Calculating the cost of casting aluminum vs. bronze is not as simple as calculating the cost of the raw metal materials involved. If it were just a matter of materials, the answer is easy – bronze is clearly more expensive and costs anywhere from 5x to 10x more than aluminum.
Costs vary from manufacturer to manufacturer. Each supplier has strengths and weaknesses in their capabilities, production process, and relationships with material suppliers. The casting methods used can greatly increase or reduce production costs and will be the largest factor in calculating the cost of casting aluminum and bronze.
Below we discuss in more detail what factors impact the cost of casting aluminum versus bronze, what creates cost savings, and what contributes to the overall cost of each casting method and the different properties of each metal.
Raw Cost of Aluminum and Bronze Are Not The Biggest Variables
Casting is used to make complex shapes that would be difficult or expensive to make using other metal manufacturing methods. Casting classifications are divided into two main categories: expendable mold and permanent mold casting.
The three primary methods of metal casting are:
- Die Casting
- Sand Casting
- Investment Casting
Each method has its strengths and weaknesses. Both ferrous and non-ferrous metals can be sand or investment cast. Die casting is an excellent choice for high-volume runs, and investment casting creates parts with superior finishes that seldom require additional machining.These strengths and weaknesses are what impact the overall cost of metal part production.
How are Casting Costs Calculated?
Calculating the cost of casting aluminum compared to bronze or even other metals is not cut and dry. There are plenty of casting calculators on the internet, but those only provide a rough estimate.
You must consider the material (metal), part/component geometry, desired quality, and production requirements. But that also fails to factor in any additional costs you incur to reproduce defective parts, tariffs, or packaging and transportation costs.
- Material: Metal choice is one of the most important determinants of casting. Metal costs vary based on market price and a manufacturer’s relationship with material suppliers. While metals, such as aluminum, account for 40-60% of total casting costs, others like iron might only contribute 10-25% of the total production cost. Bronze can cost five to ten times more than aluminum.
- Melting: Each metal has a unique melting point. Metals with higher melting points require more energy to reach a molten state and will, therefore, incur a higher cost in the manufacturing process.
- Mold Creation: A majority of casting processes use either an expendable mold or permanent mold. Expendable molds, such as sand molds, must be recreated after each cycle and can account for 5%-15% of casting costs. Permanent molds can last millions of cycles, which creates cost savings for longer production runs.
- Pouring: These costs vary based on if the metal is poured manually or if it is an automated process. Some higher melting point metals require manual pouring. When combined with melting, these two factors make up 15%-20% of the overall cost.
- Core-making: Complex parts require sophisticated molds and sometimes the addition of cores within a mold. These types of parts may require extended fill and cooling times, which adds to the overall cost.
- Finishing: Certain metallic properties make finishing less labor-intensive. Non-ferrous metals require more simple equipment for trimming and finishing compared to their harder ferrous counterparts.
- Inspection: This step will depend on a part’s application. More rigorous inspection such as x-ray or destructive testing will incur a greater cost than a visual inspection.
- Heat Treatment: Castings that require added strength by heat treatment will have an additional cost.
To get the most accurate cost, it is best to talk with manufacturers to get real time quotes, accurate timelines, and current material costs.
Die Casting Aluminum vs. Bronze
Die casting is a metal forming process that is used to create parts and components from non-ferrous metals. These are metals that do not contain iron. It can mass-produce thin-walled parts with dimensional accuracy, surface finish better than sand casting, and high tolerances.
Bronze alloys have a higher melting point, which shortens the die mold lifespan. Other casting methods are best to use with this material.
Aluminum die-cast parts have an excellent strength to weight ratio, good corrosion resistance, and high electrical and thermal conductivity. In fact, low-density aluminum is essential to the die casting industry.
What Contributes to Aluminum Cost?
The largest disadvantage of die casting is the high initial capital investment. Most die cast molds are made of steel and tend to be the most expensive part of the die casting process. When compared to other processes, the machines, furnace operating costs (for cold chamber casting), and its related components are costly.
For die casting to be truly affordable, it must have a high production volume. This casting process is subject to increased porosity and, with the wrong partner, could produce higher defect rates. Miss-runs and flow lines are additional drawbacks of the process.
Die-cast tools can cost anywhere from $7,500 to as high as $75,000.
What creates cost savings with Aluminum Casting?
If you are not already tired of hearing it, the answer is longer production runs. But that’s not all.
Die casting creates near-net-shape parts, which limits secondary processes. Inserts such as heating elements, threaded inserts, and high strength bearing surfaces can be used in die casting where that is not possible with other methods.
Sand Casting Aluminum vs. Bronze
Sand casting uses a sand mold (which is usually mixed with clay and a binder) to create cast parts in a variety of shapes and sizes. It is the oldest known casting process, and 0ver 60% of all castings are produced this way.
