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AN ELEJMENT/-yL, COMPONENT DECOMPOSITION
OF A SIMPLE ASSEMBLY TASK
by
JOHN BERNARD SOTMAN, B,S.
A THESIS
IN
INDUS TRIAL ENGINEERING
Submitted to the Graduate Faculty of Texas Technological College
in Partial Fulfillment of the Requirements for
the Degree of
MASTER OF SCIENCE IN
INDUSTRIAL ENGINEERING
June, 1968
1 ''**!^M^
mi l)/o,7l
ACKNOWI.E DGMENT S
I wish to express my appreciation to Dr. M. M. J youb
for his direction of this thesr.s and to the other members
of my advisory committee. Dr. J, D. Ramsey; Mr. W. D.
Sandel; and Dr. N. R. Denny, for their helpful advice and
assistance.
I also wish to thank Mr. C. D. Mittan for his helpful
suggestions in constructing the equipment and Mr, J, L.
Gibbs for developing and building the Component Assembly
Task Analyser.
Lastly, I wish to thank my wife, Carol, for her
patience and helpful criticism, and typing of the draft of
this thesis.
11
TABLE OF CONTENTS
Page
ACKNOWLEDGMENTS ii
LIST OF TABLES V
LIST OF ILLUSTRATIONS vi
Chapter
I. INTRODUCTION . . . . . . . . . . . . . . . . 1
Purpose and Scope 1 Background 2 Sumrriary. . 9
II. EXPERIMENTAL TASK, EQUIPMENT, AND PROCEDURE 10
Task and Workplace Layout 10 Equipment , 21 Experimental Procedure 25
III. EXPERIMENTAL DESIGN , 29
Selection of Variables 29
Star-istical Design , . 35
IV, EXPERIMENTAL RESULTS . 39
Significant Main Effects 39
Significant Interactions 60
V, CONCLUSIONS AND RECOMMENDATIONS 61
Summ.ary 65
LIST OF REFERENCES 69
APPENDIX A. ANOVA Program 7 3
APPENDIX B. Siqnifico.nt Means , . . 77
iii
IV
Page
APPENDIX C. Graphs of Significant Subject Interactions 81
APPENDIX D. Schematic Diagrams of Electrical Circuits 88
LIST OF TABLES
Table Page
1. Elemental Components of Motion 15
2. Factors and Their Levels 36
3. Expected Means Square (EMS) Table 37
4. Significant Effects 40
V
1 ^ -
LIST OF ILLUSTRATIONS
Figure Page
1. Subject Starting the Task 11
2. Subject Reaching for Workpiece 12
3. Subject Positioning Workpiece 13
4. Dimensional Sketch of Work Area 16
5. View of Workplace Layout 17
6. View of Slide and Receiving Box 19
7. View of Workpiece 20
8. View of Component Assembly Task Analyser
(CATA) 22
9. View of Timing Equipment 23
10. Effect of Angular Direction on Reach Time 41
11. Duncan Multiple Range Test for Reach 41
12. Effect of Angular Direction on Grasp Time 42
13. Duncan Multiple Range Test for Grasp 42
14. Effect of Angular Direction on Move Time 43
15. Duncan Multiple Range Test for Move 43
16. Effect of Visual Discrimination on Grasp
Time 47
17. Duncan Multiple Range Test for Grasp 47
18. Effect of Visual Discrimination on Move
Time 48
VI
VI1
Figure Page
19. Duncan Multiple Range Test for Move 48
20. Effect nf Visual Discrim.ination on Total
Time 49
21. Duncan Multiple Range Test for Total Time 49
22. Effect of Weight of Workpiece on Reach
T ime 5 3
23. Dijncan Multiple Range Test for Reach 53
24. Effect of Weight of Workpiece on Grasp
Time 54 25. Duncan Multiple Range Test for Grasp 54
26. Effect of Weight of Workpiece on Position
Time 55
27. Duncan Multiple Range Test for Position 55
28. Effect of Weight of Workpiece on Total
Time 56
29- Duncan Multiple Range Test for Total Time 56
30. Effect of Angular Direction by Subjects on
Reach Time 82 31. Effect of Angular Direction by Subjects on
Total Time 83
32. Effect of Visual Discrimination by Subjects on Reach Time 84
33. Effect of Weight of Workpiece by Subjects on Grasp Tim.e 85
34. Effect of Weight of Workpiece by Subjects on Move Time 86
Vlll
Figure Page
35. Effect of Weight of Workpiece by Subjects on Total Tim.e 87
36. Schematic Diagrams of the Componen:: Assembly Task Analyser (CATA) 89
CHAPTER I
INTRODUCTION
Over the years, the concept of time and motion study
has grown from a state of infancy into the v;ell-defined,
technological science it is today. However, probably one
of the most significant contributions made in this area wa.s
that of Frank B. Gilbreth in the early nineteen hundreds
when he defined the elements of motion. Since that time.
Industrial Engineers have traditionally separated a motion
into its elemental components when applying the techniques
of time and motion study. This thesis describes an inves
tigation of how three variables affect the fundamental
elements of motion of a sim.ple assem.bly task.
Purpose and Scope
The purpose of this experiment was to investigate the
effects of the following independent variables, visual dis
crimination, weight of the workpiece, and angular direction
of movem.ent, on the times of the elemental components of a
simple assembly task. The task in general involved the
movement of workpieces from a supply bin to a target area
and the subsequent insertion of the piece into the target
«
hole. In Gilbreth's terminology, the elemental components
of hand motion involved are transport empty, grasp, trans
port loaded, and position. For the purpose of simplicity,
the elemental components transport empty and transport
loaded will hereafter be called reach and move, respectively
A more detailed discussion of the independent variables is
contained in Chapter III.
The dependent variables utilized in this experiment
were the times required to perform the elemental components
of motion. Reach, Grasp, Move, and Position, as well as the
total time of the task. These elements are defined in more
detail in Chapter III.
The scope of the experiment was to analyze the de
pendent variables by the method of analysis of variance
to determine v;hEit effect the independent variables had on
che times of the component elements of motion and on the
total task time.
Backqroung
The problem of determining the m.osL efficient way to
perform a manual task has plagued man ever since he started
receiving compensation for his servile efforts. However, a
formal technological system of analyzing m.anual labor wa^
not organized until the seventeenth century when a man
named Frederick W. Taylor invented V7hat he called "Time
Study." As originated by Taylor, the time study was used
mainly for determining the tim.e standard of a given job.
Taylor himself said,
Time study is the one element in scientific . management beyond all others making possible the "transfer of skill from management to mien. " "Time study" consists of two broad divisions; First, analytical work, and second, constructive work (2).
Basically, Taylor believed in focusing his attention
on the materials, tools, and equipment used on the job to
develop more efficient methods of performing the task.
However, he stated unequivocally, "that one of the first
duties of mianagement was to develop a science for each
element of a man's work" (2). Taylor was actually touch
ing upon the area of motion study which was developed by
two of the great pioneers in this field, Frank and Lillian
M- Gilbreth. Motion study had its beginning in 1885 when
Gilbreth, only a boy of seventeen, made his famous study
of the bricklayer's trade. Gilbreth pioneered micromotion
study, in which he used motion pictures to help analyze
his v/orkers in motion. He placed great value on this
technique as it was probably the first technological
breakthrough in the problem of correctly analyzing motions.
Gilbreth also invented the chronocylegraph which he used
to study the path of motion of his operators. This tech
nique utilized small electric bulbs, v;hich v/ere attached
to the fingers, hand, or other parts of the body, and a
still camera. The resulting photograph indicated the di
rection of motj.on as well as the speed of the motion.
In his work in motion study, Gilbreth decomposed
motion into seventeen basic elements which he called
"therblig" (Gilbreth spelled backv/ards) . The therblig
terminology gained wide invdustrial acceptance and has
been carried forward to modern day motion analysis. How
ever, it was not until the early 1900's that motion study
became recognized as a method of finding better and easier
ways to get the job done.
