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Friday, 27 December 2013

Angular Contact Ball Bearings.

PumpPac angular contact ball bearings reduce operating temperatures and vibration levels for smoother operation and longer life.

Available in three series, the bearings incorporate combinations of 40 and 15° bearing-contact angles capable of carrying high thrust loads with the 40° bearing (without unloading the opposed 15° bearing).

Wearresistant machined bronze cages work in poor lubrication conditions. "CB" endplay better controls and lowers operating temperature. ABEC 3 tolerances promote less impeller shaft runout, smoother operation, and longer seal life; and a V-etched OD simplifies installation by clearly indicating the direction of thrust capability.

ARB Bearings Limited
H-22, Udyog Nagar
New Delhi - 110041, Delhi, India
Phone: +(91)-(11)-25471274 / 25471255 / 25186300
Fax: +(91)-(11)-25475455 / 25470126
Email: info@arb-bearings.comexport@arb-bearings.com,
sales@arb-bearings.com 
Website :http://arb-bearings.com/content.php?id=2
For Export Enquiry :
Mr. Divay Rathee : +91-9968373086




MACHINE DESIGN partners with PARTsolutions to launch new 2D/3D CAD Library

Penton Media's Design Engineering group, anchored by Machine Design magazine, announced today that it has entered into a strategic partnership with PARTsolutions®, LLC, a leading provider of publishing solutions for 2D/3D digital parts catalogs, to launch the Machine Design CAD Library, a powerful, new resource for design engineers.

CLEVELAND, OH - October 25, 2006 - Penton Media's Design Engineering group, anchored by Machine Design magazine, announced today that it has entered into a strategic partnership with PARTsolutions®, LLC, a leading provider of publishing solutions for 2D/3D digital parts catalogs, to launch the Machine Design CAD Library, a powerful, new resource for design engineers.



Located at www.machinedesign.com/cadlibrary and free to design engineers, the Machine Design CAD Library includes millions of configurable 2D and 3D CAD models of components and assemblies downloadable for easy use in new and existing designs. Unlike other digital parts catalogs, the Machine Design CAD Library models are in native CAD formats with no translation required resulting in the highest possible accuracy and data quality. PARTsolutions' relationships with the major CAD companies make it the only company with solutions that serve the entire market independent of the technology choice of suppliers and OEMs.

"Machine Design's new CAD Library provides an exciting, next-generation resource for designers and engineers taking advantage of the depth and immediacy of the Web to find solutions for their product development initiatives," said Machine Design Publisher John Petersen. "PARTsolutions is the perfect partner to help us continue bringing cutting-edge resources to complement our portfolio of industry-leading information products and services for the global design engineering community."

PARTsolutions CEO, Tim Thomas, added, "The opportunity to be partnered with Penton Media and a best-in-class team with the strongest industry readership is extraordinary. Part catalogs delivered in native formats have long been demanded by industry users and are now accessible in the Machine Design CAD Library. Component suppliers and their customers will all benefit."

ARB Bearings Limited
H-22, Udyog Nagar
New Delhi - 110041, Delhi, India
Phone: +(91)-(11)-25471274 / 25471255 / 25186300
Fax: +(91)-(11)-25475455 / 25470126
Email: info@arb-bearings.comexport@arb-bearings.com,
sales@arb-bearings.com 
Website :http://arb-bearings.com/content.php?id=2
For Export Enquiry :
Mr. Divay Rathee : +91-9968373086

Industrial Bearings Manufacturers India

How do they get the balls in ball bearings so perfectly round and smooth?
If you have ever rolled a couple of those little metal balls found in a ball bearing around in your hand, you have noticed how perfectly round and incredibly smooth they feel. You might have wondered how anything could be made that perfect. It's actually a pretty neat process that starts with a metal wire and ends with a perfect shiny ball.




The first stage in the process is a cold or hot forming operation. A wire of metal approximately the diameter of the finished ball is fed through a heading machine. This machine has a metal cavity the shape of a hemisphere on each side. It slams shut on the wire forcing the piece of metal into the shape of a ball. The process leaves a ring of metal (called flash) around the ball, so the balls coming out of this machine look something like the planet Saturn.

Next the balls go into a machine that removes the flash. This machine rolls the ball between two very heavy hardened steel plates called rill plates.

Rill plates for ball machine



Photo courtesy of Noonan Machine Co.

One rill plate is stationary and the other one spins. The plates have grooves machined into them that guide the balls around in a circular path. You can see that one of the plates has a section cut out of it; this is where the balls enter and exit the grooves. When the machine is running, the grooves are completely filled with balls. Once a ball has traveled through a groove, it falls into the open section in the plate and tumbles around for a little while before entering a different groove. By making sure the balls travel through many different grooves, all the balls will come out of the machine the same size even if there are differences between the grooves.

As the ball travels through the groove, it spins and tumbles, the rough edges get broken off, and the ball gets squeezed into a spherical shape, a little like rolling a ball of dough between your hands. This squeezing of the balls compresses the metal, giving the balls a very hard surface. Because the balls are metal, this operation generates a lot of heat, so water pours over the balls and plates to cool them.

