Recently, C&U Group was announced to be selected as High-tech Enterprise Certificate for the year 2008. Beside, its seven subsidiaries also won this title at the same time, they are C&U Group Wenzhou Company,,Wenzhou Jingyin Bearing Co.Ltd,Shanghai Sibote Bearing Tech Development Co.Ltd,C&U Group Wuhu Company,Wuhu Sanxing Bearing Co.,Ltd,C&U Group Shanghai Company,Huangshi Hatebei'er Precision Forging Co., Ltd.

It is reported that the high-tech enterprises can enjoy 15% off for the income tax.

China pledged to maintain a steady growth in foreign trade this year amid sharp declines in external demand and a rise in international trade protectionism.

Premier Wen Jiabao yesterday said in his government work report at the opening of the annual session of the National People's Congress that the government will take a series of measures to help exporters address difficulties amid the global economic downturn and to ensure steady growth in foreign trade.

Another report released by the country's top planner, the National Development and Reform Commission, yesterday predicted that the country's foreign trade volume would grow by 8 percent year-on-year this year, compared to the 17.8 percent growth seen last year. That means the value of foreign trade would touch $2.76 trillion this year.

Hit by the global credit crisis, Chinese exporters are suffering from declining demand and increasing defaults in deals.

A research by China Council for the Promotion of International Trade said Chinese companies' uncollectible debts in exports to the US market increased by two to three times last year, which made many exporters not confident enough to take further orders.

Premier Wen said a central government fund for trade development will be increased in order to encourage branded export products and support small- and medium-sized enterprises in expanding their international markets.

The government will expand the coverage of export credit insurance and encourage financial institutions to develop export credit to improve the country's financial services for imports and exports.

China will adjust the prohibited or restricted commodity categories of processing trade, and encourage the relocation of export processing industries from the eastern to the central and western regions.

Ningbo Sunthai Bearing Co.,Ltd
ADD: NO.1730 Liyuan North Road,Ningbo, China
TEL: 86-574-87220319-8013
FAX: 86-574-87223781
MSN: maggie_perfect@hotmail.com
Email: stb888@sunthaibearing.com
Website: www.fbearing.com  www.sunthaibearing.com

Iglide plastic bearings come in 20 material blends and in more than 6,000 stock metric and inch sizes and styles.

All iglide bearings are self-lubricating and maintenance-free. Iglide bearings will not corrode, give excellent vibration dampening, and resist UV.

Such factors as speed, load and temperature mostly determine bearing suitability for an application. A predictability calculator, based on considerable data gathered in the lab and field, helps determine wear rates and bearing performance.

Applications for iglide bearings include agricultural and lawn equipment, construction, fitness and sports equipment, semiconductor production equipment, medical devices, textile machinery, machine tools, packaging and material-handling machinery, and automotive equipment.

Ningbo Sunthai Bearing Co.,Ltd
ADD: NO.1730 Liyuan North Road,Ningbo, China
TEL: 86-574-87220319-8013
FAX: 86-574-87223781
MSN: maggie_perfect@hotmail.com
Email: stb888@sunthaibearing.com
Website: www.fbearing.com  www.sunthaibearing.com

Contact Angle

Contact angle is an important consideration at high speeds. This angle measures the difference between the ball-to-raceway contact line and a plane through the ball center perpendicular to the bearing axis. Higher angles provide more axial stiffness in the direction of the applied thrust load.

The contact angle is key to optimizing the mounting arrangement of duplex spindle bearings. The most common is back-to-back mounting where angles diverge toward the shaft centerline. It resists overturning loads and provides effective operation in both float and fixed positions.

Face-to-face mounting has angles converging toward the shaft centerline. It provides equal thrust capacity in either direction, as well as radial and axial rigidity. Tandem mounting has parallel angles for double-thrust capacity in only one direction.

