Die casting is a pressure casting process that can be very well used in industries that produce metal parts with complex designs. In addition to its compatibility with any product design, many metal parts manufacturers consider it for its ease of use, reduced material waste, and cost-effectiveness.
If you are looking for the right process for your die casting project, the question “How can I use die casting?” Therefore, this article explains the process, the machines used and their application in the manufacture of parts.
Die casting concept
Pressure casting (HPDC) is one of the three main types of pressure casting used in the production of metal parts. Regardless of the machine, the process involves injecting molten metal into a prefabricated mold under high pressure. Cooling follows, the molten metal solidifies and is removed from the mold. The cycle then continues.
Die casting is sometimes confused with low pressure die casting (LPDC), another type of die casting process. However, both methods have different advantages and disadvantages. Below you will find a summary of both procedures.
- HPDC uses a horizontally oriented machine
- HDPC machines, as the name suggests, inject molten metal under high pressure (1,000 to 25,000 PSI)
- LPDC machines have two die halves fixed to different machine plates
- Vertically arranged machines are used in low pressure casting
- LPDC machines, as the name suggests, inject molten metal at low pressure.
Die casting compatible materials
HPDC is only suitable for the production of metal parts. The most common materials are aluminum, zinc and magnesium. Below is a brief introduction to compatible materials so you know whether to stick with HPDC or use something else.
1. Aluminum
Aluminum is the most commonly used HPDC material – one of the reasons aluminum die casting is a popular manufacturing process in industries such as automotive and aerospace.
Due to its inherent properties, it is very common. Additionally, aluminum exhibits good fluidity when cast under high pressure, but requires a cold runner system for high-quality castings. Common aluminum alloys used in the process are 380, 390, 412, 443 and 518.
Aluminum HPDC parts are widely used in numerous industries due to their light weight, dimensional stability, electrical conductivity, corrosion resistance and heat resistance.
2. Magnesium
Magnesium is another popular HPDC material known for its light weight (lighter than aluminum) and high machinability. Their lower melting point makes them more suitable for hot chamber pressure casting. Common magnesium alloys you can use include AZ91D, AM60, AS41B, and AE42.
3. Zinc
Of the three common HPDC materials, zinc is the most manufacturer-friendly. It works best with a hot runner system, but is also suitable for a cold runner system. Common high pressure zinc die casting alloys include Zamak, 2, 3 and 5. Zinc die casting materials are strong, durable and machinable.
Other compatible materials include copper, lead, and tin alloys. Each of them has its unique properties. Therefore, you should check the required function and operating environment before choosing. Better yet, consult a pressure casting service that will carry out the process with the right material.
Components of a pressure casting machine
High pressure casting machines use two different systems: cold and hot chambers. Both systems use almost the same components with similar functions. For a manufacturer wanting an HPDC machine, below are some components of an HPDC machine and their features.
1. Die Casting Mold
This is the most important part of the machine, which is mainly made of steel due to its high precision, accuracy and tolerance. For example, it is manufactured using CNC machining processes. The design of the part corresponds to the intended product. Die casting molds consist of two halves (movable and fixed) that are attached to the machine. Both halves are held together under force while the operator injects molten metal.
2. Ejector pins
These components are used to eject the casting after solidification. They are usually located in the movable half of the mold.
3. Piston
The piston creates the pressure that injects molten metal from the blow chamber into the mold. Depending on the type of machine, this may be done automatically.
4. Heating components
The heating components are the heating element, thermocouple and blowing chamber (location of molten metal). They are used to heat the metal and store and maintain the temperature of the molten metal. There are no heating components in the cold room system.
5. Riser
It serves as a passage for the molten metal in the pressure casting mold.
How does the pressure casting process work?
Most die casting enthusiasts agree that HPDC consists of four processes: mold preparation, injection, ejection, and post-treatment. Below is everything you need to know about how the process works:
Step #1: Mold Preparation
Mold preparation includes cleaning the mold to remove contaminants that may affect the quality of the metal casting. It also includes lubrication of the inner walls of the mold to facilitate mold ejection and temperature regulation.
Step 2: Injection
In this step the molten metal is injected into the mold. However, the injection method depends on the machine's injection system. There are two systems: hot chamber and cold chamber. Below is an explanation of both methods.
Hot runner injection system
The hot chamber injection system is suitable for working with low melting point metals such as zinc, magnesium and lead. The metal part is melted in the machine and the molten metal is injected into the mold.
