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A Comprehensive Overview of Calendering Machine Basics

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2023-05-11 14:34

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In plastic machinery, calenders are typically integrated with primary equipment for material conveying, screening, metering, kneading, and shaping, as well as downstream units for web take‑off, stretching, embossing, cooling, thickness measurement, winding, and cutting, along with drive, monitoring, and heating systems, to form a complete calendering production line that manufactures rigid and flexible films, thin films, leather, wallpaper, and floor‑covering products.

Working principle of a calender:

1. Relative rotation—two adjacent rollers rotate relative to each other at a specified speed ratio or at a constant speed;

2. Under the action of friction, the rubber material is drawn into the roll gap.

3. As the cross-sectional area of the roll gap gradually decreases, the rubber compound undergoes intense compression and shear, enabling it to be stretched and shaped—whether by calendering into sheets or by extruding the compound onto steel‑cord fabric—for applications such as double-sided adhesive coating, embossing and profiling of the rubber blank surface, and laminating multiple layers of rubber sheets.

Calender Maintenance and Servicing:

1. Regularly inspect the system’s transmission components and ensure that the control oil lines remain unobstructed.

2. Pay attention to the roller bearings and seals; if necessary, remove the lower pressure cover and replace the oil-resistant rubber hose. If severe air leakage occurs at the working water head, disassemble the water head and replace the sealing ring.

3. Under normal operating conditions, the equipment shall undergo maintenance every two years, during which the wear condition of all components is inspected and worn parts are replaced. Following maintenance, installation must be carried out to ensure compliance with installation quality standards.

4. After the machine has operated for 2,000 hours, it should be cleaned and the lubricating oil replaced. The internal lubricant in the reducer shall be Grade 220 gear oil. The reducer should be cleaned annually, and the lubricating oil should be changed once per year, regardless of the operating cycle.

5. The lubricating oil for the calender’s main drive gears is No. 100 machine oil, with the oil pressure typically set at 0.1–0.2 MPa. Monitor the oil level in the reservoir to ensure the lubrication system operates properly.

6. After the calender has been in continuous operation for 300–600 hours, the lubricating oil in the reducer and the oil collection tank should be drained, the components cleaned with kerosene, and then refilled with fresh lubricant.

7. At the end of each shift, turn off the main power supply to the distribution cabinet, wipe down the machine, clean the work area, and maintain a tidy environment.

A calender consists of two or more rollers arranged in a specific configuration; under controlled temperatures, it presses rubber or plastic into films of specified thickness and shape, and can also apply adhesive to fiber‑reinforced or steel‑cord fabrics.

Do you know the advantages of a calender in operation?

1. High-quality plastic sheets are produced on calendering machines; in fact, calenders excel at extrusion and are particularly well suited for processing heat-sensitive polymers, as they rarely induce thermal degradation.

2. Calendering also offers the advantage of thoroughly blending polymers containing substantial solid additives, and the high mechanical energy generated by the calender results in a rapid melt rate, enabling the incorporation of greater amounts of fillers into the plastic—thereby reducing raw material costs.

3. The calender is a highly versatile machine, featuring three feed axes, each equipped with an electromagnetic powder tension controller and a wedge‑type pneumatic shaft, fully meeting the requirements for thick materials such as PET, intermediate glass fiber, and sponge.

Calender machine

Related Information

A Comprehensive Overview of Calendering Machine Basics

In plastic machinery, calenders are typically integrated with key equipment such as material conveyors, screening units, measuring devices, kneaders, and molding machines.

An Introduction to Calendering Machines

Calendering machines are classified according to the number of rolls into two-roll, three-roll, four-roll, and five-roll calenders. Based on the arrangement of the rolls, they can be further categorized into L‑type, T‑type, F‑type, Z‑type, and S‑type configurations. A standard calender typically comprises roll cylinders, a frame, a roll gap adjustment mechanism, a roll temperature control system, a drive transmission assembly, a lubrication management system, a control information system, and a roll‑removal device. In addition to these core components, precision calenders incorporate advanced features—such as pressure‑holding systems and bearing clearance‑adjustment mechanisms—to ensure high‑precision calendering operations. Key characteristics of calendering machines: 1. The design is simple and streamlined, with straightforward, user‑friendly operation. 2. A wide range of speeds and speed ratios are available, enabling adaptation to various formulations and processing requirements. 3. Both the frame and base are welded structures; after stress‑relief treatment, they undergo annealing for an aesthetically pleasing finish. 4. The gearbox achieves Class 6 accuracy, featuring hardened gear surfaces that are ground and finished, resulting in long service life and low noise levels. 5. Comprehensive emergency stop provisions are provided, maximizing safety for operators and equipment. 6. A specially designed sealing system effectively prevents oil leakage. 7. Rolling bearings are employed throughout the machine. 8. The rolls are made from alloy cold‑hard cast iron (LTG‑H), equipped with swivel joints and finished with a polished surface.

