EVALUATION OF VARIOUS METHODS FOR MANUFACTURING ONE PIECE, SMALL TIP OPENING IMPELLERS

Abstract

Closed centrifugal compressor impellers have been manufactured using several methods through the years. Due to limitations of the materials and machining processes, most of these impellers have been manufactured in what is considered two piece or three piece methods. Despite the vast amount of experience with traditional construction methods, there is a drive to move towards one piece construction, where there are no joints and, in theory, lower probability of preexisting defects. Typically, the impellers that are being offered as one piece are those with relatively large openings where 5-axis milling machines can be utilized. This paper investigates several alternative methods to manufacturing small tip opening impellers as a single piece. The methods discussed include Electrical Discharge Machining (EDM), investment casting, Hot Isostatic Pressed Powder Metal (HIP’d PM), and Direct Metal Laser Sintering (DMLS).