Abstract: The multi-body dynamics is widely used in the current research of the digital prototype of precision plastic injection molding equipment, without considering the stress and its distribution of components in the motion of closing mechanism. Therefore, it is difficult to solve the mutual coupling problem between the large displacement of the mold movement and the small displacement of the structural deformation. For the complex dynamic characteristics of precision plastic injection molding equipment, the digital prototype of double toggle mold closing device is established with flexible parts of tie bars, crosshead rod, front elbow bar and pin, then, before order 22 modes of tie bars can be obtained. In the simulation analysis of digital prototype of mold closing device, there is a velocity turning point of crosshead rod in the starting procedure, which needs to consider the elastic deformation of the crosshead rod. In the rigid-flexible coupling dynamics analysis of double toggle mold closing device, by using the central difference method, the elastic deformation of crosshead rod is resolved in the starting procedure, and a reference method is provided for the development of precision plastic injection molding equipment.

Key words: Digital prototyping, Mold closing mechanism, Rigid-flexible coupling, Twin toggle three links type