In machining operations, a cutting tool fed to the workpiece removes the material to shape it into a planned part.
Machining copper is challenging due to its tough nature that resists deformation. To increase the machinability of copper, they are alloyed with metals like aluminum, zinc, silicon, tin, etc., to make different machinable alloys of copper like brass, bronze, nickel-silver, etc.
This article discusses different copper machining techniques, things to consider while machining copper, applications, and some copper machining services.
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Machining Copper: How it's Done
Machining removes material from a workpiece to shape it into a specific part. It is primarily used to work on metals like steel, aluminum, brass, copper, etc.
Copper in its pure form is difficult to machine due to its high toughness and ductility.
So copper is alloyed with zinc, tin, and aluminum to improve its machinability. These alloys are then used for machining jobs.
Things to Consider When Machining Copper
The machining of copper depends on many factors, including the cutting technique, part geometry, tool, and machining conditions.
All the factors are interdependent, and you must test and optimize them to get a good output.
Optimizing The Part Design
Compared to other machined metals, copper is a valuable metal.
For example, a 2mm thick square copper block used for precision machining can cost anywhere between $18 - $30. The price varies based on their size.
So, it's essential to optimize the part's design and minimize the use of copper.
Only use it in part regions where the qualities of copper are essential. If the part needs to be a single piece, you'll have to make it entirely using copper.
Some common advantages of copper include good thermal conductivity, specific heat capacity, malleability, finish, etc. Consider them when optimizing the design.
Copper finds use in heat exchangers, parts of laser systems, electrical systems, etc.
Optical components are often fabricated using copper to maximize the intensity of the incident light.
Parts with holes or that need to be turned require a design that minimizes material wastage. You can have the part drawn or forged in such cases.
Choosing the right grade of copper
Based on the application of the part, it is vital to choose a suitable grade of copper.
Copper 101 and 110 are two commonly used grades. C101 is purer than C110 but has less machineability.
C110 offers better machinability and electrical conductivity when compared to C101. This makes it a better choice for machining copper parts like busbars for electrical systems.
C101 is only chosen to make critical parts that require maximum efficiency.
Since the C101 grade can be easily machined, you can use it to make small and complex copper parts.
C110 is the best option for turning jobs as it is more ductile than C101.
Working with Copper
The performance of machining copper depends on the parameters like the cutting tool used, speed, coolant, and feed rate.
Tools commonly used in machining copper are high-speed steels (HSS) and cemented carbides.
These tools are easier to grind and have high resistance to wear, hardness, and toughness. It helps improve the tool life and perform smooth machining jobs.
While machining, considering cutting speed is crucial as it affects the tool's life.
In the case of continuous machining (uninterrupted), the tool life of HSS tools is unaffected, but for the carbide tool, the cutting speed should be about 10% lower.
Copper can be machined with or without cutting fluid.
Based on the job and considering the need for uniform chip removal and heat dissipation, cutting fluid is used either as a coolant or a lubricant.
Emulsified oils are generally used when cooling is of prime concern. These oils have high specific heat capacity, making them an ideal coolant.
If lubrication is the primary concern, sulfur-free low-viscosity oil is the best as it is easy to deliver and remove from the machining area.
If the rate feed rate is high, there is a high chance of a temperature rise at the tool and workpiece interface, imparting a poor surface finish to the part.
Post-processing Copper Parts
Post-processing copper parts refer to imparting or improving surface finish to enhance its properties.
Commonly used surface finishing processes are anodizing, electropolishing, and electroplating.
These techniques help enhance the copper part's corrosion and chemical resistance by applying a coat of material.
Copper Machining Techniques
Copper can be machined manually on traditional machines or computer-controlled CNC machines.
CNC machining of copper is preferred as they deliver accurate and repeatable parts in less time.
Turning, milling, and drilling are the most used CNC operations. Other miscellaneous jobs include copper stamping, bending, etc.
In CNC turning, the copper workpiece is held by a rotating chuck, and the cutting tool is fed to the rotating workpiece.
The cutting tool traverses over the workpiece in longitudinal and transverse directions to remove the material, resulting in accurate parts with a good finish.
Choosing a lower feed rate is always recommended for optimum performance and smooth finishing.
Setting the tool at an appropriate angle also plays an important role. This, in turn, reduces thermal stress on the cutter and improves the cut.
In CNC milling of copper parts, the cutting tool moves along three or more axes depending on the machine configuration and complexity of the part.
You can perform various operations through CNC milling, like thread milling, end milling (to create grooves, slots, etc.), gear cutting, angular milling, etc.
CNC milling of copper is best when you want to make multiple complex parts accurately at a lower cost.
CNC drilling of copper involves cutting out a circular hole on them. Unlike CNC milling, the primary machine movement is along the Z-axis in CNC drilling.
Here, a rotating bit plunges into a clamped copper workpiece and cuts. Holes can be drilled over the entire width of the workpiece or partially (blind holes).
It is often adopted to produce threaded or tapped holes to provide a secure and tight fit for parts like screws.
Copper stamping is the process of using a press and a die to cut or form copper into the desired shape.
The press applies pressure, fording the copper sheet into the die, taking the shape of the die cavity.
Generally, electrical stamping is used for copper workpieces.
Applications of Copper Machining
Machined copper parts greatly benefit in making heat exchangers, radiators, bearings, gas welding nozzles, and plumbing components.
Excellent thermal conductivity and high corrosion resistance make copper a suitable material in the mechanical field.
Bus bars, electrical components, connectors, windings, and terminals are largely made using machined copper.
Also, its good electrical conductivity and non-magnetic nature make it eligible for a wide range of applications.
Copper Machining Services
If you face difficulty in machining copper or want to make complex parts with a better finish, it is good to avail a professional machining service.
Some of the most known copper machining service providers are listed below.
You can get better results while machining copper by choosing the right tool and cutting parameters.
Most importantly, your choice of copper alloys influences the machining process and the finish of the part.
Copper can be machined using different machines, but CNC machines help produce parts with good dimensional accuracy in less time.
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Frequently Asked Questions
Which material is easier to machine, copper or aluminum?
When compared to copper and aluminum, machining copper is relatively easy. Machining pure aluminum produces long chips that adhere to the cutting tools, hampering the machining process and affecting the part's surface finish.
What is the optimum cutting speed while machining copper?
The optimum cutting speed while machining copper depends on the machining technique adopted. The commonly adopted cutting speed for turning, milling and drilling processes is between 230 - 460 m/min.
Is machined copper parts fire-resistant?
Yes, machined copper parts are fire-resistant due to their high thermal rating. Hence, copper is often chosen over other materials for resisting high temperatures for specific applications. The alloys of copper have a melting point range of 1,675-1,981°F.
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