Cold chamber injection system
In cold chamber spraying, molten metal is poured into the blow chamber before being injected into the mold. The system is suitable for materials with a high melting point, such as aluminum and brass. Due to the high melting point of the material, it is necessary to melt it outside the system.
Below are some important conclusions about the two systems:
- The hot runner injection system is faster because the metal is additionally heated in the cold runner system.
- The hot runner uses a lower pressure (1,000 – 5,000 PSI) than the cold runner, which uses 1,500 to 25,000 psi.
- The cold runner system can use horizontal or vertical injection, while the hot runner system uses only horizontal injection.
- The hot runner injection system is suitable for producing small and complicated parts due to machine size limitations.
Step 3: Removing Parts
As it cools, the molten metal solidifies. The operator then uses the ejector pin to release the mold cavity and pushes out the solidified castings.
Step 4: Trim
Trimming is necessary to remove excess material from the casting and mold. There are many ways to cut off excess material. Typically this involves using a cutting tool and a saw. Excess material is reusable and recyclable. Therefore, the process is economical.
Advantages of pressure castings
Due to its advantages, pressure casting is widely used in industry. Below are some reasons why you should consider this procedure for your project:
1. Higher production rates
The injection phase is the most important phase of HPDC and is fast. Therefore, HPDC has a high production rate. Therefore, the process is important in rapid prototyping, especially in mass production. It is also faster than LPDC and other casting processes.
2. High quality die casting parts
Castings made with HPDC feature high dimensional accuracy, good surface finish and excellent uniformity. They also retain the mechanical properties of the base material and rarely require additional processing.
3. Thin-walled products
A thin wall thickness of less than 0.40 mm can be achieved through die casting. You can also add inserts (or co-molded parts) to reduce the number of components during assembly.
4. Get a complex design
HPDC is suitable for producing products with complex die shapes due to the flexibility in die shape design. Due to the flexibility, it is easier to assemble the manufactured parts.
5. Long-lasting matrices
The die casting molds used in the HPDC process are extremely durable and therefore suitable for multiple production cycles. Due to their longevity, unit costs of castings are reduced.
When should you not consider die castings?
Although HPDC offers unique advantages, there are two situations where it is not ideal. If you fall into this category, you should definitely talk to a rapid prototyping company about possible manufacturing processes. Here you can discover the advantages and disadvantages of pressure casting.
Presence of air
HPDC is not the appropriate material for products that cannot have air pockets. Due to the high pressure, air pockets may occur in the mold during the injection phase. This results in porosity and such parts should not be subjected to heat treatment as this may cause blistering on the surface. If you still think that die casting is the right method, you can switch to die casting.
Initial startup costs
Setting up your own HPDC machine requires a large investment. One of the reasons why many people and companies consider outsourcing to a die casting service provider.
Application of the pressure casting process
HPDC has broad industrial capabilities and is therefore used in the following industries:
1. Automotive industry
The automotive industry uses HPDC to produce engine blocks, transmission cases, engine mounts and other structural vehicle parts. These parts have a complex design and require high precision. They are also suitable due to their compatibility with materials such as aluminum and magnesium.
2. Medical industry
Medical parts such as high-production imaging devices and infusion pumps are manufactured on HPDC machines. This is the preferred process due to its productivity, material compatibility, and need for compatibility with complex product designs.
3. Aerospace industry
The aerospace industry also uses HPDC to manufacture products such as engine parts. High pressure casting processes for zinc, magnesium and aluminum are common here due to their properties.
Should I outsource or buy a die casting machine?
The decision between outsourcing and purchasing an HPDC machine depends on your company, the size of the project and your investment options.
Small and medium-sized businesses should outsource die casting services regardless of the size of their project. For large companies, the desire to maximize profits will dictate their choice, as HPDC has high start-up, maintenance and operating costs.
Concluding
Pressure casting is a common manufacturing process in industries that use solid metal parts with complex designs. Offers ease of use, less material waste and cost efficiency. This article dealt with the process and its application in the production of parts. Do you need high-quality metal parts manufactured using a die casting process? We'll help you get started.
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Common questions
Why do you use CNC machining for die casting molds?
Due to its precision, accuracy and high tolerance, CNC machining is the most widely used method for mold production. Form requires a process that can provide a lot of detail. Therefore, CNC machining is a common method for producing die casting molds.
Is pressure casting suitable for plastics?
No, for plastic polymers you must use injection molding. Die casting is the injection molding of metals.
What is the difference between high pressure casting and gravity casting?
High pressure casting is a type of die casting process, which means it is injected under pressure. Gravity casting, on the other hand, involves filling the mold with molten metal under the influence of gravity.
