11/20/2016
Final Report
Work and Time Study
Team C members:
Huỳnh Hoàng Duy - 12273 (Team Leader)
Vũ Đức Nguyên – 12329
Hồ Thanh Tùng – 11258
Nguyễn Hồng Phước – 12519
Ngô Quốc Dũng - 11275
Team C
WORK STATION 5 AND 6
Contents
1.
Abstract................................................................................................................................................. 3
2.
Introduction .......................................................................................................................................... 3
3.
State of Art (Background) .................................................................................................................... 3
4.
Method ................................................................................................................................................. 3
5.
4.1
Stopwatch time study (STS) ......................................................................................................... 3
4.2
Process Analysis ........................................................................................................................... 3
4.3
Performance rating ...................................................................................................................... 4
Time Measurement .............................................................................................................................. 4
5.1
Work station 5 – Soldering red wire section and green wire section to raw motors ................ 4
5.1.1
Summary of Work Station 5 ................................................................................................. 4
5.1.2
Operational sequences......................................................................................................... 6
5.1.3
The result .............................................................................................................................. 6
5.1.3.1 Evaluation of stopwatch time study ................................................................................ 6
5.1.3.2 The result analysis ............................................................................................................ 7
5.1.4
5.2
Discussion of Work Station 5 ............................................................................................... 7
Work station 6 – Soldering pre-assembled motors to mini circuit board. ................................. 8
5.2.1
Summary of Work station 6 ................................................................................................. 8
5.2.2
Operational sequences....................................................................................................... 10
5.2.3
The result ............................................................................................................................ 10
5.2.3.1 Evaluation of stopwatch time study .............................................................................. 10
5.2.3.2 The result analysis .......................................................................................................... 10
5.2.4
Discussion of Work Station 6 ............................................................................................. 11
5.2.4.1 Hypothesis ...................................................................................................................... 11
5.2.4.2 Implement ...................................................................................................................... 11
5.3
6.
The Conclusion ........................................................................................................................... 12
Optimization ....................................................................................................................................... 12
6.1
The current process .................................................................................................................... 12
6.1.1
Description.......................................................................................................................... 12
6.1.2
Remark of the writers group .............................................................................................. 13
6.1.3
Time Analysis ...................................................................................................................... 14
6.2
The Solution of Team C .............................................................................................................. 14
6.2.1
New Floor Plan and Description ........................................................................................ 14
6.2.2
Description.......................................................................................................................... 15
6.2.3
Improvement Proposal ...................................................................................................... 15
1
6.2.4
7.
Time Analysis ...................................................................................................................... 16
6.3
Time Comparison........................................................................................................................ 16
6.4
The Conclusion ........................................................................................................................... 17
References .......................................................................................................................................... 17
The Table of Figure
Figure 1.The alternative sequences of Work station 5 ................................................................................. 6
Figure 2. The pie chart of illustrating the percentage of time share of activities at Work station 5 ............ 7
Figure 3. The alternative sequences of Work station 6 .............................................................................. 10
Figure 4. The pie chart of illustrating the percentage of time share of activities at Work station 6 .......... 11
Figure 5. The current whole process is showing the flow of work piece.................................................... 12
Figure 6. The bar chart illustrates the time share of current process ........................................................ 14
Figure 7. The new process had been recommended.................................................................................. 15
Figure 8. The bar chart illustrates all the time measurements after improvement ................................... 16
2
1. Abstract
To apply ‘The Work and time course” in studying the current Fischer lock production line, that design the
new production line with the best efficiency
This report shows stuck-points in the old production line. Based on those, recommendations will be
finding as below structure:
Time measurement
Process optimization
Evaluation and Summary
2. Introduction
Based on the time study, Team C examined the real workflow of the workstation 5 (soldering two wires
to motor), workstation 6 (soldering motor to board) and observed all other workstations.
In the stations 5 and 6, we recorded 20 times for the main manipulation, waiting time and others
interruption. The results were written down to find out the standard time for utilization.
During the project, we discussed to establish a new layout of the whole process that may be able to
balance the duty cycle and reduce the waiting time as lowest as possible.
