Abstract:
A method is provided for guaranteeing generation of 2D sketches based upon a 3D sheet metal part shape created by any type of sheet metal feature operation. The method includes performing a sheet metal feature operation to create the 3D sheet metal shape. The 3D sheet metal shape will have multiple flanges. Then an editable 2D sketch is created for each flange by obtaining geometric parameters of the 3D sheet metal shape, and linking the parameters with the appropriate generated sketch. The constraint parameters can include line segment lengths and angles between selected adjoining two line segments of the 3D sheet metal shape.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of computer-aided design for sheet metal parts. More particularly, the present invention relates to guaranteeing sketches for every flange of a 3D sheet metal part, no matter how the part was generated. 
     2. Background Information 
     Sheet metal part designers typically think of flanges as 2D problems. When designing a new 3D sheet metal shape on a computer-aided design (CAD) system, it is therefore often more convenient and simpler for sheet metal designers and manufacturers to operate with 2D representations at the flange level. Current 3D CAD systems, however do not guarantee 2D sketches for every 3D sheet metal part. Thus, the sheet metal manufacturing industry is not widely using 3D CAD systems for sheet metal part design. 
     One easy way to create a basic 3D sheet metal part shape (which can be modified later) is to use a sheet metal feature operation, such as a profile extrusion, as seen in  FIG. 1A . Unfortunately, current 3D sheet metal CAD systems do not generate 2D sketches for parts created by all sheet metal feature operations. For example, current systems represent a shape created by a profile extrusion operation with a single profile sketch and its material property. That is, 2D sketches for each created flange are not generated. Consequently, it is difficult for the designer to alter the shape of the flanges of the 3D part. 
     Currently, an editing operation of even a simple flange requires a patchwork process involving 2D and 3D manipulations, an example of which is shown in  FIG. 1B . More specifically, after creating a flange  1 , the user enters a sketch mode (which shows the flange  1  being edited in 2D) and then creates a 2D shape  2  that will be added to or deleted from the original flange  1 . In this example, the shape will be added. The user must then convert the 2D shape  2  into a solid shape  3 , and then blend the solid shape  3  with the original flange  1  to create the modified flange  4 . 
     Not only is the editing process overly complicated, but the display showing a previously edited part is unnecessarily cluttered. Typically, the user is not interested in seeing how the part was created. As seen in  FIG. 1C , however, a flange  5  that had been edited by adding the new portions  6 ,  7 ,  8  shows the history of shapes that were used to created the edited flange. Thus, the user is required to view the patchwork process used to create the edited part when making further edits. In other words, in systems of the prior art the screen becomes unnecessarily cluttered. 
     It would be desirable to have a software application that permits easy editing of a 3D part created by any type of sheet metal feature operation. Such a system should create sketches for each flange of the 3D part to permit easy editing of the flange in 2D. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, the present invention is directed to generating sketches for each flange of a 3D sheet metal shape generated by every type of sheet metal feature operation. 
     In one embodiment, a method is provided for guaranteeing generation of 2D sketches based upon a 3D sheet metal part shape. The method includes performing a sheet metal feature operation to create the 3D sheet metal shape, which has multiple flanges. The method also includes generating an editable 2D sketch for each flange to facilitate editing the 3D sheet metal shape. Thus, sketches are generated for any type of feature operation used to create the 3D sheet metal shape. 
     The generating may include obtaining parameters based upon the 3D sheet metal shape to generate each 2D sketch. In one embodiment, the sheet metal feature operation is a miter flange operation. 
     The method may also include linking constraint parameters of the created 3D sheet metal part shape with each generated sketch. The linking may include linking lengths of lines in the 3D sheet metal shape to lengths of each generated sketch. The linking may also include linking angles between selected adjoining lines of the 3D sheet metal shape to corresponding angles between generated sketches. 
     In one aspect, the sheet metal feature operation is a profile extrusion created from a profile and an extrusion length. In this case, the parameters are lengths of each line segment in the profile and the extrusion length. Each length of a line segment and the extrusion length make up the geometry of one of a several rectangles that each correspond to one of the sketches. Each sketch is associated with one of the line segments. 
     In yet another aspect of the present invention, a computer readable medium stores a program for guaranteeing generation of 2D sketches based upon a 3D sheet metal part shape. The program includes a sheet metal feature operation code segment and a sketch generating code segment. The sheet metal feature operation code segment performs a sheet metal feature operation to create the 3D sheet metal shape, which has multiple flanges. The sketch generating code segment generates an editable 2D sketch for each flange to facilitate editing the 3D sheet metal shape. Thus, sketches are generated for every type of feature operation used to create the 3D sheet metal shape. 
     The sketch generating code segment may also include a parameter code segment that obtains parameters based upon the 3D sheet metal shape to generate each 2D sketch. The sheet metal feature operation may be a miter flange operation. 
