Custom Die Casting Manufacturer in China

What is Die-Casting

Custom Die casting is a special casting method that develops rapidly in modern metal processing technology. It is a process in which molten metal is injected into the mold at high pressure and speed, crystallizes, and solidifies under high pressure to form a casting.

The unification of speed, pressure, and time is the basis of this process. High pressure and high speed are the main characteristics of die casting. The use of die-casting has the advantages of high production efficiency, simple process, high casting tolerance level, low surface roughness, high mechanical strength, less chip, and so on, which saves a lot of processing equipment and raw materials.

The process is suitable for aluminum alloy, zinc alloy, magnesium alloy, copper, etc. It has become an important part of the foundry industry.

Using die casting has the advantages of high production efficiency, simple working procedure, high casting tolerance level, low surface roughness, high mechanical strength, less chip, etc. It saves a lot of processing and equipment, as well as raw materials. It has become an important part of the foundry industry.

Die-casting technology also has some disadvantages. For example, it is easy to produce small pores, the plastic of finished parts is low, and it is not suitable for working under impact load and vibration. When the melting point of the alloy is high, the die life will be reduced.

Die casting was first used in the automobile industry and instrument industry, and then gradually expanded to various industries, such as agricultural machinery, machine tool industry, electronics industry, national defense industry, computer, medical equipment, daily hardware, and other industries.

We not only pay attention to casting structure technology, advanced mold, die casting machine performance and excellent structure, die casting alloy selection adaptability, and smelting process standardization, but also pay attention to pressure, temperature, time, and other technological parameters on the casting quality of the important role. These parameters should be controlled effectively during the die-casting process.

There are three main elements of die casting machine, mold, and alloy.

Die-casting Machine

There are two main types of die casting machines, cold chamber die casting machine and hot chamber die casting machine. The hot chamber die casting machine has high automation, less material loss, and higher production efficiency than the cold chamber die casting machine.

However, due to the restriction of the heat resistance of the machine, it can only be used in the casting production of zinc alloy, magnesium alloy, and other low melting point materials. Aluminum alloy die castings are widely used today, due to its high melting point, it can only be produced on cold chamber die casting machine.

The die casting chamber is immersed in the liquid metal of the heat preservation melting crucible, and the injection parts are not directly connected to the machine base but are mounted on the crucible.

This kind of die casting machine has the advantage of simple production procedures and high efficiency. Less metal consumption, stable process. However, the pressure chamber and injection punch are immersed in liquid metal for a long time, which affects the service life.

It is also easy to increase the iron content of the alloy. At present, the hot chamber die-casting machine is mostly used for casting low melting point alloy castings such as zinc alloy, but it is also used for casting small aluminum and magnesium alloy castings.

The pressure chamber of the cold chamber die casting machine is separated from the holding furnace. During die-casting, liquid metal is taken out of the holding furnace and poured into the pressure chamber for die-casting.

Die-casting Mould

Depending on the die casting method, die casting mould is generally divided into high-pressure die casting and low-pressure casting.

The level of die casting mould mainly depends on the following aspects. The first is mould manufacturing accuracy; The second is the yield of die casting; Third, the production efficiency of the mould; Fourth, the reliability of mold production; Five is the service life of the mould.

