Obscure rubber rollers are mostly used for very specific projects. These include: live shaft rollers, dead shaft rollers, cleaning rollers, spreader rollers and stinger rollers. Live shaft rollers are designed to withstand difficult environments and high load quantities; they have external bearings in which both the roller shaft and the roller rotate. Dissimilarly, dead shaft rollers have internal bearings located at the same place as a spinning roller that spins around a stationary shaft.
Cleaning rollers are used to remove dirt, dust and other contaminants from different surfaces. They are highly specialized to each surface they clean. Spreader rollers, frequently machined with specialized groove designs, like herringbone, spiral, circumferential and lateral-fluted, are commonly used for webs spreading machinery and other spreading applications. In the case of web spreading machinery, spreader rollers stretch and spread the web to prevent and fix wrinkles. Stinger rollers, finally, are configured very much like dead shaft rollers, but they are designed specifically for marine applications.
Rubber rollers are usually manufactured via casting or molding, but they may also made through extrusion. Casting processes are utilized only with rubber rollers that have metallic cores. In this case, cores are formed through a metal casting process like stamping, after which they are bound to a rubber coating. Binding is carried out using a bonding agent that usually made of polymer-solvent solutions, a primer coat based on phenolic-style resins and a top layer of mixed polymers and other various materials. Rubber roller molding processes include compression molding and injection molding; these are used for solid rollers. To extrude rubber rollers, manufacturers heat chosen elastomeric material(s), and squeeze the molten material through a die that has a pin in the center to fabricate the hollow tube.
The reason that rubber is such a popular material for making rollers and assisting object movement is that it can be repeatedly compressed and relaxed without losing its shape. A material that could not hold its shape, which would need constant replacing, would be virtually useless. Rubber is also fairly inexpensive to extract and manipulate. The elastomeric materials from which manufacturers can choose from is fairly varied. Each material has its own strengths and weaknesses, but all of them have some level of resistance to water, wear, certain chemicals and heat extremes.
Among the many, a few materials that are frequently used to fabricate rubber rollers include: EPDM, silicone, nitrile, neoprene, polyurethane and natural rubber. Metal core rollers are usually made with steel, stainless steel, aluminum or another metal that fits application requirements. A consumer may order rubber rolls to meet unique diameter and length specifications, and they may order them in a variety of thicknesses and colors.
Rubber Roll Manufacturing Process Explained
Rubber rolls are an important functioning component in a number of machineries, from printing to laminating. However, rubber rolls are primarily used in conveyor belts to help move things since rubber has a high coefficient of friction that makes them apt candidate for covering rolls.
Whether is it a warehouse, packaging, or equipment processing facility, all use conveyor rubber rolls for transferring products over a conveyor belt. Rubber rolls are of various types, including drive rollers, urethane rollers, conveyor rollers, industrial rollers, laminating rollers, and ink rollers.
Rubber rolls manufacturing process:
Standard rubber manufacturing involves a rubber fabrication step, which can be achieved either by plying method, extrusion, casting, or die press. In the plying method, calendered sheets are rolled over a core, and in extrusion, rubber is forced through a die to give shape. Alternatively, in the casting method, rubber is injected into a mould and cured by heat. The die press method involves a die to give shape and press by pressure and heat cures the rubber.
After the rubber-fabricating step is done, the next step is bonding the rubber and the core together to make a rubber roll. However, before bonding step, the core goes through a number of steps. When a rubber roll gets old, it is sent back to a rubber roll manufacturing unit, where it is recycled and its core is covered with different types of rubber, based on an application.
The first step in recycling removing rubber from the roll, then if grooves on a core are deemed suitable for the further process, then the cores are sand blasted—a process of cleaning surface with the help of a jet of sand. When a new core is used, it also goes though a blasting stage. After blasting, the next step is bonding, which is done by two methods. In the most common method, adhesive agent is used to glue rubber and core together. The alternative method involves use of ebonite, a type of very hard rubber. Ebonite method is not used normally and is considered for bonding when solvents used can damage the adhesive agent or when the core is not in good condition. Both adhesive agents and ebonite show high adhesion strength and stability under testing. However, adhesive agents work better when temperature, ranging 100 to 150 F, is involved in an application.
The next step involves surface grooving. There are a number of grooves that can be created on a surface of rubber, including square, trapezoidal, “V”, double edge saw, half circle, and round. Moreover, on a rubber roll, these grooves can be made vertically, horizontally, helically, worm, diamond cut groove and screw threaded.
The grooves have some specific purposes, including:
For increasing the amount of coating
For smoothening wrinkles out from a paper or plastic film
Preventing belts from slipping in a conveyor system
Grooves are also used for embossing surfaces
Some grooves help to release heat created by friction
Adding texture to rubber rolls.
At the end of this step, the products are inspected for aberration.