V?ith the vast expanding industrial complex ixi the
United States, it becam.e evident that additional research
in analyzing motions as v;ell as in the equipment used for
such analysis had to be undertaken. One of the earlier
studies done in the area of motion analysis was that of
Brown and Slater-Hammel in 1949 which produced some inter
esting results (4). For a long time, it was thought, and
some experiments actually obtained evidence supporting
this point of view, that as the length of the movement
increased, the speed of the movement increased in a direct
proportion so that the movement time remained constant
over distance. The results of the Brown and Slater-Hammel
experiment found this not to be true. They found that as
the distance increased, the speed also increased but not
in a direct proportion. Therefore the movement ti.me did
not remain constant over distance. Another interesting
aspect of this investigation was that there appearsd to
be a slight tendency for the right to left movemients to
be faster than left to right movements. This finding was
in direct opposition to that of A. S. Householder who con
cluded that left to right miovements v/ere superior to right
to left movements (4). However, both of these findings
were not statistically significant.
The next major adv^ancement in the area of motion
analysis was that of Davis, Wehrkamp and Sm.ith at the
University of Wisconsin in 1951 (5). In their experim^ent,
they used a new piece of equipment which they called the
"Universal Motion Analyser." This enabled them to accu
rately separate the total motion time into its two
components, manipulation time and travel time. They found
that travel time was influenced by the type of manipulation
which was performed at the end of the movement. They also
discovered that the direction of motion (right or left, up
or down) did not affect the manipulation tim.e, but that
the travel time was shorter for vertical motions than for
horizontal motions. Hov/ever, probably the most significant
conclusion of this study is stated as follows:
It has been observed that there is no systematic relation or correlation between the manipulative and travel components of motion patterns in a set task. This fact points out a need for marked revision of measuremient technique and applied study of psychomotor tasks in relation to both individual appraisal of psychomotor performance and general analysis of psychomotor skill situations. It is quite evident that the failure -co find significant relations between differe:::it psychomotor tasks and to predict performance in these tasks is accounted for in part by unknown variations in the basic unrelated componentis of m.anipulatior and travel in the task situations (5) .
In another important experiment in the development of
modern day motion analysis, Wehrkamp and Smith in 1952
investigated the effects of type of manipulation and dis
tance of travel on the components of the motion (29).
They found that the manipulation time of turn movements
was 53% faster than that of pull movements and that the
travel time of turn mLOvements was 32% faster than that for
pull movements. They also found that an increase in the
distance traveled between successive movements induced an
increase in the travel and manipulation components of the
motion involved. This prompted the authors to make the
following statement:
Thus it has been shown that pattern of m.anipulation and distance of travel have integrative effects related to all of the com.ponents of the v/orking task and do not affect alone the component of movement primarily related to those dimensional variations (29).
vhat they are saying is that the time required for a
given comporisnt of motion can be influenced by the compo
nent v;hich precedes it as well as by the one that follows
it.
This is in direct contrast to the underlying prin
ciple of predetermined time systems which assum.e that each
comiponent in a task is independent of every other compo
nent and therefore the total time of a task can be obtained
by addition of the various components.
This sam.e conclusion was borne out by Schmidtke and
Stier in a series of experiments conducted in 1960 at the
Max-Planck-Institute for Work Physiology in Dortmund,
Germ.any (2 2) . A rebuttal to the Schmidtke and Stier report
8
was written by J. M. Honeycutt, Jr., in 1962 in which he
defended one predetermined timie system in particular, MTM
(Methods Time Measurement) (15). In his article, Honeycutt
pointed out that in MTM no assumptions were made concerning
time when development research of MTM was being conducted.
He points out in particular that MTM does not assumte that
elemental times are additive. In concluding his remtark,
Honeycuct makes an important comment in v/hich he says:
There is a real need for careful research in the field of predetermined elemental times. How much thj.s wil]. change existit^g systems which have been found to work v/ell when properly applied may be debatable. Every user of predeterrained elemental times, hov/ever, would like to understand more about the fundamental characteristics of rrotioii so that man can improve his ability to design effective, non-fatiguing motion sequences and so that he can improve the speed and accuracy of applications (15).
All of the predetermined time system.s in existence
today embody the elemients Reach, Grasp, Move, and Position.
In these systems, the time to perform a given motion de
pends on many variables such as the body member which per
forms the motion, the distance the body member moves, the
weight or resistance involved in the motion, and whether
or not the motion is under manual control (2), (16), (20).
However, none of these systems account for any effects due
9
to the factors of weights under two pounds, the direction
of motion, and whether or not the task is under any visual
disci imdnation requiremeni:s. Triis study has investigated
the effects of these factors on the elemental components
Reach, Grasp, Move, and Position as well as on the total
time required to perform the task.
Summary
Previous research has shov/n that the time required to
com.plete a particular motion C3.r be affected by a number of
factors, including the direction of the m.otion, the rela
tionship of various body members to the rest of the body,
the degree of precision required, and whether or not the
motion was under visual or tactile control. Most of these
studies were concerned with the effect of these variables on
the total time required to perform, a particular motion.
This research wa~ concerned with the effects of three
variables, angular direction of movement, visual discrimi
nation, and weight of the workpiece, on the component
elements of motion of a simple assembly task- To the
author's knov/ledge, the study of the combination of the
above variables on an assembly task was without precedent,
and therefore was deserving of a detailed investigation.
ft
CHAPTER II
EXPERIMENTAL TASK, EQUIPMENT, AND PROCEDURE
Task and "Workplace Layout
The experimental task was designed to simulate a cne-
handed assembly operation in an industrial situation, and
was simular to that used by Wall (29). It was recognized
that a one-handed assembly operation was not the most
efficient method of accomplishing the task, and that, in
practice, tv/o hands would probably be used. However, for
the purpose of simplicity and in order to establish a
framework to which future research in this area could be
compared, only one hand was utilized in the task.
The subject started the task with his hand resting on
a piece of aluminum foil which circumscribed the target
hole as shown in Figure 1. At the command of the experi
menter, the subject reached for a workpiece which was
stored in a supply bin ten inches away. This is shov/n in
Figure 2, He then grasped the workpiece and moved it to
the target area, made contact with the aluminum foil with
his fingers, and inserted the piece into the hole as shown
in Figure 3. The subject continued to repeat this sequence
10
11
Figure 1. Subject starting the task
12
Figure 2. Subject reaching for workpiece
13
Figure 3. Subject positioning workpiece
14
until all of the designated pieces had been assembled into
the target. This completed the task for the situation
where there was no visual discrimination required. Slight
variations in the task were required, depending on the
level of visual discrimination that was performed. This
will be discussed in detail in Chapter III.
The subject was required to move ten workpieces in a
given task as this simplified the mathematics involved in
obtaining the average time for each component of motion.
However, this in no way compromised the validity of the
statistical analysis. Four replications of each of the
60 variable combinations were required of each subject. A
complement of four subjects was used and the total number
of observations recorded in the experimtent v«/as 4800. Only
right-h.anded subjects were chosen to perform the task. As
a result, the subjects performed the follov/ing movemicnts
in the sequence indicated: Reach, Grasp, Move, and Posi
tion. The single performance of the above elements was
considered as a work cycle. The beginning and end of
these elements are defined in Table 1.
A dimensional sketch of the work area is shown in
Figure 4. Figure 5 shows an actual view of the workplace
15
Table 1. Elemental Components of Motion
Element
1. Reach Beginning:
2. Grasp
3. Move
Position
End:
Beginning:
End:
Beginning:
End:
Beginning:
End:
Hand breaks contact v/ith aluminum foil surrounding target hole.
Hand makes contact with workpiece in supply bin.
End of Element 1.
Workpiece breaks contact with supply bin.
End of Element 2.
Hand makes contact with aluminum foil surrounding target hole.
End of Elemicnt 3.
Workpiece inserted one inch into target hole.
