CHAPTER 1 INTRODUCTION
1.1. Company Profile
Austin Engineering Company Pvt. Ltd. believe in two things: the power of innovation and the sheer force of focus. Ever since our inception in 1973, company had continuously upgraded their skills, production capacities, infrastructure and services. From an outfit of 10workers, that manufactured cylindrical roller bearings and deep groove ball bearings with an outside diameter of up to 50 mm, today company is a global force in the bearings industry. Currently company manufacture almost the entire range of anti-friction bearings up to an outside diameter of 1000 mm.
The bearings that company supplies to various segment of market:
‘ Manufacturing of engineering equipment
‘ Steel rolling mills and Steel Rolling plants
‘ Process Industries
‘ Industries of automotive
‘ Manufacture of textile machinery
‘ Power Plants
‘ Road Transport
‘ Railways
‘ Atomic Energy applications
‘ Replacement Market
1.1.1 Types of Bearing
AEC manufactures over 4500 size/types of ball and roller bearings used in number of industrial segments and are constantly adding more items to the current wide range to cater to all customers’ rolling element bearing needs. The engineering is backed by a strong R&D, quality assurance, testing and gauging team and the customers have seen the value of this investment in every single bearing AEC manufactures.
‘ Ball Bearings
‘ Deep groove ball bearing
‘ Angular contact ball bearing
‘ Self – aligning ball bearing
‘ Thrust ball bearing
‘ Roller Bearings
‘ Cylindrical roller bearing
‘ Needle roller bearing
‘ Tapered roller bearing
‘ Spherical roller bearing
‘ Super Precision Bearings
‘ Angular contact ball bearing
‘ Cylindrical roller bearing
‘ Axial-Radial bearing
‘ Plain Bearing
1. Deep groove ball bearing
The deep-groove ball bearing is the most common type, since it can be used for relatively high radial loads.
Deep-groove radial ball bearings are the most widely used bearings in industry, and their market share is about 80% of Industrial rolling-element bearings.
The radial and axial load capacity increases with the bearing size and number of balls.
2. Spherical roller bearing
Spherical roller bearings are self-aligning bearings. The self-aligning feature is achieved by grinding one of the races in the form of sphere.
These bearings can normally tolerate angular misalignment in order of ” 1” and when used with a double row of roller, these can carry thrust loads in either direction.
3. Needle roller bearing
Needle roller bearings are relatively slender and completely fill the space so that neither a cage nor a retainer is needed.
These bearings are used when heavy loads are to be carried with an oscillatory motion.
4. Tapered roller bearing
The rollers and race ways of these bearings are truncated cones whose elements intersect at a common point. Such type of bearings can carry both radial and thrust loads.
These bearings are available in various combinations as double row bearings and with different cone angles for use with different relative magnitudes of radial and thrust loads.
5. Self-aligning ball bearing
Self-aligning bearings permit shaft deflection within 2-3 degrees. It may be noted that normal clearance in ball bearings are too small to accommodate any appreciable misalignment of the shaft relative to the housing.
If the unit is assembled with shaft misalignment present, then the bearing will be subjected to a load that may be in excess of design value and premature failure may occur.
1.1.2 Process Flow Chart
1.2 Project Profile
1.2.1 Cylindrical Roller Bearing
The roller bearings use the cylindrical roller, taper roller or spherical roller as the rolling elements. The contact between the inner race and the roller or the outer race and the roller is a line contact. Because of the nature of contact, the roller bearings have a higher load carrying capacity as compared to ball bearing.
Cylindrical roller bearings have greater radial load carrying capacity than the ball bearings of the same size because of the greater contact area. In addition, they have high rigidity. However, they cannot take thrust load.
Cylindrical roller bearings have short roller guided in a cage. These bearings are relatively rigid against radial motion and have the lowest coefficient of friction of any form of heavy duty rolling-contact bearings. Such types of bearings are used in high speed service.
