Report on REJECTION REDUCTION IN CPC RING

A REPORT

ON

SUMMER TRAINING INTERNSHIP IN

ON TITLE

REJECTION REDUCTION IN CPC (COMPOSITE PLATING OF

CHROME) RING

SUBMITED TO

ASET, Amity University, Noida

BATCH: 2011-2015

SHRIRAM PISTONS AND RINGS PVT. LTD. SUBMITTED BY:-

REPRESENTATIVE: K.VENU GOPAL

MR. ROHIT KUMAR ROLL NO. - A2305411030

ENGINEER, C2D1 PLANT

i

CERTIFICATE

This is to certify that Mr. K.Venugopal of Amity School of Engineering and Technology, Amity

University, Noida (U.P.) has been provided with industrial training in Shriram pistons and rings

Pvt. Ltd. (Ghaziabad) for the period of 8 weeks from 02/05/2014 to 25/06/2014 under my

guidance. During this period he has successfully completed the project “REJECTION

REDUCTION OF CPC RING”

Rohit kumar K.Venu gopal

(Guide)

ii

ACKNOWLEDGEMENT

I would like to express my gratitude to everyone who supported me and gave me a possibility to

successfully complete my project. A special thanks to our project guide, Mr.Rohit kumar,

Engineer, C2D1 Plant, whose help, stimulating suggestions and encouragement helped me to

coordinate my project and especially write this report. His constant support and guidance

throughout the course of the project has made the project reach its successful completion. Their

suggestions were indispensable in preparing ourselves to meet the challenges posed by the

project.

I would also like to thank Shriram Pistons and Rings Pvt. Ltd, which gave me all the liberty to

explore and understand the concepts of manufacturing on shop floor. I would like to thank my

faculty guide Mr. Prashant Gill of Amity University & Mr. Vivek Kumar, H.O.D (MAE) of

Amity University for guiding all my way throughout this project.

Last not the least I would like to thank my parents, seniors and friends without whose kind

support I could not have undergone the project smoothly & successfully.

I thank all those who knowingly and unknowingly have helped me in the fulfilment of this

project, I would like to heartily thank all of them.

iii

COMPANY PROFILE

Shriram Pistons & Rings Ltd. (SPRL) is one of the largest and most sophisticated manufacturers

of precision automobile components i.e. pistons, piston rings, piston pins and engine valves in

India. The products are sold under brand name ‘USHA/SPR’ in the markets.

SPRL manufacturing unit is located at Meerut road in Ghaziabad (25 km from Delhi). The plant

has been recognized as one of the most modern and sophisticated plants in north India in the field

of automobile the production capacity of plant is as under:

Piston : 17.06 million per year Actual Production in 2011-2012

Pin : 14.9 million per year Actual Production in 2011-2012

Rings : 76.5 million per year Actual Production in 2011-2012

Engine valves : 33.8 million per year Actual Production in 2011-2012

The company has technical collaboration with:-

M/s. Kolbenschmidt, Germany to produce pistons

M/s. Riken corporation, Japan for piston rings

M/s. Fuji Oozx, Japan for the manufacture of Engine Valves

M/s. Honda Foundary, Japan for technical support

The company supplies its products to several Original Equipment Manufacturers (OEMs) like

Ashok Leyland, Tata Cummin, Tata Motors, Maruti Suzuki, Mahindra & Mahindra, Tafe

Tractors, SML( Swaraj), Kirloskar Oil Engines, Bajaj Auto, Honda Siel Cars, Sundram

Claylon, Honda Scooter, International Tractors, Standard combine in addition to all the Honda

Joint ventures in India. SPRL is also supplying its products to international OEM’s like Renutt,

Nissan, Ford and Riken etc.

At Shriram Pistons and Rings Ltd. Quality is an integral part if whatever we do, which is

reflected in the company’s Quality Policy:

“Total Customer satisfaction through Quality Management and Continuous Improvement”

Quality Objectives:-

Organisation which is sensitive and interactive to the needs of customer.

Continuous upgrading of quality and process to meet changing needs of customer.

Optimization of return on investment by-

Continuous improvement

Technology development

iv

Organizational and personnel development

Cost reduction efforts

Effective use of all resources

Harmonious and safe working conditions

Work to international norms of quality and management.

The company has successfully practiced the best work ethics and technology along

with the TPM & Kaizen approach and harmony through teamwork.

Achievements in terms of quality:

SPR received the ISO-9001 certificate from RWTUV, Germany in 1994.

Technology from the collaborators was supplemented with In-house efforts and

by implementing world-class practices.

The company received QS-9000 certificate from TUV, Germany in the year

1999.

The company received ISO-14001 certificate in the year 2001.

SPR received the TS-16949 certificate in the year 2003.

The company received OHSAS-18001 certificate in the year 2003.

Best foundry awards from institute of Indian Foundry men in the year 2003.

Green rating award by CII, U.P.Pollution Control Board & World Bank in

2004.

The company received TPM Excellence award in the year 2004.

Received Diamond Award – overall Best performance in QCDDM, outstanding

performance in cost, bronze award for delivery, gold award for 5S from Honda

Siel Cars(I) Ltd. In 2006.

SPRL has received the Best Vendor Awards from Maruti Suzuki for 4

consecutive times, Best supplier performance awards from Tata Cummins Ltd

for 3 consecutive years. And has self-certified status with most of the OEMs.