1. For the manufacturing precision of the mold, we not only through advanced equipment but also from the other two aspects of research. One is to improve the level of processing equipment, the other is to improve the level of management. We believe that only with good equipment, if the management can not keep up, also can not make high precision mold. For example, tool wear, machine tool accuracy decline or produce changes and so on will affect the machining accuracy. In view of this, we must start from the management, such as the establishment of tool library, before the use of all testing, regular accuracy testing of the machine tool and so on, only pay attention to each link, to ensure the quality of processing, to ensure the quality of the mold.
2. To improve the yield of casting mold production, water drainage system to the influence of the casting yield is very big, but we believe that the mold temperature balance, namely is equally important to the layout of the mould cooling water, actually mold balance problems not only affect the mold die casting production yield, the production efficiency of mould is also crucial. The mold temperature field directly affects the product quality in the die-casting production, and only when the mold is cooled well, can it be guaranteed to adapt to the production of fully automatic die-casting, because under the condition of fully automatic production, it is impossible to adjust the mold temperature with manual spraying to meet the requirements of die-casting production. It is our key concern to increase the research on mold cooling and to increase the research on mold adapting to automatic die casting.
3. For the production efficiency of the mold, on the one hand, as the previous problem focuses on the mold cooling, reduce the use of spraying to solve the mold temperature balance, reduce the spraying time, reduce the casting cooling time on the mold, improve the production rhythm, improve the production efficiency of die casting; On the other hand, the focus is on the rapid dis-assembly of the mold, and reduce the time for mold maintenance, replacement of vulnerable parts.
4. The reliability of die casting is very important to die casting. Many die casting mould manufacturing enterprise in design, manufacturing mould from economic interests, often only small mould is often done, especially large die casting mold, mold under force is very big, and we are designed for a large-scale die-casting mold a strength is enough big, boards, generally choose forged steel P20 or 4140, and heat treatment, in the period of using, the mold die is absolutely reliable long life. Die casting mold is generally used cast iron or cast steel, often at the beginning of production without problems, after a period of use, the mold will appear a variety of problems, such as sliding block concessions, even appear mold cracking, cover plate cracking, mold reliability is poor, seriously affect the production of die casting. We are more from the mold structure, mold design and manufacturing technology and other aspects of continuous improvement, to ensure the improvement of the level of the mold, such as considering that the slider is easy to enter aluminum or debris, cleaning not clean will crush the mold, the use of advanced slider structure, to ensure the mold production safety and reliable.
5. Die-casting molds are often used for aluminum alloys, Magnesium alloys and zinc alloys have also become more popular in recent years. The general market to aluminum alloy mold 100,000 times life as a common requirement, magnesium alloy, and zinc alloy life will be higher. In order to improve the service life of the mold, on the one hand, we are learning from foreign enterprises, in the mold structure, mold strength and other aspects of strengthening, mold materials, heat treatment, surface treatment and other aspects of research and optimization. On the other hand, we have adopted advanced processing centers and the introduction of advanced processing technology, mold cavity hard processing, reduce the hard layer on the surface of the mold, greatly improve the life of the mould.

In addition, the factors that affect the life of die casting mold, except the performance of the steel mold itself, mold design, use environment, and other factors, maintenance is also very important.

At the end of each production, we will promptly remove the accumulated metal dust in the parting surface, cavity, core, sprue, overflow tank, exhaust duct, etc., to prevent the mold surface from collapsing, blocking the exhaust duct, or causing mold closure lax.

Do not use steel tools to contact the forming surface during mold cleaning. Spraying is one of the most important and difficult die-casting operations, which must be operated in strict accordance with the spraying process. Incorrect spraying can lead to unstable product quality and premature mold damage.

In addition, we will timely lubricate the sliding part according to the provisions, and also pay attention to the tightness of the mold at any time. We will often check the pressing condition of the mold platen and the support condition of the mold bracket, so as to prevent the mold from sinking or falling in use. Stop production after the completion of a mold repair cycle, or after the completion of the specified production batch, to retain the last die casting product, together with the mold repair.

Die-casting Alloy

Casting alloys are standardized according to the European standard EN1706 “cast aluminium and aluminium alloys”. The absolute values of properties in EN are based on independent test samples and show the minimum allowable values.

Only the minimum size of the sample is given. Samples must be cast under different casting conditions. Casting test samples shall be of the same position and size as the test method.

Data on die-casting and gold properties are used only as reference information because they depend heavily on the special way the samples are sampled and prepared for testing.DIN standards differ in these respects.

He gives a range of performance that includes possible differences, and his floor corresponds to the required minimum. In addition, it also gives the independent casting sample and the sample reference value from the casting.

To some extent, the results from the sample tests are less clear about the validity of the castings in the EN standard than in the DIN standard. They involve different problems in a wide range of micro-structure.

The casting method

S– sand mold casting

K – chilled

D – die casting

L– investment casting

Toughness and handling

O– tempering, the release of thermal stress

T1– control cooling and natural aging after casting

T4– heat treatment, quenching, and natural aging solid solution

T5– control cooling and artificial or over-aging after casting

T6– heat treatment, quenching and complete artificial aging of solid solution

T64- heat treatment, quenching, and partial artificial aging solid solution

T7– heat treatment, quenching and artificial over-aging solid solution (stable)

Common problems with aluminum alloy die casting

In the process of die casting, there are often some problems. We enumerate some common aluminum alloy die casting main defect characteristics, formation reasons, and prevention, remedial methods

1. Bubbling

The foaming of die castings mainly occurs in three situations: immediately after die casting; Bubbling after curium furnace; Foaming after surface treatment.

First, foam after die casting: this kind of situation is mainly due to mold exhaust, demulsifying agent dosage also has a little relationship.

The main reason for the poor exhaust of the mold is the volume of liquid metal liquid or the exhaust area is too small resulting in high pressure in the cavity. Our general solution is to open an overflow tank at the bubble to increase the exhaust area.

