US 3782164 A
A method and die for drawing a complex elongated structural member formed with at least one extending fin which consists of drawing said member through a die of substantial complimentary orifice configuration disposed to effect a predetermined gage reduction of said fin, the metal working surface of said die disposed to effect a gage reduction of said fin being inclined in the drawing direction so that said fin is gradually and sequentially engaged by said working surfaces from its innermost surface to an unrestrained edge. The orifice portion of the die corresponding to said fin extends laterally from the direction of drawing a distance greater than the lateral growth of the fin to avoid any lateral restraint. Also, where said member has a cross-bar which does not terminate on a free edge said working surfaces are optionally inclined in the drawing direction to an intermediary position between the ends of the cross-bar where there is provided in the die orifice or the cross-bar a local relief of restraint to receive metal flow.
Claims available in
Description (OCR text may contain errors)
United States Patent 191 Felker Jan. 1, 1974 METAL DRAWING DllE Primary ExaminerRichard J. Herbst  Inventor: Theodore S. Felker, 651 Rockhill Assistant Exammer M Keenan Ave Kettering Ohio 45429 Att0mey.lohn L. Gray et a1.
 Filed: Feb. 19, 1971  ABSTRACT  Continuation-in-part of Ser. No. 17,648, March 3, 1970, abandoned, which is a continuation-in-part of Ser. No. 686,064, Nov, 28, 1967, abandoned.
 US. Cl. 72/274, 72/467  Int. Cl. 1321C 3/00  Field Of Search 72/467, 274, 276, 72/377  References Cited UNITED STATES PATENTS 1,929,695 10/1933 Julien 72/274 3,024,896 3/1962 Scribner 72/467 2,402,281 6/l946 Green 1 1 72/467 3,298,219 1/1967 Schober 72/377 FORElGN PATENTS OR APPLICATIONS 546,589 3/1932 Germany 72/274 A method and die for drawing a complex elongated structural member formed with at least one extending fin which consists of drawing said member through a die of substantial complimentary orifice configuration disposed to effect a predetermined gage reduction of said fin, the metal working surface of said die disposed to effect a gage reduction of said fin being inclined in the drawing direction so that said fin is gradually and sequentially engaged by said working surfaces from its innermost surface to an unrestrained edge. The orifice portion of the die corresponding to said fin extends laterally from the direction of drawing a distance greater than the lateral growth of the fin to avoid any lateral restraint. Also, where said member has a crossbar which does not terminate on a free edge said working surfaces are optionally inclined in the drawing direction to an intermediary position between the ends of the cross-bar where there is provided in the die orifice or the cross-bar a local relief of restraint to receive metal flow.
13 Claims, 13 Drawing Figures PATENTEDJAH 1 I974 SHEET NF 5 THEODORE S. FELKER INVENTOR PATENTEUJM 1 I574 SHEEI EUF 5 PATENTEDJAH 1 I974 SHEEI 30$ 5 THEODORE S. FELKER INVENTOR SHEET 4, BF 5 PATENTEDJAH S B L E C R O F M R D O O: Q m w 4 k O O: O 5 2 6 3 6 O m; w. m. Mu M V a. w. m. m m m s 5 m w lull! mw wmo2 mw mmowo DIMENSIONAL CHANGES VS. DRAW FORCE Fi 9 THEODORE s FELKER INVEN TOR SHEET 5 OF 5 PATENTEDJM? METAL DRAWING DIE This application is a continuation in part of US. Pat. application Ser. No. 17,648, filed Mar. 3, 1970, entitled Metal Drawing Die," now abandoned which was a continuation in part of US. Pat. application Ser. No. 686,064, filed Nov. 28, 1967, entitled Metal Drawing Die, now abandoned.
This invention relates to a novel design for a die such as might be used on a drawbench to reduce the crosssectional dimensions or area and to improve the surface finish of extruded or otherwise pre-formed blanks or billets of materials such as steel and alloys of aluminum, titanium and beryllium, the superalloys and the refractory metals. The invention is more particularly related to a draw die to be employed in the dimensional and surface finishing of blanks such as metallic extrusions characterized by complex cross-sectional configurations such as Ts, H's, Zs, ls, and so forth.
Such blanks or extrusions have been popularly employed in the art as structural members and this has been particularly so in the case of the construction of aircraft and aerospace vehicles and equipment where weight is almost always a critical factor because of the fact that the complex cross-sectional configurations contribute to the greatest structural strength per unit of weight. To gain the maximum structural efficiency, it is essential to obtain desired surface finishes and tolerances which are critical factors in aircraft and aerospace vehicles from the standpoint of the elimination of stress risers of such surfaces, and to reduce excess weight in a particular construction or design. It has been the practice to subject the blanks which have been formed by extrusion, rolling, or the like, to one or more machining operation. Thus, for example, smooth surfaces are required to eliminate notch sensitivity and possible fatigue failure. The maximum allowed variation in thickness of the webs, flanges, or extensions of the complex cross-section for aircraft or aerospace vehicle construction is on the order of i'0s002 inch throughout a foot'length and thesurface finish is required to be IOO RMS or better. To me'etthese specifications it has been necessary to subject complex shaped blanks to a series of very costly and timeconsuming machining operations. The more complex the cross-sectional shape of the component, the more costly and timeconsumingare the required surfacefinis'hing operations. Although the very precise finishes and tolerances required in the aerospace industry are an outstandingexampleof the problem, in most if :not allof theconstruction and assembly industries itis frequently not possible to employ an extrusion or other stringeras'it comes from the press orrolling mill-and expensive machining andother finishing operations are required.
