Innovation in part manufacturing industries that use metals many times leads to products with complex designs made from different materials. This further necessitates the popularity of high pressure die casting.
High pressure die casting is a process considered by many manufacturers due to its speed and lesser material wastage compared to other die casting processes. However, choosing it must be done after you understand it. Hence this article discusses all you need to know about the process.
What is High Pressure Die Casting?
High pressure die casting (HPDC) is a pressure die casting process most enthusiasts call the die casting process.
The manufacturing process makes use of a die casting machine which has components that function together in injecting molten metals like aluminum and zinc into a pre-designed mold under high pressure. On cooling, solidification occurs, the die casting part is removed from the mold, and the cycle continues.
The component of a die casting machine depends on the injection system (i.e., cold, or hot chamber). Nevertheless, both types of machines use nearly the same components introduced below with their functions.
Die cast mold
The mold is made using materials such as steel due to its high melting point using CNC machining and is where the molten metal is injected. It has a design model after the desired product and is divided into two halves, one movable and the other fixed to the die casting machine. During the injection process, the machine clamps both halves together to prevent spilling of the molten metal.
Ejector pins
The ejector pins are most times on the movable half of the die-cast mold. They function in ejecting the part after the casting solidifies.
Piston
The piston functions in generating the pressure to inject the liquid metal into the die cast mold. It can be semi-automated, manual, or automated depending on the sophistication of the die casting machine.
Heating components
Heating components function in storing and maintaining the temperature of the molten metal. They include the heating element, thermocouple, and blow chamber. They are only found in hot chamber die casting machines.
Riser tube
This component acts as a passageway which the molten metal takes into the die-cast mold.
Types of High Pressure Die Casting
High-pressure die casting has two types: cold chamber and hot chamber depending on the method of the machine’s injection system.
Hot Chamber Injection System
Hot chamber die casting is suitable for materials such as magnesium, aluminum, and lead. In the injection system, the melting process takes place in the machine before injection into the mold occurs.
Cold Chamber Injection
In a cold chamber die casting, melting occurs outside the die casting machine before pouring into a blow chamber using a metal ladle before being injected into the mold. A cold chamber die casting system is suitable for materials with high melting points such as aluminum.
A summary of the differences between the two types of high pressure die casting include:
- A hot chamber injection system is faster since it does not have the extra step of melting the metal outside the machine
- The cold chamber uses more pressure (1500 to 25000 psi) than the hot chamber (1,000 – 5,000 PSI)
- A hot chamber uses a horizontal injection process while a cold chamber system uses both horizontal or vertical injection
- A hot chamber injection system is better suited for small and intricate parts due to the machine’s size.
How Does High Pressure Die Casting Process Work?
According to many enthusiasts, the die casting model comprises four major processes. This section of the guide will show you everything you need to know about how the process works:
Mold Design and Preparation
The mold is manufactured using CNC machining as it can achieve the tight tolerance, accuracy, and precision needed. Afterward, the operator cleans the mold to remove impurities as they can affect the final part’s quality. You should also lubricate the interior wall of the mold to regulate temperature and improve part ejection.
Molten Metal Preparation and Injection
This depends on the die-casting machine’s injection system as previously explained in the hot chamber vs cold chamber injection system. For the cold chamber injection system, you need to prepare the molten metal soup outside the machine. Afterward, injection occurs based on the injection system.
Cooling and Solidification
The molten metal cools and solidifies. Afterwards, solidified die casting parts are released from the mold cavity using the ejector pin.
Post casting process
Die casting parts also undergo several post-casting procedures such as trimming to remove extra materials found on them. Trimming commonly occurs using a trim die and saw. Furthermore, the extra materials on the parts are reusable and recyclable which makes it cost-effective.
Common Materials Compatible with High Pressure Die Casting
HPDC is the most common type of die casting process in the manufacturing world with the most common materials being aluminum, zinc, and magnesium. Each one has its properties introduced below and you can know about them to know whether you should stick with the HPDC or use another.
Aluminum
Aluminum is the most versatile die casting material in part manufacturing industries like automotive and aerospace. The aluminum die casting process is popular due to properties like high strength-to-weight ratio, corrosion resistance, thermal resistance, and good flow on melting in making high-quality die casting parts.
