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METHOD FOR MILLING OF INTEGRALLY BLADED ROTORS

IP.com Disclosure Number: IPCOM000248492D
Publication Date: 2016-Dec-08

Publishing Venue

The IP.com Prior Art Database

Abstract

A method is provided for computer optimization of a tool shape and tool path for a rough milling step of an integrally-bladed turbomachinery rotor ("IBR").

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This is the abbreviated version, containing approximately 30% of the total text.

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METHOD FOR MILLING OF INTEGRALLY BLADED ROTORS

ABSTRACT


[0001] A method is provided for computer optimization of a tool shape and tool path for a rough milling step of an integrally-bladed turbomachinery rotor ("IBR").

BACKGROUND


[0002] A gas turbine engine utilizes one or more rotors (compressor or turbine) having a rotating hub carrying an array of airfoil-shaped blades. In a conventional rotor, the blades are manufactured separately and mounted into machined grooves of the hub. In contrast, an IBR comprises a plurality of integral blades extending radially outward from a hub. An IBR could be a bladed disk "(BLISK") or bladed drum ("BLUM"). An IBR offers several advantages over conventional rotors, such as reducing aerodynamic losses, weight, complexity and parts count.


[0003] However manufacturing of an IBR is difficult because of the large volume of the material to be removed, complex 3D airfoil geometry, the use of difficult-to-machine materials, etc.


[0004] One known manufacturing process for an IBR involves using a milling head (cutter) of spherical form (FIG. 1) mounted in an appropriate machine tool, such as a multi-axis CNC milling machine, to make one or more initial rough cuts in a disk-shaped workpiece. In this "rough milling" process, material is removed between two sections of material that will eventually become compressor blades. Subsequent machining is done conventionally, for example using a ball-end milling cutter.

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[0005]

FIG. 1 cutting tool of spherical configuration being used for rough milling operation


[0006] Conventionally, the tool path and cutter shape for the rough milling steps are not optimized. The current process of selecting a tool and generating the tool path comprises modeling of the cutter geometry in a CAD software package and manually positioning and orienting the cutter in the 3D model of the IBR such that sufficient clearance exists between the cutter and airfoil surfaces. If a suitable orientation is not obtained the cutter geometry is modified and the process is repeated. Once a satisfactory orientation is obtained the tool path is derived (along radial and flow path directions) based on the property that the cutter is constrained to move on the defined sphere surface to avoid fouling of the tool body with the IBR surfaces. However, this process is time consuming even for an expert programmer, and there is a chance of machining the IBR with a non-optimal tool and/or tool path, resulting in excess material left for finishing operations.


[0007] Described herein is a method for computer optimization of a tool shape and tool path for a rough milling step of an IBR.

DETAILED DESCRIPTION OF THE CONCEPT


[0008] Referring to FIG. 2, the spherical tool can be represented by an imaginary sphere passing through the mid-section of the tool (hereinafter "tool center sphere" or TCS). For any valid tool location, the TCS must pass through a center line (hereinafter

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