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Abrasive jet machining (AJM), also called abrasive micro blasting, is a manufacturing process that utilizes a high-pressure air stream carrying small particles to impinge the workpiece surface for material removal and shape generation. The removal occurs due to the erosive action of the particles striking the workpiece surface. AJM has limited material removal capability and is typically used as a finishing process.
AJM is advantageous in two aspects. First, it has a high degree of flexibility. The abrasive
media can be carried by a flexible hose to reach internal, difficult-to-reach regions. Second, AJM has localized force and less heat generation than traditional machining processes. In this study, AJM is investigated to generate a desired edge shape.
In highly stressed mechanical components, such as the turbine blades and rotors in aircraft engines it is important to avoid sharp edges, which can lead to cracks and premature part failure due to localized stress concentrations.
The technical challenges are the definition, measurement, and generation of edges with the desired shape. In difficult-to-reach edges, for example, at the intersection of holes inside the part, the generation and measurement of the edges are particularly challenging due to the geometrical constraints for limited tooling access. AJM, abrasive flow machining and turbo abrasive machining are all suitable for internal edge generation because of their ability to enter small holes and reach the internal edges. The investigation into the use of AJM was undertaken since it can be applied directly to a single controlled location.
(1999) investigated using AJM to remove burrs at the intersection of cross-drilled holes on stainless steel, while also examining the subsequent edge radius
(2000) proposed a mathematical relationship for edge radius definition when using AJM on a blunt surface
(2003) reported AJM for removing burrs on very small holes in aircraft turbine blades
(2004) examined the AJM process for glass etching and grooving in micro-systems and flat panel displays
(2005) studied the use of AJM as a surface finishing process on wood and WC-Co composite, respectively
However, this method does not take into account the edge radius created on a predefined sharp edge. Therefore, the investigation into the definition of an AJM generated edge has become one of the goals of this research. Another goal of this study is to develop the optical non-contact conoscopy laser measurement with a small, 25 μm, focal point spot size to quantify the shape of the edge after AJM under different processing conditions.
In the cutting tool industry, the shape of the edge is important for tool performance. The radius and waterfall shape are two commonly used features to define an edge. However, the mathematical description of an edge has not been studied extensively. Using high resolution edge measurement, such as the conoscopy laser used in this study, can give a more detailed quantitative analysis of the edge. There is a need for a more precise definition of edge than just a radius. In this study, a mathematical model based on B-spline is investigated to provide a better fit to the measured edge profile. The level of fitness is quantified using an error index.
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