Method and apparatus for preparing rare earth sintered magnet

A method for preparing a rare earth sintered magnet from a corresponding alloy powder using a mold and a feeder,

• said mold comprising a die, an upper punch having a pressure surface, and a lower punch having a pressure surface, the pressure surface of one or both of the upper and lower punches being shaped non-planar, a cavity being defined between the die and the lower punch, the feeder including a shooter having a lower end port for passage of the alloy powder, the port being aligned with the cavity,
• said method comprising the steps of feeding the alloy powder from the feeder into the cavity through the shooter until the cavity is filled with the alloy powder, compressing the alloy powder fill in the cavity under a magnetic field between the upper and lower punches for uniaxial pressure molding to form a precursor, and heat treating the precursor,
• wherein the shooter is provided with a main sieve at its lower end port such that the main sieve is disposed closely above the cavity, the main sieve having a sifting surface of non-planar shape as the pressure surface of the upper or lower punch,
• during the step of feeding the alloy powder into the cavity through the shooter, vibration and vertical reciprocation are applied to the shooter to assist the alloy powder to pass through the main sieve and fall into the cavity.