Chapter One: What is a metal stamping die?

A metal stamping die is a cold forming process that begins with a strip of metal, known as a blank or tool steel. Through the use of one or multiple dies, this method cuts and shapes the metal to achieve a desired shape of sheet or profile. The force applied to the blank alters its geometry, inducing stress that renders the workpiece suitable for bending or shaping into intricate forms. Stamping Parts produced through this method can vary greatly in size, from exceptionally small to extremely large, depending on the specific application.

A metal stamping dia, also referred to as pressing, encompasses various techniques such as punching, blanking, piercing, coining, and several other operations. Precision in design is essential to ensure each punch achieves optimal quality.

Dies used in die stamping are specialized tools tailored to produce specific designs, ranging from simple everyday items to intricate computer components. They can be designed for single-function operations or as part of a sequential series of functions performed in stages. There are four types of Metal stamping die : single punch dies, progressive dies, compound dies, and transfer dies.  

When start design a stamping die, do pay attention for the steel and materials as below:   

If the stamping material has high hardness, such as stainless steel, the stamping die needs to use steel with good wear resistance material, such as Cr12MoV.

1.2 For soft materials, such as aluminum, the stamping die wear resistance requirement is slightly lower, but the stickiness of the material should be considered to avoid the material sticking to the die. You can choose a die steel with good anti-sticking properties.

For die that are subject to large impact loads during operation, such as stamping dies for large automotive covers, the material must have high toughness, and steels such as SKD11 can be selected.

If the die working environment has corrosion risks, such as working in a humid environment, you should choose a die steel with corrosion resistance, such as stainless steel.

For small batches, the performance requirements of the die material can be appropriately reduced, and lower-priced materials such as 45 steel can be selected, and appropriate heat treatment can be performed to improve the performance.

For large batches, you should choose die steel with high performance, high wear resistance, and high life. Materials such as cemented carbide can be used for stamping dies for mass production.

High-precision molds require small material deformation, such as CrWMn steel, which has small quenching deformation and is suitable for manufacturing high-precision stamping molds.

Under the premise of meeting performance requirements, the mold steel price, processing cost, etc. are comprehensively considered. For example, some new mold steels have good performance but high prices, and the cost and benefit must be weighed.

A single punch die or mold is composed of a concave mold and a punch mold or multiple concave molds and multiple punch molds. Each punch only completes one time of the forming of  punching hole or one shape because its structure and function are fixed and designed for a specific process. Metal Manufactured and cannot be applied to other processes. Usually it is for small or medium-scale production, especially for situations where the punching position or shape needs to be changed frequently. It can be flexibly adjusted and replaced during the production procession, and the single punch die cost is low. It is suitable for the production of small batches of metal stamping with relatively simple processes.

First, place the metal plate to be punched in the working area of the single punch die. The workpiece is often clamped to ensure stability during the stamping process. The punch of the single punch die descends, exerting impact force on the metal workpiece. Form the desired hole or shape. After the impact is completed, the punch will be lifted away from the workpiece to prepare for the next stamping. Then manually remove the workpiece and repeat the above operation.

2.1 Faster production – Multiple cuts can be made from several dies.

2.2 Positioning of blank – Loading and repositioning of the blank is easy. It can be turned, flipped, and shifted with little effort.

2.3 Complex geometries – Produces complex geometries without the need of special calculations or adjustments.

2.4 Handling of dies – Dies are lighter and less expensive to handle.

2.5 Tooling – Tooling is smaller and conveniently accessible.

Progressive die, it is also named continuous die or mould, is a cold stamping die that uses strip-shaped stamping raw materials in one stamping stroke, and uses several different stations to complete multiple stamping processes at the same time on a set of molds. Each stamping process of the mold is completed. Once, the material belt moves at a fixed distance, and the blanking parts are gradually formed in the continuous mold. Continuous forming is a process method with concentrated processes, it is easy to make trimming, incision, grooving, punching, plastic deformation, blanking. This process is completed on a mold.

The Progressive die can complete multiple processes in one feed. The following is the typical workflow of a progressive die:

(1) The metal plate or strip is fed into the progressive die in the form of a reel. The feed system guides the metal material to ensure its accurate positioning in the mold.

(2) The system guides the metal strip into the mold, the clamping system ensures that the metal strip remains stable during the entire stamping process, and the guiding system ensures that the metal strip is accurately positioned.

(3) First process stamping: In the first process of the progressive die, the metal strip passes through the first punch and die to complete the first stamping process, which may be punching, cutting or shape forming, etc.

(4) The metal belt guides the workpiece that has completed the first process to the location of the next process through the moving system.

(5) Second process stamping: In the second process, the metal strip passes through another set of punches and dies again to complete the second process. This process is repeated throughout the mold, with each operation being completed on a continuous strip of metal.

(6) Continue until the workpiece passes all designed processes.

(7) Discharging: After completing all processes, the workpiece is discharged from the mold for the next operation, such as assembly or subsequent processing.

3.1 Progressive dies are ideal for producing simple to moderately complex parts with repetitive shapes and uniform features.

3.2 They are highly efficient for continuous feeding of material and require minimal operator intervention.

3.3 Progressive dies are well-suited for long production runs with a consistent part design.

3.4 Each station in the die is responsible for performing a specific operation,    such as cutting, bending, punching, or forming, as the strip advances.

