Paper tubes consist of paper or paperboard sheet layers wound together to form strong, hollow and usually cylindrical shapes. The paper layers are laminated or bonded together using adhesives. The wall thickness of the tube can vary depending on the number of layers wrapping/ wrapped during manufacturing.
Paper tubes are also known as paper cores, paper board tubes, paper cans, fiber drums, fiber tubes, paper tubing, wound tubes, composite cans, core board tubes and cardboard tubes. While widely used everywhere, the term “cardboard tube” is a misnomer. Cardboard consists of three craft layers with the central layer corrugated.
Paper Tubes Types and Shapes
Paper Tube and Core Types
While paper tubes, paper cores and related products are all made from wound piles of paper or paper board, Paper tube or cores can be constructed from one, two or many piles of brown craft paper or paperboard.
The innocent layer or ply, the liner and the outermost layer, the wrap can consist of different materials (foil, film etc.) or specialized paper. The specialized paper and materials can provide water resistance, graphics or labeling, or a specific color.
The two main types of paper tubes and cores include spiral wound and convolute or parallel wound paper tubes. Convolute wound tubes are used in applications requiring high blood strength, crush resistance and dynamic strength.
A spiral wound tube has the paper ply or plies wrapped around at an angle to the tube’s axis. Paper tubes have thinner walls and are widely used as containers for packaging of products.
A paper core is essentially a heavy walled paper tube. The much thicker wall of paper cores enables their use in winding webs or sheets of flexible material into rolls in converting operations.
Paper machines produce extremely large rolls (also known as machine, jumbo, tambour or mother rolls), which are rotary slit or converted into many narrower smaller rolls on a winder with a paperboard core. Similar jumbo rolls are converted in plastic film, foil, textile and coated abrasive plants.
You will be surprised that not all paper tubes are geared toward packaging applications. Paper cores can be machine elements. Paper cores used for winding large rolls in a paper mill or plastic film production plant are machine elements and require extremely high strength paper cores, which are often convoluted.
Paper cores for retail or small diameter width rolls of adhesive tape, label, foil, paper, tissue or plastic film are a packaging and dispensing product, which can consist of a thinner, spiral wound core.
The paper tube material is rotary or saw cut into paper cans or composite cans, shipping tubes, push tubes, pyrotechnic tubes, display poles, converting cores, concrete piling forms and other paper tube products.
Large fiber or composite drums and even paper straws are manufactures in a similar winding process. Convolute winders are typically used to make composite drums, which are a more eco friendly alternative to steel drums. Paper straws are spiral wound at very high speeds.
Paper Tube Shapes
Most paper tubes have a cylindrical shape or round cross-section, but paper tubes can be made with square, oval, hexagonal, triangular and other custom shapes by using a square, oval and custom shaped winding mandrel. Custom shapes are useful for fitting the tube specifically to a part or product shape while eliminating wasted space and additional spacers or packing material.
Tapered paper tubes or paper cones are wound with a cone-shaped mandrel. Paper cones are used as yarn carriers in the textile industry.
For certain applications, you may want your paper tubes slit or cut along their length to make half shells such as facilities covering large rolls for protection. They can be reconnected with tape or h-profiles. You will find covering a paper roll or coiled steel roll easier with half shells compared to sliding a roll into a large protective paper tube.
Spiral paper Tube or Core Manufacturing
In the spiral paper tube or core manufacturing process, jumbo rolls of paper, paper board and lining materials are converted in a rotary slitting operation into narrower width ribbons. The paper ribbons are rewound into narrow rolls o rewinding stands.
The narrow paper ribbon rolls are stacked in what looks to me like giant stacks of “Poker Chips”. The “Poker Chips” stacks or rolls of paper ribbon are transported and loaded into the tube manufacturing machine.
Narrow paper webs or ribbons from several different rolls are passed through guides and attached, adhered or taped to a steel mandrel in an overlapping fashion or with spacing between leading edges of the paper ribbon. The festooning or spacing allows the ribbon to feed without interference between ribbons.
You will see that by attaching the leading edge or end of the ribbon obliquely or at an angle less than 90 degrees to the axis of the mandrel, the result is the formation of spiral during winding.
