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“What are Linear Bearings?
Linear bearings are a type of bearing that “”bear”” or support the load of the carriage during its single-axis linear movement and provide a low friction sliding surface for the guide rails. In a linear guide, the carriage is the component that travels in a straight line, back and forth, along the length of the guide rail. The guide rail is fitted and inserted into the linear bearing.
A linear bearing is a critical component of the linear guide assembly. Its applications are in cutting machinery, X-Y positioning tables, machine slides, industrial robots, and instrumentation systems. Either a motor-driven ball screw, lead screw, or manual force can be used to drive the motion. The single-axis motion is limited in the X-Y plane.
The types of linear bearings are divided into two main classifications: the rolling linear bearings and the plain linear bearings.
Linear Bearing Materials of Construction
The materials for constructing linear bearing components are the following:
Steel, an alloy primarily composed of carbon and iron, is the most popular material selection for linear bearings. Steel linear bearings are known to have excellent mechanical properties (i.e., high strength and rigidity); this can support heavy loads and provide smooth and precise motion. Carbon steel and stainless steel are common types of steel used in constructing steel linear bearings. Increasing the carbon content increases the hardness of steel; this affects the performance of the linear bearing.
Aluminum is a lightweight but high-strength metal. It is corrosion and chemical resistant. It is softer and less expensive than steel. However, aluminum linear bearings have lower load capacity than steel linear bearings. Aluminum linear bearings are also capable of providing smooth and precise motion.
Plastic linear bearings are softer, cheaper, and have a lower coefficient of friction than metallic bearings. Typical plastics used in linear bearings are nylon, polyethylene, and PVDF, and they are usually lined with a self-lubricating coating (e.g., PTFE). They are sometimes reinforced with fibers and fillers to enhance their weight-bearing capabilities. Plastic linear bearings can be used with softer shaft materials. However, they generally have lower load capacities and are limited to room temperatures.
Bronze is an alloy mainly composed of copper and zinc, with other additives such as manganese and phosphorus. It is a soft metal. Bronze linear bearings have a higher load capacity than plastic linear bearings. Because of the presence of metal-to-metal contact, however, they generate greater friction than plastic bearings; this necessitates maintenance of sufficient lubrication.
Ceramic linear bearings are typically fabricated from silicon nitride, aluminum oxide, zirconium oxide, and silicon carbide. They have high rigidity, which maintains travel accuracy and precision at high speeds. They have a high hardness, which increases their service life and abrasion resistance and reduces the generated particles from sliding of bearing components. They are also compatible with vacuum and ESD-sensitive devices and equipment.
In recirculating linear bearings, ceramic rolling elements are utilized for their higher speeds.
Composite bearings consist of a metal backing and a plastic sleeve or a PTFE liner. The polymeric component eliminates metal-to-metal contact; this lowers the coefficient of friction while maintaining the high load capacity of the bearing. The metal backing allows the bearing to dissipate its heat.
It is common practice to use different materials for the bearing and the guide rail; with the guide rail, it is usually harder to reduce friction. Material wear is concentrated in the contact surface of the linear bearing, which is the softer component. The guide rails, shafts, and bases (for plain linear bearings) are commonly constructed from hardened steel, ground steel, and anodized aluminum, which are all harder types.
What Is a Rod End Bearing?
A rod end bearing is a common type of mechanical joint used on the ends of control rods. The steering columns in most cars, trucks and other vehicles, for example, feature tie rods with a rod end bearing. Of course, tie rods are designed to connect a vehicle’s steering rack to its steering knuckle. As a result, tie rods must be able to rotate according to the direction in which the wheel is turned. Rod end bearings allow tie rods to perform this rotation in a precise and controlled manner. To learn more about rod end bearings and how they work, keep reading.
Rod End Bearings Explained
Also known as a heim joint in the United States or a rose joint in the United Kingdom, a rod end bearing is a mechanical joint that features a rounded ball-like swiveling tip. They were invented in Germany during the 1930s to 40s for use in aircraft control systems. This promoted a company called H.G. Heim Company to patent and produce its own rod end bearings in North America, which is why the mechanical joint now has the moniker “heim joint.”
H.G. Heim Company has since closed its doors for business, but rod end bearings are still produced and used throughout the world. Automotive tie rods are just way in which rod end bearings are used. They are used in countless other applications in which an articulating joint is needed, including aircraft control systems, steering links, track rollers and more.
Rod end bearings are typically made using the following materials:
Male vs Female Rod End Bearing: What’s the Difference?
A rod end bearing can be classified as either male or female depending on the way in which the threading is designed. Male rod end bearings are designed with external threading. In comparison, female rod end bearings are designed with internal threading. With interior threading, female rod end bearings can handle unique applications that aren’t possible with male rod ends bearings. Helicopters, for instance, often use female rod end bearings to adjust the direction of the blade. They allow pilots and aviation technicians to fine tune their blade adjustments.
A pulley is a mechanical device which contains a wheel and rope/belt/chain to lift the heavy objects. The wheel of the pulley is generally fixed to a hinge and rotates on an axle or shaft. In a simple arrangement of the pulley, chain/rope/belt/cable is the driving element that drives over the wheel. At the one end of the rope, the object is loaded, and from the end, when the rope is pulled down the object lifts. To lift large objects an assembly of pulleys are used. These are also used to transfer power from one rotating shaft to another. The advantage of the use of pulleys is that by applying a little force heavy objects can be lifted. In other words, the pulleys multiply the force to lift the heavyweights which cannot be lifted with bare hands.
