Aluminum Casting: Processes and Benefits

An aluminum cast is defined as a component, usually of lightweight material, that contains aluminum or other materials cast by an aluminum casting process.

It extensively describes the markets, which concurrently improve the efficiency of the industry, looking for aluminum that matches complex designs and products, and requires the durability, strength, and lightweight properties that aluminum offers.

Processes that aluminum casting entails vary between the sets and arrangements of requirements. So it must express casting parts of aluminum with various attributes.

In this article, we will describe the elements of casting aluminum and inform you of the option for your project.

What is Aluminum Casting?

Aluminum casting is the process of pouring molten aluminum into specially crafted dies, molds, or forms to manufacture parts with high precision and superior quality.

This highly effective method is perfect for producing intricate, complex, and highly detailed components that accurately adhere to the design specifications originally outlined.

Cast aluminum is a term that denotes a part made from aluminum and/or other metals using one of the various casting processes. Generally, most aluminum casting processes involve heating the aluminum (and other metals) and pouring them in molten form into a prepared mold with the desired product design. Afterward, the molten aluminum cools down, solidifies, and takes the shape of the cavity.

The aluminum cast has the properties of aluminum and the other metals. Furthermore, it develops an external coating of aluminum oxide, which helps to prevent corrosion, and it is stronger than the conventional aluminum material.

Aluminum casting is the process of pouring molten aluminum into custom designed dies, molds, or forms to produce parts with precise dimensions, specifications, and excellent quality.

This method is a very efficient way to produce parts since the casting process can create parts that may be intricate, complex, and with high levels of detail, meeting the requirements specified by the design’s intent.

Cast aluminum is a term that defines a part manufactured from aluminum and/or other metals formed using one of many casting processes.

Typically, all aluminum casting processes are preceded by heating aluminum (and other metals), pouring them into a preformed mold, with the finished product conceived from a predetermined design.

From this point, the aluminum takes shape, as molten aluminum cools and solidifies in conformance to the shape of the mold.

The aluminum cast has the properties of aluminum and the other metals. In addition, it develops an outside layer of aluminum oxide, which helps prevent corrosion, and it is harder than ordinary aluminum material.

Types Of Aluminum Casting Process

One common example of the casting processes of aluminum is the pouring of molten aluminum into steel molds, which are designed and manufactured to give exact size and shape to the cast aluminum piece, while providing a smooth surface.

These reusable or permanent molds can be made from steel or a different metal with a higher melting point, and are manufactured out of materials that will withstand the temperature of molten aluminum.

Permanent (or reusable) molds are a great option for high-volume production runs, and as they are reused, they have a very low labor cost associated with them, the production can consist of complex shapes and faces with high accuracy.

The amount of waste that is produced from the casting process is minimal, providing savings to the manufacturer and the customer. The only downside is that the creation and tooling of the tooling is labor intense.

Permanent Mold Casting

The most significant cost in aluminum permanent mold casting is in the machining and configuration of the mold (made from gray iron or steel), which is produced to the geometric shape corresponding to the designed part and has a constant parting line with the designs defined half and half.

The two halves are clamped tightly to prevent the infiltration of air and contaminants until molten aluminum is introduced.

When the mold is made from two halves, they are prepared by heating them up prior to pouring the aluminum; the aluminum can be ladled, poured, or injected.

After the aluminum is poured into the mold, the mold is allowed to cool, which allows the part to solidify. Once cooled, the part is removed quickly to avoid defects.

Although the process might look simple, this is a scientifically and technically designed process that employs die casting for high volume output.

Die Casting

Die casting is the process of manufacturing aluminum parts by injecting molten metal under high pressure into a pre-conceived or precision shaped mold.

The die casting process creates parts which have very little finishing or machining operations, and due to the rapid nature, is well suited for the mass production of components with higher volumes.

Two styles of die casting are hot chamber and cold chamber. The critical difference is the way the molten metal is introduced into the die.

In hot chamber die casting, the melting pot is in direct connection with the die casting system, and the molten metal is pushed by a plunger through a gooseneck into the die.

In cold chamber die casting, the melting pot is separate from the die casting system, and the molten metal is ladled from the melting pot into a cold chamber, where it is then pushed into the die by a plunger.

Vacuum Die Casting

Vacuum die casting uses a bell housing that is airtight, in which at the bottom of the bell housing, the sprue is, and coming out of the top of the bell housing is a vacuum outlet.

The vacuum die casting process begins with submerging the sprue below the surface of the molten aluminum. Next, a vacuum is created in the receiver, which establishes a pressure differential between the die cavity and the molten aluminum in the crucible.

The pressure differential pulls the molten aluminum up through the sprue into the die cavity and solidifies. Once the aluminum has solidified, the die is removed from the receiver, opened, and the part ejected.

By controlling the vacuum and the pressure differential between the die cavity and the molten aluminum, the filling rate can be controlled to meet the part design and gating specifications exactly. This control improves the ability to control the soundness and quality of the finished part.

