Patent Application
20130325423
The present invention generally relates to sheet metal forming, more particularly to determination of a trim line in a deep draw manufacturing of a sheet metal part by conducting a numerical simulation of unfolding flange of a computerized model (e.g., a finite element analysis (FEA) model) of the sheet metal part.
Sheet metal forming has been used in the industry for years for creating metal parts from a blank sheet metal, for example, automobile manufacturers and their suppliers produce many parts using sheet metal forming.
One of the most used sheet metal forming processes is deep drawing, which involves a hydraulic or mechanical press pushing a specially-shaped punch into a matching die with a piece of blank sheet metal in between. Exemplary products made from this process include, but are not limited to, car hood, fender, door, automotive fuel tank, kitchen sink, aluminum can, etc. In some areas of the die, the depth of a part or product being made is generally more than half its diameter. As a result, the blank is stretched and therefore thinned in various locations due to the geometry of the part or product. The part or product is only good when there is no structural defect such as material failure (e.g., cracking, tearing, wrinkling, necking, etc.). In order to produce a part free of these defects, it is critical to design an addendum section between the product design and the binder region.
Shown in
Product surface contains the desired pattern/shape of a sheet metal part at the end of the forming process followed by a trimming operation. Binder section is configured for holding the blank during the forming process. Addendum section provides a buffer or transition zone between the product design surface section and the binder section. After the blank is shaped by the punch, the sheet metal part is cut out along the enclosed trim lines.
A well or properly defined trim line allows the manufacturer to convert a blank into its final configuration either directly or faster hence significantly reducing the manufacturing costs of a sheet metal part. Prior art approaches of determining a trim line have been mainly dependent upon human experience or at best on an ad-hoc procedure based on trial-and-error. It would therefore be desirable to have methods of determining a trim line of a sheet metal part using a computer simulation.
This section is for the purpose of summarizing some aspects of the present invention and to briefly introduce some preferred embodiments. Simplifications or omissions may be made to avoid obscuring the purpose of the section. Such simplifications or omissions are not intended to limit the scope of the present invention.
Improved systems and methods of determining a trim line of a sheet metal part during its manufacturing procedure using a numerical simulation of unfolding flange of a computerized model are disclosed. The computerized model is suitable for a numerical simulation of deep draw sheet metal stamping process using computer aided engineering analysis (e.g., finite element analysis (FEA)) in a computer system.
According to one exemplary embodiment of the present invention, a computerized model of a sheet metal part is defined and received in a computer system having a FEA application module installed thereon. Also received in the computer system is a three-dimensional geometry of the addendum surface adjacent to product surface of the die face. At least one flange portion in the computerized model is identified. Perform a numerical simulation of unfolding of the flange portion by applying a first set of numerical loads to each pair of adjacent finite elements in the flange portions towards the addendum surface. The first set of numerical loads is configured for flattening out the pair of finite elements with a bending moment, which is determined using relative orientations of the pair of finite elements and material properties of the sheet metal part. A second set of numerical loads is applied to close any remaining gap between the unfolded flange and the addendum surface after the first set of numerical loads has been applied. A theoretical trim line is a three-dimensional closed curve disposed on the addendum surface depicting the outer edge of the flange portions in their final unfolded configuration.
Objects, features, and advantages of the present invention will become apparent upon examining the following detailed description of an embodiment thereof, taken in conjunction with the attached drawings.
These and other features, aspects, and advantages of the present invention will be better understood with regard to the following description, appended claims, and accompanying drawings as follows:
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will become obvious to those skilled in the art that the present invention may be practiced without these specific details. The descriptions and representations herein are the common means used by those experienced or skilled in the art to most effectively convey the substance of their work to others skilled in the art. In other instances, well-known methods, procedures, components, and circuitry have not been described in detail to avoid unnecessarily obscuring aspects of the present invention.
Reference herein to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Additionally, used herein, the terms “horizontal”, “vertical”, “upper”, “lower”, “top”, “bottom”, “right”, “left”, “front”, “back”, “rear”, “side”, “middle”, “upwards”, and “downwards” are intended to provide relative positions for the purposes of description, and are not intended to designate an absolute frame of reference. Further, the order of blocks in process flowcharts or diagrams representing one or more embodiments of the invention do not inherently indicate any particular order nor imply any limitations in the invention.
Embodiments of the present invention are discussed herein with reference to
The present invention is directed to an improved method of creating a computerized numerical model representing addendum section. The computerized numerical model is suitable for a computer simulation of a sheet metal forming process using computer aided engineering analysis (e.g., finite element analysis).
Referring first to
Process 200 starts at step 202 by defining and receiving a computerized model of a sheet metal part's final or any intermediate manufactured configuration and an addendum surface three-dimensional geometry in a computer system. Next, at step 204, at least one flange portion of the computerized model is identified. The flange portions represent respective flanges of the sheet metal part. There can be more than one flange in a sheet metal part, for example, one along the outer perimeter, another along an inner opening. One exemplary computerized model is a finite element analysis (FEA) model, which contains a number of finite elements. Typical finite elements for representing sheet metal part are three-dimensional shell finite elements.