=ln an effort to eliminate some or all'of these finishing operations, the prior art has resorted in a limited way to theuse of drawing dies ondrawbenchesnhe desired effect'of which is to achieve a uniform reduction'in the cross-sectionaldimensions and area ofthe part andto impart a smoother surface to it. Thisis achieved'bythe forced pulling or drawing ofthe'length'of the matepart ispulled through the die,the effect of the dieface isto cause a'flowofthe excess metalina directionopposite tothe movement of thepartthrough'the die with the displaced volume of metal being reflected in an increased length of the drawn or finished part.
The success of this apparently desirable and sufficient means for obtaining desired dimensional and surface characteristic control of a preformed component has been substantially impaired by the fact that it is economically impractical if not impossible for the extruding and rolling mills to produce the blanks in the first instance which have a reasonable uniformity in the cross-sectional dimensions or the surface characteristics of the part which ultimately is to be passed through the draw die. Since this is particularly so with regard to members of complex cross-sectional configurations, the problems encountered in the drawing operation as a result of the nonuniformities in the part being drawn are even greater in the case of the more complex shapes; and the result of this has been that, even though such shapes are in all other respects more desirable, particularly in the aircraft and aerospace industries, their use has been substantially hindered by economic considerations which necessarily arise where the intricate and time-consuming machine operations remain as the only known satisfactory means for finishing such parts.
It is the nonuniformity of the starting materials which cause the failure of the part being drawn, deterioration of the drawing die and/or breakdown of the lubricant that is conventionally employed in either cold or warm drawing operations. It has been discovered that, as a workpiece is pulled through the conventional drawing dies of the prior art, the excess metal resulting from the nominal reduction in cross-sectional area accumulates at the face of the die in a nonuniform manner which results in the presence of nonuniform stresses across the working edges of the die. As this metal continues to pile up, the greater reduction in the cross-sectional area of the part at such point further increasesthe stress in the metal, in many instances to the point at which the stress exceeds the ultimate strength of the metal being worked and the part breaks or separates while it is being drawn. in other cases, even though the ultimate strengthof the metal being worked is not exceeded, the
continuous application, particularly in a noncontrollable, nonuniform fashionresults in excessive stress concentrations at certainzpoints on the die at which the lubricant breaks down and severe galling of both the part and the die occur to render both unusable.'Beyond this,
regardless of whether or not the excessive stresses result in the breakage of the part or in the deterioration of its surface orof'the die, in almost all cases the nonuniformbuildup of the metal in front of the drawing face of the die results in a bending of the part as it emerges from the die. Tests have demonstrated that some 20 process for finishing such parts must accommodate those with unequal volumes of metal in their various segments and such accommodation results in the unequalapplication of the drawing force throughout the cross-section of thepart, satisfactory products are not likely-to be achieved. Indeed it might be said that the correction of the above-enumerated problems with prior art apparatuses and processes will have'to violate "basicprinciples of geometry and mechanics.
It is accordingly an object of the present invention to provide an improved metal drawing die. A more specific object of the invention is to provide such a die which is capable of accomplishing substantial reductions in the cross-sectional dimensions of metal components, especially those of complex cross-sectional configurations having angularly disposed legs, webs, and/or flanges which are not at the outset of uniform dimension or surface characteristics.
Another object of the invention is to provide such a die which is capable of accomplishing the dimensional changes in a continuous and uniform manner and of simultaneously improving the surface characteristics of the drawn part thereby eliminating the need for machining or any other finishing operations thereon.
Still another object of the invention is to provide such a die which can accomplish the above objects without being subject to premature deterioration in themselves or will not lead to premature damage or deterioration of the part being drawn or the lubricants employed in connection therewith.
The most significant object, of course, is to provide a new and unique draw die capable of accepting nonuniform blanks and of reducing them to parts of satisfactory and usable quality without complicated finishing operations.
INVENTION To achieve these and other objects and advantages of the invention which will appear from a reading of the following disclosure, the present invention teaches a die which is capable of eliminating the excessive building up ofthe metal in front of the die face. More specifically the present invention teaches a die which, by simple variations in its basic design, can be so constructed that the excess metal resulting from the reduction in the cross-sectional area of the part being drawn will be caused to move laterally as well as longitudinally of the direction of the movement of the part through the die. At the same time, the lateral dimensions of the die opening are, according to the teachings of this invention, enlarged to accommodate the lateral movement of the metal in such a manner that it will continue to pass through the die without any excessive metal buildup in front of it. Although the length of the legs or projections will vary somewhat as the metal is laterally displaced within the die opening, the lengths of such legs or projections may be easily corrected and made uniform by a relatively simple edge machining or broaching operation which involves neither the cost nor the time of the type of complete surface machining that has heretofore been required.