Cylindrical Roller Bearing
1.2.2 Nomenclature of Cylindrical Roller Bearing
1.2.3 Cylindrical Roller Bearing Series
‘ Single Row Series
Metric – N, NF, NH, NJ, NU, NUJ, NUP, NUPJ
Inch – CFL, CFM, CRL, CRM, LLRJ, MMRJ, XLRJ
‘ Double Row Series
Metric – NN, NNU, NCF
‘ Without IR Series
Metric – RNU 200, 300, 400, 1000, 2200, 2300
‘ Full Complement Series
Metric – NJG
1.3 Definition
Cylindrical roller bearing occurs excellent resistance to instantaneous load, over load and shocks. Manufacturing of this bearing some malfunction occurs this malfunction rejection of product unit. This rejection of finished product result into wastage of company’s man, material and machine.
The cylindrical roller bearing is used in applications where high radial load is present without any thrust load. In certain applications where diameter space is limited, these bearings are mounted directly on the shaft, which serves as the inner race.
They simplify assembly thanks to their detachable element and allow, for certain types, axial displacement or low axial load, for other types.
1.4 Purpose
‘ Long service life
‘ Low friction
‘ High positioning accuracy
‘ Increased the machine uptime
‘ Noise free operation
‘ Reduction in vibration
‘ Reduce frictional corrosion
‘ Detect defect occurring in manufacturing of bearing
‘ Determine amount of scrap rejection due to defect
1.5 Objective
The Objective of this Project are determine. There are following objective have been focused on and simplify the project started below :
‘ To reduce the friction between two contacting surface
‘ To protect the surface against corrosion
‘ To carry away the worn-out particles
‘ Reduce defected finished product in batch quantity
‘ Improvise machining process
‘ A slightly rough surface having uniform and constantly maintained value of roughness
‘ Smooth surface free from scratches and sharp corners and edges give safety to users
1.6 Scope
‘ The productivity of bearing will increase.
‘ Maintenance and down the time cost will minimize.
‘ Bearing life will increase.
‘ Failure of bearing will decrease.
‘ Innovative design
‘ The modification in bearing manufacturing process used for the latest technology and automation.
1.7 Project History
Contact-type bearings have mechanical contact between elements, and they include sliding, rolling, and flexural bearings. Mechanical contact means that stiffness normal to the direction of motion can be very high, but wear or fatigue can limit their life. Non-contact bearings include externally pressurized and hydrodynamic fluid-film (liquid, air, mixed phase) and magnetic bearings. The lack of mechanical contact means that static friction can be eliminated, although viscous drag occurs when fluids are present; however, life can be virtually infinite if the external power units required to operate them do not fail. Each type of bearing has its own niche application area, and thus design engineers must be familiar with different types of bearings, and their applications and limitations.
The principle of reciprocity is particularly useful in the design of bearing systems: Whenever you think you have a good design, invert it, think of using a completely different type of bearing or mounting, and compare it to what you originally considered. Rolling element bearings generally consist of two rings, an inner and an outer, between which a set of balls or rollers rotate in raceways. Under normal operating conditions of balanced load and good alignment, fatigue failure begins with small fissures, located between the surface of the raceway and the rolling elements, which gradually propagate to the surface generating detectable vibrations and increasing noise levels (Eschmann et al 1958). Continued stress causes fragments of the material to break loose, producing a localized fatigue phenomenon known as flaking or spalling (Riddle 1955). Once started, the affected area expands rapidly contaminating the lubricant and causing localized overloading over the entire circumference of the raceway (Eschmann et al 1958).
Eventually, the failure results in rough running of the bearing. While this is the normal mode of failure in rolling element bearings, there are many other conditions which reduce the time to bearing failure. These external sources include contamination, corrosion, improper lubrication, improper installation or brinelling.
CHAPTER 2 – LITERATURE SURVEY
2.1 Defects in Cylindrical Roller Bearing
1. Ovality
Ovality means non-circularity. In measurement instruments, ovality is the amount of out of roundness of a cylindrical part in the typical form of an oval. Ovality is defined as the difference in diameters measured in one plane perpendicular to each other.
2. Hardness due to over heating
Hardness is a function of material a brittle structure. Austenite and pearlite is a partly hard and partly soft structure when slowly quench process`. When the cooling rate is at room temperature the face centered of cubic structure found in austenitic region.
Internal tension of bearing increased risk of deformation during heat treatment of bearing ring. In order to eliminate internal tension, hardening is followed by tempering. The tension will removed by tempering.
