How To Choose Materials between brass/copper/bronze for CNC Machining

How To Choose Materials between brass/copper/bronze for CNC Machining


Brass, Bronze, Copper for CNC machining

In contemporary CNC machining, understanding the differences between brass, bronze, and copper is crucial. In most cases, these metals are considered to be the same as their likeness properties. The colors and elemental compositions of the three metals are somewhat alike but not identical. Therefore, it’s imperative to select appropriate material for an application. Their primary features distinguish one metal as suitable for one function or another.

In this article, we will provide a detailed analysis that may prove useful regarding CNC machining. Moreover, we will outline the material characteristics, various alloys available, and intended applications. The information helps make the right material choices when carrying out CNC machining processes.

Brass vs. Bronze vs. Copper: CNC Machining — Detailed Analysis

As mentioned earlier, these metals possess specific characteristics that are important for the CNC machining process. This section elaborates on those differences for clarification.

Overview of Brass 

CNC-Machining-Brass-Parts

CNC machining is optimal for brass as many types of brass alloys are available. Key alloys of brass include:

  • Alloy 260: Alloy 260 is a cartridge brass. It’s vital for cold working. Moreover, it is more often used in fasteners and couplers so, preferred in CNC manufacturing.
  • Alloy 272: The alloy features a yellow color. Alloy 272, is composed of roughly 33% zinc. It can be easily CNC machined and, thus can be applied in the manufacturing of several parts in industries.
  • Alloy 330: The alloy is the right one for CNC milling and CNC turning. It entails a low lead content. So, versatility makes it a significant alloy for the piping industry.
  • Alloy 353: It has another name of clock brass. The Grade is identified by its suitability for use where high precision is needed. It gives good yields in CNC machined parts.
  • Alloy 360: Alloy 360 features high formability. It’s widely applicable in manufacturing fittings, fasteners, and valves(such as side channel blower).
  • Alloy 464: These are also known as naval brass. It has high corrosion resistance. Its use is common in CNC machining applications in marine industries due to its high thermal stability.

Understanding each alloy type allows for the best performance during production to be achieved.

Overview of Bronze

CNC machining Bronze Parts

Bronze typically consists of approximately 90% copper and 10% tin. However, components including aluminum, zinc, silicon, manganese, and phosphorous can further improve its characteristics.

Bronze is preferred for certain reasons. It has a higher percentage of copper relative to the other metals. Historical analysis suggests that the Bronze Age started as early as around 3500 BC. The alloy has a low value of the coefficient of friction and exhibits considerable ductility in its mechanical characteristics. Moreover, it has a significantly higher melting point between 900°C and 1,000°C (1,650°F to 1,832°F), and relatively high strength. CNC machining provides reliability, and quality when it comes to manufacturing bronze pumps to fit specific needs. It can be used to produce durable and reliable machined parts/components.

Grades of Bronze

Different bronze alloys exist depending on the ingredients mixed; oil bronze, and acid bronze. Below are some common bronze alloys:

  • Alloy 932: High-leaded bronze typically contains around 6% to 20% lead, approximately. Due to its superior workability, it is suitable for CNC machining of brushings and washers.
  • Alloy 954: Aluminum bronze is effective under different working conditions. This alloy is widely used in industrial uses and mounting equipment.

Applications of Bronze

In CNC machining, bronze sheets are widely used owing to the mentioned properties. Common applications include:

  • Petrochemical industries equipment
  • Sculptures cast in bronze
  • Bearing for an automobile transmission
  • Bearing that operates under submerged conditions
  • Fittings for boats and ships
  • Electrical systems are connections

Overview of Copper

CNC machining Copper Parts

Copper is a metallic element found in the Earth, represented by the symbol Cu on the periodic table. Copper in its raw form has almost 100 recyclability. Its electrical and thermal conductivity, machining ease, and corrosion resistance make it ideal for CNC machining. Copper heat sink fins improve the internal heat transfer relatively well. Machining with computer numerical control provides the desired form of copper to achieve the required performance. This process raises the surface area by a large percentage. Improved heat dissipation is suitable for all kinds of electronics.

They are very accurate, which makes them fit perfectly into systems. Copper that is used efficiently disperses heat quickly thus minimizing the chances of overheating. CNC methods improve performance in thermal management applications. Because of the high conductivity of copper, it stands at the top of the list.

