Stamping

What Is Stamping?

Metal Stamping definition: The stamping process is a processing method in which an external force is applied to the blank through a mold to cause it to be plastically deformed or separated, thereby obtaining a workpiece of a certain size, shape and performance. The stamping process has a wide range of applications, which can process metal sheets and bars, as well as a variety of non-metallic materials. Since processing is usually carried out at room temperature, it is also called cold stamping.

Cold Stamping Process

Since stamping is the use of the force of conventional or special stamping equipment, the sheet in the mold is directly subjected to deformation force and deformation, and the manufacturing process of product parts has a certain shape, size and performance.

The latter is carried out at room temperature and is a common stamping method for sheets. It is one of the main methods of metal-plastic processing (or pressure processing) and is also related to material molding technology.

The mold used for stamping is called a mold. Molds are a special tool for batch processing the required stamping material (metal or non-metal). Molds are very important for stamping and it is difficult to produce batch stamping because the molds do not meet the requirements. Without advanced molding, an advanced stamping process cannot be achieved. The stamping process and mold, stamping device and stamping material form the three elements of stamping. Stamping is only available when you combine them.

Sheets, molds and equipment are the three elements of stamping.

Stamping temperature is divided into hot stamping and cold stamping.The former is suitable for sheet metal processing with high deformation resistance and low plasticity.


The Features Of The Stamping Process

Metal Stamping Parts

a. Advantages

  • – Stable quality, good interchangeability
  • – Manufacturing thin wall, high surface quality, high strength, complex shape parts
  • – Energy saving, saving metal
  • – High efficiency
  • – Simple and easy operation

b. Disadvantages

  • – The shape of the part must be suitable for the shape of the stamping process
  • – Molds are mostly specialized
  • – Single-piece production of stamping molds, high precision, high technical requirements, and high cost
  • – It takes considerable time to make the mold
  • – Due to the different shapes of parts, the punch (press) beds suitable for processing are also different
  • – There is a need for a fairly spacious working place and storage space.
  • – Work hazard and injury rate (8)   Produce large noise and vibration

c Cold stamping processing methods

Cold stamping processing methods can be used to obtain workpieces with complex shapes and difficult to process with other processing methods, such as thin-shell parts. The dimensional accuracy of cold stamping parts is guaranteed by the mold, so the dimensions are stable and interchangeability is good.

d High material utilization rate

High material utilization rate, light workpiece, good rigidity, high strength, and low energy consumption in the stamping process. Therefore, the cost of the workpiece is lower.

e Simple operation

Simple operation, low labor intensity, easy to realize mechanization and automation, and high productivity.

f Mold Structure

The mold structure used in stamping processing is generally more complicated, the production cycle is longer, and the cost is higher.

Basic Requirements For Stamping Materials

The materials used for stamping must not only meet the technical requirements of product design, but also meet the requirements of the stamping process and the processing requirements after stamping (such as cutting, electroplating, welding, etc.). The basic requirements of stamping process for materials mainly include:

  • – Requirements for stamping performance: For the forming process, in order to facilitate the stamping deformation and the improvement of the quality of the parts, the material should have: good plasticity (high uniform elongation δb), small yield ratio (σs/σb), The plate thickness directivity coefficient is large, the plate plane directivity coefficient is small, and the ratio of the yield strength of the material to the elastic modulus  (σs /E) is small. For the separation process, the material does not need to have good plasticity, but it should have a certain degree of plasticity. The better the plasticity is, the more difficult it is to separate.
  • – Requirements for material thickness tolerance: The thickness tolerance of the material should conform to the national standard. Because a certain die gap is suitable for a certain thickness of material, the material thickness tolerance is too large, which not only directly affects the quality of the part, but may also cause damage to the die and punch.
  • – Requirements for surface quality The surface of the material should be smooth and smooth, free from delamination and mechanical damage, free from rust spots, oxide scales and other attachments. The material with good surface quality is not easy to break when punching, not easy to scratch the mold, and the surface quality of the workpiece is also good.

