CNC (Computer numerical Control) is a technology for automatic operation of machine tools or other equipment by computer control. CNC machining is a reduced-material manufacturing process that creates a product by removing part of the material from the workpiece. The process uses the instructions generated by the CAD model for machining operations such as turning, drilling or milling.
What is CNC machining?
CNC machining is a “subtractive” manufacturing process that typically uses computerized controls and machine tools to remove layers of material from a blank (or workpiece) and produce a custom part.A CNC machine is not one specific machine, as it is a group of different types of CNC machines working on various machining processes. Some of the most popular CNC machining operations include:CNC Milling，CNC Drilling,CNC Grinding，CNC Routing etc.
Modern 5-axis milling machine making a cogwheel
The Different Types of CNC Machining
CNC Milling
CNC milling is one of the most popular types of CNC machining processes. In fact, many professional machine shops often use a CNC machining and CNC milling process interchangeably. Face milling and peripheral milling are two of the most frequently used CNC mill applications.
In a CNC milling machine, rotating cutting tools move relative to the workpiece to remove material.
The cutting tool (also called a milling tool) is fixed on a spindle that can rotate. The rotation and movement of the spindle give CNC milling machines the ability to perform three or more axes milling operations.
3-Axis CNC Milling machines
3-axis CNC machines can be moved along the X-axis (left and right), Y-axis (front and back) and Z-axis (up and down).
They are the most basic and common type of CNC machine tool. Suitable for processing relatively simple 2D and 3D parts, low cost.For parts requiring multi-angle processing, need to be installed multiple times, increasing the processing time and error.
4-Axis CNC Milling machines
The 4-axis CNC machine add a rotational axis to the 3-axis . In simple terms, the machine can go up and down, side to side, back and forth, and rotate along the X or A axes. All this happens without the workpiece moves. They are the most common CNC machines used in machining complex parts due to their speed, precision, and accuracy.
5-Axis CNC Milling machines
5-axis CNC machine tools add a rotating shaft to the 4-axis base, and can process any face and Angle of the workpiece in a single clamp, suitable for the manufacture of complex and precision parts, the structure and programming are extremely complex, requiring a high level of technical support and operators.The cost of a 5 axis cnc machine is usually higher.The dual-swivel milling head, as the core component of a five-axis milling machine, is priced around 4.5 million RMB, while a single-swivel milling head costs approximately 300,000 to 600,000 RMB. They can handle curves, angles and are the go-to for high-precision tasks.
CNC Milling Work Operations
CNC Drilling
The CNC drilling process is a lot simpler than using milling tools or the turning process. In CNC drilling, the workpiece is held stationary while a drill bit moves over the workpiece and creates holes.
The purpose of drilling holes might be to add screw bolts, counterboring, countersinking, reaming, tapping,and aesthetic requirements, or any other use.
CNC Grinding
CNC grinding machines use a rotating flat abrasive wheel for removing material from rough workpiece surfaces. This machine process is usually applied to create a smooth-finished part. The process involves the use of an abrasive wheel to remove burrs at high speed. The grains on the grinder wheel chips away at the work piece to achieve the desired shape.
CNC Turning(Lathes)
CNC turning is a subtractive manufacturing process in which pieces of material are rotated as a machine tool is fed to the piece, removing material to create a finished piece. It is primarily used to manufacture parts that are cylindrical in nature.
Electrical Discharge Machining
CNC Wire EDM (Electrical Discharge Machining) is a precision process that removes material using electrical sparks. A thin metal wire, usually made of brass or copper, acts as the electrode, generating discharges on the workpiece to cut the desired shape. There is no mechanical contact during the process,so it’s also called EDM Wire Erosion. It suitable for machining complex shapes and hard materials. It is commonly used for producing precision molds, blanking dies, and specialized parts. Wire EDM achieves high accuracy and surface finish, and Safewell provide wire EDM services because we have a wide range of needs for precision machining.
- Fast Wire EDM: High-speed wire movement (6-12 m/s) provides efficient cutting but with lower precision, around ±0.02mm, and surface roughness of Ra 1.5µm or more.
- Slow Wire EDM: Low-speed wire (0.2 m/s) delivers higher precision, reaching ±0.001mm to ±0.005mm, with surface roughness as low as Ra 0.1µm.
