Copper CNC Machining

When turning copper on a lathe, it is important to grind the copper cutting tool properly. Considering that copper tends to stick to the tool during processing, a crucial aspect of the machining process is to ensure a large front angle and a chip groove greater than 5mm, with a depth ideally between 2mm to 3mm. This approach minimizes heat generation during the machining of copper, resulting in smooth and polished surfaces.

Copper is highly prone to oxidation and discoloration. Using common cutting fluids can lead to a chemical reaction with copper, resulting in greenish discoloration and black spots on the surface. To prevent this, it is recommended to use cutting fluids specifically designed for copper, containing anti-oxidation and anti-rust properties to prevent oxidation during and after the machining process.

Products processed from copper include CNC milling and engraving machines, CNC lathes, core-walking machines, automatic lathes, turning, stamping, stretching, tubing, shafts, axles, copper and iron sleeves, aluminum sleeves, copper columns, copper needles, probes, rivets, pins, threaded inserts, nuts, threaded rods, nozzles, spray nozzles, oil nozzles, wind nozzles, air nozzles, connector shaft bases, ball joints, shaft connectors, spring-tipped positioning pins, adjusting rods, flange covers, rivet cones, brackets, pin connector nut, copper nut, non-standard custom hardware parts.

Recently, many online discussions have taken place regarding the raw material for copper flexible connections, specifically copper, also known as T2 copper. Surprisingly, there are several types of T2 copper. T1, T2, and T3 are the three grades of copper, which appear similar and cannot be distinguished with the naked eye; professional testing equipment is required for differentiation.

These three types of materials have different copper contents, which is the fundamental distinction:

T1: Copper content is 99.95%

T2: Copper content is 99.90%

T3: Copper content is 99.70%

Their melting points slightly differ, and their electrical conductivity and resistivity also vary. T1 has the highest copper content, while T3 has the lowest. The choice of which type to use depends on the specific application and requirement.

When grinding your own tools for machining copper, it’s beneficial to have a larger back angle to enhance tool sharpness. Polishing of the front cutting surface is essential. For pointed ends, a slightly smaller point angle is preferred for better machining results.

The characteristic of long and unbroken chips in copper requires a smooth front cutting surface on the machining tool to reduce friction between the chips and the tool. This is crucial for improving tool life and machining quality.

In machining copper using a CNC engraving machine, the cutting line speed does not significantly impact tool life. Thus, the spindle speed can be adjusted within a considerable range. Generally, a flat-bottomed cutter is used at a spindle speed of around 14,000 (rpm).

The length of the tool protruding should be kept as short as possible, or a thicker tool holder can be used to increase tool strength and reduce deformation during machining, which significantly affects the surface finish of the workpiece.

For precision machining with a ball-end cutter, the intersection of the two edges of the cutter should be thin to ensure sharpness and reduce friction during machining, especially in areas with small curvature for better results.

For turning copper on a CNC lathe, suitable copper cutting tool s include hard alloy (carbide) tools, high-speed steel (HSS) tools, tungsten steel tools, vertical tools, multi-blade tools, and PVD-coated tools. The choice of tool depends on factors such as turning process, cutting speed, processing conditions, workpiece shape, and machining accuracy requirements. Hard alloy tools are recommended for efficient and high-speed, deep-cut, and high-feed turning processes. High-speed steel tools, although less expensive, are suitable for small-batch, medium-low-speed, and small-feed turning processes. Tungsten steel tools are ideal for high-hardness metal materials like copper, providing fast cutting speed and longer tool life, though they are relatively more expensive. Vertical tools are versatile for various metal materials, including copper. Multi-blade tools are commonly used for turning copper, enabling multiple different types of machining processes in a single cut and improving processing efficiency. PVD-coated tools are prepared using physical vapor deposition technology, forming a thin film on the tool surface, providing excellent wear resistance and anti-oxidation performance, enhancing cutting speed and tool life, suitable for high-precision and high-speed machining. Nickel-based alloy tools have high hardness and excellent wear resistance, capable of withstanding high temperatures, making them suitable for cutting difficult-to-cut metals like copper. Apart from choosing the appropriate tool, other methods can make copper easier to cut, such as using a lubricant during cutting to reduce friction and heat and improve cutting efficiency and tool life. In summary, the choice of tool should be based on a specific analysis of the actual situation. Hard alloy tools are suitable for high-efficiency, high-speed, deep-cut, and high-feed turning processes, while high-speed steel tools are suitable for low-efficiency, medium-low-speed, and small-feed turning processes. Select the appropriate tool according to the actual situation to improve processing efficiency, machining accuracy, and reduce the number of tool changes and costs.

Copper has low strength and hardness, resulting in a low cutting load during turning, allowing for sharper copper cutting tool s. However, due to its high plasticity and toughness, the chips are not easily broken, resulting in chip lumps during turning, intensifying tool wear and affecting the surface quality of the workpiece. Additionally, copper has a high linear expansion coefficient, and the workpiece undergoes thermal effects during turning.

The main reasons include improper tool selection, unreasonable setting of processing parameters, and inadequate operational skills. Therefore, extra care and precision are required when turning copper.

Attention should be paid to proper tool selection and assembly, reasonable setting of processing parameters, stable clamping of the workpiece, and maintenance of the machining environment. Regular equipment maintenance and upkeep are also necessary to ensure machining accuracy and stability.

Standards for copper products include:

Seamless copper tubes for air conditioning and refrigeration equipment (GB/T 17791-2007)

Seamless copper tubes for cables (GB/T 19849-2005)

Seamless round copper tubes for conductivity (GB/T 19850-2005)

Oxygen-free copper tubes for magnetrons (GB/T 20301-2006)

Seamless internally threaded copper tubes (GB/T 20928-2007)

Laser cutting of copper is an efficient and precise processing method that can complete complex cutting tasks in a short time. However, to achieve the best cutting results, it is essential to set the cutting parameters appropriately.

Based on information about laser cutting parameters, the parameters for laser cutting copper include laser power, cutting speed, gas flow rate, and focal length. For most copper materials, the recommended laser power range is 1500-3000 watts. The cutting speed for copper is suitable between 1-2m/min. The focal length, if too large or too small, can affect the cutting quality, and the gas flow rate, if too large or too small, can also affect the cutting effect. Therefore, adjustments should be made based on specific circumstances.

Copper is industrial-grade copper with a melting point of 1083°C, no allotropic transformation, a relative density of 8.9, and a density five times that of magnesium.