Internship Report Final.docx

Study of processes involved in manufacturing of high speed gear TM3G3489 1.0 COMPANY PROFILE Triveni Engineering & Industries Limited is a focused, growing corporation having core competencies in the areas of sugar and engineering. The Company is one amongst the largest sugar manufacturers in India and the market leader in its engineering businesses comprising high speed gears, gearboxes, and water treatment solutions. With 7 sugar mills, 6 co-generation units and 1 distillery spread over 8 locations in Uttar Pradesh, we progressively engage with over 250,000 farmers through our cane marketing and development programs. As the largest Indian manufacturer of high-speed and niche low speed gears and gearboxes, Triveni commands a dominant market-share in the gears market in the region. As a focused player in water treatment domain, we offer end-to-end services & product mix in the technology spectrum of water and waste water treatment. We have a dedicated manufacturing and R&D unit each for Gear and Water Treatment Applications at Mysore and Noida respectively. Our two major business segments – sugar and engineering - are mutually exclusive in terms of growth factors and environment. The sugar business is immune to the upheavals in the global economy, and is dependent only on the sugar cycle. Our engineering businesses cater to the two most critical industries – power and water. Our steam turbine business, located at Bangalore has been demerged through a scheme of arrangement into Triveni Turbine Limited (TTL) from the appointed date on 1st October 2010, and the same has become effective w.e.f. 21st April, 2011. Triveni Engineering & Industries Limited holds 21.8% equity capital of Triveni Turbine Limited

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Study of processes involved in manufacturing of high speed gear TM3G3489 2.0 BUSSINESS OVERVIEW Triveni Gears, Gear Business Group of Triveni Engineering & Industries Ltd., is the largest manufacturer of high speed gears and gearboxes in India for steam turbines, gas turbines, compressors, pumps, blowers as well as special purpose industry applications designed as per API, AGMA. DIN, ISO and other international standards. Triveni Gears also manufactures niche low speed gearboxes for mini Hydel turbines, Steel mills, sugar mills, rubber mixers and extruders, cement mills. Thermal plants and plastics etc. Reliability built through superior technology, manufacturing and product quality combined with 38 years of rich experience in high technology gears are our key strengths that lead to develop customized gear drives, meeting tough demands of Industries across high speed as well as Niche slow speed applications. Triveni Gears offers end-to-end solutions in high-speed gears and gearboxes. Started in 1976, with the objective to fulfil the Company's captive demand for high-speed gears, over these years, it has become the dominant supplier to all major OEMs in the country. With unmatched capabilities in the design and development of all types of gears and gearboxes, combined with an ultra-modern manufacturing facility the Company is poised to "Gear the Future". Triveni Gears and Lufkin Industries, LLC (part of GE-Oil & Gas) joined hands, way back in the year 1998 through strategic technology license agreement to redefine gear transmission technology in India. Over the last decade and a half, the technology license from Lufkin has been expanded with respect to product range, applications and geographies, now designated to countries in South East Asia, parts of Africa and South Asia. Lufkin has been a world leader in high speed gear applications as well as Niche low speed and has been in the field of gears for over a century. Lufkin's commitment to excellence has been supported by an extensive research and development as well as modernization programme. Customers worldwide depend on Lufkin for their continuous commitment to technological innovation and engineering experience in mechanical transmission. Superior product technology coupled with rich experience of Lufkin and combined with exceptional problem solving

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Study of processes involved in manufacturing of high speed gear TM3G3489 capabilities allows Triveni Gears to produce customized Gear drives which meet the tough quality and specification demands of the industry. License agreement would include technology transfer from design, manufacturing and service for new build and aftermarket coupled with technical support and training to Triveni Gear's personnel. While Triveni Gears manufactures gearboxes for (below 7.5 MW applications using its own technology, and the license covers above 7.5MW) all high speed and niche low speed applications.

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Study of processes involved in manufacturing of high speed gear TM3G3489 3.0 MILESTONES 

2014 Supplied 15MW test rig gearbox for testing 1000MW capacity generator Frame6 load gearbox order from USA 27680 rpm drop in replacement of integrally geared API 613 gearbox for a refinery in SE Asia Won CII EXIM Bank Award second year in row for Business Excellence 2014 – Strong commitment to Excel

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2013 New Product Development – 850 KW Planetary Gearbox supplied for sugar mill drive application Commissioned for first time indigenously manufactured drop-in replacement unit for LM6000 Gas Turbine load gearbox for India's leading petrochemical company. OHSAS 18001 certified Won CII EXIM Bank Award for Business Excellence 2013 – Strong commitment to Excel

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2012 Exclusive MOU with BHEL signed for gas turbine Load gears CE Certification Went Live on SAP across all functions Implemented 5S and Kaizen

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2011 Highest power local gearbox for 38MW for India's largest automobile company Highest API-613 30 MW gearbox for the largest petroleum refinery Highest 70,000 RPM gearbox for defense test rig Renewal of High Speed license agreement with Lufkin for another 12 years, includes Gas Turbine Load gears and ASEAN countries as additional territories, and local manufacturing up to 62 MW Signing of LSLA with Lufkin for Metal & Steel, Rubber & Plastics Commissioning of 1.6 MW fully instrumented Test Rig for testing of high power upto 90MW gearboxes- exclusive Test facility in India.

