This document discusses improving the productivity of an existing production line that manufactures product X through implementing Kaizens (continuous improvements). It analyzes the current production line and identifies reaming as a bottleneck station, taking 52.4 seconds per cycle which is longer than the target 41 seconds. The document proposes replacing the hydraulic cylinder used for the upstroke/downstroke of the fixture in reaming with a smaller diameter cylinder. Calculations show this would increase velocity 4 times and save around 7 seconds per cycle. Implementation of this and other Kaizens could increase productivity by 30% to meet demand.

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IMPROVING THE PRODUCTIVITY OF EXISTING DISC LINE
THROUGH A KAIZEN
S.Sampath Kumar1*
, V.Vignesh2
1*
Professor, Department of Mechanical Engineering, CEG Campus, Anna University, Chennai-600025
2
PG Student, Department of Mechanical Engineering, CEG Campus, Anna University, Chennai – 600025.
Email: ssk@annauniv.edu1*
, vignesh_1610@yahoo.com2
Kaizen, a lean tool which emphasis on smaller but continuous improvements on a production line,
thereby improving the operational excellence and productivity in many industries over the years.
This mainly concentrates on eliminating or reducing the proportion of non-value adding activities
present in each workstation of the production line. This work aims to improve the productivity of the
production line, which manufactures product X by at least thirty percent using Kaizens. A total of
five higher priority Kaizens were found, of which one of the Kaizen is discussed here. The present
time taken for the upstroke and down stroke of the feed cylinder in reaming station constitutes
around fifty percent of the entire work station time. This paper explains the calculations in detail
about how the stroke of the feed cylinder is improved by replacing the higher diameter cylinder with
a lower diameter one without affecting operation characteristics. On replacing the cylinder, the
velocity is improved by four times and a considerable amount of time is saved in the reaming station,
which was one of the bottleneck station. All other Kaizens will be discussed as a future work.
Index Terms—Kaizen, Productivity
I. INTRODUCTION
Automobile has become an essential one to
everyone‟s life. Due to heavier competition,
industries are forced to manufacture cars at lower
cost, higher quality and at quicker pace. Increased
material and labor cost has caused more burden to
the automobile and their ancillary industries. Their
problems are multiplying on day to day basis [1].
The end customers are the most affected, as the
companies force their losses onto them. Though the
cutting edge technology is put in use, still the
problem persists. The companies are trying
different approaches to tackle the problem, one
such approach is the KAIZEN approach [2], which
this work emphasis on. This work is done at an
automobile auxiliary unit, which manufactures
product X and has seven workstation in its
production line.
A) LITERATURE REVIEW
Lean Manufacturing has become a major
revelation among industries, such that they improve
operational excellence, continuous improvement
and the elimination of non-value adding activities
[1].One among the lean tool is Kaizen, which
emphasis on low cost improvement on a continuous
manner [2].This tool brings out complete employee
co-operation, thereby improves teamwork in a firm.
Low cost automation through Kaizen has become
popular among industries, which reduces the cost of
the labour associated to the work [4].Improving the
productivity has been the challenge for many
industries over the years, which Kaizens able to do
it.Study of existing layout through time study needs
accurate results, so as to scale the improvement
needed at each workstations[5].This work able to
concentrate on all aspects from time study to the
implementation of Kaizens, which is discussed in
the coming sections.
B) METHODOLOGY
The following Fig1 summarizes about the detail
methodology followed in this work. The work
started with a detail study of existing layout,
followed by the time study which gives a clearer
image of stations that are bottleneck in the
production line.

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Fig1.Methodology of work
A detailed calculation of present and target
cycle time is calculated so as to find the scale of
improvement needed [6]. Next, Identifying the
areas for Kaizens is done and a best solution is
taken and designed. After designing, required
materials are either purchased or fabricated and
then installed. The installed system is monitored
and feedback is taken from the firm.
