August 1st, 2010 by admin

Linear motion bearing is able to simultaneously bear loads and direct linear motion. There are four main categories of linear motion bearings: sliding contact linear motion bearing, rolling element linear motion bearing, hydrostatic or aerostatic linear motion bearing, and magnetic linear motion bearing.
Sliding contact linear motion bearing, also known as plain or journal bearing, carry a load by sliding. Due to their construction, they tend to produce more friction than other types of bearings. This aspect makes them less useful for precision work, although certain low-friction polymers make this type of bearing practical for an increasing number of applications.
Rolling element linear motion bearing, of which linear ball bearing and linear roller bearing are varieties, are far more accurate than sliding contact bearings. Because of their accuracy, low cost, and availability, these bearings are used in a variety of applications.
Hydrostatic or aerostatic linear motion bearings are used in applications requiring a great deal of precision. In hydrostatic or aerostatic bearings, the load is carried by a pressurized liquid which completely separates the two surfaces. These bearings are typically more costly and difficult to implement than rolling element bearings. As a result, they are usually only used in precision work.
Magnet linear motion bearings use magnetic forces from an electromagnet to keep one of the surfaces afloat. Because of the energy expenditure, this type of bearing has very limited applications. However, since they do not need lubrication or wear down from friction, these bearings are useful in clean environments such as semiconductor manufacturing.

Linear motion bearing

July 21st, 2010 by admin

Linear motion bearings are able to simultaneously bear loads and direct linear motion. There are four main categories of linear motion bearings: sliding contact linear motion bearings, rolling element linear motion bearings, hydrostatic or aerostatic linear motion bearings, and magnetic linear motion bearings.
Sliding contact linear motion bearings, also known as plain or journal bearings, carry a load by sliding. Due to their construction, they tend to produce more friction than other types of bearings. This aspect makes them less useful for precision work, although certain low-friction polymers make this type of bearing practical for an increasing number of applications.
Rolling element linear motion bearings, of which linear ball bearings and linear roller bearings are varieties, are far more accurate than sliding contact bearings. Because of their accuracy, low cost, and availability, these bearings are used in a variety of applications.
Hydrostatic or aerostatic linear motion bearings are used in applications requiring a great deal of precision. In hydrostatic or aerostatic bearings, the load is carried by a pressurized liquid which completely separates the two surfaces. These bearings are typically more costly and difficult to implement than rolling element bearings. As a result, they are usually only used in precision work.
Magnet linear motion bearings use magnetic forces from an electromagnet to keep one of the surfaces afloat. Because of the energy expenditure, this type of bearing has very limited applications. However, since they do not need lubrication or wear down from friction, these bearings are useful in clean environments such as semiconductor manufacturing.

July 19th, 2010 by admin

Linear motion products play a critical role in many different kinds of equipment and machinery. Linear motion implies that these products flow in a linear path. Most often this is a back-and-forth motion or side-to-side. Linear motion bearings are an important part of linear motion applications and they are typically classified as either rolling-element bearings or plane bearings. Linear motion products also rely on other related components to function properly including rails, precision shafting, cross rollers, guideways and bellows.

There are a variety of applications for linear motion products. Linear motion bearings are often used for indexing, whether it is in packaging, machining or welding. The sliding motion is also helpful for ergonomics, painting, and moving equipment. Linear motion bearings can be either motorized or non-motorized depending on its application.

The accessories that accompany Linear motion bearings are just as vital as the products themselves. Linear precision shafting provides a track forLinear motion bearings. Customized shafts must be in place to properly fit the bearings for accuracy. Precision shafts are typically formed from alloy steel, carbon steel or stainless steel.

Another component of Linear motion bearings is the ball screw. These help to make a rotational motion product into a linear motion product. These kinds of screws are able to take the heavy thrust loads and minimize friction. Typically, ball screws are used when the highest degree of accuracy is required. Different tools, robots and precision equipment require these components to function at their best. Ball screws are also used in computer-controlled motion-control systems. While acme screws are approximately 50% efficient while ball screws are 90% or higher.

Many machines and tools rely onLinear motion bearings to function properly. While they do come in a variety of different designs for different applications, there is a Linear motion bearing to get just about any job done.