There are several aluminum alloys used in the die casting process each with unique properties. The table below shows a summary of the alloys, the elemental composition, properties, industry, and the die casting parts.
| Alloys | Elemental composition | Properties |
| ADC1 | Aluminum, Silicon (11-13%), Iron (0.9Max), Copper (1.0max), Manganese (0.3Max), Magnesium (0.3Max), and Nickel, Zinc, and Tin in trace amounts | Low tensile strength and yield strength, corrosion resistance, dimensional stability, and machinability, |
| ADC3 (A360) | Aluminum, Silicon (9.0-11.0), Iron (0.9Max), Copper (0.6max), Manganese (0.3Max), Magnesium (0.4 – 0.6), and Nickel, Zinc, and Tin in trace amounts | High yield strength, corrosion resistance, dimensional stability, and machinability |
| ADC6 | Aluminum, Silicon (1.00%), Iron (1.10% max), Copper (0.2% max), Manganese (0.4-0.6%), Magnesium (2.6-4.0%), and Nickel, Zinc, and Tin in trace amounts | Corrosion resistance, dimensional stability, and machinability |
| ADC10 | Aluminum, Silicon (7.5-9.5%), Iron (0.9% max), Copper (2.0 – 4.0%), Manganese (0.5% max), Magnesium (0.3% max), and Nickel, Zinc, and Tin in trace amounts | High strength, corrosion resistance, dimensional stability, and machinability |
| ADC12 | Aluminum, Silicon (9.6-12%), Iron (0.9Max), Copper (1.5-3.5%), Manganese (0.5% max), Magnesium (0.3% max), and Nickel, Zinc, and Tin in trace amounts | High tensile strength, yield strength, and better fluidity |
Other aluminum alloys compatible with the die casting process include B390, AC43500, and A413. Choosing the right aluminum material depends on the specific requirement. Many die casting manufacturers use ADC12, due to its cost-effectiveness, good mechanical properties, and dimensional stability.
Magnesium Alloys
Magnesium is popular among die-casting services due to its lightweight (it is lighter than aluminum) and machinability. The material is die-casted using the hot chamber die casting process due to its low melting point. Common magnesium die casting alloys are:
| Alloys | Elemental composition | Properties | ||
| AZ91D | Magnesium (90%), Aluminum (8.3 – 9.7%), Zinc (0.35 – 1%), Manganese (≥ 0.13%), Silicon (≤ 0.10%) | High strength-to-weight ratio, good corrosion resistance, excellent castability | ||
| AM60 | Aluminum, (5.5-6.5%), Manganese (0.24-0.6%), Zinc (0.22%), Silicon (0.1%), Magnesium (others). It also contains other trace elements like iron and copper. | Balanced strength and ductility. Good castability and weldability, corrosion resistance, | ||
| AS41B | Magnesium (94.6%), Aluminum (3.5-5%), Silicon (0.5-1.5%), Manganese (≥0.35%), and other trace elements | Good castability and fluidity, intricate and thin-walled castings, corrosion resistance | ||
| AE42 | Magnesium (93.4%) Aluminum (4%), Rare earth metals (2.5%), Manganese (≥ 0.10%) | Creep resistance, high performance | ||
Zinc Alloys
Zinc alloys are compatible with both cold and hot chamber die casting processes. It is a strong, durable, and machinable material suitable for making strong die casting parts. Common zinc die casting alloys are in the table below.
| Alloys | Elemental composition | Properties | ||
| Zamak 2 | Base zinc, Aluminum (3.8-4.2%), Copper (2.7-3.3%), Magnesium (0.035-0.06%), Iron (0.02%), and elements like Silicon, Lead, Cadmium, Tin, and Nickel in trace amounts. | High strength, hardness, excellent castability, and creep resistance. | ||
| Zamak 3 | 96% zinc, 4% aluminum. | High strength, good castability, and dimensional stability. | ||
| Zamak 5 | Base zinc, Aluminum (3.8-4.2%), Copper (2.7-3.3%), Magnesium (0.035-0.06%), Iron (0.02%) | Good castability and fluidity, intricate and thin-walled castings, corrosion resistance | ||
Other metals compatible with the die casting process are lead, copper, and tin alloys. Before choosing any die casting material, ensure you are well familiar with their properties which can determine their applications and environment of use. A better option is to get material recommendations from a die casting service with a high reputation.
Advantages of High Pressure Die Casting
The wide application of the high pressure die casting process in several industries is due to its several advantages which include:
Quality Castings
Castings made using the process are accurate and uniform. They are strong and have good surface finish hence, they seldom need further post-surface finish processes such as machining.
Higher Production Rates
High pressure die casting has a high production rate due to the pressure and high flow rate of the molten metal. It is faster than other die casting processes such as low pressure and gravity die casting making it a top choice in high-volume manufacturing.
Thin Wall Products
The die casting process is suitable for making parts with wall thicknesses of 1.5mm – 12mm. Furthermore, it permits the addition of inserts (or co-cast parts) which reduces the component number during the part assembly.