Excellence award in Export by government of India.

Excellence award in productivity by ACMA in 2007-08.

Excellence award in quality by Honda Scooters and Motor Cycles Limited,

Excellence award in technology by ACMA in 2007-08.

Excellence award in manufacturing excellence award by ACMA in 2007-08.

Received silver trophy- technology from ACMA in2007-08.

Received outstanding supplier for technology award from Cummins in 2007-

08.

Received vendor performance award Kaizen, vendor performance award

overall commendation, overall achievement trophy from Maruti Suzuki in

2007-08

v

The company received recognition award by government of India for In House

R. & D.

Best foundry award received from Institute of Indian Foundry Men.

Received star performer(IC Piston Engine & Parts) award from Engineering

Export Promotion Council (EEPC) India.

Received silver award – Quality & Bronze award – spares from Honda Siel cars

India ltd. In 2007.

The company received TPM special award in march 2008

Received Best Quality Vendor award from Tata Motors ltd. In 2008-09.

Received best vendor award for overall performance (QCLDM) from Ashok

Leyland in 2008-09.

Received overall achievement trophy from Maruti Suzuki in 2008-09.

Received best explorer award from FIEO- Federation of Indian Export

Organisation in 2009-10.

Received Trophy from EEPC “STAR PERFORMER IN PRODUCT GROUP

OF ENGINES, TURBINES & PARTS” in recognition of outstanding

contribution to engineering exports during the year 2008-09.

ISO/TS 16949 achieved for SPR Unit-II – Ghaziabad in year -2009.

ISO/TS 16949 achieved for SPR Unit V pune in year 2010.

Received performance award form Honda siel Power products Ltd. In march -

2012.

Features of SPR factory:

Total area covered by the factory is 27 Acres.

The factory has manufacturing facilities for piston, rings, pins and engine valves.

Classification of the premises:

P.T.E- Production Technology and Engineering

C.A.A- Commercial Administration and Accounts

R & D- Research and Development

Total strength of the company is 5230 nos. consisting of officers, staff and workers.

The turnover/sales for the year 2011-12 are Rs. 1000.00 Cr.

The company is exporting or more than 35 countries.

Exports sales are of Rs. 188 Cr. year 2011-2012.

Over 10% of the production is exported to sophisticated markets such as Europe, UK,

Egypt, USA, Latin America etc.

SPR has been investing 30% of its retained earnings in quality upgradation and

modernization every year.

vi

VISION

World Class Company, Preferred by World Class Customers

Motivated, Dedicated and System Oriented Employees

Safe and Healthy Work Place

MISSION

Sales and profit growth/leadership

Strong leadership with collaborators

Preferred OE supplier

Employee development

Superior returns to stake holders

Care for environment and society.

OTHER MANUFACTURERS COMPANY IN INDIA:-

There are following Manufacturers Company of piston, piston ring, piston pin and engine valves

in India which is given below

SAMKRG Piston & Rings – Andhra Pradesh

(IPL)India Piston Limited (A Group of Amalgamations) – Chennai

(SSPPL) Sintered Product Pvt. Ltd. –Headquartered in kosi kalan (North India)

(AIP) Abilities India Piston & Rings Ltd – Ghaziabad

Shriram Piston & Rings Ltd – Bhiwadi.

C O N T E N T

i. CERTIFICATE

ii. ACKNOWLEDGEMENT

iii. COMPANY PROFILE

1. INTRODUTION………………………………………………………………………[1]

1.1 COMPRESSION RING…………………………………………………………...[1]

1.2 SECOND RING…………………………………………………………………...[2]

1.3 OIL CONTROL RING…………………………………………………………….[2]

2. ABOUT THE PLANT………………………………………………………………....[2]

3. PISTON RING SHAPE………………………………………………………………..[4]

4. TYPES OF RING MADE IN THE PLANT………………………………………….. [5]

5. TYPES OF RING PROFILE…………………………………………………………..[6]

6. PROCESS SEQUENCE……………………………………………………………….[7]

7. MACHINING OPERATION DETAIL………………………………………………..[8]

7.1 GRINDING SECTION…………………………………………………………….[8]

7.1.1 ROUGH SIDE FACE GRINDER………………………………………….[8]

7.1.2 SEMI FINISH GRINDER………………………………………………….[9]

7.1.3 FINISH SIDE FACE GRINDER…………………………………………..[9]

7.2 LINE 1 SECTION………………………………………………………………….[10]

7.2.1 CAM TURNING AND GAP CUTTING MACHINE……………………..[10]

7.2.2 INTERNAL BORING MACHINE………………………………………...[11]

7.2.3 HONING MACHINE……………………………………………………...[12]

7.2.4 PROFILE TURNING MACHINE…………………………………………[13]

7.2.5 GROOVING MACHINE…………………………………………………..[14]

7.3 PCM SECTION……………………………………………………………………[14]

7.3.1 GAP GRINDING MACHINE……………………………………………[15]

7.3.2 GAP EDGE CHAMFER MACHINE……………………………………[15]

7.3.3 PROFILE GRINDING MACHINE………………………………………[16]

7.3.4 PARKERISING……………………………………………………………[17]

8. DEFECTS OCCURRED DURING MACHINING OPERATION……………………[18]

9. REJECTION ANALYSIS METHODOLOGY………………………………………[18]

9.1 TRACK OF THE LOT FOR REJECTION ANALYSIS…………………………[19]

9.2 PARETO ANALYSIS……………………………………………………………[20]

10. PREVIOUS IMPROVEMENTS TO REDUCE REJECTION………………………[20]

10.1 PROCESSING OF ALL CPC RINGS BELOW 120MM DIAMETER ON AUTO

OD GAP CHAMFER MACHINE…………………………………………………[20]

