Comparison of Variants of Tube Straightening Machine Frames Using Finite Element Analysis

Tube and pipe straightening machines are used in the final phase of the tube manufacturing process. These straighteners ensure the straightening and adjustment of tubes produced by rolling, welding or other types of production. The basic requirement placed on tube straightening machines is that they must produce the most accurate possible tubular semi-product in the highest possible quantity and at the lowest possible cost. This ideal requirement is influenced by many undesirable factors that affect the entire straightening process and make this finishing operation a very complex problem. In this paper, the main attention is paid to the stiffness of the frame of the straightening machines, which is one of the most important factors that fundamentally influences the quality of the final product. There is a wide variety of types and designs of straighteners and this paper especially deals with a computation and comparison of 3 different frame types of six-roll tube straightening machines with cross axis. The straightening force of the rolls is exerted by hydraulic cylinders - every roll is pressed by its own hydraulic cylinder. To ensure the unequivocal comparison of the individual variants, all rollers are loaded by uniform straightening force. Finite element method (FEM) analysis of this problem was performed using MSC Marc 2011. Computational models of all straighteners were created for this numerical analysis. The frame geometry of all straighteners is symmetrical, and the load is also symmetrical, therefore, only half of each frame was modelled. The aim of this analysis was to find the frame with highest toughness.