Research On Optimal Design Method Of Spindle Flexible Drive System Of Large CNC Gantry Milling Machine

For large CNC gantry milling machine, the spindle is the most important part of theentire milling and directly related with the machining accuracy and milling machine life.The gantry milling spindle is mounted in the ram, and is directly connected with the driveshaft. The other end of drive shaft connected to the reducer, and the reducer is connectedwith the driving motor. The rotational movement of the drive motor is passed to the spindleby drive shaft. Therefore, the structure and performance of spindle drive system and thedrive shaft will directly affect the overall performance of the milling machine. Ram driveshaft is long and generally more than two meters, so the center of the drive shaft at bothends of the support is difficult to ensure complete alignment. After processing andinstallation, if occurs misalignment, and because of the traditional drive shaft is rigid driveshaft, will cause a lot of stress and have a large radial force at the support, seriouslyaffecting the normal operation of the unit and causing vibration or shaft off. And two setsof bearings support the drive shaft in the traditional ram. When occurs misalignment, shaftand bearing force uneven in a long time to interact wear. So it often brings more bearingwear and seriously affects the normal operation.This paper adopts good toughness, high strength titanium alloy (TC4) instead of thetraditional material, to design a flexible drive shaft instead of the original rigid drive shaftand remove the support bearings at both ends of the original drive shaft. Then it becomesfrom a rigid transmission system into a flexible transmission system, and to improve theprocessing of the structure. And it can reduce the difficulty of processing and installation.In this paper, by the actual situation of the studying subjects, using the singularfunction and the Laplace transform method calculated the expression of reaction forces andbending deformation and the expression of the relationship of the total corner and thetransition curve when the drive shaft respectively is in cross and parallel misalignment.The expression is regulate and unified, suitable for optimizing design and easily to program.In this paper, firstly, using traditional mechanical design methods design the basicparameters of the drive shaft. Then the finite element analysis technical apply to theselection of the transition curve to select the appropriate transition curve. Finally, bymechanical optimization design method, optimize shape the structure and performance ofthe drive shaft.By the VB programming to calculate the total optimization process, and simplifies thetedious process of calculation. The interface is simple and easy to operate, and the resultsare visually displayed. The program has general applicability, applicable to other differentseries ram drive shaft design.