Professional Agricultural Articles
It has been estimated that every year in the UK as many as 22 million round bales are made using netwrap. By any measure, that is a lot of netwrap! It has been around for over 25 years, so many of you are more than familiar with net and how it works, but there is more to it than that. Franze ThreadNetwrap is manufactured with long ‘Franze’ threads  (the heavier threads) connected by ‘Shuss’ threads (the cross threads). The strength of the net is carried by the Franze threads, the lighter shuss threads are only to hold the Franze threads in place. All of the heavy ‘franze’ threads are acting together give the net its overall strength.Care should be taken when choosing nets which include single coloured threads, as some makes and brands may use a different material to the rest of the net for the identifying coloured thread.  Single coloured threads within a netwrap are a mark of identification from the manufacturer. Coloured threads are not related to any higher strength or better spreading ability of the net.
There has always been a lot of misunderstanding or, more accurately, misinformation about netwrap. By design, netwrap is very flimsy in appearance and feel, but it is manufactured to withstand the considerable pressures it endures during use and afterwards, from the baler as well as containing dense and, sometimes, explosive crops. One common misconception is the ‘weight’ of the net and how this is measured, often incorrectly referred to as ‘gauge’, when what is really meant is the grammes per metre weight (g/m).  Even so, the ‘weight’ of the net does not give any indication of the actual strength of the netwrap.  Netwrap strength can be affected massively by the quality of raw material and accuracy of extrusion and manufacturing, and it is often the case that a producer quoting a higher ‘weight’ (g/m) type of net is doing so as this may be the only way to achieve a given strength.  In doing so, of course, this producer becomes restricted on either roll length or roll weight, unlike newer technology such as Bale+™.Incorrect or misleading information about netwrap can create confusion in the market, which can have a serious effect on the performance of the net in your baler as well as seriously affecting the quality of the bales you produce. Often, demonstrations on how ‘strong’ a net seems to be are shown by pulling the net apart in a sideways direction, which, because of the construction of all netwrap, will always result in the net tearing apart. This is quite wrong. What should be understood by everyone is that the strength of any netwrap is in its ‘running direction’, along the heavier strands that go around the bale. The lighter ‘zig-zag’ threads are simply there to hold the heavier threads in place and offer no supporting strength to the net.In the information that follows, we have tried to summarise some of the main points in netwrap construction, which we hope will offer some advice on what to consider, or what to dismiss as ‘mis-information’ when choosing your netwrap for this season.

High Spot
Any different material may cause problems in the baler, by causing a ‘high spot’ on the net roll profile. This can be problematical in balers where the net sits in a box, with the roll turning on itself – with greater pressure on the ‘high spot’ creating excess friction that can easily break the net.

Net Constructor
A net constructed with cross pattern ‘shuss’ (zig-zag) threads within the net, either in the centre or on the edges, does not offer any greater benefits in strength and is simply a manufacturer preference during production. As we have seen, the strength of any netwrap is in ‘running direction’ and is carried by the heavier Franze threads, adding extra ‘shuss’ threads in the net does not add to the overall strength of the net in any way.

Understanding more clearly the properties and characteristics of netwrap should help you more in your purchasing in the future.  This season, more than ever, wise decision making will become more critical than ever. Choose wisely and buy the best quality – you know it makes sense! Remember, there is a very true old adage that says …”buy cheap – buy twice”.

Think what it means and remember, your Crop Packaging Association is here to help you with any queries or questions you may have. We are always happy to hear from you …

Professional Agricultural Articles

Why Bales bursting

It is important to understand and appreciate the various factors that determine how safe and secure your bale is. It may only need to remain intact for a short time; alternatively, it could be required to remain wrapped and fully intact for a whole year or more. Consider:

  • the actual type of crop and how it will be used.
  • how and where the bale will be stored.
  • how the bale will be handled.
  • how many times the bale will be handled.
  • the weather conditions when it is baled and when and where it will be stored.

