Metal deforming – By extruding through orifice – With cutting
Patent
1982-01-13
1984-07-17
Larson, Lowell A.
Metal deforming
By extruding through orifice
With cutting
722735, B21C 2502, B21C 3504, B21C 3506
Patent
active
044598378
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
Technical Field
This invention relates to a method of indirect extrusion of metal and, in particular, to an indirect extrusion method wherein container cleaning is simultaneously executed in the course of extrusion, and discard such as billet residual unextruded which closely adhered or clung on the die is effectively cut and separated by means of a shear.
Background Art
As a method for extruding a billet, metal material, direct extrusion has been conventionally prevailing as a main stream. Indirect extrusion method has however been in recent days adopted in some quarters because of its merit of producing comparatively less friction loss in the course of an extrusion process.
The indirect extrusion method referred to herein means a method for extruding a billet through a die without relative movement between the container and the billet. Further concretely it means a billet extrusion method in which an axially movable container, with one opening end of a billet charging hole disposed axially through a central portion thereof being closed by an extrusion or press ram, is moved while accommodating a billet and a die put therein toward a stationary hollow die stem concentrically arranged therewith.
When such indirect extrusion method is put in practice, however, treatment of thin outer layer of a billet comes up as an important problem. That is because there are generally some kinds of impurities on the surface of billets which are feared to give rise to various undesirable defects to produced articles when introduced thereinto. A device of making the diameter of the die slightly smaller than the inner diameter of the billet charging hole, for preventing introduction of the outer layer or shell of the billet into the produced articles by leaving the outer layer as a shell in the billet charging hole when the extrusion is carried out, has been developed as an effective measure to solve the problem and fairly widely practiced. In this method, however, the shell left in the billet charging hole after a stroke of extrusion must be removed, that is to say, a container cleaning cycle of removing the residual shell in the hole by utilizing some means such as a dummy block used in the extrusion is needed while moving the container or an extrusion ram on the other hand. It inevitably makes the cycle time of extrusion longer.
For the purpose of eliminating the container cleaning cycle, a sort of die having a two-stepped structure has been developed. This sort of two-stepped die is provided with a pair of large diametered portions, having a slightly smaller diameter than the inner diameter of the hole of the container, on either axial end thereof, such that the shell produced in the course of an extrusion stroke is accommodated in an annular space between the pair of large diametered portions. This device of die does not leave the shell in the hole, eliminating the container cleaning cycle indeed. It still leaves a problem how to remove the shell accumulated in the clearance of the die, because the die is secured on a die-stem. Another demeritorious problem inherent to this device is deformation and misaligning of axes of the die-stem observed when the discard consisting of the residual billet, the dummy block, etc., is severed off the die.
A free die or a loosed die has been, on the other hand, developed, wherein the die is not secured on the die-stem at all when extrusion is conducted, in consideration of inherent disadvantages in the conventional attached-die system, where the die is fixed on the end of the die-stem when extrusion is carried out, for example, a weak point feared at the fixing place of the die, scratching or damaging of the inner surface of the container hole by the shell clung to the outer surface of the die. In this free die system there is still a serious problem how to cut off, in every cycle of extrusion, an integrated block consisting of the die, the residual billet left there, the dummy block, etc., from the produced articles. Two ways are generally thought of the severance o
REFERENCES:
patent: 3522721 (1970-08-01), Whiting
patent: 4056964 (1977-11-01), Shibasaki et al.
patent: 4342212 (1982-08-01), Sibler
patent: 4430877 (1984-02-01), Asari
Hayashi Hiromasa
Mohri Eiichi
Larson Lowell A.
Sumito Light Metal Industries, Ltd.
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