US3559450A - Incremental die construction having a hole piercing capability - Google Patents

Abstract

A DIE CONSTRUCTION FOR FORMING SHEET METAL, THE PUNCH SECTION AND THE COMPLEMENTARY DIE SECTION BEING FORMED OF INTEGRATED HEXAGONAL RODS, THE RODS OF THE RESPECTIVE DIE SECTIONS BEING IN ALIGNED REGISTRY, THE ENDS OF THE RODS BEING FORMED WITH SURFACES HAVING PRECALIBRATED SURFACE NORMALS, SELECTED RODS BEING ADAPTED TO ACCOMMODATE A

DIE PUNCH AND A DIE BUTTON IN THE COMPLEMENTARY METAL FORMING DIE SECTIONS.

Description

Feb 2, 1971 F. E. WHITACRE; Y 3,559,450

INCREMENTAL DIE CONSTRUCTION HAVING A HOLE PIERCING CAPABILITY Filed sept. 9. 196e I 5 sheets-sheet 1 y Nf INVENTO Feb. 2, 1971 F. E. WHITACRE 3,559,450

INCREMENTAL DIE CONST TION HAVING HOLE PIERCING ABILITY 'Filed sept. 9, 196e 5 sheets-sheet a INVENTOIIL' ff/'f/z/iffmf Fell 2, 1971 F. E. WHITACRE 3,559,450

INCREMENTAL DIE CONSTRUCTION HAVING A HOLE PIERCING CAPABILITY Filed Sept. 9, 1968 l 5 Sheets-Sheet S f mi A MII/171i iff/NM1 Nw L @ /YLA 'Xi/@5 El' V M y Iggy @Uf f E; 4` i @Emy- INVENTOR.'

J Cdf @S/2g Feb. 2,1971

Filed sept; 9, 1958 F'. E. WHITACRE INCREMENTAL DIE CONSTRUCTION HAVING A`HOLE PIERCING CAPABILITY 5 Sheets-Sheet E ELAB.

vue-J INVENTOR:

United States Patent O 3,559,450 INCREMENTAL DIE CONSTRUCTION HAVING v A HOLE PIERCING CAPABILITY Foster'E. Whitacre, Farmington, Mich., assgnor to Ford Motor Company, Dearborn, Mich., a corporation of Delaware Filed Sept. 9, 1968, Ser. No. 758,360 Int. Cl. BZld 37/00 U.S. Cl. 72-464 4 Claims ABSTRACT F THE DISCLOSURE A die construction for forming sheet metal, the punch section and the complementary die section being formed of integrated hexagonal rods, the rods of the respectivedie sections being in aligned registry, the ends of the rods being formed With surfaces having precalibrated surface normals, selected rods being adapted to accommodate a diepunch and a die button in the complementary metal forming die sections.

GENERAL DESCRIPTION OF THE INVENTION My invention is adapted especially, but not exclusively, for use with an incremental, metal-forming die of the type described in co-pending application Ser. No. 749,685, filed Aug. 8, 1968. That disclosure is assigned to the assignee of my instant invention, and reference may be made to it for the purpose of supplementing this disclosure.

The complementary die halves for the metal forming dies described in the co-pending application may be formed from hexagonal metal rods. The rods are precut to length so that the end surfaces of the individual rods are situated in contiguous relationship to define an approximation of the finished die surface. The rods are identied by numbers or the like, and the side of each rod facing in a given direction is identified to permit automated assembly of the cut rods.

After the hexagonal rods are assembled in registry, they are brazed together to form a permanent bond, thereby forming an integral die section. After bonding, the die sections are finished machined to the required surface contour. The cutting of each of the individual rods at the required angle defines an increment of the rough die surface. Each rod of the bottom die section faces a matching rod for the upper die section.

If the finished sheet metal part is to be formed with pierced holes, such as bolt holes, one or more of the rods of one die section may be moved so that its end protrudes above the surface of the adjacent contour defined by the companion rods of that die section. The complementary rod for the other die section can be removed, either Wholly or partially, so that when the die sections are brought into registry, the raised rod will enter the recess created upon withdrawal of the other rod. The raised rod thus can form a die punch, and the rods in the other die secltion surrounding the recess form a die button. In the alternative the removed rod can be replaced by a hardened steel die button, preferably of hexagonal shape, and the raised rod can be removed and replaced by a hardened steel die punch situated in exact alignment with the opening in the die button.

