Square feed hoppers

Square feed hoppers with rapid compression usually work well with bulk materials with uniform pellet size. However, when there is a large variation in particle size and shape the square feed hopper is likely to cause conveying problems. This can happen for instance when regrind is added to the virgin material. For this reason it is better to use a circular hopper with gradual compression. 

At its base, the hopper empties into the feed throat through an opening. This opening in the feed throat is often circular or square. However, improved feeding has been measured when the opening is elongated along the barrel direction with dimensions of 1.5 screw diameters by 0.7 screw diameters [7]. 

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