The gravity die casting process has a long history in manufacturing due to the production of durable parts with a high level of accuracy. It is suitable for non-ferrous materials with aluminum being the most common. 

Aluminum gravity die casting
Aluminum gravity die casting

The process surrounding the use of gravity die casting process is straightforward, however, it is important to understand how this method works before using it for your project. As a result, this article is your guide on gravity die casting as it explains how the process works, its advantages and disadvantages, compatible materials, and typical applications. 

What is Gravity Die Casting?

Gravity die casting part
Gravity die casting part

Gravity die casting process is a common die casting technique that makes use molds to produce parts. The molten metal flows into the mold freely under gravity without the use of external pressure or force. 

Gravity die casting manufacturers use this technique primarily for aluminum alloys. Hence the term aluminum gravity die casting. Nevertheless, it is also suitable for steel, brass, zinc, and some other non-ferrous metals. 

Aluminum gravity die casting can be manual or automatic. The automated casting process is faster. It is important to know that the mold is made using steel or cast iron. These materials are strong and can withstand the temperature and heat that comes with casting. 

Tooling and Equipment Used in Gravity Die Casting

Different tools and equipment make up the gravity die casting process. Each one plays a crucial role and when absent, the system will not function. Let us explore the most important gravity die casting tools and equipment.

The Die (Mold)

The die is the heart of gravity die casting. The final part takes the shape of the mold. Hence, it must be flawless. The die, usually a product of CNC machining, is reusable and permanent. 

Gravity Die Casting Machine 

It controls the opening and closing movements of the die and holds the die firmly throughout the casting operation. Gravity die casting machine is robust and has smaller parts to make a whole. The main components of a gravity die-casting machine include 

  • Frame, 
  • Cooling system, 
  • Pouring system, and 
  • Control panel.

The Crucible Furnace 

The furnace is a melting oven that liquifies the metal to be cast. It performs its function using a crucible to house the metal. This heating chamber may be titling or non-titling. With the titling type, the whole furnace is slanted to direct the molten metal to produce parts at a fast rate. 

Trimming Tools

Though not a direct gravity die casting component, they are also important. Gravity die casting manufacturers use trimming tools to cut off excess materials from casted parts.  

How Does Gravity Die Casting Work?

Gravity die casting metal mould
Gravity die casting metal mould

The gravity die casting process is like other die casting methods with the difference being the mechanism of injecting the molten metal enters the die. There are six distinct steps as discussed below:

Die Preparation

After manufacturing the die using a process such as CNC machining, it must undergo preparation. These include:

  • Heating the die to a predetermined temperature creates a thermal balance that helps to increase the lifespan of the die.
  • Cleaning the die to remove impurities that might affect the final part’s quality. 
  • Using a lubricant or a refractory material on the mold for easier removal of the final part. 

Molten Metal Preparation

The next step is to prepare the metal pellets. Before placing the metal in a crucible, ensure that it is free from dirt and debris. Now, heat the metal material slightly above its melting point until it liquified. 

Injection 

After melting, transfer the molten metal into the die cavity carefully. Pour it vertically under gravity until the die fills up. When using a die, ensure the draft angle is within 1-2 degrees for a seamless operation. 

Cooling and Solidification

Following the pouring stage, leave it to cool. Give the metal sufficient time to solidify as it takes the shape of the mold accurately. Premature cooling may affect the grain size of the alloy and lead to casting defects. 

Ejection 

Thereafter, the operator opens the die halves using an ejector pin and carefully removes the final part. These pins are attached to the casting setup to securely push out the part from the die. 

Trimming and Finishing

Occasionally, a gravity die-cast part comes with excess materials that need to be trimmed off. Carefully remove flash, runners, or sprues from the manufactured part for a flawless finish. Finally, clean and use appropriate surface finishing options to improve the appearance.

Gravity Die Casting Advantages and Disadvantages 

Gravity die casting workpiece
Gravity die casting workpiece

Using the gravity die casting process for manufacturing comes with unlimited advantages. This is the go-to technique when quality and accuracy are determining factors. The following are some of the advantages of gravity die casting.