The compound die is a stamping die that simultaneously completes both the inner hole and outer shape processes at the same station of the die (can perform multiple stamping operations simultaneously in one stroke). Multiple processes can be completed in one stamping, including multiple punching holes or shaping of shapes. The multi-process design combines the advantages of single punch dies and progressive dies to a certain extent.

Compound Dies are applicable in many metal stamping operations. When metal stamping part requires more than one feature to be stamped and these operations can be run independently of one another, a compound die can be used. Compound dies will provide multiple metal stamping features with each stroke of the press. Furthermore, compound dies provide excellent part flatness.

4.1 Efficiency - Compound dies cut complicated parts in a single stroke avoiding the need for multiple dies.

4.2 Cost-Effectiveness - Compound die stamping manufactures parts quickly, saving time and money.

4.3 Speed -Compound die stamping produces parts in seconds and can produce over 1000 parts in an hour.

4.4 Repeatability -Using a single die in compound die stamping ensures that every part has the same dimensions and configuration.

Put the raw materials to be processed into the designated position through automatic or manual devices. When the upper mold descends under the action of the press slider, the mold and unloader and the punching punch in the upper mold first contact the strip and continue to pressurize, and then the outer edges of the punch and concave mold act on the mold and punch Punch and bumps and dips. The inner bore of the mold is simultaneously blanked and punched to separate the part from the strip.

The raw materials are directly formed after being stamped by the composite mold.

Transfer die stamping is similar to a progressive die, but parts are transferred from one station to another via a mechanical transfer system. Mainly used when parts must be removed from the strip to allow operations to be performed in a free state. The transfer mold can be a single mold or multiple molds or machines arranged in a row to form a production line. Typically used to produce more complex parts, where each workstation can perform different operations such as punching, bending, stretching and more.  

5.1 Transfer dies are suitable for complex parts that require multiple operations and precise positioning.

5.2 They are capable of producing intricate parts with tight tolerances.

5.3 Transfer dies are often used in high-volume production runs due to their efficiency and automation capabilities.

5.4 The workpiece moves between stations, and each station may perform operations like cutting, bending, punching, or coining.

transfer die stamping uses a transmission device to transfer the workpiece. After each station is stamped, the workpiece is moved mechanically or manually to the next station for stamping processing. Transfer die stamping systems can consist of multiple single distinct dies or a series of dies.

Generally, steel, aluminum, copper, stainless steel and brass are commonly applied in stamping raw materials.

6.1 The single punch die is simple and flexible, but the speed is slow.

6.2 Progressive die stamping can manufacture parts with complex geometries quickly, cost-effectively and with high repeatability.

6.3 Composite die stamping is formed in one step, so it is suitable for parts with relatively simple structures.

6.4 Transfer die is suitable for situations where multiple processes need to be completed within one stroke.

Maintenance

Remove metal chips, debris, and lubricant residue from the die after each use or at regular intervals. Use brushes, air blowers, or cleaning solvents (suitable for the die material) to keep the die surface clean. For example, in a high - volume stamping operation of automotive parts, the die may need to be cleaned daily.

Apply the appropriate lubricant regularly to reduce friction between the moving parts of the die. High - quality stamping oils or greases can prevent wear and overheating. The frequency of lubrication depends on the stamping speed and load; for a moderately used die, lubrication might be needed once a week.

Routinely check for signs of wear, such as wear marks on punches and dies, cracks, or deformation. Use visual inspection, magnifying glasses, or non - destructive testing methods like magnetic particle inspection. For example, check the cutting edges of blanking dies for signs of dullness every few thousand stamping cycles.

Sharpening or Replacing Punches and Dies

If the cutting edges of punches and dies become dull, they can be sharpened to restore their cutting ability. In cases where the wear is severe, replacing the worn - out components is necessary. For example, a punch used for piercing holes may need to be sharpened after a certain number of uses to maintain clean hole edges.

For small cracks or damaged areas on the die body, welding can be a viable repair option. However, it's crucial to use a welding process and filler material suitable for the die material to ensure the repaired area has similar properties to the original material. After welding, the repaired part usually requires heat treatment and machining to restore its shape and dimensions.

If the die components become misaligned due to vibration or impact during stamping, the alignment needs to be adjusted. This can involve shimming or using precision - adjustment mechanisms to realign the punches and dies. For example, in a progressive stamping die, misalignment can lead to inaccurate part formation, and realigning the stations can correct this issue.

A metal stamping die is a specialized tool used in the manufacturing process. It's designed to cut, shape, or form metal sheets into specific desired shapes and components.

- It typically consists of multiple parts such as the die set (including the upper and lower die halves), punches, and cavities. The punches are used to apply force to deform or cut the metal.

- There are 4 types stamping dies based on the operations they perform, like blanking dies for cutting out shapes from a larger sheet, piercing dies for creating holes, and bending dies for folding the metal.

- Dies are made from materials like tool steel which can withstand high pressures and repeated impacts during the stamping process.

- Precision in design and manufacturing is crucial as it determines the accuracy and quality of the stamped parts. They need to be properly maintained to ensure consistent performance and a long service life in industrial production settings where they play a key role in mass-producing metal components efficiently.