Ring-Shaped Nd-Fe-B Magnet Moulding Die for Crack-Free Sintering
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Solution Overview
Problem
The manufacturing process of ring-shaped sintered Nd-Fe-B magnets faces challenges with high material waste and sintering cracking due to inconsistent heating rates and complex machining processes, leading to low material utilization rates and increased production costs.
Innovation Solution
A method involving a moulding die with a flexible cylindrical core made from alumina and/or zirconia powders bonded with an organic adhesive, which is embedded in the Nd-Fe-B magnetic powder to apply uniform pressure and heat, reducing material waste and cracking by allowing for simultaneous heating of the inner and outer arcs during sintering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional machining processes are used to process outer diameter and inner diameter, then the product shape is achieved, but material utilization rate decreases to less than 60%
Solution Approach 1:
The invention uses a mould core to preliminarily form the inner hole shape during the green block manufacturing stage, so that the inner hole structure is established before sintering. This preliminary action eliminates the need for subsequent inner hole machining, thereby preventing material waste while achieving the required product shape.
Solution Approach 2:
The invention extracts the inner hole formation process from the post-sintering machining stage and moves it to the pre-sintering moulding stage. By removing the inner hole material during moulding rather than after sintering, the process eliminates unnecessary material waste associated with traditional sequential machining.
2Shape
If mould core is removed from green block after isostatic pressing, then the inner hole is formed, but the inner surface integrity is damaged and production time increases
Solution Approach 1:
The invention employs a flexible mould core made of rubber or plastic material that can be easily extracted from the green block after isostatic pressing. The flexibility of this shell-like structure allows it to be removed without damaging the inner surface of the green block, while still maintaining the required inner hole shape and integrity.
3Use of energy by moving object
If inner hole of green block is not heated during sintering, then heating time is reduced, but sintering shrinkage inconsistency and cracking occur
Solution Approach 1:
The invention uses the mould core as a thermal intermediary during sintering. The mould core, being in direct contact with the inner hole region of the green block, acts as a heat transfer medium that conducts thermal energy to the inner hole area. This intermediary role ensures uniform heating and consistent sintering shrinkage throughout the product, preventing cracking while maintaining heating efficiency.
4Manufacturing precision
If complex machining processes are used for ring-shaped magnets, then the product shape is achieved, but production cost increases
Solution Approach 1:
The invention performs the inner hole formation action preliminarily during the green block manufacturing stage using a mould core, rather than performing complex machining operations after sintering. This preliminary shaping action simplifies the overall manufacturing process and reduces production costs by eliminating subsequent machining steps.
Solution Approach 2:
The invention merges the inner hole formation process with the green block manufacturing process by using a mould core during moulding. This consolidation of operations eliminates the need for separate post-sintering machining steps, thereby reducing production complexity and cost while maintaining product shape accuracy.
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 enhances material utilization rates and reduces sintering cracking, achieving higher quality sintered products with improved material efficiency and processing ease.
Implementation Method 1
A flexible cylindrical core formed from powders of alumina and/or zirconia, which are bonded with an organic adhesive... applying uniform pressure and heat, reducing material waste and cracking by allowing for simultaneous heating of the inner and outer arcs during sintering
Implementation Method 2
A flexible cylindrical core formed from powders of alumina and/or zirconia, which are bonded with an organic adhesive
Data Source
Figure 1~2
AI summary
The invention provides a preparation method, which comprises the following steps: step a) providing a moulding die for a ring-shaped sintered Nd-Fe-B magnet; step b) placing a Nd-Fe-B magnetic powder into the mould cavity of the moulding die in a loosely packed state, the loosely packed height of the Nd-Fe-B magnetic powder is L; step c) placing a flexible cylindrical core into the loosely packed Nd-Fe-B magnetic powder at a L/2 position, wherein an axial direction of the flexible cylindrical core is horizontal and parallel to the direction of a magnetic field in the mould cavity; step d) applying a vertical pressure to the Nd-Fe-B magnetic powder to obtain a ring-shaped green block assembly with the flexible cylindrical core embedded therein; step e) after encapsulating and isolating the ring-shaped green block assembly, applying an isostatic pressure to the ring-shaped green block assembly; step f) sintering the ring-shaped green block assembly to obtain a ring-shaped sintered blank; and step g) thermally aging, grinding and slicing the ring-shaped sintered blank to obtain the ring-shaped sintered Nd-Fe-B magnet.