In other arrangements, a flush-ground tandem set of two or three bearings may mount back-to-back in combination with a single flush-ground bearing to form a triplex or quadruplex set. Triplex configurations provide high thrust capacity in one direction in a rigid mounting carrying a moderate amount of reverse thrust. The quad set provides higher thrust capacity in both directions.

Most superprecision bearing manufacturers offer contact angles ranging from 25 to 15°. Low contact angles are more rigid radially and less rigid axially, allowing more axial yield and less radial deflection than high contact angles.

In general, use low-contact-angle bearings where the operating load is principally radial. Experts recommend higher-contact-angle bearings where the application involves chiefly thrust loads and requires a high degree of axial rigidity. Thus, most machine-tool applications use low contact angles. However, when maximum axial rigidity is required in combination with heavy thrust loads, bearings with higher contact angles are preferred.

Timken recommends a 15° contact angle for high-speed machining. Higher speeds drive the rolling elements outward. The contact angle tends to increase on the inner ring (away from the bottom of the raceway) while decreasing on the outer ring (toward the bottom of the raceway). Take, for example, a bearing with a 15° design contact angle on both inner and outer rings (1:1 ratio) at low speeds. In a particular high-speed application, the inner ring angle increases to 20.3° while the outer ring angle reduces to 9.7° (a 2:1 ratio).

The ratio of inner to outer ring contact angle should be no greater than 2:1 for maximum ball control and dynamic stability. A ratio exceeding 3:1 will induce ball skidding and heat generation. A 15° contact angle combined with proper internal geometry keeps this important ratio between 1.2:1 and 1.5:1. Superior performance characteristics will result, including improved dynamic stiffness, stable operating temperatures, and the ability to accommodate interference fits required for high speeds.

Additional considerations

Cages. Cage material, tolerances, and guidance all affect bearing performance. Phenolic is currently recommended because it's light, absorbs oil for more lubricity, and maintains pocket integrity. Holding precise tolerances on ball pockets and pilot diameters ensures the cage and rolling elements spin in the same axis. The bearing industry has not agreed on the best practice for cage guidance. Some manufacturers believe the inner ring diameter grows at speed, and it should guide the cage. Timken studies show that the cage grows and should be guided by the outer ring. Timken Fafnir designs are based on outer-ring guidance with tight controls to avoid cage precession at high speeds and loads.

Shoulder construction. The design and dimensions of the raceway shoulders can affect high-speed machining. While the thrust sides of inner and outer raceways require maximum shoulder height, low shoulders on the nonthrust sides let oil flow through the bearing. Improved lubrication of contact surfaces helps reduce operating temperatures in high-speed, oil-lubricated systems.

Surface finish. Most bearing manufacturers strive for an average surface finish of 2 to 4 R_a for inner and outer raceways, depending on bearing size. Average finish, however, is not the best indicator of optimum operating smoothness. In reality, it is the peaks or asperities, not the valleys, that impact antifriction performance. Any protrusion capable of penetrating the oil film separating the rolling elements from the raceways is a source for concern. A uniform finish with low peak content provides the smooth rolling contact necessary to maintain low operating temperatures and maximize service life.

Some manufacturers leave unfinished many nonfunctional surfaces, such as counterbores, corners, and ring lands. While these noncontact areas do not directly affect bearing performance, Timken has determined that these surfaces can trap debris and impact cleanliness. The extra step of grinding nonfunctional surfaces improves overall cleanliness and justifies the effort.

Cleanliness. The impact of superprecision-bearing cleanliness on machine-tool performance is widely acknowledged, and most manufacturers assemble, test, and package their bearings in clean rooms. Points of contamination can rapidly become a source for abrasion, cracks, or spalling, as well as lubricant-film breakdown.

Timken field research indicates that hard particulate contamination and/or marginal lubrication are the most common causes of machine-tool spindle bearing failure. Contaminants, not fatigue, limit service life and performance in the inherently high-debris environment of machine tools. Contamination generally causes excessive bearing raceway wear and increases temperature and noise. The impact on the tool spindle will be unacceptable runouts and vibration.

