Cane damage and mass losses for conventional and serrated basecutter blades

Modern sugarcane harvesters use a double disc basecutter with multiple straight blades. These blades cut the cane at its base by an impact cut where the force against the stalk is essentially normal, causing cracks and splits that may divide the first two billets into one or more parts when the cane is chopped. These parts are easily carried out with trash, causing significant cane losses in terms of both volume and quality. A cut using a curved blade edge has been suggested to avoid the impact cut, but a backward curved plain blade edge can push the cane aside without cutting it. Serrated edges might represent a solution to this problem. An initial investigation has shown that although serrated edges are in common use and retain their cutting ability much better than plain edges, very little has been established about how they work and how they should be designed. This paper describes an investigation into the cutting ability of serrated edges and a comparison of straight and curved smooth edges. The sugar losses during the cut were measured by the weight of the cane before and after the cut, and a qualitative scale measured the degree of damage. A correlation was derived relating damage and losses. Despite the better cutting ability of serrated edges, sugar cell losses were greater, but cracks and splits in the stool and stalk were smaller. After the blade has started the cut, there is contact between the blade and the cut surface of the cane. The roughness of the serrated blade surface removes more sugar cells than smooth blades, but there is significantly less damage to the stool and stalk. This work shows that serrated edges in combination with new blade shapes have the potential to reduce cutting damage. The juice losses which result are small and appear to be correlated with the degree of damage caused.