Mechanism of mixing is shear
Shear is transferred by moving blades. High shear rates are
effective in breaking lumps and aggregates. Convective mixing also occurs as
the powder bed is lifted and allowed to cascade to the bottom of the container.
An equilibrium state of mixing can be achieved.
• Consists of horizontal cylindrical trough usually open at
the top. It is fitted with two helical blades, which are mounted on the same
shaft through the long axis of the trough.
• Blades have both right and left hand twists.
• Blades are connected to fixed speed drive.
• It can be loaded by top loading and emptying is done
through bottom port.
• Through fixed speed drive, ribbons are allowed to rotate.
• Helical blades moves powders from one end to another.
• One blade moves material in one direction and other moves
• Close open trough to avoid dusting during dry blending.
• Due to high shear it effectively breaking up lumps and
• Once equilibrium achieved, powder mixture discharge from
• Used for mixing of finely divided solids, wet solid mass,
and plastic solids
• Uniform size and density materials can be easily mixed
• Used for solid – solid and liquid – solid mixing
Advantages of ribbon
• High shear can be applied by using perforated baffles,
which bring about a rubbing and breakdown aggregates
• Headroom requires less space
• It is a poor mixer, because movement of particles is two dimensional..
• Shearing action is less than in planetary mixer
• Dead spots are observed in the mixer, though they are minimum
• It has fixed speed drive