SEGMENTED DIES FOR USE WITH ULTRASONICS

Abstract

A forming die that includes a body, wherein the body of the forming die includes at least one opening created therein; at least one die segment, wherein the at least one die segment is adapted to be inserted into the at least one opening in the body of the forming die, and wherein the at least one die segment is further adapted to receive ultrasonic vibrations; and at least one geometric feature formed within the at least one die segment, wherein the at least one geometric feature affects the ultrasonic vibrations in a predetermined manner.

Claims

1. A forming die, comprising: (a) a body, wherein the body of the forming die comprises: a cavity circumscribed by the body and at least one opening in the body; (b) at least one die segment, wherein the at least one die segment is adapted to be inserted into the at least one opening in the body of the forming die and be adjacent to the cavity, and wherein the at least one die segment is further adapted to receive ultrasonic vibrations; and (c) optionally, at least one geometric feature formed within the at least one die segment, wherein the at least one geometric feature affects the ultrasonic vibrations in a predetermined manner.

2. The forming die of claim 1, further comprising at least one source of ultrasonic vibrations in communication with the die segment for directing ultrasonic vibrations into the die segment.

3. The forming die of claim 2, wherein the at least one source of ultrasonic vibrations is either embedded within the die segment or external to the die segment.

4. The forming die of claim 1, further comprising at least one vibration-isolating device positioned between each die segment and the body of the forming die, wherein the at least one vibration isolating device prevents ultrasonic vibrations from the die segment from entering the body of the forming die.

5. The forming die of claim 4, wherein the at least one vibration-isolating device is a low friction pad.

6. The forming die of claim 1, further comprising a die segment adapting fixture, wherein the adapting fixture is mounted within the body of the forming die, wherein the die segment is mounted within the adapting fixture, and wherein the at least one vibration isolating device is mounted between the die segment and the adapting fixture.

7. The forming die of claim 1, wherein the at least one geometric feature includes a cylindrical bore, and wherein the cylindrical bore is oriented transversely, side-to-side, within the die segment.

8. The forming die of claim 1, wherein the at least one geometric feature includes a cylindrical bore, wherein the cylindrical bore is oriented vertically within the die segment.

9. The forming die of claim 1, wherein the at least one geometric feature includes a square cutout, and wherein the square cutout is oriented vertically within the die segment.

10. The forming die of claim 1, wherein the at least one geometric feature includes a rectangular cutout, and wherein the rectangular cutout is oriented transversely, side-to-side, within the die segment at a predetermined angle.

11. The forming die of claim 1, wherein the at least one die segment has a length, a height, and a width, and wherein the at least one geometric feature formed within the die segment permits the width of the die segment to be increased from an acoustic quarter-wavelength to a predetermined multiple thereof.

12. A forming die, comprising: (a) a body, wherein the body of the forming die comprises: a cavity circumscribed by the body and at least one opening in the body; (b) at least one die segment, wherein the at least one die segment is adapted to be inserted into the at least one opening in the body of the forming die and be adjacent to the cavity, and wherein the at least one die segment is further adapted to receive ultrasonic vibrations; (c) at least one source of ultrasonic vibrations in communication with the at least one die segment for directing ultrasonic vibrations into the at least one die segment, wherein the at least one source of ultrasonic vibrations is either embedded within the at least one die segment or external to the at least one die segment; and (d) optionally, at least one geometric feature formed within the at least one die segment, wherein the at least one geometric feature affects the ultrasonic vibrations in a predetermined manner.

13. The forming die of claim 12, further comprising at least one vibration-isolating device positioned between the die segment and the body of the forming die, wherein the at least one vibration isolating device prevents ultrasonic vibrations from the die segment from entering the body of the forming die, and wherein the at least one vibration-isolating device is a low friction pad.

14. The forming die of claim 12, further comprising a die segment adapting fixture, wherein the adapting fixture is mounted within the body of the forming die, wherein the die segment is mounted within the adapting fixture, and wherein the at least one vibration isolating device is mounted between the die segment and the adapting fixture.

15. The forming die of claim 12, wherein the at least one geometric feature includes a cylindrical bore, and wherein the cylindrical bore is oriented either transversely, side-to-side, within the die segment or vertically within the die segment.

16. The forming die of claim 12, wherein the at least one geometric feature includes a square cutout, and wherein the square cutout is oriented vertically within the die segment.

