Hay Pellet Machine – Die and Roller

The carpet in hey pellet machine is a thin layer of compressed material, which sits on top of the die surface. As material goes into hey pellet machine, it gets pulled beneath the roller and forms a carpet. As more material is placed in the pellet machine, this is then added to the carpet. The bottom of the carpet is then forced through the die holes, as the process continues, results in a pellet. So for the material to be able to form a pellet, it must first be able to form a carpet.

1mm Gap
Generally, a 1mm carpet is regard optimum for most biomass materials such as hay to give the correct balance between pellet quality, energy input and wear of pelleting machine. Increasing the gap from 0 to 1mm increases the energy demand by 1.2 folds. However, fines are reduced by up to 30% and die and roller wear is reduced.

>1mm Gap
The larger the gap between the rollers and die, the greater the energy input required.
If the rollers are set above 1mm, there may not be enough pressure generated between die and rollers in the hay pellet machine. Without pressure, there is no heat, no binder is released and a carpet cannot form, thus a hay pellet cannot form.

<1mm Gap
As the rollers and die touch, there is no room to form a carpet, so material such as hay is forced directly through the pellet machine die holes, and the quality of the pellet is reduced. More importantly though there is metal to metal contact, it significantly reduces the life of the roller and die plate.
When setting roller gaps the characteristics of the material need to be considered, for example, hay density and binding properties. A 1mm gap is recommended for most materials, including hay; however, experimenting with different gaps with certain pellet making machine could be beneficial.

Die and Roller Life
Die and roller life is dictated by several factors. Firstly, the die metal will influence abrasive resistance and breakage resistance. Abrasive raw materials lead to shorter die and roller life. The roller gap also affects the life of pellet machine consumables. If the rollers and die touch and there is metal-to-metal contact, this will increase wear, leading to a shorter life. Finally, the speed of the pelletizer including hay pellet machines influences to die and roller wear. With care hundreds of hours of use can be obtained.