Computer numerical control is the process of controlling machining tools like drills and lathes using a computer. The material that may be a composite, plastic, or wood piece is subjected to the programmed instructions without a manual operator and so it gets transformed into the final product. The CNC machine behaves as a manoeuvrable tool with motorised control.
The working mechanism of the machine
Generally, we operate the tool using a movable platform, which takes in specific instructions and is controlled by the computer. In this way, we have the CNC pattern making machines that we can use to make specific patterns for use in the commercial sector. A sequential program of machine control is the pattern for the instruction. This is fed to the piece of material and executed.
One person can write the entire program (such as G-code) and generate the same using graphics software such as computer-aided design (CAD). When we use 3D printers, we slice the part we need to print and then the instructions are generated. We can also use G-Code in this case.
Advantages of automation:
CNC affords a large variety compared to the non-computerised machining methods that use handwheels. Mechanically controlled cams find use as pattern guides. Automation helps improve the working and accuracy of the system. The workpiece is defined using CAD software that takes in manufacturing directives through the computer-aided manufacturing (CAM) software. The directives transform through post-processor software and these become specific commands needed by the machine. Using these commands, the machine changes the piece into the desired component.
We might need any number of tools in the CNC pattern making machines such as drills, saws, and so on, all the tools are combined into a single cell. In other cases, different machines are used with external controllers where the controllers might be human or robots. They move the component from the machine and so many steps might be needed.
Use of motors for motion control:
Motion is controlled in multiple axes and a tool spindle moves in the depth axis. Servo motors or direct drive stepper motors help control the position of the tool. We have a series of step-down gears in the older models. If we are able to maintain a small force limit open-loop control is maintained. We must also keep the speeds down to a small value. The metalworking machines in the commercial sector make use of closed-loop controls. This will provide good accuracy and speed for working on metals. It also helps when repeatability is in great demand.
Mill is the most commonly used CNC machine. In this, the program has specific numbers and letters that move the spindle or workpiece to various locations and depths. G-code is frequently used to do face milling, shoulder milling, drilling, and tapping. CNC mills can have 3-6 axes. Then there is a plasma cutter that uses a plasma torch that is used to cut steel and other metals. Gas comes out at high speed out of a nozzle, and an electric arc is formed through there gas from the nozzle to the surface being cut. In the process, some of the gas turns into plasma. The heat from the plasma cuts the metal and moves with great speed to blow the metal away from the cut.