16
180' 0'
Coronal Plane
Midsaggital Plane
Figure 4. Dimensional sketch of work area
17
Figure 5, View of workplace layout
18
layout. The distance from, the supply bin to the target
hole was held constant at ten inches. A slide was placed
under the work table to direct the workpieces into a re
ceiving box as they were inserted through the target hole.
This can be seen in Figure 6. Figure 7 shows a close-up
view of one of the workpieces which were constructed from
35 millimeter film containers. These workpieces were ap
proximately 1 7/16 inches in diameter and 2 ^ inches in
length. The target hole was two inches in diameter. The
mid-point of the bins was placed at 0°, 45°, 90°, 135^,
and 180° from, the horizontal as shown in Figure 4, page 16.
It was found by Ellis that worksurface height affects
the speed of movement (6). He found that the fastest per
formance times for a block turning task were produced from.
a worksurface height in the range of tv7o to three inches
below the level of the elbow. As a result, an adjustable
height chair was used and the subjects were seated so that
the worksurface height v;as two inches below the level of
the elbow, as this height minimized the problem of the
subject's thighs contacting the underside of the worktable.
The chair was situated so that each subject was three
inches av;ay from the edge of the worktable.
19
Figure 6. View of slide and receiving box
20
Figure 7. View of workpiece
21
Equipment
Most of the equipment utilized in this experiment was
of a comonon industrial nature and has been discussed
earlier in this chapter. However, a most significant
achievement of this research was the development of an
electronic device which has been named the Component
Assembly Task Analyser (CATA), This unique piece of equip
ment can be seen in Figure 8. The purpose of the CATA was
to serve as a control mechanism to start and stop the tim.-
ing devices in the proper sequence in order that the times
of dependent variables. Reach, Grasp, Move, Position, and
total cycle tim.e could be recorded. To simplify m.atters,
the CATA was a series of capacitance relays which depended
upon the capacitance of the human body to activate the
various electronic circuits. Schematic diagrams of the
CATA are shown in Appendix D.
Five Cramer Controls Corp. electronic timing clocks
with accuracy to 1/100 of a second were used to record
the elemental times. These timers were capable of accum
ulating time and could be reset after each combination of
variables was run. Figure 9 shows the timers as they were
set up for the experim.ent. The first timer recorded the
22
Figure 8. View of Component Assembly Task Analyser (CATA)
23
Figure 9. View of timing equipment
24
Reach time, the second timer the Grasp time, the third
timer the Move time, the fourth timer the Position tim e,
and the fifth timer the total cycle tim.es.
The CATA controlled these timers as follows: When
the subject's hand broke contact with the aluminum foil,
the CATA started clocks 1 and 5; when the subject's hand
made contact with a workpiece, the CATA stopped clock 1
and started clock 2; when the workpiece broke contact with
the supply bin, the CATA stopped clock 2 and started
clock 3; when the subject's hand made contact with the
aluminum foil surrounding the target hole, the CATA stopped
clock 3 and started clock 4; and when the workpiece was
inserted a distance of one inch into the target hole, the
CATA stopped clocks 4 and 5 and the work cycle was com
pleted. Vhen the subject reached for the next workpiece,
clocks 1 and 5 were restarted and the same process was
repeated. Tlie supply bins were covered v?ith aluminum
foil which allowed the CATA to detect the change in capac
itance as the subject's hand entered and left the bin.
The aluminum foil was in turn covered v;ith paper to prevent
any chatter in the electronic circuits should the subject's
hand make direct contact with the surface of the supply bin,
25
In order to determine when a workpiece was properly
positioned, an electromagnetic coil was attached to the
underside of the target hole. The resistance of the coil
was adjusted so that when the workpiece was inserted one
inch into the hole, the voltage in the coil circuit was
of a sufficient nature to activate the CATA which stopped
clocks 4 and 5. Clock 5 served as a check on the total
cycle time as the four components of motion were added
together to obtain the total time figures which were used
in the analysis of variance. It was found that generally
the figure obtained by adding the four components of
motion was within t 5/100 of a second.
Experimental Procedure
Each of the four subjects were instructed that the
purpose of the experiment was to measure how qijickly they
could perform the assigned assembly task. They were cau
tioned, however, that any error made in the assembly pro
cedure would result in having to rerun the task. This,
then, provided the mtOtivation to perform the task as
quickly and as accurately as possible. The task was
visually monitored to assure that no errors were made in
26
the assembly procedure.
After an explanation of the task, each subject was
seated in the chair and the height adjusted so that the
level of the elbow was two inches above the surface of the
worktable. Prior to the first experimental session, each
subject was allowed approxim^ately fifteen minutes to prac
tice the assembly task in order to become proficient in
handling the workpieces and to develop a familiarity with
the various combinations of the independent variables. At
subsequent sessions, each subject was allowed four practice
runs prior to the recording of actual data. Each session
lasted approximately one hour and twenty minutes, and there
was no restriction on when the session was held. The sub
jects performed each of the 60 variable combinations a
total of four times; however, the order of the variable
combinations was completely randomized. There was approxi
mately a one minute interval between runs, during which
time the subject was allowed to rest, thereby minimizing
the effects of fatigue.
The actual data recording sessions were then conducted
in the following manner:
1. The subject was seated in the adjustable height chair with his elbow two inches above the surface
27
of the worktable and his body three to four inches away from, the edge of the worktable. Ten workpieces of the proper weight were placed in the specified supply bin and the subject was instructed as to v/hat visual discrimination he was to perform according to the randomly chosen treatment combination.
2. The subject then placed his right hand on the aluminum. foJ.l surrounding the target hole, and on the commiand of the experimenter, started the assembly task. Visual monitoring was m.aintained throughout the task to assure that no errors were com-mitted.
3. Upon insertion of the last workpiece through the target hole, the electronic circuits were deactivated by throwing a two-way, off-on power switch. The timers were then read and the data recorded. At the same time, the expended work-pieces were collected from the receiving box and preparations were made to run the next combination of variables according to a previously randomiized list of treatmicnt conditions.
4. The timers were then reset to zero and the power switch turned on. The above procedure was then repeated for the next variable combination. A total of 60 variable combinations were run at each experimental session.
The experiment was conducted in Room 204A, Industrial
Engineering Building, Texas Technological College. The
room was well lighted, was sound proofed from outside
noise, and, more importantly, was air-conditioned v/hich
kept the temperature relatively constant. This was im
portant in that it kept any drifting of the electronic
28
com.ponents of the CATA to a minimum. Approximately 40
man-hours were expended in collecting data for this ex
periment. The independent variables selected for study
in this experiment and the statistical design of the ex
periment are considered in the next chapter.
CHAPTER III
EXPERIMENTAL DESIGN
Selection of Variables
As mentioned in Chapter I, the dependent variables
measured in this experim.ent were the times required to
perform the elemental components of motion. Reach, Grasp,
Move, and Position, as well as the total time of the task.
The independent variables chosen for study were visual
discrimination, weight of the workpiece, and angular direc
tion of movement. In previous studies analyzing hand
motions, some attention had been focused on the above men
tioned variables; but, in almost every case, the prirric
interest had been the effect of the variables on tlie over
all time required to perform the task. In this investiga
tion, it was proposed to examine the effect of the variables
on the individual components of motion that comprise the
k.a s j^.
Visual Discrimination
The levels of visual discrimination chosen for this
study v/ere: no discrimination, discrimination at the parts-
supply area, discrimination at the assembly area, and
29
30
discrimination at both the parts-supply area and assembly
area. An experiment conducted by Simon and Smader inves
tigated the problem of visual discrimination at the assem
bly area (23). They found that all four components of
motion suffered significant differences in the duration
when under visual discrimination. However, left unan
swered was the question of hov7 do discriminations made at
the parts-supply and at the assembly area differ in their
effects on the elements of motion? This study proposed
to answer that question.
