US 3599471 A
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United States Patent 1,591,572 7/1926 Stimson 76/107 R 1,826,873 10/1931 Hess 76/107 R 2,332,360 10/1943 Wakefield 76/107 R 2,691,905 10/1954 Onksen 76/107 R 3,137,937 6/1964 Cowan .1 29/486 3,409,975 11/1968 Rolsten 29/4701 3,503,110 3/1970 Berry 29/1574 Primary ExaminerCharles W. Lanham Assistant Examiner-Gene P. Crosby Attorneys-John R. Faulkner and Donald J. Harrington ABSTRACT: An incremental die construction comprising individual rod increments that are premachined and arranged in registry, one end of each rod forming an increment of a precalibrated surface contour, and a metal cap bonded to the ends of the rods over which sheet metal may be drawn during metal-forming operations.
T I I I I I I I 1 I l I I I 1 I I I Y J L l PATENTEU Ausl-mn 3,59%471 SHEET @1 5 EXPLOSIVE CAlPlPllNG FOR HEX DIES GENERAL DESCRIPTION OF THE INVENTION My invention is an improvement in the invention disclosed in copending application Ser. No. 749,685 filed Aug. 2, 1968, which is assigned to the assignee of my invention. This copending application discloses an incremental die comprising hexagonal rods which are precut to length using a numerically controlled cutoff machine. The ends of each rod form a segment of a predetermined surface contour so that the individual rods may be bonded together to form a solid die section.
The upper die section and the lower die section can be formed simultaneously since the numerically controlled rodcutting steps produce registering elements of the upper and lower die sections, the matching ends of the two rods forming increments of the rough machined die surface equivalent for the respective die sections.
By employing my invention a homogenous die surface for a hexagonal rod assembly can be made and the rods themselves may be tied together to form a unitary die section that is structurally rigid.
A die section such as that described in the copending application may be provided with a capping of metal which may be finish machined to provide a homogenous, continuous Contact surface for the sheet metal material to be drawn by the die. This is done by an explosive capping procedure which will be described. The metal capping applied to the die rod material produces a permanent bond that ties the rods together into a welded assembly.
DIe surfaces of wear resistant materials can be used in my invention while retaining the base metal for structural rigidity. For example, it is possible by employing the teachings of my invention to convert prototype dies of hexagonal rod construction to production dies. This is done by the addition of long wearing metal caps which may be finish machined to form the finished die surface.
The rods of the die section need not be brazed together. It is possible, for example, to use instead a low-temperature epoxy adhesion process rather than a high-temperature brazing process. This avoids distortion of the die surface.
PARTICULAR DESCRIPTION OF THE FIGURES OF THE DRAWING FIG. 1 shows in plan view an incremental die section without the cap applied thereto.
FIG. 2 is a cross-sectional view taken along the plane of section line 22 ofFlG. 1.
FIG. 3 is a cross-sectional view taken along the plane ofsection line 3-3 ofFlG. 1.
FIG. 4 is a die comprising incremental sections, one section being shown in registry with the other. The capping for the upper die section is illustrated in FIG. 4.
FIG. 5 is a view of the rod ends of the upper die section of FIG. 4 as seen from the plane of section line 5-5 of FIG. 4.
FIG. 6 is a cross sectional view taken along the plane of section line 6-6 of FIG. 5.
FIG. 7 shows an incremental die section together with a metal cap, as it would appear prior to the explosive capping operation.
PARTICULAR DESCRIPTION OF THE INVENTION FIGS. 1,2 and 3 show one ofa pair of die sections for forming sheet metal. In this instance the die section has a cooperating die surface in the form of a cavity. The cooperating die section would have a convex die surface that would register with the concavity of the die section shown in these figures.
Numeral I0 designates in FIGS. 1, 2 and 3 a die housing which may be in the form ofa box. The housing may be of any shape desired, although in the FIG. 2 embodiment it is a square. Situated in the housing in close registry are hexagonal rods 12. Each rod is cut to form an upper surface such as that shown at 114, which generally cooperates with an adjacent end surface of the adjacent hexagonal rod. The surfaces directly adjacent surface 17 are designated by reference characters 16, I8, 20 and 22 in FIG. 3. The height of each rod, as well as the angularity of the end surface, are chosen so that each individual surface forms an increment of a larger surface having a contour that approximates the contour of the desired finished dies surface.