Round baling with netwrap is the most convenient and least expensive way of wrapping your bale. Wrapping with netwrap reduces costs by being faster than using twine and offers much better protection to the crop than twine ever could.  However, the actual security of your valuable bale is down to you and how well you know and use your baler. It is very important that a MINIMUM of NOT LESS THAN 2 layers of net are applied to the bale, as there are many ways that the ACTUAL amount of net applied can be LESS than the baler is set to apply.

Baler accuracy

Most modern balers are equipped with net application systems, controlled by an in-cab control box (some lower specification machines may be fitted with mechanical operation, adjusted on the baler itself). Very often, the amount of net expected to be applied to the bale is considerably less than actually wrapped on the bale. The quantity of net applied should always be checked ON THE BALE, as the setting on the baler is only an ‘indication’ and should never be assumed to be accurate. There will always be variations in the amount of net on the bale, these are dependent on a number of important factors:-

BALER ACCURACY
Is the baler’s feeding system accurate enough to feed the correct amount of net into the baler?

BALER ACCURACY
Is the net feeding uniformly across its entire width, or not giving full width cover all around the bale?

BALER ACCURACY
Is the net ‘bunching up’ in the baler as it feeds before reaching the bale – so wasting some metres of net?

D
Is the net being pulled to one side or the other from long threads hanging on the net from the previous wrap – so part of the bale has less net than another?
 signs  BALER ACCURACY
Is crop still being fed into the baler as the net is being applied, so not all the net is on the outside?
Correct net application should be fully to the OUTSIDE of the bale.  It is important that once the net is being applied, forward motion of the baler should have stopped, so avoiding crop being taken is as the net is being applied. If this happens, the full ‘solding properties’ of the net will not be possible, as some of the net is now incorporated inside the bale, so reducing the ability of the net to secure the bale.

Climate

Certain regions of the world have higher U.V. radiation levels than others, caused by latitude, weather and climatic variations and air pollution levels.  In these regions, bales stored outside with continual exposure to high U.V. radiation levels can suffer increased degradation of the netwrap.

CLIMATE CLIMATE

Netwrap tensile strength is at its greatest when first used.  However, continued exposure to the elements, as well as being under ‘load’, when wrapped on the bale and holding the crop, all have an effect on the residual strength that the netwrap can retain.  If used and applied correctly, netwrap is designed to maintain 50% of its applied strength over a 12 month period.

It is important to consider these factors when making and storing bales in higher U.V. radiation regions.
Where netwrap on a bale is under greater tension than recommended, due possibly to bale pressure or insufficient netwrap layers on the bale, the inherent strength of the netwrap can be reduced when exposed to higher U.V. radiation levels.
Tama Netwrap is specially designed to hold the bale for at least 12 months and has UV stabilization
to assure it will retain at least 50% of the original net strength after 12 months in the field.
Netwrap - residual strength over time

In order to achieve best wrapping results it is highly recommended to follow the instructions detailed below:

  • Netwrap rolls (before baling) should be kept in their original packaging under cover, in dry conditions, to assure best performance.
  • To reduce the risk of bursting bales and netwrap failure on the bale during storage, handling or use of round bales, it is extremely important that sufficient netwrap is applied during baling – in accordance with manufacturers’ recommendations.
  • Ensure the netwrap (roll or netwrap on the bale) is not exposed to any type of agro chemicals, as this can affect the net strength and reduce the time the net will securely hold the bale.

