Fixed or variable bale chamber, which baler is best for me?

An important question to consider when purchasing a round baler or baler-wrapper: which type of bale chamber is most suitable? A fixed bale chamber with rollers, a variable bale chamber or a high density (HD) bale chamber that can produce a variable bale size? We have listed the advantages and disadvantages of each type of bale chamber below.  

Fixed bale chamber 

A fixed bale chamber is a round chamber with driven steel rollers that rotate and form a round bale. This is a reliable and easy method of producing a good bale. A fixed chamber baler will still produce a good bale even under difficult conditions, for example, with short or wet crops.  

When the bale chamber is being filled, the operator can use the full intake capacity. The baler will only start to compact the crop when the bale chamber is almost full. After being wrapped, the bale is ejected quickly to start forming another new bale. This means that a fixed chamber baler wrapper has a high capacity.  

Due to the maintenance-friendly, reliable concept and its user-friendliness and high capacity, an advantage of a fixed chamber baler is the low cost per bale. However, the disadvantage of a fixed bale chamber is that it offers no versatility in bale diameter, and compared with a variable bale chamber it is more difficult to create good bale density with drier crops such as hay and straw.  


  • User-friendly method; easy to produce a good bale 
  • Extremely reliable concept with fixed rollers 
  • Good cost price per bale 
  • Low power requirement 
  • High capacity
  • Very suitable for short and wet autumn crops 


  • Variable bale diameter not possible 
  • Less suitable for drier crops such as hay and straw compared with a variable bale chamber 
Bale chamber of a fixed chamber baler

Variable bale chamber  

A variable bale chamber has a combination of fixed rollers and adjustable belts that can increase the size of the chamber. Baling pressure is built up from the core until the desired diameter is reached. It is also possible to set whether the bale should have a soft or hard core and a soft or harder outer layer. The variable concept also has a better ability to produce a good bale with a high density from dry crops such as hay and straw.  

With a fixed bale chamber, the last bale to be formed might not have filled the bale chamber, so the final bale is not as firm. A variable bale chamber can compact and bind the bale well even if the chamber is not completely full.  

A variable bale chamber excels in versatility. It can produce bale silage with a diameter of 1.3 m in the morning, switch to forming smaller hay bales in the afternoon and finish with large straw bales in the evening. All possible with the same machine. 

A variable bale chamber is easy to use but demands a little more experience to produce the perfect bale. Especially in wet conditions, it can be more difficult to produce perfect bales.  


  • Variable bale size possible, from small bales for horses to large straw bales, for example
  • A larger bale size can save money
  • Well-compressed bales from start to finish
  • Variable density from core to outer layer possible
  • More suitable for dry crops such as hay and straw
  • Exceptionally good cost price per bale
  • Low power requirement#


  • The operator will need a little more experience to produce perfect bales 
  • Less suitable for extremely wet autumn crops  
Bale chamber of a variable chamber baler

Variable HD bale chamber

n 2022, KUHN introduced a variable high density (HD) baler-wrapper: the VBP 7100 series. This model combines the advantages of a fixed and variable bale chamber in one machine. It can bale extremely wet crops in the same way as fixed bale chamber, but it can also bale hay and straw with an extremely high bale density. The intake is designed to fill the bale chamber quickly in the same way as a fixed bale chamber. The bales are also ejected at the same speed as a fixed chamber thanks to a special bale chamber concept with two tension arms. This allows the tailgate to open and close quickly, and the belts are immediately tensioned ready to start forming a new bale. This innovative technology means the machine can easily create perfect bales in all conditions.  

An HD baler-wrapper can form bales with extremely high densities. As a high bale density contains a higher volume of crop, high forage quality and lower transport costs are guaranteed. The heavy-duty construction of the bale chamber makes the machine extremely robust. The machine is over-dimensioned, so if a standard bale density is used, the machine’s service life will be extended further.  

However, the price of a baler-wrapper with a variable HD bale chamber is higher than a model with a standard bale chamber. A larger tractor is also needed to utilise the high capacity of this heavier machine.    


  • Combines a standard fixed bale chamber and a variable bale chamber in one machine: 
  • Variable chamber enables variable bale size 
  • Innovative technology makes creating a good bale shape easy 
  • Suitable for short and wet autumn crops  
  • The variable chamber is also extremely suitable for dry crops 
  • High capacity  
  • Heavy-duty construction 
  • High bale density 
  • High forage quality  
  • Lower transport costs  
  • Extended machine service life if used for standard bale density 


  • Higher investment
  • Larger tractor required compared with a fixed or standard variable bale chamber
Bale chamber of a high-density baler

Also read: 

    • How does KUHN make a good bale? 
    • Save costs with a larger bale diameter  
    • The advantages of a higher bale density 

Film Binding: more economical and greater preservation

Film bound bales, using 3D wrapping and Intelliwrap, are better preserved than net bound bales. This is a key finding to a study carried out in 2021 and 2022, conducted by KUHN in cooperation with Eurofins Agro in Wageningen. In addition, the binding and wrapping costs for film bound bales are lower than bales bound in net.