C) PROBLEM DEFINITION
The objective of this work was to improve the
productivity of existing production line in order to
meet its demand. The company had some
productivity issues on its Product line .The
Company could produce 398 nos of X per shift
against the demand of 600 nos of X per shift. The
company‟s interest was to improve the productivity
by eliminating the huge proportion of non-value
adding activity present in its four workstations out
of seven workstation, through Kaizens. Table 1
summarizes detailed production line characteristics
of the production line.
Figure II .Results From Time Study
Figure II represents the results of time study of all
stations. It is clear that the stations such as
Reaming, Boring, De- burring and Marking are
well above the target cycle time.
II. TIME STUDY
Table I represents the production line
characteristics of the line, which gives a clearer
0
20
40
60
CHART REPRESENTING THE OPERATION TIME AT
EACH STATION
Present cycleTime=64
Target Cycle Time = 41
TABLE I
PRODUCTION LINE CHARACTERISTICS
S No Description Data‟s
1 Nature of
production
system
Batch Production
2 Product Disc for wheels
3 Line Name Escol Disc Line
4 Type of layout In-line layout
5 Product variety 38
6 Transfer type Manual
7 Total man
power
07
8 Total number
of work
stations
07
9 Total number
of machines
05
10 Setup time 45 mins
11 Total layout
area
750 sq.ft/

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idea of the existing system.
Time study is a work measurement technique
for recording the time of performing a certain
specific job or its element carried out under specific
condition and for analyzing the data so as to obtain
the time necessary for an operator to carry out at a
defined rate of performance. A detailed time study
was carried out with the help of camcorder and stop
watch.
A detailed calculation of present and target
cycle time is done in coming sections. It is evident
that four workstation (Reaming, Boring, Deburring,
Marking) are well above the target cycle time of 41
sec from figure II. So our utmost concentration lies
on those stations first. This work concentrates only
on reducing the operation time in Reaming station
alone.
1) OPERATION AT THE REAMING STATION
Table II represents the list of activities
performed and their average time at reaming
station. It is clearly evident that the activities A.3
and A.5 have huge proportionate of time as against
other activities performed at the same station.
These activities alone constitutes 35 % of total
workstation time. In here, VA represents Value
Added Activities, NVA represents Non Value
Added Activities, NVA (PT) represents Non Value
Added Activities with present technology. A
detailed time study results are represented here.
III) CALCULATIONS OF CYCLE TIME
In this section, we will be discussing about the
calculations of cycle time from the time study data
and target cycle time needed to achieve the
production rate. This clearly indicates the
workstation that needs improvement and scale of
improvement that has to be implemented.
Cycle time is defined as the maximum time that
one work unit spends at a station. It is the time
between when one work unit begins processing and
when the next unit begins the cycle, Tc is the time
a component spends at a workstation. Now we will
discuss the calculation of present and target cycle
time in the coming section.
1) CALCULATIONS OF PRESENT CYCLE TIME
Cycle time (Tc) = To+Th+Tth (1)
(To=Actual processing Time (min/pc),
Th=handling time (min/pc),
Tth=Tool handling time (min/pc)
Eq (1) can be generalized to most processing
operations in manufacturing.
Assuming Tth=0 in Eq(1)
Tc.=Max (To+Th)=60+4
(Marking station has highest time =60sec)
= 64 sec/pc (1.066min/pc) (2)
1.1) TO FIND TP AND RP FOR BATCH PRODUCTION
Batch processing time (Tb) =Tsu+ (Q*Tc) (3)
(Tsu=Setup time for the batch, Q=Batch Quantity)
Substituting Tc from Eq(2)
Tb= 45+ (400*1.06)
(Setup time=45mins, Batch Quantity=400)
Tb = 471mins (4)
Avg Prod. Time (Tp) = Tb/Q (5)
TABLE II
PRODUCTION LINE CHARACTERISTICS
Task
ID
Activity VA/NVA Avg
Time
(Sec)
A REAMING
A.1 Taking disc from
palette and
keeping on lifter
NVA(PT) 11.5
A.2 Pushing the disc
from lifter to the
machine
NVA 1.9
A.3 Upstroke of the
fixture
NVA 8.7
A.4 Reaming process
(machining)
VA 11
A.5 Down stroke NVA 7.8
A.6 Cleaning of scrap
on the disc
NVA 4.6
A.7 Pushing the disc
from lifter on to
the conveyer
NVA(PT) 2
ADDITIONAL
Waiting for the
rack pinion
arrangement to
turn
1.9
Allowances 3.04
TOTAL 52.40

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Substituting the values from eq(4),
Tp=471/400 = 1.18mins/pc (6)
Avg.Prod Rate (Rp) =60/Tp (7)
Rp = 51X‟s/hr (8)
Avg .Prod Level = Rp*no of hours
(Rejections not considered)
51*8=408 X‟s/shift (9)
Avg .Prod Level = (Rp*no of hours)-q
(q-No of rejections)
(Rejections Considered)
= (51*8)-10=398 X‟s/shift (10)
The above mentioned calculations clearly states
that the average demand met with existing cycle
time is only 2, 38,800pieces as against the forecast
demand of 3, 60,000 X per year.
