Fractional Lobe Processor (FLP) and Fractional Geometry Technology (FGT)

Fractional Geometry Technology (FGT) is a technology used in elements design and manufacturing, whereas Fraction Lobe Processor (FLP) is combination of FGT elements used for specific applications with target outcomes. FGT and FLP are available only on STEER Omega series.

Though it is a fact that co-rotating twin-screw extruders evolved through the years, the ability to process certain shear and temperature sensitive materials is greatly enhanced in an extruder only with deeper flights. The increase in melt temperature due to the kneading elements at high speeds is solved by FGT with unequal tip angles. FGT can easily replace standard kneading elements. For example, in an eccentric tri-lobed kneading element, the small tip angle leads to higher wear rate. Increasing the tip-angle gives a circular shape to the element and reduces the free volume available in the extruder.

These elements continue to work as conjugate pairs while suiting the needs of twin-screw extrusion. The new element geometry provides greater flexibility in design of individual elements.

FGT is being applied on standard elements used in STEER’s extruder – the Omega series. The changes were made over the years, but we have been deploying the FGT-based elements since the last few months after successful tests and validation. The FGT elements are unique and cannot be replacement elements for other branded extruders and vice-versa.

The standard elements in Omega class extruder are being replaced by FGT-based elements where there is a need to finely control the compounding process to a great extent. Forty years ago, Erdmenger determined the need for fractional elements. Erdmenger said, “One disadvantage that was hitherto encountered in apparatuses of this type (twin-screw extruders) was that it was only possible to vary the dimension lying in the axial direction but not the dimension lying transversely to the axis, e.g. the thickness of the layer of material used, which often has an important effect on the transfer of heat or the transfer of material or the course of the reaction, which in practice is the most important alteration”.

The standard twin-screw elements have equal tip angles for all lobes. These limit the types of elements that operate in a twin-screw extruder if the geometry is based solely on the design of Erdmenger. For example, in an eccentric trilobed kneading element, the small tip angle leads to higher wear rate. Increasing the tip-angle gives a circular shape to the element and reduces the free volume available in the extruder. Elements having different tip-angles using FGT have been invented by STEER.

Using FGT, it is possible to finely control the compounding process than what is considered possible with standard elements. Processing of various materials with FGT elements have already been carried out. This involved processing of polymers with a high filling of carbon black, organic pigments, glass fibre, etc.

In an Erdmenger Bilobe Geometry system, Peak Shear is always present. This is experienced by 10% of the material. While many applications are shear-forgiving, many are shear-sensitive, requiring compromises on speed or quality. An innovative approach was required that minimizes shear peaks, while retaining self-wiping and adding new functionality. An infinite set of Elements are possible through FLP. It is possible to form screw, kneading blocks or mixing elements with any of these profiles with full self-wiping capability.

Standard/Feed Enhancement/Fractional Geometry elements are possible in an end-to-end trilobe eccentric fractional configuration. MFE (Melt Formation) Element is Capable of controlling the fusion process. End-to-End Fractional Lobe can ensure greater control over process by completely eliminating pressure peaks across entire screw.

In addition to ensuring Shear Uniformity, FLP performs Melt Temperature Reduction; Extensional Flow and Fiber Length Retention. While FGT focuses on fully filled zones, FLP addresses both partially and fully filled zones. FLP elements have the ability to control energy without stagnation; No perpendicular face to the flow; Reduces barrel and Screw Contact Area and are highly scalable. Omega FLP is ideal for sensitive polymers, pharma and food.