 Crop and Conditions

The type of crop being baled and the way the bale will be handled afterwards have huge influences on how much net should be applied to the bale. There should ALWAYS be a MINIMUM of at least a 2 layers of net ON THE BALE, but the diameter of the bale, the actual type of crop and its characteristics when baled will determine the REAL MINIMUM amount of net to be used. Netwrap Baling Guide
Grass forage crops, such as silage, haylage, Alfalfa etc., are heavy leafy crops, often baled with a diameter of 1.2m – 1.5m and, when cut and baled, tend to be ‘inactive’ and do not have a characteristic for expansion. In general, the weight of the bale and the method of bale transportation are the main factors in deciding how much net to apply to the bale.  It is important to remember that when baling silage, the amount of netwrap applied to the bale should not be reduced because of the film wrapping immediately or soon after baling.  It has been proven that if fewer than minimum of 2 wraps of net are applied ON THE BALE, there is a high risk of the netwrap slipping and allowing the bale to expand. Bale expansion before or during wrapping brings two problems:- Cereal crops, such as wheat, barley, etc. produce lighter bales and are, by comparison, more ‘explosive’ in their characteristic after baling. These longer, hollow-stem crops do not compress as well as a leaf crop and, consequently, are more likely to require a greater number of net layers for them to be safely contained. As these bales are, generally, not as heavy as leaf crop, the bale dimensions are typically greater, with bale diameter between 1.5m – 2.0m.  Bales of this size mean a greater circumference and, therefore, a greater ‘energy’ contained within the bale.  With a greater surface area of bale wanting to expand more, the netwrap is under considerably more pressure.  In such cases, it is IMPORTANT that more net is applied to the bale to ensure adequate security of the bale.
  1. The increased bale diameter will alter the wrapping pattern of film being applied to the bale, so disrupting the calibrated wrap over-lap on the bale and reducing the amount of film layers applied.
  2. If the bale is allowed to expand before wrapping, the density will decrease, allowing the bale to become more aerated, affecting the fermentation process and reducing the quality of the silage being produced.
 Grass Forage Crops

Bale Shape

If the bale shape is not uniform, the net will be under varying tension from the un-even pressure within the bale. A bale which is not flat and uniform will have more pressure in the centre and so apply more pressure against the net in this place. This increased and excessive pressure against the net will create higher tension forces against the net threads causing one or more to break, which will, in turn, increase the tension on the remaining threads and, therefore, eventually cause more threads to break. Also, badly shaped bales, like this, will have more risk of damage on the ‘high point’ when being ejected from the baler or when being handled, because of the shape and higher net tension in this area. BALE SHAPE
Professional Agricultural Articles

Netwrap Manufacturing

Netwrap is manufactured from High Density Polyethylene (HDPE), a thermoplastic resin produced from the chemical molecule ethylene. It is the most common polymer used in industry as it offers excellent properties of strength verses weight.

HDPE is the result of a process called polymerization, sometimes referred to as ‘cracking’, which combines small molecules (each called a ‘Mer’), into very large molecules (‘Poly-mers’).  When the polymer resin is extruded for the manufacturing of netwrap, the molecules become arranged along the direction of the strand – ‘Machine Direction’ (or MD), giving the plastic a very high strength in this direction. When considered in this way, it is easy to see how such light material is able to withhold the extreme force of a dense and heavy round bale applied to the net, around the bale’s circumference – in the Machine Direction (MD) of the material used to construct the net.

Traditional netwrap manufacturing involves a two-stage process.  Firstly, the film is extruded into a wide plastic film and wound onto large sized ‘mother rolls’.  The film from these rolls is then slit into narrow tapes, which are then knitted together on knitting looms to produce a net mesh.

Extrusion Knitting

Weight vs Strength

Normally, to increase the strength of plastic agricultural packaging (netwrap or baler twine for example) requires the use of heavier, or thicker, material. However, increasing the thickness and weight of the material, to achieve increased strength, will produce a heavier finished product; in the case of netwrap, a heavier material (increasing the grammes/metre of the netwrap) will result in a much heavier roll, with greater diameter, for the same roll length.

If a longer length roll is required, it is then impossible to maintain either a useful roll diameter to fit in the baler, or a suitable roll weight, when manufacturing with the heavier material.
It is not possible, when making netwrap with ‘standard’ raw material, to make a product with both higher strength and longer length, without the roll becoming too heavy or too big in diameter.
As an example:

Netwrap
strength
g/m Roll
length
Core
weight
Total Roll Weight
(g/m x length + core)
240kgf 12 2,000m 2kg 26kg
240kgf 12 3,000m 2kg 3kg
260kgf 14 2,000m 2kg 38kg
260kgf 14 3,000m 2kg 44kg

Raw Material Resins

Various netwrap manufacturers use different types of HDPE materials in the production process of bale nets. Higher grade, or better quality, resins will be able to produce higher strength polymers, likewise, a poorer grade of resin will not be as strong, for the same given weight of raw material.

