Three Typical Structure of Dies

The historical development of tungsten carbide heading dies

WC-Co (Cemented Carbide) was developed as a material for wire drawing dies. It is not clear when the use of WC-Co (cemented carbide) for cold forging began, but it can be assumed that it was used from the beginning of the development of cold forging in Germany (around 1940).

Tungsten carbide tools were well known in Japan, but in the 1960s die steel (SKD11) was dominant, and from the 1980s onwards, high speed steel (HSS) and WC-Co (carbide) began to be used regularly. More recently, WC-Co (carbide) has been used more often in order to improve the accuracy of cold forged products, which is strongly influenced by the elastic deformation of the tool.

The above trend is more pronounced in the cold heading process and there is a certain evaluation that WC-Co (carbide) is absolutely indispensable.

Cropping Knife For Mould Associate Tool

We will explain the three typical constructions of dies and their manufacturing methods.

General purpose heading dies

Typically, heading dies have a WC-Co (Cemented Carbide) structure and the die steel is used to reinforce the WC-Co (Cemented Carbide).

Not all dies are made of WC-Co (Cemented Carbide) as it is a rigid hair material and very expensive.

We produce the mould material by punching a hole in the mould steel and then producing a heat shrink fit and press fit in that hole.

We then perform small-hole EDM, wire-cut EDM and sinker EDM hole machining on the WC-Co (cemented carbide) parts. This part becomes the core that is actually used for component production. Therefore, we finish it with grinding inside the hole in mirror condition. Depending on its quality, the service life of the die may change several times. It would not be an exaggeration to say that one turn of machining records the life of the mould.

The Mould of The Cropping

Assembling the die

When we design heading dies and punches, if in cases where their shape may be fragile due to load concentration. Or in cases where the desired shape cannot be provided due to air or oil collecting in the material, we will be able to solve these problems by splitting the inside of the heading die.

Assembling the mould

Tungsten carbide two-piece punches

Tungsten carbide dies are divided into pins and set pins folders

For one-piece moulded shapes with pins and clips, the stresses are concentrated at the root of the pin. The die may then be damaged in this area. Tungsten carbide two-piece punches are suitable for high volume production of stainless steel hexagonal head screws and can prevent very strong stresses being placed on the die. Because the internal hexagonal head is not like a positive or negative shape, it is difficult to form due to the unique shape of the internal hexagon.

As a result, it will perform in the mass production of such complex shapes. Typically, HSS one-piece punches are used for this production, but the tool life is very short. On the other hand, tungsten carbide two-piece punches last 15 to 30 times longer than HSS punches, and even if the pins wear out, you can sharpen them again and reuse them.

When the head is processed, there is a danger of burrs coming out on the product when there is a gap between the large head pin and the folder. To solve this problem, we measure the shape of the large head pin by using 3D measuring equipment after making the head pin, and make the folder based on the data. Because we are able to suppress the gap to around a few microns, no burrs appear.