If sequential or compound action of the die is necessary, a movabledie punch, whether it is in the form of a rod or a hardened steel die punch, can-be carried by a movable die head or platen that is adapted to move independently of the die half with which it cooperates. In this way the metal forming can be completed prior to the initiation of the piercing operation.

The hole piercing capability of the die sections can be integrated into the manufacturing technique for the die ice itself through the use of numerically controlled process steps. The coordinate dimensions that locate the aligned rods involved in the hole punching operation can be'made a part of the input data which is initially used for controlling the cutting and the assembly of the rod elements.

In making the die halves the shape of the hole produced by deleting one of the rods can be made to match the shape of the complementary rod of the other die half, the length of the latter being controlled numerically during the cutting operation for the rods. If it is desired to insert a hardened steel die punch, the punch itself can be made in a hexagonal shape so that it exactly registers with the hexagonal shape defined `by the adjacent rods of the die section. The same is true for the die button that would register with the hardened steel die punch.

BRIEF DESCRIPTION OF THE FIGURES OF THE DRAWINGS FIG. l is a cross-sectional view of complementary die sections with a formed sheet metal part located between the sections.

FIG. 2 shows a metal forming die made form integrated hexagonal rods.

FIG. 3, shows a metal forming punch which is adapted to register with the die of FIG. 2. It also is formed from integrated hexagonal rods. FIGS. 2 and 3 are isometric assembly views of a die section constructed as illustrated in FIG. 1.

FIG. 3A is an enlarged view taken along the plane of section line 3A-3A of FIG. 3.

FIGS. 4A, 4B and 4C show the process steps used in 4forming an incremental die used for constructing a rough machined casting equivalent.

PARTICULAR DESCRIPTION OF THE INVENTION 'of the rods being situated in mutual registry. The rods are bonded together by brazing or by some other suitable bonding technique.

Each rod is cut to a predetermined length and at a predetermined angle so that the end surface of each rod forms an increment of the rough form of the die surface. After the rods are assembled, the incremental surfaces which are contiguous with respect to each other form a surface profile indicated generally by reference character 12.

The die portion for the pair of die sections is shown in FIG. 2. This registers with the punch portion of FIG. 3 as seen in FIG. 2. The die portion is formed of hexagonal rods 14 which, like the rods 10` shown in FIG. 3, are of hexagonal shape. The rods 14 are cut to predetermined length, and the end surfaces are formed by cutting the rods at a predetermined angle with the angular position of the rods with respect to their axes being preset so that the ends of the rods form an increment of the rough form of the die surface.

lEach of the rods 14 is situated in co-axial alignment and in perfect registry with a companion rod 10. Each rod 10 and its companion rod 14 are formed in the same cutting operation from a common piece of bar stock, the length of which is predetermined.

When the die portion of the pair of die sections registers with the punch portion shown in FIG. 3, a predetermined clearance exists between their respective die surfaces. This is shown in FIG. 1. The space between the surfaces is occupied by the sheet metal 16, which is formed as the punch portion and the`die portion are brought into registry.

`In FIG. 1 construction, the rods 14 that form the die insert are assembled in a die housing 18. The housing includes end walls 20 and 22 and a base 24. The rods 10 of the punch insert are assembled in another housing 26 having end walls 28 and 30. The rods in a selected region of the punch insert are foreshortened to accommodate a platen 32, which is adapted to move vertically within internal recess 34 formed by the foreshortened rods 10.

If it is desired to form in the sheet metal 16 a pierced opening for a bolt or for some other purpose, one of the rods can be removed. It can be replaced by a die punch rod 36, preferably of hexagonal shape, which registers `with the hexagonal opening formed by the removed rod. The punch rod 36 can be tied to the platen 32 and moved vertically therewith.

In a similar fashion rods 14 may be removed from the die insert to form a cavity for receiving a die sleeve or button 38 having a hexagonal central opening 40. If seven adjacent rods are removed from the die insert, the center of the seven rods has a hexagonal opening that exactly registers Iwith the punch rod 36. The insert 38 that is substituted for the removed rods then would have a corresponding hexagonal opening for receiving the punch rod 36.

When the dies are brought into registry, the metal is deformed as illustrated in FIG. l. Following this operation, the platen 32 can be moved downwardly so that the punch rod 36 enters the opening 40. The lower region of the opening 40 can be formed with an enlarged diameter thereby providing a clearance space 42 which will permit the slug removed from the sheet metal 16 to fall freely through an aperture 44 formed in the base 24 of the housing 18.