To accomplish the beneficial lateral movement of the metal, the present invention teaches a drawing die wherein the forward or working surfaces of the die opening, i.e., those surfaces adjacent the die opening which are first contacted by the metal blank moving through the die, are divergent or sloped rearwardly or in the direction of the movement of the piece through the die. In certain modifications of the invention, this divergence of the working surfaces may be accomplished by simply sloping the forward face of the die which the die opening intersects to form the working surfaces.
In other modifications, the working surfaces of the die at which the metal is actually reduced in lateral dimensions are recessed or positioned interiorly of the die; and communication of the metal blank with such edges is provided by suitable passages through the die forwardly of the edges. These particular modifications are especially adaptable for use where, as in the case of the reduction of a T-section, for example, substantial working forces are present at certain points of the die. The provision of additional die body at such points, as opposed to their mere location upon the surface of the die, serves to reinforce the die and to accommodate the larger stresses without subjecting the die to premature breakage or to variations in the opening which would result in dimensional variations in the finished part.
The angular disposition of the working surfaces of the die is such or, by calculation or experiment is adjusted to be such, relative to the particular size, shape, and composition of the blank being drawn, that the flow of the metal laterally of the direction of travel of the blank through the die will cause a predetermined amount of the excess metal tending to build up in front of the die to move to the edges of the part. Considered from a slightly different point of view, it can be observed that in the prior art constructions wherein the working surfaces of the die have been substantially at right angles to the movement of the part, all of the metal being moved or caused to flow in the drawing reduction is translated into the elongation of the part. Since all of this displacement occurs forwardly of the die, there has heretofore been no apparent means whereby the displaced metal could be shifted laterally from one location on the part which is oversize to some other location thereon which is undersize. In the case of the present invention where the working surfaces are angularly disposed, a portion of the displaced metal, depending upon the degree of the angular disposition, will, because of its lateral movement, result in an increase in the lateral dimensions of the drawn part. Since this degree of lateral displacement is substantially directly proportional to the angle of inclination of the working surfaces; i.e., that angle which they form with a plane at right angles to the direction of the movement of the part, an inclination angle of say 18 may result in the lateral movement or flow of approximately 20 percent of the metal being displaced to increase the lateral dimensions. On the other hand, approximately eighty percent of the displaced metal would still be caused to flow longitudinally to result in an increase in the length of the part. While the specific result as to any part will depend as well upon the physical characteristics such as the hardness, ductility, malleability, coefficient of friction, plasticity, etc., of the material of which the part is formed and of the lubricants and other process parameters, the preferred angle as to any particular part composed of any particular material can be quickly arrived at by nominal empirical adjustments. As previously indicated, the preferred disposition of the working surfaces should be such that the lateral flow of the metal can absorb, adjust for, or otherwise accommodate such nonuniformities as existed in the original blank prior to drawing. On the other hand, since, as will be hereinafter more fully explained, the lateral metal flow results in a growth in lateral dimension, the nonuniformities of which will be ultimately corrected by edge trimming or broac'hing operations, it is also preferred that the lateral metal flow be no greater than is absolutely necessary to cover all nonuniformities that are reasonable to be anticipated. Hence the angle of inclination of the working surfaces should be no greater than is necessary.
An important feature of the die of the present invention is that, to accommodate such lateral growth of the part as is necessary, the die surfaces which form the lateral extremities of the reduced part extend beyond the anticipated length of the particular legs or flanges to provide an extended opening or clearance that will accommodate the laterally displaced metal and allow it to move freely through the die without any interference. Because this lateral flow will vary according to minor variations in the drawing forces applied and the uniformity of the composition of the metal being worked upon, the precise degree of the lateral flow and the growth of the extremeties of the legs or flanges cannot be controlled. Consequently, it is in many cases necessary, after the part has been thus drawn, to machine or otherwise to trim the edgemost portions of the flanges or webs to their desired dimensions. In such cases,'even though a machining operation is thus required, it can be appreciated that this is a very basic and inexpensive machine shop operation which is entirely distinguishable from the machining that would be required to bring the entire cross section into proper tolerances insofar as size and surface characteristics are concerned.