10.2 BEARING UNIT NECK THICKNESS REDUCED TO AVOID CHROME

BROKEN AT GAP DURING PROCESSING OF RINGS ON BORING

OPERATION…………………………………………………………………….[21]

11. SUGGESTION FOR REJECTION REDUCTION FOR FUTURE SCOPE………..[22]

11.1 SUGGESTION OF IMPROVEMENT………………………………………[23]

12. CONCLUSION………………………………………………………………………[24]

13. REFERENCE………………………………………………………………………….[24]

1. INTRODUCTION

Piston ring can be perfectly defined as the split ring with slight adjustment of diameter which fits

around the groove of the piston and seals the gap between the piston and cylinder wall.

Piston rings are widely classified into two types:

1. Compression ring

a. Top ring

b. Second ring

2. Oil control ring

Each of these rings uses distinct combination of materials, shape, heat treatment and surface

coating in contemplation of performance of its assigned function in optimality manner. The

design of these rings is a very critical job to carry upon to make it function properly. Its design

are made with respect to the combination of number of these rings in an engine. Some engine

requires 2 or 3 rings ranging till 6 per piston.

Functions of the rings –

Piston rings must accomplish three major principle functions,

Seal off the combustion chamber from the fuel mixture entering the crankcase

Limit and controlled regulation of oil consumption

Transfer the heat absorbed by the piston in the combustion process to the cooled cylinder

walls.

1.1 TOP RING-

This ring sit on top portion of the piston also referred as the upper compression ring. This ring is

operated at high thermal and mechanical loading. Its function is to form a gas-tight barrier

between the cylinder walls and the piston in order to the seal the combustion chamber. Another

function is to transfer the heat generated to the cylinder wall from piston and act like a bridge

between them.

Figure 1 Top ring

1.2 SECOND RING-

This is known as the lower compression ring. Its function is to work cumulatively with the top

ring to seal the combustion chamber and transfer the heat to the cylinder walls. These rings also

control oil ring. It does the job of both compression ring and oil ring.

1.3 OIL CONTROL RING-

It regulates and limit oil consumption. They scrape off excess lubricating oil from the cylinder

walls and return it to the crankcase. They are designed to provide a thin oil film to ensure piston

and ring lubrication. Improper control results in carbon residues or blue smoke in the exhaust gas

and results excessive oil consumption.

Application of piston ring is very wide. Some of them listed below-

Motor cycles, Passenger cars, Buses, Trucks, Motorsports, Large agriculture power generations,

Marine propulsion, Leisure RV’s, Small agriculture lawns and garden, Leisure crafts.

2. ABOUT THE PLANT

The factory located at Ghaziabad produces mainly three products pistons, piston rings and engine

valves. The piston ring has two plant namely C.I. Ring plant and the C2D1 Ring plant. The

C2D1 Ring plant is the point of interest in this project. The C2D1 plant is technically named

after the size of diameter made in this plant. C2 refers to the size range 121-140 mm and D1

refers to the size range 141-150 mm. C2D1 plant is the only plant which produces the chrome

rings.

Material used for manufacturing these piston rings are S.G. iron which is also known as the

ductile iron. Material which are widely used are as follow-

RIK- 10, RIK- 20a, RIK- 40B, RIK- 40S, SPR-02

Elemental composition chart of these materials are below-

Figure 2 Second ring

Figure 3 Oil control ring

Figure 4 Table showing all material composition

3. PISTON RING SHAPE:

Piston ring shape can be classified into three part according to the ovality namely:

1. Positive ovality: The measurement of the positive ovailty is done with the ring at its

free state. If the dimension of the ring measures from the back of the ring to the tip is

larger than the diameter measured across 90 degree, then the ring is said to be having

positive ovality. This causes an effect at the tips by the joint exert a high pressure against

the cylinder than other area of ring. This prevents the ring tips ‘fluttering’ at higher

engine speeds. Such rings are normally only specified on engines with higher RPM.

2. Negative ovailty: The measurement of the negative ovailty is done with the ring at its

free state. If the dimension of the ring measures from the back of the ring to the tip is

smaller than the diameter measured across 90 degree, then the ring is said to be having

negative ovality. Rings are specified with negative ovality to compensate for expansion at

operating temperature. As the ring warms, the heat can be concentrated at the ring tips.

These try to expand outwards, and by designing a ring with negative ovality, this effect

can be negated to create a ring exerting more even pressure around its circumference.

Rings with negative ovality were formerly used on slow speed 2-stroke diesel engines,

and are today widely specified on medium speed 4-stroke diesel engines.

3. Zero ovality: The measurement of the zero ovailty is done with the ring at its free state.

If the dimension of the ring measures from the back of the ring to the tip is equal to the

diameter measured across 90 degree, then the ring is said to be having zero ovality. Rings

with zero ovality are frequently specified for the latest slow speed 2-stroke diesel

engines.

