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Manufacturing Process & Quality
Management
Hard Ferrite/Ceramic magnets can be
produced with either isotropic or anisotropic properties.
Anisotropic properties are derived from the high magneto-crystalline
shape anisotropy of the ferrite particles. Physical orientation of
the ferrite particles is necessary in the pressing process to
achieve magnetic alignment.
Hard Ferrite magnets have excellent corrosion resistance and have
normal operating capabilities between -40°C and +250°C. As
temperature increases, remanence decreases by 0.2%/°C whereas
coercively increases by 0.3%/°C. At very low temperatures there is a
risk of permanent demagnetization in magnet systems with low working
points.
The excellent and consistent magnetic and physical characteristics
of DML's ferrite magnet are established by integrated manufacturing
process, which is evolved through long experience, unique technology
and know-how acquired from a world leader like TDK Corporation,
Japan.
Innovative manufacturing technology continuous involvement of
process control and new TQM initiatives enable DML maintain high
level of quality at the most competitive prices in the world.
The following shows the manufacturing sequence from raw material
input through to the final inspection.
MIXING
The Wet mixing process adopted by DML ensures homogeneity which is
very essential for the next process i.e. calcining process.
CALCINATION
This is the pre-firing process which produces the basic magnetic
characteristic in the raw materials. Calcination is done in a Rotory
Kiln where the temperature is controlled in a very narrow band.
MILLING
The coarsed milled powder which is obtained from Vibro Mills are fed
into Attritors for fine milling. Necessary additives to enhance
magnetic properties are added at this stage.
WATER REMOVAL AND KNEADING
The thin slurry from Attritors is passed through filter press and is
well kneaded to form homogenous slurry for wet press moulding.
MOULDING
Thick slurry after dewatering and kneading is pumped into the die
cavity by a high pressure filling device. During the process of
compaction a magnetic field is applied to align the particles in the
desired direction. The water that comes out during the process of
compaction is removed by vacuum. The green product thus formed
inside the die cavity is de-magnetised before removal from die
cavity.
SINTERING
The green magnets from the moulding press are passed through a dryer
and the sintering furnace which is basically a Roller Hearth Kiln
with stringent temperature control facilities.
GRINDING, CLEANING AND PACKING
The sintered magnets are ground in multi spindle segment grinders
incase of arc segments. Thereafter they are cleaned in ultrasonic
bath, dried and packed.
INSPECTION AND SHIPPING
Our well trained Q.A. inspectors monitor the process through out and
also carry out a release inspection prior to dispatch of finished
goods to the customers.
 Process
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