     In one embodiment, a linking code segment is provided to link constraint parameters of the created 3D sheet metal part shape with each generated sketch. The linking code segment may links lengths of lines in the 3D sheet metal shape to lengths of each generated sketch. The linking code segment may also link angles between selected adjoining lines of the 3D sheet metal shape to corresponding angles between generated sketches. 
     In another embodiment, the sheet metal feature operation is a profile extrusion operation that creates the 3D shape from a profile and an extrusion length. In this case, the parameters are lengths of each line segment in the profile and the extrusion length. Each length of a line segment and the extrusion length make up the geometry of one of a group of rectangles that corresponds to one of the sketches. Each sketch is associated with one of the line segments. 
     In another aspect of the present invention, a computer executes software for guaranteeing generation of 2D sketches based upon a 3D sheet metal part shape. The computer includes memory and a processor. The processor performs a sheet metal feature operation to create the 3D sheet metal shape, which has multiple flanges, in response to a user&#39;s input. The processor also generates an editable 2D sketch for each flange to facilitate editing the 3D sheet metal shape. Thus, sketches are generated for every type of feature operation used to create the 3D sheet metal shape. 
     The processor may obtain parameters based upon the 3D sheet metal shape to generate each 2D sketch. The processor may link constraint parameters of the created 3D sheet metal part shape with each generated sketch by linking lengths of lines in the 3D sheet metal shape to lengths of each generated sketch, and/or linking angles between selected adjoining lines of the 3D sheet metal shape to corresponding angles between generated sketches. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is further described in the detailed description that follows, by reference to the noted drawings by way of non-limiting examples of preferred embodiments of the present invention, in which like reference numerals represent similar parts throughout several views of the drawings, and in which: 
         FIGS. 1A ,  1 B, and  1 C show a 3D part created by a prior art profile extrusion operation, editing of that part according to the prior art process, and a prior art display of a previously edited part; 
         FIG. 2  illustrates a profile that can be used with a profile extrusion operation to create a 3D sheet metal part shape, in accordance with an aspect of the present invention; 
         FIG. 3  illustrates a 3D sheet metal part shape created by a profile extrusion operation and the profile of  FIG. 2 , in accordance with an aspect of the present invention; 
         FIG. 4  shows a 3D model and corresponding sketches that are generated as a result of a feature operation, according to an aspect of the present invention; 
         FIG. 5  shows an example of dimensional constraints of the profile of  FIG. 2 , according to an aspect of the present invention; 
         FIG. 6  shows an example of angular constraints of the profile of  FIG. 2 , according to an aspect of the present invention; 
         FIG. 7  shows editing of a 3D part by use of a 2D edit function, according to an aspect of the present invention; and 
         FIGS. 8A ,  8 B, and  8 C show an example of a miter flange operation, in accordance with an aspect of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention is directed to a system that guarantees sketches for each flange of a 3D sheet metal part created by any type of 3D sheet metal feature operation. The system may include software running on a computer including a processor and memory, such as random access memory (RAM). 
     Sheet metal feature operations are operations that permits quick and easy creation of complex sheet metal shapes. A profile extrusion operation will now be described with reference to  FIG. 2 . A profile  10  can be drawn. In  FIG. 2 , an X-Y axis is also shown. The profile shown in  FIG. 2  includes a set of seven continuous line segments  2 ,  4 ,  5 ,  6 ,  7 ,  8 ,  9  that define the profile. 
     After the profile is created, an extrusion operation is performed. The sheet metal part designer can select the length of the extrusion. The designer can also select a thickness of the material of the part.  FIG. 3  shows the profile after it has been extruded and thickness has been added. As seen in  FIG. 3 , seven different flanges (i.e., faces)  12 ,  14 ,  16 ,  18 ,  20 ,  22 ,  24  result from the extrusion of the profile  10 . A flange will refer to a single flange of a sheet metal part in a 3D CAD system. According to an aspect of the present invention, each flange is represented by a 2D sketch and material properties, e.g., 3 mm aluminum. 
     Creation of the sketches for the profile extrusion, shown in  FIG. 3 , is now discussed with reference to  FIGS. 4 ,  5 , and  6 . Because the profile extrusion operation generates flanges that are rectangular, the sketches resulting from this particular sheet metal part feature operation are also rectangular.  FIG. 4  shows that along with the 3D model, sketches  12 ,  14 ,  15 ,  16 ,  17 ,  18 ,  19  are generated as result of the feature operation, according to the present invention. 
     First, the constraints associated with the initial profile  10  are determined.  FIG. 5  illustrates the length of each line  2 ,  4 ,  5 ,  6 ,  7 ,  8 ,  9  of the profile  10 . The extrusion length is also determined. In this example, it will be assumed that the extrusion has a length of 10 units. The dimensions of each sketch can then be calculated. For example, lines  2 ,  4 ,  8 , and  9  have a length of 1.118 (as seen in  FIG. 5 ). Lines  5  and  7  each have a length of 0.422. Line  6  has a length of 0.992. 