Figure 5 Diagram depicting all the types of ovality

4. TYPES OF RING MADE IN THE PLANT:

Oil Ring

Plain Oil ring Oil chrome

HTCR

HTCR PGV

Compression ring

Chrome Compression ring

K.S. Chrome

Taper K.S. Chrome

Taper Chrome

K.S. Chrome PGV

Plain Compression ring

Taper

K.S. Compression

Taper K.S.

Taper Comp. IDB

Taper Comp. IDS

Plain

Taper napier

ODS Plain/Taper

5. TYPES OF RING PROFILE:

Napier ring: The Napier ring (also known as a Nasen ring) has a step machined into the lower

part of the running face. The upper part of the running face may be either square or with a taper.

Such a ring has a twisting effect when closed which allows the ring to

present a sharp downward edge to the cylinder which is effective at scraping

excess oil from the liner. The step provides a large area into which this oil

can be stored.

Rectangular Ring: Simple design with a square running face. Such rings are often un-coated, and

since the full ring face sits against the cylinder liner, such rings have a

relatively low contact pressure.

Taper faced: The taper faced ring allows the contact area between the ring and cylinder liner to

be reduced, thus proportionately increasing the contact pressure with the cylinder. Additionally

there is some pressure relief due to combustion gas pressure between the

top of the ring and the liner pushing the ring inwards. Such rings have

reduced running-in times and also provide some oil scraping function.

Internally Stepped Ring/Internal Chamfered Ring: By machining a step or a bevel onto the top

inside corner of the compression ring, the ring becomes subject to a twisting

or torsion effect when closed to working size and fitted into the liner. This

feature causes the bottom outside corner of the ring to make contact with the

cylinder liner thus providing good running-in characteristics and improved

oil scraping function. When combustion gas pressure is applied, the ring

running face is pushed flat against the liner.

Keystone Ring: This ring has a wedge shaped section. Thus the side faces of the ring are tapered.

This allows the clearance between the ring and the piston groove to vary as

the ring moves radially within the groove. This feature greatly reduces the

ring sticking in the piston groove, and is useful where the engine is for

some reason producing heavy combustion residues.

Slotted Oil Scrapper: Otherwise designated as SOC type this ring, has two scraping edges

separated by a groove. In the bottom of the groove are a number of slots

running to the inside of the ring. These allow oil gathered by the two scraping

edges to flow through, and be dispersed back into the engine via drain holes

drilled into the bottom of the piston groove. Such a ring can be supplied in

many different forms. The simplest and oldest is shown to the right with

square scraping edges.

6. PROCESS SEQUENCE

Figure 6 Process flow diagram production line

7. MACHINING OPERATIONS DETAIL

In C2D1 plant has a wide and huge space to accommodate various high-tech machining

equipment. The machining operations are divided into mainly three categories:

1. Grinding section

2. Line 1 section

3. PCM

The making of piston rings starts with the casting of the ring from molten metal

7.1 Grinding section-

Grinding section consist four machines namely rough grinder, semi-finish grinder, finish grinder,

and plunge grinder.

7.1.1. Rough side face grinder- Rough grinding machine is where the first operation starts. The

casted ring is first grinded in the rough grinding machine. In this operation the axial height of the

ring is decreased. About 1000-2000 microns of material is scraped out during this process. This

machine has got two grinding wheel horizontally placed in-between which the ring is passed. In

the input of the machine a slow moving v belt carrying the rings pass it to the machining portion,

where the grinding wheel is placed. The two grinding wheel are responsible for the stroke

removal. The output is constantly inspected for its axial height using a screw gauge.

Following are the brief detail of the machine unit:

Materials machined: - RIK -40B, RIK-40S, RIK-10, RIK-20A, RIK-25H and SPR-02

Tooling detail: -

1. Grinding wheel- 760x70x25.4 mm

2. Grinding wheel surface structure- Honeycomb

3. Grinding wheel material carborundum

4. Grinding wheel R.P.M.- 600-660 rpm

5. Dresser- Single pipe diamond dresser (0.75 carat)

6. Coolant- CIMSTAR (4.5-6 % max)

7. Guide strip- Thickness< axial height

Defects occurred-

1. Bad face- Irregular pattern on the radial face

2. Burn- Surface burned with black patch

3. Broken ring- Ring broken due to cracks

Figure 7 Diagram showing an example of burn defect

7.1.2. Semi-finish side face grinder- Semi finish grinding machine is where the second operation

starts. The rings after rough grinding is further machined in this machine. In this operation also

the axial height of the ring is decreased. About 150-200 microns of stroke is removed out during

this process. In input the rings are placed on the v shaped platform. This platform is attached

with a vibrator which helps in the forward movement of the rings. After this the rings are

displaced to the magnetic rotary drum which carries the ring to the grinding wheels for

machining to be done. Machined rings are brought adjacent to the input side by means of a

conveyor belt. On output the rings are inspected for the axial height.



Tooling detail: -








Defects occurred-




7.1.3. Finish side face grinder (plunge/diskus grinder) - Finish grinding machine is where the

third operation starts. The rings after semi finish grinding is further machined in this machine. In

this operation also the axial height of the ring is decreased. About 4-5 microns of stroke is

removed out during this process. These machines are vertical type whereas the rough and semi

finish grinders are horizontal type. These are fully autonomous machine. It is also built with two

grinding wheels but are vertically placed. The rings are stacked at input which is then passed to

the carrier plate. Carrier plate are circular disc with holes at 120o each. With the ring engaging to

the hole, the plate rotates and the rings are machined. After that the rings are robotically

collected through collector unit.