If the material application is such that only the edges of the finished .part are to be machined, in particular cross sections such as channels or U's, Hs, Fs, and l's wherein certain of the webs or flanges are interior and do not terminate in exposed edges, the die opening forming such interior webs or flanges in such cases need not be angularly disposed relative to the movement of the part. Only those surfaces of the die which are to form those legs or flanges which do terminate in exposed edges will have angularly disposed working surfacesand the working surfaces ofthe portions of the die to form the interior webs may be at right angles to the direction of the drawing movement of the part or have a zero angle of inclination. Thus, in the case of a die to reduce a length of a channel having a U-shaped cross section for example, the base web of the channel from each edgeof whichprojects a flange is formed by working surfaces which are disposed at right angles to the movement of the part through the die whereas those flanges which do project upwardly from the base are formed by working surfaces which are rearwardly sloped from thefront die face or have an angle of'inclination. As a result of thisparticular disposition of the various working surfaces, all of the lateral displacement of the metal is reflected at the upper edges of extremitiesof each of the flanges projecting from the base, and it is only these edges which ultimately have to be trimmed where closer tolerances than those whichresult from a natural displacement of the metal are required.
However, if the interior webs or flanges are to be substantially reduced in section, it is possible to induce lateral flow in the interior section by the angular deposition of the working surfaces in the direction of drawing thereby inducing lateral metal flow toward an intermediary part of the section where a local relief in the die allows unrestrained-metal flow. Therefore, in the case of a die to reduce a length of channel having a U- shaped cross section, for example, the baseweb of the channel from each edge of which projects a flange is formed by working surfaces which are disposed at a rearward angle fromthe juncture of the base web and the vertical flanges to induce lateral metal flow toward an intermediary position of the base web (preferably the center) where a relief in the die allows unrestrained metal flow. The fins that project upwardly from the base may be formed by working surfaces which are rearwardly sloped from the front of the die face at some angle of inclination. As a result of this disposition of the various working surfaces, all lateral metal flow is directed toward a portion of the die where local metal flow is unrestrained and it is only these locations which ultimately have to be machined where closer tolerances are required.
Another embodiment of the subject invention allowing unrestrained metal flow in interior webs or crossbars would have lateral metal flow induced by the angular disposition of the die working faces with no local relief in the die at anintermediaryposition. The workpiece itself would have a continuous depression or relief at the intermediary position where lateral metal flow induced into this intermediary position would flow unrestrained into the relief provided in the workpiece itself.
The invention thus generally described may be more clearly understood by reference to the following detailed description of certain specific andvpreferred embodiments and examples thereof in connection with which reference may be made to the appended drawings wherein:
FIG. I is a front elevational view of a drawing die constructed in accordance with the present invention and designed to accommodate a T-shapedpart;
FIG. 1A is a fragmented cross-sectional view of the orifice of the die of FIG. 1 as seen along the line lA-lA thereof;
FIG. 2 is a perspective view of the die illustrated in FIG. 3 is a perspective view of the die illustrated in FIGS. 1 and 2 with a workpiece being drawn therethrough;
FIG. 4 is a front elevational view of a drawing die according to the present invention adapted for the drawing reduction and finishing of a U-shaped part with no lateral flow induced by the dies in the interior web of FIG. 9 is a graph showing dimensional changes experienced by utilizing the dies of the present invention and conventional dies in drawing T sections;
FIG. 10 is a front view of the draw die used to reduce and finish a U-shaped part where the die surfaces induce lateral metal flow in the interior section as well as the upright fins;
FIG. 11 is a perspective view of the die illustrated in FIG. 10;
FIG. 12 is a perspective view of the drawing die illustrated in FIGS. 10 and 11 with a U-shaped workpiece being drawn therethrough.
Referring now to the FIGS. 1, 1A, 2, and 3, a typical drawing die 10 according to the present invention is shown to consist of a cylindrical main body portion 11 and a face portion 12 formed with a die orifice 13 which, in the case of the illustrated embodiment, is T- shaped in cross section having a base (13a and 13b) and an upwardly projecting stem 13c. As is best illustrated in FIGS. 2 and 3, the face 12 of die 10 protrudes being, in this particular instance, of a generally conical configuration having its apex at 14. The intersection of the base and stem of the T-shaped orifice 13 coincides with the apex 14 of the protruding die face 12 so that each leg 13a and 13b of the base and the stem 13c slants rearwardly or in the direction of movement of workpiece 16. The metal working surfaces 15 of legs 13a and 13b of the base and the stem 13c parallel the leg and stem openings.
As shown by FIG. 3, a T-shaped metal extrusion 16 may be drawn through the T-shaped orifice 13 of die 10 in the direction of the arrow. As is the practice in the case of conventional drawing dies, the width of the individual passages defined by the respective working surfaces 15 of the die openings is nominally less than the width or thickness of the flanges 17 and 18 of the workpiece 16 to be drawn by the die. It is, of course, in response to this reduced dimension that the workpiece is drawn as it passes through the die to the ultimately desired dimensions which are those established by the spacing between said working surfaces. As previously stated, however, in the case of the present invention, the influence of the divergent character of the die working surfaces is such that the displacement of all of the metal involved in the reduction in the crosssectional dimensions of the part is no longer translated exclusively along the axis of the movement of the part through the die but is rather in part at least translated into some lateral movement and lateral expansion of the part as it passes through and emerges from the die. To accommodate this lateral flow of metal and the lateral metal expansion, legs 13a and 13b and stem 13c of die orifice 13 extend laterally from the intersection 14 farther than normally regarded to be necessary solely to accommodate the lateral expansion of the various webs such as 17 and 18 of the part.
