Mixing: Sigma Blade Mixer.

 

Principle:

• It's an “Agitator  Mixer”.

• It works on the mechanism of Shear and Convective Mixing.

• This type of mixer employs a stationary container to hold the material and brings about mixing by means of moving  screws, paddles or blades.

• They cause folding, kneading, tearing and mixing of the materials.

Construction:

•  Consists of a vessel in which it uses two mixer blades, the shape of which resembles the Greek letter “sigma” (Σ).

• The loading of material is done from top by opening the lid.

• The unloading is done by tilting the entire vessel.

Working:

• The materials to be mixed are introduced to the mixer through the lid.

• The two blades rotate towards each other and operate in a mixing vessel which has a double trough shape, each blade fitting into a trough.

• The two blades rotate at different speeds, one usually about twice the speed of the other, resulting in a lateral pulling of the material and divisions into two troughs, while the blade shape and difference in speed causes end-to-end movement.

• After mixing the material is removed by opening the lid.

• Material with similar size and density mixes faster than the materials with density difference and particle size change.

Uses:

1. For granulation during tablet manufacturing.

2. Semi-Solid mixing.

3. Commonly used in bakery.

Advantages:

1. Minimum dead space during mixing.

2. Suitable for solid-solid and semisolid mixing

Disadvantages:

1. Fixed speed.

2. Batch type only: No continuous operation.

Commonly Asked Questions:

1. Define Mixing. With help of a diagram describe the principle, construction and working of the Sigma Blade Mixer.

2. Write a short note on Sigma Blade Mixer.