Grades of Copper

Copper types can be machined using CNC technology to produce different parts and prototypes. Some common copper alloys include:

  • Alloy 101: Al 101 is an oxygen-free copper alloy. It has excellent conductivity suitable for CNC electrical parts such as connectors.
  • Alloy 110 (Electrolytic Copper): Alloy 110 has good thermal stability. So, it finds extensive use in CNC machining of heat exchangers and electrical wiring.
  • Alloy 145 (Tellurium Copper): AI 145 has 0.7% tellurium to enhance its machinability but retains its high thermal and electrical conductivity suitable for CNC parts like switches.
  • Alloy 122: Due to its very good machinability and weldability, Alloy 122 is widely employed in CNC in the production of bus bars along with heat sinks.

Applications of Copper

Copper has excellent mechanical characteristics that make it suitable for several CNC machining uses in different sectors. Key applications include:

  • Heat sinks and heat exchangers
  • Arches and elements of architecture
  • Electric motor production
  • Telecommunications equipment
  • Submarine anti-biofouling parts

Comparing Brass, Bronze, and Copper-based on Their properties

Different material properties are known that assist in choosing between brass, bronze, and copper. The following presents information about these metals in detail.

Corrosion Resistance

Corrosion plays a critical role in product reliability. Bronze, being an alloy of copper, can be corroded by air and forms a tarnish layer on its surface. The intended layer serves as a shield against further corrosion from taking place.

Bronze is fairly resistant to corrosion by salt water. Therefore, it’s commonly used in marine hardware equipment. Nevertheless, it can lose its copper content over time because of chlorine. Copper also undergoes tarnishing and builds an oxide layer to prevent further corrosion resistance.

In general, the corrosion resistance of brass is comparatively less than bronze and copper. However, manganese-containing brass alloys may exhibit better corrosion properties than brass alloys containing lower manganese content. Of the three materials, bronze characteristically receives the least corrosion influence.

Durability

Bronze is a relatively stiff material, and mechanically strong. It has high ultimate tensile strength, and durability because of its highly rated-corrosion resistance. Moreover, copper is also a high-strength material but it can be bent or stretched without snapping due to low ductility. However, brass is more brittle than bronze and copper. It’s easily susceptible to cracking and has comparatively low corrosion resistance.

Weight

The weight is a critical factor when material considerations for CNC machining. The densities of bronze and brass alloys are almost in the same range. When lightweight materials are needed brass appears to be an efficient solution.

The density of brass is 8720 kg/m³. Bronze density varies between 7400 and 8900 kg/m³, and copper is the densest with a density of about 8930 kg/m³.

Machinability

Copper is slightly easier on CNC machines than brass and bronze. It can be bent, turned, and machined with relative ease. Copper alloys usually receive significant attention concerning to their high ductility. However, bronze is less ductile, making it more difficult to machine. Like copper, the brass material also exhibits a low level of ductility that results in poor machinability.

Weldability

Brass, bronze, and copper alloys can be joined through almost all conventional welding processes. These metals can be bonded via a process known as silicon bronze welding and Metal Inert Gas welding commonly known as MIG welding.

Brass alloys are MIG, TIG, and silver solderable, although lead-bearing alloys are more problematic in welding. Of the bronze grades, the unleaded bronze has moderate weldability but tends to fracture under severe loads. The best welding procedure for these alloys is suggested to be Shielded Metal Arc Welding (SMAW).

Material Properties Summary: Brass, Copper, and Bronze

The table below outlines the core differences in properties among brass, copper, and bronze.

Property Brass Copper Bronze
Elemental Composition Primarily Cu and Zn; may include Pb, Mn, Fe, Al, Si, etc. Pure copper Primarily copper and tin; may include nickel, aluminum, zinc, phosphorus, etc.
Corrosion Resistance Good Excellent Excellent
Weight 8720 kg/m³ 8930 kg/m³ 7400 – 8900 kg/m³
Durability High Low High
Machinability Lower High machinability Moderate
Weldability Good High High

Conductivity Differences Among Brass/Bronze & Copper

Understanding electrical and thermal conductivities may help you choose the right material for a particular use.

Electrical Conductivity

Copper has a conductivity rating of 100%. This makes it a standardized metal for measuring other electrical conductors. Copper, being a constituent of brass, has a conductivity of roughly 28%. However, bronze typically made from tin & copper provides a conductivity of about 15%.

Thermal Conductivities

  • Bronze: 229-1440 BTU/hr-ft²-°F.
  • Copper: 223 BTU/hr-ft²-°F.
  • Brass: At 64 BTU/hr-ft²-°F.

