MACHINERY | DOSING AND FEEDING
Right: Maguire blenders are available in eight sizes and can be configured to handle up to 12 materials
from a dryer or other processing step, is to main- tain the temperature of the material rather than allowing it to cool down before feeding. “This requires the ability to feed warm to hot ingredi- ents,” Siffert says. “The feeder design must include heat-resistant materials while ensuring critical parts are insulated and appro- priate seals are used.” Recycled materials, such as shredded films,
present feeding difficulties due to their low bulk density. Siffert says feeders for these materials must be able to handle high volumes with accuracy. ”It has been shown that bottom-agitated silos with screw feeders underneath, in combination with a gravimetric weigh belt feeder, are the best solution to bring the shredded film sheets into the extrusion process,” he says.
Below: Entek’s Vacuum Feed Technology works with fluffy fillers to achieve higher output compared to conventional atmospheric venting
Recycling solutions Compounders and processors are increasingly installing additional feeders for recycled material used for recipes that combine recycled and virgin resin. “Testing is critical prior to purchasing new equipment, since the recycled material isn’t always as consistent as virgin material. The feeder selected needs to be able to handle the variability,” says Rene Medina, Executive Vice-President for Gericke in the US. Medina says Gericke’s GAC 232 family of feeders is especially useful for handling difficult-to- feed materials as it uses a proprietary gearbox design that supports two different speeds from one electric motor. “Plastics processors are looking for economical solutions to incorporate additional materials, more diverse materials, and changing material content in their final product,” according to Frank Kavanagh, Vice President of Sales and Marketing at Maguire. He says the company’s Maguire Weigh Scale
Blender provides that capability, offering the ability to handle up to 12 different components. The units are offered in eight sizes. “Each blender is configured with the appropri-
ate size hopper and dispense device for the given material (pellet, granular, flake, powder or liquid). Without the proper dispense device, a blender cannot achieve a repeatable, accurate dispense,” says Kavanagh. He says the control — in Maguire’s case a touch-screen unit capable of controlling third-party loading systems — is also a key piece of the system. “The software allows [dispensing] of minute quantities of additives, while maintaining an accuracy of 0.1% of set point,” he claims.
Venting limitations Feeding “fluffy” (low bulk density) fillers is a common challenge for compounders. “These fillers tend to draw large amounts of air into the extruder, causing a volumetric limitation which restricts output rates,” says Dean Elliott, Entek’s Technical Processing Manager. Another problem is that the fluffy powders can potentially be discharged through the atmospheric vents traditionally used to vent out the air. Entek’s VFT (Vacuum Feed Technol- ogy) offers a solution to both. “VFT ultimately densifies the material prior to entering into the extruder, making the material easier to feed,” Elliott says. The company claims that processors experiencing volumetric limitations due to fluffy fillers can achieve much higher throughput, as much as doubling output rate, by using VFT. Entek’s VFT technology is available on all of the US-based company’s twin-screw extruders. Trials can be conducted to configure the extruder for the custom- ers’ materials and to demonstrate the throughput rate improvements that can be obtained compared to traditional extruder atmospheric venting. Although some formulations need special designs to optimise feeding, other formulations can benefit from streamlined, simple equipment. Coperion K-Tron’s new ProRate Plus Feeder Line is an economical solution for simple applications in
14 COMPOUNDING WORLD | July 2022
www.compoundingworld.com
IMAGE: ENTEK
IMAGE: MAGUIRE
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