/

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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r H 1—1 rH f-J r H - - • r e

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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o

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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)