CNC (Computer Numeric Control) machining covers a wide range of technologies and techniques. Broadly defined, the machining technique involves shaping a workpiece using machine tools according to a predetermined form. Most – if not all – components and metallic pieces require a certain kind of machining over the course of their manufacturing process. Other materials – such as plastics, rubber, wood, and paper products – are also commonly manufactured using machining. Let’s review the most widespread machining techniques.
- Boring: Boring tools are generally used at the end of the process to enlarge the holes previously cut in the material.
- Cutting: Devices such as saws and shears are typical examples of cutting tools. They’re often used to cut materials (such as sheet metal) into predetermined dimensions and desired shapes.
- Drilling: This category includes double-edged rotating devices that create round holes parallel to the axis of rotation.
- Grinding: These instruments apply a turning wheel to obtain a fine finish or to make slight cuts on a workpiece.
- Milling: A milling tool uses a rotating cutting surface with several blades to create non-circular holes or to cut specific patterns.
- Turning: These tools turn a workpiece on its axis while a cutting tool gives it a specific shape. Lathes are the most common type of turning tool.
Besides mechanical machining, there are also techniques that use heat to machine a workpiece. The most common types of welding and burning used in machining are the following techniques.
- Laser cutting: A laser emits a narrow, high-energy beam of light that melts the material. CO2 and Nd:YAG lasers are the two types of lasers most frequently used in machining. The advantages of laser cutting include high-quality finishes and extreme precision.
- Oxy-fuel cutting: Also known as gas cutting, this machining process uses a mixture of combustible gas and oxygen to melt and cut various materials. Acetylene, hydrogen, and propane often serve as the gaseous environment here due to their high flammability. The main advantage of this method is its ability to cut thick or hard materials, such as steel.
- Plasma cutting: Plasma torches use an electric arc to transform inert gas into plasma. This plasma reaches extremely high temperatures and is applied to the workpiece at high speed to melt the undesirable material. The process is often used on electrically conductive metals that require a very precise cutting width.
While burning tools use heat, erosion machining techniques, for their part, use water or electricity to erode the material of the workpiece. The two main types of erosion machining technologies are the following:
- Water jet cutting: This process uses a high-pressure water jet to cut the material. An abrasive powder can be added to the water jet to facilitate the erosion. Water jet cutting is usually used on materials that have been previously deformed by the effects of heat.
• Electrical discharge machining (EDM): Also known as electro-erosion machining, this process uses electrical discharges to create micro-craters that quickly lead to complete cuts. This machining technique is used in applications that require complex geometric shapes in hard materials with low margins of tolerance (that is to say, less than 0.0005 mm, as a general rule). In addition, electro-erosion requires that the base material be electrically conductive, which limits its use to ferrous alloys.