The task involved in this research was the movement
of a workpiece from a supply bin and its subsequent inser
tion into a target hole. Some of the workpieces had one-
half of their shafts painted yellov; and the otliers were
completely painted a silver color. Under the condition
of discrimination at the parts area, the supply bin con
tained ten pieces painted yellow and three pieces painted
completely silver. The subject was required to pick out
only those pieces which had one end painted yellow and
move them to the assembly area and insert them into the
target hole. In the discrimination at the assembly area
problem, the supply bin had ten workpieces, all of which
31
had one end painted yellow; and the subject was required
to pick out a piece and move it to the assembly area and
insert it, painted end first, into the target hole. The
condition of discrimination at both the supply area and
the assembly area consisted of having the subject pick out
a workpiece with one end painted yellow from among the
completely silver pieces and insert it into the target
hole, yellow end first. Under the condition of no dis
crimination, there was no restriction whatsoever on the
movements; the subject simply moved ten workpieces and
inserted them in whatever fashion was most convenient.
Weight of the V7orkpiece
The three levels of this factor were .01 lb., .45 lb.,
and .90 lb. Using 35 millimeter film containers as the
workpieces, the above mentioned levels were obtained in
the following manner:
1. The .01 lb. was the weight of the empty containers .
2. The .45 lb. was obtained by filling the container with an appropriate amount of No. ih lead shot.
3. I'he .90 lb. was the weight of the container when it was poured full of m.olten lead.
32
A study by Schmidtke and Stier showed that as the
weight of the workpiece increased, the time required to
perform the task increased (22). However, their task in
cluded only the element transport loaded. It v/as proposed
in this experiment to study the effect of weight of the
workpiece on all the elements of the motion involved.
The above levels were chosen because they were represent
ative of the range of weights that might be encountered
in light assembly tasks.
Angular Direction of Movement
The levels of this independent variable were 0, 45,
90, 135, and 180 degrees as measured counter-clockwise
from the horizontal. Schmidtke and Stier also investi
gated this variable and found that a movement of 45 degrees
produced the fastest time to complete their task (22).
Again, however, they were mainly interested in the effect
on the total tim.e, whereas the purpose of this study was
to determine the effect of angular direction on the indi
vidual elements of motion. Research conducted by Ayoub
showed that the velocity of movement v/as a maximum, in the
45 degree direction (1). A thesis by McElhannon demon-
33
strated that the center of gravity of the arm traveled the
shortest distance in the 0 to 45 degree direction (18).
These results tend to explain the findings of Schmidtke
and Stier. Another experiment by VonTrebra and Smith has
shown that direction of travel movement affected only the
travel component of the motion (28). However, the task
movements involved were either vertical or horizontal.
The effects of a diagonal movement were not investigated,
and the task involved was that of turning switches, not an
assembly task. This study investigated the effects of
direction of movement on the elemental movements of an
assembly task, and has determined under what conditions
direction becomes a relevant variable in determining the
duration of movement.
Subjects
Four subjects were chosen at random from a right-
handed male population for this experiment. All of the
subjects were students at Texas Technological College and
had no physical handicaps. There was no restriction in
the selection of the subjects except that they were right-
handed.
34
Replications
Four replications of the experimicnt v/ere perform.ed by
each of the subjects. The effect of learning on the depen
dent variables was not of interest in this experiment
since it had been shown previously that practice did not
uniformly affect the elements of motion and that the grasp
ing and positioning components were affected the most (24),
(30). For this reason, the replications were completely
randomized as to the order of occurrence. The main purpose
of the replications was to provide an error term with which
to test the other main effects and their interactions in
the analysis of variance.
Dependent Variables
The dependent variables chosen for study were defined
as follows:
1. Reach - The time elapsed from when the subject moves his right hand from a resting position until he makes contact with a workpiece located in a storage bin,
2. Grasp - The time elapsed from when the subject's hand initially makes contact with the workpiece until the v/orkpiece breaks contact with the storage bin.
3. Move - The time elapsed from when the workpiece breaks contact with the storage bin until the
A •-r
35
subject's hand makes contact with aluminum foil which circumscribes the target hole.
Position - The time elapsed from when the subject's hand m akes contact with the aluminum foil until the workpiece is inserted a distance of one inch into the target hole.
5. Total Time - The time elapsed from v/hen the subject's hand breaks contact v/ith the aluminum foil which circumcscribes the target hole until the workpiece is inserted one inch into the target hole.
Statistical Design
The statistical design of this experiment was a four-
way factorial completely randomized design with four obser
vations per cell. The independent variables and their
associated levels are shown in Table 2. The expected mean
squares and degrees of freedom for each of the main effects
and the va.rious interactions aire shown m Table 3. This
table indicates v;hat mean squares were used in obtaining
the .F-ratio test m testing for the significance of a par
ticular factor. It can be seen that the effect of subjects
and all interactions with this effect were tested against
the error mean square. All of the ether effects and their
interactions v/ere tested against the mean square of their
interaction with the effect of subjects.
Table 2. Factors and Their Levels
36
FACTOR SYMBOL TYPE LEVEL LEVEL CODE
Angular Direction Fixed OO 45< 90°
135 ^ 180*
1 2 3 4 5
Visual Discrimination V Fixed None Target area Supply area Both
1 2 3 4
Weights W Fixed .01 lb, .45 lb, .90 lb.
1 2 3
Subject: S Random #1 #2 #3 #4
1 2 3 A -X
Replications R Random. #1 #2 #3 #4
1 2 3
Table 3. Expected Mean Square (EMS) Table
37
Source
Degrees of
Freedom EMS
V.
W,
AV
AW ik
AS
VW
il
VS
ws kl
AVW^j^,
AWS.3^,
vws jkl
AVWS^.^^l
Error
4
. 3
2
3
12
8
12
6
9
6
24
36
24
18
72
720
01 + 48 0I3+ 60 ol
02 + 60 o2g + 100 o2
o? + 80 o2 4 200 o2 ws
o2 + 240 o2
^e + 1^ ^iws
01 + 48 o2.,
^i + 20 o2^s
02 + 60 o2g
w
+ 5 o? ciV
+10 o2 . avv
+ 1^ vw
i ol ol
+
+
+
SO
4
12
^^s
o2 ^avws
a2 avs
a2 + 16 o2 e aws
a2 + 20 0-2 e vws
0-2 + 4 a2 ^e avws
+ o 2 avw
Total 959
38
The model of the experiment was:
'ijklm = - + A^ + Vj + W^ + S^ + hV^. + AW 3 + AS^^
+ WJ.^ . VS.^ + WS ^ -f AVW^.^ + AVS^.3^ +
^^^ikl - ^ S .3 ^ + AWS^ .3 , + e^ .3 ^
Where:
^iiklm ~ ^ P ^ ^ t variable for the i, j, k, 1, m levels of respective treatments.
J =•- Common effect for the entire experiment.
A. - Effect of the angular direction.
V. = Effect of visual discrimination.
W, - Effect of weights.
S, - Effect of subjects.
e.^, , = Error term com.posed of effect of replications
all other terms - E.ffects of the various interactions
of the main factors.
The analysis of variance was accomplished on the IBM
7040 computer utilizing the Brigham Young University Anal
ysis of Variance program available at the Texas Technolog
ical College Com.puter Center. Five univariate analyses of
variance were run, one for each of the stated dependent
variables. The results of the analyses of variance are
treated in the next chapter.
CHAPTER IV
EXPERIMENTAL RESULTS
This chapter considers the main effects and interac
tions which were found to be significant in the analyses
of variance. Only those main effects and interactions
which were.significant at the one or five percent level
will be discussed and these are shown in Table 4. A print
out of the analysis of variance (ANOVA) program is given
in Appendix A. The means of the significant main effects
and interactions are presented in Appendix B. A Duncan
Multiple Range Test has been performed on all significant
main effects. Those levels which are underlined are not
significantly different from one another.
Significant Main Effects
Angular Direction
The five levels o.f angular direction of movement were
discussed in Chapter III. The effect of angular direction
was significant on the Reach, Grasp, and Move components
of motion. Figures 10, 12 and 14 show the effect of this
variable on the significant elemental component times.