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2010 Long term strategy and visioning Plant upgraded to manufacture and handle 2 meter dia gears Page 4

Study of processes involved in manufacturing of high speed gear TM3G3489 

2009 First locally manufactured drop-in replacement of Frame-6 gear box at for India's leading petrochemical company

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2008 CFT training on high power high speed technology at Lufkin-US First order for SE Asian palm oil market in Indonesia Kaltimex Balance score card PMS implemented

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2007 Establishment of global supply chain for raw- materials First lot of gear sets shipped to a leading engineering company in Germany for 20MW geared fluid coupling Setting up of full fledged in-house metallurgical testing facility First high power 6 MW vertical offset hybrid configuration for Hydro turbine

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2006 Retro fit of High power Gas Turbine Load Gearboxes at ASEB and GEB Development of first integrally geared 37935 rpm compressor designed/manufactured gearbox for a public sector engineering conglomerate

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indigenously

2005 Renewal of High speed agreement and with enhanced local manufacturing up to 25MW & added geographies CNC hobbing and profile grinding technology adopted Retro fit of vertical roller mill for Cement Segment Plant layout optimization, technology and infrastructure up gradation

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2004 Competency mapping and development through one of the leading HR consulting companies

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2003 Hydel technology training at France Visioning and Six Sigma initiative

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2002 First export supply to Singapore of API Gearboxes

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2001 Page 5

Study of processes involved in manufacturing of high speed gear TM3G3489 Retro fit of 25 MW gearbox for a leading Cement company from India High Power Hydel -vertical axis -2.5 MW 

2000 Oracle based ERP Pro-E platform for entire business

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1999 First high power gearbox 10 MW for a leading sugar company in South India Commissioning of Test rig for testing upto 35 MW Gearbox

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1998 CFT Training on High power High speed technology at Lufkin – US ISO 14001 Certified

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1997 Business Process Reengineering initiated through a world leading consulting company

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1996 Replacement for IH I Compressor Gear sets - 32000 RPM and 28000 RPM for India's leading petrochemical company First High Power API-613 for Refinery blower application

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1993 First High Speed 6 MW API - 613 Gearbox for a Refinery in South India. ISO-9001 Certified First in Gear industry

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1992 First Gearbox for High Speed Test Rig for defense segment

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1990 Precision grinding facility extended with addition of Hoffler Grinding Machines.

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1987 First Supply of indigenized Traction gears for Rajdhani Express (Indian Railways)

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1982 First Hydel gearbox shipped to site

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1981 First retrofit supply to shipping industry for crude oil pump turbine gear set 1980 First gearbox supplied to a non-captive steam turbine OEM

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1976 Unit started at Mysore, to cater to captive consumption

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Study of processes involved in manufacturing of high speed gear TM3G3489

4.0 QUALITY & CERTIFICATIONS Every Triveni product passes through the stringent quality checks from raw material to final run test, assembly and packing to ensure that product meets or exceeds customer expectations. We have an in house metallurgical laboratory with state-of-the-art equipment to inspect the raw material properties, grain size, inclusions, banding and micro structure. This also ensures complete quality requirements of the case hardened Gear teeth as regards to the hardness gradient, case and core hardness and microstructure. Core raw material chemical composition and carbon percentage in heat treated teeth are tightly controlled through sophisticated optical spectrometer. The installation of magnetic particle testing and surface etch inspection also ensures defect free gear teeth that last long. All these equipment and quality infrastructure undergo predetermined calibration regime. These also include heat treatment furnace and quenching stations to consistently produce high quality gear. Triveni's mechanical run test stand consist of three fully instrumented test benches of 1600 KW, 600 KW & 200 KW capacities with capabilities of tandem testing. Process capability is established across processes in the complete value chain from raw materials to finish product. Test beds are equipped with 

Bently Nevada vibration monitoring system with ADRE

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Vibration analyzer SKF Micro log

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Noise analyzer.

CERTIFICATION 

ISO-9001 : 2008 for QMS

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ISO-14001:2007 for EMS

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OHSAS-18001

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CE certified for self-certification of Gearbox and accessories

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CII-Exim Bank award for Business Excellence for "Strong commitment to Excel". Page 7

Study of processes involved in manufacturing of high speed gear TM3G3489

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CE

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Study of processes involved in manufacturing of high speed gear TM3G3489

ISO 14001 : 2004

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Study of processes involved in manufacturing of high speed gear TM3G3489

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Study of processes involved in manufacturing of high speed gear TM3G3489 ISO:9001:2008

OHSAS Page 11

Study of processes involved in manufacturing of high speed gear TM3G3489 

AGMA MEMBER

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Study of processes involved in manufacturing of high speed gear TM3G3489 5.0 OUR PRODUCTS 5.1. SALIENT FEATURES

Fig 1 Gear box We follow international standards for manufacture of Gearboxes. Engineered to order gearboxes are supplied with Gear internals having single or double helical tooth profile. All critical operations for the rotating elements from Gear hobbing, heat treatment, surface grinding -and teeth grinding are all carried out in-house. Gears are made of alloy steel forgings sourced from approved vendors as per stringent standards. Gear sets are housed in robust but value engineered cast iron/ fabricated housing. Accessories to Gearboxes like shaft driven oil pump/ lube oil system / barring gear system are sourced from approved supplier partners.

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Study of processes involved in manufacturing of high speed gear TM3G3489 5.2. TYPES OF GEARS AND GEARBOXES

Fig 2

Fig 3

Helical and double helical gear drives

Single stage and multi stage gear drives

Fig 4 Planetary gear drive Page 14

Study of processes involved in manufacturing of high speed gear TM3G3489 6.0. APPLICATIONS

Table 1

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Study of processes involved in manufacturing of high speed gear TM3G3489 Table 2

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Study of processes involved in manufacturing of high speed gear TM3G3489 Table 3

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Study of processes involved in manufacturing of high speed gear TM3G3489

7.0 Key strengths •

Technological advantage by virtue of License agreement with Lufkin Inc., USA (Now a part of GE –Oil & Gas ), world renowned gear company

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Engineered-to-order gearbox solutions upto 62 MW under technology license from Lufkin

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Proven track record of supplying high speed high power gearboxes coupled with Niche low speed gearboxes for the past 38 years cumulating to 8000 Gearboxes

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One of the few gear companies in the world having a turbine back up

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Brand acceptability across global OEMs – operating in India and Asia

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Design capability to address 62 MW power, 70,000 rpm speed

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Gear are designed to meet all global standards like AGMA, API, ISO, DIN and the only company in India approved for API standard gearboxes as per latest edition

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Vast clientele across industry segments and application spectrum

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Vast application knowledge from the system perspective

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Experienced and skilled Manpower

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Integrated manufacturing facility capable of testing 90 MW Gearbox, handling 70 tonnes and producing 2 mtr diameter gears

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Trouble shooting and diagnostics expertise

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Experience of reverse Engineering of 80+ global makes of gearboxes through replacement, repair and refurbishing route for more than 25 years

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Study of processes involved in manufacturing of high speed gear TM3G3489

8.0 Technology •

Adopting to Global Standards like AGMA, API and DIN

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Case Carburized, Hardened and Ground Gears upto 2 Meter diameter

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Double Helical and Single Helical gearings both Internal and External

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High Efficiency using Double Helical Gearing for high power

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Pressure Dam bearing for low vibration under low load conditions

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Robust Casing design offering both Dry sump and Wet sump designs

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Proven designs across small to very high power range, across applications and speeds as high as 70000 rpm

• Unique Hybrid design for Vertical Offset hydro turbine Gears

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Study of processes involved in manufacturing of high speed gear TM3G3489

9.0 Our clients

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OEM’s: Steam Turbine, Gas Turbine, Hydro Turbines Pumps, Compressors, FD and ID Fans, Marine Propulsions, Test Rigs.