In June 2021, 12 hectares of grassland were cut and baled to create two groups of bales.  

  • Group 1: bales bound with 2.75 layers of net and conventionally wrapped with 6 layers of film.  
  • Group 2: bales bound with 3 layers of film and wrapped with 5 layers of film using 3D wrapping and Intelliwrap.  

Whilst baling, grass samples were taken by Eurofins Agro. After 6 weeks of storage, samples were taken from both bale types for feed content analysis and for conservation analysis. Forage samples were repeated after 8 months of storage. In addition to sampling, when the bales were opened, a visual assessment was made for mould present and the location of any mould patches in the bales. Finally, the study included a separate comparison of the binding and wrapping costs of both bale types. 

Film bound bales promote consistent forage preservation

The main result of the study concerned the large difference in the butyric acid concentration between the two bale types after 8 months of storage. At 9.2 grams per kilogram of dry matter in net bound bales, this was clearly higher than the 4.9 grams per kilogram of dry matter in the film bound bales. According to Bob Fabri, feed and preservation expert at Eurofins Agro, this means that the preservation process of the film bound bales were better than with the net bound bales. Fabri: ‘To put it simply, butyric acid bacteria will dominate if the conditions are not favourable for beneficial bacteria such as lactic acid bacteria. The higher the butyric acid concentration, the poorer the process of preservation.’ In this context, Fabri emphasises the importance of ensuring there is as little air in the bale as possible when ensiling. ‘The faster the oxygen is consumed by the aerobic bacteria, the sooner the anaerobic bacteria can start their work and the less energy and dry matter it costs. This result shows that this effect was superior in bales bound in film compared with net bound bales.’ 

Minimal mould formation

Another key finding is that bales with film binding were practically free of mould formation. After the visual assessment, this bale type scored 9.67 on a scale of 1 to 10, with 10 being completely mould free. Net bales had a lower score of 6.95.  

The third conclusion is that the binding and wrapping costs for film bound bales are lower than for bales bound in net. Binding bales with film is more expensive than binding bales with net, however because the TWIN-reel binding system on the KUHN baler-wrapper uses standard rolls of stretch film instead of the more expensive mantle film, the additional costs are low. And, because a layer less of film is used in the wrapping process, the total savings on the wrapping costs are higher than the extra costs of film binding. 

Read more about the results: View Here 

Improved forage quality with film binding

Binding and wrapping a bale with film improves the quality of both the bale and the forage. In addition, multiple film layers improve the quality of sealing and limit the development of mould in the bale. Using the same film offers the additional advantage of having only one type of waste material and the bale is much easier to unwrap. 

The highest possible feed quality and the lowest loss of dry matter. Previously, it was standard practice to bind round bales with net then apply film layers with a wrapper. Nowadays, the combination of binding and wrapping, both with film appears to produce a better bale and therefore higher forage quality. 

As the bale is both bound and wrapped with plastic film, this eliminates the need for net completely. This film binding system uses standard 750 mm rolls of film – 60% of the bale is covered in film during the binding process and then the rest is covered by the wrapper.  

Film binding reduces mould development 

A pressure test has indicated that it takes air 160 seconds longer to permeate film bound and wrapped bales than bales bound by net. The bale is so airtight that mould has less chance to develop. Research1 also shows that the loss of dry matter resulting from mould in a net-wrapped bale (125 cm diameter) can reach more than 8.5 kg. In a film bound and wrapped bale, this is 80% lower (1.7 kg).  

Airtight bales with film binding 

To ensure forage quality, the influence of all external factors – including those of the bale – must be excluded. Using the same stretch film for both binding and wrapping creates an airtight bale that also retains its shape. By pre-stretching the film by 75%, it retracts like elastic around the bale, forcing out any air pockets and preventing from forming as the air has no way of penetrating the bale. Using the same film offers the additional advantage of having only one type of waste material to recycle and the bale is much easier to unwrap

Uninterrupted baling operations

The moment when bales are produced is critical. An uninterrupted baling operation is vital for the quality of the forage. Downtime is not an option, so in the event of a malfunction the part you need has to be on site as quickly as possible. KUHN Parts helps you with smart logistics and rapid delivery.  