Figures 11, 13, and 15 show the results of the Duncan
39
40
Table 4. Significant Effects
Source
Angular Direction
Level of Significance For:
Total Reach Grasp Move Position Tim.e
Subjects
Angular Direction by Subjects
.01
Visual Discrimination NS
Weight of Workpiece .01
01
.01
Visual Discrimination by Subjects .05
Weight of V7orkpiece by Subjects NS
.01
.05
.01
NS
NS
NS
.05
.05
.01
NS
.01
NS
NS
.01
NS
NS
.05
.01
NS
NS
NS
NS
.01
.05
.01
.05
NS
01
w c o u 0) CO -H iH rH •H
0) e •H
325
300
275
250
225
(
41
. O
™J„ J .i_-. OO 45^ 90O
± 135^ 180O
Angular Direction
Figure 10. Effect of Angular Direction on Reach Time
Angular Direction: 45 0 orO 135 90' 180 o
Figure 11. Duncan Multiple Range Test for Reach
325 r
300
CQ 73 C O U Q)
-H 275 i-i
rH
•H
0) e •H EH 250
225
i .. L OO
42
-e>-
J—--.. -. 450 90C 1350 180 o
Angular Direction
Figure 12. Effect of Angular Direction on Grasp Time
Angular Direction: 180' 135* 90' 45'
Figure 13. Duncan Multiple Range Test for Grasp
43
CO 'U c o u Q) CQ •H
-H
B •H
E
500 r-
475
450
425
,_-—--0
OO 450 900 135° J I8OO
Angular Direction
Figure 14, Effect of Angular Direction on Move Time
Angular Direction: 45' 00 90 o 135 o 180 o
Figure 15. Duncan Multiple Range Test for Move
44
Multiple Range Tests on these elements. The effect on
each of the components is discussed below.
Reach: The time to complete the Reach component was
significantly lower for movements in the 45 degree direction.
It is shown by the Duncan Multiple Range Test in Figure 11,
page 41, that there was no significant difference in the
times for 0, 90, 135, and 180 degrees. This result agrees
witJi that found by Schm.idtke and Stier, Ayoub, and
McElhannon. However, it is interesting, to note that, al
though angular direction had a significant effect on Reach,
it was non-significant as far as total time to complete
the task was concerned. The reason that the Reach time is
lower at 45 degrees is that the center of gravity of the
arm travels the shortest distance at that angle. There
fore, the moment of inertia is at a minimum and less time
is required to complete the motion.
Grasp: The time required for the Grasp component was
almost the complete antithesis of tlie Reach component.
The time for Grasp was lowest for 180 degrees and highest
for 45 degrees. This was just the opposite for the Reach
component. This was an unexpected result and is not
easily explained. For some reason, when the Reach was
45
fast, the Grasp was slow; and when the Reach was slov/, the
Grasp was fast. This is a case of the preceding element
affecting the succeeding element. The Duncan Multiple
Range Test of Figure 13, page 42, shows that there is no
significant difference between 0 and 45 degrees and be
tween 90, 135, and 180 degrees. This is borne out by Fig
ure 12, page 42.
Move: The times required to complete the Move com
ponent very closely followed the tim.es for the Reach com
ponent. The 45 degree direction produced the fastest Move
time, but the time was almost twice as slow as that needed
for the Reach. Also, the difference between the 45 degree
direction and the other directions was not nearly as pro
nounced as it was for the Reach component. This can be
clearly seen by comparing Figures 10 and 14, pages 41 and
43 respectively. The biggest reason for this is probably
the fact that in the Reach, the subject is making the motion
away from the body; and in the Move, the subject is making
the motion tov/ard the body. Research by Goodv7in (10) has
shown that moves away from the body are faster than those
toward the body. Another reason for this is that, in the
Reach, the subject is making the motion empty handed and,
46
in the Move, the subject is making the m.otion with the
workpiece which weighed from .01 lb. to .90 lb. This has
the effect of increasing the mas:s of the forearm which is
moved and therefore increasing the Move time. The addi
tional weight seems to have a leveling effect on the time
and ostensibly, if the v;eight were increased to some upper
limit, the effect of angular direction on Move time would
be negligible. Figure 15, page 43, shows that there is
no significant difference between 0, 90, 135, and 180
degrees and between 45 and 0 degrees.
Visual Discrimination; The independent variable,
' visual discrimination, had a significant effect on the
components. Grasp and Move, and on the rotal time of the
assembly task. These effects are demonstrated in Figures
16, 18, and 20. The Duncan Multiple Range Test for these
effects are shown in Figures 17, 19, and 21. It is inter
esting to note that visual discrimination had no signifi
cant effect on the time for Reach. It appears that the
subjects were adjusting for the various levels of visual
discrimination in the Grasp time. Also, the Position time
was non-significant, the reason being that the subjects
were doing any required pre-positioning during the Move
•H
300
47
CQ
C o u c CQ •H 275
.- O
e •H EH 250
1 >
L_ None
I Target Supply Both
Level of Visual Discrimination
Figure 16. Effect of Visual Discrimination on Grasp Time
Visual Discrimination: None Target Supply Both
Figure 17. Duncan Multiple Range Test for Grasp
48
5oor
CQ 'O c o o 0) CQ •H
-H
e •H EH
475
450
425
± 1 None Target
I X Supply Both
Level of Visual Discrimination
Figure 18. Effect of Visual Discrimination on Move Time
Visual Discrimination: None Supply Target Both
Figure 19. Duncan Multiple Range Test for Move
1375r
1350
49
1325
CQ TJ C O U Q) CQ -H
•H
B -H EH
1300
1275
1250
? J. X J
None Target Supply Both
Level of Visual Discrimination
Figure 20. Effect of Visual Discrim.ination on Total Time
Visual Discrimination: None Supply Target Both
Figure 21. Duncan Multiple Range Test for Total Tim.e
50
component which was highly significant. The effects on
the components Grasp and Move and on the total time are
discussed below.
Gra^£: The level of visual discrimination which had
the fastest Grasp time was that of no discrimination.
Visual discrimination at the target area was the next
fastest, followed by discrimination at the parts-supply
area, and, finally, the condition of visual discrimination
at both the parts-supply area and the target area. These
results generally follow those found by Simon and Smader
in that the time for all four components of motion was
increased when under visual discrimination. From Figure
17, page 47, it can be seen that there is no significant
difference in the Grasp time between discrimination at the
target area and at the parts-supply area. Also of notable
interest is the fact that there is no significant differ
ence in the Grasp time for the conditions of no discrimina
tion and discrimination at the target area.
Move: The time for the elemental component Move was
fastest for no discrimination. Tlien next in order were
discrimination at the parts-supply area and at the target
area; however, the differences between these two levels
51
were not statistically significant. This can be seen
quite graphically in Figure 18, page 48. The Move time
for the condition of discrim.ination at both the parts-
supply area and the target area was significantly longer
than any of the other conditions of discrimination. This
result was not wholly exepted as there is no difference
in performing the Move component of motion between the
condition of discrimination at the target area and the
condition of discrimination at both the target area and
the parts-supply area. The only explainable difference
is that in the condition of discrimination at both the
parts-supply area and the target area, the Move component
is preceded by a p.roce3S of discrimination in the Grasp
component. This suggests that the component Move is being
affected by the preceding component Grasp. The Duncan
Multiple Range Test on the component means is shown in
Figure 19, page 48.
Total Time: The effect of visual discrimination on
the total time required to complete the task, is shown in
Figure 20, page 49. The Duncan Multiple Range Test of
Figure 21, page 49, shows that the total time Vvas signif
icantly lower for no discrimiination; hov^ever, there was
52
no significant difference between the other three levels
of visual discrimination. It is interesting to note that
the total time for discrimination at the target area v as
practically the same as that for discrimination at the
parts-supply area. Tnis can be clearly seen in Figure 20,
page 49.
