Cutting teeth of a dual-cone double enveloping hourglass worm wheel hob retain land surfaces with a certain width to increase the service life of the hob because this kind of hob cannot be re-sharpened. The land widths from the top to the root of all of the cutting teeth should be uniform so that all of them have the same cutting performance. However, the accuracy and the uniformity of the land width of the land surface of hob with spiral rake faces have not been studied till now. To solve this problem, this paper puts forward a method for designing the land surfaces of the hob with spiral rake faces and studies the accuracy and the uniformity. The spiral rake faces of the teeth of the hob are generated by a cylindrical surface. The offset surfaces of the spiral rake faces are obtained by offsetting the spiral rake faces along their normal vector directions with the offsetting distance equal to the land width. The rake faces and the offsetting surfaces intersect with the helical surfaces so the cutting edges and the land edges can be gotten, respectively. The land width of each cutting tooth is the distance between its cutting edge and its land edge. The results of a numerical example show that the calculated land widths on the pitch torus decrease firstly and then increase from one end to another end along the axial direction. The difference of the calculated land widths between the top and the root is larger at side teeth than that at middle teeth. The calculated land widths are slightly larger than the given one and all the calculated land widths change within a small range that can be ignored. Therefore, the method can keep the accuracy and the uniformity.

In the design of corn combine harvester, there is a high demand for customization and diversification in China. Aiming at the problems of backward design method, lack of design knowledge and long product development cycle, the discrete beam method is used to establish the corn plant model. The model of sub-device and the vertical and horizontal roller picking device is established by using UG, and the virtual prototype model is established by using ADAMS software. Meanwhile, the simulation experiments on the kinematics and dynamics performance of the separating device, the corn plant and the picking roller are carried out, and the simulation results are verified by field experiments. Through this method, the design parameters of the separating device and the picking roller are serialized, the method of evaluating the separating performance and the picking performance is provided, and the development and design cycle is shortened, which provides certain reference and theoretical basis for the development and design of the corn harvester header.