vary radically from those of employees working in the functionallyarranged unit. The one exception, however, was feedback from agents (supervisors). Cell workers reported that they received less feedback than other workers. The difference may, in part, be due to a decreased need for external feedback among cell workers. Because the jobs are designed to provide feedback, the need for external reinforcement may be reduced. Cell workers also perceived slightly less (only marginally significant) autonomy. This result is plausible because cellular manufacturing requires teamwork. In contrast, employees in the functional units did not necessarily have to cooperate with other workers to complete job assignments. Job Characteristics
and Social Realities
In explaining the pattern of results, the recent work of Salancik & Pfeffer is particularly useful [40, 411. They argue that job characteristics are socially constructed realities; that is, perceived job characteristics may not be fixed and objective, but are defined through the set of information cues about the job which are received by employees from others. According to their model, an individual’s social environment provides cues as to what dimensions are primary in the work environment or to how valued the work is. Thus, jobs which are objectively different in the amount of skill, feedback, and autonomy that is provided, can conceivably be viewed similarly-providing the social cues indicate that they should be. For example, O’Reilly & Caldwell found that the major determinant of perceived job characteristics and job satisfaction was the information cues that the task was either enriched or not enriched [34]. Schwab & Cummings make a similar but slightly different point [44]. They argue that problems arise when perceptions are used to measure environmental characteristics
Journal of Operations Management
225
because an individual’s judgments concerning job characteristics are only partly determined by their objective properties. While cellular manufactu~ng actually involved restructuring jobs to include greater task variety and feedback, the job changes may not have been blatant enough for inexperienced workers, not trained in job analysis, to perceive. Based on this approach, cell and non-cell workers may have perceived their jobs similarly because the organizational cues indicated that the jobs were comparable. This explanation is plausible since the cell workers received the same pay, benefits, and privileges as non-cell workers. As interviews with management revealed, when cellular manufacturing was implemented, job content was examined. However, the decision was made to place the cell jobs in the same class as the highest paid functional jobs. A new higher-paying, job category was not created. Reasons given for the decision were: 1) to prevent friction among workers; 2) to allow workers to be rotated (if necessary) in and out of the cellular units without wage adjustments; and 3) to prevent the administrative overhead of adding a new pay cl~sification level. The decision, but not the rationale, was subsequently communicated to workers. Thus, the social cues provided by top management indicated that cell and non-cell jobs were comparable. Another reason for the low variability in perceptions of job characteristics relates to the timing of the study. The research was conducted after the jobs had been redesigned and workers had been performing in the positions for six months, While perceptions may have varied initially, the passage of time may have dissipated differences, replacing them with a common assessment. Additional research is indicated in which perceptions of workers are examined at multiple time periods. Such research would indicate how or if organizationally-produced cues affect behavioral perceptions and performance. Performance Concerning performance, cell workers were rated higher by their supervisors than noncell workers. The difference, however, was nonsignificant. Less variation in performance, as indicated by the standard deviation, was found among cell workers. This result suggests that cellular manufactu~ng has a positive impact on performance, stabilizing behavior to within a restricted range. While this finding is promising, the results should be interpreted cautiously. As noted by several researchers, supervisory ratings may suffer from problems of leniency, restriction of range or halo effects, all of which can create bias [S, 18, 311. Second, as already noted, the environmental cues provided by top management indicated that the two types of jobs (cell and non-cell) were comparable. Thus, supervisors, like subordinates, may have perceived the job as similar and consequently rated individuals within a similar range. Before definitive conclusions can be made conceding the effects of cellular manufacturing on individual productivity, additional research is needed. Supervisory perceptions of task dimensions should be examined to determine if they moderate their ratings of performance. More importantly, objective measures of productivity should be included in the future. Satisfaction Cell workers were found to be as satisfied with their jobs, supervision, fellow workers and advancement opportunities as were employees assigned to the functional unit. Surprisingly, they were significantly more satisfied with their pay. This finding is interesting for several reasons. First, based on the objective characteristics of their job, they should have been dissatisfied: they performed more complex work for the same pay. Second,
226
APES
according to the Job Characteristics Model, they should have been equally, but not more, satisfied than functional workers because they perceived job characteristics similarly. One explanation for this result is that employee perceptions do not affect satisfaction. It is also possible that other unmeasured variables moderate the relationship between job perceptions and satisfaction. Finally, the cellular manufacturing jobs might have offered less tangible but reinforcing rewards. For example, the opportunity to master new equipment or release from the same boring routine might have been intrinsically rewarding. If such reinforcing, but unmeasured, rewards were present they may have made pay less valued and less salient as a reward. Thus, the same amount of pay would evoke higher satisfaction among cell workers than non cell workers. Again, additional research is needed to determine if other factors not measured moderate the job design satisfaction relationship. CONCLUSIONS While additional research involving cellular manufacturing systems in other organizations is needed, the results of this exploratory study are important. First, the study provided the first empirical test of the proposition that cellular manufacturing has human, as well as manufacturing process, payoffs. It was found that cellular manufacturing neither increases nor decreases employee performance or satisfaction over that achieved in the functionally-designed unit. On first blush, this conclusion may seem disheartening, indicating a less than desirable condition. In reality, the results are very encouraging. They suggest that cellular manufacturing may be implemented without any human fallout. A ramification of this is that reductions in work-in-process and finished goods inventories, decreases in production lead time, and improved overall productivity which reportedly accompany the implementation of cellular manufacturing may be achieved without any negative effects on employees. Additional research should, however, be conducted to determine if the findings of this study generalize to other work situations. REFERENCES 1. Astrop, A.W., “Group Technology as a Way of Life,” Machinery and Production Engineering, 1975, 126 (3241) 42-45. 2. Beeby, W.D. and A. Thompson, “A Broader View of Group Technology,” Computers and Industrial Engineering, 1979, 3(4), 289-3 12. 3. Bim, S.A., “Improving Motivation Through Job Design in the GT Workcell,” SME Technical Paper MS78-976, Computer and Automated Systems Association of SME, 1978, Dearborn, MI. 4. Burbidge, J.L., The Introduction of Group TechnoIogy. London: Heineman, 1975. 5. Burbidge, J.L., Group Technology in the Engineering Industry. London: Mechanical Engineering Publications LTD., 1979. 6. Campbell, D., “Factors Relevant to the Validity of Experiments in Social Settings,” Psychological Bulletin, 1957, 54, 297-3 12. 7. Cook, T.D. and D.T. Campbell, Quasi Experimentation: Design and Analysis Issues for Field Setting. Chicago: Rand McNally Co., 1979.
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APES