17. The forming die of claim 12, wherein the at least one geometric feature includes a rectangular cutout, and wherein the rectangular cutout is oriented transversely, side-to-side, within the die segment at a predetermined angle.

18. The forming die of claim 12, wherein the at least one die segment has a length, a height, and a width, and wherein the at least one geometric feature formed within the die segment permits the width of the die segment to be increased from an acoustic quarter-wavelength to a predetermined multiple thereof.

19. A forming die for use in automotive applications, comprising: (a) a body, wherein the body of the forming die comprises: a cavity circumscribed by the body and at least one opening in the body; (b) at least one die segment, wherein the at least one die segment is adapted to be inserted into the at least one opening in the body of the forming die and be adjacent to the cavity, and wherein the at least one die segment is further adapted to receive ultrasonic vibrations; and (c) optionally, at least one geometric feature formed within the at least one die segment, (i) wherein the at least one geometric feature affects the ultrasonic vibrations in a predetermined manner, and (ii) wherein the at least one geometric feature includes a cylindrical bore that is oriented transversely, side-to-side, within the at least one die segment; a cylindrical bore that is oriented vertically within the at least one die segment; a square cutout that is oriented vertically within the at least one die segment; a rectangular cutout that is oriented transversely, side-to-side, within the at least one die segment at a predetermined angle; or combinations thereof.

20. The forming die of claim 19, wherein the at least one die segment has a length, a height, and a width, and wherein the at least one geometric feature formed within the die segment permits the width of the die segment to be increased from an acoustic quarter-wavelength to a predetermined multiple thereof.

Description

DESCRIPTION OF THE DRAWINGS

[0010] The accompanying drawings, which are incorporated into and form a part of the specification, schematically illustrate one or more exemplary embodiments of the invention and, together with the general description given above and detailed description given below, serve to explain the principles of the invention, and wherein:

[0011] FIG. 1 is a perspective view of a forming die in accordance with an exemplary embodiment of the present invention showing the ultrasonically excited die segment removed from the body of the forming die;

[0012] FIG. 2 is a perspective view of the forming die of FIG. 1, wherein the ultrasonically-excited die segment has been fully mounted and secured within the body of the forming die;

[0013] FIG. 3 is a perspective view of a forming die in accordance with an exemplary embodiment of the present invention showing the ultrasonically-excited die segment removed from the body of the forming die and also showing the adapting fixture mounted within the body of the forming die;

[0014] FIG. 4 illustrates the general three dimensional vibrations that occur in the ultrasonically-excited die segment of this invention as well as the length, width and depth dimensions;

[0015] FIG. 5 illustrates the general directions of ultrasonic vibrations across the surface of the ultrasonically-excited die segment that are preferred for achieving maximum friction reduction effects;

[0016] FIG. 6 is a perspective view of an embodiment of the present invention, wherein ultrasonically-excited die segment includes a plurality of slots formed therein; and

[0017] FIG. 7 is a perspective view of an embodiment of the present invention, wherein the ultrasonically-excited die segment includes a plurality of cylindrical columns or holes formed therein.

[0018] FIG. 8 is a perspective view of a forming die in accordance with another exemplary embodiment of the present invention showing the placement of two ultrasonically-excited die segments within the body of the forming die;

[0019] FIG. 9 is a perspective view of one of the ultrasonically-excited die segments of FIG. 8 shown without any internal features that affect the vibration amplitude of the segment;

[0020] FIG. 10 is a perspective view of one of the ultrasonically-excited die segments of FIG. 8, wherein the ultrasonically-excited die segment includes transverse cylindrical bores having different diameters formed therein;

[0021] FIG. 11 is a perspective view of one of the ultrasonically-excited die segments of FIG. 8, wherein the ultrasonically-excited die segment includes a plurality of vertical bores formed therein;

[0022] FIG. 12 is a perspective view of one of the ultrasonically-excited die segments of FIG. 8, wherein the ultrasonically-excited die segment includes at least one vertical square cutout formed therein;

[0023] FIG. 13 is a perspective view of one of the ultrasonically-excited die segments of FIG. 8, wherein the ultrasonically-excited die segment includes a transverse cylindrical bore formed therein; and

[0024] FIG. 14 is a perspective view of an embodiment of the present invention, wherein at least one of the ultrasonically-excited die segments of FIG. 8 includes a plurality of transverse, angled, rectangular cutouts formed therein.