Seals. While seals are needed to prevent contamination and lubrication problems, the challenge of high speeds proved to be beyond the capabilities of even the most advanced contact seals. Noncontact dynamic seals are now available to keep contamination out of the bearing while minimizing running torque for high-speed operation. These seals effectively retain grease inside the bearing, making it maintenance free compared to open, oil-lubricated bearings. Extended bearing service life reduces machine-tool maintenance requirements and eliminates the costs associated with expensive oil/mist lubrication systems.

Ring materials. The bearing industry is also looking at new ring materials that resist contamination-induced surface damage and improve performance. Special high-alloy steels have recently been developed with higher hardness, compressive yield strength, and dent resistance than 52100 and other high-nitrogen steels. Special processing provides a more-uniform microstructure with greater wear resistance.

Ningbo Sunthai Bearing Co.,Ltd
ADD: NO.1730 Liyuan North Road,Ningbo, China
TEL: 86-574-87220319-8013
FAX: 86-574-87223781
MSN: maggie_perfect@hotmail.com
Email: stb888@sunthaibearing.com
Website: www.fbearing.com  www.sunthaibearing.com

Ball bearings bring the smooth feel of car steering to boats
 

Basics of Design Engineering Bearings

Teleflex Morse tilt-steering columns come equipped with ball bearings from Hartford Technologies. Boat-steering controls fitted with steel ball bearings are stiffer, more responsive, and smoother than controls with nylon bushings, says marine-steering maker Teleflex Morse Inc., Limerick, Pa Teleflex tapped Hartford Technologies, Rocky Hill, Conn., for the modular bearings when nylon bushings couldn't handle the high loads or meet tolerance specs. The bearings support the steering drive shaft. Hartford took existing bearings and upgraded them for saltwater service. This involved changing out carbon steel balls for 440 C stainless-steel equivalents and applying a corrosion-resistant coating to races. The updated steering column then underwent 18 months of rigorous testing at Teleflex. It is now slated for production in a line of premium pleasure boats.       Ningbo Sunthai Bearing Co.,Ltd ADD: NO.1730 Liyuan North Road,Ningbo, China TEL: 86-574-87220319-8013 FAX: 86-574-87223781 MSN: maggie_perfect@hotmail.com Email: stb888@sunthaibearing.com Website: www.fbearing.com  www.sunthaibearing.com

 

MRC Bearings now offers precision-finished, silicon-nitride rollers separately, or installed in its line of aerospace hybrid roller bearings.

MRC Bearings,a div. of SKF, Jamestown, N.Y. now offers precision-finished, silicon-nitride rollers separately, or installed in its line of aerospace hybrid roller bearings. MRC uses Cerama SN-101C silicon nitride ceramic roller blanks from Saint Gobain Ceramics,East Granbury, Conn. Hybrid roller bearings (silicon-nitride roller in metal races) are said to last longer and run faster than their all-steel counterparts. Silicon nitride has just 40% the density of steel, which lowers rotational inertia and centrifugal force. Lower friction and less wear from smooth, hard ceramic surfaces let hybrid bearings run cooler with less lubricant. Applications for ceramic rollers include precision bearings for aerospace, machine tools, and racing. --Lawrence Kren Ningbo Sunthai Bearing Co.,Ltd ADD: NO.1730 Liyuan North Road,Ningbo, China TEL: 86-574-87220319-8013 FAX: 86-574-87223781 MSN: maggie_perfect@hotmail.com Email: stb888@sunthaibearing.com Website: www.fbearing.com  www.sunthaibearing.com

