A BMC Compound Sigma Mixer (also known as a Sigma Blade Kneader or Z-Arm Kneader) is a specialized industrial mixing machine designed for processing high-viscosity, dough-like, and sticky materials, particularly Bulk Molding Compound (BMC). BMC is a thermoset composite material reinforced with glass fibers, commonly used in applications like electrical enclosures, automotive parts, and construction products (e.g., manhole covers). This mixer ensures thorough kneading, shearing, and homogenization of BMC formulations, which typically include unsaturated polyester resin, fillers, glass fibers, and additives.
BMC Compound Sigma Mixer Video
Key Design and Working Principle
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Structure: It features a double-arm configuration with two interlocking Z-shaped (Sigma) blades mounted horizontally in a W- or U-shaped trough/container. The blades rotate toward each other at the same or differential speeds (typically 30-60 RPM), creating close clearances (1-2 mm) against the trough walls and each other.
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Mixing Action: The process involves smearing, stretching, folding, compressing, dividing, and recombining the material. This tangential or overlapping blade motion pulls, shears, and kneads the viscous mass, achieving up to 99% homogeneity without dead zones.
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Capacity Range: From laboratory scale to production scale, with working capacity at ~60% of total volume.
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Jacketed Design: The trough is often jacketed for heating or cooling to control temperature during mixing.
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Discharge Options: Hydraulic tilting, bottom valve, or integrated screw extruder for efficient unloading of the heavy paste.
Applications Specific to BMC Compounds
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Ideal for mixing BMC/DMC formulations, including glass fiber composites, resins, pigments, and thickeners.
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Used in industries like composites, plastics, rubber, chemicals, and automotive for producing molding intermediates that undergo injection, compression, or transfer molding.
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Not typically vacuum-equipped for BMC, but can handle low- to high-viscosity pastes.
Advantages
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Superior for fibrous, high-viscosity materials where standard mixers fail.
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Energy-efficient for thorough dispersion.
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Durable construction ensures longevity and easy cleaning.
Salient Features of Sigma Mixer Machine
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Available in Stainless Steel 316, Stainless Steel 304 and Mild Steel materials.
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Stainless Steel polish to matt & mirror finish as per customer’s requirements.
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Mild Steel finish with one coat of red oxide and two coats of epoxy paint.
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Discharge option of hand wheel operated (manual) or hydraulic operated (automatic) offered.
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Jacket for heating or cooling application can be offered.
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Mineral wool insulation with cladding on jacket.
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Tangential designed ‘Z’ blades offered for uniform mixing.
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PTFE made shaft sealing provided for food grade compatibility.
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Minimum gap between trough inner shell & blades removes possibility of sticking product.
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On demand Spray system, vacuum system
Optional Features/Accessories of Sigma Mixer
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Liquid Spray System
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Vacuum System
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Blades Cooling Arrangement
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Screw System
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Automatic Valve Discharge System
Process Operation of BMC Compound Sigma Mixer
In Sigma mixer tangential action of mixing and kneading obtained by ‘Z’ type (SIGMA) shaped kneading blades, which rotates very accurately at different speed towards each other causing product to be transferred from one end to another end. Discharge of the finished product is achieved by tilting the container or through the valves at the bottom or by means of an extrusion screw beside the container.
The mixing action is a combination of bulk movement, stretching, folding, dividing, and recombining of the material. The shearing & tearing action of the material against blades and the side walls causes size reduction of the solids. After the time period required for sterilizing the batch has elapsed, the heating circuit shuts of the pneumatics damper (exhaust) opens and cooling operation commences.
In the tangential design, the blades rotate in the trough meeting tangentially. The front blade generally rotates faster than the rear blade usually in the ratio of 3:2. Tangential blades are generally used for material of higher viscosities such as adhesives, rubber compounds, flush colors, dyes, and pigments.
In the overlapping design, the blades overlap above the saddle of the container. Due to the overlapping action, it is necessary that the relative position of the two blades is unchanged, and as a result, both the blades rotate at the same speed. Materials that flow freely or creep down into the blades are mixed using the overlapping blade action. This design offers a faster interchange of material from one blade compartment of the mixer to the other. Overlapping blade action is used for materials of lighter viscosities such as carbon pastes, clay coating, creams, and ointments. The overlapping blade produces a lower kneading and shearing compared to the tangential blade action.
Technical Specification of Sigma Mixer Kneader
| Model | Capacity – Liters | Motor (H.P.) | ||
| Working Capacity approx. | Gross Capacity approx. | General | Heavy Duty | |
| ASM – 50 | 50 Liters | 80 Liters | 5 H.P. | 7.5 H.P. |
| ASM – 75 | 75 Liters | 110 Liters | 7.5 H.P. | 10 H.P. |
| ASM – 100 | 100 Liters | 150 Liters | 10 H.P. | 15 H.P. |
| ASM – 150 | 150 Liters | 200 Liters | 15 H.P. | 20 H.P. |
| ASM – 200 | 200 Liters | 300 Liters | 20 H.P. | 25 H.P. |
| ASM – 400 | 400 Liters | 550 Liters | 30 H.P. | 40 H.P. |
| ASM – 500 | 500 Liters | 750 Liters | 40 H.P. | 50 H.P. |
| ASM – 750 | 750 Liters | 1150 Liters | 50 H.P. | 60 H.P. |
| ASM – 1000 | 1000 Liters | 1500 Liters | 60 H.P. | 70 H.P. |
| ASM – 1500 | 1500 Liters | 2100 Liters | 75 H.P. | 80 H.P. |
| ASM – 2000 | 2000 Liters | 2600 Liters | 80 H.P. | 90 H.P. |
| ASM – 3000 | 3000 Liters | 3800 Liters | 100 H.P. | 120 H.P. |
* Power voltage can be adjusted as per customer’s domestic power voltage requirements.
* Rights of technical improvements & modification reserved.
* Illustrations & dimensions are shown for information purpose only.
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