The Manufacturing Confectioner • January 2008 71

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The working method of an extruder isbased on the principle of theArchimedes screw technology and was

already being used in the 17th century. In

the beginning of the 20th century, extrud-

ers as production machines were used for

manufacturing plastics and other nonfood

materials.

An extruder is a machine which converts

viscous masses to solid masses by mechan-

ical pressure and/or with thermal treatment.

It presses the mass uniformly through a geo-

metrically shaped nozzle and forms it into

slabs, strands or individual pieces.

The pressure in an extruder varies

depending on the construction. Designs

from 1 to 300 bars (14 to 4,200 psi) and, for

special applications, even 700 bars (9,800

psi) can be achieved. Normal working tem-

peratures are between -18°C and 300°C (0°F

and 572°F).

Extruders are classified into two techno-

logical types: reactive extruders and process

extruders (Figure 1).

REACTIVE EXTRUDERS

In the reactive extruder materials are chem-

ically or physically modified and formed.

Fundamentals of ExtrusionExtruding technology was developed in the 17th century. It hasevolved into a variety of sophisticated machines that serve theconfectionery industry.

Hermann-Otto VongeheurHosokawa Bepex

Hermann-OttoVongeheur is cur-rently group directorof process technologyand R&D atHosokawa-Bepex. Hehas held machineryand process technol-ogy jobs at Winkler +Dünnebier, Jagenbergand Ziemann.

Figure 1

Process and Reactive Extruders

Process ExtrudersMechnical pressure

leads to geometrical formed products

Reactive ExtrudersThermal energy and pressure

lead to a physically or chemicallycharged structure