                                                                     The need for speed
 

Motion-component manufacturers like SKF are experimenting with hybrid material rail guides to decrease weight and increase attainable speeds. Today's motion-control applications often demand higher speeds to boost productivity and throughput. When you get right down to it, the system's mass largely determines maximum speed. And that has led manufacturers to reexamine the materials they use to build components. One trend is the increasing interest in hybrid materials for motion-system components such as rail guides. Hybrid products offer the potential for lighter weight and higher performance. As an example in linear-guidance systems, profile rail guides have begun to evolve in this direction with emerging hybrid designs. Conventional steel linear-profile rails guides usually consist of a profile rail with four precision-ground raceways and a slide unit with four ball-circulation paths. This design offers a number of benefits. Specifically, square configuration raceways result in a guidance system with good rigidity, capable of withstanding moment loads in all directions, with equal load-carrying capacity in all four directions. Also, ready-to-mount units can minimize installation and adjustment requirements and the design of these systems can compensate for inaccuracies in adjacent components. Hybrid guide technology can potentially deliver other advantages by reducing drive power requirements and a machine's overall manufacturing and operating costs. An inherent drawback of traditional linear-rail guides is that the weight of the steel rails and slide units naturally limits a machine's operating speeds: inertia increases linearly with mass and acceleration. As a result, the feasibility of lightweight designs is gaining interest to help promote more dynamic production, transport, and handling systems. For instance, reducing weight to 80% of previous levels means significantly less system inertia, and speeds to 10 m/sec. The density of steel historically used for guides (approximately 8 gm/cm3) is almost three times the density of aluminum (less than 3 gm/cm3), making aluminum a viable material for hybrid guides. Hybrid bearings can incorporate aluminum, engineered plastics, and hardened steel inserts for roller contacts. The composite designs lower rail-guide weight without significantly reducing load-carrying capacity. Interest in lighter profile rail guides has been generated, in part, by an increasing number of smaller and lighter products to be transported or positioned in high-tech industries, leading to a quest for smaller and lighter machines. Today, size and weight have earned virtually equal attention with requirements for load-carrying capacity and stiffness when designing linear systems. Another reason for the interest is the systems themselves. Multiaxis handling systems, in particular, stand to benefit from lightweight hybrid guides. In these systems, the base axis must support two, three, or even four other axes. Weight reductions of the supported axes could add up considerably to offer previously unattainable increases in the dynamics of the base axis and machine performance. The first hybrid rail-guide designs consisted of a lightweight material to provide the required structural stiffness and a special steel to promote running accuracy between the rails and rolling elements, as well as the load-carrying capacity of the system. Prototype linear-profile rail guides replace the conventional heavyweight steel rails with special lightweight materials. Only special steel raceways are incorporated into the rail body. Hardened raceways accommodate the high Hertzian stress typically associated with rolling-element bearings. Further prototype development and evaluation have shown aluminum base bodies can be up to 65% lighter, and as much as 80% lighter for lightweight material/metal systems, without sacrificing system stiffness or running accuracy and repeatability. Full production of standard off-the-shelf hybrid linear-profile rail guides awaits further testing and refinements with traditional production methods. In the meantime, an accelerated search is currently underway for suitable materials, whether aluminum, ceramic, or other appropriate alternatives to lower weight, increase speeds, and improve corrosion resistance. However, depending on the type of materials used, there could be some reductions in operating temperature limits. Regardless of material choices, using hybrid rail guides calls for close cooperation between machine designers and linear-guide specialists in the early stages of machine design: In particular, bringing performance characteristics such as stiffness and running accuracy in line with material capabilities.  From SKF

Ningbo Sunthai Bearing Co.,Ltd
ADD: NO.1730 Liyuan North Road,Ningbo, China
TEL: 86-574-87220319-8013
FAX: 86-574-87223781
MSN: maggie_perfect@hotmail.com
Email: stb888@sunthaibearing.com
Website: www.fbearing.com  www.sunthaibearing.com

Contact Angle

Contact angle is an important consideration at high speeds. This angle measures the difference between the ball-to-raceway contact line and a plane through the ball center perpendicular to the bearing axis. Higher angles provide more axial stiffness in the direction of the applied thrust load.

