Piston-type presses

Although die compaction is used most widely in applications (such as tableting in the pharmaceutical industry) requiring strict specifications for the agglomerate, there are a few applications in which piston-type machines are used simply to compress particulates into a larger size suitable for further processing without regard to fine detail. 

In the automotive industry and other metal working industries, coarse scrap metal particulates are compressed and recycled to melting operations 

Piston or ram type briquetting presses are operated as follows. The material to be briquetted is placed into a forming die which is closed on all but one side face. A close fitting ram or piston then enters into the die s open side and exerts the force required to produce the briquet. The briquet is then ejected or stripped out of the die. The ram or piston (which is also sometimes referred to as the stamp or punch) which enters into the die can be actuated either mechanically or hydraulically. A typical installation has the following characteristics  

Die diameter Press rating Oil pressurizing pump Feed material Briquet size Production rate 

In the pharmaceutical industry large, often poorly-formed, tablets or slugs are made from fine cohesive powders in large capacity tablet presses and then comminuted to form a granular feed suitable for final tableting [10]. Slugs are typically 1 or 2 in. (2.5 or 5.1 cm) in diameter and perhaps in. (1.3 cm) thick. Results comparable to those accomplished with this piston and die method are also obtained by roll compaction followed by granulation (see Section 2.2). 

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Piston-type presses are not suited to large tonnages when a small briquet is required. Their reciprocating nature is a disadvantage since this produces non-uniform loads on the drive motors [11]. 

Chapter 5. Pressure methods Piston-type presses... 

Pressure methods Unidirectional, piston-type compaction 1. Large briquets formed (e.g. from scrap metal turnings) by piston compression into die. Briquetting, compacting, preforming Heavy duty compacting presses... 

Piston-type extrusion presses are described in Section 2.3.1. 

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

Fig. 5.12. Schematic diagram of the piston-type extrusion briquetting press [7].

Fig. 5.13. Diagram of the head section of a piston-type extrusion briquetting press [17]-...

Modem piston-type extrusion presses contain multiple stamps and moulds of twin, triple or double-twin construction [7]. At an operating speed of 100 rpm, a triple-type press produces 10.5 tons/h (9.5 Mg/h) and a double-twin type press 16 tons/h (14.5 Mg/h) of lignite briquets. Power requirements are in the range 22 to 35 kW-h/ton (30 to 47.5 hp-h/ton) depending on the feed properties. 

Scorim Process or SP (Cinpres-Scorim), Rheomolding Process or RP (Thermold s), and the Press Alpha Process or PAP (Sumitomo Heavy Industries and Sankyo Chemical Engineering of Japan) processes are examples of this method. The SP multi-live feed molding process where two packing pistons oscillate 180° out of phase and eliminate weld lines, etc. The RP system provides 3-D orientation based on the concept of melt rheology as a function of vibration frequency and amplitude as well as temperature and pressure. The equipment utilizes piston/type melt accumulators set up adjacent to the melt stream of the plasticator. Piston oscillates back and forth. The PAP system uses compression pins that are... 

Fig. 4.6.9. Example of piston type column end fitting suitable for water and organic solvents (after Ref. 19). 1, fixed tube 2, movable tube with pressure plate 3, rubber O-rings 4. rings 5. polytetrafluoroethyl-ene seal pressed toward column wall by rubber rings 6, body of the end fitting made of plastics or inox steel 7, filter 8, column 9, inlet capillary.

Contrary to inner gliding surfaces, cutting laminations are usually a-ligned in the direction of extrusion. As they are created exclusively in the die or pressure head, these cutting laminations can be found with ill types of extruders, i.e. with piston extrusion presses as well as auger extrusion units. 

Flow laminations, laminations caused by inner gliding surfaces, and cutting laminations, all can be distinguished to varying degrees in the extrusion of plastic bodies, independent of the extrusion method employed, e.g. piston extrusion presses, single-shaft extruders, twin-shaft extrusion machines or rotory-type extruders. 

Fixed-volume and variable-volume pumps are the two types commonly applied in the press application. Fixed-volume pumps are normally vane type and are used for fixed-speed presses and for auxiliary circuits such as filtering, cooling, and pilot pressure. Variable-volume pumps are normally radial or axial piston type and are used for variable pressing speeds and pressure compensated circuits. 

Compression moulding is a simple and flexible method of fabrication. The polymer— dmg mixture is ground or spray-dried into a fine powder, placed in a piston-type mould, and compressed into a flat wafer with a hydraulic press. Compression moulding is usually done at 5—10°C above the glass transition temperature of the... 

In the two-column press, Fig. 27 and 28, and the frame-type press, Fig. 26, a plunger piston has been chosen instead of a disk piston. Although... 

There are presses in which a cylinder fitted with a die and a system of filters is filled with the dough and turned through by 180°. In other presses, e.g. those of the Champigneul type, the bottom of the cylinder, when filled with the rammer, is formed by a separate piston. When, however, the cylinder takes up the position... 

In practice, the high-pressure polycondensation of the salt monomers producing polyimides was carried out by using a piston-cylinder type hot-pressing apparatus with the use of a Teflon capsule as a reaction vessel (see Eq. 5) [34]. 

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