Factors influencing the dimensional accuracy of metal stamping parts

Different metal stamping products have different requirements for accuracy. As long as we meet the accuracy requirements of customers and comprehensively consider production costs, we can produce qualified stamping parts. The factors that affect the dimensional accuracy of metal stampings must be known by everyone. Let’s have a look together.The dimensional accuracy of metal stamping parts refers to the difference between the actual size of stamping parts and the basic size. The smaller the difference, the higher the dimensional accuracy of metal stamping parts.

The influencing factors are as follows:

1. Manufacturing precision of metal stamping die.

2. Gap between male and female dies.

3. Elastic recovery of materials after stamping.

4. Accidental factors in the production process, such as inaccurate positioning, unstable material performance, etc.

It can be divided into precision level and ordinary level. The ordinary level is the precision that can be achieved by more economic means, while the precision level is the precision that can be achieved by stamping technology.

The surface quality of metal stampings shall not be higher than that of raw materials, otherwise, subsequent processing is required to achieve it, increasing production costs.

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What are the application scope of metal stamping products?

1. Application scope of metal stamping products

1. Stamping parts for daily necessities: mainly to do some handicrafts, such as tableware, kitchen utensils, faucets and other daily hardware.

2. Electrical device stamping: The electrical stamping factory is a new industry developed with the development of electrical appliances. Such manufacturers are mainly concentrated in the South.

3. Stamping in the automotive industry: For example, the body, frame, rim and other parts are stamped. Mainly deep drawing, mainly concentrated in automobile factories, tractor factories, aircraft factories and other large factories.

4. Stamping in the medical industry: It is necessary to assemble various precision medical devices, and the stamping in the medical industry develops rapidly.

5. Special stamping enterprises. For example, the stamping of aerospace components belongs to this category, but these process plants also belong to some large factories.

Metal stamping parts have the advantages of simple operation, easy automation, and accelerated production efficiency. They are widely used in many industries and play an indispensable role.

Large size and dimensional accuracy of automotive stamping parts

1. Large pieces and dimensional accuracy of automotive stamping parts

Automobile stamping parts are divided into many types, and the steel plates used for different types of parts are also different.

For some sealing plates, brackets and the like that do not require very high performance and the shape is not complicated, it is easy to use steel plates with general tensile properties for a long time.

Due to strict appearance requirements, large outer covering parts inevitably use specially required steel plates.

Some shapes are more complex, and some are deep shapes or steel plates with relatively sharp changes that do not require good tensile properties.

The dimensional accuracy of metal stamping parts can be generally divided into two categories: precision grade and ordinary grade. The precision grade is the precision that can be achieved by the stamping process, and the ordinary grade is the precision that can be achieved by economical means. When the machining accuracy of the mold is high, the shape and dimensional accuracy of the metal stamping parts can reach the ITl0 level, and the inner hole size can reach the IT9 level.

The surface quality of metal stamping parts should not be higher than the surface quality of raw materials, otherwise it needs to increase the follow-up processing to achieve, but also increase the cost of production.

The dimensional accuracy of metal stamping parts refers to the difference between the actual size and the basic size of the stamping parts. The smaller the difference, the higher the dimensional accuracy of the metal stamping parts. The main factors that lead to the size error of metal stamping parts are: the manufacturing accuracy of convex and concave molds, the gap between convex and concave molds, the elastic recovery of materials after stamping, inaccurate positioning, and unstable material properties.  

Design specification for stamping die forming parts

1. The design of forming parts includes the following four aspects:

1. First of all, it is necessary to consider determining the parting surface of the movable and fixed molds. During the injection molding process, the surface that opens the mold for taking out the plastic part or the gating system is collectively called the parting surface. That is to say, the parting surface is the contact surface between the movable mold and the fixed mold, and its main function is to tightly seal the cavity. The mold designer must determine the opening direction of the mold when designing the parting surface.

2. When designing molding parts, it is necessary to consider the number of cavities and the layout of the cavities, the setting of the pouring system, the core pulling mechanism, the demolding mechanism, the design of the temperature control system, the material selection and heat treatment of the molding parts, etc. See other chapter.

