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Machining of Free Form Surface with Enclosed Wall of Three Bladed Mini Propeller Mould

By M E Mohana Sundaram, R Prathapanayaka, N Vinodkumar, SJ Krishnamurthy and M Radhakrishna

Abstract

The conventional machining of miniature components is an interesting and very challenging task. Machining of miniature components will take long lead time to get the required size and tolerance due to the limitations of size of the machining tool and limited material removal rate. This paper presents the process of machining metal mould using aluminum-2024 material in 3-Axis CNC milling machine with enclosed wall of free form surfaces. The mini propeller mould is divided in to two halves namely top and bottom. The top mould has the twisted cavity contours of suction surface of the propeller blade airfoil. The bottom mould has the twisted cavity contours of pressure surface of the propeller blade airfoil. Smooth matching of leading and trailing edges over the span of the blade are also accomplished. To avoid the cutting tool interference during machining of the space between two blades, smooth contours in the mould is given and machined accordingly. The machining operations are divided in to ‘rough machining’ and ‘finishing operation’ to minimize the machining time. To avoid local gouging on the profile, sufficient allowance is kept in comparison to actual material to be removed by leaving extra material for finishing operation. During the finishing operation on the propeller blade profile which consists of free form surface, two boundaries were introduced instead of single boundary method to generate the tool path in span wise direction. The matching of two boundaries profile after finishing operation is within the accepted tolerance of + 0.04mm. The machined moulds were inspected and compared with the IGES model of the mould. New machining method adopted here has saved 40% machining time without compromising in accuracy of machining top and bottom moulds of the propellers. The geometrical accuracies and surface finish of propellers blade obtained through this process are good in comparison to RPT process

Topics: Aircraft Propulsion and Power
Year: 2014
OAI identifier: oai:nal-ir.nal.res.in:12083
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