Tips on Extending the Operating Life of Rubber Rolls
Rubber rollers are a staple component in a range of equipment, where they are used for guiding, squeezing, laminating, and spreading. Different industries have their own rubber rolls, such as drive rollers, urethane rollers, conveyor rollers, laminating rollers, and ink rollers.
Rubber rolls, just like every other component, has its limits and should be used as per the instructions.
Here, we are dispensing some advices regarding rubber rolls use, and how they should be used to extend their life.
A typical rubber roller has the maximum load capacity of 100 kilogram-force centimeter (kgf/cm) when force is exerted linearly. Although, the load capacity of a roll varies with the rubber hardness, materials, and the rotation speed, as well as thickness of rubber, the temperature range, type of the core, and construction. Therefore, it is recommended to check the rubber roller load capacity while installing them.
If needed, a roller with greater load capacity of 100 kgf/cm can be designed, therefore, ask your manufacturer if your requirement falls in this range.
If a roller is exposed to high speeds with large loads, it is recommended to buy rubber rolls with a core that can be water cooled. When rubber is nipped, it releases heat—called hysteresis heat—and water cooling is an effective way to contain that heat.
High temperature is an enemy of rubber, regardless of the rubber used for making rolls. Therefore, it is best to avoid rapid heating while using rubber rolls. There is other reason why rapid heating must be avoided, as the adhesive, used for bonding rubber and the core together, usually has low heat resistance, even lower than the rubber, which with the development of new types of polymer has become quite heat resistant.
If an application demands work under high temperature, it is recommended that the rollers are water cooled so that the temperature remains under operating range.
Rubber does not show much resistant to chemicals; therefore, if an application involves use of chemicals, it is better to inform the manufacturer or the supplier about it before making the buying decision. The manufacturer then can provide you with the alternatives that can be used for making rubber rollers.
Other factors that affect the function of rubber rollers
The life of a rubber roll can be drastically cut short, if it is installed on a worn-out ball bearing and misaligned along an axis. The other factors include over loading and faulty gear. Therefore, it is recommended that all these parts be taken care of during maintenance checks. Moreover, an unbalanced roller and a deflected roller can affect the functioning of an equipment, therefore, replacing them is a best option.
These are tips regarding the operation of rubber rolls; however, inappropriate storing of rollers too can damage them. Therefore, while storing a rubber roll, you must hold at the shafts and stand them upright, so the rubber part does get exposed to other materials. Moreover, since rubber can be damaged by UV light, it is recommended to stored roller in a cool and dark place.
How Rubber is Fabricated for Rubber Rolls
Rubber rolls, as the name suggests, are rollers that have a rubber outer covering and the core, based on the application, is made metal and other materials. Rubber rollers have an array of applications, ranging from conveyor belt components to lamination, to rotary screen-printing machinery and automotive rubber components. The common products include drive rollers, urethane rollers, conveyor rollers, industrial rollers, laminating rollers, and ink rollers.
Rubber rollers have become a staple in many industries for a number of reasons:
Unlike metal rollers used in conveyor system, rubber rolls have high coefficient of friction, which provide great traction in moving parts and components.
Since rollers have rubber covering, rollers are flexible and can accommodate distortion in shape.
If rollers encounter load variation, rollers can absorb shocks.
Different types of rubber can be used to make rollers inert against chemicals based on an application.
Rubber handles a range of products while preventing damage and scratching.
Rollers can compensate for small changes emerging from machine functions.
Since rubber rollers are used in a range of industries, different types of fabricating methods are available.
The plying method involves calendering process, where to make calendered rubber sheeting, rubber is passed through a combination of rollers. As the rubber moves through the rollers, it is smoothened and flattened. By this process, two types of polymer can be sandwiched together, if an application demands. Once the calendered sheet is ready, the sheet is covered onto an iron core or other cores to make rubber rollers. Based on the requirements, sheets can polished, glazed or embossed.
Extrusion is the most common manufacturing method that involves an extruder. With this method, a rubber profile of fixed cross-sectional can be made continuously by passing rubber through a die. In this process, raw material is heated by passing it through a screw mechanism, which heats material by a combined action of pressure and temperature, and then the material is pushed through the die. The critical step in this fabricating technique is curing, which involves conditioning the rubber product in a controlled environment where it is exposed predetermined temperature and pressure. The curing process gives the structural strength to a rubber product by removing porosity.
This method commonly involves a hydraulic press and a die. The die gives the shape to the raw rubber, whereas press provides pressure and heat to cure the rubber product. The process begins by filling raw rubber into a metal mold, and then a hydraulic arm fitted with a die presses the mold and provides heat and pressure. Unlike extrusion, the press method is not continuous, thus is not as efficient as extrusion.
Casting, inarguably, is the oldest way of giving shape to a range of materials. From automobile engines to high-end sculptures, have been crafted by this method. Whatever the material is, all is molded by a same principle, which involves pouring of raw material in a mold and then exposing it to an oven for a period of time that cures it and set it in a predefined shape.