DESCRIPTION OF THE INVENTION

[0025] Exemplary embodiments of the present invention are now described with reference to the Figures. Although the following detailed description contains many specifics for purposes of illustration, a person of ordinary skill in the art will appreciate that many variations and alterations to the following details are within the scope of the invention. Accordingly, the following embodiments of the invention are set forth without any loss of generality to, and without imposing limitations upon, the claimed invention.

[0026] The purpose of the present invention is to apply ultrasonic vibrations to one or more regions of a large stamping die in order to reduce friction between the sheet metal being formed and the surface of the die, thereby improving the formability of the metal at critical shape locations, as well as reducing galling, tearing and cracking of the sheet metal. This desired effect is accomplished by acoustically isolating a segment (or segments) of the die and embedding within the die, an ultrasonic vibration source (i.e., an ultrasonic transducer) that creates resonant vibrations of the die, of varying magnitudes, at its several surfaces thereby creating an ultrasonic friction reduction effect having various benefits. Thus, the present invention typically includes the steps of: (i) identifying a critical region (or regions) of a die where friction reduction would have greatest effect (or effects); (ii) acoustically isolating a segment (or segments) of the die, from the critical region (or regions) into a manageable mass (or masses) that is capable of being ultrasonically excited; and (iii) incorporating within that mass a source of ultrasonic excitation, i.e., an ultrasonic transducer system. The ultrasonic excitation of the die segment by an internal source versus transmitting vibrations from an external source to the die segment along with the specific means of its acoustic isolation, are among the novel features of the invention.

[0027] With reference now to the Figures, a first exemplary embodiment of an acoustically isolated ultrasonic die is shown in FIGS. 1-2. In FIG. 1, die assembly 10 includes die segment 12, which is adapted to be excited with ultrasonic/acoustic vibrations; a portion of a large stamping die 14; and low friction pads 26 (or similar devices) that are operative to provide acoustic isolation die segment 12 when ultrasonic vibrations are applied thereto. In FIG. 1, die segment 12 is shown separated from large stamping die 14, wherein in FIG. 2, die segment 12 is seated within a portion of large stamping die 14. As shown in FIG. 1, acoustic isolation of die segment 12 involves an adaption of portion of large stamping die 14 to specifically accommodate die segment 12. In addition to the opening created in portion of large stamping die 14 for die segment 12, low friction isolation pads 16 may be affixed to portion of large stamping die 14, and/or set screws or other threaded components may be utilized to secure die segment 12 within portion of large stamping die 14. Various means for ultrasonically exciting die segment 12, such an external ultrasonic transmission line or an embedded internal excitation mechanism (i.e., transducer), may be used (not shown in the Figures). For use in the present invention, the piezoceramics in an ultrasonic transducer are typically pre-compressed to prevent tensile fracture.

[0028] With regard to holding ultrasonic die segment 12 within a portion of large stamping die 14, it is important to acoustically isolate the ultrasonic die segment from the surrounding die structure, while at the same time securing it in a fixed location so that it seamlessly merges into the overall die. Two approaches, which may be used alone or in combination with one another include: (i) low friction pads 16, wherein the pads include a Frelon coating or are made from a metallic bearing material such as bronze or cast iron; and (ii) a setscrew engagement. The surrounding die structure should be capable of some disassembly in order to insert ultrasonic die segment 12 as well as to provide access for the electrical (and possibly air) connections to the die segment insert. Low friction pads 26 may be screw-in inserts, and while these inserts may be sufficient to secure die segment 12, a set screw method may also be modified for this purpose.

[0029] One important aspect of the present invention generally, is the minimal modification a large die for accommodating a die segment that will be excited with ultrasonic energy. While adjustment or modification of a large die for accommodating the general block dimensions of die segment 12 is possible (because current die practice allows for die segments) it may not always be practical to modify a large die to accommodate the various features of a particular die segment. Accordingly, in some embodiments, die segment adapting fixture 18 is included for more effectively placing die segment 12 into at least one portion of large stamping die 14. FIG. 3 provides a generalized image of this embodiment. Die segment adapting fixture includes features that hold, position, and acoustically isolate die segment 12 from the remainder of the large stamping die. Die segment adapting fixture 18 is not typically acoustically active and is not intended to vibrate at ultrasonic frequencies. Die segment adapting fixture 18 is configured to be easily attached to large stamping die 14, usually in a recess, opening, or aperture created for receiving the fixture. Die segment adapting fixture 18 may be attached to a large die in the same manner as die segment 12.

