Before introducing computerised numerical control (CNC), the manufacturing process involved strenuous human labour, unnecessarily long periods of production, wastage of material, and was fraught with error. Today, technology has dramatically improved the manufacturing process.
The introduction of CNC machining technologies provides a high level of reliability, making iterative processes more automatic. But what is CNC machining? Which products can be made from CNC technology? How does CNC machining work, and which materials can be used in the manufacturing processes that use CNC machines?
This article is a deep-dive into what CNC machining is, and the basic concepts involved in the process. We will discuss CNC’s contributions to modern manufacturing and the advantages of CNC over traditional manufacturing.
WHAT IS CNC MACHINING?
CNC machining is a subtractive process that involves creating custom-shaped designs from a workpiece through computerised controls. The process is subtractive in that the product is manufactured by chipping material off an initial piece instead of adding material to make a product.
CNC machining can be described as a manufacturing process done by robots. The machines can run automatically without the need for a constant operator, which dramatically increases productivity.
WHAT IS THE HISTORY OF CNC MACHINING?
The predecessor of the CNC is numeric control (NC), a process described by the Society of Manufacturing Engineers as “marking the beginning of the second industrial revolution and the advent of an age in which the control of machines and industrial processes would pass from imprecise draft to exact science.”
CNC machining began as a punched tape-based technology in the 1940s and 1950s before quickly evolving to analogue and digital technologies in the 1960s.
John T. Parsons is considered the father of CNC machining. He developed numerical control, which is the principle that CNC machining is built upon. But even before Parsons, the machining technique had been invented in 1751. In 1952, Richard Kegg, in collaboration with the Massachusetts Institute of Technology (MIT), developed the first CNC milling machine.
WHAT ARE THE BASIC CONCEPTS OF CNC MACHINING?
To understand how CNC works, we need to understand some basic concepts.
Numeric Control
This denotes the automatic control of machine tools. These machine tools range from milling to welders, grinders, waterjet cutters, and hydraulic press machine.
Desktop CNC Machining
These are minimalist versions of CNCs and are better adapted for working on softer materials like wax, foam, and plastics. This type of machining uses smaller versions of CNC machines to make smaller products, mostly by hobbyists.
CAM
Computer-Aided Machining or Manufacturing (CAM) uses software to create code for running CNC machines. To work with a CAM system, you need three things:
- The first is software that instructs the machine regarding the directions it must move.
- You also need a machine that is capable of taking the instructions.
- Finally, you need to have a post-processing capability to turn the instructions into a language that the machines can understand.
NC Code
This is a basic yet unique computer language designed for a CNC machine to quickly understand and execute the NC code (commonly called the G-code). This is the language that the programmer uses to tell the machine how to manufacture something.
Postprocessor
A postprocessor is a translator that converts G-Code written for one CNC machine into code that can be understood and executed by another CNC machine.
HOW does CNC MACHINING WORK?
CNC machines operate by having their instructions programmed into software fed into computers using a small keyboard connected to the machine. The CNC system then carries out these programmed tasks in a similar fashion to robots.
WHAT ARE THE DIFFERENT TYPES OF CNC MACHINES?
Different CNC machines serve diverse purposes. Some of the most common types of CNC machines are mills, lathes, routers, plasma cutters, and LaserJet cutters. You can see more examples of the different types of CNC machines and what they do here.
WHAT CAN CNC MACHINES MAKE?
CNC machines can produce a diverse range of products from a wide range of materials, including metals, plastics, foam, and wood. As long as a material can be cut, CNC machines can be utilised for manufacturing products. The machines can be used to process surfaces, keyways, and other irregular shapes. Metal lathes can be used for machining round rods, threads and outer circles, and a drilling machine can bore holes.
CNC SOFTWARE
CNC software are application packages that write G-Code that a CNC machine can read. This software is called Computer-Aided Manufacturing (CAM) or Computer-Aided Design (CAD). This software is responsible for the numerical control of CNC machines. It helps to create designs that the computer program on the CNC machine can interpret.
The different types of CNC software have specific uses:
Computer-Aided Drawing (CAD): This is used to create 2D and 3D designs and technical documentation.
