Rollers and wheels for industrial uses – Construction and applications

In mechanical engineering and in general automation processes, it is essential that materials and construction components are transported quickly and efficiently from A to B. This requires purposeful guidance and alignment along the conveying paths. Rollers and also drums contribute significantly toward fulfilling these functions. This article examines which types of materials are used and for which specific applications rollers are used.

Definition: Rollers, drums, wheels, bandages and their construction

For the purposes of mechanical engineering, a roller is an annular disk-shaped (hollow-cylindrical) machine element that is rotatably mounted on an axle or a roller pin as an axis of rotation such that it can rotate with the least-possible friction. The differentiation between roller and drum, also called carrier drum, does not refer to the function, but rather to their geometry. Rollers and drums are both hollow cylinders seen geometrically and differ by their ratio of component radius to component height. If the width of the rolling surface of a roller exceeds its radius, this is usually referred to as a drum.

Wheels are also components that enable a rolling movement. However, compared to rollers, wheels usually consist of a rim, a bandage (running surface) and a wheel bearing. An axle or a bearing pin connects the wheel body to the housing and ensures a secure seat in the holder. A bandage is the protective or wear coating applied onto a roller or wheel, also called rolling surface. This also influences the ease of movement.

Different bandages should be selected depending on the floor conditions. For example, rubber features a high degree of floor protection, but has a comparatively high startup and rolling resistance. Metal coatings have a very high load capacity, but are not suitable for sensitive floors due to the high surface contact pressure. Specialized high-performance plastics, which compel with their low weight and high wear resistance, are also used by industry.

In contrast to wheels, rollers directly absorb the load on the outer ring (direct contact). This distinguishes rollers from pure ball bearings, which - due to their range of applications and the resulting different load distribution - can also have an outer ring with reduced thickness. In engineering terms, a track roller or support roller is therefore a rolling bearing reinforced on the outer ring.

Various applications of rollers

Rollers fundamentally allow movement. They can take on various tasks. Their main applications include:

• Equipment, e.g. apparatus rollers, drive technology, e.g. drive roller
• Material handling equipment, e.g. track rollers
• Drive technology, e.g. drive rollers, machine components, e.g. transport rollers for machines in heavy-duty applications

For example, apparatus rollers are used as devices to facilitate the transport of heavy equipment. For this purpose, they are bolted to the bottom of a transport cart or the equipment itself. Drive technology uses rollers to support the transfer of energy between various drive elements and thus influence rotational speed and velocity. Material handling equipment not only uses rollers for transport, but also for various other applications. Here, however, they are generally not permanently installed on the transported cargo but instead facilitate the flow of materials, e.g. on roller conveyors. Special-purpose conveyor belt deflection rollers guide conveyor belts in the right direction and stabilize movement.

For more information on material handling, see our article on Industrial Material Handling.

Materials for rollers

Which material is selected for a roller depends on which material or workpiece the roller will come into contact with. Basically, the following materials are used:

• Polyurethane (PU) / rubber
• Metal
• Resin
• High-performance plastics

Polyurethane and rubber rollers are used when sensitive materials and surfaces and handled, such as paper or thin sheet metal parts. High-performance plastics (e.g. polyamide, POM) are used in environments with special hygiene requirements. They have a smooth surface, which causes little friction, and do not react chemically. Metal rollers, on the other hand, are preferably used in environments with extreme temperatures, aggressive chemicals, or heavy mechanical loads where PU or rubber rollers would not hold up.

Details on high-performance plastics and their properties can be found in our article Special-purpose Plastics in Industry: properties, resistance, and application examples.

Different types of rollers

Rollers can be distinguished in terms of their geometry and the associated applications. The term track roller generally refers to an idling, i.e. non-driven, roller. However, with regard to their function and the associated structural design, practitioners distinguish these into track rollers, support rollers, deflection rollers and guide rollers, cam rollers and transport rollers.

Track rollers

In addition to various industrial applications, track rollers, also called support rollers, are essential components in chassis systems of heavy industrial vehicles such as crawler excavators and track vehicles. Here, track rollers provide a stable and mobile machine base while also absorbing shocks. Installed on the lower part of the undercarriage, they have direct contact with the moving chain while driving and thus supporting the weight of the machine on the floor.

However, a track roller is usually understood to be a bearing consisting of a single or multi-row ball bearing with a reinforced outer and inner ring. The reinforced outer ring forms the running surface of the track roller. This rolling surface can consist directly of the outer ring, or another material can be deposited to improve the running characteristics.

Advantages of track rollers include:

• high load-carrying capacity
• resistant
• optimized guidance and power transmission.