The harvest season is a peak period for the entire contracting company. The planning has to be right; clients want their grass baled, the machinery operatives are working flat out and the balers are really put through their paces. No matter what the conditions, the machinery has to keep running. If a tractor breaks down, it’s often relatively easy to organise a replacement, but locating a spare baler is a different matter. Downtime costs money, but that is not the main issue. As an agricultural contractor, the last thing you want is a dissatisfied client. Due to time pressure, a client will just as easily switch to another contracting company. Winning back their confidence is a challenge.  

Prevention is better than cure 

The KUHN dealer is your main partner for maintenance and repairs to your baler. The dealers are trained professionals and have all the necessary tools available. That is a very relevant point: ordering a spare part is one thing, but replacing it is something else. KUHN dealers have the necessary knowledge and expertise. The same applies to the winter maintenance check. During this check, every part of the baler is inspected and components susceptible to wear are also checked. These include the pre-stretcher rollers, oil filters, the driveline, knives, wrapper table belts, chains and chain sprockets. This inspection is performed with the greatest care. Despite this, one of the parts may need replacing during the harvest season.  

Parts are never far away

The complete range of spare parts is stored at KUHN in Saverne, France. The 26,000 square metre warehouse holds 80,000 parts in stock. Parts can be shipped from the warehouse 24/7. And to prevent the baler from unnecessarily long downtime, KUHN dealers always have the most common wear parts in stock. So never too far away. If a dealer does not have a certain part in stock, the KUHN SOS Order can help. The dealer can place an urgent order and the part will be supplied the next day by express delivery. If the delivery is less urgent, the dealer can use KUHN i search to contact other approved KUHN partners around the world to find the right part.  

As well as the services provided by the dealers, KUHN users can also arrange a lot themselves. Via the online MyKUHN portal you can order parts quickly. If you place an order in MyKUHN, your own dealer will be notified and can ensure the parts are sent to you as quickly as possible. Signing up to MyKUHN is free. To sign up, simply register using the serial number of your baler or other KUHN machine.  MyKUHN offers users many other benefits such as access to operator’s manuals and your settings and maintenance information. 

KUHN is ready to serve you and your client 

During the harvest season what really counts is minimum downtime and a satisfied client. There’s no need to use your time and energy finding and ordering spare parts – KUHN Parts can arrange it for you. Via the KUHN dealer, MyKUHN or via an express order.  

Discover KUHN Parts:


Also read: 

  • How does KUHN make a good bale 
  • Save costs with a smart approach to wrapping 
  • Weighing bales delivers accuracy and insight 

Save costs with a smart approach to wrapping

Every layer of film wrapped around a bale is one, and every layer of film costs money. Taking a smart approach to binding and wrapping film will deliver you some significant savings. On top of that, binding with film offers multiple advantages.  

Using six layers of film as standard in order to ensure the bale is sufficiently sealed and protected is often what you see in practice. But various factors influence the maximum number of film layers the bale actually needs. The guideline is: the drier the crop, the more layers of film. If the crop is wet, it’s probably fine to use fewer layers of film for wrapping. In addition to moisture content, the intended storage period is an important factor. After all, the more layers of film, the better the oxygen barrier so oxygen takes longer to reach the forage in the bale.  See the table below for our recommendations.

Good film for minimum air permeability 

In all cases, high quality film is vital for good preservation of the bale. Plastic wrapping film is never 100% airtight, but good film is characterised by minimum air permeability. Using lower quality film will affect how the crop is processed in the baler-wrapper combination and the overall forage quality. In addition, cheaper film increases the risk of forage losses, as air can penetrate the bales faster so to compensate for that, you need to use more layers of film to wrap the bale. 

Low costs with the same film 

Binding bales with net has been standard practice for years. However, film binding has been gaining ground on using net in recent years. And with its rise in popularity, the benefits of film binding are also becoming more evident. For example, a bale bound with film is more dimensionally stable, easier to open and has more oxygen-tight coverage. In addition, the farmer only has one type of waste material that is easy to dispose of. However, all benefits come at a price. Compared with net binding, binding a bale with film is up to €1 more expensive2. However, if the same film can be used to bind and wrap – as is the case with KUHN balers with film binding – this extra cost can be reduced to €0.50. If you decide to change from the standard six layers and take the condition of the crop material and storage conditions into account more, you can apply a total of five layers. This means the cost is identical to a net tied bale plus six layers of film wrap. And with young crop material with a sufficient sugar content3, you can even get away with using a layer of film less!   

How does KUHN make a good bale?