Thus, it will be observed that the lateral limiting surfaces 19, 20, and 21 of the die opening are spaced from the edges of the workpiece passing therethrough to provide ample clearance. The distance between the edge of the workpiece and the surfaces 19, 20, and 21 of the die opening at these points should be sufficient to accommodate whatever lateral flow of metal results as the particular part of a particular composition is drawn through a particular die having a particular angle of divergence of its working surfaces.
Although some nominal contact between the transversely expanding edges of the workpiece and the lateral limiting surfaces 19, 20, and 21 of the die opening was thought permissible even to the extent that a nominal amount of metal might build up in front of the die even at the surfaces 19, 20, and 21, it is most important that this build-up might be such that it exerts no substantial pressure upon the part or resistance to the movement thereof through the die. However, it has been determined that such nominal contact is impractical and not possible in ordinary commercial practice. Consequently, it may be stated that to avoid metal build-up in back of the die lateral flow of fins or webs 17 and 18 must be completely uninhibited. In other words, lateral limiting surfaces 19, 20, and 21 must not contact the workpiece or distortion and warping of the workpiece will result.
As previously explained, as the part 16 enters the die under the influence of a drawing force applied by conventional clamping means (not shown) and moves through the die in the direction of the arrow, the restrictive influence of the relatively smaller die opening causes a flow of the metal of the part which results in the parts being reduced in its cross-sectional dimensions, at least insofar as the width of the webs and flanges such as 17 and 18 are concerned. The metal that is necessarily displaced in this reduction in volume per unit length of the part as it passes through and emerges from the rear of the die is moved by the die face or more particularly the working surfaces of the die opening in a direction generally opposed to the direction of the movement of the part. Whereas in the prior art dies, this movement was almost entirely longitudinal in the direction of such movement, the angular disposition of the working surfaces of the die of this invention is such that a controllable portion, depending upon the degree of the angular disposition, of the displaced metal will flow laterally to the direction of movement of the part and tend to fill the clearance spaces between the workpiece and limiting surfaces 19, 20, and 21.
While in some cases, the relative uniformity of the dimensions of the part before it is drawn will be such that the degree of lateral flow of the metal (as influenced by the angular disposition of the working edges, the characteristics of the metal itself, etc., as set forth above) may be controlled so that the lateral expansion of the part only nominally exceeds the distance provided by the enlarged spacing of the limiting surfaces 19, 20, and 21 so that the part emerging from the die will be in the exact cross-sectional dimensions desired, not only with regard to the width of the flanges but also as to their length. In most cases, however, and particularly in those where the die of the present invention is to find its greatest utility and advantage, the nonuniformities in the original workpiece will be such that the lateral growth of the part (wherein the bulk of the nonuniformities are absorbed or accounted for) will be too erratic or variable to have the legs 13a and 13b and stem 13c completely filled to limiting surfaces 19, 20, and 21 without one or more oflegs 13a and 13b or stem 13c being excessively filled to the point that an excessive build-up of metal occurs during at least one part of the drawing operation to create the problems that have heretofore been experienced in conventional draw dies. Consequently, the limiting surfaces 19, 20, and 21 should always be spaced a somwhat greater distance from intersection 14 than the ultimately predicted lengths of the webs of the finished part. In these cases it is then necessary to finish the part after it has passed through the draw die by a machining operation to bring the webs or flanges to their desired length; but it is again to be pointed out that this edge trimming or broaching operation is a fast and economical operation that does not represent a substantial distraction from the great benefits achieved by the use of the die.
The draw die 22 illustrated in FIGS. 4, 5, and 6, like that above described, is shown to comprise the body portion 23 and the rearwardly divergent or conical working face 24. In this particular modification the die orifice is designed for the drawing of a U-shaped channel member. Orifice 25 is provided with a base 26 and side legs 27 and 28 which extend upwardly from either side of base 26. The front die face 24 is frustroconically shaped, terminating at its forwardmost end in a flat surface 29. The effect of this particular configuration of the front die face is that the U-shaped passage through the die intersects the front face in such a manner that the working surfaces which parallel the base 26 and which ultimately draw the cross web 31 of workpiece 30 (FIG. 6) extend transversely to the direction of movement of the part 30 through the die, whereas the working surfaces which parallel legs 27 and 28 are angularly disposed to the plane normal to the movement of the part and slope rearwardly therefrom to provide for lateral flow or the metal of which the webs 32 and 33 are composed as the part is drawn through the die.