A Comprehensive Overview of Calendering Machine Basics

In plastic machinery, calenders are typically integrated with upstream equipment such as material conveyors, screening units, metering systems, kneaders, and molding machines, as well as downstream processes including take‑up, stretching, embossing, cooling, thickness gauging, winding, and cutting. Together with drive, monitoring, and heating systems, these components form a complete calendering production line, used to manufacture rigid and flexible films, thin films, leather‑like materials, wallpaper, and floor‑covering products.

One-minute overview of precautions when using a calender.

A calender consists of two or more rollers arranged in a specific sequence according to the heating method and is classified into cold‑calendering and hot‑calendering. Cold‑calendering is suitable for materials that do not require heating, such as graphite films, graphite sheets, radar‑absorbing materials, shielding materials, magnetic materials, and non‑ferrous metal materials. Hot‑calendering employs methods like steam heating, electric heating, oil heating, and electromagnetic heating. This equipment presses and coats rubber, silicone, silicone rubber, phase‑change materials, polytetrafluoroethylene, or plastics at a specified temperature to produce films of a defined thickness and surface profile, and it can also bond fibrous fabrics, canvas, or steel cord fabric.

Some key points about hot rolling mills

Rolling mill manufacturers note that in spunmelt nonwoven production lines, the fiber web formed consists primarily of fibers overlapping within the plane, with very weak bonding in the vertical direction. As a result, the web can hardly withstand external forces from any direction and thus lacks practical applicability. Therefore, appropriate web consolidation techniques are required to enhance inter-fiber bonding, transforming the web into a nonwoven fabric with adequate longitudinal (MD) and cross‑directional (CD) strength. A hot‑rolling machine leverages the thermoplastic properties of fibers: under the combined action of high‑temperature heat from the press rolls and the high pressure generated between the two rolls, the fiber web deforms, melts, and bonds at the embossing points, thereby consolidating the loose web into a nonwoven fabric with specified mechanical strength. As an indispensable piece of equipment in spinning and meltblowing lines, the hot‑rolling machine requires the following routine management procedures: 1. During operation, personnel must not enter the space connecting the hot‑rolling machine to the web‑forming table; entry into the protective guard at the drive end for inspection is also prohibited. Touching safety devices is strictly forbidden to avoid triggering shutdowns. Additionally, do not touch the two heating rolls with your hands to prevent pinching or burns. 2. When the oil furnace is being heated, the hot‑rolling machine must be started, and the rolls should be kept separated to prevent thermal deformation. 3. Once the oil furnace reaches the set temperature, the hot‑rolling machine may only be put into service if no alarms are present.

What are the characteristics of a hot rolling mill?

A hot rolling mill primarily consists of rolls, a drive system, a linear pressure‑adjustment mechanism, a roll‑deflection compensation mechanism, a heating system, a hydraulic system, a cooling system, a lubrication system, a frame, and a control system. The rolls are the principal components of a hot rolling mill. Each mill must have at least one pair of rolls: a patterned roll (commonly referred to as a “pattern roll”) and a smooth roll. The rolls are manufactured from heat‑resistant alloy steel. In most two‑roll hot rolling mills, the pattern roll is typically mounted on the wall plate above it, while the smooth roll is positioned below; the smooth roll is supported by two hydraulic cylinders. Under hydraulic control, the smooth roll can be raised, pressed against the pattern roll, or separated from it. The drive system of a hot rolling mill provides the power required to rotate the rolls and includes an electric motor, a reducer, and a universal joint shaft, among other components. The motor and reducer are usually fixed to the mill frame. Due to space constraints and the need for the lower roll to move vertically, a universal joint shaft—capable of compensating for axial misalignment and changes in center distance—is employed between the reducer’s output shaft and the rolls to transmit torque. According to hot rolling mill manufacturers, line pressure is defined as the force per unit length acting across the effective working width of the rolls, with the commonly used unit being N/mm. The line‑pressure adjustment mechanism is used to regulate line pressure according to process requirements, typically by adjusting the hydraulic oil pressure in the support cylinders of the lower roll. The operating line pressure is mainly related to…

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