If problem, will increase the laundry pull ingredients exhaust structure, is to pull the bad material inside to a washboard exhaust device, make good filling material in improperness, Japanese companies to the most commonly used structure, but the site has its limitations, space increases the agency must be mold and will increase scrap ratio, the processing is not easy. So in general, we are to change the filling way of the flow channel, flow Angle to solve the bubbling of this kind of situation.

Second, bubbling after curium furnace: this kind of situation is mainly due to casting material porosity, our solution is also first in the bubble attachment with an overflow tank to obtain relatively dense tissue. If the problem is not resolved, extend the runner internal gate so that it is close to the defect.

Third, foaming after surface treatment: this kind of situation is relatively tricky, which may be caused by mold problem, post-processing process control problem, surface treatment problem, and material problem. Analyze and rule out one by one.

1. Mould problem: in addition to the two types of super classification, cold striations, cold striations, and cracks can also cause blistering. Our solution is to increase the mold temperature, increase the filling speed (note that too high filling speed will also cause porosity), and balance the ejection.
2. processing technology: to ensure that the work-piecein the process of handling can not scratch.
3. Material problem: strictly control the organization composition of incoming materials and ask the supplier to provide material certification. Increase the mixing ratio of new and old materials.
4. Surface treatment: take electroplating as an example, electroplating process includes: oil removal — cleaning — electricity to remove oil — cleaning — acid immersion — cleaning — electroplating — cleaning — drying, the whole process is also mobile, so the work-piece must not scratch. Generally speaking, to distinguish whether the foaming is caused by electroplating, we take a knife to pick up the bubbles if we can pick out a layer of skin, which is the problem of electroplating.
5. The chemical composition

The reasons leading to the unqualified chemical composition are generally incorrect calculation of ingredients, too little consideration of element burning loss, incorrect calculation of ingredients, inaccurate composition of raw materials and return charge or put into use without analysis, inaccurate weighing of ingredients;

Problems occur in feeding, less or more and missing materials, disordered storage of materials, mixing, melting operation is not in accordance with the process, temperature is too high or melting time is too long, chemical analysis is not accurate, etc.

For metals with severe oxidative burn loss, the upper limit of technical standards or the upper limit of empirical burn loss value shall be calculated in the batching; After batching and after nucleation. Before mass production, the material should be check whether weighing, chemical analysis, and spectral analysis are correct. Regularly calibrate the weighing device, and disable inaccurate ones.

The raw materials required for ingredients shall be stored separately marked and used in the order. Strengthen the storage of raw materials with clear labels and orderly storage. The alloy liquid shall not be overheated or the melting time shall be too long. After per-furnace analysis before use, the ingredients shall be adjusted immediately after unqualified analysis, and the burden shall be supplemented or diluted.

The proportion of melted sediment and secondary and above wastes mixed for use after re-refining shall not be too high. Finally, pay attention to the waste or use process, there are sand, lime, paint mixed.

1. Vortex hole

The vortex hole is a small hole in the casting or a large hole in the alloy fluid inlet. It can be seen in machining or X-ray.

The generation of vortex holes may have the following points:

1. The direction of the alloy liquid into the cavity is not correct, the cavity wall or core erosion, generating vortex, involving the air;
2. The injection speed is too fast, and the sprue is involved in the gas;
3. The inner gate is too thin and the movement speed of the alloy liquid is too high, resulting in spray and spatter, and blocking the exhaust slot too early;
4. The exhaust groove of the mold is not in the right position, or the outlet section is too small so that the exhaust capacity of the mold is poor, and the air cushion in the mold cavity is under high back pressure;
5. The cavity position in the mold is too deep, while the exhaust groove position is improper or too little;
6. The clearance between the punch and the pressure chamber is too small. When the punch returns too fast, a vacuum is formed. Or punch return too fast;
7. The pressure chamber has a large capacity and too little alloy liquid is poured.
8. Solution
9. Change the direction or position of the injection of alloy liquid into the cavity so that the alloy liquid first enters the deep and high part of the cavity or the broad part of the bottom, and press the air in the cavity into the exhaust slot. Before the alloy liquid fills the cavity, the exhaust slot cannot be blocked;
10. Adjust the shooting speed and fast pressure position, and shorten the two-speed distance as much as possible on the premise of filling;
11. Increase the inlet thickness of the inner gate under the condition that no spatters or jet is generated and the mold cavity can be filled;
12. Enhance the exhaust capacity of the cavity :(1) The position of the exhaust groove should be considered not to be blocked by the alloy liquid that enters first; (2) Add overflow groove, pay attention to the connection between overflow groove and work parts should not be too thick, otherwise prematurely blocked and surrounding porosity; (3) The parting surface is designed as a zigzag parting surface with the structure of insert block to solve the problem of difficult exhaust in-depth cavity; (4) Increase the cross-sectional area of the rear end of the exhaust groove. The general thickness of the front end is 0.05-0.2mm, and the rear end can be increased to 0.4mm.
13. According to the heat and exhaust conditions of each part of the casting, appropriate spray coating, after spraying water, dry water, avoid water is not dry mold: (1) Expand the gap between the punch and the pressure chamber to about 0.1mm, and extend the pressure holding time appropriately;(2) Adjust the position of the bottom punch of the vertical die casting machine, or increase the amount of alloy liquid injected in the room.
14. Shrinkage cavity and shrinkage porosity

