Cylindrical Bonded Magnet Extrusion Orientation
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Solution Overview
Problem
The existing methods for manufacturing cylindrical bonded magnets, such as injection molding and compression molding, face limitations in achieving high surface magnetic flux density due to difficulties in orienting magnetic materials, especially for small-sized magnets, leading to lower productivity and higher density, which hinders the development of smaller and lighter spindle motors.
Innovation Solution
A method and equipment for extrusion molding of cylindrical bonded magnets using a bonded magnet composition with an anisotropic magnetic material, where a unique orientation magnet configuration with alternating N and S poles is employed to create a powerful magnetic field, allowing continuous orientation and curing of the molten composition, resulting in a higher surface magnetic flux density and lower density magnets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If injection molding or compression molding is used to manufacture cylindrical bonded magnets, then the magnets can be produced with controlled shape and composition, but the productivity is limited due to batch production cycles and the surface magnetic flux density is reduced due to difficulties in orienting magnetic materials
Solution Approach 1:
The patent replaces mechanical orientation methods (compression molding) with a magnetic field-based orientation system. An orientation magnet generates a magnetic field that aligns magnetic particles in the molten composition during extrusion molding, achieving high surface magnetic flux density without the limitations of batch production cycles.
Solution Approach 2:
The patent implements continuous extrusion molding instead of batch production. The molten bonded magnet composition is continuously extruded through a die while passing through the magnetic field of the orientation magnet, enabling continuous production without cycle interruptions, thereby significantly improving productivity.
2Stability of the object's composition
If mechanical orientation is used during compression molding, then the magnetic material particles can be aligned to achieve anisotropic magnetic properties, but the pressure is not transmitted to the middle of slender molded articles resulting in incomplete filling
Solution Approach 1:
The patent changes the physical state of the bonded magnet composition to molten state during extrusion molding. This allows the composition to flow easily and fill the mold completely under extrusion pressure, while the magnetic field simultaneously orients the magnetic particles. The combination of fluid flow and magnetic field action solves both the filling and orientation problems.
Solution Approach 2:
The patent replaces mechanical compression orientation with magnetic field orientation. The orientation magnet generates a magnetic field that aligns magnetic particles in the molten composition without requiring high compression pressure, thereby enabling complete filling of slender articles while achieving proper particle orientation.
3Productivity
If injection molding is used for slender articles, then the molding can be completed in a batch cycle, but the bonded magnet composition cools down after going through the gate resulting in short shot (improper molding due to incomplete filling)
Solution Approach 1:
The patent implements continuous extrusion molding where the molten bonded magnet composition is continuously extruded through a die. The composition remains in molten state throughout the extrusion process and is immediately molded, eliminating the cooling issue that occurs in injection molding after the gate. This continuous process ensures complete filling without short shots.
Solution Approach 2:
The patent performs orientation of magnetic particles during the extrusion process itself, before the composition cools and solidifies. The orientation magnet is positioned to act on the molten composition as it exits the die, ensuring proper particle alignment is achieved while the material is still fluid and can be properly molded.
4Quantity of substance
If ferrite-based magnetic material is used in bonded magnets, then the cost is reduced and mechanical strength is improved, but the magnetism is weaker which is insufficient for small molded articles
Solution Approach 1:
The patent replaces mechanical compression molding with extrusion molding combined with magnetic field orientation. This allows for better particle alignment and more efficient packing of magnetic materials, thereby increasing the magnetic force strength without increasing material cost. The continuous extrusion process enables optimal particle arrangement that enhances magnetic performance.
Solution Approach 2:
The patent uses a composite composition of magnetic material particles suspended in a molten resin matrix during extrusion molding. The magnetic field orientes the particles within this composite, creating an anisotropic structure with enhanced magnetic properties. The resin binder holds the oriented particles in place, maintaining the improved magnetic force strength.
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 enables the production of cylindrical bonded magnets with higher surface magnetic flux density and lower density, facilitating the creation of smaller and lighter spindle motors with enhanced magnetic performance.
Implementation Method 1
Magnetic field orientation refers to orienting particles by applying a magnetic field externally during molding
Implementation Method 2
heating a bonded magnet composition composed of a magnetic material and a thermoplastic resin or thermosetting resin in a cylinder to melt the composition and put it in a fluid state
Data Source
AI summary
In a method for manufacturing a cylindrical bonded magnet, a molding space having a cylindrical shape is filled with a bonded magnet composition containing a magnetic material and a resin. The magnetic material disposed in the molding space is magnetically oriented using an orientation magnet. The orientation magnet includes a first permanent magnet and a second permanent magnet. The first and second permanent magnets are disposed such that same poles are opposite each other in the axial direction.