Sand casting aluminum vs. bronze is ideal for prototyping and producing runs of 1 to 5,000 parts per year. This method works for parts of all sizes. Sand casting has lower dimensional accuracy than other methods and is not well suited for complex parts.
Sand-cast aluminum parts are widely used in the auto and transportation industry to make car suspensions, gear casings, and powertrain assemblies.
Bronze alloys are used in industries that require high corrosion resistance, such as marine propellors or parts that may be submerged in water.
What contributes to cost?
The surface finish of sand cast parts is grainy like the sand molds they came from and are 250 Ra when before any secondary processes. Extra work is needed for sand cast parts to be acceptable in most applications.
Additionally, sand cast parts have lower tolerances than parts cast using other methods, so they require additional machining.
What creates cost savings?
Sand casting pattern costs range from $500 to $7,500, depending on the size and complexity of the part. Because sand molds are relatively simple to make, there is a lower capital investment and lower tooling costs.
Investment Casting Aluminum vs. Bronze
Investment casting creates complex parts with excellent finishes from a ceramic mold tree. This method can be used to make parts that are only an ounce to parts weighing several hundred pounds.
Investment casting allows for ferrous and non-ferrous metals to be cast. These parts usually will not require extra finishing methods and will be dimensionally accurate.
Aluminum investment casts are popular in electronics, medical, food and beverage, and aerospace equipment. It is used to make parts such as valves, levers, heat sinks, and pistol frames.
Bronze alloys are resistant to metal fatigue and corrosion, making them ideal in high-stress applications. Many industries value the mechanical properties of bronze alloys, and it is used to make parts such as bearings, marine castings, pumps, valves, and bushings.
What contributes to cost?
Shorter production runs will be more expensive. Creating a ceramic mold from a wax pattern is labor-intensive and requires expensive binders and refractories.
What creates cost savings?
Investment cast finishes average 125 Ra, which eliminates the need for finishing processes. Because parts cast with this method also have tight tolerances, it greatly reduces the amount of secondary machining.
Is cast-aluminum rustproof?
Yes. Aluminum is a non-ferrous metal, which means it does not contain iron and means it will not rust.
Is Aluminum Stronger than Bronze?
Aluminum weighs around one third the weight of bronze and is less than half of its cost per pound. Cast aluminum is softer than bronze, but it is more brittle. Thin sections break under severe stress, and, unlike bronze, it is difficult to weld.
Bronze, on the other hand, is not usually 100% bronze. It is an alloy. In fact, it is usually 80%-90% copper, and the remainder is tin, zinc, lead, and iron.
Sometimes other metals such as nickel, aluminum, and metalloids like arsenic, phosphorus, or silicon are added. These additions produce different alloys that have added stiffness, ductility, or machinability.
To get the best of both metals, manufacturers will use aluminum bronze alloys.
What is Aluminum-Bronze alloy?
Aluminum bronzes are valued for their high strength and corrosion resistance compared to other bronze alloys. At high temperatures, they display low oxidation rates, low corrosion rates in atmospheric conditions, they are tarnish-resistant and have low reactivity with sulfurous compounds, and other exhaust products of combustion.
This corrosion resistance comes from the aluminum. When it reacts to atmospheric oxygen, it forms a thin, tough surface of aluminum oxide that creates a barrier in the copper-rich alloy. Adding tin can make this super alloy even more corrosion resistant.
Their corrosion resistance to seawater makes them a popular choice in marine applications. Another reason they are popular with this industry is because aluminum bronzes are biostatic, which means it prevents the colonization of marine organisms such as barnacles, mussels, lichen, and algae.
Typical applications of aluminum bronzes include plain bearings and landing gear components on aircraft, engine components, valve components (especially on seagoing ships), naval architecture, ship propellers, and underwater fastenings.
Aluminum bronzes are in the highest demand from the following industries:
- Water supply
- Oil and petrochemical
- Sea water-related services
- Specialized structural retrofit building applications
Which metal should I choose?
Material choice will depend on the parts application, production volume, and budget.
Here is what you should consider:
Aluminum is inexpensive, has an excellent strength-to-weight ratio, and great thermal and electrical conductivity. Using aluminum alloys can reduce the need for finishing treatments, and additional alloys can be added to improve tensile strength, or nickel can be added to increase rigidity.
Bronze castings are durable and highly accurate parts weighing up to fifteen pounds. They are generally suitable for applications requiring a tensile strength of less than 8000 pounds per square inch.
Determining the cost of casting aluminum vs. bronze is no easy task. Many factors such as casting method, application, and production volume influence cost.
Our team can help you generate RFQs and get accurate, competitive pricing for your casting needs.