Centrifugal Impeller Passageway Formation via Inverted EDM
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Solution Overview
Problem
The manufacturing of centrifugal compressor impellers faces challenges in precisely forming complex passageways due to their curved shapes, which are difficult to process using existing methods like electrical discharge machining, leading to potential deformation and low precision.
Innovation Solution
A method involving a rotation center positioned between the curvature centers of the outer and inner stream surfaces, allowing a processing tool to be rotated and moved in a curved locus to form the passageway from the inner to the outer peripheral side, enabling precise formation of the curved passageway by adjusting the rotation center and tool position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If welding is used to fix blades and shroud to the hub, then the impeller can be assembled, but deformation occurs and manufacturing precision deteriorates
Solution Approach 1:
The invention extracts the problematic welding operation from the manufacturing process and replaces it with electrical discharge machining. Instead of joining separate components (blades, shroud, hub) through welding, the passageway is directly formed in the hub, eliminating the need for welding and thus preventing deformation while maintaining assembly capability.
Solution Approach 2:
The invention substitutes the mechanical welding process with electrical discharge machining. The thermal-mechanical welding process that causes deformation is replaced by an electrical field-based material removal process, achieving the same functional result (forming the passageway) without the harmful thermal effects.
2Manufacturing precision
If electrical discharge machining is used to form the passageway from the outer peripheral side, then welding is avoided, but the inner portion of the curved passageway cannot be processed with high precision
Solution Approach 1:
The invention inverts the processing direction by introducing a new approach: forming the passageway from the inner peripheral side toward the outer peripheral side, rather than the conventional outer-to-inner direction. This inversion allows the electrode to access and precisely process the inner curved portion that was previously inaccessible, while still avoiding welding.
Solution Approach 2:
The invention changes the processing dimension by inserting the electrode from the inner peripheral side (radial dimension) rather than from the outer peripheral side. This dimensional change in approach allows the electrode to follow the curved path of the passageway and precisely form the inner curved portion that cannot be accessed from the outer side.
3Reliability
If the passageway is formed with complex curved shape, then the impeller function is achieved, but the processing becomes difficult and precision is reduced
Solution Approach 1:
The invention applies local quality by tailoring the electrode shape to match the specific geometry of the passageway section being processed. The electrode is designed with a shape corresponding to the curved passageway, allowing precise formation of each local section while maintaining the overall complex functional shape required for impeller performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method allows for the easy and precise formation of the passageway, reducing deformation risks and improving the manufacturing accuracy of centrifugal compressor impellers by shortening processing lengths and enhancing precision in forming both inner and outer curved portions.
Implementation Method 1
a first passageway forming step of setting a rotation center at a position between a curvature center of part of an outer stream surface forming the outer portion of a curved portion and a curvature center of part of an inner stream surface forming the inner portion of the curved portion on one side of the axial direction where a curvature center of the passageway is located relative to a disk forming an external shape of the impeller, and rotating a processing tool about the rotation center relative to the disk so as to form at least a part of the passageway
Data Source
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AI summary
A method of manufacturing an impeller (1) of a centrifugal rotary machine, the impeller being formed in a substantially disk shape and including a passageway (2) curved to follow the axial direction in an inner peripheral side of the impeller and to follow the radial direction as it goes to an outer peripheral side thereof, the method includes: a first passageway forming step of setting a rotation center at a position on one side of the axial direction where a curvature center of the passageway is located relative to a disk forming an eternal shape of the impeller, and rotating a processing tool about the rotation center relative to the disk so as to form at least a part of the passageway from a position which is an inner peripheral end of the passageway of the disk toward the outer peripheral side.