[0030] The present invention has been described herein in reference to forming dies. A typical stamping/forming operation consists of the forming die, a blank holder and a punch, each of which may have large mass and dimensions (as noted earlier for a die). This invention, i.e., an ultrasonically activated, embedded die insert, may be applied to blank holders or punches, as well. By means of this invention it is possible to create ultrasonic vibrations in a critical segment or segments of a large die that would otherwise be impossible to ultrasonically excite to any significant vibration level, and in so doing, to reduce friction forces between sheet metal being formed and the forming die at one or more critical forming locations on the die.

[0031] With regard to the size and dimensions of die segment 12, FIG. 4 illustrates the general three dimensional vibrations that occur in such dies as well as the length, width and depth dimensions (L, W and D). Also shown in FIG. 4 are the two ultrasonically active die faces that contact deforming metal in a manufacturing process, with the other faces being embedded within the large stamping die 14 or within die segment adapting fixture 18. Determining the practical size of an ultrasonic die segment 12 that provides the desired ultrasonic vibrations for friction alleviation in the forming process is also an aspect of this invention. For ultrasonic sheet metal forming, the ultrasonic vibrations on the surface of die segment 12 will preferably be in the general directions shown in FIG. 5, for achieving maximum friction reduction effects. Thus, the surface of the die typically includes vibration components that are both perpendicular to the surface and parallel to the surface in the general direction of the deforming metal sliding along its surface. This result is achieved by restricting the length L of the die segment to approximately an acoustic half wavelength (about 5 inches for a steel die at 20 kHz) in its longitudinal dimension and the width and depth of the die segment to approximately one quarter of an acoustic wavelength (about 2.5 inches for a steel die at 20 kHz) or less in its lateral dimension, while its vibrational motion is restricted to purely longitudinal at its ends and purely lateral in its middle region. If dimensions significantly exceed these limits, additional complex vibration modes may enter, and the surface of the die can take on a complex vibration pattern that may negatively affect friction reduction. However, large stamping dies may have regions requiring ultrasonic friction reduction that significantly exceed these acoustically imposed limits, especially those in the width direction.

[0032] Accordingly, one aspect of the present invention includes creating controlled vibrations on a die surface by embedding, within the body of the die and/or in non-contacting die surfaces, various geometric features that modify surface vibrations and facilitate the friction reduction performance of the die. As will be appreciated by one of ordinary skill in the art, it is known to incorporate slot features in ultrasonic plastic welding horns for achieving uniform vibration across a welding surface, which is essential for creating a uniform weld. While slotting of this nature demonstrates that geometric features can be used to affect surface vibrations occurring on certain ultrasonic tooling, such slots are not necessarily compatible with ultrasonic metal forming dies because a smooth forming surface against the formed metal is required. To overcome this limitation, certain embodiments of this invention include various geometric features that are embedded within the body of die segment 12 and/or at the die surfaces that are not in contact with formed metal. These geometric features are effective for creating a desired or predicable ultrasonic vibration pattern at the forming surfaces of the die.

[0033] In the embodiment shown in FIG. 6, slots placed internally within die segment 12 permit increasing the die width W well beyond the acoustic quarter-wave limit that would normally apply. As shown in FIG. 6, internal rectangular or square slots 20 are machined into die segment 12 from the back of bottom and are not surface breaking at the die forming surfaces. FIG. 7 depicts an embodiment that includes internal cylindrical holes 22 rather than slots 20. The precise geometric shape and positioning of such internal features will be subject to the general size and shape of the overall die segment, which will be dictated by the specific forming process being used. The use of computer analysis (e.g. finite element analysis (FEA)) permits specific details of the internal features to be determined by analytical means, which then guides final die design and fabrication. Using this approach, it is possible to increase the dimensions of ultrasonic segmented dies to the sizes needed for most if not all practical forming processes. Using this method of increasing the overall width of die segment 12, multiples of the acoustic quarter-wavelength can be achieved such as, for example, up to an acoustic half-wavelength or acoustic full wavelength (e.g., 2.5 inches for a steel die at 20 kHz up to 10 inches in width).

