PerMix PSG series Sigma Mixer, which is also known as Double Sigma Mixer, or Double Z Blade Mixer, is used for the mixing-kneading of materials with very high viscosity (over 500,000 cps). If a screw extruder is applied for discharging, the mixer is also called Sigma Mixer Extruder, or Mixtruder. With its unique design of Z-shaped mixing tools installed in two semi-cylinders, PSG Sigma Mixer is able to provide a combined functions of compressing, stretching, folding, kneading & mixing, which makes it widely used in the chemical, food, sealing compound and paint industries, among others.

In the PerMix PSG series Sigma Mixer, there are two special designed Z-shaped rotating elements installed in a W-shaped chamber, the intersection of which forms a saddle piece and meeting tangentially just above the saddle. They rotate at different speeds (usually in the ratio of 3:2) and in opposite direction.

The mixing action is a combination of bulk movement, smearing, stretching, folding, dividing, and recombining as the material is pulled and squeezed against blades, saddle, and side walls. Continually new layers of material are compressed and folded over one another and are subjected to shearing forces. New surfaces are formed and the components can penetrate.

The blades, which are ground and polished, successively sweep all points of the trough surface during each revolution, at the same time dividing the batch continuously across the saddle piece and thereby rapidly affecting a perfectly homogeneous mix.


The large number of options available for the PerMix PSG Sigma Mixer (Extruder) enable it to operate as a general purpose mixer or perform particular functions:

  • Quick Disassembly & Easy-clean Design: With “easy-clean” design, the end plates, trough, cover, arms and screw can all be disassembled quickly without a tool for complete cleaning.
  • Lab-size for R&D: Full volume of mixer can be 1 L, 3L, SL, 1 0L, 1 SL.
  • Overlapping Arms: Overlapping arms provides more shearing to the product.
  • Vacuum Execution: PerMix designs the Sigma Mixer (Extruder) to work under mild vacuum or high vacuum up to -0.95barg.
  • Welded Jacket for Heating & Cooling: Jacket for heating/cooling by steam, thermal oil, or water can be welded around the trough and/ or end plates. ASME/PED certificate is optional for high pressure operation.
  • Bored Arms for Heating & Cooling: Arms, screw and main shafts can be designed with heating/cooling to offer more contact areas for heat exchange.
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