HDPE materialsSome netwrap manufacturing companies remain less sophisticated and unable to develop their product, or are less aware of how to develop, meaning they are forced to rely upon out-dated production methods.  Consequently, these manufacturers have to depend upon ‘standard’, and therefore, ‘heavier’ materials to ensure a certain minimum strength and quality for their products.

Tama Group have developed a revolutionary advance in netwrap manufacturing, called Tama Light-Technology (LT), which combines an advanced formula of HDPE resin with a completely new production technology.   Tama Light Technology has enabled the production of lighter-weight netwrap, which actually has strength greater than the ‘standard’ type of netwrap.  This is a result of obtaining a higher ‘Relative Strength’ of raw material and is achieved by a unique step in the netwrap production process.

Relative Strength is the manufacturer’s scale of reference in achieving the highest strength (kgf) per gramme (g) of raw material.

RELATIVE STRENGTH

RELATIVE STRENGTH

Raw Material Material Weight Netwrap Strength Relative Strength
(Netwrap strength ÷ g/m)
Standard 12 g/m 240 kgf 20
Tama Light-Technology 9 g/m 250 kgf 28

It is now very easy to see that it is NOT CORRECT to use the weight of the plastic (grammes per metre or g/m) as an indicator of the strength of the product.

Raw Material Netwrap Strength g/m Roll length Total Roll Weight
(g/m * length * core)
Standard 240 kgf 12 g/m 2,000m 26 kg
Standard 240 kgf 12 g/m 3,000m 38 kg
Tama Light-Technology 250 kgf 9 g/m 3,000m 29 kg

Using Tama Light-Technology (LT) to increase strength, also allows the manufacturer to increase the roll length, without exceeding a useful roll weight and still within the tolerance of the roll diameter needed to fit in the baler.

Tama Light-Technology netwrap is 10 kgf STRONGER and not as heavy as ‘standard’ netwrap.

Environment

Environmental benefit Tama Light-Technology plastic also has a strong Environmental benefit in agricultural use. Tama Light-Technology brings a lighter weight material, considerably less plastic is used to produce the same length of netwrap, compared with ‘standard’ netwrap production. Also, because Tama Light-Technology plastic is stronger than the ‘standard’ netwrap raw material, it can withhold the forces of the bale better.

Tama Light-Technology is approved by German DLG Signum test and is also awarded Polagra Gold Medal.

Professional Agricultural Articles
single-coloured-thread The single coloured thread will be different material and can be slightly thicker. This can  make an uneven roll profile, with a ‘high point’, which causes problems in the baler where the roll is free turning in a box.  The ‘high point’ of the net roll creates greater friction as the roll is turning, that will cause the net to break.
different-properties The different properties of the single coloured threads will cause differences in the net when being wound onto the roll. This can be an un-even roll edge profile, that can damage the edge of the net when the roll is turning in the baler.
different-material It is possible that the different material of the coloured thread will not knit together correctly with the slit tapes of the rest of the net. This can create problems when feeding or cutting of the net.
slit-film-tapes The ‘normal’ slit film tapes of the net are completely uniform, with the same properties, as the tapes are all cut from the same ‘mother roll’ – unlike the single coloured thread which comes from a different source.
coloured-thread-material The coloured thread material can be of a different profile, making it less uniform in the net construction.

What you want to believe …!

Netwrap has been with us for almost 25 years now.  Many manufacturers have not developed their product, so it is very similar now to when first introduced in the mid 1980s. Initially, netwrap was all white, actually ‘natural’ in colour, with no colouring to the raw material at all.

Some manufacturers then introduced a single coloured thread on the sides of the netwrap, as a simple form of identification of their product; one manufacturer went so far as to register this single colour thread as a trademark.  In any case, this single thread was nothing more than an identification mark.

Net Wrap Manufacturers

Single coloured threads are no stronger than any other part of the netwrap and are only there for roll identification.

