Hydraulic Roll Gap Control And Analysis For Failure Of Spindle In Vertical Miller Machine

The vertical edger with bottom drive is attached to the entry side of the reversing roughing stand.The edger rolls is driven by one vertically arranged motor each through helical spur gears and vertical universal spindle.The edger consists principally of the horizontal mill housings,the roll chocks with built-in edger rolls,the spur gears on top,the full hydraulic screw down system and the roll balancing system.The heavy duty cross-pin joint of the universal spindles for the No.2 vertical edger(E2)was broken for two times in one and half years in one hot rolling plant.So it is necessary to study the hydraulic roll gap control system and factors of causing the this kind of failure,i.e.the working conditions and structure design.This paper first studies the working principle of hydraulic roll gap control for E2 mill,then PDA curve of the driving system for E2 was studied,and the negative torque impact was found.The stress of the E2 Spindle tends to be reasonable by optimizing backward slip value in the rolling model of the No.2 roughing mill(R2).And the "pulling" effect from the R2 was released during the rolling process.On the other hand,by using the finite element method,the strength of the spindle was calculated.The conclusion shows that the design strength of the conventional joint is more than the actual strength,but the safety factor is not enough.By comparing the other production lines,and studying torsional vibration of the vertical edger,we proposed to increase the joint design strength,and completely solved the vertical roller spindle failure problem.This paper creatively applied PDA curve of the driving system,studied the dynamic stress of the spindles and cross-pin joint for E2,found the causes of failure with the conventional strength calculation,provided a theoretical basis and experience for solving this kind of failure problems for the driving spindles.