Submersing the sprue below the surface of the molten aluminum insures that the aluminum is oxide and dross free. This leads to sound, clean parts with little foreign material.

Investment Casting

Investment casting, also called lost wax casting, begins by injecting wax into a die to form a pattern of the finished product. The wax patterns are attached to a sprue to form a tree configuration. The tree is repeatedly dipped into a slurry, which forms a strong ceramic shell around the wax shapes.

After the ceramic shell is formed and hardened, it is heated in an autoclave to remove the wax, and the shell is then pre-heated to the pouring temperature prior to pouring molten aluminum into the sprue.

The aluminum flows through the runners and gates into the molds. After the aluminum solidifies, the shell is broken away, and the cast parts are removed from the tree.

Lost Foam Casting

Lost foam casting is a type of investment casting in which polystyrene foam is used instead of wax. Patterns are molded from polystyrene and assembled in clusters, like the runners and sprues of typical investment casting.

Under low pressure, polystyrene beads are injected into heated aluminum molds, where steam is injected into the mold to expand the foam to fill the cavity.

The pattern is then enclosed in loose dry sand. The sand is then vibrated to compact it tightly to eliminate voids or air cavities.

When the aluminum is molten and it has been poured into the sand mold, the foam is burned off, and the finished castings are produced.

Sand Casting

The sand casting profile is based on packing sand around a pattern that will be recycled, which contains the shape, contour, and design characteristics of the final product.

The pattern will have risers, also referred to as casting risers or pouring risers, which serve for pouring molten metal into the sand mold and into the additional volume of material (the risers) to help accommodate the difficulty of shrinkage porosity when the molten material cools.

The pattern will also have a portion called a sprue that provides a passage for the molten material to enter the sand mold cavity.

The pattern is oversized slightly to accommodate the molten material that will shrink in size as it cools. The sand casting process is stable and has enough strength range to maintain the shape of the pattern and to resist interaction with the molten material.

How to Choose the Right Aluminum Casting Process?

Each casting process has pros and cons that are specific to that casting process. If you are to pick the best casting process for you, you will have to consider the following:

Design Complexity

The complexity or simplicity of the end product design will influence which aluminum casting process you choose. Most multidimensional (severely complex) or multi-faceted aluminum casting components will be manufactured using sand casting.

The sand casting method should be the best place to start when designing your product experience with complicated design features.

 If you have the need for cast aluminum parts that have an accurate dimensional profile, then permanent mold castings would be a better process to choose.

Manufacturing Speed

The die casting process pressures or injects its profile via the concepts of pressure with a respective injection; therefore, die casting is the best method for mass producing profiles of aluminum castings. Sand casting is the second-fastest production process, and permanent mold casting is the slowest.

High Quantity

Die casting is the best-suited process for producing large quantities of aluminum cast parts. However, to strike the right balance between high quantity and tool cost, sand casting and permanent mold casting are both good options.

Prototyping

Sand casting is the best-suited process for prototyping due to its low investment costs. The alternatives would require a high investment cost, which is not feasible because prototyping is intended for a few parts.

Strength and Surface Finishing

Permanent mold casting offers the best balance of strength and good surface finish. That said, sand casting and die casting have comparable strength, although die casting has the best surface finish.

Advantages of Aluminum Casting

Design

Aluminum casting can make any part in any size, shape, or configuration. It does not matter if it is a small electronic component or a large transmission casing or clutch housing for an automotive vehicle; each part is produced with high tolerances according to design intention and requires very little finishing.

Engineers can design components that they have the utmost trust and confidence in, that their components will meet performance expectations and maintain their design integrity through assembly, disassembly, repairs, and reprocessing.

Versatility

The vast design possibilities offered by aluminum casting allow engineers to tap into its advantageous properties. Engineers can truly design custom and unique products that realize imaginative ideas.

Rate of Production

Manufacturers are always looking for quicker and more efficient production. Computerization has increased pressure for timely deliveries, and the desire is endlessly growing. Aluminum die casting has surely met the demands of high level production, faster than other alloys.

Strength

Aluminum cast parts would also have a good strength to weight ratio, greater than other metals and alloys. The light weight of aluminum components facilitates aluminum fatigue life to surpass steel fatigue life, allowing for their durability and longevity to be key components in modern products.

Appearance

Aluminum castings are not only strong and light but also offer an attractive appearance. In regard to appearance, aluminum castings provide a great deal of value in personnel areas since often an aesthetically correct aluminum casting requires no modifications or re-engineering.

Cost

Industries aim towards cost reductions at all quality levels, including products and services. Aluminum casting is a low-cost option, due to the speed of production, minimal finishing required, and the lower cost of materials.

Speed of production leads to material and labor savings to the company, which saves the hydraulic pressure compression molding process for consumers.

Corrosion Resistance

Aluminum castings will take on an oxidized surface when exposed to air. Since the natural oxidation process allows for previously cast aluminum components to be reconstituted, successful oxidation will help to provide greater longevity for aluminum castings.