Commonly Used Materials For Stamping

The surface and unique properties of the stamped sheet have a great influence on the quality of the stamped product.
The requirements for stamping materials are as follows:

  1. Accurate and uniform thickness. The thinning of the metal plate affects the quality of the plate, increases the deforming force, clogs the material, and even destroys the mold. The finished product will break even if it is drawn.
  2. The surface is smooth, with no spots, no scratches, no scratches, no surface cracks. All surface defects remain on the surface of the finished part. Cracks occur during bending, deep drawing, and molding, which is wasted.
  3. Yield strength is uniform and there is no clear direction.
    Anisotropy (see plastic deformation of sheets during drawing, such as deep drawing, flange processing, bulging, etc.). Due to the appearance of anisotropic yield, the plastic deformations are inconsistent, causing non-uniform deformations and resulting in inaccurate defects or waste. )
  4. Uniformly high elongation. In the tensile test, the elongation before the initial necking phenomenon of the sample is called uniform elongation. During the deep drawing process, the deformation of any region of the sheet must not exceed the uniform elongation of the material, otherwise non-uniform deformation will occur.
  5. Low buckling ratio. The ratio of the yield limit to the strength limit of the material is called the yield ratio. A low yield ratio not only reduces deformation resistance, but also reduces wrinkles during deep drawing, reduces springback after bending, and improves the accuracy of curved parts.
    6, low work hardening. Work hardening after cold deformation increases resistance to deformation of the material, making it difficult to continue deformation, so low hardness index sheets are usually used. Materials with a high hardening index have good plastic deformation stability (ie, uniform plastic deformation) and are less susceptible to local cracks.

Most of the materials used for cold stamping are sheets, strips and blocks of various specifications. The size of the sheet is larger, and it is generally used for the stamping of large parts. For small and medium-sized parts, most of them are used after cutting the sheet into strips. Strip material  (also called coil material) has various specifications of width, and the unfolded length can reach tens of meters. It is suitable for automatic feeding of mass production. The material thickness can also be made into strip supply. Block materials are only used for stamping a few steel grades and expensive non-ferrous metals. 

Ferrous metal, ordinary carbon structural steel, high-quality carbon structural steel, alloy structural steel, carbon tool steel, stainless steel, electrical silicon steel, etc. 

For cold-rolled steel sheets, according to the national standard GB708-88, according to the rolling precision (steel thickness precision), it can be divided into A and B grades:  A──higher precision;  B──normal precision. 

For high-quality carbon structural steel cold-rolled thin steel sheets with a thickness of less than 4mm, according to the provisions of GB13237-91, the surface quality of the steel sheet can be divided into three groups: I, II, and III. According to the deep drawing level, it is divided into three levels: Z, S, and P:  

  • I ──Advanced finishing surface; 
  • II ──Higher grade finishing surface; 
  • III──Ordinary finishing surface. 
  • Z ──The deepest drawing level; 
  • S ──Deep drawing; 
  • P ──Ordinary deep drawing level. 

Non-ferrous metals  

Pure copper, brass, bronze, aluminum, etc. 

Non-metallic materials  

Cardboard, bakelite board, rubber board, plastic board, fiberboard and mica, etc. 

In the metal stamping process data and drawings, there are special regulations for the representation of materials. Take the marking of high-quality carbon structural steel cold-rolled sheet as an example. 

For example, 08 steel, size 1.0mm×1000mm×l500mm, ordinary precision, higher-level finishing surface, deep-drawn cold-rolled steel plate is expressed as: the steel plate belongs to the author. For commercial reprints, please contact the author for authorization, and for non-commercial reprints, please indicate the source. For the grades, specifications and performance of the materials, you can consult the relevant design materials and standards.


Metal Stamping Process Classification  

Stamping is mainly categorized by process and can be divided into two categories: separation process and forming process.

The separation process is also called punching. The purpose is to separate the parts punched out of the sheet along a particular contour, while ensuring the quality requirements of the separated parts.

The purpose of the forming process is to plastically deform the sheet without breaking the blank to produce workpieces of the desired shape and dimensions.

In actual production, multiple processes are typically applied to a single workpiece. Stamping, bending, shearing, stretching, inflating, spinning and straightening are several major stamping processes.

Separation process

Blanking separation process

This is a basic stamping process that uses a mold to separate the materials. Can be made directly on flat parts. Alternatively, prepare a blank for other stamping operations such as bending, deep drawing, and forming. It is also possible to cut and trim the formed stamping. Stamping is widely used in the fields of automotive, consumer electronics, electronics, instrumentation, machinery, railroads, telecommunications, chemistry, light industry, textiles, aerospace and other industries. The stamping process accounts for about 50% to 60% of the total stamping process.

