Sheet Metal Assembly Process Optimization Using Lean Manufacturing Tool

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 09 Issue: 07 | July 2022 www.irjet.net p-ISSN: 2395-0072
© 2022, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page 2644
Sheet Metal Assembly Process Optimization Using Lean Manufacturing
Tool
Kaanv Patel1, Aadit Khant1, Dipan Dholakia1
1Undergraduate student at PDEU, Gujarat, India
---------------------------------------------------------------------***---------------------------------------------------------------------
Abstract - Numerous manufacturing firms in India
experience a variety of issues, including long cycle times, a
high number of rejections, unfulfilled orders, degraded
quality, inadequate safety assurance, etc. Japanese lean
production tools such as KAIZEN,5S and Kanban aid in
achieving continual improvement in the workplace.
Applying these results in the removal or reduction of various
wastes in a sector of the economy improves the
organization’s overall effectiveness. Assembly time
reduction has appeared as an essential thing of
improvement to produce a component of high quality in the
least time possible with maximum resource utilisation. The
following study was carried out at a CNC manufacturing
company.
Key Words: Time Study, KAIZEN, Assembly process, Bolt
Tray
1.INTRODUCTION
A sheet metal assembly of a single CNC machine took 6
hours to complete at the company. The simple task was to
achieve the same quality of final assembly in the least
possible time by optimizing the process. Various industrial
engineering concepts were applied to achieve the
aforementioned. The concepts are explained in brief
below:
1. Kaizen: It is a Japanese term for "improvement" or
"change for the better," and it refers to a way of
thinking or doing things that are centered on always
improving business, engineering, and manufacturing
processes. Kaizen strives to reduce waste by
enhancing standardized tasks and procedures.
2. Cycle Time: It is described as the actual amount of
time needed to perform a series of tasks (one cycle).
3. Time Study: Time study is a structured technique of
directly observing and measuring human work with a
timing device to determine the time required for a
qualified worker to complete the work at a set level of
performance.
It adheres to the fundamental technique of systematic
work measurement of:
 Work analysis into simple, clearly observable
components or factors
 Measurement of individual components
 Synthesis of those measurements to arrive at a
time for the entire job
4. 5S: The term 5S is a housekeeping philosophy about
maintaining order and cleanliness in the work area.
The five Ss are:
 Sort: Sorting involves clearing the workspace of
any extraneous objects and discarding them.
 Straighten: The remaining tables, tools, parts,
documents, and workbenches need to be sorted
now that the mess has been removed. Keep
everything at right angles while straightening as a
general rule of thumb.
 Scrub/Shine: The meaning of the third S is rather
obvious. To help it look like a showroom, the
work area should be thoroughly cleaned. The
operators will feel proud of keeping the
workplace tidy and orderly, and you'll discover
that they'll want to continue doing so. Cleaning is
beneficial for appearance as well as accident and
injury prevention.
 Standardize: Written criteria should be created to
track the 5S program's development and
compliance. As previously indicated, keep colors
and identifications uniform and straight.
 Sustain: Just developing the above given system is
not enough. A company needs to maintain it, as
humans we are naturally resistant to change, so
an employee should be appointed who sees to the
maintenance of the system.
5S improves employee morale, makes a fantastic first
impression on consumers, and keeps the operation
running smoothly with continual accountability and
faith in the programme.

5. Kanban: It is a method for defining, administering,
and enhancing knowledge-delivery services. It aids in
visualizing tasks, increasing productivity, and always
improving. Kanban boards represent work, allowing
employees to maximize work delivery across various
teams and handle even the most complicated projects
in a single environment.
1.2 Existing Process
The sheet metal assembly of a typical 800mm bed size
model consist of 52 pieces and 150+ nut bolts of various
types. The complete process of putting together a whole
body takes 2 workers about 6 hours (360 mins).
As for the bolt arrangement they were using a big trolley
in which all the tools were kept. The issue with the trolley
was that it could not be taken inside the sheet metal
assembly.
The Old assembly process consisted of no standard
operating procedure and the whole assembly was done by
the workers according to their convenience and
availability of equipment and material.
Timing for each activity was found using time study. To
measure the time and record the duration of an activity, a
continuous stopwatch was used. This eliminates the
requirement for subtractions and enables the element
times to be entered directly on the time study sheet. The
time spent by each operator on the task, which they
completed over a number of cycles, was recorded.
The time study data can be found below:
READING
NO.
TOTAL
TIME
WORKER - A WORKER - B
1 351 351 328
2 346 346 331
3 333 333 315
1.3 Kanban application in the plant:
The company has been using two bin Kanban system to
solve their inventory needs. The general working of the
system is as follows: The 2-bin system, to put it simply, is a
method of managing inventory that employs two actual
bins, typically for small but essential parts (such as
fasteners and components). It is a straightforward pull
system in which containers contain the pieces.
The system is merely based on giving employees two
plastic storage bins filled with inventory, which they can
use to fill orders or supply supplies to various
departments. The number of products put in the bins will
depend on how quickly they are utilized individually
The employees take what they need from one bin until it is
empty, at which point they switch to the second bin while
simultaneously placing an order to restock the first bin
with what they need. The first bin must be replenished
with a predetermined quantity of goods, so there is little
chance of running out of supplies (which could slow down
production).
2. Improvements:
Introduction of a standard operating procedure for the
workers with the inclusion of diversions for equipment
and material shortages was experimented by us. The
proposed process led to equal distribution of work over
the workers. This led to better resource utilization. And a
custom-made magnetic bolt tray was also introduced. All
this made an improvement in the sheet metal assembly
time.
2.1 Proposed Flow Chart

