Design and parameter optimisation of a cotton straw crushing device based on DEM-MBD

• The dynamics of the straw crushing process were analysed. • A straw crushing mechanism for a split-type residual film recycling machine was designed. • A simulation test of the straw crushing mechanism was carried out using MBD-DEM. • The results of the simulation experiment were analysed, and the optimum parameter combination was determined. To address the problems of structural complexity and unsatisfactory crushing qualification rate in existing integrated machines for straw crushing and film recovery, a cotton straw crushing device suitable for a split-type film recovery machine was designed. Parameter optimisation of key components was carried out using a coupled DEM–MBD simulation approach. The device adopts a novel 2L+1 straight-knife rotor configuration, consisting of 132 L-shaped blades and 66 straight blades arranged in a double-helical pattern to enhance crushing performance. A dynamic analysis of the longitudinal cutting, follow-up motion and chopping phases of the straw was conducted to identify the factors that influence the crushing qualification rate. A machine–straw–soil coupled discrete element model was developed, and single-factor tests were conducted through EDEM–RecurDyn co-simulations. The optimal operating ranges were identified as follows: machine forward speed of 6-8 km/h, rotary shaft speed of 2200-2400 r/min and blade length of 155-165 mm. A three-factor, three-level orthogonal test was designed using the Box–Behnken method based on these ranges. Response surface methodology was applied to determine the optimal combination of the operating parameters: forward speed of 7.88 km/h, rotary shaft speed of 2280.5 r/min and blade length of 160.24 mm. Field validation showed that the straw crushing qualification rate reached 91.82% under these parameters, meeting regional agronomic requirements. The proposed split-type crushing unit effectively meets the operational needs for cotton straw processing in the Xinjiang region, providing a practical solution to the challenges of mechanical complexity and maintenance difficulty in combined straw crushing and film recovery systems.