Computer numerical control

Computer numerical control (CNC) is a way to use computers to control machines that make things. It started from a system called numerical control, where machines were guided by things like punched cards. But CNC is easier to change and adjust, so it became more popular as computers got cheaper.

A CNC machine has tools and platforms that move by themselves. They follow instructions written in a special language called G-code. People can write these instructions, but usually, computer programs make them based on designs drawn using CAD software.

CNC machines are great for making the same thing over and over again because they work faster than machines controlled by hand. But they can be expensive and take time to set up. For small jobs or testing new ideas, a skilled worker might do better by hand while the CNC is getting ready.

In modern CNC, designs and instructions are mostly made by computers. The design is drawn with CAD, turned into steps with CAM, and then changed into commands the machine can understand. This makes sure every part made matches the design perfectly.

CNC machines can use many tools like drills and saws all in one setup, or parts can be moved between different machines. Either way, the process is mostly automatic and makes parts exactly as designed.

Description

In numerical control systems, the position of the tool is defined by a set of instructions called the part program. These systems can be either open-loop, where communication is only from the controller to the motor, or closed-loop, where feedback helps correct errors. Open-loop systems are cheaper but less accurate, while closed-loop systems are more precise and commonly used in commercial metalworking machines.

CNC machines use a three-dimensional Cartesian coordinate system to guide tool movements. This system helps map out the paths the machine needs to follow. Modern CNC systems are often enclosed for safety, and they can control many types of processes, including laser cutting, plasma cutting, and bending.

Coding

G-codes are special commands that tell a CNC machine how to move. For example, G01 makes the machine move in a straight line, while G02 and G03 make it move in a circle. M-codes are other commands that control things like turning the motor on or off, changing tools, and using coolant to keep the machine cool during work.

A typical CNC program starts with a percent symbol (%), followed by a name for the program like "O0001", and ends with another percent symbol. The program uses a mix of G-codes and M-codes to guide the machine through its tasks, ensuring everything runs smoothly and safely.

Examples of CNC machines

Computer numerical control (CNC) machines are special tools that use computers to guide their work. These machines can shape materials like metal, plastic, and wood very precisely. Some common types of CNC machines include lathes, which spin materials to cut shapes, and milling cutters, which remove material to create detailed designs. CNC machines are used in many industries to make parts for cars, computers, and even toys, making manufacturing faster and more accurate.

CNC machine	Description	Image
Mill	Translates programs consisting of specific numbers and letters to move the spindle (or workpiece) to various locations and depths. Can either be a Vertical Milling Center (VMC) or a Horizontal Milling Center, depending on the orientation of the spindle. Many use G-code. Functions include: face milling, shoulder milling, tapping, drilling and some even offer turning. Today, CNC mills can have three to six axes. Most CNC mills require placing the workpiece on or in them and must be at least as big as the workpiece, but new 3-axis machines are being produced that are much smaller.
Lathe	Cuts workpieces while they are rotated. Makes fast, precision cuts, generally using indexable tools and drills. Effective for complicated programs designed to make parts that would be unfeasible to make on manual lathes. Similar control specifications to CNC mills and can often read G-code. Generally have two axes (X and Z), but newer models have more axes, allowing for more advanced jobs to be machined. Most modern lathes have live tooling, allowing for limited milling operations to take place without having to remove the part from the lathe spindle. Second operations can be completed by using a sub-spindle, which is co-axial to the main spindle, but faces the other direction. This allows the part to be removed from the main spindle, and for additional features to be machined in the back side of the part.
Plasma cutter	Involves cutting a material using a plasma torch. Commonly used to cut steel and other metals, but can be used on a variety of materials. In this process, gas (such as compressed air) is blown at high speed out of a nozzle; at the same time, an electrical arc is formed through that gas from the nozzle to the surface being cut, turning some of that gas to plasma. The plasma is sufficiently hot to melt the material being cut and moves sufficiently fast to blow molten metal away from the cut.
Electric discharge machining	(EDM), also known as spark machining, spark eroding, burning, die sinking, or wire erosion, is a manufacturing process in which the desired shape is obtained using electrical discharges (sparks). Material is removed from the workpiece by a series of rapidly recurring current discharges between two electrodes, separated by a dielectric fluid and subject to an electric voltage. One of the electrodes is called the tool electrode, or simply the "tool" or "electrode", while the other is called the workpiece electrode, or "workpiece". EDM can be broadly divided into "sinker" type processes, where the electrode is the positive shape of the resulting feature in the part, and the electric discharge erodes this feature into the part, resulting in the negative shape, and "wire" type processes. Sinker processes are rather slow as compared to conventional machining, averaging on the order of 100 mm3/min, as compared to 8 million mm3/min for conventional machining, but it can generate features that conventional machining cannot. Wire EDM operates by using a thin conductive wire, typically brass, as the electrode, and discharging as it runs past the part being machined. This is useful for complex profiles with inside 90 degree corners that would be challenging to machine with conventional methods.
Multi-spindle machine	Type of screw machine used in mass production. Considered to be highly efficient by increasing productivity through automation. Can efficiently cut materials into small pieces while simultaneously utilizing a diversified set of tooling. Multi-spindle machines have multiple spindles on a drum that rotates on a horizontal or vertical axis. The drum contains a drill head which consists of several spindles that are mounted on ball bearings and driven by gears. There are two types of attachments for these drill heads, fixed or adjustable, depending on whether the center distance of the drilling spindle needs to be varied.
Water jet cutter	Also known as a "waterjet", is a tool capable of slicing into metal or other materials (such as granite) by using a jet of water at high velocity and pressure, on the order of 60,000 PSI, or a mixture of water and an abrasive substance, such as garnet powder. It is often used during the fabrication or manufacture of parts for machinery and other devices. Waterjet cutting is the preferred machining method when the materials being cut are sensitive to the high temperatures generated by other methods. It has found applications in a diverse number of industries from mining to aerospace where it is used for operations such as cutting, shaping, carving, and reaming. The thickness of material processable via waterjet machining is generally limited by the pressure of the waterjet, and by the dispersion of the jet as it gets further from the nozzle. Some waterjet cutters have a 5-axis cutting head, allowing for much more complex shapes to be cut, and to compensate for the angle of the kerf to leave the angled wall on the stock instead of on the finished part.
Punch press	Used to rapidly punch holes and cut thin materials. Such as sheet metal, plywood, thin bar stock, and tubing. Punch presses are generally used when a CNC mill would be inefficient or unfeasible. CNC punch presses can come in the C frame, where the sheet material is clamped onto a machining table and a hydraulic ram pushes down on the material, or they can come in a portal frame variant where bar stock/tubing is fed into the machine.

Other CNC tools

Many tools can be made better and more accurate with computer control, just like regular CNC machines. Some of these tools include 3D printing, drills, lathes, and even embroidery machines.

Other examples are laser cutting, glass cutting, and wood routers. All these tools can be guided by a computer to make very precise shapes and designs.

History

Main article: History of numerical control

The first NC machines were built in the 1940s and 1950s. These machines used tools that were moved by motors to follow points on punched tape. Over time, these machines were improved with computers, leading to the modern CNC machines that changed how things are made.

By the 2000s, CNC had become very important in making products. It is used not just for cutting and shaping materials, but also for many other types of machines. This helps make products better and faster. New ways of making things, like combining regular making with 3D printing, are also being developed. There is also a push to use AI and many sensors to make factories more flexible and smart.