Assembly Task
Estimated
Time
Worker
A
Worker
B
Silicon Application 10
Assembly of Right and
Left Joint of Sheet Metal
20
Top Cover Joint 10
Top Guide Bar 20
Sliding Door
Preparation (1)
45
Bottom Cover 10
Bottom Rail 15
Tool Holder Door
Assembly W/O Acrylic
Glass
25
Sliding Door
Preparation (2)
45
Window Assembly W/O
Acrylic Glass
40
LED Light Mounting 15
Tool Holder Rack Fitting 15
3M Tape 15
Name Plates and Black
Plates
35
Acrylic Mounting for All
Windows
30
JSL Plate 10
Brackets 15
Door Mounting and
Door Alignment
35
Stoppers Mounting 20
Total Time
280
min
280
min
The flow chart can be interpreted as follows:
Task of the 2 workers have been divided in 3 blocks, Red is
for worker A, Green is for worker B and Blue is where they
both work together. The task has been written with the
estimated time it takes a worker to complete it. The time
for each task was recoded from the time studies conducted
above and their average time was taken.

The excel table can be interpreted as follows:
Each row contains a task, it’s approximate completion
time and the green color indicates work allocation to the
worker. The table was used during the application of the
flow chart to cross check the results and write
observations. The observations are further discussed in
conclusion.
It can be deduced from the above table and flow chart that
there is equal time-based work allocation between both
the workers.
In case of equipment shortages, the workers were
provided with a table beforehand, which contains the task
which can be performed in such conditions.
Without Crane Without Drill
Without 3M
Tape
Name Plates Window Hinges Name plates
Door
preparation
Unwrapping Thread tapping
Application of
3M tape on tool
door
Tray bolt
Mounting
Window
Mounting
Unwrapping Black Plates
Bolt mounting
int the tray
2.2 The Magnetic Bolt Tray:
We designed and built 2 magnetic bolt trays, one for the
right and other for left side of the assembly. Each tray had
exact number and size of slots as the required bolts. The
assembly uses very few nuts so no slots for nuts was
Software) the rendered images can be found below.
The tray used upcycled acrylic sheets from the window
pane. Acrylic was drilled as per the design. A right-angle
bracket from the headstock assembly of the CNC was used
to hold the acrylic and the magnet together. We used an off
the shelf magnet with the carrying capacity of
approximately 2 kgs.
This tray created the following improvements: The
workers now did not have to remember the number and
sizes of bolts for the assembly, as when they arranged the
tray with the bolts it is made sure that they have just the
required bolts. The magnetic support of the tray made it
very versatile as it can be attached on any section of the
sheet metal assembly. Due to which there was a reduction
in the worker’s hand and feet movement.
3. CONCLUSION
It was observed that implementation of KAIZEN and the
optimization of a standardized operating procedure in the
assembly led to a 20% increase in productivity. There was
a reduction in the lead time without making new
resources available.
After the implementation of the above-mentioned process
flow chart and the magnetic bolt holder tray we observed
50%
50%
WORK TIME
DISTRIBUTION
Worker A Worker B
provided. The tray was first made in Fusion 360 (CAD

the process and have come up with following issues which
can be improved further:
1. Unexpected inconveniences caused due to different
skill level of different workers and their experience.
2. Improvement in tray deign to accommodate nuts and
button bolts. Also, custom magnet to support the
added weight will be needed.
3. A time study should be performed to segregate tasks
in value and non-value adding tasks. This will further
decrease the projected lead of the assembly.
REFERENCES
[1] Ortiz, C. A. (2006). Kaizen Assembly: Designing,
Constructing, and Managing a Lean Assembly Line (1st
ed.). CRC Press.
[2] Tejas Rathod et al. A CASE STUDY ON APPLICATION
OF KAIZEN IN INDUSTRY, International Research
Journal of Engineering and Technology (IRJET), June
2019.
[3] Jain, Ashish. (2015). The Kaizen Philosophy for
Industries: A Review Paper.

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