Machining

Machined items in copper, brass, bronze, nickel silver, alubronze or other copper alloys are important building blocks in our everyday life; From the fittings in your kitchen to bearings in large machines or bus bars in wind turbines.

Choosing the right alloy

As a rule of thumb, hard alloys are more suitable for machining, because the chips are short and brittle. A soft alloy will produce long, soft chips that get in the way of machining and can get stuck in the tool.

Overall, brass is one of the most suitable materials for machining. In the “machining index”, the brass alloy CW614N is index 100, i.e. the most suitable of all metal alloys for machining.

Lead and machining

Copper-lead alloys (often bronze and brass alloys) are much more suitable for machining than pure copper. Lead creates shorter and more brittle chips that are less likely to get in the way of machining.

However, lead is harmful to human health, and the metal is slowly being phased out of our lives. As part of this phase-out, the use of lead is limited under the EU's RoHS- and REACH legislation.

Fortunately, several new alloys have been developed to minimise lead content and maximise machinability. One example is the brass alloy CW724R with a maximum of 0.1% lead, which is RoHS and REACH compliant.

Turning and milling

Brass is by far the most machinable copper alloy. But if you know the properties of each alloy, you can get good results with copper and bronze alloys as well.

Pure copper is not only soft, but also great at absorbing heat, which softens the material further. To machine a part accurately, you need to watch the speed of machining and use a generous amount of lubricant to reduce friction and keep heat generation as low as possible. If the part becomes to warm, the copper can get stuck in the tool.

Bronze alloys, on the other hand, can be relatively hard and brittle and can contain stress. This poses the opposite challenge: The part can crack from temperature differences within the metal during machining. The cure for this is also to watch your speed and be generous with lubricant to reduce heat generation.

Punching

Punching is an effective way to create holes in copper and brass. One of the uses for punching is when producing busbars for electrical distribution systems.

For punching, the alloy should be soft, but not too soft. If the alloy is too hard, the material may crack, and if it is too soft, a clean cut is hard to obtain.

When punching, it is important to pay attention to how the material moves on impact. Punching too close to the edge will push the material out and create visible dents at the edge.

The alternative to punching is drilling. Drilling makes for a better result with no risk of dents, but the process is more expensive.

To find the best solution for your project, we always recommend that you consult with Alumeco or your subcontractor about the specific project – especially if the part will be bent after punching. We can help you come up with a design that is optimised for machining.

Waterjet cutting and laser cutting

Waterjet cutting and laser cutting are widely used methods for cutting thin copper sheets quickly and efficiently. Both methods offer a lot of freedom in cutting.

However, when laser cutting, be aware that copper can reflect the laser beam back into the machine – to avoid this, we recommend that you always consult with the manufacturer of the laser cutter before laser cutting copper.

Bending and cold forming

In general, copper and brass alloys are very suitable for cold forming such as bending and deep drawing. This is why copper and brass are traditionally used for cartridge cases, which require extreme deep drawing, and other special components, e.g. for thermostats.

For deep drawing, we recommend choosing DDQ (deep drawing quality) material, which is particularly suited for deep drawing. The softer and thinner the material, the more it can be bent, twisted and drawn.

Rules of thumb for bending radius

There are no official guidelines for the proper bending radius on copper alloys. But these general rules of thumb can help you avoid surface cracking:

If your bending radius is too small, you may see cracks in the surface:

Additional components

You can buy copper parts with pre-assembled add-on components such as press nuts or insulation. The items are ready for installation with no need for machining.

Copper welding

Copper and brass parts are suitable for welding, but their high thermal conductivity can pose a challenge. To mitigate the issue of heat dissipating into the material too quickly, the workpiece should be preheated. This makes it easier to retain sufficient heat in the welding area to keep the welding temperature high enough.

When choosing your alloy for a welding project, you should look for a low-oxygen alloy. We recommend CW008A (Oxygen Free) or HCP/DHP (CW021A/CW024A).

An alloy such as ETP (CW004A) is not low-oxygen. During welding the oxygen will be converted to water, which can cause hydrogen embrittlement.

Press welding

Press welding is a unique welding method for copper. With this method, thin laminate strips can be welded together into a solid block using pressure and high temperatures. This provides a seamless transition phase between the solid copper terminal and the flexible lamels.

As with conventional welding, HCP and DHP (CW021A and CW024A) are common alloys used for press welding.

TIG and MIG welding

Oxygen and hydrogen from the surrounding air can interfere with the welding process, which is why you need a shielding gas when welding copper. And, as mentioned previously, the material should be pre-heated before welding to maintain a sufficiently high temperature throughout the weld. The most common methods of copper welding are TIG and MIG welding.

TIG is short for Tungsten Inert Gas and uses a tungsten electrode. TIG is a handheld welding method, which makes it easy to control and to achieve a neat finish.

MIG is short for Metal Inert Gas and is an automatic welding method. The method is significantly faster than TIG welding, but less precise.

Braided and stranded copper

Copper has a unique ability to be drawn into incredibly thin wires (0.2 mm). This is a great advantage for electrical applications because it allows for very flexible parts.

Braided or stranded items are produced by braiding or twisting several hundred or thousands of individual wires together. In both cases, 1600 wires provide a cross-section of approximately 50 mm².

What is the best option?

Stranded wires are widely known from wires, cables and other industrial applications. This method creates a strong wire that can withstand repetitive bending and movement in all directions. Stranded busbars are typically more break-resistant than braided busbars, while braided busbars are typically more flexible.

Braided wire is produced in a cylindric shape that can be pressed flat. Stranded wire will usually be produced in a solid round shape that cannot be altered.

Both types come with advantages and disadvantages, and the best solution depends on the specific installation.

Brazing and soldering

Brazing is widely used with copper and copper alloys, e.g. for the production of heat exchangers and the assembly of electrical components.

The process requires a flux, e.g. another copper alloy with a lower melting point than the two items to be joined. The molten flux reacts with the surface of the two items so that they solidify together into one material.

Soldering is particularly suitable for applications where the material is either too thin for welding or there is no room for welding. In the plumbing industry, soldering is especially used for installations of pipes, e.g. in private homes.