The variables in this process are the pressure that squeezes the plates together, the speed the plates spin and the duration the balls are left in the machine. Properly setting these variables will consistently produce balls of the correct size.

After this operation the balls may be heat-treated. This hardens the balls, but it also changes their size. The size of bearing balls has to be perfect, sometimes within millionths of an inch, so a few more operations are needed after heat-treating.

The balls next go through a grinding operation. The same kind of machine is used, but this time the coolant contains an abrasive. The balls travel through the grooves again and get ground down and compressed to their final dimensions.

Finally the balls go through a lapping operation. Again, the same kind of machine is used, but this time the plates are made of a softer metal, and the machine uses much less pressure to squeeze the plates together. Also, the machine uses a polishing paste rather than an abrasive. This process gives the balls their perfect smooth shiny surface, without removing any more material.

The last step in the process is inspection. The balls are measured with very accurate machinery to determine if they meet the required tolerances. For instance, the Anti-Friction Bearing Manufacturers Association (AFBMA) has a set of grades for bearing balls. A grade three ball has to be spherical within 3 millionths of an inch and the diameter must be accurate within 30 millionths of an inch. This means that for a grade three quarter-inch ball, the diameter would have to be between 0.24997 and 0.25003 of an inch and the smallest diameter measured on the ball has to be within 3 millionths of the largest diameter.

Manufacturers use a very similar process to make metal pellets for air guns, plastic balls for bearings and even the plastic balls used in roll-on deodorant.

How Ball Bearings Are Made.

Three centuries ago, an astonishingly simple manufacturing method had been developed for balls made of stone, e. g. marble. Lumps of stone were hammered into squares with rounded edges and put on stone plates with concentric grooves; then a wooden plate was put on top and run as a water wheel, until, after one, two or three days, the squares had become balls.


The deviation in diameter of these balls from the ideal circular shape, the out-of-roundness, is less than 0.1 millimetre (Figure 34, left).
Who knows why steel balls were not machined, from the very beginning, to a principle similar to that of stone ball production. This production method guarantees for a large number of balls equal diameters when machined between two plates, since only the ball contacting the upper and lower rotating surface simultaneously with a certain load can be ground. Due to the numerous contact points, a set of balls of equal size is produced almost automatically.

For mass production of steel balls in the 19th century another method was chosen first. After all, not relatively soft stones, but steel had to be treated. On lathes, balls of a remarkable accuracy were cut off from a rod of steel and the ends machined to form a sphere. At the turn of the century, balls manufactured by this method in England were within tolerances of 0.025 to 0.050 millimetre [1]. The Schweinfurt mechanic Friedrich Fischer, son of Philipp Moritz Fischer who built the first pedal bicycle, did not want to accept this accuracy, mainly because the imported steel balls were too expensive. In his workshop for velocipedes, bicycles and tricycles he therefore worked intensively on the production of high-quality balls. The marble ball mills described above were probably not the model for Friedrich Fischer's ball milling machines. He developed, however, a similar production method.

ARB Bearings Limited
H-22, Udyog Nagar
New Delhi - 110041, Delhi, India
Phone: +(91)-(11)-25471274 / 25471255 / 25186300
Fax: +(91)-(11)-25475455 / 25470126
Email: info@arb-bearings.comexport@arb-bearings.com,
sales@arb-bearings.com For Export Enquiry :
Mr. Divay Rathee : +91-9968373086

Hybrid taperedroller-spindle bearings help machine tools cut without cutting fluids.

Anthony Romero
Senior Application
Engineer
Machine Tool
The Timken Co.
Torrington, Conn.

Spindle heating can be a problem for equipment that dry machines gear teeth. These large-bore hybrid tapered roller spindle bearings operate at temperatures between 90 and 100°F, significantly cooler than all-steel bearings. The hybrid bearings can also last significantly longer than all-steel equivalents under the same operating conditions.




The hybrid bearings come in precision Classes 00 and 000, providing a rotational accuracy below 1 m (TIR) and nonsynchronous runout of <0.5 m. The latter metric is key to accurate and repeatable cutting processes. Timken credits tighter bearing tolerances with the improved rotational accuracy.

Machine tools are one of the most challenging environments for bearings. This is particularly true for gear-cutting equipment. Such machines put significant loads on spindle bearings when they simultaneously cut multiple gear teeth at high metalremoval rates. Spindle bearings also need a wide speed range because bevel and hypoid gear cutters typically run between 200 to 4,500 rpm, depending on the operation and workpiece size.

There is also a push to eliminate cutting fluids in the interest of lowering maintenance and disposal costs. Such dry machining is typified by fast metal-removal rates, which necessitates an extremely rigid spindle able to handle both high rpm and horsepower. Machining without cutting fluids can set up large thermal gradients between the spindle and tooling, making it difficult to hold size on machined parts. Standard spindle-bearings under these conditions may reach temperatures above 150°F, exacerbating the problem.