The contact angle is key to optimizing the mounting arrangement of duplex spindle bearings. The most common is back-to-back mounting where angles diverge toward the shaft centerline. It resists overturning loads and provides effective operation in both float and fixed positions.

Face-to-face mounting has angles converging toward the shaft centerline. It provides equal thrust capacity in either direction, as well as radial and axial rigidity. Tandem mounting has parallel angles for double-thrust capacity in only one direction.

In other arrangements, a flush-ground tandem set of two or three bearings may mount back-to-back in combination with a single flush-ground bearing to form a triplex or quadruplex set. Triplex configurations provide high thrust capacity in one direction in a rigid mounting carrying a moderate amount of reverse thrust. The quad set provides higher thrust capacity in both directions.

Most superprecision bearing manufacturers offer contact angles ranging from 25 to 15°. Low contact angles are more rigid radially and less rigid axially, allowing more axial yield and less radial deflection than high contact angles.

In general, use low-contact-angle bearings where the operating load is principally radial. Experts recommend higher-contact-angle bearings where the application involves chiefly thrust loads and requires a high degree of axial rigidity. Thus, most machine-tool applications use low contact angles. However, when maximum axial rigidity is required in combination with heavy thrust loads, bearings with higher contact angles are preferred.

Timken recommends a 15° contact angle for high-speed machining. Higher speeds drive the rolling elements outward. The contact angle tends to increase on the inner ring (away from the bottom of the raceway) while decreasing on the outer ring (toward the bottom of the raceway). Take, for example, a bearing with a 15° design contact angle on both inner and outer rings (1:1 ratio) at low speeds. In a particular high-speed application, the inner ring angle increases to 20.3° while the outer ring angle reduces to 9.7° (a 2:1 ratio).

The ratio of inner to outer ring contact angle should be no greater than 2:1 for maximum ball control and dynamic stability. A ratio exceeding 3:1 will induce ball skidding and heat generation. A 15° contact angle combined with proper internal geometry keeps this important ratio between 1.2:1 and 1.5:1. Superior performance characteristics will result, including improved dynamic stiffness, stable operating temperatures, and the ability to accommodate interference fits required for high speeds.

Additional considerations

Cages. Cage material, tolerances, and guidance all affect bearing performance. Phenolic is currently recommended because it's light, absorbs oil for more lubricity, and maintains pocket integrity. Holding precise tolerances on ball pockets and pilot diameters ensures the cage and rolling elements spin in the same axis. The bearing industry has not agreed on the best practice for cage guidance. Some manufacturers believe the inner ring diameter grows at speed, and it should guide the cage. Timken studies show that the cage grows and should be guided by the outer ring. Timken Fafnir designs are based on outer-ring guidance with tight controls to avoid cage precession at high speeds and loads.

Shoulder construction. The design and dimensions of the raceway shoulders can affect high-speed machining. While the thrust sides of inner and outer raceways require maximum shoulder height, low shoulders on the nonthrust sides let oil flow through the bearing. Improved lubrication of contact surfaces helps reduce operating temperatures in high-speed, oil-lubricated systems.

Surface finish. Most bearing manufacturers strive for an average surface finish of 2 to 4 R_a for inner and outer raceways, depending on bearing size. Average finish, however, is not the best indicator of optimum operating smoothness. In reality, it is the peaks or asperities, not the valleys, that impact antifriction performance. Any protrusion capable of penetrating the oil film separating the rolling elements from the raceways is a source for concern. A uniform finish with low peak content provides the smooth rolling contact necessary to maintain low operating temperatures and maximize service life.

Some manufacturers leave unfinished many nonfunctional surfaces, such as counterbores, corners, and ring lands. While these noncontact areas do not directly affect bearing performance, Timken has determined that these surfaces can trap debris and impact cleanliness. The extra step of grinding nonfunctional surfaces improves overall cleanliness and justifies the effort.