The outer diameter of the steel mandrel determines the inner diameter of the finished paper tube. The wall thickness of the tube is a function of the thickness of the paper or paperboard ribbons, the adhesive thickness and the number of ribbons used in the process.
Adhesive or glue is applied to each paper ribbon or ply before being wound onto the steel mandrel. In my experience coating webs of paper, cloth, vulcanized fiber and plastic film, a variety of web coaters can apply the adhesive to the piles such as:
Roll Coaters – Extrusion Coaters- Spray Coaters
Reverse Roll Coaters – Curtain Coaters – Blade Coaters
Slot Die Coaters – Brush Coaters – Melting Bar Coaters
Dip Coaters
What’s Fascinating is how the paper tube belt twists around in a helical shape to continuously form and bond the paper tube piles together. The flexible belt wraps
around and applies pressure to the paper layers, which assures the proper formation of adhesive bonds between the paper ribbons. The fabric reinforced rubber belt also advances the tube forward along the mandrel.
I have to imagine that the stresses and performance requirements on the paper tube forming belt are enormous. These belts are endless or seamless and prevent marking. They have high tensile strength and high friction to grab and more the tube along and easy to clean.
As additional paper plies are added at one end of the paper tube forming mandrel, the formed or laminated paper tube slides of the other end of the mandrel and is cut to length using rotary blade slicing or offline sawing operations. Additional deburring of the tube and edge may be performed depending on the end use.
Another interesting aspect of the paper tube manufacturing process is the ability to make an enormous amount of highly customized paper tube product or materials combinations by using different material plies.
Linear or Lining layers are used on the inner diameter (first ribbon) or outer diameter (last ribbon) of the tube to improve water resistance, moisture resistance or grease resistance. Liners can consist of metal sheet, foil, coated paper (wax, silicon or plastic), plastic film and other protective materials.
If your current application is not satisfied with existing paper tubes, you can well imagine a custom paper tube manufacturer can engineer a new combination of liners, plies and wraps to meet the needs of your specialized application. As long as the order volume is sufficient.
Paper Tube manufacturing has the ability to provide branding through labelling or print to enhance marketing inside and outside. If printed or decorated graphics are required on the inside or outside of the paper tube, then the printed paper ribbons or ribbons made of printable material can be used for the first and last ribbons. A white paper or paperboard could be used on the outer layer with stronger brown craft paper used on the inner layers.
Convolute paper Tube or Core Manufacturing
If the parallel or convolute paper tube or core manufacturing process, jumbo rolls of paper, paper board and lining materials are converted in a slitting operation, but not into the very narrow width ribbons are used in Spiral Tube manufacturing. In the convolute paper tube or core manufacturing process, the leading edge of the ribbon is parallel to the axis of the paper tube mandrel, so a single seam or flap along the length of the paper tube results.
An external metal roll can apply pressure instead of a belt, which squeezes out any voids or air pockets providing better contract of the adhesive and therefore a stronger adhesive bond between paper plies. Since the paper web is wider, high pressure and tension can be applied in the convolute winding process. The higher pressures and tension in convolute paper tube manufacturing result in tubes with higher strength compared to the spiral wound tubes.
Convolute paper cores have higher beam strength compared to spiral wound cores, which makes convolute cores desirable in web manufacturing and converting. Convolute paper tube processes are used to form high strength, heavy duty cores for winding and unwinding of large jumbo rolls of flexible webs such as:
- Paper and Paper Board
- Coated Abrasives
- Plastic Films and Rubber Sheets
- Woven and Non-woven Textiles
- Metal Sheet and Foil
- Carpeting and Flooring
When we think about a paper core, we need to think of them like other rotating components such as bearings, gears, chucks and shafts. In heavy duty converting operations, paper cores are considered a machine part. They are not a packaging product because they impact the function and integrity of web manufacturing and handling machines. Spiral wound paper cores are sufficient for lighter duty applications such as packaging and dispensing smaller width and diameter rolls of labels, tape, foil, tissue, paper, paper or plastic film.
Combined Convolute and Spiral Tube manufacturing
The Spiral and Convolute tube manufacturing processes are combined to produce some tubes. For instance, a spiral wound tube made of kraft paper could have an outer white paper or plastic layer with graphics and labelling wound around the outside of the tube using a convolute winding process.