Weight of Workpiece
The independent variable, weight of the workpiece, was
highly significant on all of the elemental com.ponents of
motion with the exception of the component Move. Figures
22, 24, 26, and 28 graphically depict the effect on the
various components. The Duncan Multiple Range Tests for
these effects are shown in Figures 23, 25, 27, and 29. The
non-significant effect of the weight of the workpiece on
the element Move was unexpected and in direct opposition
to the results obtained by Schmiidi.ke and Stier. They found
that the time for Move increased with increasing weight;
however, as mentioned in Chapter III, their task was com
posed only of the element Move.. But, in an actual assembly
task, the subjects performed the Move component without
any statistically significant difference in regard to
weight. Goodwin, in a study in 1964. obtained the same
•H
300
53
CQ
C O O Q) CQ •H
275
•H E-< 250
^
01 lb !
45 lb. .90 lb,
Weight of Workpiece
Figure 22. Effect of Weight of Workpiece on Reach Time
Weight of VJorkpiece: .45 lb. 90 lb .01 lb,
Figure 23. Duncan Multiple Range Test for Reach
325
300
54
CQ
C o o Q CQ -H
275
•H
B 250
225
± . 0 1 l b 45 l b
I I I I M i l l
. 9 0 l b .
Weight of Workpiece
Figure 24. Effect of V^eight of Workpiece on Grasp Time
Weight of Workpiece: .01 lb. .45 lb .90 lb
All Significant
Figure 2^. Duncan Multiple Range Test for Grasp
CQ tJ C O u Q) CQ
•H
g -H FH
325
300
275
250
55
0-.
e I
.01 lb. __i
.45 lb. 90 lb,
Weight of Workpiece
Figure 26. Effect of Weight of Workpiece on Position Time
Weight of Workpiece: .45 lb. .01 lb. 90 lb.
Figure 27. Duncan Multiple Range Test for Position
1350
56
CQ
c o u (U CQ -H
1325
-H
21 S 1300
e •H EH
1275
t.. 01 lb.
\
45 lb ._J .90 lb
Weight of Workpiece
Figure 28. Effect of Weight of Workpiece on Total Time
Weight of Workpiece: .45 lb. .01 lb .90 lb
Figure 29. Duncan Multiple Range Test for Total Time
57
result (10). In that experiment, weights of 2, 4, and 8
ounces were used. There appears to be no ostensible reason
for this result, unless the difference xn v eight was not
great enough to influence the element Move. The effect of
weight of the workpiece on the other dependent variables
is discussed below.
Reach: The time required for the Reach component was
lowest for .45 lb. with .90 lb. being the next fastest.
However, the difference was not significant. This is shown
in Figure 23, page 53. The time for the .01 lb. v/eight was
significantly longer than the other two. This result was
unexpected as the v/eight of the workpiece had nothing to
do with the Reach component. However, the subjects were
aware of the weight of the workpiece prior to performing
the task, and this appears to have had some effect on the
Reach time. This seems even more plausible when it is
considered that the Grasp component was fastest for the
.01 lb. weight and slowest for the .90 lb. weight. This
is a case of a following elem.ent affecting a preceding
element. What appears to happen is that the subject, aware
of the difference in his ability to grasp the different
weights, is making up for this by adjusting his Reach, time.
58
In other words, when the subject knows that it is going to
take him significantly longer to grasp a certain weight,
he speeds up his reach in an attempt to counterbalance the
longer grasp time. Conversely, when the subject knows
that he is going to have a relatively quick g.rasp time, he
has a tendency to let up on the Reach component. Goodwin
obtained almost identical results (10). He found that
Reach time was slowest for the two ounce weight and fastest
for the eight ounce weighr.
Grasp: The three levels of weight of workpiece were
all significant on the Grasp time. This is shown in Fig
ure 25, page 54. The fastest Grasp time was for the .01
lb. weight. The next fastest time v/as for the .45 lb.
weight and the .90 lb. weight was the slowest. The reason
for this result is that it v/as physically much easier to
grasp and gain control of the lighter weights. As was ex
plained above, the Grasp time appears to have a definite
effect on the Reach tim.e.
Position: The .45 lb. weight produced the fastest
Position timiC; however, there v/as no significant differ
ence between that and the Position time for the .01 lb.
weight. The Position time for the .90 lb. weight was
59
significantly longer. These results are portrayed in Fig
ure 27, page 55. The reason that the .90 lb. weight gave
the slowest Position time was that the subjects had much
m.ore difficulty in manipulating the heavier weight for the
minute movements required to position it than they did for
the two lighter weights.
Total Time: The effect of the weight of the workpiece
on the total time followed quite closely the effect on Posi
tion time. The fastest total time was achieved with the
.45 lb. weight; however, this was not significantly differ
ent from, the .01 lb. weight. The total time for the .90
lb. weight was again significantly longer. There appears
to be a critical weight somewhere between the .45 lb, and
.90 lb. v/here the time to complete the task increases sig
nificantly. The Duncan Multiple Range Test on the m.eans
of the total time is presented in Figure 29, page 56.
Subjects
The effect of the subjects on the elemental compon
ents of motion was highly significant with the exception
of the Grasp time. This was an expected result and it
indicates that the individual subjects differed widely
in their ability to perform the task. The non-significant
60
effect on Grasp timie would seem to indicate that there is
not much room for variance in the execution of that com
ponent. Any further consideration of the effect of sub
jects on the elemental components of motion is deemed
beyond the purpose and scope of this experim.ent. There
fore, the discussion of the significant main effects will
be concluded.
Siqnificant Interactions
The only significant interactions which resulted from
this investigation were those of angular direction, visual
discrimination, and weight of workpiece interacting with
the effect of subjects. This merely indicates that the
three main effects had a v;idely varying influence on the
individual subjects. Graphs of these interactions are in
cluded in Appendix C. For the same reason given for the
effect of subjects on the components of motion, any further
discussion of the effect of these interactions is deemed
unnecessary and without merit.
The conclusions and recommendatioris resulting from
this experiment are presented in the next chapter.
CHAPTER V
CONCLUSIONS AND RECOMI-IENDATIONS
This experiment investigated the effects of the inde
pendent variables, angular direction, visual discrimination,
and weight of the workpiece, on -che times of the elemental
components of motion for a simple assembly task. The de
pendent variables measured in the experim.ent v/ere the tim.es
for the elemental components. Reach, Grasp, Move, and Posi
tion, and the total times required to perform, th.e task.
Only right-handed usbjects were used in the experiment and
they were all of the male sex.
The conclusions which are presented below are based
on the results which were discussed in Chapter IV. In
formulating the conclusions, most of the emphasis was
directed toward the effect that an independent variable
had on the components of motion. Each of the independent
variables will be discussed separately.
Conclusions
Angular Direction
The fastest Reach and Move times were produced by the
movement in the 45 degree direction. This agrees with
61
62
previous research which studied these two variables. It
was also noted that the advantage of the 45 degree move
ment was diminished in the Move component. Ihis was due
mainly to the fact that moverrents toward the body are
slower than movements away from the body. However, the
addition of the weight of the workpiece probably contrib
uted to this. An interesting conclusions to be noted here
is that, although the times of the elem.ents Reach, Grasp,
and Move were significantly affected by the direction of
movement, the total time of the task remained unaffected.
In other words, it made no difference, as far as the total
time of the task v/as concerned, as to where the parts were
located on the worktable.
Probably the miost noteworthy conclusion to be drawn
f.romi this part of the experiment is the fact that a pre
ceding element can have a definite effect on a follov/ing
element. This occurred in the times required for the
Grasp component. Wlien the Reach tim.e was the fastest,
the Grasp time was the slowest; and when the Reach time
was the slowest, the Grasp time was the fastest. Evi
dently, the Reach element had a reverse effect on the
Grasp element.
63
Visual Discriminat_2r>n_
Visual discrimination had no significant effect on
either the Reach comiponent or the Position comtponent.
However, it v/as highly significant on the Grasp and Move
components and on the total tim.e of the assembly task.
