This article provides all that you need to know about tape and label cores and how they are used.
You will learn:
A tape and label core is a robust, cylindrical structure situated at the center of a roll of tape or labels. It resembles the core of a toilet paper or paper towel roll but is designed to be more durable and resilient. Despite their similar shapes, tape and label cores differ in their strength, dimensions, materials, and thickness, with thicker cores used for more substantial types of tapes and labels.
When examining tape and label cores, it's important to consider the core size, which refers to the inner diameter (ID) of the core. The overall diameter, including the core and the tape or label, is known as the outer diameter (OD). Additionally, it's crucial to specify the winding direction when ordering, as there are eight possible directions to choose from.
The rewind directions are categorized based on the placement of the labels, which can either be on the exterior or interior of the roll. There are four rewind options for labels placed on the outside and four for labels on the inside, each with a unique winding direction. Among the eight possible winding directions, options 5 and 8 are rarely used, whereas options 3 and 4 are quite common and widely preferred.
Tape and label cores come in various forms, each depending on the materials used in their production. Traditionally, these cores are made from tightly wound paper, formed on a mandrel and adhered with glue. Kraft paper is the most commonly used material for these traditional paper cores.
Paper cores are the industry standard and are utilized in many applications. However, plastic cores are preferred when there's a risk of contamination from paper core dust. Plastic cores can be made from materials such as high-impact polystyrene (HIPS), high-density polyethylene (HDPE), polypropylene, polyvinyl chloride (PVC), and acrylonitrile butadiene styrene (ABS).
The manufacturing process for tape and label cores is similar to that of other core types, with the primary difference being their size. Although tape and label cores are designed to be as strong and durable as those used in more demanding applications, they are typically measured in inches and millimeters rather than feet and meters.
The choice of core depends on its intended application, which varies between consumer products and industrial uses. Cores for tapes and labels must be robust enough to support the weight of the materials and withstand the winding process. The material type and wall thickness, whether plastic or paper, determine their durability.
It's important to distinguish between tubes and cores. Tubes are used for storing and shipping items such as maps, blueprints, or long, thin products. In contrast, cores are designed for holding materials like tape, labels, or fabrics. While tubes are designed to protect their contents, they lack the structural strength of tape and label cores, which are thicker and more resilient.
Tape and label cores are made of plastic or paper depending on the type of winding. Plastic is used for sturdy, heavier, and stronger wound materials, while paper cores can be used for the same types of materials if they are wound very thick. In most cases, paper wound cores are used with light to medium tape and labels. There is a great deal of difference between how paper and plastic cores are made due to the radical difference between the materials.
Paper cores are cardboard tubes that are spiral wound in layers of one, two, or more plies. The liner, or inner most layer, and the wrap, the outermost layer, are made of various types of special paper. The types of paper vary and include recycled paper, paper and adhesive composites, cardboard, kraft paper, waterproof cardboard, or fiberboard.
The production of paper cores starts with cutting strips of paper or cardboard into narrow ribbons. These ribbons, or plies, can vary in width from a few inches (about 50 mm) to as wide as 10 or 20 inches (approximately 254 mm to 508 mm). Their thickness typically ranges from 0.008 inch to 0.050 inch (about 0.20 mm to 1.3 mm).
The paper strips are passed through a container that applies adhesive to bond the layers together securely. Different manufacturers use various types of glue, which fill the gaps between the layers with a penetration depth of less than 20 microns (µ). The adhesive's tackiness affects the speed at which the machines can assemble the layers. The overall strength of the core relies on factors such as the adhesive's bonding capability, the core's thickness, the degree of overlap, and the adhesive's durability.
The mandrel is a long metal tube used to wind the paper plies. The number of layers wound onto the mandrel can range from 1 to over 50, though 3 to 30 layers are most common. Modern mandrels come in various designs, including those that can expand or contract to adjust the core's inner diameter. For successful core formation, the mandrel must operate smoothly, rotating steadily to ensure even bonding of the layers by the adhesive. A strap or belt powers the mandrel's rotation and controls the angle at which the ribbons are fed. The heat generated from rotation and movement helps the glue to dry and set.
During the initial winding process, the ribbons or plies form long tubes that define the core's inner diameter and thickness. After the adhesive has dried and hardened, the long tube is removed from the mandrel and then cut to the required width to produce the final core.
There are several techniques for cutting cores, all of which involve the use of a circular saw. The cutting process can be performed either manually or through automation. In high-volume core production, an automated system is typically employed. This system positions the long tube on a rotating mandrel while a saw or knife slices the tube into cores of the specified width. Given the wide range of core widths, automated machinery is programmed to achieve precise cuts according to the desired dimensions.
