Segmented Rotor Casting for Low Porosity Cu-Al Hybrid Motors
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Solution Overview
Problem
The current copper-aluminum (Cu—Al) hybrid rotor casting process for motor rotors suffers from high porosity and inconsistent bonds due to the inability to expel air and gas from the mold, leading to substantial rejected assemblies and the need for a post-machining process for aluminum runner removal.
Innovation Solution
The process involves forming multiple steel plates with radially oriented slots and aligned runners that create axially aligned or skewed passages, allowing molten aluminum to flow radially outward and surround conductive bars, thereby minimizing air and gas entrapment and enhancing bonding consistency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional Cu-Al hybrid rotor casting process is used, then production cost is reduced by using aluminum instead of permanent magnets, but porosity increases and bonding consistency deteriorates due to inability to expel air and gas from the mold
Solution Approach 1:
The mold is segmented into multiple cavities with individual runners for each cavity. This segmentation allows each runner to independently control the flow of molten aluminum into its associated cavity, enabling better expulsion of air and gas from each cavity and reducing porosity while improving bonding consistency.
Solution Approach 2:
Runners are introduced as intermediary channels between the mold cavity and the molten aluminum source. These runners act as mediators that facilitate controlled material flow and enable the expulsion of air and gas from the mold cavities, thereby reducing porosity and improving bonding consistency.
2Productivity
If traditional casting process is used, then manufacturing simplicity is maintained, but productivity decreases due to substantial rejected assemblies from high porosity and inconsistent bonds
Solution Approach 1:
The mold is divided into multiple cavities, each with its own runner system. This segmentation increases the number of rotors that can be produced simultaneously in one casting cycle, thereby improving productivity and yield rate despite the increased complexity of the mold structure.
Solution Approach 2:
The segmented mold structure with multiple cavities and runners serves multiple functions: it produces multiple rotors simultaneously (increasing productivity), controls material flow to each cavity (reducing porosity), and maintains bonding consistency. This multi-functionality justifies the increased device complexity.
3Loss of substance
If traditional casting process is used, then process simplicity is maintained, but loss of substance increases due to substantial rejected assemblies
Solution Approach 1:
The segmented mold with multiple cavities and individual runners allows for controlled material distribution, reducing defects and rejected assemblies. This reduces material waste despite the increased complexity of the mold structure.
Solution Approach 2:
The runners act as intermediaries that enable controlled material flow and expulsion of air and gas, reducing porosity and bonding defects. This reduces the number of rejected assemblies and material waste, justifying the increased device complexity.
4Loss of time
If traditional casting process is used, then manufacturing process simplicity is maintained, but loss of time increases due to post-machining process for aluminum runner removal
Solution Approach 1:
The segmented mold structure with multiple cavities and runners is designed to facilitate easier removal of aluminum runners, reducing or eliminating the need for post-machining operations and thereby reducing loss of time despite the increased device complexity.
Solution Approach 2:
The runners are designed as removable intermediaries that can be easily separated from the cast rotors. This design reduces the need for post-machining operations to remove runners, thereby reducing loss of time despite the increased device complexity.
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 approach reduces porosity in the aluminum casting, improves conductivity and performance of the rotor, and eliminates the need for post-machining of runners, resulting in a more efficient and consistent Cu—Al hybrid rotor manufacturing process.
Implementation Method 1
an aluminum material is cast about the stack and forced under pressure into the slots and about the copper bars
Implementation Method 2
forced under pressure into the slots and about the copper bars
Data Source
AI summary
A rotor stack assembly includes multiple plates each including multiple elongated slots each oriented radially outward from a longitudinal central axis of each plate toward an outer perimeter wall of the plate. Multiple openings are each positioned proximate to one of the slots and directed outwardly through the outer perimeter wall. Multiple runners individually extend through the plate and individually open into one of opposed ends of each of the slots. Multiple bars of a conductive material are each extended through aligned ones of the slots of each of the multiple plates.