Tube and Rod Extrusion Press

Fig. 55. Light metal sections on rnnont and conveyor bed of a 12,000-ton tube and rod extrusion press (Courtesy of Dow Chemical Co., Madison, US.A.)...

The early extrusion presses were mainly used for the production of round rod and other solid sections. Tubes were manufactured by attaching a mandrel to the extrusion ram and forcing a biUet which had been provided with a central bore, through an annulus formed by mandrel and die. The billet was not pierced in the container as the material available for the mandrels could not withstand the high stresses occurring. This method of extruding tubes was of course imperfect. Steps were, however, taken to improve machinery and materials which led finally to the combined tube and rod extrusion press in which the solid billet is pierced by the mandrel prior to extrusion. Simultaneously there were developed vertical presses for the extrusion of small diameter tubes. 

Combined tube and rod extrusion presses are sometimes designed so as to be suitable both for direct and inverted extrusion. In the direct or Dick extrusion method, as illustrated in Fig. 56 a, the billet lies between extrusion ram and die. Consequently, frictional resistance has to be overcome on the wall of the container which has its highest value at the beginning of the extrusion cycle and decreases in accordance with the reduction in length of the billet. When extruding by the inverted method. 

Fig. 89. Combined tube and rod extrusion press in three-column design with laterally arranged drive of the piercer and separate pullback devices for main ram and piercer mandrel...

An advanced tube and rod extrusion press in three-column construction with horizontal die slide is illustrated in Fig. 97 and 98. The die slide is brought into its various working positions by a drive unit arranged behind the counterplaten. Extruding having been completed, the die is cleared of the slide during the return motion of the container, so that... 

Fig. 157. Combined 12,000-ton tube and rod extrusion press for working of light metals in four-column construction with three hydraulic cylinders arranged one above the other. Maximum billet diameter 800 mm, maximum billet length 1,800 mm. Courtesy of ALCOA, USA (By Schloemann, Diisseldorf)...

Fig. 161. Pressure water accumulator for combined tube and rod extrusion press shown in Fig. 1.58...

The various hand-lever controls for tube and rod extrusion presses are arranged in such a way that the operator can closely watch the ram motions and the charging operations. A drawback to this system is the large space required and the distances between the various hand-levers, on account of which the operator has to change his position frequently... 

Fig. 181. Eemote-control desk of a tube and rod extrusion press (By Hydraulik, Duisburg)...

The main control of tube and rod extrusion presses - whether accumulator driven or directly driven by variable-delivery oil-hydraulic i ressure pumps - has to meet much higher demands. They must be able to regulate the working speed of the press at least in steps, and set the plunger motions to advance, stop, and return. This could be attained by arranging a number of intermediate switches on the control shaft, which, however, is not made use of, as there are better and simpler methods. 

In tube and rod extrusion presses, stepless remote-controls are employed almost exclusively for the regulation of the pressing speed. In presses which are driven by a hydraulic accumulator with a constantly operative and rather uniform pressure potential, regulation is done by means of a throttle gate valve or a throttle valve. The speed of directly driven oil-hydraulic presses is controlled by the infinite regulation of the delivery of the pumps. 

Fig. 183. Stepless electric remote control of a combined tube and rod extrusion press...

A tube and rod extrusion press is to be capable to extrude copper and brass tubes of a maximum outside diameter = 120 mm, a 5 mm wall and in minimum lengths of 8 m, over a mandrel that is held in the die, under the following conditions ... 

TUBE AND ROD EXTRUSION PRESS Table 26. Consumption of Pressure Water and Cycle Time... 

With presses operating at slow speed rates, i. e. lead wire- and lead pipe presses, cable presses and rod extrusion presses, the working stroke is of relatively long duration - 10 to 20 minutes not being extraordinary -so that the accumulation of pressure fluid would make no sense. For tube extrusion presses, especially those working on heavy metals and at speed rates of up to 200 mm/sec, the accumulator drive will be preferred as the direct pump drive would be very expensive on account of the high pump capacity required. 

Fig. 96 shows an older light metal tube extrusion press, built in 1936/37, in frame construction, being the first press to be equipped with a horizontal die slide and a moving container, even before using it in rod extrusion presses (see p. 83). 

Fig. 118. Combined 12,000-bon tube and rod press in four-column design with 3,000-ton piercer for the extrusion of max. 800 mm diameter and 1,800 mm long light metal billets. Foreground 1,000-ton capacity shape stretcher. Courtesy of Dow Chemical Co., Madison USA (By Hydraulik, Duisburg)...

A few patents have been issued covering the use of screw presses [39], but they do not include details of the design of the presses. However these do not differ from the screw presses widely used for extrusion of plastic rods, tubes and other shapes. A detailed description of the screw presses used in plastics technology can be found in monographs [40, 41]. A diagrammatic representation of a screw press is given in Fig. 266. 

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