The lateral distance between flanges 32 and 33 of the workpiece 30 must remain fixed so that outward lateral metal flow in web 31 is not desirable since there is no unrestrained edge to allow lateral expansion. In this particular application the method of the invention is not used on the center portion 31 of the workpiece 30. However, the metal tending to build up in front of the die at the legs 27 and 28 of orifice 25 may be relieved by lateral flow. Thus, as the part 30 is drawn through the die in the direction of the arrow, the base or trough web 31 will be reduced in thickness and receive the desired surface characteristics although no lateral metal flow takes place. At the. same time, however, flanges 32 and 33 will expand laterally (vertically in the case of the position of the part as shown in the drawings). To accommodate this lateral flow, space is provided between the limiting surfaces 34 and 35 of legs 27 and 28 in which the expansion of the side flanges may occur without an incidence of excessive build-up of the metal that might cause breakage of the part, damage to the die or other disrupting influences in the drawing operation.
In passing, reference is made to FIG. 5 wherein the face 29, being normal to the direction of the movement of the part through the die can be used as a reference plane for the definition of the angle of inclination 37 which is the angle of intersection between the rearwardly sloped working surfaces of the die opening such as those paralleling legs 27 and 28 with the surface 29 which is merely representative of a plane normal to the movement of the part.
Referring now to FIGS. 7 and 8, the die 37 is shown to be basically cylindrical in its overall shape having a flat front face 38 parallel to the flat rear face 39 both of which are intersected by a drawing passage 40 designed to receive a member of T-shaped cross-section with the transverse or base opening 41 and the stem opening 42 extending vertically therefrom. In this case, however, it is important to observe that the working edges of the die do not parallel the base and stem openings, but are rather positioned interiorly of the die at 44. These working surfaces may be likened to the working surfaces that parallel base legs 13a and 13b and stem 13c of the die of FIG. 1 and are identified as base legs 44a and 44b and stem leg 44c. As will be ob served, these working surfaces are angularly disposed to the plane normal to the movement of the part through the die; and, because of their angular disposition and because they are the working surfaces which actually result in the drawing or reduction of the part, they have the same influence upon the lateral movement of metal and lateral expansion of the part as do the similarly disposed working surfaces of the dies previously illustrated and described.
Thus, the entrance portion of die orifice 40 is of greater dimensions that the undrawn T-shaped workpiece and the opening diminishes in size from opening 40 to work surfaces 44 and then expands to opening 50. A gage reduction of the base and stem fins of the workpiece does not occur until the lateral dimensions along any given transverse plane reaches the working surfaces 44. Upon reaching the surfaces 44 the drawing phenomenon is substantially identical with what occurs at the working surfaces that parallel the face 12 of the die of FIG. 1. Since the base surfaces 44a and 44b and stem 44c are all inclined at an angle in the direction of drawing from a centrally positioned apex 45, metal flow will tend to be lateral and if the limiting surfaces 46, 47, and 48 of legs 44a and 44b and stem 440 are spaced a sufficient distance from apex 45 to permit adequate lateral flow, such flow will occur to prevent metal build-up and alleviate the problems associated therewith. The exit orifice 50 may be larger than work surfaces 44 though smaller than opening 40.
In FIG. 8, a T-shaped extrusion 16' (side elevation) is shown as being drawn through die 37 in the direction of the arrow. In this embodiment web 18 corresponds to web 18 of the embodiment of FIG. 3. Limiting surface 48 corresponds to limiting surface 20 of the embodiment of FIG. 3 and accordingly is spaced from the end of web 18' so that lateral flow of web 18' will not bring the web into actual contact therewith. Web 17 corresponding to web 17 of FIG. 3 is likewise spaced from limiting surface 47 (FIG. 7) of the orifice of die 37 so as to avoid inhibition of lateral growth of web 17 during the redrawing.
The drawing die in FIGS. 10, 1 1, and 12 comprise the body portion 63 of a die that induces lateral metal flow in all components of a complex workpiece having an interior web 71 with no unrestrained edges as well as flanges 72 and 73 that can expand unrestrained at their extremities. This die has two conical work faces 69 and 64 with the die orifice 65 designed for the drawing of U-shaped channel members provided with a central relief 63 of the die restraint to allow local metal flow induced by the disposed die face 69. Orifice 65 is provided with a base 66 and side legs 67 and 68 which extend upwardly from either side of base 66. The rearwardly diverging front die face 64 is frusto-conical shaped terminating at its forward end on the intersection of the rearwardly convergent front die face 69. The effect of this particular configuration of the front die face is that the U-shaped passage through the die intersects the front faces in such a manner that the working surfaces which parallel the base 66 and which ultimately draw the cross web 71 of workpiece (FIG. 12) are angularly disposed rearwardly in the direction of drawing the part 70 through the die just as the working surfaces which parallel legs 67 and 68 are angularly disposed to the plane normal to the movement of the part and slope rearwardly therefrom to provide for lateral flow or displacement of the metal in the entire part 70 as it is drawn through the die.
The lateral distance between flanges 72 and 73 of the workpiece 70 must remain fixed so that lateral metal flow must be directed toward the center where the relief 63 provided in the die orifice 76 allows local unrestrained metal flow and expansion. The working face 69 is a rearwardly converging conical surface whose working surfaces 66 induce lateral metal flow toward the center of the web 71 of workpiece 70 into relief 63 in an unrestrained manner. At the same time flanges 72 and 73 will expand laterally (vertically in the case of the position of the part shown in FIG. 12). To accommodate this lateral flow, space is provided between the limiting surfaces 74 and 75 of legs 67 and 68 in which the expansion of the side flanges may occur without an incidence of excessive buildup of the metal.