Molding process

Bending: Metal sheets, tubes and profiles are bent by plastic molding methods of angle, curvature and shape. Bending is one of the main processes widely used in the manufacture of stamping. Bending of metallic materials is basically an elastic deformation process. After unloading, the workpiece elastically deforms in a recovery direction called rebound. The effect of springback on the accuracy of the workpiece is an important technique that must be considered during bending.

Deep stretch is also known as drawing or scrolling. After stamping with a die, the obtained flat blank becomes a method for punching a hollow portion. The stretching process can produce thin-walled portions of cylindrical, stepped, tapered, spherical, box-shaped and other irregular shapes.

Combined with other press forming processes, it can also produce parts with very complex shapes. Stamping production has many types of drawing parts.

Due to their different geometric properties, the position of the deformation zone, the nature of the deformation, the distribution of the deformation, and the stress states and distributions of the various parts of the blank have considerable differences, if not required. Therefore, process parameters, process quantities and sequence determination methods, and template design principles and methods are all different. Depending on the characteristics of the deformation mechanism, it can be classified into four types: straight wall rotating body (cylindrical part), straight wall non-rotating body (box body), curved rotating body (curved part), and curved non-rotating body.

In the pull type, the pull type applies a tensile force to the sheet, so that the sheet causes non-uniform tensile stress and tensile strain. Then, the mating surface of the sheet and the tension mold gradually expands until it completely fits the tension mold surface. The purpose of the pull type is primarily the specific plasticity of the material produced. The surface area is large and the curvature changes slowly. High quality double curved skin (correct shape, smooth rationalization, stable quality). Due to the use of process equipment and equipment, the pull shape is relatively simple, resulting in low cost and high flexibility, but low material utilization and productivity.

Roll forming

Spin forming is a metal rotation process. During the process, the blank is actively rotated on the flow forming die, or the spin forming head is actively rotated around the blank and the spin forming die. The spin forming head performs a feeding operation on the mandrel and the blank, and locally deforms the blank to obtain a desired hollow rotating member.

Molding is the use of a predetermined shape of a polishing tool to change the shape of a product. It mainly reflects on the pressure surface and bounces off the foot. For some materials, it is elastic and does not guarantee the quality of molding and reworking.

Flange processing is a plastic processing method in which a material in a narrow strip region of a preformed hole edge on the edge of a sheet blank or billet is bent into a vertical edge along a curve or straight line.
Flanging is primarily used to strengthen the edges of a part, cut the edges, and create parts that assemble and connect with other parts on the part.

Or have a three-dimensional part with a complex specific shape and reasonable space, while at the same time improving the rigidity of the part. It can also be used as a means of suppressing cracks and wrinkles when forming large sheet metal. Therefore, it is widely used in the automotive, aerospace, aerospace, electronics and consumer electronics industries.

Shrinkage is a stamping process that reduces the diameter of the open end of an unflanged hollow member or stretched blank.

Before and after shrinkage, the diameter of the edges of the work piece should not change significantly, otherwise the edge material will wrinkle due to the strong deformation caused by the compression.

Therefore, the size of the neck is reduced from a larger diameter reduction to requiring less multiple shrinkage.


Judgment of common defects in stamping parts, treatment methods and preventive measures

For the outer plate, the requirements are high and there must be no obvious defects. The inner plate is mainly free from cracks and dark cracks. For deep-drawn parts, first check whether the pressure point is clear, then check for dark cracks, and then touch it by hand , Push with Whetstone. 

Uneven

Judgment method: touch with hand, push with oil stone, see with eyes, recommended to push with oil stone, bright spots are raised and dark spots are sunken. 
Reason: If you find unevenness, check whether there are foreign objects such as sand particles in the mold,  
Solution: If there are sand particles, wipe the mold clean with mold-wiping paper 

Cracking (dark cracking) 

  • Judgment method: use eyes to check the corners of the drawn parts and other places where the material is deformed.should be turned over to check. 
  • Reason: It may be due to mold strain and large blank holder force. 
  • Solution: Check whether the workpiece is severely strained, and appropriately reduce the blank holder force. 

Wrinkle 

  • Judgment method: see with eyes 
  • Reason: small blank holder force 
  • Treatment method: appropriately increase the blank holder force. 