Movement of the platen 32 occurs after the punch insert has been received in the die insert. This prevents tearing of the metal, which Iwould otherwise occur if the punch rod 36 were to protrude from the die surface of the punch insert as the latter dcforms the sheet metal 16.

The housings 26 and y18 can be formed with cooperating pilot ridges and recesses as indicated at 46. This establishes exact registry of the elements 10 with their companion elements 14 as the sheet metal 16 is formed. The platen 32 can be operated hydraulically with a sequential motion in timed relationship with respect to the motion of the punch insert. Prior to removal of the punch insert, the platen 32 can be withdrawn from the die button 38.

There have been some circumstances, especially when the rods themselves are formed of an alloy steel vwith a high hardness number, when selected rods in the die insert may form the die button without the necessity for providing a special insert such as that shown in FIG. 1 at 38. This requires removal of a single rod rather than several rods, although the surfaces of the rods that surround the hexagonal opening caused by the removal of one of the rods 14 must be formed with a fiat in order to provide for the clearance 42.

During the formation of the assemblies shown in FIG. 1, the numerically controlled program is furnished with sufficient input data to permit the application of stop-off material on the rods that must be removed to form the punch rod and die button openings. Input data can be provided to the system also to permit machining of the flats of the rods that will produce a clearance 42 and which ywill permit special maclzu'ning of the foreshortened rods to provide a cavity within which the platen 32 operates. The automated operating procedure for forming the die sections with the special hole piercing capability is illustrated in FIGS. 4A, 4B and 4C.

FIGS. 4 A, 4B and 4C show a process `fiow chart which is separated into thirteen stations. Each station is separated into substations. As station I, substation 1, the hexagonal bar stock is loaded into each of the several openings of the material turret. If the particular die design requires special materials in selected regions, this requirement can be introduced into the automatic control program whereby the materials in the turret can be intermixed. Rods having various degrees of hardness to provide added wear quality in special areas in the finished die surface then can be selected. For example, if a selected area of the die surface is to operate as a hole punch die button, the rods that define the hole punch opening must be of substantially harder hardness number than that normally required by the other rods of the die surface.

In substation 2 of station I, the material turret, on command from the control system, rotates so as to present the proper material to a cutoff machine. The first machining operation occurs at substation 3, which requires the raw bar stock to be squared off by removing a minimum amount of stock from the rod end. This is accomplished by feeding the bar against a tailstock as indicated.

In substations 4, 5 and 6 of station I a cutoff blade, whose linear position is fixed, is automatically actuated to square-cut the end of the bar. While the cutoff plate is cutting the bar, the tailstock support, in response to numercial data, is set to a discrete linear position in the X- axis direction. The positive stop is retracted, and the bar is fed automatically into the tailstock. At substation 7 the cutoff plate is again actuated to cut through the bar. The cut bar now becomes the so-called in-process hex rod whose length at this time represents the adjusted, completed length.

The bar then is transferred to station II. After being clamped into position against an end stop, the bar is cut by two milling cutters simultaneously to produce a at at each end of the bar. One milling cutter is preset with respect to the end stop. The second cutter is adjustable in the X-axis direction, thereby accommodating varying lengths of the bars.

The machined flats provide a convenient area for impressing on the rods an identification number. This is done in station III of substation 1 as the bar is positioned against an end stop and clamped. One marking head can be fixed, and the other is adjustable in an X-axis direction. They are actuated in response to computer program data by supplying an identification number in binary code form at each end of the bar. The numbers are consecutive from end to end and progressive from bar to bar.

As the numbering heads are retracted, two opposed hollow milling cutters are actuated to approach and chamfer each end of the bar. The bar then is transferred to station IV.

During transfer to station IV, the bar is rotated by a collet chuck. At the same time end pressure is applied to the bar in the direction of the collet chuck in such a manner that the modified hexagonal configuration of the bar enters a modified collet opening. When the two shapes coincide, the collet chuck head then is rotated about its A-axis to the proper angular increment in relation to the numbered data.

After the bar is angularly positioned, it is clamped.v

A face mill is adjustable in the X-axis position in response to numerical data and is automatically actuated to machine a flat across one of six preselected corners. After the rods are assembled, these corners provide a passage through the die to permit venting of air or passage of lubricant.

