As a professional supplier of tobacco packaging machine parts, Hansheng Automation boasts its own CNC machining center, boasting a precision of ±0.002mm, achieving super-mirror-like finish. Next, I'll explore copper, a material suitable for CNC machining, drawing on our own machining practices.
What is copper?
To understand what copper is, we first need to answer the question, "What type of material is copper?" Copper is a naturally occurring, ductile transition metal with the chemical symbol Cu (derived from the Latin "cuprum") and atomic number 29. It is one of the few substances that can exist naturally in a metallic state and was one of the earliest metals used by humans.
What types of copper are there?
Copper isn't a single material type; instead, it's divided into two broad categories: pure copper and copper alloys. Each type offers optimized performance for specific CNC machining requirements.
Pure copper
This type of copper has a purity of ≥99.5%. The most commonly used grade in CNC machining is C110 electrolytic tough pitch copper, which boasts a purity of up to 99.9%. It exhibits excellent electrical conductivity (101.5% IACS, second only to silver), thermal conductivity (391 W/m-K), and ductility (elongation >45%, enabling drawing into ultra-thin wires as thin as 0.01mm). When CNC machining pure copper, it's important to note its high viscosity, requiring specialized tool geometry (such as a tool rake angle ≥25°) and TiAlN coating to prevent built-up edge.
Copper Alloys
This type of copper alloy is primarily created by adding elements such as zinc, tin, and lead to pure copper, enhancing its strength and machinability. Common types include:
Brass: A copper-zinc alloy (5%-45% zinc content). C360 brass (containing 2.5%-3.7% lead) is the benchmark for free-cutting copper materials. Its cutting index is based on 100% of 1214 free-cutting steel. Its cutting force is 40% lower than pure copper, and its tool life is three times longer, making it an ideal copper material for high-frequency CNC machining.
Bronze: A copper-tin alloy with outstanding advantages for corrosion resistance (especially seawater resistance) and wear resistance, making it suitable for machining marine engineering parts such as propeller bushings.
Oxygen-Free Copper (OFC): With a purity of ≥99.99% and an extremely low oxygen content, it is suitable for high-precision CNC parts (such as vacuum electronic components). Even trace impurities can affect its performance.
High-strength alloys: such as C194 copper-iron-phosphorus alloy and C195 copper-iron-zinc alloy, improve tensile strength while maintaining high conductivity (≥85% of pure copper), enabling miniaturized design of CNC machining electrical hardware.
What are the properties and performance of copper?
| Property Category | Specific Indicators (Pure Copper / Typical Alloy: C360 Brass) |
|---|---|
| Electrical Conductivity | Pure Copper: 101.5% IACS; C360 Brass: 25% IACS |
| Thermal Conductivity | Pure Copper: 391 W/(m·K); C360 Brass: 29 W/(m·K) |
| Corrosion Resistance | Pure Copper: Atmospheric corrosion rate < 0.005mm/year; C360 Brass: Seawater corrosion weight loss 40% lower than Pure Copper, no copper sulfide black spots in sulfur-containing environments |
| Ductility | Pure Copper: Elongation rate > 45%; C360 Brass: Elongation rate 23% |
| Machinability | Pure Copper: High viscosity, requiring special tools; C360 Brass: Cutting force is 60% of Pure Copper, chip length < 1mm, surface roughness Ra value 50% lower |
| Antibacterial Property | Both Pure Copper and Brass: Copper ions destroy microbial proteins, free radicals rupture cell structures, killing E. coli and Staphylococcus aureus |
| Mechanical Property - Strength | Pure Copper: Tensile strength ≈ 210MPa; C360 Brass: Tensile strength 140-350MPa |
| Mechanical Property - Hardness | Pure Copper: HB 35-45; C360 Brass: HB 65-75 (lead-reinforced) |
CNC machining process of copper materials
Select the appropriate copper material based on part requirements:
Conductive components (such as busbars): Choose C110 pure copper;
Parts frequently threaded (such as spools): Choose C360 brass (for high machining efficiency);
Marine connectors: Choose brass with a passivated surface treatment (salt spray life > 1000 hours).
Sawing or shearing the raw material into billets (blocks or rods) reduces machining waste; cleaning the billets removes oil and rust to prevent machining defects.
Import the CAD model into the CNC software and optimize the tool path based on the material properties:
Pure copper: Use a lower feed rate and higher spindle speed, and use TiAlN-coated tools.
C360 brass: Feed rates can be increased to twice that of pure copper, and use conventional carbide tools.
Roughing: Rapidly removes excess material. For pure copper, use a cutting fluid containing sulfur additives to prevent sticking. Brass can be dry-cut, achieving a surface roughness of up to Ra 0.8μm.