•

Direct Users (for replacement solutions), Refineries, Cement plants, Steel Plants, Paper plants, Petrochemical, Fertilizers plants, Rubber and Plastics processing and other process companies in India and nearby countries.

10.0 Industries served Wide variety of gearboxes are required for varied industry segments such as Power, Sugar, Refinery, Fertilizer, Steel, Cement, Rubber, Plastics etc, Industry Segments 10.1 Power Generation Geared drives •

Steam Turbine Generator

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Hydel Turbine Generator

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Geo-thermal (Steam Turbine Generator)

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Bio-mass (Steam Turbine Generator )

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Palm Oil ( Steam Turbine Generator )

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Gas Turbine and Accessory Gearbox

Non Geared drives •

Boiler feed pump

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Coal Mill drives

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Coal Pulverizer

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Study of processes involved in manufacturing of high speed gear TM3G3489 10.2 Fertilizer industries •

Steam Turbine Generator

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Carbomate Pump

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Ammonia Pump

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Boiler Feed Water Pump

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Compressor

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Granulator

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Dryer

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Wagon Tippler

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Blower

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Agitator

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Gas Turbine and Accessory Gearbox

10.3 Sugar industries •

Steam Turbine Generator

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Primary & Secondary Gearbox for mill and Fibrizor Drive

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Cane chopper / Shredder Gearbox

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Boiler Feed Water Pump

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Planetary mill drive gearboxes

10.4 Steel and cement industries •

Steam Turbine Generator

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Boiler Feed Water Pump

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Mill Stands ( Pinion stand / combined pinion stand for cold roll mill, Hot Strip Mill ).

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Briquetting Press / Share Press

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Study of processes involved in manufacturing of high speed gear TM3G3489

11 INTRODUCTION Gears are toothed members which transmit power / motion between two shafts by meshing without any slips. In any pair of gears, the smaller one is called pinion and the larger one is called gear immaterial of which is driving the other. When pinion is the driver, it results in step down drive in which the output speed decreases and the torque increases. On the other hand, when the gear is the driver, it results in step up drive in which the output speed increases and the torque decreases.

(Fig 5) Types of gears

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Study of processes involved in manufacturing of high speed gear TM3G3489

11.1 GEAR NOMENCLATURE

(Fig. 6) Gear tooth Terminology

Addendum: The addendum is the height by which a tooth of a gear projects beyond (outside for external, or inside for internal) the standard pitch circle or pitch line; also, the radial distance between the pitch diameter and the outside diameter.

Pitch circle: A pitch circle (operating) is the curve of intersection of a pitch surface of revolution and a plane of rotation. It is the imaginary circle that rolls without slipping with a pitch circle of a mating gear.

Module: Module, m this indicates the tooth size and is the number of mm of pitch circle diameter(p.c.d.) per tooth

Pressure angle: Pressure angle in relation to gear teeth, also known as the angle of obliquity, is the angle between the tooth face and the gear wheel tangent.

Dedendum: Definition of dedendum plural: The root of a gear tooth also the distance between the dedendum circle and pitch circle of a gear wheel or rack

Root circle diameter: Root Diameter (R.D.) is the diameter of a circle around the bottom (root) of the gear tooth space.

Base circle: The circle of an involute gear wheel from which the involute forming the outline of the tooth face is generated.

Back lash: Backlash is defined as the amount by which width of tooth space exceeds the tooth thickness of engaged gear when measured on pitch circle.

Face width:The face width of a gear is the length of teeth in an axial plane. For double helical, it does not include the gap. Page 23

Study of processes involved in manufacturing of high speed gear TM3G3489 PROCESS PLAN FOR HIGH SPEED GEAR TM3G3489 Table 4 PROCESS NO

PROCESS

CONTROL PARAMETERS

STD HOURS

1

RAW MATERIAL INSPECTION(QA)

As per Drawing

00

2

TURNING AND FACING

As per Drawing

03

3

DRILL AND TAP

As per Drawing

0.75

4

HOBBING(QA INSPECTION)

No of teeth 159 Module 4.233mm

3.5

5

CARBURIZING(QA INSPECTION)

Case depth 1.5 to 2.1mm

24

6

MACHINING AFTER CARBURIZING

As per Drawing

2.5

7

HARDENING(QA INSPECTION)

60 to 63 HRC

10

8

TEMPERING

150 T0 180 deg

8

9

SHOT BLASTING

By steel shots/grits

10

MACHINING AFTER HARDENING

As per Drawing

3.5

11

DRILL AND TAP

As per Drawing

2.5

12

BORE AND Ist FACE GRINDING

As per Drawing

3

13

TEETH GRNDING(QA)

No of teeth 159 Module 4.233mm

3.75

14

OD AND 2nd FACE GRINDING

Allow it to dry

2.5

15

DEBUR AND DP TEST(QA)

As per data sheet

00

16

BALANCING PREPARATION

As per data sheet

4.0

17

DYNAMIC BALANCING(QA INSPECTION)

As per std

4.0

18

DIMENTION INSPECTION

As per drawing

00

2

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Study of processes involved in manufacturing of high speed gear TM3G3489 13 GEAR MANUFACTURING PROCESS INVOLVED 1.

BLANKING

2.

DRILL AND TAP

3.

HOBBING

4.

