**2.1 Introduction to the die face**

Fig. 3 lists the factors that should be considered when designing a die face for an automotive fender.


Die face design can be divided into three parts—product-in face, product-out face, and binder. Fig. 4 shows a die face cross section. A sheet metal surface generally has two parts product-in face and product-out face. Product-out face is the largest boundary that must be restriked because it can only be shaped after drawing, and is not included in the die face. Product-in face is the outside of a sheet metal piece that can be seen after being assembled in an automobile and is shaped during drawing and, thus, is included in the die face.

### Fig. 3. Features on fender design

22 Industrial Design – New Frontiers

A trimming mold is used to cut sheet metal into an appropriate size and shape, such that the restriking mold can bend. During this operation, the most essential factor is trim cutter and scrap cutter position in a combination that enables sheet metal scrap to automatically drop

Restriking is an operation in which sheet metal is molded into a desired shape. The main activities in this process are flanging and restriking. Flanging refers to the process of folding edges at a 90° angle, while restriking refers to folding at any angle and is usually driven by a cam for wide areas. When designing a mold for restriking, one should compensate for

Piercing is typically the last operation. When piercing is done prior to restriking, the

The die face plays a crucial role in drawing operations as it determines operation quality (Makinouchi, 1996). Not only does the design have to prevent sheet metal from cracking, wrinkling, offset of the characteristic line, it also has to take the following factors into consideration including compensation of springback, and whether the trimming mold should use normal cams or suspended cams, whether the restriking mold should use a convex hull, and piercing direction. Designers usually search for previous successful cases as references when designing a new die face. This design process is explained in Section 2.2.

Fig. 3 lists the factors that should be considered when designing a die face for an automotive

1. Product-in face: The part of a sheet metal that would be shaped during the drawing

2. Binder: The binder is the area that a piston presses against on an upper mold to ensure

3. Drawbead: The drawbead controls tension resistance of a metal blank during drawing. 4. Convex hull: The convex hull stores prepared materials to avoid sheet metal cracking

5. Stamp mark: A stamp mark is used when determining whether the upper mold and

7. Trimming line: The trimming line is a rough profile of the boundary of a piece of sheet metal. During trimming, the sheet metal is trimmed along this line to facilitate

Die face design can be divided into three parts—product-in face, product-out face, and binder. Fig. 4 shows a die face cross section. A sheet metal surface generally has two parts product-in face and product-out face. Product-out face is the largest boundary that must be restriked because it can only be shaped after drawing, and is not included in the die face.

6. Parting line: The parting line is a line separating the lower mold and piston.

operation (excluding the areas that would be folded afterwards).

the metal blank remains stationary during drawing.

springback, which can be determined based on raw material characteristics.

position of a hole can move or hole shape can deform during shaping.

2. Trimming (TR) mold

3. Restriking (RST) mold

4. Piercing (PI) mold

**2. Die face** 

fender.

and be removed after trimming.

**2.1 Introduction to the die face** 

while folding.

restriking.

lower mold are in full contact.

Addendum is the surplus area outside the product-in face that facilitates drawing operations; thus, when designing an addendum, the quality and strength of a sheet metal piece after drawing must be considered.

Fig. 4. Divisions on die face

Normally when designing a die face, except for such parts as product-in face, the addendum, and binder—the three main parts—other features like drawbead and the stamp mark during the drawing operation, trimming line during the trimming operation, and convex hull during the restriking operation are also included in die face to facilitate those operations.
