EFFECT OF PITCH AND NOMINAL DIAMETER ON LOAD DISTRIBUTION AND EFFICIENCY IN MINIATURE LEAD SCREW DRIVES

Vikrant Karmarkar, S.G.Jadhav, Rajesh Parab

Abstract: Lead screws are the devices which are used for power transmission or to have linear motion. It is theoretically assumed that applied load is evenly distributed among the thread pair in contact. However, practically it is observed that load is not uniformly distributed among threads. The first thread carries the maximum load and later the load on each thread reduces. Numerous studies have been carried out for analytical calculation of the load distribution using spring stiffness method. But these studies are for screw and nut combination. Not much study has been done to find load distribution on threads of a lead screw. The maximum load acting on one thread is an important parameter in lead screw design. The load decides the fatigue life of the screw and nut. To have better life of threads, the load distribution should be uniform to have fewer loads on single thread. The load is also important to know the deflection of thread which affects the positional accuracy of the lead screw drives. This paper focuses on analyzing mathematically the various thread parameters which affects the load distribution in threads and the corresponding effect on efficiency. The spring model method proposed in [1], [4] has different constant coefficient which are depending on thread geometry and material. If there are n numbers of threads in contact, there will be (n-1) number of equations in (n-1) unknowns. These are linear difference equations and can be solved by matrix elimination method. The results obtained from analytical solution are validated with the FEM (Finite Elements Method) results

Keywords: Lead Screws, Load Distribution, Thread Parameters, Efficiency, Linear Drives

DOI: https://doi.org/10.15623/ijret.2016.0504054