Hardness due to overheating which is depends on rate of heat generation, rate of heat dissipation, heat balance.
3. Cracks due to rough
Cracks may form in bearing ring, inner race, outer race, rolling elements or cage may be fail in various reasons. The rolling elements either permanently deform or get crushed due to over load or misalignment.
The same result may be obtained when bearings are heated and then mounted on shaft manufactured to the wrong tolerance.
Cracks of the bearing parts can be avoided by maintaining the load on bearing within the limit and Operating the bearing within permissible speed limits.
4. Faulty Cages
Most of cages are made of die casting. So generally defect occurring in casting are likely to occur in cage. These casting defects are as follows: inclusion, segregation, porosity.
If, on examination of a failed bearing, the cage is found to be damaged, it may in many cases prove difficult to ascertain the cause. Usually other components of the bearing are damaged too and this makes it even more difficult to discover the reason for the trouble.
5. Misalignment
Misalignment can be detected on the raceway of the non- rotating ring by a ball wear path that is not parallel to the raceway edges. If misalignment exceeds 0.001inch/in. you can expect an abnormal temperature rise in the bearing and/or housing and heavy wear in the cage ball-pockets.
The most prevalent causes of the misalignment are: bent shaft, burrs or dirt on shaft or housing shoulder, shaft threads that are not square with shaft seats and locking nuts with faces that are not squared to the thread axis. The maximum allowable misalignment varies greatly with different application, decreasing, for example with speed.
2.2 Life of Bearing
The life of an individual ball or roller bearing may be defined as the number of revolutions which the bearing runs before the first evidence of fatigue develops in the material of the rolling elements.
The rating life of a group of apparently identical roller or ball bearings is defined as the number of revolutions that 90 percent of group bearings will complete or exceed before the first evidence of fatigue develops.
The term minimum life is also used to denote the rating life. It has been found that the life which 50 percent of a group of bearings will complete or exceed is approximately 5 times the life which 90 percent of bearings will complete or exceed.
2.3 External Indication of Failure
A bearing rotating under functional conditions will exhibit certain “normal” operating levels of temperature, noise and vibrations. Exact levels will vary, as they are dependent on several factors: load, speed, lubrication, type of bearing. These levels should be considered as signals or warnings when they exceed those established for the “normal” or steady state conditions.
Deviations from the “norms” established under your operating conditions should signal the need for implementation of your preventive maintenance program or at least a close check to determine the cause of the deviation.
(1) Vibrations:
These can be detected by hand or with electronic equipment (frequency or amplitude analyzer). This type of equipment can be used to alert the operator or to stop the machine.
(2) Noises:
Some abnormal noises can be heard immediately, frequently the bearing damage will have to be identified from an external indication. The amount of fatigue in a bearing might be difficult to evaluate from external indications. Generally the bearing is close to the end of its useful life when the external indications are detectable. such as those due to rolling element indentations because of improper mounting; others are progressive.
Noise is usually an indication of incipient failure and varies in intensity and frequency with the extent of the damage. Conversely the damage due to unbalanced loads is generally inaudible since their frequency is identical to the rotating assembly frequency.
(3) Temperature rise:
Any operating bearing is subjected to a temperature rise above the ambient. This rise depends on many factors and reaches a certain level considered as normal, for a particular mounting. Any rise beyond that normal level is an indication of failure.
(4) Increase of the friction torque:
Any rotation system (shaft, wheel, pulley…) presents a resistant torque, even when mounted on bearings. Any torque increase is indicative of an alteration in the bearing. Generally, an increase of the friction torque generates a temperature rise.
CHAPTER 3 – IMPLEMENTATION OF THE PROJECT WORK
3.1 Working principle of cylindrical roller bearing
In most applications, there are mostly one or two roller bearings supporting a rotating shaft. The inner rings are fitted pressure on the shaft and the outer rings may not be fitted press.
There are unlike balls riding in ball bearings, rollers rolling on a flat surface and free to move axially on way path. The capability of rollers to move axially on way paths eliminates unwanted thrust from due to differential thermal expansion between shaft and housing.