CARBURISING

5.

MACHINING AFTER CARBURISING

6.

DRILL AND TAP

7.

HARDENING

8.

TEMPERING AND COOLING

9.

SHOT BLASTING

10. MACHINING AFTER HARDENING 11. DRILL AND TAP BETWEEN RIM AND HUB 12. BORE,FACE AND OD GRINDING 13. KEYWAY MACHINING 14. SHRINK FITTING 15. TEETH PROFILE GRINDING 16. DEBUR AND DP TEST 17. DYNAMIC BALANCING 18. FINAL DIMENDION 19. ASSEMBLY

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Study of processes involved in manufacturing of high speed gear TM3G3489 13.1 GEAR BLANK MACHINING Quality of gear manufacturing starts with blank machining. Accuracy in blank machining is a necessity for attaining the desired quality standard of finished gears. According to shape, the gears are called round gears and shaft gears. For round gears, the dimensional and/or inter-related tolerances that must be closely controlled are as follows:  Size of the bore (inside diameter).  Out of roundness or straightness of bore.  Squareness of the bore axis with respect to face.  Parallelism of the two faces.  Outside diameter and runout with respect to bore. Different defects in blank machining and their effects in subsequent gear manufacturing are: 1. Oversize bore results in poor clamping efficiency of the gear. Even a slight tendency to slip on the work holding arbour may cause lead error. Geometrical error of the bore also results in poor work holding efficiency. 2. Error in perpendicularity of the bore axis with respect to the locating face, results in lead error and variation in lead. 3.

Excessive parallelity error of work clamping face with respect to work locating surfaces, results in non-uniform clamping and may twist the blank. In stack hobbing (when numbers of blanks are placed one over the other and are cut simultaneously), it causes lead error.

4. Excessive eccentricity of the outside diameter with respect to bore results in uneven cutting load and causes varying tooth depth around the periphery. Round gear blanks are machined generally in two setups on many types of chucking lathes. Threeoperation blank finishing ensures clean outside diameter. Two-operation finishing leaves a step on outside diameter. However, with accuracy of present work holding chucks, the amount is well within a limit that does not cause any trouble for ultimate performance. For shaft gears, the axis of rotation is created by a face milling and centring operations on both the ends. The accuracy of the operation is Page 26

Study of processes involved in manufacturing of high speed gear TM3G3489 important to maintain accuracy in the subsequent operations. Generally a protected type centre drill is used to avoid damage to the actual locating surface of the centre during handling. Shaft gears blank machining requires careful planning to achieve the concentricity between different locating surfaces and gear diameters. The tailstock pressure and the cutting forces may bend the shaft depending upon the length/diameter ratio that may necessitate a judicious application of welldesigned steady rest. 13.2 HOBBING Gear hobbing is a generating process. The term generating refers to the fact that the gear tooth form cut is not the conjugate form of the cutting tool, the hob. During hobbing both the hob and the workpiece rotate ill a continuous rotational relationship. During this rotation, the hob is typically fed axially with all the teeth being gradually formed as the tool traverses the work face. For a spur gear being cut with a single start hob, the workpiece will advance one tooth for each revolution of the cutter. While bobbing a twenty-tooth gear the hob will rotate twenty times, while the workpiece will rotate once. The profile is formed by the equally spaced cutting edges around the hob, each taking successive cuts on the workpiece, with the workpiece, in a slightly different position for each cut. Several cutting edge of the tool will be cutting at the also time. The hob is basically a worm with gashes cut axially across it to produce these cutting edges. Each cutting tooth is also relieved radially to provide chip clearance behind the cutting edge. This also allows the hob face to be sharpened and still maintain the original tooth shape. The final profile of the tooth created by a number of flats blending together. The number of flats corresponds to the number of cutting gashes which pass the workpiece tooth during a single rotation. Thus, the greater the number of gashes in the hob, the greater the number of flats along the profile which improves the "smoothness" of the tooth profile.

(Fig. 7. Gear Hobbing process)

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Study of processes involved in manufacturing of high speed gear TM3G3489 13.3 THE GEAR HOBBING MACHINE: A gear hobbing machine consists of five common elements:  A work spindle to rotate the work.  A hob spindle to rotate the hob.  A means of rotating the work spindle and hob spindle with a constant of ratio, depending on the number of teeth in the workpiece and the number of threads ill the hob.  A means of traversing the cutting too across the face of the work in the direction of the work axis for spur and helical gears.  A means of adjusting the centre distance of the work and the hobs for different size workpieces. 13.4 THE HOB: As more and more threads are designed into the tool, the lead of the thread will increase. Normally. A thread lead angle of 2-6° will be acceptable. Beyond six degrees, the left and right side of the cutting tooth will be loaded unequally, which will cause poor tool life. To compensate for this problem, the diameter of the tool can be increased slightly but with a reduction in RPM to maintain the same SFM. Alternatively, the gash of the hob can be made helical to position the cutting tooth perpendicular to the cutting action. In Triveni gears we found that there are two Hobbing machines. The Gear wheels of OD 75 mm to 2000 mm can be machined here from different hobs having module from 2 to 35. If pinions are machined, they are held between the centres and if gear wheels are machined they are supported on fixtures. The Job is usually made of 17CrMnNi6 material and the hob is made of ASP2030 material. The helix angle of up to 45° can be cut. The hobbing also depend on Span, Apex and MR. If we draw an imaginary tangent to the pitch circle, then the length of the tooth which come under this tangent is known as span. The measurement is done between two rollers keeping each side on the gear profile which gives Measurement over roller. The coolant used is Garia20.