Tooling detail: -








Defects occurred-




7.2 Line 1 section:

After the grinding operation is done at line 1 the ring gets into the shape and profile. This section

consists of machines like cam turning, internal boring, honing, grooving, I.D. step and profile

turning.

7.2.1 Cam turning and gap cutting machine: Cam turning machine is a special turning

machine designed specifically for machining the piston ring. Since the rings are

initially oval in shape round turning is not possible, cam turning machine is used to

turn the oval shape. In order to start the process a no. of rings are stacked and

clamped in a cylindrical rod and levelled using a v block. The cylindrical rod is then

clamped to the machine. With the required setting according to the type of ring the

machining takes place over the outer surface i.e. along the axial height. After this the

rod is transferred to the gap cutting machine. Here using two parallel milling cutter

the gap is cut on the rings. With the rings with the gap is oval shaped and closing the

gap the shape changes to round. With the oval shape the gap is called free gap and

the round shape is called as closed gap with the precision of 0.00 mm.


Materials machined: - RIK -40B, RIK-40S, RIK-10, RIK-20Aand SPR-02

Tooling detail: -

1. CAM%- Selected as per process card

2. Ovality- Selected as per process card

Gap cutting tooling detail:

Material Diameter Feed value reading RPM Cutting material

RIK-40B/40S 40-100 400-450 250-300 H.S.S / Carbide

RIK-10/20A, SPR-02 40-100 400-450 250-300 Carbide

RIK-40B/40S 100.1-120 350-400 250-300 H.S.S / Carbide

RIK-10/20A, SPR-02 100.1-120 300-350 250-300 Carbide

Defects occurred-

1. Face dent- Dent present on the axial face

2. OD unturn- Incomplete machining on the outer surface

3. Unshape- Irregularity in dimension of radial distance

7.2.2 Internal boring machine: Internal boring machine is used to bore the internal side

face of the ring. This operation is followed by the cam turning operation. Tool used

in this operation is a five single point cutting tool attached to a thick disc shaped

attachment. This machine consist of vertical motor which rotates the spindle which

is attached to the tool. Rings are stacked to the machine in such a way that the

spindle is right at the internal portion of the ring. As the vertical motor starts the tool

rotates and bore the internal part of the ring.



Tooling detail: -

RING DIAMETER BEARING UNIT DIA.

57-74(& 74 OVER SIZE) 50,55

76-96(& 96 OVER SIZE) 65

98-108(& 108 OVER SIZE) 75

110-128(& 128 OVER SIZE) 90

130-150(& 150 OVER SIZE) 100

HOUSING RING DIA.

SMALL HOUSING 38~96

MEDIUM HOUSING 97~140

LARGE HOUSING 141~150

Defects occurred-

1. ID lining- Incomplete machining on the inner surface

2. ID burr- Burr at the inner surface

3. Gap broken- Gap is broken

4. Chrome broken- Chrome coating is broken

5. ID unturn- Incomplete machining on the inner surface

6. ID vibration- Irregular pattern due to vibration

7.2.3 Honing machine: Honing operation is one of the crucial operation in piston ring

production. During the cam operation the outer surface is machined with lining. This

lining has to be polished in order to get a smooth outer surface for further machining.

Honing sleeve selection is the first step in this operation, which is selected according

to the process card. After this the rings are stacked in the mandrel with intermediate

collars. The mandrel is inserted into the sleeve. The abrasive texture in the inner

surface of sleeve is responsible for polishing the outer lining of the ring. This

abrasive operation takes place through two motions, one is rotational and other is

translation motion. The spindle rotates along with vertical linear moment. This

process goes through no of cycles for specified time. This time is known as the

lapping time.



Tooling detail: -

1. Honing sleeve- Punch mark for diameter

2. Collar- Punch mark for diameter & Angle

3. Honing mandrel- As per ring diameter

4. Coolant- Fresh servo 46 mixed with 35gm 1000 grit emery

5. Dummy ring- 2-3 rings

Defects occurred-

1. Chrome broken- Chrome plating at outer surface

2. Granular plating- Granular patch on the surface

3. Dechrome- Chrome coating removal

4. Rehoning- This occurs improper machining

5. Gas leakage- Minute hole due to casting defect

6. Patch- Patch on the surface of the ring

7. Twisted ring- Twist in the split ring

8. Chrome at gap- Chrome plating broken at gap

7.2.4 Profile turning machine: Profile turning machine is where the ring is distinctly get

into shape. Each ring has specific function to accomplish and this is done through

ring profile design. Profile of ring is designed by a team of engineers with the

demand of the customer. Profile are made on the ring using computer controlled

lathe machine. In order to increase productivity and rejection five single point

cutting tool are combined and used to machine five ring at a time. Rings are stacked

in a string wrench with a dummy disc in between two rings. After that the rings are

clamped to the lathe machine and tightened. Following this machining takes place

and profile are generated.