As the complexity of visual discrimination increased, the
Grasp, Move, and total times increased. This portion of
the research again demonstrated that a preceding element
of motion can affect the following element of m.otion.
This v/as shovm by the result that the .Move time for dis
crimination at both the parts-supply area and target area
was significantly longer than that for discrimination at
the target area; when, in actuality, the motions required
to perform, the Move component was identical in both cases.
What was affecting the Move time v/as that, under the con
dition of discrimination at both areas, the subject was
required to discriminate during the Grasp component, lliis
caused the Move time to be longer than in the case where
the subject did not have to discriminate during the Grasp
element.
Another conclusion that can be drawn from this research
is that the conditions of visual discrim.ination at the
64
-.r J.
target area and visual discrimination at the parts-suppl
area had no significantly different effect on the times
of the elemental components of the assembly task.
Weight of Workpiece
The independent variable, weight of the workpiece,
had a highly significant effect on all the components of
motion with the exception of the Move time. The reason
for this non-significant result may have been that the
weights were not large enough to substantially change the
center of gravity of the arm and thereby produce a detect
able difference in the Move time. This is certainly an
area for future research..
For the component Reach, tlie time v;as slowest for
the .01 lb. weight and was fastest for the .45 lb. weight.
The time for the .90 lb. weight was slightly higher than.
that for the .45 lb. weight. There seems to be a weight
betw^een ,01 lb. and .45 lb. where the time for Reach de
creases significantly. For the component Position and
the total time, the .45 lb. weight produced the fastest
tiiTies although this was not significantly different from
the times resulting from, the .01 lb. weight. There appears
to be a critical weight between .45 lb. and .90 lb. where
65
the time required to perform the Position component and
the total t.ime increases dramatically.
A miost significant conclusion to be drawn from the
effect of weight of workpiece on the elemental com.ponents
is that a follov/ing element can affect a preceding ele
ment. This v/as seen in the analysis of the Reach and
Grasp times. The Reach timie was longest for the .01 lb.
weight and fastest for the .45 lb. and .90 lb. weights.
Logically speaking, this effect should have been insig
nificant since the weight of the workpiece was not involved
in the Reach component. A look at the Grasp time revealed
that the .01 lb. weight produced the fastest time, .45 lb.
next fastest, and .90 lb. the slowest. It appears that
the subject's knowledge of the Grasp time was affecting
his Reach time. When he knew that the Grasp tim.e was
going to be slow, his Reach time decreased; and when he
knew that the Grasp time was going to be relatively fast,
his Reach time increased.
Summary
It has been shov/n by this research that some kind of
interrelationships exist between the elemental components
of motion. It v/as demonstrated that a preceding element
bo
can influence a follov/ing element and that a following
element can have an effect on a preceding element.
As a result of this study, it can be concluded that
angular direction had a definite effect on the times for
the Reach, Grasp, and Move comiponents of motion. Hov/ever..
angular direction had no significant effect on the total
time of the task. This was due mainly to the opposite
effect on the Reach and Grasp components. The variable,
visual discrimination, had a significant influence on the
times for the Grasp and Move components as well as on the
total time of the task. Weight of the wcrkpiece affected
the times of the elements. Reach, Grasp, and Position, and
the total time of the task.
As far as the particular task used in this research
is concerned, this experiment tends to validate the posi
tion taken by predetermined time systems that angular
direction of movement has no effect on the total timie.
However, this may not be the case for a different task.
It appears that predeterm.ined time systems may be in error
by-omitting any contributions to total time due to the
factors of visual discrimination and we.ight of the work-
piece (below two pounds).
67
Recoramendations fp^.j;jirth£^_Research
Although a great deal of research has been conducted
in the area of time and motion study, miany questions re
main unansv/ered in regard to the effect of certain variables
on the elem.ental components of motion and in regard to the
interrelationships of these components. The following sug
gestions are considered worthy of future study:
1. It was noted that weight of the workpiece had a
non-significant effect on the Move comiponent. It would be
interesting to determine at what level weight of the work-
piece does become significant. Also, weights in the range
of one to two pounds should be considered and the physio
logical cost of work should be measured.
2. A. most interesting extension of this research
would be an investigation to determine exactly how the
components i each and Grasp influence one another, when
under the effect of the variables, angular direction of
iTiOveinent and v/eight of the workpiece.
3. This experiment utilized a one-handed assembly
task. A st'jdy using a similar task, but involving both
hands would prove worthwhile. It would be interesting to
see hov/ this would affect the individual components of
motion.
68
4. This study v/as concerned only v/ith the assembly
of workpieces in a two dimensional plane. A most worth
while extension of this work v/ould be to perform the task
in three dimensional space.
5. Finally, another area for farther research would
be to investigate the effect of various levels of illumi
nation on the times of the elements of m.otion, using the
same task that was perform.ed in this experiment.
LIST OF REFERENCES
1. Ayoub, M. M., Effect of Weight and Distance Traveled on Body Member Acceleration and Velocity for Three-Dimensional Moves. Unpublished Doctoral Dissertation, State University of Iowa, 1964.
2. Barnes, R. M. , Motion and Time Study, John Wiley and Sons, Inc., New York and London, 1964.
3. Block, S. M., "Semtar, Automatic Electronic Motion Timer," The Journal of Industrial Engineering, Vol. XII, No. 4, July - Aug. 1961, pp 276-288.
4. Brown, J. S. and Slater-Hammel, A. T., "Discrete Movements in the Horizontal Plane as a Function of Their Length and Direction", Journal of Experimental Psychology, Vol. 39, 1949, p 84.
5. Davis, R. T., Wehrkamp, R. F., and Smith, K. U., "Dimensional Analysis of Motion: I Effects of Laterality and Movement Direction", Journal of Applied Psychology, 1951, Vol. 35, p 363-366.
6. Ellis, D. S., "Speed of Manipulative Performance as a Function of Work-Surface Height", Journal of Applied Psychology, Vol. 35, pp 289-296.
7. Floyd, V!. F., and Welford, A. T, (editors). Human Factors in Equipment Design, K. K. Lewis and Co., Ltd. , London, 1954.
8. Pogel, L. J., Biotechnology: Concepts and Applications, Prentice-Hall, Inc., Englewood Cliffs, N. J., 1963.
9. Franz, D., and Nadler, G., "New Measurements to Determine the Effects of Task Factors on Body MemJaer Acceleration Patterns", Journal of Industrial Engineering, Vol. XII, 1961, p 317.
69
70
10. Goodwin, H. M., The Determination of an Optimal Work Area in the Horizontal Pl nf . Unpublished M.S. Thesis, Texas Technological College, Lubbock, Texas, 1964.
11. Harris, S. j., Smith, K. U., "Dimensional Analysis of Motion: V, An Analytic Test of Psychom.otor Ability", Journal of Applied Psychology, 1953, Vol. 37, pp 136-142.
12. Harris, S. J., and Smith, K. U., "Dimensional Analysis of Motion: VII, Extent and Direction of Manipulative Movements as Factors in Defining Motions", Journal of Applied Psychology, 1954, Vol. 38, pp 126-130.
13. Hecker, D., Green, D., and Smith, K. U., "Dimensional Analysis of Motion: X, Experimental Evaluation of a Time-study Problem." , Journal of Applied Psychology, 1956, Vol. 40, pp 220-227.
14. Hicks, C. R. , Fundamental Concepts i.n the Design of Experiments, Holt, Rinehart and Winston. New York, 1964.
15. Honeycutt, J. M., Jr., "Comments on 'An Experimental Evaluation of the Validity of Predetermined Elemental Time System'", The Journal of Industrial Prngineering, Vol, XIII, May-June 1962, pp 171-172.
16. Maynard, H. B., Stegemerten, G. T., and Schwab, J. L., Methods-Time Measurement, McGraw-Hill Book Co., Inc., New York, 1948.
17. McCormick, E. J., Human Factors Engineering, Reinhold Publishing Corp., New York, 1965.
18. McEIhannon, Virgil B., An Analysis of the Center of Gravity of the Arm During Certain Simulated Industrial Movements, Unpublished M.S. Thesis, Texas Technological College, 1966.
