What is CNC machining?


CNC machining is a very popular manufacturing technology in modern machinery manufacturing and parts manufacturing. This article will discuss the development history of CNC machining, the types of CNC machine tools, what CNC machining can do, how CNC programming, manufacturing technology, processing materials, tolerances and precision, processing characteristics, and application industry, and other dimensions to introduce what is CNC machining.

Contents of this article:

 

What is CNC machining?


CNC machining refers to a process method for machining parts on CNC machine tools. The process rules of CNC machine tool processing and traditional machine tool processing are generally consistent, but there have also been significant changes. A machining method that uses digital information to control the displacement of parts and tools. It is an effective way to solve the problems of various parts, small batches, complex shapes, and high precision, and achieve high efficiency and automated processing.

 

The history of CNC machining


The world's first electronic computer was born in 1946. Six years later, in 1952, computer technology was applied to machine tools, and the first CNC machine tool was born in the United States. Since then, the traditional machine tools have undergone qualitative changes. In 1948, Parsons was commissioned by the U.S. Air Force to develop processing equipment for the profile model of aircraft propeller blades. Due to the complex and diverse shapes of the templates and the high precision requirements, the general processing equipment is difficult to adapt, so the idea of computer-controlled machine tools is proposed. In 1949, with the assistance of the Servo Mechanism Research Office of the Massachusetts Institute of Technology, the company started the research on CNC machine tools, and in 1952, it successfully tested the first three-coordinate CNC milling machine modified from a large vertical copy milling machine. It began to be officially produced, and it was officially put into use in 1957. When manufacturing the frame of the aircraft and the rotating wing of the helicopter, the data processing of the wing processing path was carried out by using a fully digital electronic computer, and the tool diameter was considered to affect the processing path. As a result, the machining accuracy reached ±0.0381mm, which was the highest level at that time.

 

What are the CNC machine tools?


The commonly used CNC machine tools mainly include CNC lathes, CNC drilling machines, CNC milling machines, CNC grinding machines, and CNC machining centers.



CNC lathe

The CNC lathe is one of the most widely used CNC machine tools. It is mainly used for cutting inner and outer cylindrical surfaces of shaft parts or disc parts, inner and outer conical surfaces of arbitrary taper angles, complex rotating inner and outer surfaces, and cylindrical and conical threads, etc., and can perform grooving, drilling, reaming, reaming Holes and borings, etc. The CNC machine tool automatically processes the parts to be processed according to the pre-programmed processing program. We write the machining process route, process parameters, tool motion trajectory, displacement, cutting parameters, and auxiliary functions of the part into a machining program list according to the instruction code and program format specified by the CNC machine tool, and then record the content of the program list. On the control medium, it is then input into the numerical control device of the numerical control machine tool, thereby directing the machine tool to process the parts.
CNC turning



 

CNC drilling machine

CNC drilling machine is a digitally controlled hole processing machine tool mainly for drilling. Due to the development of machining centers, most CNC drilling machines have been replaced by machining centers. However, some parts with drilling as the main processing process still need to be processed by CNC drilling machines, such as processing printed circuit boards, so there is still a certain demand for CNC drilling machines. CNC drilling machine is mainly used for drilling, reaming, reaming, tapping, and other processing.


 

CNC milling machine

The CNC milling machine is automatic processing equipment developed on the basis of the general milling machine. The processing technology of the two is basically the same, and the structure is also somewhat similar. There is a big difference,   CNC milling machine generally consists of a CNC system, main transmission system, feed servo system, cooling, and lubrication system, CNC milling machine is divided into two categories without tool magazine and with tool magazine. Among them, the CNC milling machine with a tool magazine is also called a machining center.
CNC milling



 

CNC grinder

The CNC grinding machine is a machine tool that uses the grinding tool to grind the surface of the workpiece through numerical control technology. Most grinding machines use high-speed rotating grinding wheels for grinding, and a few use oilstone, abrasive belts, and other abrasives and free abrasives for processing, such as honing machines, and superfinishing machines, belt grinders, grinding machines and polishing machines, etc. CNC grinders include CNC surface grinders, CNC centerless grinders, CNC internal and external cylindrical grinders, CNC vertical universal grinders, CNC coordinate grinders, and CNC forming grinders.

 

CNC machining center

CNC machining centers are developed from CNC milling machines. The biggest difference from CNC milling machines is that the machining center has the ability to automatically exchange machining tools. By installing tools for different purposes on the tool magazine, the machining tools on the spindle can be changed through the automatic tool changer in one clamping to achieve a variety of machining. Function. CNC machining center is a high-efficiency automatic machine tool composed of mechanical equipment and a CNC system suitable for processing complex parts. The CNC machining center is one of the most productive and widely used CNC machine tools in the world. Its comprehensive processing ability is strong, the workpiece can complete more processing content after one clamping, and the processing accuracy is high. For batch workpieces with moderate processing difficulty, its efficiency is 5 to 10 times that of ordinary equipment, especially it can complete The processing that much ordinary equipment cannot complete is more suitable for single-piece processing or medium and small batch multi-variety production with complex shapes and high precision requirements. It concentrates the functions of milling, boring, drilling, tapping, and thread cutting on one device so that it has a variety of processing methods.
CNC machining center



 

What can CNC machining do?