Application Of Aluminum Casting

Since the introduction of the Bayer and Hall-Heroult processes used to extract aluminum, aluminum has become a necessary element in the production of many commercial and industrial products.

Improvements to these processes streamline success for the engineers and designers to develop and utilize aluminum at all levels of the design planning stage for practicality and cost effectiveness.

There is a great deal of engineering performance wrapped up in aluminum, whether it be aeronautics or electric kitchen appliances.

Aluminum can be expected a great deal of reliability and durability through a long service life that incorporates many things due to its unique properties as a metal.

Its adaptability makes it easily shaped and formed for many design purposes. There are over 270 different elements that are available to alloy with aluminum to improve their properties and advantages.

Aircraft Components

Aerospace has relied on aluminum at least 80% in its structural materials since World War II. Cast aluminum components have the proper characteristics and properties. The aircraft industry has had very significant savings using cast aluminum components.

Automotive

Since improving the fuel economy of vehicles is an overall focus, auto manufacturers are using more high-strength aluminum castings in their designs.

To accommodate this growth, aluminum casting manufacturers have had to develop refined and improved techniques and methods to increase outputs and efficiencies and decrease costs.

Aluminum automotive castings include oil pumps, water pump housings, connectors, transmission parts, and a variety of brackets. The reliability and durability of cast parts continue to advance vehicle design and performance, which is an obvious necessity.

Lighting

Aluminum cast lighting fixtures have many inherent benefits, such as being lightweight and non-toxic. Their corrosion resistance also makes them ideal for outdoor use.

Common methods used to manufacture aluminum cast lighting fixtures include permanent mold and gravity casting, with each method allowing companies to work with lighter aluminum forms and reducing time spent in production.

As is the case with automotive components, casting aluminum used in lighting fixtures is economic and efficient.

Aluminum casting processes are so flexible and versatile, they can easily be prepared into nearly any shape for different designs, while providing the same characteristics and stability in the application.

The characteristics of aluminum cast lights explain their immense popularity. The ease of production, lightweight nature, and great strength allow for a wide range of applications.

Agricultural Equipment

Aluminum cast components for agriculture have the same requirements and specifications as automotive production, but typically call for greater strength/durability, given the greater level of use (on top of environmental conditions).

Costs are always an important consideration in any agricultural production scenario. Therefore, aluminum castings can provide sufficient strength to perform important production operations, i.e., crankcase housing, gearbox housing, in order to be efficient at production costs.

Heatsinks

The fundamental purpose of heatsinks is to disperse heat away from electronic components/devices. The benefits of aluminum cast heatsinks are they require less machining in the final production, which aids in both cost and manufacturing efficiencies.

Fins for cooling could also be designed and cast thus improving manufacturing efficiencies at the same time.

Aluminum cast heatsink can be internally cast with electrical conductors so these are efficiently grounded during operation.

Many features of heatsink can be cast therefore requiring less secondary operations, i.e., machining or additional assembly. This too allows for additional cost savings.

Brackets

Aluminum castings are commonly used to produce brackets for both heavy industrial equipment and household appliances. The casting process allows for production of part near-net shape so assembly or welding is not necessary.

One-piece cast aluminum brackets provide the user with greater strength, durability, and decreased likelihood of failure. If holes are needed, they can be molded into the casting, which decreases the overall hand finishing after production.

Golf Products

The use of aluminum casting for golf equipment is growing due to durability, stability, and ease of shape. The goal is to provide golfers affordable high-quality equipment. Items that are developed with this casting process include: golf ball warmers, golf clubs, golf handles, and brackets.

Enclosures

Aluminum cast enclosures can be used to protect delicate electronics in a variety of environments. Aluminum is an excellent shield against radio frequency interference (RFI) and electromagnetic interference (EMI), thus increasing their effectiveness.

The casting process creates a seamless enclosure with a watertight seal adding to the durability of the product in all types of conditions.

Organizations like the National Electrical Manufacturers Association (NEMA) set standards and specifications for cast aluminum enclosures. Creating cast aluminum enclosures in compliance with NEMA guidelines is crucial to their acceptance in the marketplace.

Military

A variety of parts and components are produced for the military in aluminum castings and they must meet strict government specifications.

The processing and manufacture of military component parts is strictly controlled with specific requirements describing the material properties and characteristics.

Military parts are surprisingly specialized and can be challenging for a manufacturer since they require precision engineering and attention to detail.

Here are descriptions of two unique military components:

Fire Suppression Housing

A fire suppression housing is designed to extinguish fires in armored vehicles thus enabling the armored vehicle to take incoming fire and still allow its occupants to be safe.

Missile Nose Piece

A missile nose piece, which is mounted on the front of a missile must be cast to take the G-forced of a missile launch. The whole casting process is monitored to ensure a pressure-tight seal and that it has been properly engineered to meet these specifications.