A computer numerical control (CNC) multi-pass spinning solution to a center lathe retrofit

Abstract

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.

Machine Tool Transition from Industry 3.0 to 4.0: A Comparison between Old Machine Retrofitting and the Purchase of New Machines from a Triple Bottom Line Perspective

“…Table 2 summarizes the criteria used in these works for justifying the retrofitting process. Abd-Alrazzaq et al [17] selected a conventional center lathe machine as a good candidate for the CNC retrofit; this is a low-cost solution that can ensure the high quality of the parts. Siedlecki et al [18] analyzed retrofitting of a farm tractor with a universal particle filter with the size chosen relative to engine displacement, finding that this alternative saves money and reduces emissions.…”