**3.3 Application of designing with case-based reasoning**

Designing a die face is an art; that is, it is difficult to systemize. However, some sheet metal parts share common features, enabling reuse of similar cases to reduce design time.

Among all procedures when designing a die face, the most difficult task is designing the addendum part, which affects all operations and involves choosing an appropriate section type and size, and determining the position of trim points. All these tasks require tacit knowledge (Polanyi, 1958) and, thus, design time is considerable. Therefore, this study applies CBR to locate a similar case (Schenk & Hillmann, 2004) to accelerate design time.

This study combines CBR when designing a die face for a sheet metal panel with KBE (Fig. 18). To make the system flexible, the scale of reuse can be based on the degree of similarity between two sheet metal parts. If only a few features are shared, then only those features would be adopted; this is called local reuse. Conversely, if many similarities exist, then reuse can involve the entire addendum design; this is called global reuse.

The area or items that can be reused from previous cases are those that are difficult to design and their design is time-consuming. For a die face, only the addendum meets this criterion. The product-in face and product-out face parts are relatively easy to design and are not reused.

Two examples are used to demonstrate how local reuse and global reuse operate.

Fender B is an example of local reuse. After constructing its binder and the parting line of the die face, CBR is applied and the design of the addendum of, say, fender A is used to reduce design time. Due to the shape complexity of fender B, similarity is only for relatively small parts and, thus, only a small portion of the previous design is reused.

The procedures for reusing the design of fender A for fender B are listed as follows.


Fig. 18. Design process integrated with case-based reasoning

Fig. 19. Fender A

Similarity Compared item Data Type Weight

Designing a die face is an art; that is, it is difficult to systemize. However, some sheet metal

Among all procedures when designing a die face, the most difficult task is designing the addendum part, which affects all operations and involves choosing an appropriate section type and size, and determining the position of trim points. All these tasks require tacit knowledge (Polanyi, 1958) and, thus, design time is considerable. Therefore, this study applies CBR to locate a similar case (Schenk & Hillmann, 2004) to accelerate design time. This study combines CBR when designing a die face for a sheet metal panel with KBE (Fig. 18). To make the system flexible, the scale of reuse can be based on the degree of similarity between two sheet metal parts. If only a few features are shared, then only those features would be adopted; this is called local reuse. Conversely, if many similarities exist, then reuse

The area or items that can be reused from previous cases are those that are difficult to design and their design is time-consuming. For a die face, only the addendum meets this criterion. The product-in face and product-out face parts are relatively easy to design and are not

Fender B is an example of local reuse. After constructing its binder and the parting line of the die face, CBR is applied and the design of the addendum of, say, fender A is used to reduce design time. Due to the shape complexity of fender B, similarity is only for relatively

**Step 2.** Select a portion of the boundary of fender B that is similar to that of fender A

**Step 3.** Select the corresponding boundary of fender A (Fig. 19) and then apply it to the

**Step 4.** After reusing the design of fender A, a user can decide whether to adopt the reused design. The final reuse result is stored in a database for future reuse.

design of fender B. In this case, only the radius of chamfer, draft angle, and addendum design are reused. Other parts, such as the trimming line, are designed

Two examples are used to demonstrate how local reuse and global reuse operate.

The procedures for reusing the design of fender A for fender B are listed as follows.

small parts and, thus, only a small portion of the previous design is reused.

**Step 1.** Locate the most similar case—fender A (Fig. 19).

parts share common features, enabling reuse of similar cases to reduce design time.

f : area ratio (product-out face to product-in face)

f : connecting line (the line that connect product-out face and product-in face)

f : angle (between product-out face and product-in face)

f : the existence of undercut Boolean 3

float 1

float 1

float 1

A B

A B 2 2 s(f , f ) 2

A B 3 3 s(f , f )

A B 4 4 s(f , f ) 4

reused.

(Fig. 20).

all over again.

1 1 s(f , f ) 1

3

Table 1. Similarity of items of product-out face

**3.3 Application of designing with case-based reasoning** 

can involve the entire addendum design; this is called global reuse.

Knowledge-Based Engineering Supporting Die Face Design of Automotive Panels 35

Take hood B as a global reuse example. Fig. 24-Fig. 27 show hood A and hood B and their section views. Considerable similarity exists between hood B and hood A; thus, many parameters of hood A are adopted for hood B such as type of the section curve, radius of

Fig. 23. The features that reused parameters of previous case

Fig. 24. Hood A

chamfer, draft angle, addendum design, and trimming angle (Fig. 28).

Fig. 20. Fender B

Fig. 21 shows the detailed explanation of addendum A. The reused parameters (Fig. 22) include the radius of section curve and the draft angle (Fig. 23); other parameters of, such as the addendum and trimming line, are new designs.

Fig. 21. Addendum of fender A

Fig. 22. Addendum of fender B that reused parameters of fender A

Fig. 23. The features that reused parameters of previous case

Take hood B as a global reuse example. Fig. 24-Fig. 27 show hood A and hood B and their section views. Considerable similarity exists between hood B and hood A; thus, many parameters of hood A are adopted for hood B such as type of the section curve, radius of chamfer, draft angle, addendum design, and trimming angle (Fig. 28).

Fig. 24. Hood A

34 Industrial Design – New Frontiers

Fig. 21 shows the detailed explanation of addendum A. The reused parameters (Fig. 22) include the radius of section curve and the draft angle (Fig. 23); other parameters of, such as

Fig. 20. Fender B

Fig. 21. Addendum of fender A

the addendum and trimming line, are new designs.

Fig. 22. Addendum of fender B that reused parameters of fender A

Knowledge-Based Engineering Supporting Die Face Design of Automotive Panels 37

This study developed a framework in which KBE replaces the conventional method of designing a die face that relies heavily on designer experience and repeated trial and error, especially for addendum design due to the unpredictability of metal blank flow. With KBE techniques, designers can apply parameters from similar cases to a new case. In this study, feature recognition and case representation use features to describe cases and CBR compares

The questions faced after integrating KBE into the design process of a die face is that, due to the geometric complexity of a die face, reuse may not be successful. Additionally, reuse relies heavily on retrieved cases from a case database, meaning that if previous cases are

In the future, as the number of cases in the case database increases, CBR can search among an increasing number of possibilities to find the most similar case, resulting in desirable reuse. Furthermore, the reuse concept can be extended to the entire die design process, such

The authors would like to thank the engineers of Gordon Auto Body Parts Co., Ltd. for their technical supports. Ted Knoy is appreciated for his editorial assistance.The authors would like to thank the National Science Council of the Republic of China, Taiwan, for financially

supporting this research under Contract No. NSC-100-2221-E-002-061-MY2.

Fig. 28. The features that reused parameters of previous case

poor or the case database is biased, reuse is not desirable.

that convenience for die designers can be increased.

**4. Conclusion and discussion** 

features to determine their similarity.

**5. Acknowledgement** 

Fig. 27. Section view of addendum of hood B that reused parameters of hood A

Fig. 28. The features that reused parameters of previous case
