Stamping Mold

Stamping mold is a special process equipment for processing materials (metal or non-metal) into parts (or semi-finished products) in cold stamping processing, called cold stamping die (commonly known as cold stamping die). Stamping is a pressure processing method that uses a mold installed on a press to apply pressure to the material at room temperature to cause separation or plastic deformation to obtain the required parts.

There are many forms of stamping dies, and stamping dies are also classified according to the nature of work, mold structure, and mold material.

Classification According To The Nature Of The Process

• a. Punching die A die that separates materials along a closed or open outline. Such as blanking die, punching die, cutting die, slitting die, trimming die, cutting die, etc.
• b. Bending mold A mold for bending and deforming the sheet blank or other blanks along a straight line (bending line) to obtain a certain angle and shape of the workpiece.
• c. The drawing die is a die for making the blank of the sheet into an open hollow part, or to further change the shape and size of the hollow part.
• d. Forming mold is a mold that directly replicates the blank or semi-finished workpiece according to the shape of the convex and concave molds, and the material itself only generates local plastic deformation. Such as bulging molds, necking molds, flaring molds, undulating forming molds, flanging molds, shaping molds, etc.
• e. Riveting mold is to use external force to connect or overlap the participating parts in a certain order and manner to form a whole

Classification According To The Degree Of Process Combination

• a. Single-process mold In one stroke of the press, only one stamping process mold is completed.
• b. Compound mold There is only one station, and in one stroke of the press, two or more stamping processes can be completed at the same time on the same station.
• c. Progressive die (also called continuous die) In the feeding direction of the blank, there are two or more stations. In one stroke of the press, two or two passes are completed in different stations one by one. Die for the above stamping process.
• d. The transfer mold combines the characteristics of single process mold and progressive mold. The robot transfer system is used to realize the rapid transfer of the product in the mold, which can greatly improve the production efficiency of the product, reduce the production cost of the product, save the cost of the material, and have stable quality reliable.

Classified According To The Processing Method Of The Product

According to different product processing methods, molds can be divided into five categories: punching and shearing molds, bending molds, drawing molds, forming molds and compression molds.

• a. Punching and shearing dies: the work is done by shearing. Commonly used forms are shearing dies, blanking dies, punching dies, trimming dies, edge dies, punching dies and punching dies.
• b. Bending mold: It is the shape of bending the flat blank into an angle. Depending on the shape, accuracy and production volume of the part, there are many different forms of mold, such as ordinary bending die, cam bending die, curling Stamping dies, arc bending dies, bending punching dies and twisting dies, etc.
• c. Drawing mold: Drawing mold is to make flat blank into seamless container with bottom.
• d. Forming die: refers to the use of various local deformation methods to change the shape of the blank. Its forms include convex forming die, curling edge forming die, necking forming die, hole flange forming die, and round edge forming die.
• e. Compression die: It uses strong pressure to make the metal blank flow and deform into the required shape. Its types include extrusion die, embossing die, embossing die, and end pressure die.