Tooling detail: -

1. Basic collar left- D2= (D+0.5/D+0.3) SDE1.3/TD

2. Basic collar right- D2= (D+0.5/D+0.3) SDE1.3/TD

3. Distance collar- D1 Thickness as per chart

4. Clamping sleeve- D+0.5/ D+0.7/ D+0.3/ D+0.09 mm

5. Tool- as per the chart

Defects occurred-

1. OD unturn- Incomplete machining on the outer surface

2. Face dent- Dent present on the axial face

3. Vibration- Irregular pattern due to vibration

4. Profile centre- Shift in the centre of the profile due to improper machining

7.2.5 Grooving machine: Grooving machines are used to create groove on the side face of

the ring. Grooves are made to dispense the scraped oil around the piston groove.

These scraped oil is passed through the groove and transferred to the oil drain hole.

Groove machine contain a stack of multi point cutting tool clamped in a cylindrical

rod structure. Stack of ring is also clamped parallel to the cutting tool in such a way

that the middle portion of side face of the ring is exactly adjacent to the cutting tool.

With the rings remaining static cutting tool rotates and make the groove. The

machine is computer controlled and the cutting tool retracts back then stack of ring

rotates to change the side face for new grove machining.



Tooling detail: -

LIMITING PRESSURE

HTCR PGV/ IDCR (D+0.15) mm

HTCR (D+0.35) mm

PLAIN OIL (D+0.75) mm

HTCR CHROME (D+0.75) mm

SLEEVE/ COLLAR SIZE

25-30 kg/cm2

30-35 kg/cm2

Defects occurred-

1. Chrome broken- Chrome is broken at the slot

2. Face dent- Dent present at the surface

3. Vibration- Irregular pattern on the surface of the ring

7.3 PCM section:

PCM section is most intricate section in piston ring production. Every machining has to be taken

care of, even small irregularity could cause increased rejection. The word PCM stands for post

chrome machining which by name suggest that this section is works on ring after chrome plating

is done. This section consist of machines like gap grinder, gap edge chafer, profile grinder,

honing, and keystone grinding.

7.3.1 Gap grinding machine: After the chrome plating procedure one of the main

operation is gap grinding. This operation is very critical because of its contribution

to the rejection of the ring. Due to this reason this machine is always been a point of

interest for many engineers working on rejection reduction. Gap grinder is a

computer controlled machine having a grinding wheel which fits in between the ring

gap and grind it. A no. of ring are stacked and hanged in a T shaped bar. An arm is

provided to release single or a set of rings at a time. Ring is then grinded at the gap

with heavy supply of coolant in order to reduce chrome broken. Single ring or set of

rings are machined at a time according to the axial height of the ring. After the

machining the ring is then pushed through the sleeve and collected at the other end

of the machine.



Tooling detail: -

1. Grinding wheel- 125x1.5x22.23 mm

2. Grinding wheel designation- CB200R100BK8

3. Grinding wheel material- CBN (Cubic boron nitride)

4. Grinding wheel R.P.M.- 6000±200 rpm

5. Coolant- CIMSTAR (4-6 % min)

No. of rings per stroke Axial height

4 Up to 1.7 mm

3 1.7< B <2.5

2 2.5< =B <6

1 6< = B & Above

Defects occurred-

1. ID gap broken- Gap is broken at the inner surface

2. Slant gap- Gap cut is not proper


4. OD scratch- Scratch at the outer surface

7.3.2 Gap edge chamfer machine: Gap edge chamfer machine is used to create chamfer at

the gap edge. Chamfering is done to reduce stress concentration at the gap edge. This

machine is fully computerised, the ring is stacked in a T-shaped bar. Then a picker

arm picks few no. of ring and pass it for the machining. Two abrasive belt are

clamped of either side to chamfer the edge on both side. After then the rings are

collected in the T bar on the other side.



Tooling detail: -

1. Belt specification- 240 grit (10x350)

2. Sand paper- 80 grit (20mm dia.)

Defects occurred-

1. Chrome broken at gap- Chrome coating is broken at the gap

2. Chamfer unequal- Unequal machining of the chamfer

7.3.3 Profile grinder machine: Profile grinding machine is used to grind and polish the

outer surface of the ring. This machine uses a huge grinding wheel which grinds the

outer surface. Rings are clamped to the machine and grinding wheel grinds the side

face of the ring.



Tooling detail: -

1. Collar diameter- As per process card

2. Collar thickness- As per stage card

3. Dresser point- R0.2, 55o

4. Sleeve dia.- As per process card

5. Mandrel dia.- ɸ 69.6~ 106=58 mm, ɸ 106>80 mm

Defects occurred-

1. OD edge broken- Outer surface edge is broken

2. OD vibration- Irregular surface on the outer face

3. OD unground- Irregular machining on the outer surface

7.3.4 Parkerising: Parkerising is a chemical process done to make corrosion resistant ring.

A Piston ring has to work in extreme condition in such case corrosion is unbearable.

In order to prevent the ring from corrosion and make it wear resistant Parkerising

coating is applied on the ring. It is a method of protecting a steel surface from

corrosion and increasing its resistance to wear through the application of an

electrochemical phosphate conversion coating. Parkerizing is usually considered to

be an improved zinc or manganese phosphating process, and not to be an improved

iron phosphating process, although some use the term parkerizing as a generic term

for applying phosphating (or phosphatizing) coatings that does include the iron

phosphating process. Parkerizing is commonly used on firearms as a more effective

alternative to bluing, which is another electrochemical conversion coating that was

developed earlier. It's also used

extensively on automobiles to

protect unfinished metal parts

from corrosion. The Parkerizing

process cannot be used on non-

ferrous metals such as

aluminium, brass, or copper. It

similarly cannot be applied to

steel containing a large amount

of nickel, or on stainless steel.