In the embodiment of FIGS. 1, 2 and 3 the row of hexagonal rods directly adjacent the vertical walls of the housing It) defines a pilot ridge 24 which extends around the periphery of the die section. Each individual rod is formed with a segment of a ridge 24 so that when the individual rod segments are joined side by side, they define the peripheral ridge 24!. This ridge registers with a peripheral groove in the registering die section so that the dies sections are piloted one with respect to the other into periphery registry. When the die sections are brought together into registry, each incremental end surface of each rod 112 registers with a cooperating end surface of a companion rod for the other die section. The angle of the surface for any given rod 12 and the die section of FIG. 3, for example, would have an identical angle on the cooperating end surface of the companion rod of the other die section. A clearance space between these two end surfaces accommodates the metal thickness of the sheet metal formed by the dies.
In FIG. 4 is shown in cross section a pair of die sections, each having a die surface that registers with the die surface of a companion section. The space between the companion end surfaces of the upper and lower rod segments of the upper die section 27 and the lower die section 29 is occupied by the sheet metal 25. Shown also in FIG. 4 is a metal cap 40 which envelops the end of the rods of the die section 27. This metal cap 40 is finish machined by a machining process employing a numerically control, multiple axis milling machine.
Prior to the finish machining operation, each end of each hexagonal rod forms an end surface that is tangent to the die surface contour at a point that falls on the center line of the rod itself, as illustrated in FIG. 6. The individual rods 12 include surfaces 26, 28 and 30 which form rough machined surface equivalents for the die surface contour shown at 32. Points of'tangency for the surfaces 26, 28 and 30 coincide with the points of intersection of the center lines 34, 36 and 38 for the rods I2 with the finish die surface 32.
The capping 40 for the die section is machined to form a contour which is parallel to the contour 32. It is not necessary to remove large quantities of metal during the machining operation. No rough machining is required. The machining operation can be made by a suitable multiple axis milling machine controlled by a numerical control director. This is described in copending application Ser. No. 577,997, now Pat. No. 3,548, I 73 filed Sept. 8, 1966, which is assigned to the assignee of this invention. Reference may be had to that application for the purpose of supplemenung this disclosure.
Before applying the explosive capping, the hexxgnnal assembly for the die section is held together by a suitable adhesive. The adhesive is cured until it is set. The surface defined by the ends of the rods then is rough ground to provide a uniform surface that is not necessarily accurate. This surface can be cleaned by abrasive blasting. A preformed and cleaned blank of metal material, approximately oiiequarter to threeeighths inch thick, is fixed in place on the rough ground and cleaned end surfaces of the die section. If desired, this metal blank can be located either by tack welding or by some other suitable retaining means. A layer of sheet explosive then is attached to the top of the preformed metal blank and a suitable primer cord is attached along one end. This arrangement is illustrated in FIG. 7, where the explosive is shown by reference character 42 and the primer cord is shown at 44. A detonator, which is wired to an electrical voltage battery ignites the primer cord and the explosive charge is detonated as the burning progresses across the surface of the cap. The characteristics of the explosive during the bonding of the metal cap to the ends of the rods is similar to the action described in U.S. Pat. No. 3,137,937 in which an explosive'bonding procedure is described. Reference may be had to that patent also for the purpose of supplementing this disclosure.
A homogenous bonding zone is established between the capping and the ends of the rods.
The velocity that the burning edge develops during the burning operation must be proper for the particular metal that is used. The choice of metal, of course, is determined by the physical characteristics of the dies that are desired. The capping establishes a work surface for the die, and it also secures together the hexagonal rods in a rigid assembly which eliminates the need for brazing or welding of the rods that form the die sections.
Having thus described the preferred form of my invention, what I claim and desire to secure by U.S. Letters Patent is:
1. A machined die section comprising a plurality of incremental rods with a cross section in the form of a regular polygon, said rods being situated in registry and bonded together to define an integrated assembly, corresponding ends of said rods forming discrete two dimensional surfaces, said rod ends being contiguous to form a predetermined surface definition, and an explosive capping formed on said end surfaces whereby said rods are held together in a rigid assembly,
said explosive capping forming a surface layer for said die section which may be finish machined to a predetermined surface contour.
2. A combination as set forth in claim 1 wherein said rods in cross section form a regular hexagon whereby said rods may be welded together to form an integral assembly. 1
3. A pair of die sections, each section comprising a plurality of incremental rods with across section in the form of a regular polygon, said rods being situated in registry, corresponding ends of said rods forming discrete two dimensional surfaces, the end surface of one assembly being contiguous to define a predetermined die surface contour, the end surface of the rods of the complementary assembly being contiguous to define another predetermined surface contour, and concave portions of one surface contour registering with convex portions of the other surface contour, at least one of said die sections having an explosive capping formed thereon, said capping overlying the rod ends of said one die section and forming a bond therewith, said capping providing metal that may be finish machined to a predetermined surface contour of which the contiguous end surfaces of said rods form an approximation, said capping holding together said rods in an integral rigid assembly.