Root cause analysis

International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 1, January 2013)

211

Root Cause Analysis for Reducing Breakdowns in a

Manufacturing Industry Kiran M

1, Cijo Mathew

2, Jacob Kuriakose

3

1PG Scholar, M A College of Engineering, Kothamagalam, Ernakulam, Kerala

2,3Assistant Professor, M A College of Engineering, Kothamagalam, Ernakulam, Kerala

Abstract – Now a days manufacturing industries are

facing a greater competition in the market. Because of this,

they try to improve and increase both quality and

productivity continuously. One way to increase the

productivity is to increase the availability of existing

machines; Total productive maintenance aims to increase

the availability of existing equipment so no further capital

investment is needed. Availability of machines can be

increased by reducing the downtime or Breakdowns of the

machines. The main objective of this study is to find out the

major breakdowns causing production losses to the

company and to suggest counter measures by which these

problems can be reduced. In the study a Root cause analysis

is conducted to find the root cause of breakdowns and some

parallel improvement opportunities were also identified for

implementation so as to reduce the downtime.

Keywords – Breakdowns, Cause and effect diagram,

Pareto Chart, Total productive maintenance, Root cause

analysis.

I. INTRODUCTION

The manufacturing industries have gone through

significant changes in the last decade. New firms in

markets have increased competition dramatically. Most

of them focus on product quality, production time and

cost of product. Because of these, a company should

introduce a quality system to improve and increase both

quality and productivity continuously.

Total productive maintenance (TPM) is a methodology

that aims to increase the availability of existing

equipment hence reducing the need for further capital

investment [2, 5]. TPM can be defined in terms of overall

equipment effectiveness (OEE) which in turn can be

considered a combination of the operation maintenance,

equipment management, and available resources [7]. The

goal of TPM is to maximise equipment effectiveness [6].

It is a function of availability, performance rate, and

quality rate. Of the six major categories of losses that

affect OEE, Breakdown loss is used for calculating the

availability of equipment.

Root cause analysis (RCA) is a method of problem

solving that tries to identify the root causes of faults or

problems that cause operating events [1, 3, 9, 10].

RCA practice tries to solve problems by attempting to

identify and correct the root causes of events, as opposed

to simply addressing their symptoms [8]. By focusing

correction on root causes, problem recurrence can be

prevented.

A case study is conducted on one of the leading male

contraceptive manufacturing industry in the world. The

company is in the phase of implementing TPM. So as a

fore work to the implementation of TPM, case study,

Root Cause Analysis for reducing the breakdowns in the

company’s manufacturing unit is conducted. The

objective of study is to find out the major breakdowns in

the company which causes a production loss and to

suggest counter measures to minimize the effect.

The paper is structured as follows. Section 2 gives

clear idea of the problem in the industry. Section 3

presents the Root cause analysis of the problem. Parallel

improvement opportunities are exposed in Section 4.

Finally, Section 5 concludes the study.

II. PROBLEM DEFINITION

Even after producing 24 x 7, the company is not able

to meet its demands in the market. So firm has to reduce

the unwanted stoppages of production so as to maintain

the steady production level and to meet the demands in

the market. Production may be stopped due to many

reasons like breakdown of machine, maintenance work,

labour issues, insufficient material supply, problems in

the method of production etc… Excluding all other

factors like materials, method, man, etc... It is necessary

to reduce the breakdown (down time) of machine or

equipment’s in the company for the efficient nonstop

production to meet the demands. Breakdowns are the

most common causes of efficiency loss in manufacturing.

Eliminating unplanned down time is critical to improving

Overall Equipment Efficiency. It is not only important to

know how much Down Time your process is

experiencing (and when) but also to be able to attribute

the lost time to the specific source or reason for the loss.

Case study was conducted on the breakdowns of

machines or equipment’s of the company and to find out

the root causes of these breakdown so as to eliminate

them and to decrease the downtime caused due to these

breakdown.



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III. ROOT CAUSE ANALYSIS

The Root Cause Analysis is a four-step process

involving the following:

1. Data collection

2. Cause charting

3. Root cause identification

4. Recommendation.

A. Data Collection and Analysis

Breakdown data was collected for 8 months (from

01/12/2012 to 02/08/2012) from the shift log book of the

company and is tabulated (Tab. 1). The breakdowns and

frequency of occurrence are:

TABLE I

BREAKDOWNS OCCURRED AND FREQUENCY

Sl. No. Breakdown occurred Frequency

1 Edge roller not working 98

2 Vulcanization Barrel not working 68

3 Chain slipping 20

4 Mould touching the tank 12

5 Washing machine not working 9

6 Waste water pump not working 8

7 Quenching barrel choot block 7

8 Carry fan not working 6

9 Dehydrator not working 6

10 Slurry pump not working 4

11 Dehydrator chain slip 3

12 Feed valve block 3

13 Stripping line block 3

14 Washing brush not working 3

15 Steam line leak 3

16 Stripping jet not working 3

17 Jacket cooling water line leak 2

18 Hot air blower belt broken 2

19 Mould cooling motor not working 1

20 Dipping tank agitator not working 1

21 Agitator belt broken 1

22 Ammonia line leak 1

23 Spin dryer not working 1

24 Slurry auto valve not working 1

25 Hot air blower not working 1

26 Mould jerking 1

27 Body brush not working 1

28 Hot water gland leak 1

29 Conveyor chain loose 1

30 Quenching barrel block 1

Breakdown data collected consist of all breakdowns

that occur in a manufacturing firm. But our area of

interest is the breakdown causing production stoppages.