The KUHN FBP (fixed chamber) and VBP (variable chamber) baler-wrapper combinations have a number of unique features that always create the perfect round bale. Even cutting quality, correct bale density, consistently filled bales, stable shape retention and firmly wrapped are what you can expect from bales produced by the KUHN FBP and VBP series.

Making a good bale is not easy in all conditions. We will address the main components of KUHN baler-wrapper combinations that contribute to a good bale despite changing crop conditions.

KUHN INTEGRAL ROTOR for quick and optimal crop intake

The pick-up tines cleanly collect the grass and feed it directly into the INTEGRAL ROTOR. The large augers on both sides of the rotor force the grass through the OPTICUT cutting rotor. This integral rotor facilitates a more consistently filled bale, uniformly filled right to the sides. The integral rotor is located just after the pick-up unit. This short distance maintains a short and compact inlet channel which guarantees quick crop intake.

After the rotor, the grass passes through the OPTICUT cutting system. Two options are available with a maximum of 14 or 23 knives. The operator can pre-select the number of knives used by retracting some of the knives in the inlet channel. Baling without knives is of course also possible. The knives are individually protected against foreign objects. This gives better cutting quality with as large crop throughput as possible and reduces the sensitivity of the knives to foreign objects. Less downtime and a better cutting quality.

KUHN bales retain their round shape

After the cutting system, the grass is fed into the bale chamber. In the balers with a variable chamber, the triangular starting chamber and the PROGRESSIVE DENSITY system guarantees the bale always forms correctly. The belts apply pressure on the bale from the starting core to the outer layers, maintaining a consistent bale pressure throughout the entire baling process, ensuring tightly formed bales that retain their shape. This ensures that a good, round bale can even be made with short, dry silage. Thanks to the variable chamber design, you can set the bale diameter yourself to range from small and manageable bales to large bales with savings on (wrapping) film.

The fixed bale chamber is designed with 18 fixed rollers, allowing the bale to rotate immediately as the chamber is filled. Sensors in the hydraulic tailgate cylinders help to achieve the correct bale density, bale size and bale fill (left/right). Binding the bales on both the FBP and VBP balers can be done using either net or film.

Film always correctly positioned thanks to the KUHN 3D wrapping system

After binding the bale, it is quickly transferred to the wrapping table without being damaged. This is particularly important if film binding is used. For this reason, after film binding, KUHN uses guide rollers on the bale transfer system that ensure the bale is transferred undamaged straight onto the wrapping table, then wrapping can start.

All VBP and FPB balers can be equipped with the optional, innovative 3D wrapping system. The rolls of film rotate a quarter turn after which the bale is first wrapped around the cylindrical part and then around the flat ends. The result is an evenly wrapped bale that retains its shape better than a conventionally wrapped bale. The 3D wrapping system ensures the film is correctly positioned and evenly distributed over the bale and the vulnerable bale shoulders are well protected. Thanks to the low height of the wrapping table, the bale can then be safely discharged without dropping or deforming it. This will ultimately benefit the storage capabilities of the bale.

Winter check your round baler

Reliability is one of the most important requirements of your baler-wrapper combination. The machine is needed every minute of the short time window. Nothing is more frustrating than downtime in the middle of the harvest period. Therefore preventive maintenance in a quiet period of the year is highly recommended. 

Preventive maintenance pays off

Replacing parts and replenishing oils and lubricants during maintenance is significantly cheaper than performing repairs that result from deferred or overdue maintenance. Thanks to good and timely maintenance you save costs in the long run. 

Winter Checklist for combi balers 

What exactly needs to be done during a check is listed in the manufacturer’s maintenance instructions and maintenance intervals. These can be found in the user manual of your machine. To make it even easier for you, we provide you a Winter Checklist for KUHN FBP and VBP combi balers.  

Download the PDF and you will know exactly which points to check and where to find additional information.  

Checklist KUHN FBP 

Checklist KUHN VBP 

Also read: 

Square balers maintenance kits

Square balers maintenance kits: start in pole position for the new season

How can I be ready for the new season?

With a tight harvest window, you need to rely on a large square baler that offers the highest productivity and reliability to get the job done, season after season. KUHN understands your need for uptime.

With the new KUHN SB Maintenance Kits you are always one step ahead, making preventive maintenance easier and saving costs simultaneously. Choose the right kits depending on your situation and get everything you need to start in pole position for the next season.

In this kit you can find wear parts and technical parts, to ensure that you have all the products you need for the best results with your square balers

What are my advantages?

– Maximum operational reliability

– Increased lifetime

– Ease of use as e box contains everything you need

– Cost savings due to volume discounts

– Easy ordering via

Where can I find the maintenance kits?

Contact your local dealer today – Locate your nearest dealer