Roller bearings don’t have outer rings mounted in housing as ball bearing. Roller bearings support heavier loads than ball bearings of the same size because of having line contact between the rollers and rings as to point contact for ball bearings. Line has more supporting area of the load and less stress than the ball bearings point contact, this features makes roller bearings a stiffer support to shaft.
Cylindrical Roller Bearing Terminology
3.2 Different types of cylindrical roller bearing damages
3.2.1 Wear caused by abrasive particles
If there is not sufficient lubricant, or if the lubricant has lost its lubricating properties, it is not possible for an oil film with sufficient carrying capacity to form. Metal to metal contact occurs between rolling elements and raceways. In its initial phase, the resultant wear has roughly the same effect a slapping. The peaks of the microscopic asperities that remain after the production processes are torn off and, at the same time, a certain rolling-out effect are obtained. This gives the surfaces concerned a varying degree of mirror-like finish. The temperature may even become as high as to cause the bearing to seize.
‘ Appearance
‘ Worn, frequently mirror-like, surfaces; at a later stage blue to brown discoloration.
‘ Cause
‘ Lubricant has gradually been used up or has lost its lubricating properties.
‘ Action
‘ Check that the lubricant reaches the bearing. More frequent re lubrication.
Cylindrical roller with mirror-like surface on account of lubricant starvation
3.2.2 Wear caused by vibration
When a bearing is not running, there is no lubricant film between the rolling elements and the raceways. The absence of lubricant film gives metal to metal contact and the vibrations produce small relative movements of rolling elements and rings. As a result of these movements, small particles break away from the surfaces and this leads to the formation of depressions in the raceways.
Cylindrical roller bearings are the most susceptible. The fluting resulting from vibrations sometimes closely resembles the fluting produced by the passage of electric current. However, in the latter case the bottom of the depression is dark in colour, not bright or corroded. The damage caused by electric current is also distinguishable by the fact that the rolling elements are marked as well as the raceways.
‘ Appearance
‘ Depressions in the raceways. These depressions are rectangular in roller bearings and circular in ball bearings. The bottom of these depressions may be bright or dull and oxidized
‘ Cause
‘ The bearing has been exposed to vibration while stationary.
‘ Action
‘ Secure the bearing during transport by radial preloading. Provide a vibration-damping base. Where possible, use ball bearings instead of roller bearings. Employ oil bath lubrication, where possible.
Vibration damage to the ring of cylinder roller bearing
3.2.3 Seizure
Although scuffing and smearing can be categorized as seizure, scuffing is generally regarded as a more serious type of failure. The seizure described in this section is the kind in which bearing parts are melted and adhere to one another due to abnormal heat or the rolling surface becoming rough; as a result, the bearing can no longer rotate.
Once seizure occurs, the bearing cannot be used again because the hardness has deteriorated and smooth rotation is impossible on the rough surface.Seizure is damage caused by excessive heating in bearings.
Seizure of cylindrical roller bearing
Seizure of cylindrical roller bearing with rib
‘ Failure
‘ Discoloration, distortion and melting together of bearing components.
‘ Causes
‘ Too small internal clearance.
‘ Improper or insufficient lubricant.
‘ Excessive load
‘ Remedies
‘ Provide proper internal clearance.
‘ Select proper lubricating method or lubricant.
3.3 Implementation of the work
1. Implementation for Ovality
‘ Implementation dial indicator for mounting on spindle
‘ Use of special fixture for race manufacturing
‘ Deploy skilled and experienced grounding staff as per requirement
‘ Active supervising staff
2. Implementation for Micro-cracks
‘ Grinding process should be automated or better skilled operator should be assigned
‘ process Using magnetic clamping
‘ Scheduling grinding wheel dressing by experienced & qualified staff
‘ Consulting well-experienced engineer & dealer for abrasive
‘ Highly calibrated and digital coolant feed mechanism
CHAPTER 4 FUTURE SCOPE
The following future scope of project written below:
‘ The productivity of bearing will increase.
‘ Maintenance and down the time cost will minimize.
‘ Bearing life will increase.
‘ Failure of bearing will decrease.
‘ Innovative design
‘ The modification in bearing manufacturing process used for the latest technology and automation.
essay-2016-10-07-000BdK