Hence, we could build the time measurement pages and suitable optimization for the available
infrastructure, standard time and qualified factory employees.
3. State of Art (Background)
Line balancing is the process of assigning tasks to workstations, so that workstations have approximately
equal time requirements. We use line balancing to
-
Minimize idle time
-
Balance bottlenecks.
4. Method
4.1
Stopwatch time study (STS)
This a work measurement technique for recording the times and rates of working and analyze the data so
as to obtain the time necessary for carrying out a job at a defined level of performance. It is only valid for
the elements of a specified job carried out underspecified conditions. The objective of stopwatch time
study is to determine reliable time standards for all work, both direct and indirect, including allowances
and recovery times.
4.2 Process Analysis
3
Process analysis is a form of technical writing and expository writing "designed to convey to the reader how a
change takes place through a series of stages.
4.3 Performance rating
Based on Westinghouse system, the performance rating (L) of operator had been rated by trackers from
team C. Performance factors had defines as following:
-
Skill: Based on the processing word of operators on-site
-
Effort: Based on the state of practical work
-
Condition: Rated Good with level C
-
Consistency: Rated “Good” with level C.
5. Time Measurement
5.1 Work station 5 – Soldering red wire section and green wire section to raw motors
This step is to solder the motors with red wire section to pole (+) and green wire section to pole (-) on
original motors. And then, these pre-assembled motors would be moved to the work station 6 – Soldering
to circuit board.
5.1.1
Summary of Work Station 5
Workstation 5 – Soldering red wire, green wire to original motors
List of activities
Type of activity
Solder one head of red wire section to pole (+) and green
Main Activity
section to pole (-)
Time consumption of
activity
459.2
Clean head of solder
Ancillary Activity
6.8
Move all soldered motors into storage box
Ancillary Activity
248
Set up 100 motors onto holding tray
Ancillary Activity
415.7
Repair the error one
Additional Activity
17.9
Covering the local ventilation by carton sheet
Waiting time (relaxing time)
Interruption due to
dysfunction
Interruption due to
personal allowances
13.5
66.7
Time share of activity
37.40%
0.55%
20.20%
33.86%
1.46%
1.10%
5.43%
Total share of processing time
466
37.95%
Total share of time spent for getting/searching parts
663.7
54.06%
Total share of time spent for personal allowances
66.7
5.43%
Total share of time spent for additional activities
17.9
1.46%
Interruption due to dysfunction
13.5
1.10%
4
Solder C1
Ref.
Zy
quant.
mz
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
/n
L
i
ti
t=
L
##
ti
Zeitart
/n
1950
L
ti
95
110
90
90
100
110
90
95
105
90
85
100
85
105
100
95
110
105
95
95
20
23.7
15.9
25.2
25.8
22.3
17.4
25.2
22.7
20
26.3
31
21.4
30
20.7
21.6
22.9
19.4
20.2
23
24.5
459.2
97.50
22.39
tMH
Soldering
red
wire
section to pole (+) and
green wire section to
pole (-)
Release the prepared
motor
22.96
20
F
Release last piece
Set up 100 new motors
onto holding tray
Release last motor
1.3
1.5
1.7
1.1
L
ti
F
248
L
ti
F
415.7
tMN
Move
all
soldered
motors into housing box
1.2
tMN
L
ti
F
tMN
Cleaning the solder at C1
Covering
the
local
ventilation by carton
sheet
End of covering
17.9
L
ti
F
tMS
Release the fixed one
L
ti
F
tMZ
Repair the error one
13.5
212.1
Wait
L
End of waiting time
ti
66.7
F
1228
Ti: Actual individual element times.
TMH: Time of Main activity
F: The progress time.
L: The performance rate
tMP: Time of Interrupted activity due to personal reason
tMP
Nr.