Achieve Complex Design
There is a high flexibility in the mold design which makes high pressure die casting suitable for products with complex designs. Aside from that, molds are made using CNC machining which increases dimensionally accuracy.
Durable Dies
Die cast molds used in HPDC are highly durable, making them useful in multiple production cycles. Due to their durability, there is a reduction in the die castings per unit cost.
Disadvantages of High Pressure Die Casting
HPDC also comes with a few disadvantages which can affect the production process if not considered. As a result, you should discuss with a die casting rending service before you choose it.
Air entrapment
The high pressure involved during the die casting process can lead to air entrapment during the injection process. This can further lead to porosity and surface blister during heat treatment. As a result, high-pressure casting is not suitable for products that must not have air pockets. A better solution is to switch to low pressure die casting.
Initial Start-Up Costs
Businesses who want to set up a personal high pressure die casting machine should be wary of its high initial startup cost. The machine is costly and the mold cost can be very high. Also, the die cast mold can be very expensive to make due to the complexity and the cost per unit incurred. This huge investment is a reason many businesses consider using die casting services.
High scrap rates
High scrap rates can occur due to uncontrolled variables like temperature and pressure, and inconsistency in metal flow. This can affect the part quality and lead to scraps and waste. As a result, the is a compromised efficiency and higher production costs due to the need for additional raw materials.
High Pressure Die Casting Vs Low Pressure Die Casting
In cases when high pressure die casting is not suitable for a part, many die casting services recommend using a low pressure die casting process. This section talks about the differences between both die casting processes so you can make an informed decision.
Injection Pressure
The major distinction between high pressure and low pressure die casting is the pressure. Low pressure casting occurs at about 0.08 MPa and can reach 0.15 MPa. On the other hand, the other occurs at hundreds of MPa. The difference in injection pressure and the flow rate contributes to the low production speed in LPDC.
Flow rate of the liquid metal
Due to the low pressure, the flow rate of the liquid metal in low pressure die casting is smooth and can reach a speed of 150mm/s. On the other hand, the high pressure associated with the latter is unstable and can reach a speed of 60m/s to 120m/s. Furthermore, the low pressure and flow rate reduces air entrapment in the low-pressure casting.
Mold cavity material
The material required for the mold cavity in the LPDC can be metal or sand. However, in HPDC, the mold is made using only metal dies. Furthermore, with LDPC, you can make large or medium-sized casting parts with complex designs while HPDC can only make small and medium-sized castings.
Post casting process
Low pressure castings are subjectable to heat treatment, unlike the HPDC parts. Furthermore, the casting has a smooth surface that is inferior to the HDPC parts.
Cost-effectiveness
LDPC has a low operating cost making it suitable for low-volume production. On the other hand, high pressure casting is more suitable for high-volume order production
Application of the High Pressure Die Casting Process
HPDC is popular in the following industries:
Automotive Industry
HPDC is applicable in making structural automotive parts such as engine blocks and gearbox casing. Its popularity in the automotive industry is due to its ability to make parts with complex designs and wide material compatibility.
Medical Industry
HPDC is applicable in making medical parts made from metals including high-production imaging equipment and infusion pumps. Its high productivity, material compatibility, and complex design support make it a better process.
Aerospace Industry
HPDC in the aerospace industry is used in making engine parts. The aerospace industry works with materials such as zinc, magnesium, and aluminum due to their properties and high-pressure die casting is compatible with them.
ZINTILON Support for Your Custom Die Casting Service
High-pressure die casting compatibility with different materials and parts with complex designs makes it a top option for many manufacturers. However, its high initial cost can impede choosing it which makes considering a die casting service a better option.
At Zintilon, we have the manufacturing capability to manufacture high-quality die casting parts. We are quality-focused and offer you a competitive price. Contact us and enjoy a fast lead time and competitive market pricing.
Conclusion
High pressure die casting is a metal manufacturing process known for its ease of operation, lesser material wastage, and cost-effectiveness. This article talked about the process and its application in parts manufacturing. What is die casting? We hope this article helps. If you are looking for the right process for making high-quality metal parts? Let us help you get started.
FAQs
Why do you use CNC machining for die casting?
CNC machining is used for making the die cast mold due to due to its precision, accuracy, and high tolerance. Another manufacturing process suitable for making the mold is 3D printing.
Can I use high pressure die casting for plastics?
No, die casting is for metals. For plastic materials, you need to use injection molding processes such as insert molding and over molding.
What is the difference between high pressure casting and gravity casting?
While both die casting processes make use of the mold, in high-pressure casting, pressure is used to inject the molten metal into the die mold. This makes it a pressure die casting process. On the other hand, the gravity-casting mold is filled with molten metal under the influence of gravity.