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Study of processes involved in manufacturing of high speed gear TM3G3489

Fig 8 Gear part and hob The Typical Machine setting data for the Hobbing Process is as given below: Table 5 01

No. of Teeth

159

02

Module

4.2333

03

Direction of Helix

Left Helix

04

Standard Helix Angle

8° 17’ 37.30”

05

Pressure Angle

20°

06

Face Width

160.3 mm

07

Tip Circle Diameter

688.1.21 mm

08

Tooth Depth

10.61/10.74

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Study of processes involved in manufacturing of high speed gear TM3G3489

13.5 HEAT TREATMENT PROCESS The heat treatment process is one of the most important processes that happen in order to improve the various properties of the material of the metal. It is a crucial process because in the absence of this process the manufactured gear will not be able to bear the extreme loads in the working environment. The heat treatment unit at Triveni Gears in Mysore has a list of processes which include carburizing, quenching, tempering and shot blasting. WASHING CARBURIZING

QUENCHING

TEMPERING

SHOT BLASTING

Sequence of operations followed for heat treatment. The facility at ‘Triveni Gears Private Limited’ has a washing machine in order to clean the hobbed gear component of external impurities. There are two carburizing furnaces where the component can be subjected to high temperatures and subjected to the carburizing cycle. The quenching chamber is essentially a hardening process where the change in the micro structure properties of the metal takes place. The tempering process is followed after the quenching process in order to relieve internal stresses and decrease the brittleness of the material. The final process is the shot blasting process where the scales formed due to annealing are removed.

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Study of processes involved in manufacturing of high speed gear TM3G3489 13.5. 1 CARBURIZING PROCESS

Carburization is a heat treatment process in which iron or steel absorbs carbon liberated when the metal is heated in the presence of a carbon bearing material, such as charcoal or carbon monoxide, with the intent of making the metal harder. Depending on the amount of time and temperature, the affected area can vary in carbon content. Longer carburizing times and higher temperatures typically increase the depth of carbon diffusion. This process follows the process of washing where the external impurities are removed. The carburizing processes followed for the hobbed gear wheel and hobbed pinion is slightly different.

TEST PIECE FROM QA

HOBBED PINION

HOBBED GEAR WHEEL

CHECK FORCASE DEPTH, HARDNESSS

APPLYING ANTI CARBURIZING PASTE

CARBURISING

HARDENING MACHINING AFTER CARBUSRIZING

Fig 9 Carburizing process Page 31

Study of processes involved in manufacturing of high speed gear TM3G3489

13.5 .2 CARBURIZING PROCESS SEQUENCE

The carburizing process employed at the plant involves the use of two organic fluids which are acetone and methanol after the component is subjected to a particular temperature. The first liquid introduced in the furnace has a function of scavenging the furnace and also providing the desired positive pressure during the carburizing furnace. The liquids are supplied in drops at a particular rate. The second liquid cracks to form the desired carbon potential. The advantage of this process is that the carbon potential can be controlled and the need for an endothermic gas generator is eliminated. In this plant methanol is used as the carrier gas and acetone as the carburising agent. During carburizing methanol splits into carbon monoxide and hydrogen while acetone would give carbon along with the above products. CH3OH CH3COCH3

CO + 2H2 2C + CO + 3H2

The whole process is carried out in two cycles called the active and the deficient cycle. When the carbon concentration of 1% is reached, it is termed the active cycle. When the carbon concentration of 0.7 % is reached, it is termed as the deficient cycle.

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Study of processes involved in manufacturing of high speed gear TM3G3489 13.5 . 3 QUENCHING Quenching is the process of rapidly cooling a material from high temperature to obtain certain material properties. The thickness of the material to be quenched along with the rate of cooling required helps to choose the quenching medium. The quenching medium of oil is chosen. If a quenching medium that cools slower than the required rate is chosen, the quench is not effective in producing the required microstructures and hence properties. On the other hand, if a quenching medium that cools faster than the required rate is used, then that can sometimes lead to defects such as warping and cracking. It prevents low-temperature processes, such as phase transformations, from occurring by only providing a narrow window of time in which the reaction is both thermodynamically favorable and kinetically accessible. Quenching process introduces hardness in the steel by transforming it into martensite.

Fig 10 Time Temperature Transformation curve for steel During the quenching process the metal is dipped in heated oil at a temperature of about 800 degree Celsius and cooled suddenly in a cooling pit in a very small time frame. The cooling agent used is solid carbon dioxide which can maintain a temperature of -80 degree Celsius. At this very low temperature the crystalline structure of steel changes from austenite to martensite which is a very hard structure of steel. So this is also termed as the hardening process. Low viscosity accelerated quenching oils are used mainly in hardening plain carbon and alloyed quenching and tempering steels. Good penetration and / or through-hardening can be achieved. Page 33

Study of processes involved in manufacturing of high speed gear TM3G3489 13.5.6 TEMPERING Tempering process follows the quenching process because of the drawbacks associated with quenching. Although quenching introduces hardness in the material, it also has the following drawbacks: 

Martensite obtained after hardening is extremely brittle and will result in failure of engineering components by cracking.



Formation of martensite from austenite by quenching produces high internal stresses in the hardened steel.



Structures obtained after hardening consists of martensite and retained austenite. Both these phases are metastable and will change to stable phases with time which subsequently results in change in dimensions and properties of the steel in service.

In the plant tempering process is carried out by heating the quenched component to a temperature of about 160 degree Celsius for a specified time frame.

Fig 11

Temperature v/s Hardness curve

It is observed that the increase in the tempering temperature decreases the hardness and internal stresses while increases the toughness. Therefore a tempering process is a payoff between achieving good toughness and losing the hardness. Depending on the application of the end product the hardness of the component is maintained.

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Study of processes involved in manufacturing of high speed gear TM3G3489 13.5.7

SHOT BLASTING PROCESS Shot blasting is a method used to clean, strengthen (peen) or polish metal.

After the process of quenching, scale formation occurs on the surface of the metal. These scales remain even after the tempering process which is primarily to increase the toughness. Therefore shot blasting is a necessary finishing process. Aluminium oxide is blasted on to the steel. Aluminium oxide (AL2O3) is a man-made fused alumina that is very tough, angular shaped, medium density with hardness of 9 on the Mohs scale. This is abrasive is designed for designed for high blasting pressure up to 90 PSI. Aluminium oxide is very good for light deburring and surface prep (bonding strength) prior to painting and coating.AO creates a dull matte finish. Aluminium oxide has media life of approximately 10-12 times through the blast system. Shot blasting is used in almost every industry that uses metal, including aerospace, automotive, construction, foundry, shipbuilding, rail, and many others. There are two technologies used: wheel blasting or air blasting.

