Bronze CNC machining can be tricky. Blunting, overheating, and getting a smooth finish usually contribute to time wastage and unsatisfactory outcomes. These challenges can be caused by quality issues or cost drivers. However, you can address such problems by following the right ways to machine bronze.
To increase efficiency in bronze machining, high-speed cutting fluids, appropriate tools, and speed must be ensured to apply. Carbide or high-speed steel can be used for the cutting tools, the right use of coolant should be made to minimize heat and consequent wearing-off of the tools.
So, now it’s time to dig deeper and learn more to find out how to get the best output in your bronze machining project.
What is Bronze Machining?
Bronze machining can be accomplished through CNC drilling, milling, turning, and grinding processes. Copper-tin alloy bronze possesses high mechanical characteristics such as strength, corrosion, and wear resistance. These characteristics make it a desirable material for demanding parts used in aerospace, automotive, marine, and manufacturing industries where high stress, load, and harsh conditions are encountered.
Benefits of Optimal Proper Bronze Machining
Generally, bronze machining needs much attention because of the work-hardening tendency of the material and high rigidity. Bronze, in particular, requires certain approaches to machining to minimize tool wear, overheating, and poor surface quality in comparison with softer metals.
Accurate results can only be achieved when you incorporate the right tooling, appropriate cutting rates, and efficient lubricants/coolants are applied. Bronze machining helps produce several parts including bearings, bushings, gears, and valves, which are very durable and have a long lifespan.
Step-by-Step Process of Bronze Machining
Here’s a step-by-step guide to CNC machining of bronze;
1. Select the Appropriate Bronze Alloy
Machining bronze starts with selecting a reasonable alloy or bronze grade as per specific project. Some common types of bronze are tin bronze, phosphor bronze, and aluminum bronze; all of which possess characteristic features such as corrosion resistance, strength, and wear resistance.
2. Choose the Proper Equipment
Bronze is a rigid metal. Therefore, proper equipment has to be used in bronze machining. Carbide or high-speed steel (HSS) tools are most often used because they have the excellent capability to cut the high-strength material in question. When precision machining nonferrous materials, do not use tools intended for ferrous materials as they tend to wear out the tools and poor surface finishes.
3. Select the Right Tool Geometry
Choose the right tool geometry to reduce heat and minimize tool wear. In the case of bronze machining, a relatively low cutting speed is used in comparison to other metals, and moderate feed rates to avoid overloading the tool.
4. Employ Cutting Fluid
Coolants are an important aspect in reducing friction between the tool and workpiece, helping to cool the tool, and preventing the buildup of chips. It’s recommended to use a water-soluble coolant or synthetic oil when machining bronze.
5. Machine the Bronze Part
Begin the entire process by appropriately placing the workpiece on the metalworking machine. For turning, the lathe needs to be set for the right speeds and feeds. It’s important to regularly check dimensions and surface textures.
6. Checking on Tool Wear
Bronze is a harder metal than other metals. It tends to wear the tools much faster than the softer metals. Therefore tool wear needs to be checked regularly. Make it routine to inspect the cutting edges for signs of degrading, to avoid poor quality of parts by using worn-out tools.
7. Wash The Workpiece
After machining wash the workpiece to remove the metal chips, cutting fluids, or any other foreign material. The intended step is helpful to ensure it does not have any defects.
8. Check the Finish
When the operational part is machined, check on the dimensions, finish decisions, and quality of the part. Perform strict quality checks on machined components by using measuring instruments such as calipers, micrometers, and surface finish gauges to confirm parts’ correct measurement standards.
9. Cleaning, Storage, and Maintenance of Tools
Lastly, make sure that tools and equipment are cleaned, stored, and properly taken care of to offer their best performance in the next machining practice. Because the efficiency of the cutting tools will improve and costs will be reduced if the cutting tools are maintained and sharpened often.
Challenges Associated with CNC Bronze Machining
It’s important to understand the various challenges associated with machining Bronze since it’s a unique material. Below are some of the key challenges faced during bronze machining:
1. Tool Wear and Durability
Tin and aluminum bronze are among the hardest bronze alloys, so, conventional cutting tools become blunted rapidly. It leads to tool wear, decreased longevity of the tools, and frequent need for replacement, which defers the cost of machining bronze.
2. Heat Produced and Work Hardening
In bronze cnc machining, bronze produces excess heat, when cutting at high speeds. This heat can cause work hardening whereby the material becomes harder and difficult to work on. These areas of work-hardened metals may cause poor surface finishes, increased tool wear, and difficult chip removal. Preventing these problems involves proper control of heat by adopting the correct cutting speeds feeds and coolants.
3. Chip Control and Removal
Bronze machining produces long stringy chips that are not easy to clear during turning operation. These chips can lead to the formation of webs in the working area, produce tool vibrations, or mar the workpiece. To control chips, use the right chip breakers, coolants, and constant monitoring of the machines.
4. Surface Finish and Precision
To get a fine surface finish of bronze is difficult because the material tends to stick to the tool, and may transfer material to the tool edge. This may cause marks or imperfections on the part’s surface. Moreover, holding close tolerances on complex shapes as with most bronze materials that tend to work harden, may be very challenging and call for high-end machines, proper feeds, and speeds as well as constant tool changes.