Finally: Use precision tools to calibrate dimensions and surfaces, ensuring part tolerances meet standards (e.g., ±0.005mm).
Deburring: Use tumbling or laser deburring, especially for small copper parts (e.g., pins) machined for CNC machining.
Anti-Oxidation Treatment: Pure copper parts undergo ultrasonic cleaning, passivation (chromate or benzotriazole coating), and vacuum packaging, ensuring a one-year oxidation-free life.
Inspection: Conductivity, dimensional accuracy, and surface quality are inspected to ensure compliance with standards.
Industries where copper products are used
Electronics and Electrical Industry
Primarily used in conductive connectors, motor rotors/stators, transformer windings, and heat sinks for mobile phones and laptops.
Automotive and Aerospace Industry
Automotive: Brass valves (self-lubricating, friction coefficient 0.08), pure copper power battery cables
Aerospace: Oxygen-free copper components (resistant to high-altitude corrosion), brass fasteners (lightweight yet high-strength).
Medical Industry
Commonly used in surgical instrument assemblies, medical device housings, and electrode pads, offering both biocompatibility and antimicrobial properties.
Marine and Construction Industries
Marine: Brass connectors (salt spray resistant), bronze propeller shaft bushings (seawater corrosion resistant)
Construction: Brass pipe fittings (precision threaded), pure copper roofing (durable and aesthetically pleasing).
Renewable Energy Industry
Used in wind turbine windings, solar panel connectors, etc., leveraging high conductivity to reduce transmission losses.
Is copper material safe?
Copper material is safe when used correctly and with necessary precautions, both during CNC machining and in its final application.
Machining Safety
Electrical Conductivity Risk: Copper is electrically conductive. Ensure CNC equipment is properly grounded to prevent electric shock during machining.
Cutting Fluid Protection: Sulfur-containing cutting fluids are commonly used when machining pure copper. Operators should wear gloves to avoid direct skin contact and maintain good ventilation in the machining area to prevent inhalation of volatile substances.
Application Safety
Antimicrobial Advantage: Copper possesses inherent antimicrobial properties. Medical components machined from copper via CNC processing help reduce microbial cross-contamination risks, outperforming certain plastic materials.
Usage Restrictions: Copper is generally unsuitable for direct food contact containers (e.g., uncoated) due to potential harm from excessive intake. For potable water components, copper alloy products with food-grade coatings should be selected.
FAQ
Q: What cutting tools and parameters are recommended for CNC machining of pure copper and C360 brass?
A: For pure copper, due to its high stickiness, select tools with a front angle ≥25° paired with TiAlN coating. Use cutting fluids containing sulfide additives to prevent built-up edge formation. For C360 brass-a commonly CNC-machined copper material-standard carbide tools suffice. Under dry cutting conditions, surface roughness can reach Ra 0.8μm, with feed rates achievable at twice that of pure copper.
Q: Why do copper alloys (like brass) crack easily during welding? How can this be prevented?
A: Cracking primarily results from low-boiling-point elements (zinc/lead) in copper alloys vaporizing during welding, causing porosity in the weld. Prevention methods: For brass welding, use TIG welding with pre-set silicon bronze wire (ERCuSi-A). For pure copper welding, preheat the base material to 400°C and use phosphorus-deoxidized copper electrodes (ECu). With proper execution, joint strength can reach 90% of the base material.
Q: How can surface oxidation and blackening be effectively prevented on CNC-machined pure copper parts?
A: Implement a three-step protective process:
① Ultrasonic cleaning to remove cutting fluids;
② Chromate or benzotriazole passivation to form a protective film (~0.5μm);
③ Vacuum packaging.
Q: Can C360 brass replace pure copper for high-precision conductive components (e.g., high-current connectors)?
A: No. Pure copper's conductivity (101.5% IACS) far exceeds C360 brass (25% IACS). Brass exhibits significantly higher temperature rise under high currents (>50A) and is only suitable for low-current signal applications (<1A) to reduce costs.
Q: What post-processing is required for copper parts used in marine environments to ensure durability?
A: Brass with surface passivation is the preferred choice. The zinc-based oxide film it forms can withstand over 1000 hours of salt spray testing. If pure copper is used, additional nickel plating is required to achieve equivalent performance, but this increases costs by 30%.
Disclaimer
Hansheng Automation cannot guarantee the absolute accuracy, completeness, or timeliness of all information on this page. All descriptions of performance parameters, geometric tolerances, design, materials, and processes are for reference only and should not be relied upon as a basis for decision-making. The final product specifications are subject to the contract between you and the third-party supplier.