TMN: Time of Ancillary activity
tMZ: Time of Additional activity
tMS Time of Interruption due to dysfunction
5
5.1.2
Operational sequences
Figure 1.The alternative sequences of Work station 5
Alternative sequences had been determined during the measurement. The assigned operator have often
expressed as below:
-
Preparation of 100 motors by setting up onto holding tray to easily position the Anode and
Cathode, that aimed to prevent the event of soldering wrongly the wire colors with the kind of
pole on raw motors. The holding tray is available 100 slots to put 100 motors on one time
-
The assigned operator continue to solder in orderly with that red wire section to pole (+), green
wire section to pole (-)
-
Cleaning the head of solder if necessary
-
Stored the pre-assembled motors to transport box by 20 pc per time.
5.1.3
The result
5.1.3.1 Evaluation of stopwatch time study
Nr.
Workstation 5
Name
Soldering Red wire section to pole (+), Green wire section to pole (-)
Process description
-
Start measurement point
Touching red wire section
End measurement point
Releasing the solder from green wire section at pole (-) on motor
Time per piece
22.39 s
Amount of measurements done
20
Relative confidence
7.1%
Min real value
20.80
Max real value
23.98
Activity done at workstation
5
Measured by team
C1
Taking one red wire section, and then positioning to solder one head to pole (+)
Next is that one head of green wire section had soldered to pole (-).
6
Comments
The amount of measurements needed 42
5.1.3.2 The result analysis
Input
Specified confidence level
Standard deviation of measurements
Mean value of measurements
Number of measurements
Result
Absolute confidence interval
Relative confidence interval
Amount of measurements needed
95%
3.753469
22.83
20
1.645
7.2054
42
The result of workstation 5 is illustrating that as following:
-
The needed time for this step is about 22.83s
-
The amount of measurements needed up to 42 for much more confidence because of been over
5%.
5.1.4
Discussion of Work Station 5
The total time spent for WT 5 mainly come from soldering (38%) and setting up (54%) manipulation. There
are some improvements for this station raised as below:
-
The holding tray have been recommended to narrow down the amount of motors position from
100 to 70. Due to the fact that the female employees have hardly operated on the whole tray.
Therefore, the assigned operators have often separated two parts as setting up on this pattern
and soldering each one. In this case, the female employee on duty had divided 100 motors to 62
pc and 38 pc for each process.
-
The worker at WT 6 could support the setting activity for WT 5 to mitigate the work time of WT5.
-
The stuff and tools such as lead wire, wire tray should be fixed to easily reach and prevent risks.
2% 1%
Total share of processing time
5%
38%
Total share of time spent for
getting/searching parts
Total share of time spent for personal
allowances
54%
Total share of time spent for
additional activities
Other
Figure 2. The pie chart of illustrating the percentage of time share of activities at Work station 5
7
5.2 Work station 6 – Soldering pre-assembled motors to mini circuit board.
This step is to solder pre-assembled motors from WT5 to circuit boards. And then, these soldered motors
would be moved to the next work station: 3 and 8 – Putting motors into the shafts.
5.2.1
Summary of Work station 6
Workstation 6 – Soldering pre-assembled motors to mini circuit board
Activity
Time share of activity
Time share (%) of activity
Get boards
14.63
3.20%
Solder motor to board
286.32
62.66%
Cleaning solder equipment
11.66
2.55%
Go to toilet
99
21.67%
Taking rest of operator due to hot condition
45.33
9.92%
Total share of processing time
312.61
68.41%
Total share of waiting time
0
0
Total share of time spent for getting/searching parts
14.63
3.20%
Total share of time spent for personal allowances
144.33
31.59%
Total share of time spent for additional activities
0
0
Total share of time spent for recovery
Other
Activities
Get board
Solder motor to
board
Cleaning solder
equipment
Available
for task
Yes
Executing a
Direct task
Planned
task
fulfillment
Yes
Yes
No
Due to Due to
cycle
dysfunction
-
Type of activity
Ancillary activity
Yes
Yes
Yes
Yes
-
-
Main activity
Yes
Yes
Yes
No
-
-
Ancillary activity
Go to toilet
Yes
No
No
-
-
No
Taking rest of
operator due to
hot condition
Yes
No
No
-
-
No
Interruption due
to personal
reasons
Interruption due
to
personal reasons
8
Zy
Ref.
quant. mz
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
L
ti
1999
Solder motor
to board
1
Release
motor
board
t=
L
100
ti
Tim
e
Solder
C2
&
L
ti
94
83
13.48 11.83
93
13.36
108
112
93
97
100
110
84
112
100
95
114
91
93
108
112
93
15.42
16.10
13.34
13.92
14.25
15.76
12.00
16.05
14.33
13.61
16.39
13.00
13.36
15.42
16.10
13.34
107
20
15.26
286.32
F
20
99.97
14.31
14.32
tMH
Nr.
