Common processing methods for sintered neodymium iron boron
https://www.magnet-forever.com/product/large-neodymium-arc-magnets-for-motor1. The slicing (cutting) process often uses slicing machines, wire EDM machines, wire saws, or laser cutting machines to complete the cutting process.
Slicer: Using high-speed rotating thin inner circular diamond cutting tools to automatically cut neodymium iron boron magnetic steel, cutting oil is used as the cutting coolant during the slicing process. The advantage is that it does not require customized special cutting tools, has strong flexibility, and is suitable for sample processing and cutting processing. However, due to low processing efficiency and material yield, as well as weak ability to ensure verticality, batch slicing production has gradually been replaced by multi wire cutting machines (wire saws).
Multi wire saw cutting: Use fixtures to fix the workpiece on the worktable, and use a roller cloth diamond wire. The high-speed running diamond wire (wire diameter 0.15~0.2mm) rubs against the magnetic steel to achieve material cutting. The cutting process is cooled by cutting fluid. The main feature is that it can simultaneously cut multiple workpieces, with high production efficiency, yield rate, and material output rate. It has strong ability to ensure verticality and is suitable for continuous batch processing. But customized specialized rollers are required for different specifications of products.
Wire EDM: Using a molybdenum wire electrode to generate high-frequency electric sparks on neodymium iron boron magnetic steel, causing it to melt locally. Controlled by a computer, the electrode wire is cut and processed according to a predetermined trajectory. The advantage of wire electrical discharge cutting is high machining accuracy, which can be used for slicing tile shaped and irregular products, as well as cutting large magnets. The disadvantage is that the cutting speed is slow, and the melting zone on the cutting surface has a significant impact on the magnetic properties.
Laser cutting: using a laser beam to converge on a magnetic material, the magnetic material melts and vaporizes, and the disappearing area forms a cutting seam. Laser cutting is a non-contact processing method with low environmental impact, high processing accuracy, and the ability to process inclined surfaces. It has broad application prospects. However, the changes in temperature and stress during the processing have a certain impact on the performance of the magnet, and when cutting thick products, the divergence of the laser beam causes a slope in the cutting section.
2. Grinding process
Mainly refers to the processing method of grinding the surface of a workpiece with a grinding disc or grinding wheel. The commonly used grinding methods for square neodymium iron boron magnetic steel include vertical grinding, flat grinding, and double end grinding. Cylindrical and circular neodymium iron boron blanks often use centerless grinding, square grinding, inner and outer circular grinding, etc. Multi station forming grinders can be used for tile shaped, fan-shaped, and special-shaped magnetic steel.
Surface grinder: Used for surface grinding of magnetic materials and can also perform multi-faceted machining. Generally, a horizontal axis rectangular table surface grinder (flat grinding) or a vertical axis circular table surface grinder (vertical grinding) is used. The magnetic steel flat surface is neatly stacked as a reference surface and fixed on the disk worktable with baffle fixtures, etc. The reciprocating surface grinding is carried out using a grinding wheel.
Double end grinder: The product is continuously passed through by a conveyor belt, with two grinding wheels located on both sides of the product. The grinding wheels are driven by the rotation of a horizontal axis double grinding head (the two grinding wheels produce an inclination angle), and the two planes of the product are ground under the rotation of the grinding wheels. Double end face grinder has high machining accuracy and small surface roughness, making it the most widely used symmetrical plane machining equipment in neodymium iron boron machining.
Heartless grinding machine (or square rounding machine): Heartless grinding machine is used for the outer circle grinding of cylindrical blanks, while square rounding machine is used for the rounding of square bar magnetic steel. By using a feeder and guide rail, the magnetic steel is sequentially passed through a guide wheel and a grinding wheel. The guide wheel drives the magnetic steel workpiece to rotate on the shim, while the grinding wheel grinds the outer circle of the magnetic steel to the required diameter.
Internal and external cylindrical grinder: The magnetic steel workpiece is fixed by a fixture, and then the grinding head is moved along the inner or outer circumference of the workpiece to grind the magnetic steel workpiece to the set size of the inner and outer circles, and the surface is smoothed and deburred. Mostly used for inner and outer surface processing of circular ring products.
3. Drilling (punching) processing
The drilling process of sintered neodymium iron boron is prone to fracture or fragmentation, therefore specific equipment and processes are required for drilling operations. The commonly used equipment for neodymium iron boron inner hole processing includes drilling machines, instrument lathes, and bench drilling machines.
Hole digging machine (hole drilling machine): A device that uses diamond ring cutting tools, the product is fixed by a chuck and rotated by a spindle, and the tool feed achieves inner hole machining of the product. The drilling lathe is usually used to process neodymium iron boron products with inner holes of 8mm or more. By using specially designed cutters and reamers, holes can be drilled and reamed.
Instrument lathe: The instrument lathe clamps magnetic steel products with fixtures, drives the products to rotate continuously through the spindle motor, and drills the rotating workpieces with fixed alloy cutting tools. Mainly used for drilling and fitting holes in cylindrical, circular, and small square products, with a machining aperture of less than 5mm.
Desktop drilling machine: a device that uses self-made tooling to position products and rotates hard alloy cutting tools to achieve drilling and processing of products; The main difference between an instrument lathe and a lathe is that the workpiece rotates while the tool is fixed; The workpiece of the desktop drilling machine is fixed, and the cutting tool rotates. Therefore, desktop drilling machines can be applied to the processing of through holes, blind holes, and step holes in irregular products.
Ultrasonic drilling machine: The ultrasonic energy is concentrated at the position of the drill bit through a transducer, and the high-frequency mechanical vibration of the drill bit drives the abrasive suspension to achieve impact perforation through high-speed impact, friction, and cavitation. Ultrasonic drilling has high precision, efficiency, and qualification rate, and can be applied to small hole processing of magnetic steel.
4. Chamfering: The sharp angles generated during the grinding, slicing, drilling and other processing of neodymium iron boron magnetic products can easily cause edge chipping, and the tip effect during electroplating can deteriorate the uniformity of the coating. Therefore, after machining, the magnetic steel is usually chamfered, including mechanical chamfering and vibration chamfering. Common chamfering equipment includes vibration chamfering machines and drum chamfering machines.
Vibration chamfering machine: By using the vibration deviation generated by the vibration motor, the magnetic steel and abrasive in the working groove are driven to move up, down, left, right or rotate and rub against each other, thereby making the surface of the product flat and smooth, while grinding the edges and corners. Common abrasive media include silicon carbide, brown corundum, etc.
Roller chamfering machine: It is a type of machine that places neodymium iron boron magnetic steel products, abrasives, and grinding fluids into a sealed horizontal roller. The rotation of the roller causes centrifugal friction between the product and the abrasive, resulting in chamfering.
Manufacturers will choose the most economical and efficient processing route based on product size specifications and dimensional tolerance requirements. For the quality of processed products, we should mainly focus on dimensional tolerances, geometric tolerances, and appearance. Common defects and defects in processing include: dimensional deviation, poor verticality and contour, missing corners, cutting threads, scratches, abrasion, corrosion, hidden cracks, etc.