CNC machining can cut complex shapes and high-precision parts and has high processing efficiency, suitable for small batch production.

 

How to program CNC machining?


CNC machining programming is one of the main contents in the preparation stage of CNC machining, which usually includes analyzing the part pattern, determining the machining process, calculating the tool path, obtaining the tool position data, writing the CNC machining program, proofreading the program and testing the part machining. CNC machining programming is divided into two methods: manual programming and automatic programming.

 

Manual programming

Manual programming means that all stages of programming are done manually. Using general calculation tools, through various trigonometric function calculation methods, the tool path calculation is carried out manually, and the instructions are compiled. This method is relatively simple, easy to master, and has great adaptability. Parts used for non-mold machining.

 

automatic programming

For parts with complex geometric shapes, it is necessary to use a computer to write the source program of the part using the specified numerical control language, and generate a machining program after processing, which is called automatic programming. With the development of numerical control technology, advanced numerical control system not only provides general preparatory functions and auxiliary functions for user programming but also provides means for programming to expand numerical control functions. The parameter programming of the FANUC6M CNC system is flexible in application and free in form. It has expressions, logic operations, and similar program flow of computer high-level language, which makes the machining program concise and easy to understand, and realizes functions that are difficult to achieve in ordinary programming.
Small batch parts manufacturing


 

CNC machining process


The CNC machining process is the sum of various methods and technical means used when CNC machine tools are used to process parts.
The contents of the CNC machining process include:
1. Select and determine the parts and contents for CNC machining;
2.Process analysis of CNC machining of part drawings;
3.Process design of CNC machining;
4.Mathematical processing and calculation of part drawings;
5.Write a processing program list;
6.Verification and modification of the program;
7.Write CNC machinings process files, such as CNC machining process cards and tool cards.


 

CNC machining materials
 


metallic material


The metal materials processed by CNC are aluminum, stainless steel, carbon steel, brass, bronze, and red copper.
metallic material



 

plastic material

The plastic materials processed by CNC are PP, ABS, PC, Nylon, Acrylic, PTFE, and PET.
plastic material



 

CNC Machining Manufacturing Tolerances and Accuracy


CNC machining accuracy is mainly used to produce products, and machining accuracy and machining error are terms used to evaluate the geometric parameters of the machined surface. The machining accuracy is measured by the tolerance level. The smaller the level value, the higher the accuracy; the machining error is represented by a numerical value. The larger the numerical value, the greater the error. High machining accuracy means small machining errors and vice versa. There are 20 tolerance grades from IT01, IT0, IT1, IT2, IT3 to IT18. Among them, IT01 indicates the highest machining accuracy of the part, and IT18 indicates that the machining accuracy of the part is the lowest. Generally speaking, IT7 and IT8 have medium machining accuracy. level.

 

CNC machining features


High precision


The CNC machine tool is processed according to digital instructions, and the backlash of the feed transmission chain and the lead screw pitch error can be compensated by the CNC device. Therefore, the CNC machine tool can achieve high machining accuracy.

 

high productivity

CNC machine tools can effectively reduce the time required for workpiece processing, including maneuvering time and auxiliary time. The adjustment range of the main oil speed and feed of CNC machine tools is larger than that of ordinary machine tools. Therefore, each process of the CNC machine tool can be selected as the most beneficial. The cutting amount of the machine, especially the CNC machining center using the automatic tool changer, can realize continuous processing of multiple processes on one machine tool, and the improvement of production efficiency is more obvious.

 

CNC machining application industry


CNC machining has strong advantages in the manufacturing industry and is widely used in the aviation industry, shipbuilding industry, automobile industry, mold manufacturing, power industry, and in the processing of small batch prototype parts.

 

aviation industry

The structure of parts in the aviation industry is typically characterized by thin overall thickness, complex shape, high precision of parts, and strict tolerances, and the design of parts in the aviation industry uses special materials such as aluminum alloys, high-temperature alloys, titanium alloys, high-strength steels, and composite materials. CNC machining technology can meet the parts manufacturing requirements of the aviation industry and perfectly fit the precision, tolerance, and complex shape of the parts.
 

auto industry

The application of CNC machining technology to the processing of auto parts can improve the manufacturing speed of complex parts and drive the speed of automobile manufacturing. The numerical control technology is easy to meet the needs of continuous replacement of parts and components, and is close to the production efficiency of rigid automatic lines of combined machine tools, enabling the production of large varieties and small batches. With its unique advantages, CNC technology makes the replacement of parts easier to achieve, so as to better meet the development of the automotive industry.
 

Small batch parts manufacturing

CNC machining technology is suitable for the manufacture of small batch prototype parts, which can process metal parts, plastic prototype parts, and prototype parts, suitable for small batch and complex parts manufacturing.
 

in conclusion


CNC machining plays an indispensable role in modern machining and parts processing. With the development of CNC technology, the machining accuracy of CNC machining technology, the complexity of the shape of parts, production efficiency, production environment safety, and other characteristics have been greatly improved. Processing technology will become more popular.