Combined Rod and Tube Extrusion Presses

Application of the early vertical tube extrusion presses was confined to the manufacture of small tubes of up to about 20 mm diameter in heavy metals. They were designed for a pressure capacity of 300 tons and provided with a gently curved runout table for a tube length of 5 to 6 m. The vertical press was preferred to the horizontal type because of ease of access and higher efficiency. 

The design of the early vertical tube extrusion presses was simple and cheap. They were of the down-stroking type and built in frame construction. No special piercing equipment was provided since the billets extruded were only small ones. The mandrel w as rigidly inserted in the extrusion ram and extrusion is performed on the without shell method, when the ram has only a little clearance in the container. The heavy metal 

Container and container-holder are rigidly attached to the container support d by four bolts c. This support is aligned to the center of the press by four lateral setscrews (not shown in the sketch) and is provided with a U-shaped slot, open to the outside, through which the die slide e which carries the die, is passed. If the die is to be removed, first the four bolts on the container-holder are released, whereupon the die slide is pulled out of the support manually with the help of a rod and the die which has dropped off, is picked up with a hook. 

The container is symmetrical and may be used from either end. It is centered to the container support in an annular groove. The container is held in the holder by a bayonet lock. When dismounting the container, the crosshead is lowered until the stroke limiting collar / makes contact. Then the clamping bolts are screwed in tap-holes specially provided for this purpose in the container, and with the crosshead moving up the container is lifted out. The container-holder is provided with a resistance heating system to heat the relatively small container. Its outer jacket is well insulated to prevent thermal losses. 

Vertical COO-ton tube preE5 of simple desien wJtlioiit piercer 

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In many rod and tube extrusion presses the main cylinder is combined with the pullback and piercer cylinders in one piece of steel casting to form a cylinder-platen which is provided with integrally cast lugs for the columns (see Fig. 88 and 89). The number of the auxiliary cylinders and their arrangement around the main cylinder have lead to a great variety in cylinder-platen designs. 

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...

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...

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

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)...

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