19. Murre11, K. F. H., Human Performance in Industry, Reinhold Publishing Corp., New York, 1965.
71
20. Quick, J. H., Duncan, J. H., and Malcolm, J. A., Work-Factor Time Standard?^, McGraw-Hill Book Co., Inc., New York, 1962.
21. Rubin, G., VonTrebra, R., and Smith, K. U., "Dimensional Analysis of Motion: III, Complexity of Movement Pattern", Journal of Applied Psychology, Vol. 36, 1952, pp 272-276.
22. Schmidtke, Heinz, and Stier, Fritz, "An Elxperimental Evaluation of the Validity of Predetermined Elemental Time Systems", The Journal of Industrial Engineering, Vol. XII, No. 3, May-June, 1961, pp 182-203.
23. Simon, J. R. , and Sm.ader, R. C. , "Dimensional Analysis of Motion: VIII", Journal of Applied Psychology, Vol. 39, 1955, pp 5-10.
24. Smader, R., and Smith, K. U., "Dimensional Analysis of Motion: VI", The Journal of Applied Psychology, Vol. 37, 1953, pp 308-314.
25. Smith, K. U., and Wehrkamp, R. A., "Universal Motion Analyser Applied to Psychomotor Performance", Science, Vol. 113, 1951, pp 242-244.
26. Tichauer, E. R. , "Humian Capacity, A Limiting Factor in Design", The Institution of Mechanical Engineers Proceedings 1963-64, Vol. 178, Part I, No. 37.
27. Tichauer, E. R., Mitchell, R. B., and Winters, N. H, , "A Comparison Between the Elements 'Move' and 'Transport' in MTM and V7ork Factor", Microtecnic, Vol. XVI, No. 6, Dec. 1962, pp 246-251.
28. VonTrebra, Patricia, and Smith, K. U., "Dimensional Analysis of Motion: I.V", Journal of Applied PsychpJ-_-ogy. Vol. 36, 1952, pp 348-353.
29. Wall, W. R., Kinesiological Analysis of a Simple Assembly Task, Unpublished M.S. Thesis, Texas Technological College, 1967.
72
30. Weh.rkamp, R. , and Smith, K. U. , "Dimensional Analysis of Motion: II", Journal of Applied Psycholocrv, Vol. 36, 1952, pp 201-206.
APPENDIX A
ANOVA PROGRAxM
73
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APPENDIX B
MEANS OF SIGNIFICANT MAIN EFFECTS AND INTERACTIONS
77
MEANS OF SIGNIFICMTT MAIN
EFFECTS AND INTERACTIONS
(All values in milliseconds)
78
Source
Reach
Means for
Grasp Move Total Cycle
Position Time
Angular Direction
0^ 450 90°
135° 180°
285.4 237.0 292.1 291.3 295.8
284.4 299.0 265.9 263.1 260.5
460.9 443.9 467.3 474.9 477.3
Visual Discrimination
None Target Supply Both
Weight of
.01 lb.
.45 lb.
V7orkpiece
297.3 270.0
259.9 272.0 281.2 285.3
237.4 281.3
434.0 474.1 462.2 489.2
1246.2 1322.9 1323.4 1361.7
.90 273.7 305.1
286.1 283.6 310.5
1293.0 1288.7 1359.0
Subjecrs
1 2 3 4
• 282.6 318.0 259.1 261.6
527.2 462.7 394.6 475.0
311.7 422.0 258.6 181.2
1397.3 1482.9 1189.3 1184.8
79
Source Means for
Total Cycle Reach_ Grasp Move Position Time
Angular Direction by Subjects
0° 1 295.3 1398,6 1502.0 1219.3 1174.6
45° 1 234.0 1393.6 1445.4 1119.7 1127.4
90° 1 272.1 1343.7 1494.3 1165.5 1241.2
135° 1 296.3 1407.4 1486.9 1185.2 1208.5
180° 1 315.4 1443.1 1485.8 1256.8 1172.3
Visual Discrimination by Subjects
None 1 277.5 2 306.8 3 245.7 4 270.7
1 2 3 4
1 2 3 4
1 2 3 4
1 2 3 4
1 2 •3
4
2 9 5 . 3 3 3 1 . 9 2 6 0 . 2 2 5 4 . 3
2 3 4 . 0 2 7 8 . 5 2 1 1 . 7 2 2 3 . 0
2 7 2 . 1 3 4 2 „ 5 2 6 8 . 2 2 8 5 . 5
2 9 6 . 3 3 1 7 . 1 2 6 5 . 8 2 8 5 . 9
3 1 5 . 4 3 1 9 . 9 2 8 9 . 4 2 5 8 . 5
o 0
Source Means for
Total Cycle Reach Grasp Move Position Time
Target 1 2 3 4
Supply
Both
1 2 3 4
1 2 3 4
Weight of
.01
.45
.90
lb. 1 2 3 4
lb. 1 2 3 4
lb. 1 2 3 4
275.7 308.7 260.2 262.2
286.8 331.2 262.3 267.0
290.5 325.2 267.9 246.6
Workpiece
•
by Subj
243.6 231.5 242.9 231.5
278.8 289.8 293.6 263.1
303.1 313.9 294.5 308,8
ects
517,0 460,8 412.2 495.2
509,8 460.9 388.7 455.1
554.7 466.5 382.9 474.5
1368.2 1431.5 1199.7 1172.6
1352.0 1485.4 1177.0 1140,6
1471.7 1531.8 1191.2 1241,3
APPENDIX C
GRAPHS OF SIGNIFICANT SUBJECT INTERACTIONS
81
82
350
m c o u d) m -H rH H -H
0)
B •H EH
325
300
275
250
225
200
0 Subject #1
EI Subject #2
A Subject #3
O Subject #4
0 o 45° 90 \
o I
135° ±
180°
Angular Direction
Figure 30. Effect of Angular Direction by Subjects on Reach Time
83
1600 r
1500
w 1400 c o u
0)
f—I
jg 1300
•H EH
1200
1100 - ^
O Subject #1
13 Subject #2
A Subject #3
O Subject #4
L OO 450 90° 135°
— j . _
180°
Angular Direction
Figure 31. Effect of Angular Direction by Subjects on Total Time
350
325
CQ
o u <u
-H
5 £ •H EH
300-
275
250
225
i ± X—. None Target Supply
84
O Subject #1
B Subject #2
A Subject #3
Q Subject #4
.. L__ Both
Level of Visual Discrimination
Figure 32. Effect of Visual Discrimination by Subjects on Reach Time
^c-^A. rSl
85
325
300 CQ
c u Q) CQ
- H
•H 275
0) B •H EH
250
225
J- L
O Subject #1
• Subject #2
A Subject #3
0 Subject #4
01 lb. 45 lb 90 lb.
Figure 33
Weight of Workpiece
Effect of Weight of Workpiece by Subjects on Grasp Time
86
600
550
CQ
c 8 500 0) en •H f-i
r-\
(D 450 B •H EH
400
350
O Subject #1
Q Subject #2
A Subject #3
Q Subject #4
01 lb. "45 lb. _l
,90 lb.
Weight of Workpiece
Figure 34. Effect of Weiglit of Workpiece by Subjects on Move Time
87
1600
1500
CQ
C o u o CQ
•H
1400
c B '^ 1300
1200
1100
„1-
O Subject #1
CJ Subject #2
A Subject #3
O Subject #4
. _ ) -
01 lb. 45 lb. .90 lb,
Weight of Workpiece
Figure 35. Effect of Weight of V/orkpiece by Subjects on Total Time
APPENDIX D
SCHEMATIC DIAGRAMS OF ELECTRICAL CIRCUITS
88
89
'—lf-1
yTh
' —^WVA V
hc
bziz
! %-
^ ^ -
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r I I L „
c 1 I
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Figure 36. Schematic Diagrams of the Component Assembly Task Analyser (CATA)
top related