Linear motion bearing

April 1st, 2009 by admin

Rolling-element bearings often work well in non-ideal conditions, but sometimes minor problems cause bearings to fail quickly and mysteriously. For example, with a stationary (non-rotating) load, small vibrations can gradually press out the lubricant between the races and rollers or balls (false brinelling). Without lubricant the bearing fails, even though it is not rotating and thus is apparently not being used. For these sorts of reasons, much of bearing design is about failure analysis.

There are three usual limits to the lifetime or load capacity of a bearing: abrasion, fatigue and pressure-induced welding. Abrasion is when the surface is eroded by hard contaminants scraping at the bearing materials. Fatigue is when a material breaks after it is repeatedly loaded and released. Where the ball or roller touches the race there is always some deformation, and hence a risk of fatigue. Smaller balls or rollers deform more sharply, and so tend to fatigue faster. Pressure-induced welding is when two metal pieces are pressed together at very high pressure and they become one. Although balls, rollers and races may look smooth, they are microscopically rough. Thus, there are high-pressure spots which push away the bearing lubricant. Sometimes, the resulting metal-to-metal contact welds a microscopic part of the ball or roller to the race. As the bearing continues to rotate, the weld is then torn apart, but it may leave race welded to bearing or bearing welded to race.

Although there are many other apparent causes of bearing failure, most can be reduced to these three. For example, a bearing which is run dry of lubricant fails not because it is “without lubricant”, but because lack of lubrication leads to fatigue and welding, and the resulting wear debris can cause abrasion. Similar events occur in false brinelling damage. In high speed applications, the oil flow also reduces the bearing metal temperature by convection. The oil becomes the heat sink for the friction losses generated by the bearing.

April 1st, 2009 by admin

All parts of a bearing are subject to many design constraints. For example, the inner and outer races are often complex shapes, making them difficult to manufacture. Balls and rollers, though simpler in shape, are small; since they bend sharply where they run on the races, the bearings are prone to fatigue. The loads within a bearing assembly are also affected by the speed of operation: rolling-element bearings may spin over 100,000 rpm, and the principal load in such a bearing may be momentum rather than the applied load. Smaller rolling elements are lighter and thus have less momentum, but smaller elements also bend more sharply where they contact the race, causing them to fail more rapidly from fatigue.

There are also many material issues: a harder material may be more durable against abrasion but more likely to suffer fatigue fracture, so the material varies with the application, and while steel is most common for rolling-element bearings, plastics, glass, and ceramics are all in common use. A small defect (irregularity) in the material is often responsible for bearing failure; one of the biggest improvements in the life of common bearings during the second half of the 1900s was the use of more homogeneous materials, rather than better materials or lubricants (though both were also significant). Lubricant properties vary with temperature and load, so the best lubricant varies with application.

Although bearings tend to wear out with use, designers can make tradeoffs of bearing size and cost versus lifetime. A bearing can last indefinitely — longer than the rest of the machine — if it is kept cool, clean, lubricated, is run within the rated load, and if the bearing materials are sufficiently free of microscopic defects. Note that cooling, lubrication, and sealing are thus important parts of the bearing design.

The needed bearing lifetime also varies with the application. For example, Tedric A. Harris reports in his Rolling Bearing Analysis[2] on an oxygen pump bearing in the U.S. Space Shuttle which could not be adequately isolated from the liquid oxygen being pumped, but all lubricants reacted with the oxygen leading to fires and other failures. The solution was to lubricate the bearing with the oxygen. Although liquid oxygen is a poor lubricant, it was adequate, since the service life of the pump was just a few hours.

The operating environment and service needs are also important design considerations. Some bearing assemblies require routine addition of lubricants, while others are factory sealed, requiring no further maintenance for the life of the mechanical assembly. Although seals are appealing, they increase friction, and a permanently-sealed bearing may have the lubricant contaminated by hard particles, such as steel chips from the race or bearing, sand, or grit that got past the seal. Contamination in the lubricant is abrasive and greatly reduces the operating life of the bearing assembly. Another major cause of bearing failure is the presence of water in the lubrication oil. Online water in oil monitors have been introduced in recent years to monitor the effects of both particles and the presence of water in oil and their combined effect.

Deep Groove Ball Bearing
We supply high quality Slewing Ring Bearing, Tapered Roller Bearing, Spherical Plain Bearing, Needle Roller Bearing, Mounted Bearing Unit, Linear Motion Bearing, Automotive Bearing, Self-aligning Ball Bearing also customized bearing per drawing With many years’ experience we have cooperated with several factories and holding the concerned production company.

