Abstract:The geometrical accuracy of multi-pass sheet metal spinning products is crucial in many applications. Aerospace, petroleum, and chemical industries motivated the development of modern spun components of complicated shapes with special functionality, but a substantial research lag exists behind this progress. Due to the localized plastic deformation involved, careful control of dimensions and form is required in spinning procedures. In this study, two sets of experiments were implemented for cup manufacturing using a retrofitted computer numerically controlled (CNC) spinning machine to identify the critical factors affecting product geometry and reveal their influence on the shape accuracy of the spun cups. The first set is a screening experiment to determine the most significant parameters and the second provides the optimum processing conditions affecting cup quality. The feed ratio, number of spin-forming passes, spinning ratio, and lubrication were found to have the most important effect on the geometry of the spun cups. Optimum quality with a higher processing speed (productivity) was achieved under a lubricated condition using a larger number of spin-forming passes at a high feed ratio, diminishing the commonly adopted rule of slow spinning for accurate products and reflecting a significance for state-of-the-art spinning practice. The findings of this paper introduce a basis for a spinning quality database.

This paper suggests a typical scheme for substantially low cost machine upgrading with regard to research and manufacturing activities through the integration of mechanical, electronic and software technologies. Computer numerical controlled (CNC) multi-pass spinning process is considered state-of-the-art nowadays in critical applications such as aerospace and automotive industries but equipment cost is still an issue. For the sake of novelty, accuracy and repeatability of spun products, a conventional lathe machine has been converted into CNC spin-forming machine by retrofitting to generate automatic tool paths in two axes for multi-pass spinning. Actuators and sensors necessary to provide controlled motion of mechanical elements such as mandrel, roller, and holder are selected to cope with the requirements of this incremental metal forming process. A CNC controller is integrated to the system with software to generate the tool path and G-code required for producing cups using the retrofitted machine. Rotational speeds together with longitudinal and transverse axes movements are calibrated. Backlash in power screws is evaluated and considered in the displacement control. Different tool paths including involute path can be generated using the developed control system. The machine has been used successfully to produce cups with high processing speeds and superior surface quality to that reported in the available literature. Based on experimental investigation under lubricated condition, the geometrical and surface quality with productivity was improved and an optimum exists at 0.6 mm/rev. feed ratio, 200 RPM mandrel rotational speed, and seven spin-forming passes.

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Open-cell Al-Si foam samples were produced using infiltration casting technique. The metal infiltration process was performed in a specially designed and built setup consisting of a vertical chamber resistance furnace, a pressurization chamber connected to an Argon gas cylinder through a control manifold. To control the relative density of the produced foams, non-compacted and compacted preforms (5 MPa) were prepared from 2 or 4 mm NaCl particles. The compaction was performed using a hydraulic press in the same infiltration chamber. Argon pressure of 3 bars was applied to infiltrate the preforms with the aluminum alloy after melting at 750 °C. The produced aluminum foam specimens show no lack of filling, a high degree of preform replication, and good homogeneity of pore sizes. The preliminary physical and mechanical characterization tests, including relative density, plateau stress, densification strain, and elastic modulus of the foam, are comparable to the values reported in previous investigations, in which more complicated, time-consuming, higher energy, and costly techniques were used. Further investigations on wider ranges of particle sizes, compaction, and infiltration pressures are currently in progress.