Design criteria study and simulation for underactuated symmetric pinching mechanism of pinch roll machine in high-speed wire rod product line

Inspired by the underactuated robotic hand mechanism and its feature of shape adaptive and compliant envelop grasping, the paper presents an underactuated symmetric pinch mechanism to solve the problem of pinch rollers idle and slipped or pinched too tightly. Pinch roll machine is a key device in the high-speed wire rod product line. It is usually designed with actuated symmetric pinch mechanism. The paper considered the pinching and conveying condition of linear objects and discussed the possibility of the underactuated symmetric pinch mechanism to be applied in the pinch roll machine for the first time. Three kinds of underactuated symmetric pinch mechanism solutions are presented. A displacement can be generated at the underactuated joint when the symmetric synchronous pinch action is implemented. The spring system can buff the instantaneous clamping force to reduce the dynamic impact of clamping force. Suitable design criteria are deduced from statics and kinematics analysis. In the process of pinching and conveying wire rods, the contact force is required to be kept at a constant value when the size of wire rods changes. Thus, it can protect the rod from being damaged while pinching and conveying and it can avoid the fatigue damage caused by excessive pinching impact force. Then, the pinching and conveying conditions of four different kinds of variable diameter wire rods are analyzed through 3D modeling and motion simulation experiments. Simulation results show that the proposed underactuated pinching and conveying mechanism can satisfy shape adaptive pinching and conveying irregular long-shaped wire rods. The research method is novel and feasible. The design result will be beneficial to improve the service life of the pinch roll machine.