Vector Systems

In this article, we explain the essential part that glue performance plays in the process of continuous roll-on edge-banding.

Traditionally, edge material (clashing) was applied using a glue and clamp process.  Adhesive was applied to the clashing and the panel and the two pieces were then pressed together and held by clamps until the adhesive had set.

In the early 1990s PVC edging became popular due to its durability, low cost and large variety of colours and finishes.  However, traditional clamping methods were too costly for these new materials. Up until this point the through-feed roll-on edge-bander, which was developed in the 1960’s, wasn’t widely used. However, because of PVC edging, it disrupted the industry, and through-feed banding development became essential

An often unappreciated, but critical, part of the success of through-feed edge-banding is the role of the adhesive.  This seemingly innocuous item is crucial to edge-banding performance, but has to meet important criteria to work in an effective way.

Key glue criteria

Firstly it must have an appropriate ‘open time’. This is the time that the glue remains molten after being applied to the first surface (i.e. the panel) before it forms a skin which then prevents adhesion.

Secondly it must have very fast ‘quenching’ properties. This is the time taken for the adhesive to ‘set’ when the panel and edge-band are pressed together.

Thirdly it must have specific ‘tack strength’ (also called ‘green strength’). This is the instantaneous pull strength of the glue when the panel and edge-band are first pressed together.

With the rolling continuous through-feed process, the glue is typically applied to the panel some distance (typically 200mm or more) before the band feed and first pressure roller.  It’s critical the glue remains molten until the band and panel meet at the first pressure roller.

At the first pressure roller, the band and panel are pressed together. At this point the glue needs to quench rapidly. It must also have a high enough tack strength to prevent the band slipping on the panel and to prevent ‘popping’ of the band caused by the second pressure roller bumping up onto the panel.

The faster the feed rate, the less ‘pressing time’ from the pressure rollers, and the faster the quenching rate has to be.  The second and subsequent pressure rollers have little impact on glue bond strength so the first roller is the most critical one.

This is a remarkable feat of adhesive technology, because the rapid quench and tack strength characteristics of the glue work in the opposite way to ‘open time’.

The effects of temperature and other factors

It’s the reason that typical edge-banders are susceptible to changing temperature conditions. In a cold winter factory, the panels are cold and, as a result, the open time of the adhesive is shorter because the panels quench the glue faster. To deal with this problem heated infeed fences are common on straight-line edge-banders.

External effects such as draughts and fans only add to the variable performance of the adhesive.  Bond strength is seriously compromised if the glue skins off before the edge-band and panel are pressed together at the first roller.

Contour edge-banding only ramps up the demands on adhesive performance because the contour edge-bander must also overcome band memory

See also: Why Contour Edge-Banding Machine Design Is Critical For A Quality Finish

Band memory

For a contour edge-bander to successfully bend stiff banding around a small radius, the feed rate must be able to be slowed sufficiently to allow the pressure roller to hold the band long enough for the glue to overcome the ‘popping force’ caused by wrapping the band around the small radius.

The slow feed rates required to achieve this, mean that most contour edge-banding machines need an external heat source to keep the glue molten and soften the banding.  However, external heat applied to the band or panel works against the quenching effect and compromises the quench time and tack strength.

As with straight line edge-banding, the introduction of external heat sources such as panel heaters, band heaters and glue heaters add more variables. This makes the skill level of the operator especially critical, because they need to be able to interpret edge-band material performance and ambient conditions.

These variables however can be minimised when certain machine characteristics are optimised.

Here’s how to minimise the variables:

1. Position the glue unit close to the first pressure application roller – ideally less than 50mm. This will minimise the effects of slow feed rates for tight radius corners and means no external heating is required.
2. Apply the glue to the band material instead of the panel. This has a double benefit:
   • It minimises the quenching effects of cold panels on the open time of the glue.
   • Cold panels enhance the quenching and tack strength performance of the adhesives by dragging the glue temperature down faster when the band and panel are pressed together.
3. Increase roller pressure and use rubber or urethane rollers. The result of this combination is it:
   • Creates a quicker quench of the adhesive
   • Lengthens the time the band is pressed against the panel, because it creates a greater flat spot under the roller as it presses the band
   • Significantly improves bond strength
   • Reduces glue line thickness.
4. Choose the best quality glue with characteristics matching the machine performance.

 Summary

In summary, I cannot stress enough how glue quality and characteristics affect the performance of edge-banders.  Selecting the correct glue for your machine, while in some instances may increase adhesive cost, will save considerably cost more in giving easier and better operation of your edge-bander and reduced rejects.

Glue makes up a small fraction of the cost of the raw materials in an edge-banded panel, but plays a big part in achieving a successful and high quality result. While your accountant may question the monthly payment to the adhesive supplier, it’s important to understand that there are far greater costs to your business through production difficulties in using an inappropriate or poor quality glue.

 

Coming up will be an in depth investigation into glue performance.  Watch this space….