Basic Knowledge Of Stamping Die Terminology

1. Hemming: Hemming is a stamping process in which the edge of the process part is rolled into a closed circle. The axis of the crimped circle is straight.
2. Rolling edge: Rolling edge is a stamping process in which the upper edge of the hollow part is rolled into a closed circle.
3. Drawing: Drawing is a stamping process that transforms straight wool or process parts into a curved surface. The curved surface is mainly formed by the extension of the material at the bottom of the punch.
4. Stretch-bending: Stretch-bending is a stamping process in which bending deformation is realized under the combined action of tensile force and bending moment, so that the entire bending cross section is subjected to tensile stress.
5. Bulging: Bulging is a stamping process in which hollow or tubular parts are expanded radially outward. Sectioning Sectioning is a stamping process that divides the forming process into several pieces.
6. Leveling: Leveling is a stamping process to improve the flatness of partial or overall planar parts.
7. The undulating forming: The undulating forming is a metal stamping process that relies on the extension of the material to make the process parts form partial depressions or protrusions. The change of material thickness in the undulating forming is unintentional, that is, a small amount of change in thickness is formed naturally during the deformation process and is not a requirement specified by the design.
8. Bending: Bending is a stamping process that uses pressure to produce plastic deformation of the material, thereby being bent into a shape with a certain curvature and a certain angle.
9. Chiseling: Chiseling is a process of blanking or punching using a sharp-edged chiseling die. There is no lower die for chiseling, only a flat plate is under the material, and most of the material to be punched is non-metal.
10. Deep hole punching: Deep hole punching is a punching process when the hole diameter is equal to or less than the thickness of the material being punched.
11. Blanking: Blanking is a stamping process that separates materials along a closed contour. The separated materials become workpieces or process parts, most of which are flat.
12. Retracting: Retracting is a stamping process that pressurizes the opening of a hollow or tubular member to shrink it.
13. Shaping: Shaping is a stamping process that relies on the flow of materials and changes the shape and size of the process parts in a small amount to ensure the accuracy of the workpiece.
14. Refurbishment: Refurbishment is a punching process in which a small amount of material is cut along the outer or inner contour to improve the edge finish and verticality. The refurbishment process generally also improves the dimensional accuracy.
15. Hole turning: Hole turning is a punching process that turns the material into a side flange along the inner hole.
16. Flanging: Flanging is a stamping process that turns the material into short sides along the contour curve.
17. Deep drawing: Deep drawing is a stamping process in which straight wool or process parts are turned into hollow parts, or the hollow parts are further changed in shape and size. During deep drawing, the hollow part is mainly formed by the material located outside the bottom of the convex die flowing into the concave die.
18. Continuous drawing: Continuous drawing is a stamping method that uses the same mold (continuous drawing die) to gradually form the required shape and size through multiple drawing on the strip (coil).
19. Thinning and deep drawing: Thinning and deep drawing is a kind of drawing process in which the hollow process parts are further changed in shape and size, and the side wall is intentionally thinned.
20. Reverse drawing: Reverse drawing is a drawing process in which the inner wall of the hollow process part is turned out.
21. Differential temperature drawing: Differential temperature drawing is a drawing process that uses heating and cooling means to make the temperature of the material to be deformed far higher than the temperature of the material that has been deformed, thereby increasing the degree of deformation.
22. Hydraulic drawing: Hydraulic drawing is a drawing process that uses liquid contained in a rigid or flexible container to replace a punch or die to form a hollow part.
23. Bead: Bead is a kind of undulation. When local undulations appear in the form of ribs, the corresponding undulation forming process is called press ribs.

Stamping Mold Materials

The materials used to manufacture stamping dies include steel, cemented carbide, steel-bonded cemented carbide, zinc-based alloys, low melting point alloys, aluminum bronze, polymer materials, and so on. Most of the materials used to make stamping mold are steel. Commonly used types of die working parts are: carbon tool steel, low-alloy tool steel, high-carbon high-chromium or medium-chromium tool steel, medium-carbon alloy steel, high-speed steel , Base steel and cemented carbide, steel bonded cemented carbide, etc.

Basic Classification

a. Carbon tool steel

The most commonly used carbon tool steels in molds are T8A, T10A, etc., which have the advantages of good processing performance and low price. However, the hardenability and red hardness are poor, the heat treatment deformation is large, and the bearing capacity is low.

b. Low alloy tool steel

Low-alloy tool steel is based on carbon tool steel with an appropriate amount of alloying elements. Compared with carbon tool steel, it reduces quenching deformation and cracking tendency, improves the hardenability of steel, and has better wear resistance. Low-alloy steels used to make molds include CrWMn, 9Mn2V, 7CrSiMnMoV (code CH-1), 6CrNiSiMnMoV (code GD) and so on.