2) CALCULATION OF TARGET CYCLE TIME
Company wants to meet the demand of 3, 60,000
discs per year (30,000 p.m.).
On assuming same rejection level,
Required Hourly production Rate (Rpplanned) =
(Da+qa)/ (50 x Sw x Hsh) (11)
Da=Annual demand needed=3,60,000X‟s
(no rejections)
qa=Annual no of rejections=(10*12*50)
=6,000X‟s/year Sw = No of shifts /week = 12
sh= Hours/Shift = 8hr
(Rpplanned)= (3, 60,000+6000)/ (50x12x8)
= 76 X‟s /hour.
Rpplanned=608 X‟s/shift (12)
Tpplanned=60/Rpplanned = 60/76
Tpplanned=0.79min/X (13)
From Eq (5),
Tpplanned=Tbnew/Q= 0.79 =Tbnew/400
Tbnew = 316mins (14)
Assuming that the setup time remains the same,
From Eq (3)
Batch processing time (Tbnew) =Tsu+ (Q*Tctarget)
Tctarget= (Tbnew-Tsu)/ (Q)
= (316-45)/ (400)
Tctarget=0.6775mins=41 secs (15)
It is clearly evident that our target cycle time comes
to be 41sec which is 23sec lesser than the current
cycle time. So it has to be concentrated such that all
the elemental workstation timings should be well
below the target cycle time, so as to achieve the
demand.
III. KAIZEN
Kaizen is a Japanese philosophy for process
improvement that can be traced to the meaning of
the Japanese words „Kai‟ and „Zen‟, which
translate roughly into „to break apart and
investigate‟ and „to improve upon the existing
situation‟. Kaizen means improvement on a
continuous basis involving everyone in the
organization from top management, to managers
then to supervisors, and to workers. In Japan, the
concept of Kaizen is so deeply engrained in the
minds of both managers and workers that they often
do not even realize they are thinking Kaizen as a
customer-driven strategy for improvement.
1) KAIZEN K.H.1
Our first Kaizen was to reduce the upstroke and
downstroke time of the fixture in reaming station as
summarized in table 2.This is considered as higher
priority Kaizen, so it is named as Kaizen K.H.1.Let
us see the upstroke and downstroke activities in
detail in coming section.
1.1) UPSTROKE OF THE FIXTURE
The activity A.3 of this station represents the
upstroke of the fixture, wherein a cylinder of
160mm is used to lift the fixture along with the
product X. The labour actuates the value for the
upstroke of the hydraulic cylinder for each and
every cycle. The pressure of the oil gives a force to
push up the fixture, so as to help the product X
come closer to the reamer tool. This activity takes
around 9 sec to get it completed. The machining is
done as the next step after the upstroke of the
fixture is done. At present a cylinder of bore size
diameter of 160mm is used, which is seen as a
potential area for improvement.
ACTIVITY A.3

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1.2) DOWN STROKE OF THE FIXTURE
ACTIVITY A.5
The activity 5 downstroke of the fixture is
followed by the machining process. Once the
machining process is over, the fixture along with
the product X is downstroked.It takes around 7
seconds for this activity to get completed. This is
seen as the area for improvement, where time to get
the activity completed can be halved if the cylinder
of lesser bore diameter size is used.