Glitch 

  • Judgment method: see with eyes 
  • Reason: The gap between the convex and concave molds is large. 
  • Solution: Modification 

Hole deviation 

  • Judgment method: check on the inspection tool and compare with the sample. 
  • Reason: The workpiece is not placed properly, and the mold positioning device is faulty. 
  • Solution: If the hole is still deviated after the workpiece is aligned, report to the monitor and notify the mold repair.  

Small holes 

  • Judgment method: compare with sample. 
  • Reason: The punch is broken. 
  • Solution: Immediately stop production and report to the monitor immediately to notify the mold repair.

Hole deformation 

  • Judgment method: look with your eyes. 
  • Reason: the punch is worn out. 
  • Handling method: slight oil pumping, severe oil pumping still deformed should be reported to the squad leader and notified to repair the mold. 

The deep drawing is not in place 

  • Judgment method: see whether the pressure point is clear. 
  • Reason: The main pressure is too small. 
  • Solution: Increase the main pressure appropriately. 

Poor hemming 

Judgment method: compare with sample  
Reason: The parts are not placed properly, the positioning device is faulty. 
Solution: Put the workpiece in place. If it is still not good, report it to the monitor and notify the mold repairer to repair the mold. 

Imprint 

  • Judgment method: see with eyes 
  • Reason: There are granular impurities adhered to the working surface of the upper mold of the mold. 
  • Solution: Wipe the upper mold of the mold clean. 

Strain 

Judgment method: see with eyes 
Reason: The working surface of the mold is worn and the mold hardness is not enough. 
Solution: Modification. 

Sand grains 

  • Judgment method: push with oilstone
  • Reason: The material or mold surface is not clean. 
  • Solution: Check the material or wipe the surface of the mold clean. 

Bumps, scratches 

  • Judgment method: see with eyes 
  • Reason: The incoming or outgoing material hits hard objects such as molds. 
  • Solution: Be careful when feeding and discharging materials, handle the product with care, and increase the closing height of the mold if necessary.

Attention Issue And Solution

Attention Issue

1.Mold Problem

Molds for stamping and machining are usually dedicated. Sometimes complex parts require the handling and molding of multiple sets of molds. The manufacturing accuracy of the mold is high, and the technical requirements are high. This is a technology-intensive product. Therefore, only when the production amount of stamping parts is large, the advantages of stamping can be fully exhibited and more economical benefits can be obtained.

2.Security Issues

There are also some issues and drawbacks to punching. Primarily in the stamping process, both noise and vibration are generated, causing occasional operator safety accidents. However, these problems are not due to the stamping process and the mold itself due to traditional stamping equipment and backward manual operation. With the development of science and technology, especially the development of computer technology, advances in mechatronics technology will solve these problems as soon as possible.

3.High Strength Steel Stamping

Today’s high-strength steels and ultra-high-strength steels have achieved very good weight savings and improved impact strength and safety. Therefore, they are an important development direction for steel products for automobiles. However, as the strength of the sheet increases, conventional cold stamping processes tend to crack during the forming process. It cannot meet the processing requirements for high-strength steel. Hot stamping forming technology for ultra-high strength steel sheets is gradually being studied internationally when the forming conditions cannot be satisfied. This technology is a new process that combines molding, heat transfer and microstructure conversion. By mainly utilizing the high temperature austenite state, the plasticity of the sheet is increased, the yield strength is decreased, and the molding process is performed in the mold. However, thermoforming requires detailed study of process conditions, metal phase transitions, and CAE analysis techniques. Currently, this technology is monopolized by foreign manufacturers, and domestic development is slow.
High strength steel stamping

Solution

Traditionally, in the manufacture of deep-drawn or reworked parts, pressure resistant (EP) lubricants have been considered the best choice for mold protection. Sulfur and chlorine EP additives are added to pure oil to extend the life of the mold. However, with the advent of new metals, high-strength steels and stringent environmental requirements, the value of EP-based lubricants has declined and has been lost.

