Expertise

It’s difficult to measure the inside diameter of a tube accurately using vernier calipers. Verniers can be used as a guide but if the Inside diameter is a critical dimension then we always ask our customers to, if possible, send us a sample of their tube and then we use our full range of plug gauges to accurately match the customers requirement to the exact ‘spindle’ size required.

The thickest wall we can produce is 18mm.

We manufacture spiral tubes down to 0.45mm thick wall and convolute tubes down to 0.3mm wall.

Lead times vary between customers according to their requirements; their geographical location and type of product being manufactured. Some of our customers operate highly lean and flexible factories and need lead times of 24 hours or less, some of our customers order tubes a month in advance. As part of our sales process, we seek to understand what is required and develop the most cost effective and practical solution in partnership with the customer.

Yes. Broadly, there are four aspects of board quality that must be considered for Cardboard Tube winding: there are the strength, thickness and surface characteristics of the board but also the consistency with which a particular mill maintains these characteristics. We use a large range of cardboards with different strengths, thicknesses and surface characteristics but we only use suppliers that can deliver these consistently. One of the benefits of being 150 years old is the organisational knowledge and experience of suppliers, mills and materials that this brings!

For example, this experience allows us to tailor products precisely to our customers’ requirements: if you need extra strength but are constrained by the Outside Diameter size, we can specify a stronger board. Or perhaps you need a tube with a particularly tough inside ply to prevent damage on a driving shaft? We can suggest different options for this too.

Cardboard tubes are manufactured by wrapping board (or paper) around a steel mandrel (or spindle). In our industry some people call mandrels, spindles and some people call spindles, mandrels! At Stell we use the word “spindle” to describe each tool we use. Each spindle is defined by its outside diameter and this defines the inside diameter of the cardboard tube – which we often to refer to as the ID. Convolute tubes are manufactured on a different design of spindle to spiral tubes. Either way we have the UK’s biggest spiral tooling library and the UK’s biggest convolute tube tooling library. We can always match exactly what our customers require.

Cardboard absorbs atmospheric moisture and so sudden changes in atmospheric moisture levels will cause the moisture level in the cardboard tubes to change. This can be problematic for longer tubes where one side of the tube changes moisture levels much more rapidly than the other. So, just like a plank of wood can warp, cardboard tubes can bend if they are not constrained and exposed to changing heat/moisture levels. For this reason we recommend cardboard tubes are stored in well ventilated, heated storage areas and not exposed to direct heat sources.

In terms of the manufactured sized of the tube there is obviously no different between a 76.4 ID tube with a 3mm wall and a 76.4mm tube with an 82.4mm OD. However, our convention is that for tubes where we know that the strength is critical we will define them with a wall thickness and for tubes where we know that the OD is critical we will define them with an outside diameter.

Cardboard, by its very nature, absorbs water and we use non toxic water based solvents. We therefore can’t make a water proof cardboard tube. However we do have a wax dipping process that provides a water resistance to the tube which is useful for pyrotechnic applications or where the tubes life needs to be extended.

Yes, we have our own in-house crush-testing facility and so can design tubes to with stand specific crush forces.

The crush strength is a measure of how well a tube resists a force applied perpendicular to its circumference; this is often the critical strength when materials are wound onto the tube at high tension. The beam strength is a measure of how well a tube resists force applied perpendicular to its length when it is only supported at either end. This is often a critical measure of its strength when a tube is held between two chucks for a re-wind process or when it is being transported – for a wide web of material, you don’t want the tube to bend too much that it causes the material to crease.

Spiral and convolute cardboard tubes have very different manufacturing processes. They are also quite different visually; a spiral tube normally has an easily identifiable spiral mark on its outside where the outer ribbon is spiralling next to itself (“butt-jointed”) or where there is an overlapping ‘cover’ (thin ply) of paper on the outside. In general, spiral tubes can be manufactured to tighter tolerances with a higher quality of finish than convolute tubes.

A convolute cardboard tube is made from a single sheet of paper with a straight seam running down the length of the tube. This seam is not always easy to spot if it has been ground to a feathered edge. Due to being made from a single sheet, convolute tubes are more restricted in their geometric range than spiral tubes.

However, the single sheet fabrication of convolute tubes gives them two distinct advantages: firstly they are able to withstand higher internal pressures (important for pyrotechnic uses) and secondly they have a higher beam strength (compared with the equivalent spiral tube) which means they can be a cheaper option for many textile and material processing applications where beam strength is an important part of the specification.

Some people say tubes some people say cores – the words core and tube are largely interchangeable. But in the industry, we generally class cores as a tube that has been cut to a shorter length, and tubes are longer. But where ‘shorter’ becomes ‘longer’ is down to personal opinion!

Spiral tubes and Convolute tubes have very different production methods and machinery. We make both types:

Spiral cardboard tubes are made by coating the top side of ribbons of cardboard (also called webs or plies) with an adhesive, then winding these in a continuous process around a steel mandrel using a rubberised winding belt to pull the board around the mandrel. A flying knife is then used to cut the tubes to a desired length whilst the tube is being continuously wound.

Convolute cardboard tubes are made using a single sheet of cardboard. Typically, this sheet would be unwound from a jumbo reel and guillotined to the required length on the machine. The width of the sheet is dictated by the width of the jumbo reel. One side of this single sheet is then coated in adhesive before the ‘lip’ of the paper is fed into a grooved mandrel. The mandrel is then rotated, and the board wraps around the mandrel, forming the tube. The tube is then doffed off the mandrel and the machine is ready to start the next cycle.

At Stell, we have the UK’s largest Cardboard tube tooling library with over 200 spiral spindles/mandrels and over 250 convolute spindles/mandrels.

Nothing! Some people use the term Cardboard Tube and some people use the term Paper tube – both are commonly used. Generally, Cardboard is thought to be a ‘thick’ paper but there is not universal definition of what ‘thick’ means. Most of our tubes are made from a material that most people would call cardboard so we call them Cardboard Tubes. That said, looking at some of our marketing material from the 1920’s, we were described as Paper Tube Manufacturers!

Yes absolutely. Cardboard tubes and cores are considered one of the most environmentally friendly types of packaging because they are made from a renewable source. Cardboard is one of the materials with the least environmental impact. It is 100% recyclable and 100% biodegradable.

The cardboard is collected by either a waste merchant, or the original manufacturer before being sent back to a board mill where it is graded for quality, sifted for contaminants and then re-pulped (shredded and mixed with water). Then it is fed back into the paper making process.

Cardboard cores are used in many different industries and processes. Almost every single type of tube or core has probably been used in some sort of industrial application from textiles and carpets to tapes, labels and films.

And each one is different. For example, cores for wrapping paper and packaging don’t need to be as durable or strong as heavy duty cores you’ll find used in the flooring industry.

Convolute or spiral tubes used for pyrotechnics must be manufactured so they are safe and reliable. And for flexible films we know its important to manufacture them with the appropriate levels of crush strength.

If you want to know more about how we add value to manufacturing and supplying cardboard tubes in your industry please get in a touch!