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Study of processes involved in manufacturing of high speed gear TM3G3489

13.6

Effect of Heat treatment

Gear size and accuracy Heat treatment processes produce changes in tooth geometry. The gear profile exhibits a drop after heat treatment depending on the module. Helix angle of gears becomes decreased, as the helical tooth tends to straighten. The gear with higher helix angle will have more increase in lead. There is certain growth or shrinkage on the pitch circle diameter (measured over pins or balls) of the gears. Pitch circle diameter of inside splines shrinks and exhibits out-ofroundness error. The pitch circle diameter increases in case of solid external gears. Some important factors responsible for these changes are as follows: 

Hardenability of gear material. Z



Forging practices.



Cutting tools used in machining e.g. shaving cutter, broach etc.



Work support and pattern of loading in carburising.



Work location on a tray.

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Temperature and its uniformity and control of carbon potential and uniformity of carbon absorption and diffusion.

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Difference in cooling speed, cooling agent and necessarily design of hardening and quenching units.

Main objective of the development work in heat treatment process aims to achieve a predictable and controlled distortion and dimensional changes. With established heat treatment changes, it is possible to provide allowances at soft finishing stages to achieve the final dimensional tolerances for transmission gears. Over pin size of transmission gears after shaving is kept less to take care of growth. Helix angle during shaving is kept less to achieve helix desired after heat treatment.

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Study of processes involved in manufacturing of high speed gear TM3G3489

13.7 Profile Grinding Grinding in one form or another has been used for more than 50 years to correct distortions in gears caused by the high temperatures and quenching technique associated with hardening. Grinding improves the lead, involute and spacing characteristics. This makes the gear capable of carrying the high loads and running at the high pitch line velocities required by today's most demanding applications. Gears that must meet or exceed the accuracy requirements specified by AGMA Quality 10-11 or DIN Class 6-7 must be ground or hard finished after heat treatment. Different Gear Grinding techniques are as follows: Gear grinding with the continuous generative grinding technique using grinding worms from Wendt and Winterthur In this technique, the tool corresponds to a grinding worm, the basic tooth profile of which should always be seen as a rack profile. The involute form is generated through continuous generative grinding of the grinding worm and the gearing. The process lends itself very well to the series production of gear wheels; here, conventional or electroplate-bonded CBN grinding wheels are used. The advantages of this technique are: 

High concentricity accuracy and pitch accuracy



Constant involute form and flank line around the full circumference of the gearing



Short machining cycles Gear

grinding

with

globoidal

grinding

worms

(continuous

profile

grinding)

unlike the continuous generative grinding technique, the grinding tool in this case does not correspond to a grinding worm with a rack profile as the basic tooth profile. Instead, a globoidal grinding worm maps the contour of the tooth flank. During the grinding process the tooth form is produced through virtually linear engagement of the tool in the tooth gap. This method is predestined for grinding bevel gears which are used primarily in differential gears. A distinction needs to be made between bevel gears without an offset (spiral bevel gears) and bevel gears with an offset (hypoidal bevel gears).

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Study of processes involved in manufacturing of high speed gear TM3G3489

Fig 12 Single flank generating grinding The involute shape is produced in a generative grinding process in which the grinding wheel only machines a single flank in the direction of grinding per tooth gap. This method allows the machining of different moduli with an unchanged wheel width and allows different infeed for the left or right-hand tooth flank. In recent years, this technique has been increasingly displaced by CNC-controlled form or profile grinding. From profile grinding with radial infeed With the aid of CNC dressing, the involute form is transferred to the grinding wheel, which then generates the form in the tooth gap of the workpiece. However, the process of the vertical infeed into the tooth gap has the disadvantage that very large contact areas are generated which extend beyond two tooth flanks and that, as a result, the risk of grinding abuse is significantly increased. Form or profile grinding with rotative infeed : In the same way as described above, here again CNC dressing is used to transfer the involute form to the grinding wheel, which then generates the form in the tooth gap of the workpiece in accordance with its programming. This method has the advantage that the grinding allowance is distributed more evenly between the head and base of the tooth, and that only one flank is machined per pass, which allows the contact area to be reduced.

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Study of processes involved in manufacturing of high speed gear TM3G3489 Winterthur gear grinding expertise The key variable for increased efficiency in the grinding process, the related rate of material removal MRR, normally follows the following simple relationship during creep-feed grinding or surface grinding: MRR = radial depth of cut ae x feed rate vw/60. For gear grinding this obviously does not apply strictly as above. As the involute describes a curve, the equation cannot reflect the effective values at the individual points of contact of the involute. The effective infeed qn must therefore change over the complete involute length and only corresponds to the infeed ae at the base of the tooth (refer to the illustration, "Graf" p. 84). Consequently, we have developed a program which looks at five data points over the involute and thus guarantees perfect grinding results (refer to the illustration, "Graf" p. 85). 

Tooth size



Angle of pressure



Angle of inclination



Radial infeed



Feed value Increasing importance of CBN for gear grinding: As the second-hardest material after diamonds, this material has now largely established itself as the standard grinding material in the automotive industry for components like crankshafts and camshafts. The situation is different in the gear wheel industry, where, due to the high costs of CBN grinding tools, the preferred approach is still to grind gear wheels made of tempered and/or hardened carbon steels predominantly with fused aluminium oxide. This makes good sense, but only in applications with low production volumes and/or applications involving the machining of steels which are not tempered or are not high-tempered. For example, pump wheels for the textile industry which are made of high-alloyed tool steels simply can no longer be manufactured costeffectively using conventional grinding materials. The solution:

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Study of processes involved in manufacturing of high speed gear TM3G3489 Electroplate-bonded

CBN

grinding

worms

and

wheels

from

Wendt

Used for example for combined CBN generative grinding and profile grinding systems for gear wheels or for tooth flank grinding on gearbox gear wheels. The advantages include: 