High-quality Castings

Gravity die casting produces high-quality and durable parts. When compared to other types of castings, the parts have finer grain structure and are less porous. Additionally, using iron or steel molds improves the mechanical properties of parts including hardness and strength. 

Good Surface Finish

Parts made with this manufacturing method have an excellent surface finish. The castings solidify uniformly because it does not involve any form of pressure. As a result, the surface is smooth and consistent without irregularities. 

Dimensional Accuracy

One of the most important advantages of gravity die casting is the dimensionally accurate parts it produces. This makes it suitable for demanding industries with complex shaped parts. 

Low Production Costs

Gravity die casting is a cost-effective way to manufacture metal parts. When one is just starting, it may be expensive to set up the equipment and tooling. However, these costs reduce as one begins full production. 

Suitable for a Wide Range of Materials

Gravity die casting process is compatible with many materials. This production process can shape aluminum, zinc, and magnesium flawlessly. Note that these materials have unique properties and may require different requirements such as melting time and temperature. 

Despite the numerous advantages, gravity die casting has the following limitations. 

Slow Process

Unlike other casting processes that use pressure, gravity die casting is slower. The mold fills up slowly under the force of gravity. However, this slow speed prevents turbulence within the die to produce stronger components. 

Limited Part Size

Gravity die casting comes with size limitations. This manufacturing method is best suited for small parts. Aside from that, the workpiece must have a thick wall, usually above 5mm since the process does not make use of pressure during the injection process. 

Is Gravity Die Casting Good for Mass Production?

Gravity die casting is not an excellent choice for mass production. This casting technique has an extended cycle time and the amount of time a machinist spends on a single part is long. As a result, it makes it more efficient in small and medium-scale production.

Furthermore, it might be a little challenging to scale up production when using the gravity die casting process. As a result, you may want to explore other casting methods for large projects. 

Additionally, the more the number of parts, the higher the energy consumption and scrap rates. Mass production using gravity die casting may be energy intensive. 

Common Materials Used in Gravity Die Casting

Part of gravity die casting
Part of gravity die casting

Aluminum is the most common materials compatible with the gravity die casting process. Below are a few common aluminum alloys used with the process in no order of priority. 

A356

A356 is one of the most common aluminum alloys for gravity die casting. It contains more than 90% aluminum and other elements such as silicon, iron, zinc, copper, magnesium, and manganese in small quantities. This aluminum alloy is lightweight with high strength. Additionally, its excellent fluidity and good castability properties make it suitable for gravity die casting. 

AlSi7Mg

This alloy is a perfect blend of aluminum, silicon, and magnesium. AlSi7Mg’s high strength-to-weight ratio makes it perfect for casting durable yet lightweight parts. The magnesium content increases this alloy’s fluidity while lessening porosity. On the other hand, silicon is responsible for the lower melting point and shorter cycle time. 

A380

Aluminium gravity die casting suppliers use the A380 extensively because of its many benefits. It contains mainly aluminum and many supporting metals. It has an excellent combination of thermal and mechanical properties. Additionally, its high silicon composition contributes to the high strength of the final parts. 

LM25

LM25 is ideal for complex-shaped castings. It contains copper, silicon, manganese, nickel, and magnesium with aluminum as the base metal. These additional elements increase its hardness, strength, and fluidity. A higher fluidity means that it stays longer in its liquified state. Hence. LM25 fills all parts of the die before solidification begins. 

LM6

LM6 is popular when it comes to gravity die casting. This alloy retains its strength after melting and cooling. Furthermore, the presence of a high percentage of silicon enhances its castability property. With silicon, it is easier to fill all the extremities of the die cavity.

Gravity Die Casting Vs Other Casting Techniques 

We have explored the gravity die casting advantages and disadvantages. Now, let us compare it with other casting methods available using the process, process speed, surface quality, design complexity, and volume of production. 

Gravity Die Casting Vs High Pressure Die Casting

In contrast to using gravity, high-pressure die casting forces molten metal into a die under high pressure from a few hundreds to thousands PSI. Furthermore, the gravity die casting process is slower due to reliance on gravity unlike HPDC that uses pressure.