c. High carbon and high chromium tool steel

Commonly used high carbon and high chromium tool steels are Cr12 and Cr12MoV, Cr12Mo1V1 (code D2), SKD11, they have good hardenability, hardenability and wear resistance, heat treatment deformation is very small, for high wear resistance micro-deformation die steel , The carrying capacity is second only to high-speed steel. However, the segregation of carbides is serious, and repeated upsetting (axial upsetting, radial upsetting) and forging must be carried out to reduce the unevenness of carbides and improve the performance.

d. High carbon medium chromium tool steel

The high-carbon medium-chromium tool steels used for molds include Cr4W2MoV, Cr6WV, Cr5MoV, etc. They have low chromium content, less eutectic carbides, uniform carbide distribution, small heat treatment deformation, good hardenability and dimensional stability. Sex. Compared with high carbon and high chromium steel with relatively serious carbide segregation, the performance is improved.

e. High-speed steel

High-speed steel has the highest hardness, wear resistance and compressive strength among die steels, and has a high load-bearing capacity. Commonly used in molds are W18Cr4V (code 8-4-1) and W6Mo5 Cr4V2 (code 6-5-4-2, American brand M2) with less tungsten content, and high-speed steel for reducing carbon and vanadium developed to improve toughness 6W6Mo5 Cr4V (code 6W6 or low carbon M2). High-speed steel also needs to be forged to improve its carbide distribution.

f. Base steel

Add a small amount of other elements to the basic composition of high-speed steel, and appropriately increase or decrease the carbon content to improve the performance of the steel. Such steel types are collectively referred to as base steel. They not only have the characteristics of high-speed steel, have certain wear resistance and hardness, but also have better fatigue strength and toughness than high-speed steel. They are high-strength and toughness cold-worked die steels, and the material cost is lower than that of high-speed steel. The commonly used base steels in molds are 6Cr4W3Mo2VNb (code 65Nb), 7Cr7Mo2V2Si (code LD), 5Cr4Mo3SiMnVAL (code 012AL) ​​and so on.

g. Cemented carbide and steel bonded cemented carbide

The hardness and wear resistance of cemented carbide are higher than any other type of die steel, but the bending strength and toughness are poor. The cemented carbide used as the mold is tungsten-cobalt. For molds with low impact resistance and high wear resistance, cemented carbide with lower cobalt content can be selected. For high-impact molds, cemented carbide with higher cobalt content can be selected.

Steel-bonded cemented carbide is made by adding a small amount of alloying element powder (such as chromium, molybdenum, tungsten, vanadium, etc.) to iron powder as a binder, using titanium carbide or tungsten carbide as the hard phase, and sintering by powder metallurgy. The matrix of steel-bonded cemented carbide is steel, which overcomes the disadvantages of poor toughness and difficult processing of cemented carbide. It can be cut, welded, forged and heat treated. Steel-bonded cemented carbide contains a large amount of carbides. Although the hardness and wear resistance are lower than that of cemented carbide, it is still higher than other steel grades. The hardness can reach 68 ~ 73HRC after quenching and tempering.

h. New materials

The material used in the stamping mold belongs to cold-work die steel, which is the most widely used die steel with a wide range of applications. The main performance requirements are strength, toughness, and wear resistance. The development trend of cold work die steel is based on the performance of high alloy steel D2 (equivalent to my country’s Cr12MoV), divided into two major branches: one is to reduce the carbon content and the amount of alloying elements, and to improve the uniformity of carbide distribution in the steel. Highlight the toughness of the mold. Such as 8CrMo2V2Si from Vanadium Alloy Steel Company in the United States and DC53 (Cr8Mo2SiV) from Datong Special Steel Company in Japan. The other is powdered high-speed steel developed for the main purpose of improving wear resistance to adapt to high-speed, automated, and mass production. Such as 320CrVMo13 in Germany, etc.

Selection Principle

In the stamping die, various metal materials and non-metal materials are used, mainly carbon steel, alloy steel, cast iron, cast steel, cemented carbide, low melting point alloy, zinc-based alloy, aluminum bronze, synthetic resin, polyurethane Rubber, plastic, laminated birch wood, etc.