Comparison of Strength of Brass, Bronze, and Copper

Strength is another critical mechanical property in the assessment of material applicability. Consider the following factors:

  • Tensile Strength: Bronze placed first for having tensile strength between 350 MPa to 635 MPa. Brass has a tensile strength range between 338 and 469 MPa. In comparison, copper has the lowest tensile strength of about 210 MPa.
  • Yield Strength: Typically, Bronze comprises a yield strength of 125 to 800 MPa. Yield strength for brass varies between 95 and 124 MPa. In comparison, copper has a yield strength of 33.3 MPa.

Formability Considerations

It’s crucial to choose a material with exceptional characteristics for forming in CNC machining production.

  • Formability: Copper has high formability under large deformations without leading to cleavage. Therefore, copper is mostly applied to produce thin wire forms. PB1 phosphor bronze also exhibits fair formability. It’s mainly employed for cold-working practices. Brass has a comparatively low ductility and, thus is more challenging to form.
  • Melting Point: Formability is also associated with the material melting point in use. Among all, copper is friendly to work with. Since it has a relatively low melting point of 1085°C. However, its formability may be affected mildly. Bronze has a melting point of approx 913°C.  Oppositely, due to the low melting point of brass 927°C, it’s easier to form brass than bronze.

Color Comparison

Brass has a dull yellowish-golden. Therefore, it’s notable to be used in fittings, and joints. There are more variations in colors in the contemporary market. For example, it comes in silver-white, and in reddish-brown metallic shades similar to copper. Bronze also looks somewhat like gold, but less bright – it has a rather dull gold hue; copper, if exposed to air for the first time, looks reddish-brown.

Hardness Comparison

In CNC machining, the hardness of metals plays an indispensable role. Copper has a Brinell hardness of 35HB, while brass has a 55 to 73HB range. The typical hardness of the bronze score is 40 and 420HB. Since increased hardness is usually associated with brittleness. So, in certain cases, bronze becomes more vulnerable to fracturing.

Advantages of Brass, Bronze, and Copper In CNC Machining

Various types of brass, bronze, or copper materials show highly reusable CNC machining applications. The fact that they have diverse characteristics makes them more valuable in manufacturing settings.

Brass in CNC Machining

  • Durability: Brass is made from copper and zinc and it has a very good ability to resist corrosion. This characteristic makes it possible to have long-term use, especially in CNC applications.
  • Anti-Bacterial Properties: The copper part of the brass provides ions that act against dangerous microbes. As such brass is good for use in sanitary purposes.
  • Aesthetic Appeal: Brass gives out a warm yellow-gold appearance. As a result, there is a high demand for decorative CNC machined parts.

Bronze in CNC machining

  • Corrosion and Fatigue Resistance: Bronze forms a layer of oxide(tarnish green) when it corrode. Copper offers high tensile strength for complex cutting tasks when using Computer Numerical Control (CNC).
  • High-Dimensional Precision: Machining bronze by CNC allows one to produce extremely precision-demanding parts. Such dimensional accuracy is required by demanding manufacturing standards.
  • Thermal and Electrical Conductivity: Bronze has high electrical conductivity amongst the other physical and chemical properties. This trait is beneficial in the use of applications that require minimal energy conversion.
  • Versatile Surface Finishes: Thus, flexibility in Bronze enables it to replace brass, particularly in ornamental CNC applications where it is required.

Copper in CNC Machining

  • High Thermal and Electrical Conductivity: Copper has a higher conductivity than many other materials. This efficiency leads to cost savings in electrical applications.
  • Excellent Machinability: The malleability of copper allows it to be easily shaped and bent in the manner of the architectural design. This versatility leads to several CNC machined parts.
  • Corrosion Resistance: Copper, its reactivity is very low to keep it non-corrosive. This property is well suited to CNC uses in piping and other exposed applications.
  • Recyclability: Copper possesses a 100% efficiency of recyclability, without any compromise on quality. It also makes it a viable option in terms of cost for CNC machining services.

Brass vs. Bronze vs. Copper: Which Metal to Choose?

It becomes easier to select the right metal for CNC rapid prototyping when the differences between brass, bronze, and copper are understood. This decision is critical for attaining enhanced quality results. Consider the following aspects:

  • Machinability: All three metals have good strength, but they differ in machinability. Selecting the right metal also reduces the machining cost as well as the overall costs of the project.
  • Budget: Brass is most often the least costly of the three, whereas copper is the most costly. Lack of sufficient funds may just dictate your decision to go for brass.
  • Application and Utility: Copper performs well where high electrical conductivity is needed. Whereas bronze is desirable when hardness is paramount because of the tendency toward corrosion in machined components.

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