April 1st, 2009 by admin

Datang Huainan Tianjia An electric power plant maintenance company Xie Xiaoguang QC and his group of home-made electrical clearance measurement tools to measure the diameter of bearing 56 to 200 mm, clearance error of only 0.01 mm, with the traditional motor repair methods Used in pressure lead wire and plug-foot law, smaller and easier to use, high-precision measurements, a wide range to meet the basic measurement of a variety of bearing clearance.

In the coal-fired power plants, motor as a power source unit to ensure the normal operation of the main ancillary equipment. Through statistical analysis, Xie Xiaoguang QC and his team found that as a result of bearing damage caused by electrical fault achieve more than 60%.

How to bearing lower failure rate? Identification of bearing clearance is a key factor in whether or not qualified. Clearance is a ring bearing relative to the other mobile ring bearing the distance, clearance does not meet the technical standards will be affected in the rolling load between the rational distribution and reduce the spin bearings and precision of life.

Bearing clearance commonly used method of measuring test-foot plug lead wire and the pressure test, but both methods fail to pass bearing a lower detection rate and a longer time. Xie Xiaoguang QC and his group draw on collective wisdom and flexibility from a similar working principle of special tools, bearings mounting inner bearing inner ring will be measured fixed, measured the measured outer ring along the radial bearing the greatest amount of activity in order to detect Bearing Value gap. Meter from the base, bearing inner ring mounting (upper and lower), locking nut, Dial, magnetic seat table, table, and other aircraft components. Use will be measured on the bearing inner ring-bearing mounting, the screw tight locking nut, so that the measured bearing inner ring fixed, and then magnetic seat table, table frame Dial will be fixed base in the center of the measuring tool , So that the tip sheet and measured bearing outer ring and vertical surfaces, hand-pushed back and forth bearing outer ring, guide swings at this time Dial is the scope of the test bearing clearance value.

Deep Groove Ball Bearing
We supply high quality Slewing Ring Bearing, Tapered Roller Bearing, Spherical Plain Bearing, Needle Roller Bearing, Mounted Bearing Unit, Linear Motion Bearing, Automotive Bearing, Self-aligning Ball Bearing also customized bearing per drawing With many years’ experience we have cooperated with several factories and holding the concerned production company.

April 1st, 2009 by admin

Continuous casting steel bearings are bearing a. Often used in the application of iron and steel machinery, is a more common bearings. Japan imported brands bearing Seiko has developed a automatically aligning the import of tapered roller bearings. Mainly used in steel casting equipment-driven roller (Guide Roll). The finite element method for strength design, the use of continuous casting and completion of the development of the simulator. Durable life of ordinary auto-aligning tapered roller bearings imports (in the direction of the roll using a fixed-side), 3~4 times.

also can reduce maintenance costs, equipment, iron and steel casting difficult to form a film, a major negative, low-speed, high-temperature, high humidity, casting debris generated when the working environment is extremely bad. In this state, as can easily lead to significant negative orientation of serious roll bending deformation. In order to solve the problem, out of gear set up outside the ring as a sphere, Block-aligning device so that it is not easy curved. To this end SKF, TIMKEN, NSK, and other import brands are more appropriate to develop higher and more high-precision bearings.

Deep Groove Ball Bearing
We supply high quality Slewing Ring Bearing, Tapered Roller Bearing, Spherical Plain Bearing, Needle Roller Bearing, Mounted Bearing Unit, Linear Motion Bearing, Automotive Bearing, Self-aligning Ball Bearing also customized bearing per drawing With many years’ experience we have cooperated with several factories and holding the concerned production company.

March 24th, 2009 by admin

When selecting a ball screw for a machine-tool application, be sure to consider a variety of critical parameters first-including (but not limited to) load profile, linear and rotational speed, rates of acceleration, cycle rate, drive torque limits, environmental issues, required life, lead accuracy and system stiffness. All will have an influence on performance.

In matching a to an application, users may want to pay special attention to other important issues, such as backlash, contamination, operating temperature, and the type of support bearings.

Backlash represents the relative axial motion between the screw and the nut when the motor is not turning. In a vertical motion application, where the load constantly pushes down on the nut, backlash is not so much of an issue. But in non-vertical motion applications, backlash can result in positioning errors.