1.3) ACTION PLAN
At first, the existing system was completely
studied. A detailed dimension for the feed cylinder
was studied inside, by checking the drawings. We
found that the cylinder of bore size 160mm was
used, which we felt too much for the weight of the
fixture along with the product X. It is evident that
we need more fluid to get filled for the higher
diameter cylinder. Once filled, then the force is
induced by the fluid on the bore, such that the
cylinder actuates as the upstroke process is done. In
reverse, the down stroke of the fixture happens by
the effect of releasing the fluid from the cylinder,
which also takes more time to get emptied.
We found that it is evident to see that the higher
bore size of the cylinder was the case of concern for
this slower process time. Our action plan was to
reduce the bore diameter of the cylinder and
thereby reducing the process time. A detailed
design calculation was done in order to find the
magnitude of reduction needed to achieve the
reduction in process time of this process.
1.4) DESIGN OF CYLINDER
Old cylinder calculation:
Bore diameter of the cylinder = 160mm
pressure of the hydraulic fluid = 5 bar
Vo=Q/Ao (1)
Vo=Velocity of the old cylinder
Q=Flow rate
Ao=Area of cross section for old cylinder
Ao= (π/4) (Do) 2
Sub Ao value to Eq (1)
Vo=Q/ (π/4(Do)2
) (2)
Table III represents the time saved after
installation of the newcylinder.It is clearly seen that
around 7 sec is saved.
New cylinder calculation:
Vn=Q/An (3)
Vn=Velocity of the new cylinder
Q=flow rate
An=Area of cross section for new cylinder
An= (π/4) (Dn) 2
Sub An value in Eq (3)
Vn=Q/ ((π/4) (Dn)2
) (4)
Assuming Vn=4Vo;
So,Vo/Vn=(1/4) (5)
Substituting eq (2) and eq (4) into eq (5), we get
4 Dn2 = Do2
Dn= (Do)/2
Dn=80mm. (6)
The nearest standard dimension is 80 mm Dnc
Festo Cyliner.
It is evident that the velocity of the stroke
increases by 4times, when the diameter of the
bore is reduced by halved.
1.5) FORCE CALCULATION
F=P/A (P=Pressure), (A=Area of the bore)
Old Cylinder
Fo = ((π/4) (Do) 2
) x P
= ((π/4) (0.16)2
) x (5x10 5)
= 10,048 N (7)
New cylinder
Fn = ((π/4) (Dn) 2
) x P
= ((π/4) (0.08)2
) x (5x10 5) = 2,512 N (8)
TABLE III
TIMING OF ACTIVITY A.3 AND A.5 – BEFORE AND AFTER
CYLINDER CHANGE
S.no Activity
Before
(time in
sec)
After
(time in
sec)
1 Upstroke of
fixture
9 5
2 Down stroke of
the fixture
7 4

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Required Force calculation:
Maximum Disc Weight = 35Kg
= 35 x 9.81
= 343 N (9)
Supporting Plate and Fixture Weight = 200 Kg
= 200 x 9.81
= 1962 N (10)
Adding the values (9) and (10)
Total weight to be lifted = 1962 + 343
= 2305 N (11)
On comparing the values (9) and (11), it is
clearly evident that the newer cylinder of 80mm
diameter is capable of lifting the required load.
1.6) INSTALLATION
We could see that there is a possibility
reduction of bore size of the cylinder so as to
reduce the process time. We planned to replace the
existing 160mm bore diameter size cylinder to
80mm bore diameter size. This is a standard size of
the cylinder, such that those were easily available at
the stores. With the help of maintenance
department, we could replace the 160mm diameter
cylinder to 80mm diameter cylinder .We could see
the results to be drastically changed.
We could see that 4seconds are reduced in
the Upstroke activity and a 3 seconds change in
Downstroke activity. In total a 7 seconds reduction
was possible in the reaming station, which is
considered to be a vast improvement.