Shrinkage cavity and shrinkage porosity refer to the holes in the casting that are dark gray and irregular in shape. Concentrated large holes are called shrinkage holes, while dispersed small holes in cellular tissue are called shrinkage holes. Inspection of appearance or X-ray findings before or after machining.

Shrinkage cavity and shrinkage may be because of alloy castings have no alloy liquid in the process of condensation caused by the feeding, or because the pouring temperature of liquid alloy is too high, the injection pressure is too small, it is also possible because the casting design structure is unreasonable, there are too severe thick big changes in thickness of section connecting parts or lugs, convex sets, etc.

Improve the casting structure, try to avoid the thick and large transfer parts or lugs, lugs, etc., where the thickness and thickness section change too drastically. If not, adopt a hollow structure or insert design, and increase the cooling of its position.

The pouring temperature of the alloy liquid can be lowered properly on the premise that the casting does not produce cold insulation and under-casting. Increase the supercharging pressure and increase the compaction. Grain refiners such as titanium (0.15 ~ 0.2%) were added to the alloy solution to reduce the tendency of shrinkage cavity formation.

Alloy varieties with small volume shrinkage and linear shrinkage should be used, or the alloy liquid should be adjusted to reduce the shrinkage of the alloy should be modified. Increase the cross-sectional area of internal casting to ensure casting solidification under pressure and prevent premature solidification of internal casting from affecting pressure transfer.

Die casting can also refer to gravity casting. Die casting is a manufacturing process in which molten metal is poured or forced into steel reusable molds. The non-ferrous alloy such as aluminum or zinc is melted in the furnace and then injected into die casting machine.

There are two main types of die casting machines – hot chamber machines (used for alloys with low melting temperatures, such as zinc) and cold chamber machines (used for alloys with high melting temperatures, such as aluminum).

Aluminum die casting alloys are lightweight and posses high dimensional stability for complex part geometries and thin walls. Aluminum has good corrosion resistance and mechanical properties with high thermal and electrical conductivity.

Advantage of Aluminum

• Rapid production
• Highly conductive
• Corrosion-resistant
• Lightweight and Durable
• Recyclable and Reusable in Production
• Defined, smooth and textured-surfaced metal parts

Advantage of Zinc

• Thinner wall sections
• Highly conductive
• Corrosion-resistant
• Thinner wall sections
• High production rates
• High dimensional accuracy
• Full recyclability
• High tensile strengths

Die Casting Process

Clamping

The initial stage is preparation and clamping of the two halves of the die. Step one is cleaning the residual metal from the previous injection and lubricating the tool to facilitate the injection of the next component. After lubricating, the two die parts are secured inside the die casting machine and then clamp together. The machine will apply sufficient pressure to keep the die secured during the injection.

Injection

To warm up the furnace at a set temperature, the machine will transfer the molten metal to the chamber and inject into the die. The pressures range is from 1000 to 20,000 psi. The machine will apply sufficient pressure to holds the molten metal during the solidification.

Cooling

The molten metal is injected into the die and begin to cool and solidify. After the entire cavity is filled and the molten metal solidifies, the final shape would be formed within a short time. The cooling time can be affected by the thermodynamic properties of the metal and the maximum wall thickness of the casting.

Ejection

After the predetermined cooling period elapses, the operator can open the two die halves and the ejection mechanism will push the casting out. The period time of opening the die is be determined by the dry cycle time of the machine and the size of the casting’s envelope. The ejection mechanism will apply adequate force to eject the part due to the shrinkage and adherence to the die after cooling. After ejection, the operator can clamp the die shut for the next injection.

Trimming

After the cooling period, the excess material and flash always come with parts due to injection with pressure. The workers will trim the excess material manually via cutting or sawing. The scrap material can be either discarded or can be recycled in the die casting process.