Principle, Construction, Working, Uses, Merits and Demerits of Sigma Blade Mixer : Pharmaceutical Guidelines -->

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Principle, Construction, Working, Uses, Merits and Demerits of Sigma Blade Mixer

It is shearing which is achieved by inter-mesh sigma-shaped blades in these mixers, where very viscous materials are handled.

Sigma Blade Blender

Principle

It is shearing which is achieved by inter-mesh sigma-shaped blades in these mixers, where very viscous materials are handled. Through this mechanism, the material is both displaced laterally and transversely. By pulling, shearing, compressing, kneading, and folding the viscous mass of material against the walls of the mixer trough, the blades pull, shear, compress and fold the material. Depending on the tangential or overlapping action of the blades, and the rotation speed of the blades, this happens to varying degrees. Blade helix angles can be modified depending on what type of shearing is required.

Construction

Located horizontally inside each trough of the bowl, the blades have the shape of the Greek letter sigma (Σ). The blades and the walls of the vessel have a low clearance (~ 2 mm). Low clearances produce high shear.



Working

Typically, powder is loaded to 40 to 65 percent of the mixer's total capacity through the top of the trough. Due to the dust, the mixing process must be done in a closed container. The driving system includes a motor, a gear reducer, couplings, gears, bearings, and seals that make the blades move at a different speed. A shearing action occurs between the blades and wall of the trough as the material moves up and down. Additionally, lumps and aggregates are broken with perforated blades. Mixing vessels can be tilted, valves can be used on the bottom, or a screw can be used to discharge the material. Within 10 to 30 minutes, a homogeneous mixture can be obtained with a mixing homogeneity of up to 99%.

Uses

  • During the manufacturing of tablets, capsules, and pill masses, Sigma blade mixers are used for wet granulation.
  • Both solid-liquid and solid-solid mixtures can be made using it.
  • As well as adhesives, chemicals and chewing gum, hot-melts, inks and pigment products, soaps and detergents, sugar pastes, and other products, Sigma blade mixers are also used in the mixing of food and confectionery products.

Merits

  • It leaves fewer dead spots during mixing when using a sigma blade mixer.
  • It is suitable for mixing and kneading sticky products and highly viscous masses.
  • As the blades are perforated, it can be used for breaking lumps and aggregates.
  • Close the trough chamber and maintain a low temperature to prevent losses such as volatile solvent during mixing.

Demerits

  • Sigma blade mixers consume a great deal of power compared to other mixer types.
  • It's possible that the mixing tank has dead spots.
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Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of Pharmaceutical Guidelines, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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