Sintered Magnet Mold Inversion for Crack Prevention
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Solution Overview
Problem
Sintered magnets with nonuniform thickness, such as convex shapes, experience higher cracking probabilities and lower yield rates due to sintering shrinkage-induced local slips during the manufacturing process.
Innovation Solution
A sintered magnet manufacturing method involving a mold with a non-flat lower cavity face and a flat lid, where the mold is inverted to ensure the flat face is downward during the sintering process, preventing cracks by maintaining full-face contact and reducing friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If sintered magnets with nonuniform thickness (convex shapes) are manufactured using conventional PLP method, then complex shapes suitable for motor applications can be produced, but cracking occurs due to sintering shrinkage-induced local slips resulting in lower yield rates
Solution Approach 1:
The invention applies different surface qualities to different parts of the mold: the lower cavity face has a non-flat surface matching the convex shape of the magnet, while the lid inner face has a flat surface. This local differentiation ensures uniform contact during sintering shrinkage, preventing local slips that cause cracking, while still producing complex convex shapes.
Solution Approach 2:
The invention inverts the conventional mold orientation by placing the flat surface on the lid (top) rather than on the base (bottom). During sintering, the mold is positioned with the flat lid face downward, ensuring uniform contact area throughout the sintering shrinkage process, which prevents localized stress concentration and cracking in convex-shaped magnets.
2Ease of manufacture
If conventional mold orientation is used during sintering, then manufacturing process is simple, but sintering shrinkage causes local slips and cracking in nonuniform thickness magnets
Solution Approach 1:
The mold is designed in advance with a flat inner face on the lid and a non-flat face on the base, oriented such that the flat face will be in full-face contact during sintering. This preliminary configuration ensures that during the sintering process, uniform contact is maintained throughout, preventing local slips and cracking without requiring complex real-time adjustments.
3Ease of manufacture
If flat surface is used on the base of the mold, then manufacturing is simpler, but sintering shrinkage causes local slips at contact points resulting in cracks
Solution Approach 1:
The mold design assigns different surface characteristics to different locations: the base has a non-flat surface that matches the convex shape, while the lid has a flat surface. During sintering with the flat lid face downward, this local quality differentiation ensures uniform distributed contact, preventing stress concentration and cracking, while keeping the mold manufacturable.
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 significantly increases the yield of sintered magnets with nonuniform thickness by preventing cracks caused by local slips, allowing for high-yield production of magnets with complex shapes suitable for motor applications.
Implementation Method 1
friction arises between the sintered article and the mold... preventing cracks by maintaining full-face contact and reducing friction
Implementation Method 2
applying a magnetic field to the raw material alloy powder in the mold to orient particles of the raw material alloy powder
Implementation Method 3
performing sintering by heating the compression molded article after releasing the applied pressure
Data Source
AI summary
The present invention relates to a method for manufacturing a sintered magnet, using a mold provided with a main body having a cavity and a lid whose inner face is flat, and the method containing a filling process of filling alloy powder in the cavity and then mounting the lid on the main body, an orienting process of applying a magnetic field in a predetermined direction to the alloy powder in a state of being filled in the cavity, a sintering process of sintering the alloy powder by heating in a state of being filled in the cavity after the orienting process, and a mold inverting process of turning the mold upside down which is carried out between the filling process and the orienting process or between the orienting process and the sintering process.