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Abstract
Tube spinning is an effective and advanced chipless method in manufacturing of long thin wall axial symmetric tubes. Tube spinning process offers an increase in tensile properties and provides an excellent dimensional accuracy and surface finish. In these investigations a Numerically Controlled (NC) tube spinning machine has been built through designing and installing the tube spinning tools on a conventional lathe machine to convert it from turning process to tube spinning process. Then, by applying the retrofitting techniques, it has been converted to NC tube spinning machine in order to carry out a series of experiments for optimizing the quality characteristics of the tube
spinning products.
Designing and installing tube spinning tools involved replacing the tool post of the Lathe carriage by a rollers holder with three rollers fed radially. A mandrel is mounted on the Lathe chuck to carry the preform. The retrofitting process involved driving the radial feed of the three rollers by a DC motor unit. The mechanical control system of the carriage is also replaced by an AC motor with variable speed drive. The overall control of the units is accomplished by a Programmable Logic Control (PLC) system
ID programmed through LOGO\- software.
A series of experiments has been carried out on the retrofitted machine and tube spinning process has been performed on A9 1050 Aluminum preform. The quality characteristics of the spun tubes such as surface roughness, thickness uniformity, surface hardness and ultimate tensile strength have been measured over a range of axial feed rates, rotational mandrel speeds. percentage reductions of wall thickness and different lubricant types. The effect of the significant parameters on the measured quality characteristic has been evaluated using Design Expert’ID software. Furthermore, the optimum working parameters leading to best individual and total quality characteristics for the existing machine condition and preform material have been established, which were not included in any previous investigations. The results show that the axial feed rate, mandrel speed and reduction per pass are the most significant process parameters that affect the quality characteristics of tube spinning products.
A three-dimensional elastic-plastic Finite Element Model (FEM) for three-rollers forward tube spinning of a cylindrical workpiece has also been developed and simulated using an ABAQUS’S! software package. Simulation of the FEM included real working conditions such as the rotation of the preform, axial movement and the passive rotation of the rollers, which were not included in many previous investigations. The model has been run under the optimum and different working parameters.
Stresses and strains distributions in circumferentiaL radial and axial directions have been estimated. In addition, some of the process phenomena such as (build-up, bell mouse and bulging between rollers), and defects that may arise during actual experiments such as (thread-like serrations and spoiled surface) have been detected. Furthermore, the ranges of feed. speed and percentage reduction per pass at which the previous defects appear, have been determined. The FEM results show that most of the process defects appear when using too low feed rate (less than 0.15 mm/rev), too large feed rate (more than 0.75 mm/rev) and high percentage reduction per pass
(more than 30%).