 

There are a number of different types of machines for contour edge-banding.  In this article we compare them and explain the pros and cons of each method. The goal is to help you make an informed decision about the right machine for your situation and mix of work.

There are three main categories of contour edge-banding machines:

1. Manual
2. Semi-automatic
3. Fully Automatic

Manual Machines

Manual machines have a rotating roller and a glue application system.  There are two types:

• The first has a roller and glue system protruding from a table requiring the operator to manipulate the panel to apply the pressure and banding

• The second has the panel fixed to a vacuum table and the banding unit is manipulated around the panel.

In each case the operator is applying all of the pressure and controlling the angle of the pressure.

The advantage of these machines is low cost.

Disadvantages are:

• The machines are very operator dependent
• Quality of output can vary significantly depending on the operator and operator tiredness.

It’s difficult for an operator to apply sufficient pressure. This means that, often, more than one person is required, especially when dealing with large panels.

As a result the glue bond is weaker, so you usually need to use Flex Edge to enable smaller radius corners with consistency.

Butt joins have to be overlapped and then trimmed manually which is time consuming and quality can vary.

Semi-Automatic Machines

Semi-automatic machines use pinch rollers to rotate the panel around a fixed banding head. They use the angle of the pinch rollers (like an angled power feeder) to apply pressure against the edge as well as to rotate the panel.

The advantages of this system are:

• Low cost
• Simplicity

The disadvantages are:

• The edge pressure is very low, which means semi-automatic machines typically require the use of Flex Edge to bend banding for anything other than large radiuses.
• Radiuses less than 50 mm external, and 100mm internal, are typically not possible.
• As with manual machines, they require the operator to apply extra pressure and assist the machine to manipulate the panel around tighter radiuses.
• They also do not vary speed according to corner radius, which significantly limits their ability to handle complex shapes.

For these reasons semi-automatic machines are also very dependent on operator “feel”, which means quality can vary between operators.

Because these machines can use only very flexible edge banding material, they usually require the use of Flex Edge. Flex Edge is a very soft material that makes it easier to bend around smaller radiuses.  However, Flex Edge:

• Limits the range of suppliers for banding
• Is more expensive than standard banding materials
• Means trimming finish tends to be lower than when using standard edge-band materials, because of the plasticisers in the banding that are needed to make it flexible.

Typically Flex Edge is made from PVC and is not available in “greener” recyclable materials such as ABS and Polypropylene

Butt joins are not as accurate or repeatable as fully controlled automatic machines.

Fully Automatic Machines

There are 2 types of fully automatic machines:

• The patented Vector Revolution principle banders
• The CNC hybrid contour banders

Patented Vector Revolution Principle

The Vector Revolution machines use a patented pressure system utilising artificial intelligence (AI) algorithms to automatically analyse the shape of the panel as the head progresses around the panel. It requires no programming.

The advantages of this system are:

• Simplicity – no programming is required, which means a significant cost and time saving
• Separation of the banding process from the shape cutting, which means high productivity for both the shape cutting and edge-banding machines
• Very high edge pressure. Which makes for the best possible glue bond and glue line thickness. This feature of high edge pressure (and strong glue bond) is particularly important to overcome band memory with contour edge-banding.

A further advantage of the Vector Revolution principle is that it is fully compatible with nested based manufacturing.  With shaped components, enormous time and material savings can be made by nesting the shapes.   The Vector Revolution principle then easily performs the edge-banding processes without any issues of panel alignment on the machine.

The disadvantages compared to CNC hybrid contour banders are:

• The need to transfer the cut panel from the CNC shaper to the specialist edge-bander.
• It’s not possible to perform secondary machining processes after banding, such as notching or drilling through the banded edge.

Advantages of a dedicated contour bander with separate CNC machines for cutting the panels are:

• Compatibility with nested based manufacturing. There is no need to cut shapes from pre-sized panels.
• Routing dust does not interfere with the edge-bander performance.
• CNC router capacity is optimised as it isn’t limited to cutting only panels that need contour edge-banding.
• The CNC router capability can be matched to general cutting requirements. For example, if you’re only nesting 18mm panels, then the size of the router and machine can be smaller, which saves cost.

CNC Hybrid Contour Banders

The CNC hybrid contour edge-banders use a CNC program to first cut the shape then, because it knows the position of the panel, use a second CNC program to carry the edge-banding head around the panel.  This is followed by trimming and scraping.

The advantages of this system are:

• The panel is placed on the machine and not handled until complete.
• It is also possible to do multiple processes on the panel, such as applying different band thicknesses to the same panel, notching and drilling, all in the same setup. This is a particular advantage with highly complex panels where multiple processes are required and risk of damage is costly.

The disadvantages are:

• Machine cycle times are generally quite long for each panel since they have to both cut and apply the edge-band
• Capital cost of the machine is high.
• Operators need to have high skill levels to setup and operate the machine.
• A skilled CNC programmer is needed in the office to do the separate CAM process for the banding process.

