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.  

Advantages: 

  • 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 

Disadvantages: 

  • 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.  

Advantages:

  • 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#

Disadvantages: 

  • 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.    

Advantages:

  • 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 

Disadvantages: 

  • 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 

Costs savings thanks to a larger bale diameter

A baler-wrapper with a fixed bale chamber produces round bales of approximately 1.3 m in diameter. A baler-wrapper with a variable bale chamber can bale and wrap bales up to 1.6 m in diameter. This flexibility can be extremely useful, and a larger bale diameter can result in a lower cost per ton of forage. 

A round bale with a larger diameter: a calculation example

Take a bale of 1.3 m in diameter and 1.2 m wide that is bound with three effective layers of film, then wrapped with six layers of film. The three effective layers of film binding cost €1.27 with the KUHN TWIN-reel system. This calculation is based on standard wrapping film rolls of 1500 metres that cost €99 each. The six wrapping layers cost a total of €4.50 for film. This adds up to a total cost per bale of €5.77 for film.  

If the same calculation is made for bales with a diameter of 1.45 m, the costs for film binding are €1.38 and the six layers of film for wrapping are €5.37 per bale. This brings the total cost of binding and wrapping a bale to €6.75. This is an increase of 17% compared with the 1.3 m diameter bale. However, in this case the volume of crop in one bale is higher. A 1.3 m bale converts to 1593 litres, while a bale of 1.45 m in diameter has a volume of 1982 litres: that is 24% more crop per bale. If you calculate the costs of film per cubic metre, the result is €3.62 and € 3.41 per m3 of crop respectively. That represents a saving of 6 %. A bale of 1.6 m in diameter has a volume of no less than 2413 litres. So, the savings are even higher! In total, 13 % lower costs for film per m3. However, in practice it is more difficult to transport bales of 1.6 m and they can be quite heavy.  

Calculation example 1.45 / 1.6 m bale diameter compared with 1.3 m

Bale diameter   Bale volume  Increase in bale volume compared with 1.3 m  Film used per bale  Film costs per m3  Bale handling costs  Output 
1.3 m  1.59 m3           
1.45 m  1.98 m3  + 24%  + 17%  – 6%  – 20%  + 3% 
1.6 m  2.41 m3  + 51%  + 31%  – 13%  – 34%  + 4% 

Table 1: Calculation example difference 1.45 / 1.60 m bale diameter compared with 1.3 m bale diameter  

Save film and time  

Let’s take a farmer who produces 2000 silage bales with a diameter of 1.3 m per year as an example. If this farmer decides to produce 1.45 m diameter bales using a variable baler-wrapper, the same volume of silage will fit into approximately 1600 bales. That converts to 400 bales fewer a year.  

The total savings on film for this farmer are €688 a year.  

An additional benefit is 400 fewer bales that need to be loaded, transported and stacked, plus the baler operator can stop 400 fewer times a year to bind and eject a bale. And as less film is used, the total number of times the film must be changed on the binder and wrapper is significantly lower.  

Advantages of a larger bale diameter: 

  • Saves on net and film costs 
  • Using less net and film reduces the time spent on changing net and film 
  • Fewer stops to bind and eject bales 
  • Fewer bales to load, transport and stack 

Also read: 

Opening round silage bales: net versus film

Which bales are faster to open: net bound bales or film bound bales? To find this out we took up the silage bale opening challenge!

Film bound bales easier and faster to open

We opened a round grass bale bound with net and one bound with film. The outcome is clear: the film bound bale could be opened way easier and faster, without loss of forage due to it staying in the net. Moreover, a film-on-film bale has only one residual product which makes waste management more efficient.

Curious how we conduced the test? Watch the video:

Also read: