Dynamic analysis on fabricated mineral cast lathe bed

Abstract

Vibrations transmitted into the machine tool structure made of cast iron cause chattering and develop positional errors between the components during machining operations, causing dimensional inaccuracy and poor surface finish for the products manufactured from them. As an alternate material for cast iron, mineral cast epoxy granite structures are found to exhibit good mechanical properties such as high stiffness and damping ratio at a lesser weight. This study attempts to fabricate an epoxy granite lathe bed having same stiffness as that of a cast iron microlathe bed, and the dynamic characteristics of both the beds are compared. The dimension for the epoxy granite bed is obtained through analytical and finite-element method analysis such that it has same stiffness as that of a cast iron microlathe bed. Modal analysis is conducted to determine the dynamic characteristics of the lathe fabricated. It is found that the damping ratio is improved by 2.2 times for the fabricated epoxy granite bed. In addition, a weight reduction of about 38.64% is observed for the epoxy granite lathe bed in comparison with same-stiffness cast iron bed. To verify the dimensional stability of the fabricated epoxy granite bed, oil and water immersion tests are conducted on test specimens and no change in the dimensions is observed. It is observed that epoxy granite is a promising alternative material for fabrication of advanced machine tool structures.