Plastic cores are made from materials such as high-density polyethylene (HDPE), polypropylene (PP), acrylonitrile butadiene styrene (ABS), polyvinyl chloride (PVC), and recycled plastics. Each type of plastic offers distinct advantages, with strength and durability being the primary features of these materials.
Similar to paper cores, plastic cores are available in various wall thicknesses and sizes, ranging from half an inch to three inches in diameter. Beyond their use in tape core production, plastic cores are employed in a wide range of applications. The durability and strength of different plastics make them highly versatile for numerous other uses.
Extrusion is a technique used to manufacture plastic tape and label cores. This process involves heating plastic pellets, granules, flakes, or powders and forcing the molten plastic through a circular die. The plastics used are derived from petroleum, which is refined and processed to create resin pellets.
The diameter of a plastic core is determined by the inner diameter of the die, while the wall thickness is influenced by the die's shape. The molten plastic is pushed through the die by a screw mechanism that moves it along the heated barrel of the extruder.
As the extruded tubes emerge from the die, they are cut into various lengths and allowed to cool. During cooling, the tubes solidify into their final shape. The extrusion process is carefully controlled to ensure that the tubing meets the precise dimensions required for the plastic cores.
Cutting plastic cores necessitates more robust cutting equipment due to the strength and density of the plastic materials. Similar to paper core cutting, the process can be carried out using either manual or automated methods. The manual approach involves using a circular saw, much like the technique used for paper cores. In the automated process, rollers hold the plastic tube in place and rotate it while a circular cutter slices the core to the required dimensions.
Once completed, the cores are sold to tape and label manufacturers for use in rewinding their products. Various types of rewinding machines are available, each capable of using either plastic or paper cores. For effective rewinding, the width of the core must precisely match the width of the tape or labels. Rewinding machines ensure that the tape or labels are wound correctly and aligned properly on the cores.
The wall thickness of a tape and label core is crucial for determining its strength and durability. The required thickness depends on the material being wound and its weight. Cores used for heavy-duty tape and labels must be robust enough to retain their shape under various conditions. Wall thickness is a key dimension that affects both the inner diameter (ID) and outer diameter (OD) of the core.
For paper cores, the typical wall thickness is 0.125 inch (3.2 mm). In contrast, plastic cores have wall thicknesses set during the extrusion process, ranging from 0.024 inch up to 2 or 3 inches (0.61 mm to 50.8 mm or 76.2 mm). Paper core wall thickness can be adjusted by altering the number of paper ribbons or layers used in the core.
Paper cores are designed with thicker and more durable walls to endure the stresses encountered during the winding process. The wall thickness varies based on the width and diameter of the tape or labels being wound.
Due to their affordability and widespread availability, paper tape and label cores are among the most frequently utilized types of cores. The primary distinction lies in their winding method, with all windings forming cylindrical shapes composed of multiple layers of tightly wrapped paper. The two predominant forms of paper cores are spiral and convolute.
Convolute, or parallel, cores are crafted from a single sheet of cardboard, where the left edge is rolled over the right edge and adhered as the rolling occurs. Unlike ribbon-wound paper, convolute tubes are made from a continuous sheet, resulting in the paper edge being parallel to the tube's axis.
The design of convolute cores provides them with enhanced beam strength, making them suitable for more rigorous tape and label applications. As they are constructed from a single layer of paper, convolute tubes typically have a slightly lower cost than spiral-wound cores. These tubes are generally lightweight and easy to handle but are restricted in the variety of available sizes.
Spiral cores are manufactured by winding ribbons of paper at an angle on a mandrel to form a continuous spiral. The paper for spiral cores is thinner than that used for convolute cores and is made from kraft paper, recycled paper, or certain forms of coated papers. As each layer is applied, it is glued with a high strength industrial adhesive that securely holds the ribbons of paper and provides a smooth even surface.
The spiral core manufacturing process results in a highly smooth surface that is resistant to unraveling or separating. The multiple layers involved in spiral cores give them added strength, durability, and resistance to crushing, allowing them to support heavy loads. In contrast to convolute paper cores, spiral cores are available in a broad range of sizes, from those used in toilet paper rolls to those designed for holding duct tape.
Thermal tape cores, which can be made from either plastic or paper, are designed to hold delicate paper coated with a chemical that changes color when exposed to heat. These specialized cores for thermal tape typically have an inner diameter of 13 mm and 25 mm (0.5 in and 0.98 in) with a wall thickness of 3 mm (0.12 in).