1.7) DIFFERENCE IN PRODUCTION LEVEL
A detailed comparative study of productivity
data were done before and after installation of
cylinder at reaming station [6].
Time Saved
Upstroke of the cylinder operation = 4 sec
Down stroke of the cylinder operation = 3 sec
---------
=7sec (1)
---------
Workstation Time (Old Time) = 52 sec
= 0.86 min/X (2)
Workstation Time (New Time) = 45 sec
= 0.75 min/X (3)
1.8) OLD TIME FOR REAMING STATION
Batch processing time (Tb) =Tsu+ (Q*Tc)
(Tsu=Setup time for thebatch, Q=Batch Quantity)
Substituting Tc from eq (2),
Tb=45+ (300*0.86)
(Setup time=45mins, Batch Quantity=300)
Tb=303mins (4)
Avg Prod. Time (Tp) = Tb/Q
Substituting the values from eq 4,
=303/300
Tp= 1.01mins/pc (5)
Avg.Prod Rate (Rp) = 60/Tp
= (60/1.01)
Rp = 59 X’s/hr (6)
Rp = 59 * 8
Rp = 472 X’s/shift (7)
1.9) NEW TIME FOR REAMING STATION
Batch processing time (Tb*) =Tsu+ (Q*Tc) (8)
(Tsu=Setup time for the batch, Q=Batch Quantity)
Substituting Tc from Value 3
Tb*=45+ (300*0.75)
(Setup time=45mins, Batch Quantity=300)
Tb*=270mins (9)
Avg Prod. Time (Tp*) = Tb*/Q
Substituting the values from eq 9,
=270/300
Tp*= 0.9mins/pc (10)
Avg.Prod Rate (Rp*) = 60/Tp*
= (60/0.9)
Rp* = 67X’s/hr (11)
Rp* = 67 * 8
Rp *= 536 X’s/shift (12)
1.10) DIFFERENCE IN PRODUCTION LEVEL
Eq (12)-(8) we get,
Rp*-Rp=536-472 = 64 X’s/shift
It is clearly evident that there is a clear
difference of 64 X’s can be produced at the
reaming station, without any changes in
operational characteristics.

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CONCLUSION AND FUTURE WORK
Due to increased customer expectations and
global competition, companies are forced to
improve their productivity at lower cost and still
retain best product quality. This work addresses the
productivity issues with the above said in mind,
such that nearly 7 seconds of total workstation time
is saved. A simple cylinder change of lower
diameter has increased the stroke of the cylinder
such that it has saved about 20 twenty percent of
the workstation time.
The future work will emphasize on solving
other Kaizens which are found in Marking,
Deburring and Boring stations such that
improvements will be smaller in magnitude, cost
effective and in a continuous manner.
IV. REFERENCES
[1] D.Rajenthirakumar& P. R. Thyla (2009),
“Quality and Productivity Improvement in
Automotive Component Manufacturing
Company Using Kaizen”, Journal of
Manufacturing Systems.
[2] R.Radharaman, L.P Godoy &K.I.Watanbye
(2010), “Quality and Productivity Improvement
in a Custom Made Furniture Industry using
Kaizen”, Elseiver Science Limited, S0630-
8352(96) 001775.
[3] Jr. Jung luye (1996), “Applying Kaizen and
Automation in Process Engineering” Journal of
Manufacturing Systems, Vol 15.
[4] MebyMathewa and D.Samuelraj(2013),
“Reduction of Cycle Time Using Lean Tools in
an Automobile Assembly Line”, Proceedings of
the National Conference on Manufacturing
Innovation Strategies & Appealing
Advancements, P.S.G College of Technology.
[5] Takafumi Ueda (1998), “Quality and
Productivity Improvement JICA‟s Kaizen
assistance”, Japan International Cooperation
Agency.
[6] Mikel.P.Groover (2003), “Automation,
Production Systems and Computer Integrated
Manufacturing”, Page 49, 50.
[7] Walter.G.Holmes (1939), “Applied Time and
Motion Study”, The Ronald Press Company.