CNC Basics , Users , and Feature

Date: 2024-06-03　‖　Author：FuDong Machinery

With the advancement of IT technology, manufacturing sites are also promoting IT and automation to improve production efficiency. One of the most automated methods for automating the machining process itself is “CNC (Computer Numerical Control)”. Machine tools equipped with CNC are called “CNC machine tools (CNC machines)” and are used in industrial parts manufacturing, etc. The advantage of CNC is that it can mass-produce products with stable quality and high safety.

Next, we will introduce the overview and use of CNC, the pros and cons of CNC, and the machining methods that can be achieved with CNC. 

• What is CNC?

CNC is the abbreviation of “Computer Numerical Control” or “Computerized Numerical Control”, that is, the use of a computer to numerically control a machine tool. By automating the movement of the machine (direction of movement, moving speed, processing volume, etc.) through programming, it is possible to produce high-quality products safely and efficiently. In the past, equipment such as milling machines and lathes were operated by human hands. However, this method can lead to problems such as “differences in the finished processed products for different workers”, “inability to process complex shapes”, and “inability to improve work efficiency”. These problems can be solved by automating the movement of the machine through digital control. Nowadays, many machine tools have introduced computer numerical control. In addition, if a CNC machine is combined with CAD and CAM, everything from design to machining can be done within the computer.

Uses of CNC machine tools:

CNC machine tools are widely used in various industries such as manufacturing parts for automobiles, medical equipment, aircraft, etc., and processing molds. It is especially suitable for precision machining that is difficult to achieve with general-purpose machine tools (non-CNC manual machines), such as free-form surface machining or three-dimensional shape machining. In addition, some machine tools can process not only metals, but also non-metals such as plastics and wood.

Difference Between CNC and NC:

A similar term to CNC is NC. NC is an abbreviation for “Numerical Control”, and unlike CNC, it does not contain the word “Computer”. What’s the difference? NC is a method of controlling the operation of a machine tool using only hardware, such as transistors or arithmetic circuits. This is a technology developed in the 50s of the 20th Century, which is usually controlled by a combination of multiple substrates, such as data reading substrates, computing substrates, and servo control substrates. In contrast, CNC replaces the control mechanism of NC with a computer (microcomputer). Software control of the operation of the machine using a dedicated programming language. However, in recent years, there have been many examples of NC equipment being installed with computers, so the difference between NC and CNC is gradually narrowing.

How to use CNC:

When machining materials using CNC, the work is carried out roughly according to the following steps.

• Use 3D CAD to create 3D data of your products
• Create NC program data in CAM
• Prepare the required tools and secure them on the tool holder
• Install the material on the processing table
• Start processing

CAD is a tool for creating 3D data, while CAM is an application for creating NC programs based on 3D data created by CAD. The NC program is a type of control in the form of a program, including tool speed and type, tool change time, tool path, etc. Use CAM to automatically create NC programs by entering tools and machining conditions. Even if you don’t have programming knowledge, you can use CAM to create NC programs and perform CNC machining work.

• Features of CNC

Next, let’s introduce the advantages and disadvantages of CNC.

• Advantages of CNC

Consistent quality:

When workers operate the machine manually, there may be deviations in the finish of the product. For example, a worker’s skills and proficiency may change the size and condition of a product, or a worker may mis-operate machines and produce waste products. Since CNC machine tools are automatically machined according to the program, relatively stable product quality can be achieved. Suitable for high-volume production, helping to reduce costs CNC machines are machined automatically by numerical control, reducing unnecessary workpiece movement and can often be machined faster than manual operations by workers. The advantage is that the processing time per piece is short, and the same product can be efficiently produced in large quantities.

In addition, only one monitoring device is needed when CNC machine tools work, and one worker can be responsible for the machining operation of multiple machines. What’s more, it can be completely unmanned without even monitoring. It is possible to produce more products with fewer workers, resulting in increased productivity and lower labor costs. 

High safety:

CNC machines can perform machining automatically, even when workers are not near the machine. Therefore, it has the advantage of being caught in the machine or having chips splashed out of the risk of injury. However, if used on a workpiece that does not fit the machine’s specifications (e.g., a rod-shaped material that is long enough to extend beyond the machine’s processing range), serious injury can occur, so the operating conditions of the machine must be carefully checked when operating. Combined with the ATC function, tool change can also be automated ATC is an abbreviation for Automatic Tool Changer, which is a device that automatically changes tools during CNC machining. Preset tools (e.g. milling cutters and drills) are automatically changed and machined according to NC programming. If it is combined with such a device, it is possible to continue machining automatically without stopping the machine, having the tool changed by the worker, and without the need to manage the process by another machine. At the same time, automatic tool change can also shorten the work time and achieve efficient machining.

• Disadvantages of CNC

Expensive equipment:

CNC machines are equipped with computers and software for digital control, in addition to the structure of manual machining operations. Therefore, it is much more expensive than traditional general-purpose machine tools, and the introduction cost is high, which is its disadvantage. 

In addition, it may be necessary to prepare a separate CAM in some cases. The introduction of this equipment should be considered only after it is determined that the investment will pay for itself. 

More Preparation before machining:

When using CNC machines for automated machining operations, it is necessary to carry out a lot of preparatory work, such as “mastering the knowledge of NC program preparation”, “writing and input of NC program”, “positioning of materials”, and “trial cutting of materials”. Since there is more preparation than a conventional general-purpose machine, a lot of preparation time is required before the first part is machined. The total operating time should be estimated taking into account the efficiency and extensive preparation required by automated machining.

• CNC Machining

There are a wide variety of CNC machines in the world. Once the NC machine is started, the machining is carried out automatically according to the program. Processing can be carried out even at night or early in the morning when there are no workers, which can improve work efficiency and productivity. It can also machine three-dimensional shapes with high precision, which is difficult to do with manual machining. Here are a few examples.

CNC Milling Machine:

A device that installs CNC functions on a milling machine is called a “CNC milling machine”. With CNC milling machines, milling (a method of cutting a fixed workpiece with a rotating tool) can be automated.

CNC Lathe:

CNC lathe is the equipment that automates lathe machining (the method of cutting rotating workpieces with a fixed tool). It is possible to automatically process segmented shafts, etc. There is also some equipment that can be processed in units of 0.001mm.

CNC Grinding Machine:

CNC grinding machine is a device that automates grinding (a method of cutting the surface of a workpiece with a high-speed rotating grinding wheel). The grinding wheel can be changed automatically and the grinding range can be controlled automatically.

Machining Center:

Machining center is also a type of CNC. In CNC machining machines, ATC is defined as “the continuous performance of multiple machining processes such as boring, milling, drilling, threading, and finishing by the same machine”. It is divided into various types by size, shape, and number of movable axes.

Others CNC Machining Machines:

“CNC laser processing machine” that utilizes the principle of light energy dissolution and “CNC water cutting machine” that uses the principle of high-pressure water jet cutting are also types of CNC machine tools.

• Summary

“CNC (Computer Numerical Control)” is the automatic operation of machine tools through computers. The direction of movement, movement speed, and amount of processing are programmed to reflect the movement direction into the machine and digitally controlled with high accuracy. Machine tools with CNC functions are called “CNC machines” and are widely used in many manufacturing fields, including automobiles and medical devices. With CNC machines, high-quality products can be stably mass-produced. The advantage is that workers are not required to be nearby, which can reduce injuries and accidents. However, the disadvantage is that the equipment is expensive and there is more preparation before processing. CNC machine tools do play a big role in improving machining efficiency and safety. On the basis of weighing the pros and cons, it should be analyzed how to choose it and general machine tools.     -END-