A section profile of an exemplary deep draw manufacturing setup with a sheet metal part 300a (shown in thick black line) in its final or finished configuration is shown in
At step 206, process 200 conducts a numerical simulation (i.e., computer simulation using FEA) of unfolding the flange or flanges of the sheet metal part by applying a first set of numerical loads to each pair of adjacent finite elements in the identified flange portions. The first set of numerical loads is configured for flattening out each pair of finite elements towards the respective addendum surface with a bending moment, which is determined using relative orientation of the pair of finite elements and material properties of the sheet metal part (e.g., thickness, elasticity modulus of the sheet metal, and strain hardening properties, etc.).
F
1
=F
2
+F
3
F
2
×a=F
3
×b
where F1 is a numerical load at the intersection between two finite elements, F2 and F3 are numerical loads located at other corners of triangle 520 opposite to F1, “a” and “b” are projected distances from F1 to F2 and F3, respectively.
Further, user can gradually or incrementally apply the numerical loads to the computerized model in a flange unfolding simulation to maintain numerical stability or accuracy required in FEA. Those of ordinary skill in the art would appreciate such known techniques or schemes.
Referring back to
Finally, at step 210, the outer edge of the final unfolded configuration of the flange portions of the computerized model is designated as a trim line before process 200 ends. The trim line is a three-dimensional curve disposed on the addendum surface.
According to one aspect, the present invention is directed towards one or more computer systems capable of carrying out the functionality described herein. An example of a computer system 800 is shown in
Computer system 800 also includes a main memory 808, preferably random access memory (RAM), and may also include a secondary memory 810. The secondary memory 810 may include, for example, one or more hard disk drives 812 and/or one or more removable storage drives 814, representing a floppy disk drive, a magnetic tape drive, an optical disk drive, etc. The removable storage drive 814 reads from and/or writes to a removable storage unit 818 in a well-known manner. Removable storage unit 818, represents a floppy disk, magnetic tape, optical disk, etc. which is read by and written to by removable storage drive 814. As will be appreciated, the removable storage unit 818 includes a computer usable storage medium having stored therein computer software and/or data.
In alternative embodiments, secondary memory 810 may include other similar means for allowing computer programs or other instructions to be loaded into computer system 800. Such means may include, for example, a removable storage unit 822 and an interface 820. Examples of such may include a program cartridge and cartridge interface (such as that found in video game devices), a removable memory chip (such as an Erasable Programmable Read-Only Memory (EPROM), Universal Serial Bus (USB) flash memory, or PROM) and associated socket, and other removable storage units 822 and interfaces 820 which allow software and data to be transferred from the removable storage unit 822 to computer system 800. In general, Computer system 800 is controlled and coordinated by operating system (OS) software, which performs tasks such as process scheduling, memory management, networking and I/O services.
There may also be a communications interface 824 connecting to the bus 802. Communications interface 824 allows software and data to be transferred between computer system 800 and external devices. Examples of communications interface 824 may include a modem, a network interface (such as an Ethernet card), a communications port, a Personal Computer Memory Card International Association (PCMCIA) slot and card, etc. Software and data transferred via communications interface 824 are in the form of signals 828 which may be electronic, electromagnetic, optical, or other signals capable of being received by communications interface 824. The computer 800 communicates with other computing devices over a data network based on a special set of rules (i.e., a protocol). One of the common protocols is TCP/IP (Transmission Control Protocol/Internet Protocol) commonly used in the Internet. In general, the communication interface 824 manages the assembling of a data file into smaller packets that are transmitted over the data network or reassembles received packets into the original data file. In addition, the communication interface 824 handles the address part of each packet so that it gets to the right destination or intercepts packets destined for the computer 800. In this document, the terms “computer program medium” and “computer usable medium” are used to generally refer to media such as removable storage drive 814, and/or a hard disk installed in hard disk drive 812. These computer program products are means for providing software to computer system 800. The invention is directed to such computer program products.
The computer system 800 may also include an input/output (I/O) interface 830, which provides the computer system 800 to access monitor, keyboard, mouse, printer, scanner, plotter, and alike.
Computer programs (also called computer control logic) are stored as application modules 806 in main memory 808 and/or secondary memory 810. Computer programs may also be received via communications interface 824. Such computer programs, when executed, enable the computer system 800 to perform the features of the present invention as discussed herein. In particular, the computer programs, when executed, enable the processor 804 to perform features of the present invention. Accordingly, such computer programs represent controllers of the computer system 800.
In an embodiment where the invention is implemented using software, the software may be stored in a computer program product and loaded into computer system 800 using removable storage drive 814, hard drive 812, or communications interface 824. The application module 806, when executed by the processor 804, causes the processor 804 to perform the functions of the invention as described herein.
The main memory 808 may be loaded with one or more application modules 806 that can be executed by one or more processors 804 with or without a user input through the I/O interface 830 to achieve desired tasks. In operation, when at least one processor 804 executes one of the application modules 806, the results are computed and stored in the secondary memory 810 (i.e., hard disk drive 812). The status of the computer simulation of sheet metal forming process (e.g., finite element analysis results) is reported to the user via the I/O interface 830 either in a text or in a graphical representation.
Although the present invention has been described with reference to specific embodiments thereof, these embodiments are merely illustrative, and not restrictive of, the present invention. Various modifications or changes to the specifically disclosed exemplary embodiments will be suggested to persons skilled in the art. For example, whereas only one or two flanges have been described and shown, other numbers of flanges are likely in the real world parts. In summary, the scope of the invention should not be restricted to the specific exemplary embodiments disclosed herein, and all modifications that are readily suggested to those of ordinary skill in the art should be included within the spirit and purview of this application and scope of the appended claims.