The material used to make the mold requires high hardness, high strength, high wear resistance, appropriate toughness, high hardenability, no deformation (or less deformation) after heat treatment, and resistance to cracking during quenching.

Reasonable selection of mold materials and implementation of the correct heat treatment process are the keys to ensuring the life of the mold. For molds with different uses, comprehensive consideration should be given to factors such as their working conditions, stress conditions, properties of the processed material, production batch size, and productivity, and the various properties of the above requirements should be emphasized, and then the steel type and heat treatment should be made. The corresponding choice of craft.

When the production batch of stamping parts is large, the material of the punch and the die of the working parts of the mold should be high quality, good wear resistance mold steel. The parts and materials of other process structure parts and auxiliary structure parts of the mold should be improved accordingly. When the batch is not large, the requirements for material properties should be appropriately relaxed to reduce costs.

When the material to be stamped is hard or has a large deformation resistance, the convex and concave dies of the die should be selected from materials with good wear resistance and high strength. When drawing stainless steel, aluminum bronze die can be used, because it has better anti-adhesion. The guide pin and guide sleeve require wear resistance and good toughness, so low-carbon steel surface carburizing and quenching are often used. For another example, the main disadvantage of carbon tool steel is poor hardenability. When the cross-sectional size of the die parts is large, the center hardness is still low after quenching. However, when working on a press with a large number of strokes, due to its resistance Good impact becomes an advantage. For parts such as fixed plates and unloading plates, not only must have sufficient strength, but also require small deformation during the working process.

In addition, cold treatment and cryogenic treatment, vacuum treatment and surface strengthening methods can also be used to improve the performance of mold parts. For cold extrusion dies with poor working conditions for convex and concave dies, mold steels with sufficient hardness, strength, toughness, wear resistance and other comprehensive mechanical properties should be selected, and they should have a certain degree of red hardness and thermal fatigue strength, etc. .

• The hot and cold processing performance of the material and the existing conditions of the factory should be considered.
• Pay attention to the use of micro-deformed die steel to reduce machining costs.
• For molds with special requirements, mold steels with special properties should be developed and applied
• The choice of mold material should be determined according to the use conditions of the mold parts, so that the main conditions are met, and low-cost materials are selected to reduce costs.

Assistive Technology

Mold CAD/CAM technology

The rapid development and organic combination of computer technology, mechanical design and manufacturing technology have formed a new technology of computer-aided design and computer-aided manufacturing (CAD/CAM).

CAD/CAM is a key technology to transform traditional mold production methods. It is a high-tech and high-efficiency system engineering. It provides users with an effective auxiliary tool in the form of computer software, so that engineers and technicians can use computers to control products. , Mold structure, forming process, cnc machining and cost design and optimization. Mold CAD/CAM can significantly shorten the mold design and manufacturing cycle, reduce production costs, and improve product quality has become a consensus.

With the emergence of powerful professional software and efficient integrated manufacturing equipment, mold CAD/CAM technology based on 3D modeling and concurrent engineering (CE) is becoming the direction of development. It can realize manufacturing and assembly-oriented design and realize forming Process simulation and NC machining process simulation integrate design and manufacturing.

In order to meet the needs of multi-variety and small-batch production in industrial production, speed up mold manufacturing, reduce mold production costs, rapid economic mold making technology, the development and application of rapid economic mold making technology has attracted more and more attention. Rapid economical molding technology mainly includes low melting point alloy molding technology, zinc-based alloy molding technology, epoxy resin molding technology, spray forming molding technology, laminated steel plate molding technology, etc.

The application of rapid and economical mold making technology to manufacture molds can simplify mold manufacturing processes, shorten manufacturing cycles (70% to 90% shorter than ordinary steel mold manufacturing cycles), and reduce mold production costs (60% to 80% lower than ordinary steel mold manufacturing costs ), has achieved significant economic benefits in industrial production. It plays a very important role in increasing the development speed of new products and promoting the development of production.