But special hybrid ceramic tapered roller bearings meet all the above design criteria and, under the same conditions, run at temperatures between 90 to 100°F. The bearings incorporate ceramic (silicon-nitride) taperedrolling elements in a precision-class bearing. Ceramic has a modulus of elasticity 50% greater than steel, which boosts bearing rigidity. The material also has a lower coefficient of friction and an extremely fine surface finish that lessens frictional torque and helps the bearings run cooler.




With optimized races, ribs, rolling elements, and special highspeed synthetic grease, the hybrid design can outperform conventional bearings at higher machining speeds, while maintaining a high stiffness and load capacity at low rpm. A single bearing type generally doesn't work well in both operating regimes. Ball bearings, for example, tend to run cooler than other bearings at higher rpm (above 750,000 DN). Tapered rollers are a better choice when spindle stiffness and load-carrying capacity are key design considerations.

Compared with other bearings in spindle applications, such as angular-contact ball bearings (point contact) or cylindrical roller bearings (line contact), tapered-roller bearings have a significantly higher radial stiffness and are less susceptible to overload. Hybrid tapered-roller bearings also simplify spindle design. Spindles need just two of the bearings — one on each end. For comparison, spindles that use cylindrical double-row bearings need one at both ends and an axial angular contact bearing in the middle to achieve similar rigidity levels.

Tests show tapered-roller bearings (at zero clearance) have a radial stiffness 4 to 6 that of comparably sized angular-contact ball bearings, and twice as much as cylindricalroller bearings. Tapered-roller bearings use angled raceways to carry both radial and thrust loads. As a rule, a shallow taper is used for heavy radial loads, and a steep taper, for heavy thrust loads. The hybrid bearing is designed with an angularity or K factor specific to the gear-cutting application. It takes into account preload, external cutting loads, and operating speed.

Another tapered-roller bearing quality called true rolling motion further improves bearing performance. Standard-class bearings have crowned or other profiles on raceways and rollers to minimize contact stress at the roller ends under heavy loads. Loads on machine tools, in contrast, are better characterized so the spindle bearings instead use a straight race profile. Such precision-class bearings exhibit true rolling motion of rollers on raceways. True rolling motion helps bearings run cooler and boosts spindle stiffness and accuracy. This motion is the result of two design features: roller taper; and the contact between the race rib and the spherical surface ground on the large end of the rollers.

Rollers are designed such that extensions of the lines along the roller bodies converge toward the centerline of the bearing and meet at an apex on this centerline. The result: no relative slip between the rollers and races. The arrangement also generates a force that seats the roller spherical end against the race rib. This seating force is a function of the different angles of the outer and inner races and is desirable because it helps keep rollers from skewing off apex. A lack of skew ensures positive roller alignment. This, in turn, boosts stiffness and accuracy, and extends bearing life.

Analytical models optimize the apex angle so bearings accommodate radial and axial loads generated during the gear-cutting process. This helps maintain proper roller alignment at low rpm and controls skidding. Modifications to the rib/roller interface further help maintain control at low rpm.

Bearing stiffness also depends on the bearing load zone, which is directly related to bearing setting and applied loads. Setting in a tapered-roller bearing system can be defined as the amount of axial clearance (end play) or axial interference (preload) within a mounted set of bearings. It is typically measured in the axial direction because this is the most straightforward way to establish an optimum value.

A conventional tapered-roller bearing with zero endplay has a load zone close to 180°. The special hybrid bearing, in contrast, has a minimum 200° load zone for added rigidity. Setting is key to the bearing fully benefiting from the extended load zone. Setting variation caused by thermal expansion of the spindle-bearing-housing system directly affects spindle static and dynamic stiffness.

It is generally agreed that the optimum setting is the mounted endplay that gives maximum bearing life. However, machine tool and other applications may emphasize system stiffness and heat generation. In this context, the optimum setting is one that results in minimum deflection, counterbalanced with maximum bearing life. Often in these applications, bearing load capacity relative to a fatigue-spall life criterion is well in excess of the machine design life.

In practice, end users install and preload the bearings to manufacturer specs. A fixture applies push-pull forces equal to 3 suggested preload and measures the resulting shaft displacement. The operation typically takes place in a temperature-controlled clean room. This gives total endplay of the bearing system on the spindle. Special software uses the deflection data to calculate a push-pull constant and a spacer length that gives the right dimensional preload. Dimensional preload for taperedroller bearings is defined as the deflection of the inner race (cone) relative to the outer race (cup) at a specified force.

Users subtract the PPC and add the dimensional preload to an existing spacer to establish a final setting. The approach gives a bearing setting that accounts for actual system stiffness and deflections.

ARB Bearings Limited
H-22, Udyog Nagar
New Delhi - 110041, Delhi, India
Phone: +(91)-(11)-25471274 / 25471255 / 25186300
Fax: +(91)-(11)-25475455 / 25470126
Email: info@arb-bearings.comexport@arb-bearings.com,
sales@arb-bearings.com 
For Export Enquiry :
Mr. Divay Rathee : +91-9968373086