Stoppage of one minute causes 140 pieces of products

wasted. Calculating the loss in rupees, each product

cause a loss of profit of Rs. 4.5/-, i.e., a loss of about Rs.

630/- per minute.

The breakdowns causing stoppages of production

process were identified from the data. The time spend to

rectify the breakdowns was also noted. The Fig. 1 gives

the major breakdowns causing production losses.

Fig 1: Pie chart showing breakdowns causing production stoppage

From the chart it is clear that Edge roller breakdown

(40%) accounts for the most of the breakdown causing

production loss to the company. Vulcanization barrel

breakdown (28%), Chain slipping (8%) etc… are other

major breakdowns in the company as per the data

collected.

The times spend for getting back the equipment for

work was also collected and analysed. Fig. 2 gives the

percentages of time spend for different breakdown

maintenance. The chain slipping (63%) accounts for the

major time loss of production. Edge roller breakdown

(13%) and slurry pump breakdown (13%) also accounts

for a considerable loss of production for the industry.

40%

28%

8%

5%

4% 3%

3% 3% 2% 2% 2%

Breakdowns Edge rollerVulcanization barrelChain slippingMould touching the tankWashing machineWaste water pumpQuenching barrel choot blockSlurry pumpDehydratorCarry fanOthers



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Fig 2: Pie chart showing time spent to rectify breakdowns

For slurry pump breakdown, company have an

alternate pump which is used while breakdown of the

main pump. In case of vulcanization barrel they go for

manual vulcanization while the breakdown. And in the

case mould touching the tank they have a readjustment

screw for the adjustment. So the other types only

accounts for small stoppage rather than a larger time

consuming breakdowns.

Considering the frequency of occurrence and the time

wasted due to breakdown maintenances, it was identified

that chain slipping and edge roller breakdown was the

major causes of production loss in the company.

So root cause analysis was conducted identification of

root causes of chain slipping and edge roller breakdown.

B. Cause Charting and Root Cause Identification

Cause-and-effect diagrams or Ishikawa diagrams (Fish

bone diagram) is one of the seven basic tools of quality,

which is used to identify potential factors causing an

overall effect [4]. It was used in the study to identify the

root cause of the major breakdowns identified in the

previous section. A Pareto chart, where individual values

are represented in descending order by bars, and the

cumulative total is represented by the line. The left

vertical axis is the frequency of occurrence, and right

vertical axis is the cumulative percentage of the total

number of occurrences. The purpose of the Pareto chart

is to highlight the most important among a (typically

large) set of factors [4, 11]. In quality control, it often

represents the most common sources of defects, the

highest occurring type of defect.

1. Root Cause Identification of Edge Roller Breakdown:

Edge roller is unit used to roll up the edges of the

product produced in the company. It mainly consists of a

pulley belt arrangement, motor, bevel gear, and a long

brush mounted on a shaft. The edge roller unit is a major

contributor to the time loss to production due to its

frequent breakdowns.

Fig 3: Initial cause and effect diagram of edge roller breakdowns

Fig. 3 shows the initial cause and effect diagram of

edge roller. The causes of breakdown may be belt loose

or lower belt tension, bevel gear dislocation, motor

breakdown of the roller and brush damages.

A Pareto chart (Fig. 4) was constructed as per the

frequency of occurrences of each causes of edge roller

breakdown. From the chart it is clear that lower belt

tension or belt loose and bevel gear dislocation are the

major causes of the breakdown of the edge roller

equipment.

Fig 4: Pareto chart of edge roller breakdowns

63% 13%

13%

8%

3%

Time Spend Chain slipping

Edge roller

Slurry pump

Vulcanization

barrelOthers



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Fig 5: Final cause and effect diagram of edge roller breakdowns

A detailed study was conducted on causes for the edge

roller breakdown and final cause and effect diagram is

prepared as given in Fig. 5. Reasons for lower belt

tension was identified as deterioration, thermal expansion

of belt and the regular readjustment made on the machine

part. Regular readjustment cannot be rectified since as

the mould length varies the edge rolling unit has to be

readjusted to obtain the correct rolling thickness.

Deterioration and thermal expansion of belt can be

overcome by using a higher grade belt than the present

one, having a higher temperature range and longer life.

Motor breakdown was caused due to vibration

machine, contaminations and the over/under lubrication

of bearings of the motor. Brush damages were caused

due to deterioration of brush teeth and misalignment of

brush with the mould. But this only need a small time to

rectify and does not affect the production so much.

The major reason for edge roller was the breakdown

caused due to bevel gear dislocation of the machine.