In the formation of high temperature and high strength steels, EP oil-based lubricants lose their performance and do not provide a physical mold protection diaphragm in extreme temperature applications. Extremely hot IRMCO high solid polymer lubricants provide the necessary protection. As the metal deforms and rises in temperature within the stamping die, the EP oil-based lubricant becomes thinner and can reach a flash point or combustion (smoke). IRMCO’s water-based press lubricant sprays are usually started at low concentrations. As the temperature rises during the molding process, it becomes thicker and stronger. In fact, the extreme temperature lubricants of polymer polymers have “heat-seeking properties” that adhere to the metal to form a diaphragm that reduces friction. This protective barrier allows the workpiece to be stretched to prevent friction and metal flow without cracking or sticking during the molding of the most demanding parts. Effectively protects the mold, prolongs the life of the mold and improves stamping strength.


Top Metal Stamping Manufacturer From China

China PTJ Stamping Wordshop

Donggguan Pintejin Metal Products Limited is a definitive source and export-oriented company for custom metal stamping andOffice sheet metal parts services with ISO 9001:2015 quality system certification. We have been established in 2003 and located in Dongguan, manufacuring center of China with 1400sqm, We have success in continuous growth accompanied by our reliable commitment and on-time delivery to customers and our ability to supply our valued customers with the most excellent quality and cost-effective metal stamping and sheet metal fabrication services.

Pintejin is continuously upgrading machinery to catch up with customers’ demands of the precision and low cost stamping parts as well as training our employees at interval with the latest manufacturing technologies and quality control processes, Our experts and professionals are trained to handle the complexity of manufacturing for both long and short run stamping parts. Further, we offer value added service to your stampings, for example, TIG welding, Spot welding, MIG welding, Grinding, polishing, brushing, powder coating, painting, e-coating, plating, gift box packing, which make your metal stamping parts more durability and more elegant on appearance.

We manufacture an extensive range of quality metal stamping parts and sheet metal partstool shop for various market sectors worldwide including Household appliance, Automotive, Motorcycle, E-Bike, architecture, Lighting, Medical, Energy and Power transmission, Furniture and Electronic,IPTV set top box, DVD case, medical industries.

China Metal Fabrication Company

We use specialized and latest technology to bring china sheet metal fabrication with maximum benefits. We always try to satisfy as well as exceed your requirements and expectations. Metal Fabrication is the process that is involved in placing the sheet metal into the required shape with the help of the tool or the die surface. This manufacturing process can be made with the help of all the metal press and the stamping machines. Most China Metal Fabrication Companies use the metal stamping to shape the thin and flat sheet metal into the desired shape. Most of the companies will help with the metal stamping supplies which can bring more profit to the company.

Precision Metal Stamping

When the customer has requested for the low cost metal stamping but with the quick delivery then the manufacturing of the precision metal stamping could be the best choice as they can be easily manufactured with the quick labor and can be reliable and stable with the high quality. The application of the precision stamping is not limited to automobile, agriculture, electronics, lighting of LED, hardware and much more applications. This stamping process can be fully automated which can be produced at high quantity with good quality that too with the limited labor which is the added advantage of the metal.

Deep Drawn Stamping

Pintejin Metal Products Limited is the best Deep Drawn Stamping manufacturer and supplier in China. If you have an order that has complex design then the best choice of metal stamping will be the deep drawn stamping which can be used to produce the complex shapes at the faster rates. These complex shapes can be achieved only if the metals like aluminum, stainless steel, brass or copper are used. Only the metal that has the high flexibility is involved in this process as they need to produce the complex shapes of the products. Many sheet metal stamping types are available and they are chosen based on the shape and the size requested by the customer.

We focus on more personalized service to specific customers, which few companies nowadays care about any more. We combine traditional manufacturing and latest technologies together and bringing added value to every single stamping part we produce. Pintejin is your metal stamping partner of choice to help you maximize productivity and position your company for continuous success.

We can perform stamping, fine blanking, bending, NCT bending, progressive die stamping, deep drawn stamping, wireform, laser cut, TIG welding, grinding in house, which can meet your requests for different processings from one supplier. We are OEM metal stamping company who supply good quality metal stamping parts which are widely used as metal casing, metal case, metal stamped casing, metal housing, sheet metal casing, metal box, metal bracket, metal clip, metal clamp, metal plate, steel plate, nail stamping plate, the materials we used are iron, mild steel, carbon steel, stainless steel, aluminum, copper, galvanized steel, SECC, SPCC, etc. We involve in all stages of new projects from design, prototyping, short run production, mass production, share production knowledge with customers.

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