Avoid backlash by opting for ball screws with preloaded nuts. Preload can be applied with plus-size rolling elements or with an axial force applied to a split/tandem nut. The applied preload eliminates any axial play and increases the assembly’s rigidity and stiffness. (Beyond that, preloaded nuts are subject to less elastic deformation than non-preloaded nuts.)
Contaminants can adversely affect critical internal ballscrew components, machine reliability and uptime. Wipers for ball-screw assemblies are now available with machined nylon, molded polyurethane or felt seals to help prevent damage from contaminants and keep lubricants suitably applied. (Wipers can be mounted internally or externally.)

Screws made from standard steel and operating under normal loads can sustain temperatures of –20 to +110 C. But higher operating temperatures can lower the steel’s hardness, alter thread accuracy and may increase chances of material oxidation or a change in lubricant properties. If the operating temperature range is higher than 110 C, special steels should be selected.

The degree of support on each end of a ball screw in a machine tool will determine how fast the screw can spin and how much load can be handled. Simple supports are typified by ball bearings, which offer good radial stiffness but no axial stiffness; fixed supports (such as pairs of angular contact bearings) will provide stiffness in both directions; and “free support” means no support. Application demands will help guide choices.

OPTIMIZING PERFORMANCE

Ball-screw assemblies in all their varied types and styles can provide long life and efficient service. But a good part of that promise hinges on their design and actual operating conditions. For example, thermal expansion of the screw shaft can lead to systematic positioning errors, which need to be compensated for in the system software. Keeping the operating temperature of the screw to a minimum is critical to high repeatability of positioning.

With an increasing demand for precise positioning, it is important to control the lead error of the screw. Lead precision of a screw can be measured as the difference between the theoretical and actual position on a given number of points To create optimum system stiffness and eliminate backlash, a preloaded screw is required, but at the same time the drive torque is increased. Users must be sure to strike a balance between required preload and running torque for the drive system. Otherwise, if a system is over-preloaded, the operating temperature will suffer.

Excess friction is another influence that can lead to problems and should be minimized by the system design. This often results in stick-slip operation of the ball screw and can cause torque variations, random positioning errors, or overshooting of the desired position.

BASIC TROUBLESHOOTING

When a pending failure of a ball screw is on its way, warning signals will often emerge:
• Fatigue or Surface Distress on the Screw Shaft. Periodic visual inspection can identify pitting or spalling (typically caused by contaminants) or brinelling (imprint of the ball bearing in the raceways). Repairs can typically be made in all three instances; otherwise, users risk catastrophic ball-screw failure.
• Heat Discoloration on Balls and Screw Shaft. This signals heat buildup, often due to lack of lubrication, contaminated lubricant or inadequate system cooling. Another source of heat could be caused when the return circuits are jammed and balls are not properly recirculating. The resulting heat generation will adversely affect performance and life of the ball screw.

along the working stroke. When two screws are used in parallel, units with matched leads should be employed, unless they can be controlled independently with a linear encoder.
• Wipers and Seals Loose or Missing. Simple inspection of seals and wipers can instill confidence that metal chips and corrosive dust remain restricted from doing damage to internal ballscrew components.
• Excessive Vibration. This may suggest the screw shaft is bent, causing it to whip or whirl during operation, creating heightened levels of vibration. The integrity of the shaft should be checked and returned for possible repair or straightening.
• Clicking Sound in Recirculation Tube. Depending on the noise intensity, there may be no immediate cause for alarm, since there is no load on the ball bearings when they are in the tube. However, should the clicking sound get progressively louder, it could indicate a broken return tube strap or dented tube.
• Loss of Positioning Accuracy. This is generally caused by loss of preload from wear or contamination, or endplay in the support bearings. Check the positioning accuracy with a machine tool’s controls by monitoring the error count.
• Excessive Power Draw. Potential causes can include excessive preload, ball recirculation problems or lack of lubricant in the ball screw. Discrepancies from designated, acceptable ranges can be found by monitoring a machine’s amp meter.
In most cases, repairs to ball screws in the early stages of failure can be accomplished quickly, if problems are red-flagged before major damage occurs. Repairs (best handled by professionals) can involve polishing or regrinding the screw shaft and replacing the nut or even simply reloading the assembly (cleaning and polishing screw and nut and preloading with new ball bearings).

ball bearing, Linear motion bearing