3. Whether the structural form of the movable die and the fixed die is a whole or a block structure, and its structural form and size, block method, fixing method, etc., it is necessary to calculate the cost according to the specific situation, weigh the pros and cons to make the correct choose. The strength and rigidity of the mold should be paid attention to when adopting the combined block structure, see Chapter 16 for details.

4. When designing the size of the molded parts, the molding shrinkage rate of the product, the demoulding slope, and the manufacturing process of the parts should be fully considered.

5. Design molding parts according to the customer’s design standards and requirements and the technical data provided.

Second, the basic principles of mold structure design

1. Make it clear

The mold structure principle is clear, the function of the parts is clear, and there is no omission and repetition. The design of each part is required to be standardized and optimized (the design basis should be unified, the nominal size should be an integer, and it cannot be arbitrarily designed).

2. Simple

The structure is simple and reliable, easy to process and assemble, and the advantage of simplicity is that the cost is directly reduced. For example, try to keep the geometry of the parts simple, minimize the machining surface and processing times of the parts, reduce or simplify the assembly relationship and adjustment measures with the related parts (the related parts must not interfere).

3. Safe and reliable

The mold has sufficient strength and rigidity, and the continuous operation of the mold will not cause problems, which is convenient for mold maintenance

4. Maintenance

The product ejection and demolding mechanism is safe and reliable.

The molding efficiency of the products is high and the quality is good. Such as: high cooling rate, short molding cycle, and balanced pressure in the gating system. The designed mold, after the plastic part is formed, its runner and gate are easy to remove.

3. Design steps of forming parts

When designing the molding parts of movable and fixed molds, it is necessary to comprehensively consider related issues. After determining the mold structure and gating system, the design can generally be carried out according to the following steps.

1. Determine the number of mold cavities and preliminarily determine the cavity layout.

2. Determine the parting line of the plastic part and the parting surface of the mold.

3. Determine the gate form and feeding position of the gating system.

4. If there are concave and convex shapes inside and outside the plastic parts, it is necessary to design a lateral core pulling mechanism.

5. Determine whether the molded part is integral or insert, and its combination and structural fixing.

6. After the above relevant factors are determined, it is necessary to comprehensively consider the mold structure and overall layout.

7. Determine the inner and outer shape and molding size of the core and cavity, and determine the demoulding slope of the part.

8. Determine the technical requirements for the material, heat treatment, assembly requirements, surface roughness and other technical requirements of the movable and fixed mold forming parts.

Fourth, the method of determining the number of cavities

There are many ways to determine the number of cavities. The design is mainly based on the precision of plastic parts, the batch of products, the economy of production, the clamping force of the injection molding machine and the injection volume. The first is the accuracy of the plastic parts, and then other factors are considered, and the number of cavities is required to be reasonably selected. Usually, the number of cavities with high precision is at most 4, and for the number of mold cavities with low precision, it is best not to exceed 24. Because, every time the number of cavities increases, the accuracy will decrease accordingly.

Deep Drawing & Metal Fabrication

China Aluminum Company is a leading manufacturer of deep drawn parts, including cylinders, enclosures and irregular shapes. We maintain a vertically-integrated facility with on-site engineering, designing, and prototyping services. Over the last 20 years, we’ve earned a reputation for producing highly complex, yet cost-effective, deep drawn parts.

Metal Stamping Prevent Hidden Dangers

Metal stamping is dangerous, but it is not really dangerous. It complies with the stamping system and operates properly. Stamping is still very safe. During the Metal Stamping process, for safety reasons, pay attention to the adjustment screw of the slider, and do not let it extend too long. In the Metal Stamping process, in order to prevent the mold from moving, a layer of paper can be applied to the reinforcement, and the Stamping Mould is a dangerous situation. For the safety of metal stamping parts processing, disassemble the mold and wait until the machine is completely stopped. Metal Stamping processing, if you need to adjust and install the mold, you must first turn off the power into action. Although this can be done without turning off the power, the risk index will be greatly increased, so in order to be safe, the power must be completely turned off. Operate after stopping operation. In Metal Stamping processing, the presence of fastening screws will guarantee the safety of metal stamping parts processing. In order to ensure that this protection is not a hidden danger, it is necessary to tighten the fastening screws frequently to ensure that the fastening screws can have safety features.