Plastic cores, being extruded, are produced with fixed dimensions. They can be either solid or honeycomb-structured and are available in various colors, such as white, black, green, and blue.
Kraft paper is commonly used in the production of paper cores because of its outstanding strength, durability, and sturdiness. Unlike other types of paper, kraft paper is unbleached, which allows it to retain its structural integrity. Made from wood chips or recycled paper, kraft paper is supplied in large rolls that are cut to the required size and shape for making tape and label cores.
The term "kraft" is derived from the German word meaning strength, force, resistance, and power, aptly describing the paper's superior qualities. The key components for producing kraft pulp include wood fiber, water, chemicals, and heat. The process starts with the cooking of wood chips.
The production of kraft paper starts with the steaming, heating, and cooking of wood chips in pressurized containers called digesters, using a solution known as white liquor. During this cooking process, the tough wood chips are converted into pulp, which is treated with chemicals to enhance its strength and flexibility. In the pre-steaming phase, the wood chips are moistened and heated with steam, allowing water and air to fill the cavities within the chips.
Inside the digester, the wood chips enter at temperatures below 100°C (212°F) and are then cooked at temperatures ranging from 170°C to 176°C (338°F to 349°F) for several hours. The combined liquids, referred to as black liquor, contain lignin fragments, carbohydrates resulting from the breakdown of cellulose, and a mixture of sodium carbonate, sodium sulfate, and other inorganic salts.
Wood chips are composed of two primary structural components: lignin and cellulose. During the kraft paper manufacturing process, it is essential to separate the cellulose from the lignin, as cellulose is the key ingredient in kraft paper production. The chips transition from the pre-steaming stage to the cooking stage within the digester, which may be either vertical or horizontal.
During the recovery process, the pulp undergoes washing and screening. The weak black liquor, which is a mixture of lignin and other substances, is passed through evaporators until its concentration reaches 65%. This concentrated black liquor, rich in energy, is then burned in a furnace.
The wood chips are discharged into a collection tank at atmospheric pressure, releasing steam and volatile compounds that are subsequently condensed and collected. As the chips enter the blow tank, their fibers are separated and broken open.
During the washing and cleaning stage, the kraft pulp is subjected to various processes to remove black lignin and other impurities. Waste liquids are also removed through high-temperature and high-concentration methods. Pulp washing can be performed using single-stage or multi-stage approaches.
The effectiveness of pulp washing depends on factors such as cooking methods, fiber materials, pulp hardness, temperature, pressure, and the degree of vacuum applied. The process is carried out using different types of equipment, including vacuum drums, twin roll presses, single screw presses, disc filters, and gravity disc thickeners.
During the screening process, screens are used to remove larger pieces of shives, knots, dirt, and debris. These screens are arranged in stages to create a cascade effect. This process separates the brown pulp from contaminants, resulting in clean kraft pulp. The separation is achieved through centrifugal forces that push the pulp against the walls of the pressure screener.
The color of kraft pulp is attributed to residual lignin, which is removed during the bleaching process to enhance the pulp's physical and chemical properties. This process involves the use of bleaching agents and can be carried out through reductive or oxidative methods. Equipment used in bleaching includes screw conveyors, drum washers, roll mixers, pulp chloridizers, and bleaching towers. Kraft paper undergoes less intense bleaching compared to other papers because excessive bleaching can weaken the pulp fibers.
The pulp and water mixture is spread over a large mesh screen, where most of the water is drained using gravity, suction, and vibration. In the press section, additional water is removed as the pulp mixture is squeezed between cloth-covered cylinders called wet felts. This is followed by the drying section, where steam is used to reduce the moisture content of the pulp to between 2% and 6%.
During the size press process, a starch solution is applied to the kraft paper to improve its strength. In the calendar stack, the paper is pressed to achieve a smooth finish. The finished paper is then wound onto a reel by a winder. Once the reel is formed, it is cut to appropriate sizes for shipping.
Cores used in the production of tape and labels are supplied to manufacturers of these products. The type of core employed varies depending on whether the tape is clear, colored, heavy-duty, or the specific type of label being produced. For tape, the process starts with a large roll of material that goes through several stages, including the application of adhesive, before being wound onto a core.
There are also variations in how cores are utilized during tape production. After cores are formed into tubes, they are cut to the width required for the tape being produced. In some manufacturing setups, cores are delivered as uncut tubes, and the tape material is applied to these long tubes before being cut to the desired width.
When using individual cores, the tape material undergoes several processes to improve its strength, usability, and alignment on the core. After these steps, slicers cut the tape into the specified roll widths. The tape bands are then wound around either plastic or paper cores. The length of tape applied is determined by the roll's design and specifications. Once the rolls are finished, they are ejected, and a new set of cores is prepared for the next batch.