Single-layer grinding covering with high-strength bond



High dimensional accuracy and profile accuracy possible



Extremely high grinding performance



Good bite thanks to large grain protrusion



Cores can be recoated repeatedly 13.8 QUALITY MEASUREMENTS IN GEAR MANUFACTURING During gear cutting and finishing, some errors of the gear teeth are closely monitored to achieve the desired quality standard of the finished gears. 1. Tooth thickness error: It is the difference of tooth thickness between all the teeth at pitch circle diameter. 2. a) Individual pitch error: It is the difference between the actual pitch on its pitch circle to an adjacent tooth and the correct value. b) Adjacent Pitch error: It is the difference between the two adjacent pitch as on the pitch circle. c) Accumulated pitch error:It is the difference between the sum of actual pitches between any two teeth on the pitch circle and the correct value. 3. Total profile error:It is the sum of errors both in positive and in negative sides within the region of tooth profile measurement measured vertically to a correct involute as a basis, which passes through the intersection of an actual tooth profile and the pitch circle. 4. Total tooth lead error:It is the difference between a theoretical curve of tooth trace and that of an actual tooth trace corresponding to the necessary region of tooth profile measurement on the pitch cylinder. 5. Runout: It is the maximum variation of positions in radial direction of a contacting piece, e.g. a ball or pin, which has been made to contact with both tooth surfaces of the space close to the pitch circle.

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Study of processes involved in manufacturing of high speed gear TM3G3489 6. Backlash: It is the play on the reference pitch circle of a pair of gears engaging with each other. The magnitude of backlash for the different gear accuracy grade is established by standards. 7. Transmission error –Transmission error of a gear pair is the 'deviation of the position of the driven gear, for a given angular position of the driving gear, from the position that the driven gear would occupy if the gears were geometrically perfect Each gear error causes certain performance deficiency of gear pair in mesh.  Tooth thickness error - It causes excess or reduced backlash between the mating gears. Reduced backlash causes binding. Excess backlash may cause noise (on reversal) and if excessive, loss of tooth strength.  Accumulated pitch error and runout result in gear noise and non-uniform motion transmission.  Profile error causes disruption in uniform conjugate tooth action and uneven loading. It results in non-uniform motion transmission due to momentary disturbances of the rotational velocity, and also causes noise.  Lead error causes inadequate face width contact between the mating gears. It creates again uneven loading, localised bearings and wear. It results in non-uniform motion transmission and noise.  Transmission error causes noise and vibration.

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Study of processes involved in manufacturing of high speed gear TM3G3489

Fig 13 Online measurement Many standards, e.g. AGMA, DIN, JIS, BSI, cover gear error tolerances. Quality assurance of gears requires various types of measuring equipment during the manufacturing processes: 13.9 Elemental Checking: Tooth thickness: Different instruments, such as tooth caliper, addendum comparator, measure the tooth thickness depending on the tolerance limits. Vernier gear caliper, Fig. 4.84, measures the chordal thickness at the nominal pitch circle. Addendum Measurement: Addendum comparator, Fig 4.84, measures tooth thickness by comparing the gear addendum with that of a basic rack. The comparator jaws have the same angle of the tooth form of the gear to be checked. The comparator jaws are set to proper width with the help of a master corresponding to a rack tooth of proper module. The indicator reads zero on this master. Variation in the indicator reading (+or) implies the difference in the thickness of the gear being measured with theoretical value. Corrections for taper and dimensional deviations of outside diameter of the gear blank are made as the outside diameter is used as reference point.

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Study of processes involved in manufacturing of high speed gear TM3G3489 Span Measurement: A tooth Vernier caliper or plate micrometer measures the distance over two or more teeth along a line tangent to the base cylinder, Fig. 4.85. The measurement directly relates to the thickness of a single tooth (or the backlash contributed by the gear to the pair). Span measurement process suits for spur and helical gears of even or odd number of teeth. It is possible to measure the gears while on gear cutting machine (often while the machine is running). The differences in measurements around the gear are readily noticeable indicating the need of repair of the machine. A small 25 mm range micrometer can handle gears of quite large pitch circle diameter. Dial calipers with at least one plane anvil are suitable for helical gear measurement, while a cylinder-and-sphere anvil dial caliper is acceptable for spur gears only. For a narrow face width gear with high helix angle, the process is not recommended as the spanning of a sufficient number of teeth becomes difficult. For modified profile, the measurements will be erroneous. Runout or size variation of outside diameter does not affect the measurement. However, base pitch errors influence the readings. Measurement over pins (balls): The over pin (or ball) size of the pitch circle diameter of a gear controls the centre distance and backlash of the gear pair. Measurement is easily done for a spur gear with help of a micrometer. The over pin size for helical gears having an even number of teeth is measured by keeping two pins of specified size diametrically opposite in the tooth space, Fig. 4.86. For helical gears having odd number of teeth, the measurement is somewhat difficult. Little improvement may be there in measuring over two properly placed balls. The diameter of the measuring pins (balls) is such that it makes contact with the tooth flanks in the vicinity of pitch circle where the involute error is minimum. Variation or runout of outside diameter does not influence on the accuracy but errors in spacing and profile does affect the measurement. The method is almost universally used to check and control the size of gears at all stages of gear processing - cutting, soft finishing, hardening as well as hard finishing. Profile: Measurement of an involute profile is based on its geometric property (A line normal to an involute curve is a tangent to the base circle). An involute is thus the co-ordinates of heights to a tooth and angles from the base circle, Fig. 4.87. A base circle disc and straight edge are used to measure the involute profile. Gear is mounted with a base circle disc coaxially. A small pressure applied between the straight edge and the disc moves them simultaneously.

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Study of processes involved in manufacturing of high speed gear TM3G3489 Pitch variation: Pitch variations are measured in two ways: 

Precision indexing: The gear is indexed accurately (mechanically, electronically or optically). A single probe measures the actual position of each tooth relative to the theoretically correct position of each tooth. Adjacent and accumulated pitch error is directly measured



Tooth space comparison: A two probe system records the distance from a point on tooth number 1 to the corresponding point on the tooth number 2. The two probes continue checking all around the gear one after another. The system only compares the tooth gaps. Each measurement is taken from a different datum. For direct contact type measuring probes, surface finish of tooth flanks affects the result. A proximity measuring probe averages the flank irregularity.