[0034] As described above, an important feature of the present invention is that certain predetermined segments of a large die used in ultrasonic sheet metal forming, used for the automotive, aerospace, and consumer products industries, for example, can be acoustically isolated from the balance of a massive die structure, thereby permitting ultrasonic vibrations to be concentrated in small, critical forming regions of the die, such as corners and sidewalls (see FIG. 8). This feature of the present invention allows maximum application and effect of the ultrasonic vibrations used in the forming process, without vibrational energy being transmitted (and ultimately lost) to adjacent regions of the die mass. The segmented die shown in FIG. 8 includes certain performance enhancements, including force reductions and reduced spring back. However, the performance of the segmented die may be further improved by: (i) increasing the overall size and total mass of the die (as described above), thereby permitting its use in large die systems (see FIGS. 6-7); and (ii) modifying the distribution of vibration amplitude of the die surface to improve friction reduction characteristics by altering the die surface at critical locations. The dimensions of die segments such as those shown in FIG. 8 are typically about 5 inches in length, 2 inches in width and 2 inches in height. As discussed above, these are the approximate acoustic limiting dimensions of a solid die vibrating in its first longitudinal mode. Furthermore, the axial vibration is at a maximum at the ends of the die segment, while the transverse vibrations are a maximum in the middle of the die segment. While these vibrations have proven beneficial, greater benefits are realized if the overall size of the die segment is increased and the vibration pattern is altered/modified.

[0035] With reference to FIGS. 9-14, certain embodiments of this invention provide structural features that further enhance the performance of the segmented dies described herein beyond die force reduction and reduction in springback. These embodiments provide various features for modifying and amplifying the vibration amplitude and vibration distribution characteristics of the ultrasonic segmented die without altering the exposed forming surface characteristics of the die, which typically include a smooth, uniform surface with specific shape features, e.g. curvature of the leading edge of the die. FIG. 8 provides a perspective view of a forming die in accordance with an exemplary embodiment of the present invention showing the placement of two ultrasonically-excited die segments within the body of the forming die. In FIG. 8, die assembly 30 includes side wall ultrasonic die segment 32, to which first sonotrode 34 is connected; corner ultrasonic die segment 36, to which second sonotrode 38 is connected; and forming die body 40. FIG. 9 provides an illustration of an ultrasonically-excited die segment that does not include any internal structural features for shaping vibration amplitude, wherein FIGS. 10-14 provide multiple examples of such internal modifications. Modifications other than those shown in the Figures are also contemplated by and included as aspects of this invention.

[0036] FIG. 9 provides a perspective view of ultrasonically-excited die segment 100, which includes sonotrode tip 102, which extends into die segment 100 and is connected thereto or in physical contact therewith for providing ultrasonic energy to the die segment. FIG. 10 provides a perspective view of ultrasonically-excited die segment 200, which includes sonotrode tip 202, which extends into die segment 200 and is connected thereto or in physical contact therewith for providing ultrasonic energy to the die segment. Die segment 200 also includes a plurality of first transverse cylindrical bores 204 formed therein; and a plurality of second transverse cylindrical bores 206 formed therein, each of which have a different diameter than the diameter of each first transverse cylindrical bore 204. FIG. 11 provides a perspective view of ultrasonically-excited die segment 300, which includes sonotrode tip 302, which extends into die segment 300 and is connected thereto or in physical contact therewith for providing ultrasonic energy to the die segment. Die segment 300 also includes a plurality of vertical bores 304 formed therein. FIG. 12 provides a perspective view of ultrasonically-excited die segment 400, which includes sonotrode tip 402, which extends into die segment 400 and is connected thereto or in physical contact therewith for providing ultrasonic energy to the die segment. Die segment 400 also includes a vertical square or rectangular cutout 404 formed therein. FIG. 13 provides a perspective view of ultrasonically-excited die segment 500, which includes sonotrode tip 502, which extends into die segment 500 and is connected thereto or in physical contact therewith for providing ultrasonic energy to the die segment. Die segment 500 also includes a transverse cylindrical bore 504 formed therein. FIG. 14 provides a perspective view of ultrasonically-excited die segment 600, which includes sonotrode tip 602, which extends into die segment 600 and is connected thereto or in physical contact therewith for providing ultrasonic energy to the die segment. Die segment 600 also includes a plurality of transverse angled rectangular cutouts 604 formed therein. As previously indicated, numerous other geometric features are possible and all such features are considered to be within the scope of this invention.

[0037] While the present invention has been illustrated by the description of exemplary embodiments thereof, and while the embodiments have been described in certain detail, it is not the intention of the Applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention in its broader aspects is not limited to any of the specific details, representative devices and methods, and/or illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of the applicant's general inventive concept.