Roll-type extrusion presses

These machines, most often known as pellet mills , use compaction of material caught in the nip between rolls to force the material in a plastic state through holes in one or both rolls. Adjustable knives shear the rod-like extrudates into pellets of the desired length. Compacting pressure is determined by the resistance of material in the holes. This resistance is a function of hole length divided by hole diameter raised to the third power [21]. Spe- [Pg.115]

Rotation of die and roller pressure forces material through die, compressing it into pellets. [Pg.116]

The most popular pellet mills employ a ring-type die and two or three rollers mounted in a vertical plane as in Fig. 5.15. Power is applied to the die [Pg.116]

Die characteristics Size up to 26 in. inside diameter X approx. 8 in. wide [Pg.116]

The gear-type pellet mill of Fig. 5.14e is especially useful for difficult applications in which feed material tends to slip away from the nip of smooth rolls [21]. This may occur when the resistance of the die holes is high as with small diameter pellets (e.g. 1 mm diameter). The gear teeth catch the material and force it through the holes higher compaction ratios and more uniform pressure distribution are claimed. [Pg.117]

Roll-type extrusion presses are described in Section 2.3.2. [Pg.112]

Fig. 5.14. Various designs of roll-type extrusion presses or pellet mills [21]. (a) Horizontal perforted plate die. (b) Extrusion through both side-by-side rolls, (c) Outward extrusion through large die roll, (d) Extrusion through only one of side-by-side rolls, (e) Die holes at root of intermeshing gears.

Extrusion presses of the piston type, roll type, and screw or auger type are in use. [Pg.113]

Wrought materials are produced by extrusion, rolling and press forging in the temperature range of 300-500°C. Wrought alloys are of two types, namely those containing zirconium and those devoid of zirconium. The typical composition and mechanical properties are noted in Table 4.68. [Pg.271]

Pellet Mills. Pellet mills differ from roll briquetting and compacting machines in that the particulates are compressed and formed into agglomerates by extrusion through a die rather than by squeezing as they are carried into the nip between two rolls. Several types of equipment that use the extrusion principle are available. The die may be a horizontal perforated plate with rollers acting on its upper surface to press material through the plate. [Pg.117]

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