Radial Current Ring Magnet Sintering
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Solution Overview
Problem
The existing methods for producing ring-shaped permanent magnets, such as those used in modern electric motors, are complex, time-consuming, and expensive due to limitations in conventional sintering processes, which struggle with producing thick or ring-shaped workpieces as they result in incomplete fusion and density inhomogeneities.
Innovation Solution
A device and method utilizing electrical discharge sintering with a radial current flow and axially directed force, allowing for the production of ring-shaped permanent magnets by creating a cavity with a radial current path that ensures homogeneous melting and compaction, independent of electrode distance, using a device with a core and outer mold forming electrodes and insulation between them.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional sintering with axial current flow is used, then the process is simple to implement, but the production of thick or ring-shaped workpieces results in incomplete fusion and density inhomogeneities
Solution Approach 1:
The patent transitions from axial current flow (one-dimensional) to radial current flow (two-dimensional in the cross-section), enabling homogeneous heating throughout the workpiece thickness. The electrode arrangement changes from top-bottom positioning to inner-outer cylindrical positioning, creating a radial electromagnetic field that penetrates the workpiece uniformly from all directions around the circumference.
Solution Approach 2:
Instead of applying compression force in the same direction as current flow (axial), the patent inverts the approach by applying axial compression force while current flows radially in the perpendicular direction. This orthogonal arrangement ensures that the direction of maximum densification (axial compression) is independent of the current flow direction, allowing uniform fusion regardless of workpiece thickness.
2Productivity
If conventional sintering is used, then heating equipment is simple, but heating up to sintering temperature takes comparatively long time
Solution Approach 1:
The patent employs pulsed direct current instead of continuous heating, applying high-current pulses that rapidly heat the workpiece through resistive heating during the pulse duration, followed by cooling intervals. This periodic heating achieves faster temperature rise compared to conventional continuous low-power heating methods.
Solution Approach 2:
The patent changes the heating mechanism from conventional thermal conduction heating to resistive (Joule) heating by passing high-current pulses through the workpiece. This parameter change in the heating method enables rapid temperature increase and reduces the time required to reach sintering temperature.
3Reliability
If axial current flow is used, then electrode arrangement is simple, but current flow resistance increases with workpiece thickness
Solution Approach 1:
The patent transitions from axial current flow (one-dimensional path) to radial current flow (two-dimensional distribution in the cross-section). This dimensional change creates multiple parallel current paths through the workpiece thickness, reducing overall resistance and improving current distribution uniformity, especially in thick or ring-shaped workpieces.
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
Enables the production of ring-shaped permanent magnets with consistent magnetic properties and arbitrary geometric shapes, including tall and hollow-cylindrical forms, by ensuring homogeneous heat generation and compaction, overcoming the limitations of axial current flow in prior art methods.
Implementation Method 1
Joule heat is generated at these contact points, which is so great that the powder particle contact points change into a molten phase
Implementation Method 2
a force is applied to the powder in the direction of the cavity to compact the powder in the molten state
Implementation Method 3
processes for powder compaction by short-time sintering are known to those skilled in the art as EDS (Electric Discharge Sintering) or synonymously CDS (Capacitor Discharge Sintering)
Data Source
Figure 1a~1b
Figure 2
AI summary
The invention relates to a device (1) and a method for producing ring-shaped permanent magnets by means of an electrical discharge element. The device comprises several tool parts (3, 4, 5, 6) defining a ring-shaped cavity (11) for receiving a magnetizable metallic powder (2) and a controllable electrical pulse current generator (8, 9), wherein at least two of the tool parts (3, 4, 5, 6) form electrodes and are electrically connected to the pulse current generator (8, 9).The tool components (3, 4, 5, 6) comprise at least one outer form (3) that defines the cavity (11) radially outwards, a core (6) that defines the cavity (11) radially inwards and is arranged coaxially to the outer form (3), and two compression elements (4, 5) that define the cavity (11) axially and are axially movable relative to each other, wherein at least one of the compression elements (4, 5) is subjected to a force or can be subjected to a force in the direction of the cavity (11). The outer form (3) and the core (6) form the electrodes. The compression elements (4, 5) electrically insulate the electrodes from each other, so that the current flow is perpendicular to the force. In this way, homogeneously compressed ring magnets of any length can be produced simply and quickly.