The intersection of faces 69 and 64 define a plane normal to the direction of the movement of the workpiece through the die and the intersection can be used as a reference plane for the definition of the angle of inclination 77 of the two rearwardly sloping working faces 69 and 64.
It will be appreciated that the term working surfaces as used in the above descriptions relate to that portion of the die orifice surface that contacts the metal surface of the workpiece as it is drawn through the die and is the area of pressure wherein metal flow is caused to occur to effect a dimensional reduction of the workpiece. Such working surfaces are not necessarily flat as represented by working surfaces 44 of the die of FIG. 7, but more likely include a portion of the flared die opening (see FIG. 1A).
It will be further understood that the drawings are not dimensionally accurate since such accuracy is an engineering detail well within the skill of the art. The exact shape ofa die opening such as that depicted by FIG. 1A may vary widely depending on variables such as the metal of the workpiece, the complexity of its construction, etc.
It will be noted that in many instances complex structural members may be drawn through the dies of the present invention in a manner to provide lateral metal flow for every metal component. This is possible where every component is fin shaped and extends (cross sectionally) laterally from the workpiece. Examples of such members are Ts, L's, V5, and X-shaped members. Although the dies and method of the present invention are particularly advantageous for drawing such members as set forth above, it is obvious that the present invention is equally applicable to the drawing of any elongated member having at least one extending fin that makes it possible to reduce metal buildup on at least a portion of the member. Such members include: I, U, Z, H, and many of the complex shapes now used by the air frame industry. Where it is desirable to reduce the complete member including the internal components ofls, Us, and Zs, and Hs utilizing lateral flow the method of inducing metal flow toward a local die relief makes it possible to reduce metal buildup in the entire member.
The angle at which the working surfaces of the die of the present invention are inclined is not critical in that any angle will have some beneficial effect in causing lateral flow during drawing. However, angles of 85 and less (from the drawing direction) are preferred and angles of less than are impractical.
The method of the present invention has been demonstrated by drawing T sections through straightening dies constructed in conformity with the above teachings.
In one series of tests, aluminum alloy (AA 7075) extruded T sections were dra wn thrOug h a die constructed in conformity with the present invention and for comparision similar sections were drawn through conventionally shaped dies having comparable dimensions.
The die constructed in conformity with the present invention was of the type shown by FIGS. 7 and 8. The included angle of the working face for this die was (45 from the drawing direction), the approach angle (on either side) was 6, and the land width was 0.188 inches. Shims were provided for reductions as low as 5 percent per pass, covering a range of section thickness of from 0.097 inches to 0.040 inches. The width and height dimensions far exceeded the width and height of any of the extruded sections.
The dimensions of the extruded T sections both before and after drawing are set forth in Tables I to ill below. These dimensions include width (designated W; see FIG. 3), height (designated H), and gage or thickness (T). The gage measurements were taken in three positions identified by T1, T2, and T3 in FIG. 3.
Tables I-Ill The data of Tables H" was utilized in preparing the graph of FIG. 9. In the graph curve 60 represents plots of the dimensional changes (increases) of the T-shaped sections drawn through conventional dies while curve 61 represents comparative dimensional changes of similar T sections drawn through the die of FIG. 7. Curves 62 and 63 represent height and width changes of the conventional draw versus drawing with a die in accordance with the present invention respectively. Curves 64 and 65 represent gage or thickness reductions in the conventional draw as compared to the use of the present invention respectively.
It is readily discernable from the data of Tables I-lll and the graph of FIG. 9 that the included workface angle (90) is effective in producing marked growth of height and width dimensions. The conventional die reduced these dimensions by about 1 percent but the workface angled die increased these dimensions by about 3 percent at small (2.7 to 5.2 percent) thickness reductions and by about 11.7 percent at large (14.3v
The ratio of width to length increase will be depen-' dent upon the workface angle.
The increase in draw force required for a given reduction with the workface angled die is expected since the draw force is largely converted to sidewise thrust.
