ISSN : 2249-5762 (Online) | ISSN : 2249-5770 (Print) IJRMET Vol.

2, Issue 2, July - Dec 2012

Calculation of OEE for an Assembly Process

1
Soniya Parihar, 2Sanjay Jain, 3Dr. Lokesh Bajpai
1
Dept. of Mechanical Engineering, CIMs, Samrat Ashok Technological Institute Vidisha, MP, India
2,3
Dept. of Mechanical Engineering, Samrat Ashok Technological Institute Vidisha, MP, India

Abstract
OEE measurement is also commonly used as a Key Performance
Indicator (KPI) in conjunction with lean manufacturing efforts
to provide an indicator of success. It quantifies how well a
manufacturing unit performs relative to its designed capacity,
during the periods when it is scheduled to run. It is a well
known concept in maintenance and is a way of measuring the
effectiveness of a machine which evaluates and indicates how
effectively a manufacturing operation is utilized. It is not however
an absolute measure and is best used to identify scope for process
performance improvement, and how to get the improvement. This
paper investigates the utilization of OEE measure for efficient
management of improvement in production performance and
calculation of OEE in processing industry which assemble various
parts of tractor at various lines.

Key words
Assembly process, Effectiveness, Management, OEE, Perform-
ance
Fig. 1: Overall Equipment Effectiveness Model
I. Introduction
Lean Manufacturing: Lean Production or Lean Manufacturing is a OEE is becoming a commonly utilized maintenance metric
manufacturing/production system best characterized as relentlessly within lean organizations. The OEE concept normally measures
eliminating waste from all of its activities and operations. Lean the effectiveness of a machine center or process line, but can be
strives to produce products and deliver services: utilized in non-manufacturing operations, also.
• On-Time The high-level formula for the lean manufacturing OEE is:
• Using as few resources as possible OEE = Availability X Productivity X Quality.  
• Better than competitors
• Faster & Cheaper than competitors B. The Benefits of OEE Measurement
• While Eliminating as Much Waste as Possible The goal of measuring OEE is to improve the effectiveness of
Lean Manufacturing is the “umbrella” under which many equipment. Since equipment effectiveness affects shop floor
manufacturing improvement tools are housed. Some examples employees more than any other group, it is appropriate for them
include: to be involved in tracking OEE and in planning and implementing
• TPM: Total Productive Maintenance equipment improvements to reduce lost effectiveness. An OEE
• 5S: Visual Workplace or Visual Factory solution can enable manufacturers to achieve world-class status.
• Kanban: Work Signaling System More specifically, it can provide benefits in three key areas:
• 2-Bin: Materials Replenishment system
• Error & Mistake-Proofing: A perfect process tool 1. Equipment
• Level-Loading: For producing mixed quantities and styles Reduced equipment downtime and maintenance costs and better
of products management of the equipment life cycle.
• Inventory Reduction
• Kaizen Events or Improvement Events 2. Personnel
• Continuous Improvement and Lean Culture Change Labor efficiencies and increased productivity by improving
• Overall Equipment Effectiveness visibility into operations and empowering operators

A. Overall Equipment Effectiveness 3. Process

Overall equipment effectiveness is a concept utilized in a lean Increased productivity by identifying bottlenecks
manufacturing implementation. OEE can be defined as “A vital
component of the Lean Manufacturing philosophy, OEE provides 4. Quality
a methodology for calculating the overall effectiveness of the Increased rate of quality, reduced scrap
production environment.”
It is often shortened to just OEE. It is an established method (i). Background
of measuring and then optimising the efficiency of a machine’s The OEE is defined as a measure of total equipment performance,
performance or that of a whole manufacturing plant. that is, the degree to which the equipment is doing what it is
supposed to do. The OEE metric that originally described by
Nakajima (1988), can measure level of equipment effectiveness,