How Can Metal Stamping Use in The Medical

With the rapid development of the medical technology sector, medical equipment is crucial to the modern medical care industry. Manufacturers are facing the challenge of rising medical costs because prices are rising almost as fast as technology adaptation. To solve this problem, many professionals have begun to see metal stamping as a fast, consistent and more cost-effective solution.
In this case, high-precision metal stamping technology has become the preferred alternative for machining in medical applications. Today, metal stamping manufacturers can provide many micro and small metal parts, which are needed by the medical industry. Precision metal stamping has been widely used on many medical devices. It has become an important trend for the rapid development of the stamping industry in the future.

What are the common problems in the production of stamping and drawing parts?

1. The reason for the instability and wrinkling of the flange of the stretched part: the blank holder force is too small, or the relative thickness of the blank is small, or the tensile coefficient is too small.

Solution: Increase the blank holder force or increase the number of stretches.

2. Reasons for surface strain of stamping and drawing parts: low heat treatment hardness, poor finish, improper material selection, excessive material thickness, wear of concave die fillet, poor surface quality of bending blank, unreasonable selection of process plan, insufficient lubrication, etc.

Solution: For stamping parts that need to be stretched many times, under the premise of ensuring the necessary appearance quality, there are traces that can occur during the stretching process. Choose suitable materials and process solutions, lubricate and reduce friction.

3. Reasons for the inconsistent shape and size of stamping and drawing parts: due to inaccurate positioning, in addition to taking measures to reduce springback, the reliability of blank positioning should also be improved.

Solution: The shape of stamping and drawing should be as simple and symmetrical as possible, and one-time stretching should be done as much as possible.

4. The reason for the cracking of the hole after the stretching of the tensile member with the hole: the hole diameter is too large, so that the material around the hole is subjected to a large tensile stress, which leads to fracture.

Solution: Change the sequence of forming process, stretch and form first, and then punch holes at the bottom.

5. The reason for the instability and wrinkling of the upper edge of the cylindrical drawing part: the radius of the concave die fillet is too large, which causes the gap between the concave die and the punch die to be too large, or the blank holder force is too small.

Solution: increase the blank holder force and reduce the radius of the die fillet.

In the drawing process, the cylindrical drawing part is a common metal drawing part, which is widely used. Some customers have special requirements for stretched parts, such as flanging, etc., which can meet the special requirements of the product. Drawing parts processing plants need to fully understand the knowledge of drawing parts flanging processing.

Cylindrical stretching parts with flanging include narrow flanging, cylindrical stretching parts and wide flanging cylindrical stretching parts; narrow flanging cylindrical punching and stretching parts are stretching parts with a small total flange width . When this type of parts is stretched many times, due to the narrow flanging, it can be stretched by punching the flanging cylinder first, and then the flanging process is performed to form the specified narrow flanging shape.

In order to make the flanging better, the conical concave die and the conical pressing ring can be selected for stretching in the last two processes of drawing, and the conical flanging can be vacated, so that the flanging area can be reduced when the part is formed. Radial tensile deformation is beneficial to avoid edge cracking.

When the wide-flanged cylindrical stretched piece needs to be stretched multiple times, for the first stretch, make sure that the flanging specification is equivalent to the flanging specification of the stretched piece. In the next stretching, the flanging specification No change, only the raw material in a certain part of the cylinder migrates to the stretch specification. Because in the subsequent stretching process, even a small deformation caused by a part of the flanging will cause a very large tensile stress in the force transmission area of ​​the cylinder wall, thereby causing the bottom section to crack.

What are the positioning benchmarks for stamping processing?

1. Principles of selection of fine benchmarks

1. The principle of datum coincidence: The design datum of the machined surface should be selected as the precise datum as much as possible, which can avoid the positioning error caused by the misalignment of the datum.