Passivation can be used for

protection. Detailed flowchart of

the Parkerising process is shown.

Figure 8 Process flow diagram of parkerising operation

8. DEFECTS OCCURRED DURING MACHINING OPERATION:

The following list is the visual standard of the defect-

9. REJECTION ANALYSIS METHODOLOGY:

The process of analysis for rejection goes through various steps. To start with, the initial process

is to track and record rejection in each lots of ring. Then with all the recorded data Pareto

analysis is done. Pareto analysis is done in such cases where many possible causes are competing

and have to prioritize which cause is to be taken care of first. With the results from Pareto

analysis the defect contributing the most is selected and analysis are done on that particular

defect first. Following this there is a brainstorming session, where people operating the

respective machine causing the defect are called and asked for the reason for the defects. Then

after various careful calculation and experimentation solution for the rejection reduction is

established.

9.1 Track of the lot for the rejection analysis:

After tracking two lot of ring for the characteristics of defects occurred at each step of operation

it is been observed that chrome broken has a major contribution to the rejection. The lot which

was tracked are model XXX and YYY

1. Model name- XXX

Model type- CPC RING with KEYSTONE PROFILE

Material- RIK- 20A

Nominal dia. - 104.00 mm

Initial no. of rings in the lot- 2680

No. of rings before keystone operation- 2465

No. of rings at final inspection- 2236

Total rejection- 444

Rejection percentage- 16.56 %

2. Model name- YYY

Model type- CPC RING with KEYSTONE PROFILE

Material- RIK- 20A

Nominal dia. - 88.90 mm

Initial no. of rings in the lot- 2625

No. of rings before keystone operation- 2440

No. of rings at final inspection- 2312

Total rejection- 313

Rejection percentage- 11.92 %

CRI Inspection report for the YYY

It is been observed from the CRI report that the chrome broken has the major effect on rejection

rate. An average of 61.5 % of the whole rejection is chrome broken. After tracking and analysis

of the rejection rate it is been finalised that chrome broken is major contributor to the rejection

and studies is to be done on this defect.

9.2 PARETO ANALYSIS:

Pareto analysis is done on these models for prioritizing the causes and selecting the key

contributing cause. Pareto analysis graph is shown below-

From the graph top 4 defects are chosen along with the action plan which are as follow-

Chrome broken at gap (9.5%) - Action plan has been made for chrome broken at gap

Chrome broken at O.D. (2.3%) – 64% reduction

O.D. scratch (0.6 %) – 78% reduction

O.D. gap edge chamfer (0.09%)

10. PREVIOUS IMPROVEMENTS TO REDUCE REJECTION:

Processing of all CPC rings below 120mm diameter on auto OD gap chamfer machine

Processing of all CPC rings on D-150 cam turning machine

Buffing of entry portion of honing sleeve started to avoid chrome broken at O.D. during

insertion of mandrel in sleeve

Bearing unit neck thickness reduced to avoid chrome broken at gap during processing of

rings on boring operation

10.1 Processing of all CPC rings below 120mm diameter on auto OD gap chamfer machine:

Auto gap edge chamfer machine is used to create chamfer at the gap edge. Chamfering is done to

Figure 9 Pareto analysis chart

reduce stress concentration at the gap edge. This machine is fully computerised, the ring is

stacked in a T-shaped bar. Then a picker arm picks few no. of ring and pass it for the machining.

Two abrasive belt are clamped of either side to chamfer the edge on both side. After then the

rings are collected in the T bar on the other side.

All CPC ring below 120mm diameter are more prone to defects and has to be carefully handled.

For this purpose automatic gap edge chamfering machine is used. Figure of gap chamfering

machining process is given below.

10.2 Bearing unit neck thickness reduced to avoid chrome broken at gap during processing

of rings on boring operation: Internal boring machine is used to bore the internal side

face of the ring. This operation is followed by the cam turning operation. Tool used in

this operation is a five single point cutting tool attached to a thick disc shaped

attachment. This machine consist of vertical motor which rotates the spindle which is

attached to the tool. Rings are stacked to the

machine in such a way that the spindle is right at the

internal portion of the ring. As the vertical motor starts

the tool rotates and bore the internal part of the ring.

After the rings are machined they are passed through

the bearing unit. Since the neck of bearing unit is

thick it leads to slight expansion of gap and

ultimately the chrome is broken at the gap. To overcome

this the thickness of neck is reduced. Detailed diagram of

the bearing unit is given below.

Figure 10 Diagram depicting the edge chamfer operation Figure 11 Diagram depicting internal edge chamfering operation

Figure 12 Diagram depicting the neck thickness change in bearing unit

11. SUGGESTION FOR REJECTION REDUCTION FOR FUTURE SCOPE:

After observations it is been witnessed that gap grinding has a key role in chrome broken defect.

Gap grinding machine: After the chrome plating procedure one of the main operation is gap

grinding. This operation is very critical because of its contribution to the rejection of the ring.

Due to this reason this machine is always been a point of interest for many engineers working on

rejection reduction. Gap grinder is a computer controlled machine having a grinding wheel

which fits in between the ring gap and grind it. A no. of ring are stacked and hanged in a T

shaped bar. An arm is provided to release single or a set of rings at a time. Ring is then grinded

at the gap with heavy supply of coolant in order to reduce chrome broken. Single ring or set of

rings are machined at a time according to the axial height of the ring. After the machining the

ring is then pushed through the sleeve and collected at the other end of the machine.