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IJRMET Vol. 2, Issue 2, July - Dec 2012 ISSN : 2249-5762 (Online) | ISSN : 2249-5770 (Print)

and also identify loss elements which are classified into six major B. Performance
groups OEE metric identifies and measures main production losses Performance is in theory very simple. It is the actual achieved
such as availability, performance and quality. Therefore OEE run rate against the ideal run rate for the machine. Often the
can be used as a key tool to improve equipments effectiveness machine ideal or optimum run rate may be the figure published
and consequently increase productivity. Ivancic (1998), the main by the machine manufacturer. However, we all know that the
difference lies in the inclusion of planned downtime in the total ideal run rate may be affected by the situation of the machine,
planned time horizon. According to the presentation at the 1999 heat, cold product running through etc. Purists would say you
Society maintenance reliability professional conference, Rohm still refer to the published run rate whilst others may suggest
and Haas Corporation determined that developing hidden capacity that expected performance may necessarily be degraded by the
of existing factories was ten times less expensive than building nature of the product going through it. In a situation where the
new capacity. OEE can be considered to combine the operation, same product, with no expected variability, passing through the
maintenance and management of manufacturing equipment and machine, such as a line in a bottling plant, we would expect the
resources. According Hansen (2001) performance evaluation is ideal run rate to remain constant and therefore variances may
one of the key tools to determine world class companies. The easily be identified.
overall line effectiveness (OLE) was proposed by Nachiappan
and Anantharaman (2006) to measure productivity of product line
involving machines in series which arranged in continuous line
manufacturing effectiveness of a manufacturing line (OEEML).

II. Components of OEE

Three main factors make up the OEE calculation: They are
• Availability (A) C. Quality
• Performance (P) The final factor on the overall OEE calculation is quality. This is
• Quality(Q) simply a measure of good product divided by the total product
(for the job, shift, day, week etc). This factor is then:

III. The Assembly Process

The assembly line for tractor parts has been categorized depending
upon their operations they are performing. They are namely-
• ADDC line
• Transmission line
• Pre painting line
• Paint shop
• Post painting shop

A. ADDC Line
ADDC stands for Automatic Depth and Draft Control. This is used
for the operation of the agriculture implements like cultivator,
MB plough, disc harrow etc. ADDC system controls the depth of
implement, depending upon the draft. Draft is resistance of soil
which acts against the implement. ADDC is based on the principle
of sensing the forces on implement hence using the hydraulic
pressure to lift or lower the 3-point linkage.

Fig. 2: Components of OEE B. Transmission Line

In this line the gear box, differential assembly, final drive assembly
A. Availability and ADDC coupling is done. The gear box assembly is called
The percentage of time that a machine is actually able to produce g1 and differential assembly is called g2. The various gear
parts out of the total time that it should be able to produce parts mechanisms used in tractor are:
This number includes breakdowns, setups, and adjustments. • Sliding gear mechanism
The calculation for availability is simply the actual production • Synchro-mesh mechanism
time, including set up, out of the planned production time. Time Transmission assembly also consists of PTO (Power transmission
that is lost due to downtime through machine failure, lack of output) that is used to run the pump for drawing out water and
input materials, lack of operator(s), as a series of examples, will some implements like rotavator etc.
be set against the calculation. Therefore the actual consumed time
divided by the available time will give you a figure, expressed as C. Pre Painting Line
a percentage that is a factor that contributes to the overall OEE This line includes the coupling of engine and fly feel to the
calculation. transmission assembly. Then brakes clutch, steering mechanism
are assembled along with the order items like weight, pressures
pipe, suction pipe.

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D. Paint Shop • Rough Running