Runout: A ball or roller of specified size placed in each tooth gap, Fig. 4.89 measures the radial runout on the pitch circle diameter.. Presently, a single machine checks almost all the parameters in same setup. The machines are conventional mechanical type or fully computerised numerically controlled type with different level of automation.

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Study of processes involved in manufacturing of high speed gear TM3G3489 13.10 CNC Gear Measuring Centre: CNC gear measuring centre checks all the important gear tooth errors and modifications automatically with better accuracy and in very short time. It does not need any base circle disc. The stylus moves in a tooth space, and the automatic measuring starts. Generally, right and left flanks of 4 teeth at 90 degree apart are measured. A single probe performs all the measurements with movements produced by individual table and slide on several axes, Fig. 4.91 through a CNC continuous path control system. The CNC control determines the required relative feed rate for the measuring links and the speed for the rotary workpiece drive to suit the individual tests based on the gear data input. The control system calculates the theoretical base circle radius. The deviations from the nominal involute form and the nominal helix are registered and transmitted to the computer. For pitch measurement, the rotary and linear measuring systems register and transmit to the computer the exact angular position of each tooth flank. The electronically controlled tracer stylus advances into and withdraws from the tooth gaps on completion of the measured data pickup, while the workpiece rotates continuously. The desired information about the errors appears as traces and digital form on screen and may be plotted and printed automatically. Automation to any desired extent is possible.

Fig 14 CNC Gear Measuring Centre

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Study of processes involved in manufacturing of high speed gear TM3G3489 14 Assembly and Testing Casing Deburring, casing bore, bedding with mandrel

Cleaning and flushing process

QA verification

Improve tooth face contact, Thermocouple and RTDs

Water jet cleaning and flushing

1 tonne and 10 tonne dynamic balancing machine

Dynamic balancing of gear set with shop coupling hubs/simulated shaft coupling hubs

QA verification

1600kW , 600Kw, 200kW testing

Gear assembly and parameter checking and adjustment

Prepare gear box on test bench carrying out oil flushing, MRT inspection and other processes

QA verification

Final assembly of gear box fixing accessories, RTDs and nameplates

Release to dispatch

Fig 15 Assembly and Testing

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Study of processes involved in manufacturing of high speed gear TM3G3489

14.1. Dynamic Balancing 1. Causes: The International Standards Organization defines unbalance as: “That condition which exists in a rotor when vibratory force or motion is imparted to its bearings as a result of centrifugal forces”. The more popular definition is: “The uneven distribution of mass about a rotor’s rotating centreline”. The key phrase being “rotating centreline” as opposed to “geometric centreline”. The rotating centreline being defined as the axis about which the rotor would rotate if not constrained by its bearings. (Also called the Principle Inertia Axis or PIA). The geometric centreline being the physical centreline of the rotor. When the two centrelines are coincident, then the rotor will be in a state of balance. When they are apart, the rotor will be unbalanced. Different types of unbalance can be defined by the relationship between the two centerlines. These include: Static Unbalance – where the PIA is displaced parallel to the geometric centerline. Couple Unbalance – where the PIA intersects the geometric centerline at the center of gravity. (CG) Dynamic Unbalance – where the PIA and the geometric centerline do not coincide or touch.

2. Corrections: When unbalance has been identified and quantified, the correction is straightforward. Weight has to be either added or removed from the rotating element. The ultimate aim being to reduce the uneven mass distribution so that the centrifugal forces and hence the vibrations induced in the supporting structures are at an acceptable level.

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Study of processes involved in manufacturing of high speed gear TM3G3489 Field Balancing: Many rotors can often be balanced in place, running at their own operating speed, with minimum disassembly. To balance in place, of course, a basic requirement is that the rotor has to be accessible to make corrections. Machines such as fans and blowers are good candidates. Totally enclosed motor armatures and pump impellers are not. The technique of balancing in place is referred to as Field Balancing and it offers some distinct advantages including: 

Balancing is performed on the complete assembled machine and compensates for the assembly tolerances discussed earlier.



Costly and time-consuming disassembly to remove the rotor to a balancing machine is eliminated.



The effects of temperature, pressure, distortion and other environmental influences can be incorporated.



The resultant vibration can be the tolerance applied to the rotor, rather than the published balance tolerances normally used in a balancing machine. This is particularly advantageous if the supporting structure is close to a resonance. The unbalance in the rotor may have to be adjusted to abnormally fine levels to minimize the resultant resonant structural vibration. Modern instruments such as vibration analyzers, data collectors and portable

balancers provide accurate information to assist in the balancing process. The vibration level measured at the rotating speed frequency is used as an indicator of the amount of unbalance. The location is determined by measuring the phase. Phase, (the relative motion of one part of a machine to another) is measured by means of a stroboscopic light or by an indicator in the instrument, triggered by a photocell. It is imperative that the vibration measured is a result of the unbalance and not some other exiting force. Only a detailed, thorough, analysis can identify where the vibration measured is coming from. Many sources of vibration can occur at the rotating speed frequency.

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Study of processes involved in manufacturing of high speed gear TM3G3489 When field balancing, trial weights for balance computation and permanent weights for final correction are normally added to the rotor. Care should be taken when attaching weights. They should be attached securely so that they cannot ‘fly off’ when the machine is operating. They not only constitute a personnel safety hazard but also can cause damage. Loose balance weights rattling around inside a turbine for example can wreck the machine. Factory Balancing: As part of the manufacturing process, most rotors are routinely balanced in a balancing machine.

Fig 16: Balancing machine

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Study of processes involved in manufacturing of high speed gear TM3G3489

15. Conclusion The past days of the internship have been a very instructive experience. During our time at ‘Triveni engineering and industries private limited’, we were offered a myriad of opportunities to understand the functioning of the whole process unit. After having a look at the various processes, we really obtained a connection with the theoretical and practical aspects involved. The various intricacies with which the various production departments of the company coordinate came alive to us. For instance, the heat treatment plant gave us a thorough understanding of the heat treatment process and the time temperature transformation diagrams. Another unique opportunity which we had was to gain insight into the working of high end CNC machines. On the whole it was an eye opening experience in terms of the sheer exposure to the industrial processes we had.

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