In tape manufacturing that uses a tube as the core, the process resembles that of using a mandrel, where the material is wound around the tube after undergoing various quality assurance steps. The final stage is similar to the production of individual cores, where the long tube is cut to match the dimensions and width of the tape.
The production of labels follows a process similar to tape manufacturing, with key differences in label placement, printing, and types. Blank labels are die-cut and wound onto a core, while printed labels are applied to the material before being placed on the core.
When placing labels on a core, it's important to specify their winding direction, which can be set to one of eight possible rewind positions. The choice of rewinding method depends on how the labels will be removed from the core and whether the labels are wound out or wound in. The most common rewinding method, where labels are attached to the outside of the core, is typically found in rewind positions 1 through 4.
The rewinding position is determined during the manufacturing process when the roll of labels is mounted onto the core.
While tape and label cores are commonly known by these names, they are utilized in diverse applications for winding and rewinding different materials. The intended use of a core significantly influences its manufacturing process. This distinction is particularly evident when comparing cores used for paper towels with those used for duct tape.
Electrical tape cores are constructed from plastic to endure the specific conditions and environments in which the tape is applied. These plastic cores must be resistant to solvents and chemicals to ensure durability.
Price label cores are loaded into printing machines and are engineered to rotate and dispense labels during the printing process. Given the demands of label printing, these cores are built to be more robust and durable than other types. They are designed to support the weight of the labels, which are often heavier than materials used in other core applications.
Cash register tape comes in various forms, including carbonless two or three-ply rolls. The cores for cash register tape can be made of plastic or paper, depending on the type of cash register. These tapes are available in a range of widths, tailored to fit different cash registers. A crucial consideration for cash register tape cores is their ease of shipping and insertion into the cash register.
Gaffer tape is known for its high durability and versatility, available in a range of core sizes from one inch to four inches wide. Unlike many other types of tape, gaffer tape is constructed from heavy cotton cloth with a pressure-sensitive adhesive that is exceptionally strong. Due to its use in demanding applications, the core of gaffer tape must be robust enough to support the tape's weight and withstand the impact it endures during use.
Most equipment used for manufacturing tape and label cores is produced internationally, with China being the leading supplier.
The JT-50A is capable of producing cores with 2 to 24 layers with core diameters of 30 mm up to 250 mm. It comes equipped with an Emerson PLC and touch screen with all of the parameters of the core displayed on the monitor. Once the data has been input, the machine starts automatically using a frequency inverter for AC motor control. The unwinding angle is adjustable with a compact spacing structure. The JT-50A has an automatic glue spread with a glue recycle system and glue contained in a stainless steel tank. Single and double side coating is available.
The PTA-4120 is equipped with a PLC logic control system and a touch screen interface, along with a high-torque vector speed converter. It features photoelectric length positioning control that adjusts cutting speed automatically for enhanced accuracy. The modular design of the PTA-4120 simplifies maintenance and repair. Additionally, the PTA-4120 is noted for its low noise level during operation.
The KJT-4D core winding machine can produce cores with diameters ranging from 25 mm to 250 mm and wall thicknesses up to 15 mm. It utilizes a wax-based lubricant to manage friction between the paper core and the central shaft, facilitating more stable and precise control of the spiral gap. This feature enhances core quality and eliminates issues with oil stains. The machine's driving mechanism supports the production of thick-walled cores and offers adjustable winding speeds.
The Crown Spiral Core Machine is designed to produce custom cores tailored to specific design parameters, including various wall thicknesses, diameters, and lengths. It supports both inside and outside label wrapping with a specialized unwind reel splicing mechanism for continuous, stable production. The glue applicator features a tension adjuster and precise glue metering to ensure a consistent flow. Additionally, the belt reel on the Crown Spiral Core Machine delivers high-quality finished cores, and the servo motor-driven cutter system provides precise cutting.
The UBR Paper Core Making Machine is capable of producing cores with 5 to 30 plies, featuring sliced paper reels positioned on the top, middle, and bottom transfer rollers. It includes a paper lifting system with a small hoist. Each sliced paper reel is individually glued, with each gluing unit equipped with a pneumatic tension compressor to ensure tight unwinding. The machine's main drive utilizes a radial piston pump for energy-efficient pressure flow control. The pitch angle of the unwinding process can be easily adjusted either manually or remotely. Like other paper core machines, the UBR model is powered by a servo motor, enabling flexible changing rates and high cycle times.
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