This shop is basically in 2 categories one line itself and second • Under Nameplate
sheet metal paint shop. On the line, the chassis of tractor is painted Capacity
and is then baked in oven. In sheet metal paint shop consists Reduced Speed Speed Loss • Under Design
of thirteen tank systems which include first cleaning of the Capacity
material, re-dusting and rescaling, surface activation for better • Equipment Wear
paint adhesion. • Operator Inefficiency
• Scrap
E. Post Painting Line • Rework
The post painting line involves the assembly of bonnet, dashboard, Startup Rejects Quality Loss • In-Process Damage
electrical air cleaner, water radiator, tyres etc. This also involves • In-Process Expiration
filling of oils like steering, air cleaner, gear box oil and diesel • Incorrect Assembly
oil. • Scrap
• Rework
F. Time Matrix for each Process Production
Quality Loss • In-Process Damage
Rejects
• In-Process Expiration
Table 1: Time Matrix for Each Process • Incorrect Assembly
Process Operators Cycle Time (in Sec) Uptime
ADDC Line 3 245 90%
V. Calculation of OEE
Transmission
3 240 90%
Line A. Calculation for Line Balancing
Pre paint Line 3 242 90% 1. Available time per Shift = 510 Min
Paint Shop 5 245 98% 2. Lunch time = 30 Min
Post paint Line 4 230 94% 3. Total time (1-2) = 480 Min
Shipping 2 240 - 4. Working time in a shift @ 85% efficiency = 450 X 85% =
Total 20 1442 92% 408 Min
5. Marketing Requirements = 4500 Tractors/ month
6. Working Days in a month = 25 Days
IV. Six Big Losses in Manufacturing Process 7. No. of shift in a month = 25 X 2
One of the major goals of OEE is to reduce and/or eliminate 8. Per shift Requirement of Tractors = 4500/50 = 90 No’s
what are called the Six Big Losses the most common causes of
efficiency loss in manufacturing. B. Overall Equipment Effectiveness
1. Shift Length = 8:30 Hrs = 510 min
Table 2: Six Big Losses in Manufacturing Process 2. Meal Break = 1 @ 30 min
Six Big loss OEE Loss Event Examples 3. Time losses due to various non productive event = 78 min
Category Category 4. Ideal Run Rate = 12 parts / hour
5. Total Parts = 4500 / month
• Tooling
6. Rejected Parts (Efficiency of process 85%) = 675
• Failures
• Unplanned
C. Planned Production Time (PPT)
• Maintenance
Down Time = Shift Length – Breaks
Breakdowns • General
Loss = 510 – 30
• Breakdowns
= 480 min
• Equipment
• Failure
D. Operating Time
= PPT – Down time
• Setup/Changeover = 480 – 78
• Material = 402 min
• Shortages
Setup and Down Time
• Operator E. Good Pieces
Adjustments Loss
• Shortages = Good parts – Rejected parts
• Major Adjustments = 4500 – 675
= 3825
• Obstructed
• Product Flow F. Availability
• Component Jams = Operating time/ PPT
Small Stops Speed Loss • Misfeeds = 402 Min/ 480 min
• Sensor Blocked = 83.75%
• Delivery Blocked
Cleaning/Checking

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G. Performance VII. Conclusion and Future Work

= (Total Parts/ Operating time)/ Comparison between World-Class and assembly process OEE
Ideal run rate rates:
= (4500/402)/ 12
= 83.3% Table 4: Comparison of World Class OEE Factor and Assembly
Process Factor
H. Quality
= Good parts/ Total Parts OEE Factors World Class Assembly Process
= 3825/4500 Availability 90.0% 83.75%
= 85% Performance 95.0% 83.3%
Quality 99.9% 85%
I. OEE
= Availability X Performance X Quality OEE 85.0% 60.01%
= 0.8375 X 0.833 X 0.85 Recent studies indicate that the average OEE rate in manufacturing
= 60.01% plants is 60 percent. As shown above a world-class OEE is
considered to be 85 percent or better. Our assembly process
VI. Result & Discussion has 85% efficiency and 15% losses. These losses mainly are
Three factors are calculated by different formula and product of downtime losses, speed losses and quality losses which affect
availability, performance and quality gives OEE of process. OEE Overall Equipment effectiveness of the process. To minimize these
of assembly process is 60.01% losses and to achieve world class OEE there should be reduction
in events which are discussed in six big losses section. The main
events which are responsible for losses in assembly process are
• Tooling Failures
• Unplanned Maintenance
• Setup/Changeover
• Material Shortages
• Operator Shortages
• In-Process Damage
• In-Process Expiration
• Incorrect Assembly
It is important to decrease these non productive events which affect
efficiency of the process. They can be reduce by implementing new
Fig. 3: Graphical Representation of OEE and its Components techniques and tools, proper inventory storage, in line assembly,
skilled labors, special purpose machinery etc.
There are three main time losses during process which are
downtime loss, speed loss, quality loss. These losses are important A. Future Recommendations
to identify for calculation of OEE and also to suggest improvement • The OEE metrics is very useful for monitoring the production
in existing process. performance and also be seen as a sustainability performance
indicator.
Table 3: Time losses in Assembly Process • Future research may be done to explore the dynamics of
Time translating equipment effectiveness or loss of effectiveness
in terms of cost.
Shift Length 510 min
• OEE approaches can be apply in supporting technologies
Planned Production Time 480 min 30 min meal break • We can experience changes in implementing OEE and can
Actual Operating Time 450 min 30 min down time loss Identify, overcome barriers
Net Operating Time 428 min 22 min speed loss
Valuable Operating Time 408 min 20 min quality loss References
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ISSN : 2249-5762 (Online) | ISSN : 2249-5770 (Print) IJRMET Vol. 2, Issue 2, July - Dec 2012

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