Any rods that do not require this special machining are not transferred to station IV. Instead they are transferred directly to station V. At this stage another collet chuck angularly orients the rods about the A-axis. The rod is adjusted then in substation 2 in an X-axis direction in response to numerical data. A cutoff blade, which is preset in substation 3, is passed through the rod in substation 4 at a predetermined angle. This angular cut produces two rods, one of which represents a component of the punch portion of the die section and the other of which represents a component of the companion die portion. A space is generated by the cut and the rod ends define complementary portions of the desired surface.

Wire brushing and degreasing of the rods occur in stations VI and VII, and grit blasting occurs in station VIII. Each of these operations is done for the purpose of preparing the rods for copper spraying in station IX. Those rods that require bonding are sprayed with copper in station IX. Those rods that are to be withdrawn from the assembly are sprayed with stop-off material that inhibits brazing.

Those rods that are to be removed in the manner described previously are replaced by a hole-punch or die button. For example, in the FIG. 1 embodiment, the rod that occupies the space for the punch rod 36 would be sprayed with stop-olf material thereby permitting its withdrawal. The same is true for the rods that occupy the space for the die button 38. Those special rods within the boundaries of the opening are identified in the original numerical program and subsequently pinpointed in response to numerical data for stop-off application in the automated system.

In stations X and XI, in-process rods are automatically oriented to position so that the impressed face on the rod is presented to a reading head. The reading head will identify the piece at this station. Odd numbered pieces will be channeled in one direction, and even numbered pieces will be channeled in another direction. The odd numbered rod pieces will form a component of the punch half of the die section, and the even numbered rod pieces will form the complementary die half, or vice versa.

At stations XII and XIII where the operations are automate-d, the odd numbered pieces are arranged in numerical order as are the even numbered pieces. The separate groups then are assembled into fixtures. This is followed by a brazing operation to provide a permanent bond between the assembled rods.

The die section then can be finished machined to form the die surface indicated, for example, in FIG. l.

Having thus described a preferred embodiment of my invention, what I desire and claim to secure by United States Letters Patent is:

y1. A sheet metal forming die with an arbitrary surface curvature and having a hole piercing capability comprising a plurality of rods having a geometric cross section that permits their assembly into close registry, each rod being machined with a predetermined length with the end surface thereof being situated in a plane having a surface normal in a discrete, predetermined direction, the end surfaces of said rods forming incremental areas of a die surface contour for a rough machined casting equivalent, a companion die section formed with corresponding rods with machined end surfaces forming increments of a matching surface contour for a rough machined casting equivalent, the end surfaces of the rods of one die section being complementary in precise registry with the end surfaces of the rods of the other die section, the ends of the rods of each die section being contiguous to form a complete, contoured surface, aligned openings formed in said die sections, said openings being created upon removal of selected rods, and a die punch rod in the opening of one die section and removable relative to the rods of said one die section to permit piercing of the formed metal as the die sections are brought into registry.

2. The combination as set forth in claim 1 wherein the aligned opening formed in said other die section accommodates a die button with a central opening adapted to receive said die punch rod, the cross sectional shape of the die button corresponding to the cross sectional shape of the opening in said other die section as said selected rods are removed.

3. A method for making a metal forming die having a hole piercing capability comprising the steps of selecting hexagonal bar stock, cutting said bar stock to a predetermined length, cutting the cut bar stock into two pieces to produce two end surfaces on the cut pieces which define incremental areas having surface normals with discrete, predetermined directions, assembling said cut pieces into two separate die section assemblies, one piece forming an increment for one die section and the companion piece forming a complementary increment of the other die section, the incremental areas formed by the cut bar stock forming increments of a contoured surface of continuous, arbitrary shape for a rough machined casting equivalent, removing selected stock pieces from said assemblies to provide aligned openings in said sections, and inserting a punch rod in one of said aligned openings to permit the formed metal to be pierced following the metal-forming operation of said die section.

4. The combination as set forth in claim 3 including the step of substituting a die button in the aligned openings in the other die section, the die button having a central opening that receives said punch rod, the cross sectional areas of said punch rod and of said die button corresponding to the cross sectional shape of the respective openings formed upon removal of said selected rods.

References Cited UNITED STATES PATENTS 1,336,388 4/ 1920 Youngberg 72-475 1,861,648 6/1932 Vehko -n 72-359 2,332,360 10/1943 Wakefield 76-107 3,277,535 10/1966 Rupert 18-44 LOWELL A. LARSON, Primary Examiner U.S. C1. X.R. 712-475, -107

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