These machines are ideally suited to high value components such as high end office furniture. It can be difficult to get an economic return producing high volume mid range and low end panels such as closets, school desks, store-fixtures and the like.

Summary

As businesses look to differentiate their products from competitors, shaped panels are making up a greater proportion of components manufactured in the joinery industry.  This is evident by the high number of new manual machine manufacturers in the world as demand for entry into this field increases.

The opportunity to create new products and designs with contoured panels means manufacturers have many new possibilities to present a range, which takes them away from the commodity areas of box based components, and differentiates them from competitors.

 

It’s also common to hear that ‘cut and clash’ component suppliers (those supplying to other manufacturers), who invest in contour edge-banding equipment, win contracts they couldn’t win before, because they had now overcome their inability to reliably produce shaped components.

Contour banding is a whole new learning experience but worth the effort as it opens up new market opportunities with increased margins.

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Definitions:

1. CNC – Computer Numerical Control
2. CAM – Computer Aided Manufacturing – this is the cutting of the panel to the contoured shape

 

Most cabinet shops find edge banding one of the more challenging processes.

This is because of two key reasons. Firstly the fine finish tolerances you need to deliver a high quality result. And secondly the difficulty in working with the combination of panel, edge-band and glue.

There are two distinct types of edge-banding:

• Straight line edge-banding (SLE)

 

• Contour (or curved) edge-banding (CE)

 

Straight line edge-banding is used for standard square or rectangular panels with straight sides. Contour edge-banding is needed for panels with curved edges that have been cut with a CNC* machine.

Edge-banding machines are very mechanical. And they’re made more complex because of a large range of adjustments the operator needs to make to achieve a quality finish.

The critical things for straight line edge-banding are:

1. Skilled operators
2. Banding glue and panel quality
3. Stable machine

Get these three things right and you have the essence of a successful, high-quality straight line edge-band

While straight line edge-banding is difficult, it’s far more challenging to get a high quality result with contour edge-banding.

Contour edge-banding raises the difficulty, because not only do you need to work with a curved edge, you also have to overcome band memory.

What is band memory and why is it important?

This is the edge-band’s natural tendency, when released, to spring back to a near-straight state.  On a straight line edge-bander the glue force needed to hold the band straight is minimal. However on a contour edge-bander, the glue must provide much higher grip to bond the band tightly to the panel contours.

As the corner radius becomes smaller, the force the glue has to apply increases significantly. This is because the edge-banding process has to overcome increasing band memory. The easiest way to see this for yourself is to take some banding material and try to hold it tight against the board around a small radius or wireway.  Where gaps appear between the band and panel, press them down with your finger and see how much force is required. This is the adhesion force the glue needs to deliver to bond the band securely to the panel. And it has to achieve this in a very short time before the roller rolls off that section.

All modern edge-banders are a continuous rolling processes.

This means there is a critical relationship between roller pressure, edge-band feed speed, glue open time* and glue tack strength*.  In contour edge-banding, the relationship between machine, edge-band, pressure and glue is much more important because of the issue of band memory.

Unlike straight line edge-banders, where all machines use the same basic process, in contour edge-banding there are many different machine types. So having a good understanding of the intricacies of contour banding makes choosing the right machine easier.

One of the most important details is how close the glue unit is to the first pressure roller.

This is because tight corners mean the feed rate must be slower to allow the glue to tack-off to overcome the tension of the band memory. The longer the distance between the glue application and the first pressure roller (pressing the band to the panel), the greater the effect of variations in air temperature, feed speed, band characteristics etc.

This means the operator must have a solid understanding of how these factors relate to product quality, and must be able to make the appropriate adjustments. The best contour edge-banding operators understand their craft in a similar way that solid wood machinists understand the characteristics of their machines and the wood.

Also don’t compromise on glue quality.

Glue is the link between the board and the band. A high quality glue will make up for a lot of inconsistencies in band and board quality.

See also: Why Is Glue Type So Important In Contour Edge-Banding?

So in summary

It’s important, when purchasing a contour edge-bander, to have an understanding of the challenges faced when you’re bending rigid banding materials around complex shapes.

The most successful cabinet shops choose the best quality edge-banding machines they can afford, ideally with a short distance between the glue applicator and the first pressure roller, use high quality glue, and invest in the best quality operators.

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Definitions

1. CNC –Computer Numerical Control.
2. Open time – Length of time the glue remains tacky after application to the band.  Note:  the characteristics of the band can also affect the open time as different band materials have different heat absorption characteristics. Those which draw heat quicker will reduce the open time.
3. Tack Strength –This is the instant strength of the glue when the band is first pressed to the panel.  Also known as green strength.  This is critical in contour banding applications to prevent the band memory causing the band to pull away – or pop – when the pressure roller passes over the band.  The heat absorption characteristics and temperature of the band and panel can significantly affect the tack strength.  For example, if the band or panel are very hot before being pressed together, the tack strength is compromised.

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