**2.2 Designing a die face**

Fig. 5 shows the design process for a die face. When stamping a piece of sheet metal, no area should be unable to be pressed; that is, undercut (Fig. 6). The upper mold and lower mold should be fully pressed against each other during drawing and all areas that must be drawn should be drawn at one time; therefore, avoiding an undercut is the first priority when designing a die face.

Knowledge-Based Engineering Supporting Die Face Design of Automotive Panels 25

by the product-in face during stamping (Fig. 9). In such cases, cams should be utilized to change the direction of stamping forces to horizontal to form surfaces that are undercut.

Fig. 7. Surface features on sheet metal

Fig. 8. Feature graph of sheet metal

Fig. 9. Features on product-out face

Fig. 5. Design process of die face

Fig. 6. Undercut

### **2.2.1 Feature recognition**

The first step in designing molds for sheet metal automotive panels is to determine the stamping angle, such that subsequent operations can be successful. Typically, the outer appearance of a panel should be included in the product-in face and be formed during the first operation to yield the highest surface quality with the largest stamping force among all the operations.

A die face can be divided into two parts. One is product-in face and, when designing it, its face cannot have an undercut, and radius of chamfer should be >3mm to prevent cracking while drawing. If these requirements cannot be met, an addendum can be added, such that some tasks can be done in later operations.

The area of a sheet metal outside of a product-in face is called product-out face, which is divided into connecting features and corners (Fig. 7). The design of a product-out face focuses on how to facilitate restriking and bending operations. A product-out face can be divided into several parts and cams can be used to shape each part.

The case in this study considers product-out face as a feature (Fig. 8), and is adopted from the previous works (Tor et al., 2003; Zheng & Wang, 2007).

Factors are considered when designing a die face and cams are the existence of an undercut, area and length of the line connecting the product-out face to the product-in face, and the angle between the product-in face and the product-out face. Thus, this study uses these features to describe the product-out face. In some cases, undercut surfaces may be blocked by the product-in face during stamping (Fig. 9). In such cases, cams should be utilized to change the direction of stamping forces to horizontal to form surfaces that are undercut.

Fig. 7. Surface features on sheet metal

24 Industrial Design – New Frontiers

Determining stamping direction

Designing stamp mark, convex hull

Designing binder, parting line

Designing addendum

Feature recognition

> Designing trimming line

The first step in designing molds for sheet metal automotive panels is to determine the stamping angle, such that subsequent operations can be successful. Typically, the outer appearance of a panel should be included in the product-in face and be formed during the first operation to yield the highest surface quality with the largest stamping force among all

A die face can be divided into two parts. One is product-in face and, when designing it, its face cannot have an undercut, and radius of chamfer should be >3mm to prevent cracking while drawing. If these requirements cannot be met, an addendum can be added, such that

The area of a sheet metal outside of a product-in face is called product-out face, which is divided into connecting features and corners (Fig. 7). The design of a product-out face focuses on how to facilitate restriking and bending operations. A product-out face can be

The case in this study considers product-out face as a feature (Fig. 8), and is adopted from

Factors are considered when designing a die face and cams are the existence of an undercut, area and length of the line connecting the product-out face to the product-in face, and the angle between the product-in face and the product-out face. Thus, this study uses these features to describe the product-out face. In some cases, undercut surfaces may be blocked

divided into several parts and cams can be used to shape each part.

the previous works (Tor et al., 2003; Zheng & Wang, 2007).

OEM sheet metal

Fig. 5. Design process of die face

Die face

Fig. 6. Undercut

the operations.

**2.2.1 Feature recognition** 

some tasks can be done in later operations.

Designing drawbead

Fig. 8. Feature graph of sheet metal

Fig. 9. Features on product-out face

Knowledge-Based Engineering Supporting Die Face Design of Automotive Panels 27

Designers first construct the parting line as a limitation in subsequent design steps (Fig. 12). The addendum surface is then designed, which is composed of a section curve and connecting curve (Dy et al., 2008). The section curve determines how the addendum is shaped and is a concern for subsequent operations. The connecting curve connects section

When using programs to construct an addendum, the trimming point should lie on the trimming face and a connected curve along the shape of the sheet metal panel should be used to make its surface smooth. The design platform in this study is based on the SpringSolid system developed by the Solid Model Laboratory, National Taiwan University

Knowledge-based engineering (KBE) refers to the concept of a knowledge database applied in engineering that can be regarded as an intelligent system in a specific engineering field in which experts modularize product information and design processes to assist in product design. The design process is then stored for knowledge management. KBE is also combined widely with CAD/CAE/Computer-Aided Manufacturing (CAM) software for design,

The KBE system is composed of a database and reasoning engine; the database stores

Retrieval and case representation of knowledge are two crucial elements of a knowledge database. First, KBE engineers retrieve related knowledge from books, experts, and other resources, and record this knowledge using an appropriate knowledge representation. A representation should be able to store related knowledge in that field to enable a system to read and show that knowledge such that the knowledge can be provided to the reasoning

Fig. 13 shows case-based reasoning (CBR) operations. CBR compares cases in an analogue way. First, CBR compares a new case with cases in a case database and searches for the most

curves to produce a smooth surface. Finally, chamfer at the parting line.

**2.2.5 Addendum construction** 

Fig. 12. Addendum construction

**3. Knowledge-based engineering** 

analysis, and manufacturing, respectively.

engine.

similar case.

**3.1 Case-based reasoning** 

related knowledge and assists in design via the reasoning engine.

and written in Java.