Tooling detail: -

1. Grinding wheel- 125x1.5x22.23 mm

2. Grinding wheel designation- CB200R100BK8

3. Grinding wheel material- CBN (Cubic boron nitride)

4. Grinding wheel R.P.M.- 6000±200 rpm

5. Coolant- CIMSTAR (4-6 % min)

No. of rings per stroke Axial height

4 Up to 1.7 mm

3 1.7< B <2.5

2 2.5< =B <6

1 6< = B & Above

Defects occurred-

1. ID gap broken- Gap is broken at the inner surface

2. Slant gap- Gap cut is not proper


4. OD scratch- Scratch at the outer surface

During the ring is inside the sleeve the grinding operation initiates and grind the ring. After this

the ring is pushed by a pusher, while pushing the ring leans backward and the gap is regrinded

and chrome is broken at the gap. Another problem arose due to the sudden expansion of the ring.

When the ring is pushed outside the sleeve, ring in closed position is freed and ring expands.

This sudden expansion lead to chrome broken. Final problem which is been the most critical one

is the chrome broken at gap due to impact of the fall from upper T- shaped slide to lower T-

shaped slide.

11.1 SUGGESTION OF IMPROVEMENT:

Rubber support underneath the sleeve for preventing the ring from leaning backward

Welding a slope joint between upper T-slide to lower T-slide to supress the impact of fall

- Rubber support underneath the sleeve for preventing the ring from leaning backward-

Gap grinding operation starts with the stacking of the ring at the input area. These stacked

rings are released one by one through an automated arm actuating system. According to

diameter of the ring 2 or more rings are machined in a single cycle. After these set of

rings are released from the stack a jet stream of coolant is directed on these rings to wash

of the gap area and to tightly organise it. These rings are then pushed into the sleeve

through a pusher. Pusher diameter is slightly less than the sleeve diameter such that the

pusher fits exactly into the sleeve. Ring is then grinded inside the sleeve and then pushed

further by the pusher. During this pushing action the ring leans slightly backward. This

lean cause the ring to regrind when the ring touches the grinding wheel. This effect

caused the chrome broken defect at the gap. The reason for this failure was analysed and

came to a conclusion. The reason is the looseness of the sleeve which caused the free

movement in the ring and due to self-weight it lean backward. To overcome this failure a

rubber attachment is suggested to recover this loss. The logic behind this attachment is to

add more grip and tighten the loose joint between the ring and the sleeve. The rubber

attachment size may vary with different sleeve size. This suggestion might be

experimented for better results.

Figure 13 Diagram showing rubber attachment in the sleeve bottom: SIDE VIEW

- Welding a slope joint between upper T-slide to lower T-slide to supress the impact of fall-

After the machining operation the rings are then pushed out from the sleeve. Then the

fully machined rings are collected at the ring collector slide. Before reaching the ring

collector the ring has to follow a bumpy path. As shown is the figure above the rings has

to follow the path of upper T-Slide and the lower T-slide by finally reaching the end

portion i.e., ring collector slide. The upper T-Slide is an inverted T shaped stainless steel

rod designed such that it can accommodate rings. The ring gap fits into the inverted T-

shape with the lower flat portion bearing the ring. These T-rods are given a slight slope in

order to slide the ring in its path. When the ring passes from Upper T-slide to lower T-

slide it has to fall from a height of 3-4 cm. This fall creates an impact force on the ring

gap. The effect of impact leads to breakage of the chrome coating at the gap. Chrome

broken is the major drawback in the production of CPC ring. The chrome broken defect

at the gap grinding machine is quiet enlarged as in this machine once machining is done

and if there is any defect it has to be rejects. While in case of honing operation if

rehoning occurs the lapping time is increased to recover the defect. The solution for the

defect caused due to the fall can be recovered by welding a slide attachment to the upper

T-slide. The logic behind this suggestion is to allow a smooth path without any impact to

the ring. The ring will slides effortlessly from upper T-slide to the lower T-slide with no

impact which leads to chrome broken. The upper T-slide is adjustable to accommodate

grinding wheel adjustment. Due to this reason the slide attachment is to be welded to the

upper portion only by making the upper T-slide detachable.

Figure 15 Diagram showing the two T-Slide of the gap grinding machine Figure 14 Diagram of the concept of slide attachment

12. CONCLUSION:

Methodology for rejection reduction was successfully submitted to my industry guide and

discussed about the outcome. In near future the new suggestion might be implemented if

successfully experimented. I feel proud in rendering my service to SHRIRAM PISTONS AND

RINGS LTD.

The internship gave me an opportunity to get a hands on experience of shop floor and the

required engineering problem solving techniques. Granted a chance to visit the complete

manufacturing line, I now understand the mechanisms concerned to the industry and my

curriculum. Being in the C2D1 ring manufacturing plant I gained an opportunity to closely

observe the working and management of manufacturing operations along with the live hurdles

and their solutions. After viewing the world class manufacturing process by myself, I feel

honored to get associated with such a well renowned company and with such a hard working

team.

13. REFERENCE:

Website:

www.shrirampistons.com

Books:

Company catalogue book

http://www.shrirampistons.com/

Date post:	12-Apr-2017
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