Dislocation happens due to overload, tooth breakage of

bevel gear, and bearing damages. Bearing damage was

due to overheating, contamination of bearings and

improper load acting on it. Overload in bevel gear and

improper load in bearing was mainly due to the

misalignment of shaft. As mentioned earlier there is a

need of regular readjustment of the machine as the size of

mould varies. If proper alignment checking is done

during the adjustment of edge roller the breakdowns can

be avoided.

2. Root Cause Identification of Chain Slipping:

Conveyor Chain is a major part of moulding machine

in the manufacturing plant. This endless chain carries the

vertically positioned moulds in the moulding section.

Any breakdown to this unit causes the entire stoppage of

production.

Fig 6: Initial cause and effect diagram of Chain slipping

Fig. 6 show initial cause and effect diagram of chain

slipping. The causes of breakdown may be Pinion

breakage, vibration of machine, chain loose, and

contamination. A Pareto chart (Fig. 7) was constructed as

per the frequency of occurrences of each causes of chain

slipping. From the chart it is clear that pinion breakage is

the major cause of the breakdown due to chain slipping.

Fig 7: Pareto chart for chain slipping



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Fig 8: Final cause and effect diagram of chain slipping

A detailed study was conducted on causes for

breakdown due to chain slipping and final cause and

effect diagram is prepared as given in Fig. 6. Reasons for

vibration of the chain were the lower tension of the chain

due to its stretching or wearing and wearing of other

parts of the moulding machine. Chain becomes loose due

to stretching or wearing due to its longer and continuous

use. Contamination due to improper cleaning on the

equipment was also identified as a reason for chain

slipping. These causes can be eliminated by performing

proper maintenance techniques like preventive

maintenance, planned maintenance etc…

The major reason for chain slipping was the

breakdown caused due to pinion breakage in the

moulding machine. The different causes of pinion

breakage was improper design of pinion, improper

checking methods employed for incoming pinion from

suppliers, and pinion getting stuck at the sprocket of the

machines. By adopting a inspection method for incoming

material, the first two causes can be avoided. Pinion get

stuck at the sprocket due to contaminations (like

lubricant and dust mixture), over speed, and the

movement of pinion without mould. Mould gets

withdrawn from the pinion due to improper tightening,

while entering the rack section. A proper implementation

of tightening mechanism can avoid the occurrence of this

breakdown.

C. Recommendations

From cause and effect diagram, the root causes of

breakdowns caused due to chain slipping and edge roller

was identified.

In the case of edge roller, belt deterioration and

Improper alignment checking of the unit after

readjustment were identified as the root cause for edge

roller breakdown. A higher grade belt like EPDM belt,

which can withstand higher temperature and longer life,

can be used for the purpose. Other cause is improper

alignment checking of edge roller, for this, workers

should be given proper training for checking the

alignment of the edge roller unit.

Root cause for chain slippage was identified as the

improper tightening of pinion and the mould. Presently

pinion is tightened manually to the mould. So there will

be variations in the tightness due to the force applied by

human hand. A proper means for tightening should be

adopted to avoid this cause for the breakdown due to

chain slipping. Using a torque wrench is suggested as a

counter measure for avoiding the chain slippage.

IV. PARALLEL IMPROVEMENT OPPORTUNITIES

In the case of edge roller, belt deterioration and

Improper alignment checking of the unit after

readjustment were identified as the root cause for edge

roller breakdown. To avoid this breakdown an

improvement in the present setup can be made. By using

a direct drive for each edge roller unit, parts like belt,

pulley and bevel gear can be avoided from the present

setup. Thus avoiding the breakdown caused by belt and

bevel gear, which accounts for the most of edge roller

breakdowns of the machine.

A. Technical Feasibility

The technical detail of the motor that runs the edge

roller is given below.



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Speed of motor = 1400rpm

Gear ratio = 1:10

Torque required = 170Nm

Maximum weight permissible

= 14kg

Direct drive specification available in the market

[12]:

Model =

Unicase helical bevel gear unit (BIM 1040)

Make = NordIndia, Pune

Gear ratio = 5.4 – 200

Power range = 0.12 – 9.2kW

Torque range = 48 – 670Nm

Fig 10: Direct drive, NordIndia make.

B. Economic Feasibility

Cost of a single direct drive

= Rs. 8000/-

Installation cost (for 14 machines)

= 14*4000

= 56000/-

Total investment for implementation

= 14 * 8000+56000

= Rs. 1, 68,000/-

No. of products produced in 1 minute

= 140 in one line

Average no. of breakdowns/month

= 15 nos.

Average time taken for rectification

= 20 minutes

Loss in profit/product

= Rs. 4.50/-

Loss due to breakdown of edge roller

(Considering 2 lines of production)

= 280*15*20*4.50

= Rs. 3, 78,000/-

Implementation of direct drive will reduce the

breakdown due to edge roller to zero and company can

increase their profit.

Increase in profit/month

= 378000 – 168000

= Rs. 2, 10,000/-

V. CONCLUSION

The main objective of study was to identify the major

breakdowns causing the production loss to the company.

Root cause analysis was conducted for the major

breakdowns causing production loss to the company.

Root causes of breakdowns were identified using cause

and effect diagram. Counter measures and parallel

improvement opportunities for major breakdowns

causing production stoppage was also suggested.

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