2. The principle of mutual reference: when the positional accuracy between the two machined surfaces on the workpiece is relatively high, the method of repeated machining of the two machined surfaces as a reference to each other can be used.

3. Self-base principle: some surface finishing processes require small and uniform machining allowances, and the machined surface itself is often used as the fine base.

4. Unified datum principle: as many surfaces as possible on the workpiece should be machined with the same set of fine datums as much as possible to ensure the relative positional accuracy between the machined surfaces.

The above four principles for selecting rough benchmarks can sometimes not be taken into account at the same time, so the main decision should be made.

2. Principles of selection of rough benchmarks

1. A rough benchmark should be used in one process of workpiece processing. Whether the rough benchmark is selected correctly or not is not only related to the processing of the first process, but also has a significant impact on the entire process of workpiece processing.

2. The principle of rationally allocating machining allowances: Considering ensuring that the machining allowances of important surfaces are uniform, important surfaces should be selected as rough benchmarks.

3. The principle that rough benchmarks should not be reused in general.

4. The principle of easy clamping: In order to stabilize the positioning of the workpiece and the clamping is reliable, the selected rough datum is required to be as smooth and clean as possible. Forging flashes, pouring riser cuts or other defects are not allowed, and there must be enough support area.

What are the key conditions in the forming process of stamping parts?

In fact, the so-called performance is mainly worth the forming limit, moldability and shape freezing of stamping parts. Among them, the forming limit mainly refers to the maximum deformation degree of the raw material of the stamping part during the forming process, and on the premise of ensuring no cracking. In many cases, we consider the forming limit to be the fracture resistance of the material, that is, the better the fracture resistance of the stamped material, the higher the forming limit.

And mold fit and shape freezing refers to the ability of the material to obtain the shape of the mold during the stamping process and to obtain the shape in the mold. There are many influencing factors. Pay attention to all aspects and try to avoid the influence of the material properties by the impression concept stock, so that the shape error of the stamping parts is large.

The above is the key point in the forming process of stamping parts introduced by Zhejiang Baifudu Electromechanical Editor and everyone. Do you have more understanding of stamping parts after reading it? I hope that my friends can help you after reading the above content.

Metal Spring Clip

Metal spring clips are usually made of stainless steel or manganese alloy after heat treatment and are important parts of electronic switches. The spring clamp plays an important role in the high-quality switch between the operator and the product. At the same time, stable toughness and long life performance will provide good tactile feedback for the operator.

Material Science

Generally, copper, carbon steel, stainless steel, manganese and other materials are used to manufacture metal spring clips. Factors such as heat resistance, quenching, corrosion resistance, fatigue strength and elastic limit should be considered comprehensively.

features

Metal spring clip is mainly used to control the movement of machinery, store and output energy, absorb vibration and impact energy, and is also a force measuring element.

application

Metal spring clips have been widely used in various fields, especially in the mechanical and electrical industry, mainly in electronics, electrical appliances, advertising, IT, communications, automobiles, buildings, furniture, bags, craft gifts, sports equipment, clothing, outdoor, etc.

What are the design and material requirements for precision stamping parts?

Precision stamping and ordinary stamping are completely different. The minimum value of the hole diameter and hole margin of precision stamping parts is smaller than that of ordinary stamping. Therefore, when designing precision stamping parts, there are certain requirements for the design of the structure.

When designing the structure of precision stamping parts, the shape of the workpiece and the inner hole should be rounded, and sharp corners are not allowed. However, the minimum allowable corner radius value is related to the material thickness. The punching diameter, slot width and edge distance of the workpiece should not be too small. When precision stamping gears, the pitch circle tooth width of the gear should not be less than 0.6T, and the top and root of the tooth shape should be a rounded transition, not a sharp transition. The contour shape of the outer edge of precision stamping parts should be as smooth as possible, and should not change suddenly. On the surface of the workpiece, design symbols or marks, and when pressing, the cutting depth should not exceed 0.25T.

In general, the production of precision stamped workpieces is mainly based on strong blanking and fine blanking. The geometry, dimensional tolerances, geometric tolerances and shear surface quality of fine blanked workpieces are much higher than those of ordinary blanked workpieces.