TABLET Before After Before After Before After Before After Before After T1 T1 T2 T2 T3 T3 II l[ W W 063 055 065 058 063 047 063 053 065 056 063 052 063 057 065 056 063 040 063 056 065 056 063 047 063 053 066 056 063 052 063 057 065 050 003 074 063 056 065 055 003 047 063 .054 .065 055 .063 .048 .063 .055 065 056 063 .040 .088 -.000 -.000 Percent change -12. 7 l3. 8 04 TABLE II T shape No. 2 die, new design (plow effect) force, 2,250 average, 2,300 maximum Before After Before After Before After B efore After Before After T1 T1 T2 T2 T3 T3 11 H W W Distance along length:
TABLE III T shape No. 3 die, normal straight land force, 2,300 average, 2,400 maximum B efore After Before After Before After B efore After Before After T1 T1 T2 T2 T3 T3 H H W W Distance along length:
1" .063 .053 065 054 063 055 747 740 .955 951 2" 063 053 .065 054 063 .055 .747 .741 to .950 3 063 .053 .065 .054 063 .054 .747 741 .060 .050 4". .063 053 .065 .054 063 054 .747 .741 .952 5" .063 053 .065 054 063 .053 .747 741 .951 6. .063 .053 .065 .054 063 .054 747 .742 .052 7" 063 053 .065 054 063 .054 .747 742 .050 8". .063 052 065 053 063 .054 747 .744 051 Average. .063 .053 065 054 063 .054 .747 .7415 .058 .051 Change -.010 .011 .000 0055 -.007 Percent change 15.0 16.-9 14.3 .74 .73
In addition to the above enumerated tests, aluminum (7075) Ts (commercial and 10l36-2002) were succcssfully drawn from an average thickness of 0.097 inches to 0.040 inches using the convex face draw die of FIG. 7 with a 90 from the draw direction) included angle working surface. There was substantial metal movement transverse to the direction of drawing. There was little distortion after drawing, showing that the lateral metal flow avoided the adverse effects of thickness viariations in the extrusion.
The extrusions were drawn to 0.040 inch thickness in increments of 5 percent reductions. It was necessary to anneal after every third draw in thicknesses between 0.068 inch and 0.052 inch and after every draw in thicknesses between 0.052. inch and 0.040 inch to avoid point breakage (the points were chem milled for threading through the dies). Actual dimension changes are shown by Table IV below:
1. A drawing die comprising: a. a die body formed within an orifice having working surfaces that define a cross-sectional configuration disposed to reduce cross-sectional dimensions of a pre-formed part drawn therethrough, said configuration including at least one extending fin;
b. at least a portion of said working surfaces being inclined in the direction of movement of said part so as to urge lateral flow in a direction away from said direction of movement, for at least a portion of said pre-formed part during drawing, the inclined working surfaces including those disposed to reduce the thickness of said fin; and
c. a portion of said working surfaces defining said fin extending laterally from the axis of said die a greater distance than the corresponding fin of said pre-formed part so as to provide space for uninhibited lateral metal flow during drawing.
2. A drawing die is set forth by claim 1 wherein the inclined working surfaces of the die are substantially parallel with die face, said face protruding to provide the angle of the inclination.
3. The die of claim 1 wherein said working surfaces defining said fin extend laterally from the axis of the die a greater distance than said metal will flow laterally.
4. The die of claim 1 wherein said working surfaces defining said fin is inclined at an angle from the drawing direction of from 5 to 85 degrees.
5. The die of claim 1 wherein said cross-sectional configuration is selected from the group consisting of Ts, H's, Z's, Is, Xs, Ls, V5, and Us.
6. A drawing die as set forth in claim 1 wherein the inclined working surfaces are substantially centrally positioned within said die body and the entrance and exit passageways taper inwardly and outwardly respectively.
7. A method for reducing the cross-sectional dimensions of an elongated structural member formed with at least one extending fin comprising:
a. positioning opposing working surfaces about said member disposed to reduce said dimensions as said member is drawn therebetween;
b. providing an inclination of said opposing working surfaces positioned to reduce the thickness of said fin in the direction of drawing so as to urge lateral metal flow in said fin in a direction away from said direction of drawing;
c. providing space at the extremities of said working surfaces positioned to reduce the thickness of said fin with said space disposed to accommodate the induced lateral metal flow; and
d. drawing said member through said working surfaces.
8. The method of claim 7 wherein said working surfaces positioned to reduce the thickness of said fin are inclined from the axis of said member in the direction of draw from 5 to degrees.
9. The method of claim 7 wherein said members have cross-sectional configurations selected from the group consisting of TS, Hs, Zs, ls, X's, and Us 10. A method for reducing the cross-sectional dimensions of an elongated structural member formed with at least one element where lateral metal flow is inhibited by configuration due to the lack of an unrestrained edge comprising:
a. positioning opposing working surfaces about said member disposed to reduce said dimensions as said member is drawn therebetween;
b. providing an inclination of said opposing working surfaces to reduce the thickness of said element in the direction of drawing so as to induce lateral metal flow in said element toward an intermediary position in said element;
c. providing local relief of restraint at the intermediary position in said element allowing unrestrained metal flow into the space provided; and
d. drawing said member through said working surfaces.
11. The method of claim 10 wherein said working surfaces positioned to reduce the thickness of said element induce lateral metal flow to a local relief where space is provided for unrestrained metal flow.
12. The method of claim 10 wherein said working surfaces positioned to reduce the thickness of said element are inclined from the axis of said member in the direction of the draw from 5 to 85 degrees.
13. The method of claim 10 wherein said members have cross-sectional configurations selected from the group consisting of Hs, Zs, I's, and Us.