Moulding Preparations Sigma Mixer

It refers to the compounding of viscous, dough-like materials for molding processes. This includes blending polymers, fillers, resins, pigments, and additives into a homogeneous, stiff paste suitable for rubber injection/compression molding, plastic compounds, thermosets, and similar applications.

Sigma mixers use counter-rotating Z-shaped blades in a U- or W-shaped trough to deliver intense shearing, kneading, stretching, folding, and compressing. This produces uniform dispersion of fillers and additives with no dead zones, which is essential for consistent molded product quality when processing extremely viscous and sticky materials.

The mixer is offered in Stainless Steel 316, Stainless Steel 304, or Mild Steel. Stainless steel can be finished to matt or mirror polish as required; mild steel receives one coat of red oxide and two coats of epoxy paint.

Tangential “Z”-type sigma blades rotate toward each other at different speeds (typically a 3:2 ratio), transferring material from one end of the trough to the other. The combined actions of bulk movement, stretching, folding, dividing, recombining, shearing, and tearing against the blades and side walls ensure homogenization and size reduction of solids.

Tangential blades meet at the edges, rotate at different speeds (usually 3:2), and provide stronger kneading/shearing—ideal for high-viscosity materials such as rubber compounds, adhesives, and silicone. Overlapping blades rotate at the same speed, allow faster material interchange, and are better suited to lower-viscosity materials; they produce less intense kneading. Tangential design is preferred for most moulding preparations

Discharge can be performed by hand-wheel (manual) or hydraulic (automatic) tilting of the container, through bottom valves, or via an extrusion screw located beside the container.

Yes. A jacket for heating or cooling (with mineral wool insulation and cladding) is available. Optional features include liquid spray systems, vacuum systems (especially useful for silicone to remove air bubbles), and blades cooling arrangements.

Models range from ASM-50 (approx. 50 L working / 80 L gross capacity, 5–7.5 HP) to ASM-3000 (approx. 3000 L working / 3800 L gross capacity, 100–120 HP). Both general and heavy-duty motor options are listed for each size, and power voltage can be adjusted to local requirements.

A minimum gap between the trough inner shell and the blades reduces sticking. PTFE shaft sealing is provided for food-grade compatibility, and the overall U-/W-shaped trough with counter-rotating sigma blades minimizes dead spots for consistent, high-quality batches.