100
2
Release
boards
L
100
ti
14.63
100
1
14.63
14.63
14.63
F
tMN
Get board
1
402.39
Cleaning
solder
3 equipment
L
ti
97.17
3.00
100.6
113.87
98.8
1
92.54
4
2.56
2.95
3.15
11.66
2.93
tMN
2.92
F
4
100
4
Go to
toilet
100
L
100
1
ti
99.0
99.0
99.00
99.0
F
tMP
1
445.32
L
188.89
50.3
7
ti
24.0
90.0
148.44
206.06
22.0
3
136
F
67.29
3
Ti : actual individual element times.
tMH : time main activity
F: the progress time.
L: the performance rate
tMP : time interrupted activity due to personal reason
tMP
Taking rest of
operator due
to
hot
5
condition
tMN : time ancillary activity
t : normal time
9
5.2.2
Operational sequences
Figure 3. The alternative sequences of Work station 6
5.2.3 The result
5.2.3.1 Evaluation of stopwatch time study
No.
2
Name
Soldering prepared motors to circuit board
Process description
First
of
all,
about
25
circuit
boards
were
put
on
worktable.
Next
to
pick
one
board,
then
picking
one
prepared
motor.
- Soldering the head left of red wire section to pole (+) at board, then rounding motor 90 degrees.
- Continuing to solder the head left of green wire section to pole (-) at board.
Start measurement point
Picking circuit board
End measurement point
Releasing the solder from green wire section at pole (-) on board
Time per piece
14.32
Amount of measurements done
20
Relative confidence
4.3%
Min real value
13.70
Max real value
14.94
Activity done at workstation
5
Measured by team
C2
Comments
Work Station 6
5.2.3.2 The result analysis
The result of workstation 6 is illustrating that as following:
Input
Specified confidence level
95%
Standard deviation of measurements
1.404
Mean value of measurements
14.32
Number of measurements
20
Result
Absolute confidence interval
0.615
Relative confidence interval
4.298%
Range of real mean value
13.70≤t≤14.94
10
Because the relative confidence interval is less than 5% (4.298%) so it does not need to increase the
quantity of replication.
5.2.4
Discussion of Work Station 6
5.2.4.1 Hypothesis
As the percentage of time share of activity, time spent for personal allowances accounted for 31.59%,
meaning that it’s significant and affected the efficiency of work station 6 because operators took rest
without permission of supervisor and arbitrarily stopped working due to hot condition although the room
atmosphere is not too hot with the support of fans and air conditioner. The arm of hypothesis is how to
reduce the time of interrupted activity and it was showed as below.
The first interruption due to personal reason is the time of going to toilet. The hypothesis for this activity
is that if the worker plan to go to the toilet as group, particularly the workers those who perform as 2
stations next together, the interrupted times could be reduced and change to recovery time.
The second interruption due to personal reason is the time for taking rest due to hot condition although
air conditioner is already installed, the company could limit it in 2 ways. Once, installing new fans and air
conditioner to decrease the room temperature. Other, managing the workers more strictly by policies of
company and supervising
Total share of processing time
31%
Total share of waiting time
Total share of time spent for
getting/searching parts
66%
3%
0%
Total share of time spent for personal
allowances
Figure 4. The pie chart of illustrating the percentage of time share of activities at Work station 6
5.2.4.2 Implement
Base on the overall observation in the company. Team C had recognized the loose management of the
supervisor and almost activities lack the control. The recovery time also is unscheduled which is related
to the spontaneous activity of workers so that making the schedule for recovery time and controlling
strictly the personal activities is the top priority of the project if company want to improve the efficiency.