5. Material Variability
Machining characteristics of various bronze alloys vary. So, there is a need to identify the right bronze type as per your project needs. Cutting speeds and tool selection depend on differences in tin content, alloying additives, and material hardness. Machining bronze is relatively intricate and calls for higher tooling levels and machine calibration. Conventional tooling can sometimes be unsuitable for bronze, especially with those containing high copper content.
6. Cost of Machining
Bronze CNC machining is generally more expensive due to high tool wear, low machining speeds, and frequent maintenance. The usage of special equipment, and tools and the high frequency of replacing worn-out tools and spares also result in the high machining cost of bronze parts. These costs must be controlled by design manufacturers to reduce their impact on the overall machining project budget.
Bronze Alloys Available for CNC Machining
Bronze alloys are very popular in CNC machining because of their high tensile strength, and resistance to corrosion and wear. Here are the most common types of bronze alloys used in CNC machining:
1. Tin Bronze (SAE 660)
- Composition: Copper and tin as well as small traces of lead, and phosphorus.
- Properties: Tin bronze has high wear resistance, strength, and corrosion resistance, particularly in marine and industrial areas.
- Machinability: It features excellent workability, however, its hardness tends to wear tools.
- Common Uses: Bearings, bushings, gears, and other friction and wear-resistant components.
2. Phosphor Bronze
- Composition: Copper, tin, and phosphorus.
- Properties: It is characterized by very high fatigue strength, spring characteristics, and non-corrosive, especially in marine applications.
- Machinability: It has better machinability than tin bronze but like most bronzes, it is likely to cause tool wear if the proper speeds are not used.
- Common Uses: Switches, sockets, springs, bushes, and bearings.
3. Aluminum Bronze
- Composition: Copper and aluminum, and may also contain small proportions of iron, nickel, or manganese.
- Properties: Aluminum bronze features high hardening ability and excellent anti-corrosive properties. Furthermore, it can work under high-temperature conditions.
- Machinability: Relatively harder than tin bronze and difficult to machine at times. It is necessary to use special equipment and cooling to minimize the degree of wear.
- Common Uses: Marine hardware, aircraft, and aviation equipment, and industrial products for varied industries.
4. Silicon Bronze
- Composition: Copper, silicon, with minor amounts of iron.
- Properties: It has good corrosion resistance, especially in salt water and in acidic medium, Silicon bronze has good weldability.
- Machinability: Silicon bronze is reasonably easy to machine compared to other bronze alloys; it is, therefore, suitable for CNC machining.
- Common Uses: Hardware for marine use, construction parts, and ornaments.
5. Copper-Nickel (CuNi) Bronze
- Composition: Copper and nickel, and sometimes iron.
- Properties: Copper nickels are also corrosion resistant, particularly in marine atmospheres, and possess high strength and toughness both at peak and low temperatures.
- Machinability: These alloys can be hard to machine and thus cutting tools and strategies need to be employed to get the best out of the cutting tool.
- Common Uses: Marine valves and pumps, marine propellers, and heat exchangers.
6. Leaded Bronze (Free-Cutting Bronze)
- Composition: Copper, tin, and lead.
- Properties: Leaded bronze is more machinable than other types of bronze because lead within the metal functions as a cutting aid during the machining operation.
- Machinability: Leaded bronze is easier to cut and also reduces the wear of the cutting tool.
- Common Uses: Large quantity components like bushes, bearings, gears, etc., particularly where dimensional accuracy is not a major concern.
7. Beryllium Bronze
- Composition: Copper and beryllium with possibly some traces of cobalt or nickel or other elements.
- Properties: Some of the properties that make it convenient for CNC machining include high strength and electrical conductivity.
- Machinability: Beryllium bronze, is known to provide good results in high-temperature applications, although it is relatively hard to work on, in terms of machining.
- Common Uses: Aerospace subassemblies, electrical contacts and connectors, and precision industrial products.
Key Considerations for CNC Machining Bronze:
- Tool Selection: The nature of the bronze alloy, particularly, its hardness determines the type of tools to be cut. Carbide tools are preferred when working with harder alloys, while HSS should be enough for working with softer alloys.
- Cutting Speeds and Feeds: The cutting speeds of the bronze types should be reduced to reduce the generation of heat that leads to work hardening. For harder alloys, a lower cutting speed and smaller feed are normally optimum.
- Cooling and Lubrication: Control of heat and surface finishes is done by the right flow and coolant circulation.
- Surface Finish: Surface roughness or lack of finish are important consideration where different materials are machined to produce a uniform surface finish since the harder alloys can stick to the tool imperfections.
Surface Finishes Available for Bronze Machined Parts
- Polished Finish
- Brushed Finish
- Bead Blasted Finish
- Anodizing
- Electropolishing
- Shot Peening
- Chemical Patina
- Sandblasting
- Coating and Plating
- Lapping
Summary: CNC Machining of Bronze
Bronze machining offers resilient components and products required for critical applications in the aerospace industry, automobile industry, and marine industry. However, machining bronze poses certain challenges, such as tool wear, tear, and heat generation. So, it’s advisable to choose the right cutting parameters and the correct type of tools to obtain desired finish, and measurements.
Are You Ready for Prototype with Bronze?
At Prototeque we offer high-quality bronze machined and other custom-made parts that fit your requirements. We welcome your quote request! If you have a project in mind or need a quotation, call us today!