Computer-Aided Manufacturing (CAM): Allows users to set up work in branches to cater to multiple tasks like workflow, tool paths, and cutting simulations.
Computer-Aided Engineering (CAE): Are programs used throughout the development process during the pre-processing, analysis, and post-processing stages.
WHAT ARE THE ADVANTAGES AND DISADVANTAGES OF CNC MACHINING?
Just like any other technology, CNC machining comes with specific pros and cons. We look at some of them below.
Advantages of CNC Machining
CNC machining holds a significant cost advantage over traditional manufacturing in that it reduces labour costs. It drastically diminishes the margin of error in manufacturing. Moreover, it makes mass-manufacturing a much easier task than it has ever been due to its capacity to consistently deliver uniform outputs.
CNC also offers flexibility in design that allows the software to be quickly reprogrammed to create entirely new parts or correct mistakes.
Disadvantages of CNC Machining
A downside to CNC machining is the initial set-up cost. Companies may even need to take out loans to procure CNC technology. But, if the company can increase profits through CNC machining, that investment can be recouped quickly.
CNC machining lives off an assumption of the infallibility of computers. This means that some people using CNC machining systems may overlook the possibility of errors, making it easier for faults to slip through unnoticed. However, with proper training, this can be mitigated.
Lastly, because it is a subtractive process, CNC machining generates waste, which can have some adverse effects on the environment. Nevertheless, waste management processes can be put in place to ensure that the waste produced through manufacturing on CNC machines can be recycled.
HOW VITAL IS CNC MACHINING IN MODERN MANUFACTURING?
CNC machining ushered in a new form of modern manufacturing through its offerings of greater efficiency and precision, thereby offering significant improvements over conventional methods of modern manufacturing. This means that companies using CNC machining save on labour and time costs, increasing profitability in the long run.
CNC has also made processes such as fabrication (welding sheets of metal, shearing, punching holes, and flame-cutting) safer. It is an ideal option for fabrication because the machines are flexible and can be reprogrammed.
IS CNC BETTER THAN 3D PRINTING?
3D printing and CNC machining are both manufacturing methods. The critical difference between them is that CNC machining is a subtractive process, while 3D printing is an additive process. This means that the former creates products by chipping material from an original piece, while the latter creates the product by adding material.
Which is better between the two methods? It depends on several factors, such as the materials being used, the complexity of the parts, the skills of the employees, what is being created, and the financial considerations. Thus, one method could be excellent for a specific job and not another.
BECOMING A CNC MACHINIST
Prospective CNC machinists require some level of training and education to enter the profession.
What Skills do you Need to be a CNC Machinist?
CNC machinists require a minimum of a high school diploma or a General Educational Development (GED) before they can go on to acquire CNC-specific skills from technical schools. The GED is a set of tests used to determine whether an individual in the United States or Canada has high school-level academic skills.
CNC machinists, who have a certification from institutions like the National Institute for Metalworking Skills (NIMS), have an advantage over those without certification.
Where can I get Training to be a CNC Machinist?
People who write the programs that CNC machines follow are known as CNC Programmers, while those who attend the running of the machines on the shop floor are known as CNC Operators.
If you want to be a CNC programmer, you would typically spend much time as an apprentice or in a formal tertiary institution. CNC operators usually complete short-term courses, and gain most of their experience on the job. Many schools offer CNC-specific training.
IS CNC MACHINING RIGHT FOR MY PROJECT?
CNC machining is versatile, and its application spans many industries, including aerospace, agriculture, construction, printing, manufacturing, the military, and transportation. Thus, if your project requires a great amount of consistency, accuracy, and efficiency, CNC is your best choice.
WHAT IS THE FUTURE OF CNC MACHINING?
As technologies like artificial intelligence and machine learning become more popular, it is also expected that CNC machines’ popularity will increase. Even though some may be concerned that these sophisticated machines will take away jobs from humans, this is not usually the case when technologies improve, because they create more jobs in new areas.
The proliferation in the use of CNC machining will have benefits for both employees and manufacturers. For the former, processes are not as hard, and safety is enhanced. For the latter, profits will increase due to efficiency. Customers, on the other hand, will benefit from more quality products.
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