The most commonly used materials in the production of precision stampings are metallic materials (including ferrous and non-ferrous metals), but sometimes non-metallic materials are also used.

Among them, ferrous metals mainly include ordinary carbon structural steel, high-quality carbon structural steel, alloy structural steel, carbon tool steel, stainless steel, electrical silicon steel, etc.; non-ferrous metals mainly include pure copper, brass, bronze, aluminum, etc.; there are many Metal materials and models. How can we choose materials, not only to ensure the quality of the workpiece, but also save materials?

When manufacturers of precision stamping parts choose stamping materials for drawing parts, they generally have the following principles:

Metal materials must meet the performance requirements of the workpiece; stamping parts work normally in machines or parts and have a certain service life.

The selected material must have good process performance; for any kind of stamping part, the selected material should be able to meet the requirements of the stamping process.

The selected material should have good economy; under the premise of meeting the performance and stamping process requirements, the material should be low in price, convenient in source and economical to reduce the cost of stamping parts.

The above are the principles that manufacturers of precision metal stamping parts should follow when choosing metal stamping materials. Hope the above content is helpful to readers.

Common Defects and Preventive Measures of Stainless Steel Drawing Die

The selection of suitable convex and concave die fillets for stainless steel wire drawing is closely related to the size and distribution of stress. If the radius of the fillet is large, the pressing area of ​​the blank holder is insufficient, which will easily cause instability and wrinkling; if the fillet is too small, it increases the resistance of the material entering the die during deformation, making it difficult for the material to flow and transfer inward, thereby increasing the force transmission. area, which may cause cracking. Therefore, it is very important to choose a reasonable punch and concave die fillet radius. Under the effect of preventing cracks, the punch relative to the fillet radius rp/ is about 4. The degree of polar deformation of the die and punch will increase, and the relative fillet radius of the die will increase by 5mm~8mm, which helps prevent cracking.

4. Thin strip stretching is used for stainless steel stretching: previous testers have also confirmed that the thin strip stretching method can significantly reduce the maximum tangential residual stress of the stretched parts and effectively prevent longitudinal cracking. According to the degree of deformation and the thickness of the original plate, an appropriate thinning coefficient (usually 0.9t~0.95t) is selected. If the value is too small, the deformation stress of the deep-drawing part will increase sharply, resulting in the bottom cracking.

5. An intermediate annealing process is added to the deep drawing method for stainless steel drawing: after multiple deep drawing, an intermediate annealing process should be carried out, which can completely eliminate residual stress and restore the austenitic stainless steel structure. For high-strength steels, it is generally necessary to go through 1 to 2 stretching processes before moderate annealing. For example, 1Crl8Ni9Ti is usually heated at 1150~1170℃, heated for 30min, and then cooled in airflow or water. Moreover, whether it is the heat treatment between processes or the final heat treatment of the finished product, it should be carried out as soon as possible after stretching to avoid deformation or cracking of the workpiece due to internal stress due to long-term storage. However, both annealing and post-cleaning annealing increase product cycle time, which affects surface quality.

6. Use suitable lubricants for stainless steel drawing: using suitable lubricants has a significant effect on stainless steel deep drawing. The lubricant can form a film with certain toughness and ductility between the convex and concave dies, which is beneficial to the stretch forming of stainless steel. Due to the large deformation of stainless steel deep-drawing parts and the difficulty of forming, polyvinyl fluoride film can be used as a lubricant in actual production. PTFE membrane has good tear resistance, certain toughness and ductility, and is easy to clean. After coating the dry film, in the stretching process, the dry film can be deformed together with the blank, and can always separate the blank from the mold, and the film itself has a certain porosity and a large number of fiber cracks, so it can be stored in a certain amount. of lubricating oil.

The above-mentioned common defects and preventive measures of stainless steel drawing die, in the actual production process, the drawing die is prone to strain, and to solve this problem, the adhesive wear should be reduced by changing the characteristics of the contact pair. I hope the above can be helpful to readers.