To learn more about track rollers or cam rollers and their uses, see our article Cam rollers and rollers followers: Basic knowledge and intended uses.

Cam rollers

Cam rollers are highly stable shaft bearings with a thick outer ring and a roller bearing cage with integrated needle rollers. The design with needle roller cage helps to increase the rotational power in order to be able to cope with high speeds. The outer ring is thicker than on normal rolling bearings to allow use at high shock loads or heavy loads.

The following table provides an overview of the various cam rollers:

Conveyor rollers

Conveyor rollers are used to transport, e.g. cargo. Roller conveyors, for example, usually use several rotating rollers arranged in parallel to transport objects. They are reliable, often withstand high loads, and are therefore also used in conveyor belts. Conveyor rollers also serve as drive shafts in belt-driven conveying systems. They generally consist of robust carbon tool steel or hardened tool steel, as they must be able to transfer torque loads. For applications with particularly high loads, they can be equipped with a chrome plating finish. A deflection roller with a ball bearing is one variant of a conveyer roller. Friction resistance is minimized by the ball bearing. Conveyor systems also use these as support rollers in roller conveyors to transport materials efficiently. Advantages of conveyor rollers include:

• low friction
• high load-carrying capacity
• various drive options, e.g. belts, motor
• efficient material transport.

Conveyor rollers are essential components of belt conveyors and roller conveyors. More about this in our article Belt conveyors in focus: Construction, conveying capacity and belt selection for optimized processes and wheel conveyors, roller conveyors, roller strips – construction, function and advantages.

Support rollers, roller followers, drum followers

Support rollers are highly stable bearings with a rolling bearing cage with needle-shaped rollers as rolling elements. The shaft-free design permits their use in a space-conserving manner. The design combines a thick outer and inner ring with needle-shaped roller bodies as used on cam rollers. Support rollers can be used in applications with acting forces or that require high speeds. The length of the pin for fastening the support roller can be configured so that the support rollers can be readily adjusted to the required installation situation. The following table provides an overview of various support rollers:

Like roller followers, support rollers, also called top rollers, fulfill a load-bearing or supporting function. Like all types of track rollers, support rollers are not driven. Support rollers, also called drum rollers, have no direct contact with the floor, but to the cargo to be supported or to the belt on which the object to be supported is transported.

Using the crawler excavator as an example, support rollers are installed in the upper part of the undercarriage system and are responsible for evenly guiding the chains of the crawler excavator and preventing them from sagging. On belt conveyors, they support the belt to prevent the belt from sagging under the weight of the conveyed material. Roller bearings are installed in roller conveyors as non-driven rollers and carry the weight of the objects to be transported.

Guide rollers

Guide rollers are used for precise steering and control. They ensure, for example, that a transported item remains in its specified lane. Guide rollers made of steel are often used in industry, as they can absorb particularly high loads. Ball-bearing guide rollers ensure smooth transport and enable adaptation to the object to be guided using various groove profiles and shapes.

Guide rollers are available with different grooves that ensure optimal grip and reliable guidance. For example, there are U-groove profiles for round rails, V-groove profiles for triangular rails and H-groove profiles for rectangular rails.

The advantages of guide rollers include:

• precise guidance
• high stability
• different groove profiles
• reduced wear.

For information on profile rail guides, read our article Profile rail guides: Types, function, service life, maintenance, alternatives.

Ball rollers

Ball rollers are a special type of roller bearings, the special feature of which is high-speed movements in any direction and plane. Their main application is material handling.

The housing of ball rollers often consists of steel or steel plate. A ball bed filled with support balls is integrated in the interior of the housing. A load-bearing ball is placed on the support balls as a roller element. This permits low-friction movement. Ball rollers can also withstand high loads. Advantages of ball rollers are:

• low noise
• smooth operation
• can absorb high loads
• low dead weight
• easy mounting
• long service life.

Swivel castors, appliance castors, fixed castors

Swivel castors are used for directional control.

Turntables, which permit 360-degree rotation, are often installed for ease of movement. Swivel castors, appliance castors and fixed castors can be found in many transport applications. These range from bolting onto transport boxes for better movement to heavy-duty swivel castors for heavy loads in industrial environments. Unlike swivel castors, fixed castors are rigid and thus increase stability of linear movements. A combination of both ensures that even large and heavy equipment can be moved safely and responsively. The advantages of swivel castors include:

• high maneuverability
• simple directional control
• minimal physical effort.

Find more detailed information on the subject of swivel castors and fixed castors and what to pay attention to when selecting them in our article "7 Steps for Selecting a Swivel Castor".