Apple, which occupies the first position in the world with regard to its yield, is an important economic crop in China. Pruning of apple trees is still dominated by manual pruning, resulting in high labor costs and low efficiency. Additionally, there are some limitations with pruning machines. Thus, research regarding the mechanical properties of apple branches is the basis for the designing proper pruning machine. This paper aims to study the effect of the feed rate, cutting line speed, branch diameter, and moisture content on the cutting force. Results revealed that cutting force depended on the feed rate, cutting line speed, and branch diameter. Furthermore, both the cutting line speed and the branch diameter had a significant effect on the cutting force (p < 0.01), while the feed rate had a small effect on the cutting force (p > 0.05). However, the moisture content had no effect on the cutting force, with a difference of cutting force between samples with moisture content of 15% and 50% less than 5%. Based on the experiments performed, an equation relating the feed rate, the cutting line speed, the branch diameter was derived to calculate the cutting force. By verification test, it established that regression equation was valid with error less than 4%. This study explored the mechanical properties of apple branch, and obtained the optimal cutting parameters, which can provide a reference for the design of the pruning machine.

In the biomass densification process, a lot of energy is needed to prevent its spring-back and to overcome the friction between the material and the channel surface of the die so as to build up pressure. However, moisture, particle size, temperature, and type of material all influence the densification pressure, pellet quality, and the density. The research was aimed to find out how the densification pressure and density were affected by the die temperature based on an open-end densification method using a self-developed pellet extruder. When the piston fixed in the front of the extruder moved in a reciprocating way, the raw material was pressed into the opening die, which had a heater wrapped up. Crushed corn straw with a particle size under 4 mm and with a given moisture content of 10% was used to be compacted by the extruder. The results showed that with the increase of the die temperature, the value of densification pressure decreased; however, the quality of pellets was not good at temperatures higher than 140 °C. The proper temperature for corn straw densification was 100 °C, and the value of the unit density was above 1.0 g/cm³. Meanwhile, the surface quality of the pellet was comparatively good. The reference values of the friction coefficient at different temperatures were provided.