     Thus, the rectangle based on line  2  has four sides having the lengths 1.118, 10, 1.118, and 10. The dimensions of each other rectangle (defining each other sketch) can be determined in a similar manner. That is, the rectangles corresponding to lines  4 ,  8 , and  9  have dimensions 1.118, 10, 1.118, and 10. The rectangles corresponding to lines  5  and  7  have dimensions 0.422, 10, 0.422, and 10. Finally, the rectangle corresponding to line  6  has dimensions 0.992, 10, 0.992, and 10. 
     Each rectangle is saved as a sketch. In an embodiment of the present invention, each line in the profile is assigned a name. The name is then linked with the corresponding flange sketch. Accordingly, handling of the sketch in a computer processor and memory is simplified. In other words, the rectangle can be saved with a sketch having the name of the corresponding profile line. 
     Angular constraints are also calculated, in accordance with an aspect of the present invention. Referring to  FIG. 6 , it can be seen that the angular relationship between each two adjacent lines of the profile  10  is calculated and displayed. In the example of  FIG. 6 , each pair of adjoining lines includes a 90 degree angle. The sketches corresponding to the adjoining lines from the profile  10  are then linked to the angles between those sketches. For example, the sketches corresponding to lines  2  and  4  include a 90 degree angle. 
     Referring to  FIG. 7 , it can be seen that according to the present invention, editing of a 3D part is straightforward. Because a 2D sketch exists for every flange, the designer need only edit the 2D sketch with a 2D edit operation. The result of the 2D editing will then be transferred to the 3D version of the part. 
     Although the previous description has been provided with reference to a profile extrusion operation, any other sheet metal feature operation that can generate a 3D part is within the scope and spirit of the present invention. Thus, although line lengths and extrusion lengths were used to determine the dimensions of each sketch, other parameters can be used, depending on the shape of the generated 3D part. Moreover, although the sketches resulting from a profile extrusion are rectangles, the sketches will be a different shape if the sheet metal feature operation generates flanges of shapes other than rectangles. 
     An example of sketch generation for a miter flange operation will now be described with respect to  FIGS. 8A ,  8 B, and  8 C. Initially a front cross section is drawn. A side cross section is then drawn.  FIG. 8A  shows the front and side cross sections drawn by the part designer. As is standard in sheet metal CAD software, the side cross section is drawn rotated 90 degrees from the front cross section. 
     Based upon the front and side cross sections, a sheet metal part is created, as shown if  FIG. 8B . Typically, the sheet metal part will include a collision area (not shown). Thus, after detecting the collision area, the system determines how to cut the flat version of the 3D part in order to prevent the collision.  FIG. 8C  shows in bold where the cut occurred to prevent a collision. 
     According to the present invention, each face is represented by a sketch. As noted above, not every flange is a rectangle. See for example flange  50 . Thus, the geometry of each flange is calculated. The calculated geometry of each flange defines each sketch. The specific calculations are not described in detail because such calculations are well known in the art. 
     Thus, the present invention generates sketches for every flange of a sheet metal part shape, no matter what type of sheet metal feature operation is used. 
     Although the invention has been described with reference to several exemplary embodiments, it is understood that the words that have been used are words of description and illustration, rather than words of limitation. Changes may be made within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the invention in its aspects. For example, sheet metal feature operations other than profile extrusion operations and miter flange operations can be used to generate the shape. Although the invention has been described with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed; rather, the invention extends to all functionally equivalent structures, methods, and uses such as are within the scope of the appended claims. 
     In accordance with various embodiments of the present invention, the methods described herein are intended for operation as software programs running on a computer processor. Dedicated hardware implementations including, but not limited to, application specific integrated circuits, programmable logic arrays and other hardware devices can likewise be constructed to implement the methods described herein. Furthermore, alternative software implementations including, but not limited to, distributed processing or component/object distributed processing, parallel processing, or virtual machine processing can also be constructed to implement the methods described herein. 
     It should also be noted that the software implementations of the present invention as described herein are optionally stored on a tangible storage medium, such as: a magnetic medium such as a disk or tape; a magneto-optical or optical medium such as a disk; or a solid state medium such as a memory card or other package that houses one or more read-only (non-volatile) memories, random access memories, or other re-writable (volatile) memories. A digital file attachment to email or other self-contained information archive or set of archives is considered a distribution medium equivalent to a tangible storage medium. Accordingly, the invention is considered to include a tangible storage medium or distribution medium, as listed herein and including art-recognized equivalents and successor media, in which the software implementations herein are stored.