Roll Net Wrap In later years, the idea of a different coloured thread on either side was introduced, as a simple form of left/right identification, useful when loading the roll into the baler.
NOT STRONGER, just different

NOT STRONGER, just different

It is sometimes believed that the single coloured thread is a strengthening ‘rib’ on the net, made of stronger material.  This is NOT TRUE.The strength of a net comes from the total of all of the threads across the width of the net and the edge thread does not have a greater strength than any of the other threads that make up the net.

The normal way to make netwrap is for the material to all come from one ’mother roll’ of film, which is slit into tapes and knitted together in the loom. If a single coloured thread is added, this comes from another source and is introduced to the loom next to the film.

Single Coloured Net Wrap  Single Coloured Netwrap
The single coloured thread must be introduced into the net from a different source, most often from a single bobbin of material.

The coloured thread at the side of some makes of netwrap is often a slightly different material to the rest of the tapes. This means that when the net is being manufactured, the single coloured thread does not follow the same route through the production process as the remainder of the white tapes. This can have an effect on the quality of manufacturing, with the different material causing trouble from different tension of the thread compared with the others during the knitting process, which can then create un-even winding on the edges of the netwrap.

As the single thread of different colour is of different specific material it will have different properties. This means that, when under load (tensioned during the wrapping operation in the baler) it is likely that the strength and elongation will vary considerably from the remaining film tapes from which the remainder of the net is made. This can result in a possible change in performance and weakening of the net where the single coloured thread is located. Film Elongation
Net Wrap Zebra System RollNetwrap made with different striped netwrap pattern is not affected in this way.This two or sometimes three coloured ‘zebra’ patterned netwrap is made from individual coloured ‘mother’ rolls of film, of exactly the same material with all the same properties. The different films are then slit into narrow tapes, which are arranged into the striped pattern in the knitting loom. The entire net maintains its uniform, high strength across the full width as there is no introduction of different material to give the colour.

PROBLEMS with single colour thread

The single coloured thread may have very different properties to the rest of the net, with a variance in material, thickness, elongation and strength. These differences can affect how the net reacts when under tension during roll winding, making the roll profile un-even.

PROBLEMS with single colour thread
The way the thread stretches when under tension in the baler might increase the risk of the net ‘necking-in’ and narrowing.
Netwrap Materials The different material and properties of the single coloured thread can affect the construction of the net, with the material not knitting into the rest of the net uniformly. This can cause problems in the baler when feeding and cutting.
Film Materials The different material of the coloured thread can be thicker, creating an un-even profile on the roll. This can create problems in the baler, causing the net to break.
Net Wrap Materials Often, when the net is cut at the end of the wrapping cycle in the baler, the single coloured thread will react differently to the rest of the net, creating the risk of the thread wrapping on feeding rollers.

 

Professional Agricultural Articles

The reasons for this problem can be many; such as a damaged net from poor handling when loading into the baler — creating broken threads that can be caught. More likely will be the poor cutting action in the baler as the net roll tension is not set correctly, which presents a slack web of net for the knife to try and cut, creating a poor and un-even net tail.

This series of pictures shows how easily one thread can be pulled from the netwrap web, splitting the net into two. The long franze thread in the second picture is typical of what might be found after a poor cutting action in the baler, which can quickly lead to the stitch being pulled out and the net separating.

damaged net damaged net
damaged net damaged net
damaged net

Very often, when this happens it is easy to see the franze thread having been pulled out of the net, making the net come off the roll in two or more pieces. Unfortunately, the loose thread can very quickly be caught up in the fast turning feed rollers on the baler, which will immediately begin to pull the entire net back onto the rollers causing it to wrap around the feed roller.

If the baler produces a bale with part of the net missing, as we have seen, the correct action would be to stop baling, remove the net tail from the baler feed system and pull off any net that has begun to split, cut cleanly and re-insert into the baler.

If the problem persists, the net tension system should be inspected and tension increased on the net roll to ensure the net is held tightly at the point when it is cut, this will ensure a clean and uniform cut of the net, avoiding long tails.