How CNC works
With a numerical control machine, programs are input via punch cards. By contrast, the programs for CNC machines are fed to computers through keyboards. CNC programming is retained in a computer’s memory. The code itself is written and edited by programmers. Therefore, CNC systems offer far more expansive computational capacity. Best of all, CNC systems are by no means static since newer prompts can be added to pre-existing programs through revised code. (xvi)
CNC machining makes it possible to pre-program the speed and position of machine tool functions and run them via software in repetitive, predictable cycles, all with little involvement from human operators. In the CNC machining process, a 2D or 3D CAD drawing is conceived, which is then translated to computer code for the CNC system to execute. After the program is input, the operator gives it a trial run to ensure no mistakes are present in the coding. (xvii)
Due to these capabilities, the process has been adopted across all corners of the manufacturing sector, and CNC manufacturing is especially vital in the areas of metal and plastic production. (xviii)
During the CNC manufacturing process, position control is determined through an open-loop or closed-loop system. With the former, the signalling runs in a single direction between the CNC controller and motor. With a closed-loop system, the controller is capable of receiving feedback, which makes error correction possible. Thus, a closed-loop system can rectify irregularities in velocity and position. (xix)
In CNC machining, movement is usually directed across X and Y axes. The tool, in turn, is positioned and guided via stepper or servo motors, which replicate exact movements as determined by the G-code. If the force and speed are minimal, the process can be run via open-loop control. For everything else, closed-loop control is necessary to ensure the speed, consistency and accuracy required for industrial applications, such as metalwork. (xx)
CNC and code
There are essentially two types of code used in CNC machinery (in broad terms) readable code and unreadable code. Readable code is the code created by humans where it is possible for the code to be generated, read and corrected by a human being. It is also possible for readable code to be generated by computer or software, but the important factor is that it can be edited or corrected by a human being to remove or correct mistakes. These will be code written in Python or Java, as well as other similar programs, or software created code such as G-Code and HPGL where the coder has access to the code and the ability to edit it. In G-Code for example, the program is created by the operators and is translated to the machine through a language called G-code. It is called this because most of the words and parts of the code start with the letter G. However, the G-code will vary from different machines and manufacturers.
G-code is a CNC programming language that directs a CNC machine’s functions related to the cutting tool’s movement. It stands for ‘Geometric code.’ G-code guides the CNC machine’s actions by combining instructions readable by the microcontroller. This simple programming language requires no intricate logic or mathematical skills. (xxi)
G-code programming is embedded in the firmware of nearly all machine tools, including CNC mills, lathes, and 3D printers. While specific languages may vary between manufacturers, they generally adhere to the same principles, with most codes remaining consistent. Understanding G-code for CNC machines is not complex. It is straightforward to comprehend the basics, workings, and the creation of G-code for your next project. Continue reading to explore everything about G-code for CNC machines. (xxii)
A G-code file is plain text; it’s not exactly human readable, but it’s pretty easy to look through the file and figure out what’s going on. G-codes tell the controller what sort of motion is desired. (xxiii)
Then there is unreadable code. This is code which is generated by a software application for reading and interpretation by another device. The code cannot be read by a human and errors can only be corrected at source or in the design process. Think of creating a design on the computer, then sending it to a printer where the printer has to output it. The code that is generated by the computer is known as the RIP file or the raster image processor file. This file cannot be read or edited once generated and is only used by the printer to output the desired image. If errors are present in the design file (whether obvious or not), the RIP file will also contain those errors and the errors will be output as such or, not output if the file cannot be read by the printer.