Worker could go the toilet but they need to inform the supervisor, co-workers and follow the recovery
11
schedule. They cannot go without the permission. For example, they could go to the toilet at beginning
and the ending of shift, in process, they need to inform the supervisor
As the company aspect, investing to facility to improve the efficiency could be meaningful if the factor
(time for interrupted activity) affects dramatically to production and slowdowns the speed of production,
but if the efficiency is not much improved, the company has to consider this solution. Therefore, in case
of room condition, company should not change or improve the facility to reduce the time of action
interrupted due to hot atmosphere. Because it will cost the company’s budget and also time greatly
instead of they can improve the management skills of supervisor and control workers more tightly to edge
the complain of workers
5.3 The Conclusion
The efficiency rate has chance to improve up to 90% for work station 5 and 6 in theory. The new
approaches once applying in practical production line that would mitigate the current waiting time and
increase the processing work time.
6. Optimization
6.1 The current process
Figure 5. The current whole process is showing the flow of work piece.
6.1.1
Description
The current process have started at WT 5. Dedicated worker have picked up a motor and soldered a red
wire and a green wire section to the motor.
12
Then, WT 6 would be received the motor and soldered it to the board and sent all to WT 3.
At WT 3, the motors would be put on a shaft. Beside, worker at WT 4 inserted nine buttons into housing.
The workers at WT 3 and WT 4 have sent their shafts and housings to worker 2 to assembly. Then, WT 10
must test them and mark by laser machine.
Worker 7 does the same job with worker 4 while worker 8 puts motor on shaft with help of equipment.
Then, they have sent their work pieces to WT 9 to assembly before worker 10 tests them and mark by
laser machine.
WT 1 is a preassembly step
The process finishes and all products will be taken out. The lead time is about 80 seconds.
6.1.2
Remark of the writers group
The cycle time is the main time of WT 2, nearly 80s. This value is much more than main times of other
WTs, it has makes a lot of waiting time in the process.
Workstations located at illogical position. For example, work pieces from WT 6 must move to WT 3, which
is not next to WT 6. Worker 4 also has to send her work pieces to worker 2.
Worker 9 and worker 2 have the same mission, but worker 9 uses machine equipment, it takes her nearly
46 seconds to finish while manual skills of worker 2 take her 80 seconds.
In addition, materials are storage beside workstation 6 instead of worker 5 while workstation 5 is the first
step of this process.
Images 1. The current process
13
6.1.3
Time Analysis
90
Manual Screwdriver
80
79.84
70
Same function, same
quantity of tasks but
differenct time use
60
Screwdriver m/c
50
40
30
20
10
0
5
6
1
3
8
2
9
4
7
10
Figure 6. The bar chart illustrates the time share of current process
The lead time is 79.84s
The waiting time is based on every steps and analyzed generally, as below:
∑ 𝐴𝑙𝑙 𝑙𝑖𝑛𝑒 𝑡𝑖𝑚𝑒
∑ 𝑊𝑜𝑟𝑘 𝑡𝑖𝑚𝑒
=
∑ 𝑀𝑎𝑖𝑛 𝑙𝑖𝑛𝑒 𝑡𝑖𝑚𝑒
∑ 𝑊𝑜𝑟𝑘 𝑡𝑖𝑚𝑒
35.06+51.2+55.04+32.32+46.89+34.42+42.35+43.67+49.27
789.4
=
390.22
789.4
=
35.06+51.2+55.04+32.32+46.89+34.42+42.35+43.67+49.27
552.58
=
= 49.43%
390.22
552.58
= 70.62%
6.2 The Solution of Team C
The writers group is of opinion that the key priorities for improvement of current process as following:
-
Using every current resources
-
“Simple is the best”
-
Applying outstanding approaches of time study subject.
The approaches have been utilized such as Process analysis to rearrange the current layout; Stopwatch
time study to evaluate all kinds of time consumed in the production line as a whole; …
6.2.1
New Floor Plan and Description
14
Figure 7. The new process had been recommended.
6.2.2
Description
Starting point: Work station 5 (WT)
Work station 5: The assigned operator on duty would take input material from storage shelf and do its
function.
