Metal deforming – By extruding through orifice – Pressure or velocity conditioning
Patent
1998-02-04
2000-05-16
Tolan, Ed
Metal deforming
By extruding through orifice
Pressure or velocity conditioning
72269, 72467, 761074, B21C 3100
Patent
active
060620595
DESCRIPTION:
BRIEF SUMMARY
The invention relates to extrusion dies used for producing elongate profiles in metal (such as aluminium) plastics etc. In an extrusion process it is necessary for all parts of the material being extruded to pass through the die at substantially the same velocity, since if this is not the case the extruded profile is likely to be deformed.
As is well known, in an extrusion die the velocity of the extrusion material through the die, at any particular region of the die cavity, depends on the width of the die cavity in that region, its position relative to the centre of the die, and the bearing length of the die cavity (i.e. its length in the extrusion direction) in that region.
Since the width and position of each region of the die cavity are essentially determined for any particular profile to be extruded, it is normally necessary to control the velocity by adjusting the bearing length of the die cavity in different regions thereof so that the velocity of extrusion material is as uniform as possible through the whole area of the die cavity. Thus, a narrow part of the die cavity will require a shorter bearing length than a wider part of the cavity in order to achieve the same velocity.
This required variation in bearing length (known as the bearing contour) is normally achieved by forming in the back face of the die, i.e. the face furthest from the billet of material to be extruded through the die, an exit cavity which corresponds to the general shape of the die cavity plus an all-round clearance. The depth of the exit cavity is then varied so as to adjust the effective bearing length of the die cavity itself.
Various methods of this kind for manufacturing an extrusion die are described, for example, in British Patent Specifications Nos. 2143445 and 2184371.
There are numerous well known methods and techniques for providing the required correlation between bearing length and die cavity shape and position in order to achieve uniform flow. For example, the required bearing lengths may be achieved by trial-and-error methods based on the knowledge of an experienced die designer or, increasingly, computer programs are available to calculate required bearing lengths from the shape and position of the die cavity.
However, the extrusion dies resulting from such prior art methods may suffer from certain disadvantages. For example, the surface of the extruded profile may be longitudinally marked by a part of the die cavity where there are two adjoining regions of significantly different bearing lengths, as may frequently occur. Furthermore, since the die cavity itself has to be worked on and adjusted to control the flow of extrusion material, it may not be possible to form the die from a material which cannot be readily worked, or to provide it with a surface finish, such as nitriding, which might otherwise be desirable to give a better finish to the profile. It would therefore be desirable to achieve substantially uniform flow through a die cavity which has a substantially uniform, fixed bearing length so as to avoid marking of the profile due to changes in bearing lengths and to allow the die to be formed from a material, and have a surface finish, to give the best possible strength and wear resistance as well as to provide the finest possible finish on the extruded profile.
One method of achieving such an effect is described in European Patent Specification No. 0569315. In the method described in that specification, there is provided on the front, or entry, side of the die cavity an enlarged entry cavity the sides of which converge as they extend towards the cavity in the extrusion direction so as to provide an "entry angle". This "entry angle" is calculated in reciprocal ratio with the width of each region of the die cavity. Selection of different entry angles to different regions of the die cavity thus controls the velocity of extrusion material towards the die cavity in such manner that, at the entry to the die cavity, the velocity of the extrusion material at each region is such as to result in a substantially
REFERENCES:
patent: 2671559 (1954-03-01), Rosencratz
patent: 2894625 (1959-07-01), Harris et al.
patent: 2968835 (1961-01-01), Weston, Jr. et al.
patent: 3014583 (1961-12-01), Huffman et al.
patent: 3782164 (1974-01-01), Felker
patent: 3973428 (1976-08-01), Lugosi
patent: 5095734 (1992-03-01), Asher
patent: 5756016 (1998-05-01), Huang et al.
patent: 5870922 (1999-02-01), Rodriguez
Ailsa Investments Limited
Tolan Ed
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