Types of Pulleys
In the process of doing some work, a pulley is a simple machine that changes the direction and magnitude of the applied force. The rope and pulley system is also known as black and tackle system. There are three types of pulleys,
Fixed: A fixed pulley is mounted on an axle that has bearings at its centre. The wheel of the pulley is fixed on this axle in such a way that it rotates on its centre point. A rope is now surrounded by this wheel so that it can move circumferentially. Sometimes this wheel has grooves which help to rotate the rope around it easily.
Movable: In a movable pulley, the block is mounted on a movable axle which moves along with the weight to be lifted. These pulleys are often attached to the object and multiply the operator’s force which the operator applies to the machine. The movable pulley does not change the direction of the object. It is useful to pull up heavier loads as the operator has to exert less force and the resultant force on the load is the multiplication of the operator’s force.
Compound: In this class of pulleys, several pulleys are fixed and several pulleys are attached to these fixed pulleys with single or multiple ropes. More is the number of wheels less the effort or force to apply to lift heavyweight. This system not only changes the direction of the load but also requires less force to lift heavy objects.
Measurement of the Performance of Pulley
A term mechanical advantage is coined to calculate the effectiveness of the pulleys. The mechanical advantage of a system is the ratio of force utilised to the force applied to the work. To calculate the mechanical advantage of pulley and rope system, it is assumed that the weights of pulleys and ropes are negligible and there is no loss of energy due to friction between rope and wheel’s grooves. And it is also assumed that the ropes/belts/chains used in the operation do not deform (elongate) during the operation.
The mechanical advantage of the pulley system is directly proportional to the number of loops of the rope. In a single loop system, the efforts required to pull the weight is equal to the weight itself. By introducing another loop of rope (adding another wheel attached to the first wheel by additional rope) the effort requires to pull the same weight becomes half as compared to the previous arrangement.
In this case, the mechanical advantage will be 2. If another loop introduced, the effort becomes one third as compared to the first arrangement and therefore, the mechanical advantage is 3. To increase the mechanical advantage, more pulleys can be added. But after a certain number of pulleys, the mechanical advantage does not change and becomes constant.
Advantages and Disadvantages
The main advantage in the use of pulleys is that the effort becomes less as compared to the normal lifting of the weights. In other words, it reduces the amount of actual force required to lift heavy objects. It also changes the direction of the force applied. These two advantages in the use pulleys make them an important tool for heavy lifting. It also provides a mechanical advantage.
The other advantage in the use of pulleys is that the distance between the operator and weight. There is a safe distance between them which avoids any disaster. Pulleys are easy to assemble and cost-effective. The combination of different directional pulleys can change the position of the load with little effort. Though there are moving parts in the pulley system they require less or no lubrication after installation.
Apart from the above-said advantages while using pulley systems, there are several disadvantages in their use. The main disadvantage in the use of the pulley system is that it requires large space to install and operate. The mechanical advantage of pulleys can go to higher values but need more space to install them.
In some cases, the ropes/belts move over the wheel with no grooves, the chances of the slip of ropes/belts from the wheel are inevitable. If the system is installed to use for a long time, they require maintenance and regular check-up of ropes/cables as the friction between the wheels and cables/ropes occur causing wear and tear to them. Continuous use of the system makes the ropes weak. The rope may break while using the system causing damages to the operator, surrounding place and the load which is being lifted.
3D printing of spare parts
The costs of spare parts are usually more than 60% of all the operation maintenance costs in industry. The use of professional 3D printers in many sectors has already become a standard. A growing number of companies perceive the pronounced advantages of the opportunity to make 3D printouts of industrial machine elements which get worn and torn in the daily operation.
Industry may not allow for downtimes or freezing money in spare parts. 3D printing helps companies solve the problems with operation maintenance, overloaded warehouses and delays in delivery of finished products to end customers.
Manufacturing without downtimes thanks to 3D printing
A manufacturing line downtime may occur due to a failure of a key element. Such situation exposes companies to financial losses which may grow with time, when awaiting a replacement, which may even last a few weeks.
What is more, original parts for elements to be replaced are also related to high costs which the company will have to incur. Although some may hardly believe it, 3D printouts perform well in replacing many parts used in finished products, as well as accelerate or shorten the production time and significantly lower the costs of the whole process.
3D printed spare parts – effective solution for companies
Covers and casings, small-sized spare parts for the automotive industry or radio-television or household equipment, non-standard tools and handles ,coupling and other 3D parts – all that may be created thanks to 3D printing technologies in a fast and economic manner.
Lead Screw | Applications, Advantages, Disadvantages, Types
What is a lead screw?
Lead screw is a type of screw which is used as linkage in machines. It converts rotary (or turning) motion into linear motion.Due to large contact area between male and female members of a lead screw, it has very high frictional losses.
Advantages of lead screws
-They are generally self-locking
-They have minimum number of parts
-Their working is quiet
-They require very less maintenance
-They offer very precise and accurate linear motion
-They offer very large mechanical advantage
-They are easy to manufacture since no specialized machinery is involved in its manufacturing
-They are simple to design
-They are compact
-They have very high load carrying capacity
Disadvantages of lead screw
-They have very poor efficiency
-Due to very high friction between male and female parts, wear and tear is high
Applications of lead screw
-Types of lead screws
Lead screws are classified on the basis of type of thread used. Hence, they can be classified into following three types.
What is the function of leadscrew?
The function of a lead screw is to convert turning motion into linear motion.
What is the difference between a leadscrew and a ball screw?
In ball screws surface friction is replaced by the rolling friction of balls, which is much lower. A ball screw is much more efficient than leadscrew.