Work station 6: Taking work piece from WT5, doing its tasks and supporting WT5 such as setting up motor
onto holding tray by Anode, Cathode to save time.
Work station 1: Doing its tasks, delivering the work piece from WT6 to WT3, 8.
Work station 2, 3, 4 – 7, 8, 9: Assembly stage and put on the roller. (Note: Therein, the WTs are same
function that WT 3 - 8, WT 2 - 9, WT 4 – 7)
Work station 10: Getting the work pieces on the roller, checking buttons, returning error one to WT 2, 9;
doing its task such as testing, operating laser marking machine.
End point: Finished goods from WT 10 would be stored at dedicated temporarily box.
All input materials have been temporarily stored on shelf, they come from Storage.
6.2.3
Improvement Proposal
Swapped position between WT 5 and WT 6 because the starting point is at WT 5 and in order to easily get
raw motors from temporarily house shelf on the above right corner.
Invested new screwdriver machine to automatic operate at WT 2 to increase the performance efficiency.
Standardized the time for WT3 and WT 8 to encourage their two assigned operators perform efficiently.
15
Reposition of WT 1 to center of the work area, and then allocate this employee getting one more function
as delivery person to facilitate the flow material such as:
-
Bring output of WT 6 to WT 3, 8
-
Support to return the error work pieces from WT 10 to WT 2, 9.
Reposition of WT 10 next to WT 1 to get the output of WT 2, 9 for testing and operating the laser marking
machine. Besides that, this employee would be assigned to take responsibility for “checking buttons”,
instead of the station of 2 and 9 - Putting soldered motors into shaft must do it.
Fixed all material boxes on the production line such as: Lead wire tape, electrical wire tray, circuit board
tray at WT 5, 6 and so on. The reason is to easily find out work pieces and to prevent the event of falling,
missing.
6.2.4
Time Analysis
Using new
screwdriver m/c
45
40.2
40
35
30
Checking buttons
task from WT 2, 9
25
20
15
10
Support for 02
assembly lines
5
0
5
6
1
3
8
2
9
4
7
10
Figure 8. The bar chart illustrates all the time measurements after improvement
The lead time is 40.2s
The waiting time is based on every steps and analyzed generally, as below:
∑ 𝐴𝑙𝑙 𝑙𝑖𝑛𝑒 𝑡𝑖𝑚𝑒
∑ 𝑊𝑜𝑟𝑘 𝑡𝑖𝑚𝑒
=
∑ 𝑀𝑎𝑖𝑛 𝑙𝑖𝑛𝑒 𝑡𝑖𝑚𝑒
∑ 𝑊𝑜𝑟𝑘 𝑡𝑖𝑚𝑒
11.6+5.4+3.6+2.7+4+9.6
402
=
36.9
402
=
11.6+5.4+3.6+2.7+4+9.6
281.4
=
= 9.1%
36.9
281.4
= 13.1%
6.3 Time Comparison
16
Unit
Current process
Offered process
Lead time (s)
79.84
40.02
Waiting time (All process) (%)
49.43
9.1
Waiting time (Main process) (%)
70.62
13.1
The current process has low efficiency and logically arranging, that make a plenty of waiting times.
The manual activities would take a long time and high risks of wrong.
The lead time is downing about 39.82s
The efficiency of time spent has increase up to 57.52% (main process), 40.33% (all process).
6.4 The Conclusion
The new production process that may pose some advantages:
-
Mitigated approximately 50% of time per pieces from 79.84s reduced down to 40.2s. It means
that the efficiency of working time raised to 100%.
-
Almost current resources have been used up such as equipment, labor, workplace, and facilities.
-
Not too much invested, just something as one screwdriver machine, separating the table and so
on.
-
Easily training and adapted by factory employees.
7. References
1. Dr.-Ing. Marlene Helfert, 2016. Work and Time Study documents. Vietnamese German University.
2. GPEM 2016 Class, 2016. The result of Time Study. Vietnamese German University.
3. Dr. Allison W. Pearson, 2011. Principles of Management & Production. Mississippi State University.
4. Lecture 9. . [Nov. 19, 2016].
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