CNC Gear Manufacturing
To manufacture gears with high precision and complexity, it is essential to use CNC technology to control parameters such as the module size and pressure angle of the gear. Common CNC gear machining processes include CNC Gear Cutting, CNC Gear Shaping, CNC Gear Grinding, CNC Gear Hobbing, and CNC Gear Broaching. Safewell is a precision gear manufactures that can make the mechanical gears highly precise, of high quality, and meet complex design requirements. Below is a brief introduction to these processes:
CNC Gear Cutting
There are generally three methods for cutting: using a hobbing machine, milling machine, or broaching machine to cut gears. The most common cutting method is hobbing, where a hob continuously cuts the workpiece to form the gear teeth. CNC hobbing machines are particularly suitable for mass production of high-precision external gears. CNC Gear Broaching uses a broaching tool to progressively cut the gear teeth, and is suitable for manufacturing larger gears, especially those that are difficult to machine by other methods.
CNC Gear Shaping
Gear shaping is a process in which specially designed tools are used to form the gear teeth. The tool matches the final gear shape, making it ideal for machining internal gears and gears with complex shapes.
CNC Gear Grinding
Gear grinding is used to further improve the surface finish and precision of the gear. CNC gear grinding machines use grinding wheels to precisely refine the gear teeth, eliminating surface irregularities and errors.
Materials that CNC Machining is Used to Shape
Aluminum
Aluminum has an exceptional strength to weight ratio as well as thermal and electrical conductivity and protection against corrosion. It can easily be machined at low cost and is ideal for creating prototypes.
The variety of aluminum alloys used for CNC machining include:
- 2024 – Excellent strength and fatigue properties
- 5052 – Strong corrosion resistance, suitable for welding and molding parts
- 6061 – is the most commonly used.
- 6082 – is mostly used in Europe.
- 7075 – is used in the aerospace industry where there are concerns regarding weight. 7075 can be heat treated to increase its strength and hardness.
- 5083 – has exceptional strength and resistance to salt water and can be welded.
Stainless Steel
Stainless steel is a widely used metal in the CNC machining process due to its strength, ductility, and wear and corrosion resistance. It can be welded, machined, and polished and can be non-magnetic or magnetic.
Varieties of stainless steel that is used for CNC machining:
- 304 – is the most common stainless steel used.
- 316 – is another commonly used stainless steel. Unlike 304, it is resistant to the effects of saltwater.
- 2205 – has higher strength than other stainless steels and is used in harsh and severe conditions.
- 303 – has excellent toughness but low corrosion resistance.
- 630 or 17-4 – is capable of being hardened to 44Rc when heat treated and can withstand extremely high temperatures.
Alloy Steel
Alloy steel is produced using alloys aside from carbon to improve its hardness and toughness as well as its fatigue and wear resistance.
The types of alloy steels used for CNC machining are:
- 4140 – has excellent mechanical properties but is not suitable for welding.
- 4340 – unlike 4140, 4340 can be heat treated to increase its hardness and can be welded.
Brass
Brass is a metal alloy with machinability, electrical conductivity, and ideal for low friction applications. It is commonly used in architecture for decorative purposes since it has a pleasing appearance. Brass C36000 is the most common form of brass used in CNC machining due to its tensile strength and corrosion resistance. It is often used for high volume applications.
Polycarbonate
Polycarbonate is a tough thermoplastic that has machinability and extremely high impact resistance. It is transparent, which makes it ideal for fluidic instruments and the glazing of cars. An appealing feature of polycarbonate is its ability to be easily worked and shaped.
Inconel
Inconel alloys have been registered as a trademark brand by Special Metals Corporation for a set of alloyed metals that are nickel and chromium based. It is known for its ability to keep its structural integrity at high temperatures and resistance to oxidation. Inconel alloys are used in harsh and extreme environments. There are several Inconel alloys that include Inconel 625, Chronin 625, Altemp 625, Haynes 625, Nickelvac 625, and Nicrofer 6020.
Thermoplastics
There are a variety of thermoplastics that have sufficient strength and hardness to be shaped by using CNC machining. They are POM, known commercially as Delrin, Teflon or PTFE, and high density polyethylene (HDPE).
- POM – has very high machinability and is used for CNC parts that require high precision, stiffness, low friction, and dimensional stability.
- Teflon – has chemical and thermal resistance with a low friction coefficient. It is able to withstand temperatures of 200o C and is an excellent insulator flor electrical components .
- HDPE – has excellent impact resistance, a high strength to weight ratio, and weathering resistance.