Cleanliness. The impact of superprecision-bearing cleanliness on machine-tool performance is widely acknowledged, and most manufacturers assemble, test, and package their bearings in clean rooms. Points of contamination can rapidly become a source for abrasion, cracks, or spalling, as well as lubricant-film breakdown.

Timken field research indicates that hard particulate contamination and/or marginal lubrication are the most common causes of machine-tool spindle bearing failure. Contaminants, not fatigue, limit service life and performance in the inherently high-debris environment of machine tools. Contamination generally causes excessive bearing raceway wear and increases temperature and noise. The impact on the tool spindle will be unacceptable runouts and vibration.

Seals. While seals are needed to prevent contamination and lubrication problems, the challenge of high speeds proved to be beyond the capabilities of even the most advanced contact seals. Noncontact dynamic seals are now available to keep contamination out of the bearing while minimizing running torque for high-speed operation. These seals effectively retain grease inside the bearing, making it maintenance free compared to open, oil-lubricated bearings. Extended bearing service life reduces machine-tool maintenance requirements and eliminates the costs associated with expensive oil/mist lubrication systems.

Ring materials. The bearing industry is also looking at new ring materials that resist contamination-induced surface damage and improve performance. Special high-alloy steels have recently been developed with higher hardness, compressive yield strength, and dent resistance than 52100 and other high-nitrogen steels. Special processing provides a more-uniform microstructure with greater wear resistance.

Ningbo Sunthai Bearing Co.,Ltd
ADD: NO.1730 Liyuan North Road,Ningbo, China
TEL: 86-574-87220319-8013
FAX: 86-574-87223781
MSN: maggie_perfect@hotmail.com
Email: stb888@sunthaibearing.com
Website: www.fbearing.com  www.sunthaibearing.com

Ceramic bearing balls help injection-molding machines go green
 

Basics of Design Engineering - Bearings

Umbra ball screws equipped with Cerbec silicon-nitride bearing balls handle loads to 1,800 kN, axial speeds to 160 m/min, and accelerations to 3 g. The use of Cronidur 30 steel for certain components helps the units resist corrosion. Electromechanical injection-molding machines that run only when making parts consume about half to a third the energy of hydraulic-based equivalents that idle between cycles. The all-electric machines also generate about 65 to 70% less waste heat, lowering plant air-conditioning costs. Conventional injection-molding machines use a complex network of hydraulic actuators, hoses, tubes, filters, and valves to shut molds and inject molten plastics. Leaks are common, especially of concern now because of more stringent environmental regulations. In contrast electromechanical types swap out the hydraulics for simpler, cleaner, ball screws and electric drive motors. The ball screws transmit rotary-to-linear motion for injection slides and for clamping molds shut during the injection process. Umbra Cuscinetti, Umbra Group, Italy, makes ball screws for aerospace and industrial applications and recently applied the technology to molding machines. High loads and lack of proper maintenance and lubrication typify conditions in this application. Helping ball screws survive the rigors are Cerbec silicon-nitride bearing balls from Saint-Gobain Advanced Ceramics, East Granbury, Conn. "Alternating large silicon-nitride balls with smaller steel balls cuts adhesion, boosts load capacity and reliability, and extends ball-screw lifetime," explains Umbra Cuscinetti Stress Analyst and R&D Chief Engineer, Luciano Pizzoni. "The arrangement also lets users switch from oil to grease lubrication. Grease is more environmentally friendly and doesn't need replenishing as often."     Ningbo Sunthai Bearing Co.,Ltd ADD: NO.1730 Liyuan North Road,Ningbo, China TEL: 86-574-87220319-8013 FAX: 86-574-87223781 MSN: maggie_perfect@hotmail.com Email: stb888@sunthaibearing.com Website: www.fbearing.com  www.sunthaibearing.com