Due to the slow flow rate of the molten metal, parts made using gravity die casting have better surface quality and require fewer finishing techniques. However, high pressure die casting is more best suited for parts with complex shapes and designs and high-volume production 

Gravity Die Casting Vs Low-Pressure Die Casting

Low-pressure die casting uses a low air pressure to cast metal parts unlike the gravity die casting process. As a result, parts made with gravity die casting process are less porous and stronger. 

When it comes to cost, there is a strike of balance. The initial investment is lower in gravity die casting. On the other hand, low-pressure die casting becomes more economical as production volume increases.

Gravity Die Casting Vs Sand Casting

Sand casting uses a sand mixture as the mold’s material and can produce more complex shaped parts with intricate designs. Parts sand casted have thicker walls when compared with gravity die casting. Furthermore, the parts have a coarser finish due to the sand mold. As a result, there is usually a need for surface treatment.

Typical Applications of Gravity Die Casting 

The gravity die casting process is a common manufacturing process in many industries due to its environmentally friendliness and ability to meet many industries’ tight tolerances. Common industries using the process include: 

Automotive Industry

Auto part manufacturers use gravity die casting extensively due to its high dimensional accuracy. Hence, it is applicable in making parts such as transmission parts and engine components, and engine components like cylinder heads and engine blocks.

Medical Devices Industry

Aluminum is a common metal in the medical industry because it is biocompatible. Its excellent thermal conductivity and strength also make it stand out. As a result, Aluminum gravity die casting is common in manufacturing surgical devices casings, and imaging instruments. 

Aerospace Industry 

Aluminum gravity die casting allows the aerospace industry to make parts with a high strength-to-weight ratio. Furthermore, most of these parts have excellent corrosion resistance properties. Altogether, with aluminum and gravity die casting, the aerospace industry can save costs and increase fuel efficiency.

Construction and Architecture components 

Many construction components are made using aluminum gravity die casting. Its high-quality surface finish makes it ideal for manufacturing architectural elements where functionality and aesthetics are important. This casting method is useful when producing door and window hardware.

Electrical Industry 

Die gravity casting has many uses when manufacturing electrical parts. Because aluminum is an excellent conductor of electricity, die gravity casting has applications in electronic devices. Its lightweight also makes it useful for outdoor LED lighting housings.

Cookware Components 

Aluminum gravity die casting also has applications in kitchenware manufacturing. Most ovens, non-sticking pans, and attachments like knobs are products of this casting technique. These cookware pieces are lightweight, durable, and evenly distribute heat to reduce cooking time. 

Zintilon Support for Your Custom Gravity Die Casting Service 

After a thorough exploration of aluminum gravity die casting. The next step is to choose the most reliable supplier. There are many aluminum gravity die casting companies available and choosing the right one may determine your manufacturing success. Zintilon is here to help with all your custom gravity die-casting services. We maintain standards through the manufacturing process to produce high-quality and durable parts with our many finishing options. 

From quotation to delivery, our support team is always available to provide answers to your questions and concerns. Make us your aluminum gravity die casting supplier and experience the Zintilon manufacturing difference. Request a quote today and get feedback within 24 hours!

Conclusion 

Gravity die casting is one of the earliest die casting processes that is still in vogue because of its many benefits such as lesser porous and very fine surface quality. What is gravity die casting? What are the steps in the gravity die casting process? We hope this article has answered all your questions. 

FAQs 

What lubricants are used in aluminum gravity die casting?

Gravity die-casting manufacturers use different kinds of lubricants to aid easy removal of the final part. They come as water-based lubricants, saturated aliphatic oils, graphite-based lubricants, or those from boron nitride. Factors including type or aluminum alloy, the desired surface finish, and eco-friendliness will affect your choice when selecting a lubricant.

Is gravity die casting suitable for thin-walled parts?

No, gravity die casting is not suitable for thin-walled parts below 5mm being a non-pressure die casting process. For thin parts with wall thickness lesser than 0.5mm, the better option is high pressure die casting. 

Is gravity die casting appropriate for ferrous metals?

It is an uncommon approach to use gravity die casting for ferrous metals. This is because ferrous metals are magnetic and have high melting points. Using alternative metal fabricating methods is preferred to avoid complications. 

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