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How does CNC machining work? what can different type of CNC machine do

2021/5/9 9:05:17 click:

CNC machining is a manufacturing process in which pre-programmed computer software indicates the movement of factory tools and machinery. This process can be used to control a series of complex machines, from grinders and lathes to grinders and routers. Through CNC machining, 3D cutting can be accomplished in a set of prompts.

The abbreviation of "computer numerical control", the operation of numerical control process contrasts with the limitation of manual control, thus replacing the limitation of manual control. In manual control, real-time operators need to prompt and guide the commands of processing tools through levers, buttons and wheels. To bystanders, CNC system may be similar to a set of conventional computer components, but the software programs and consoles used in CNC machining make it different from all other forms of calculation.

CNC machining is a manufacturing process in which pre-programmed computer software indicates the movement of factory tools and machinery.

How does CNC machining work?

When the numerical control system is started, the required cutting is programmed into the software and assigned to the corresponding tools and machines, which perform the specified size tasks just like robots.

In the numerical control programming, the code generator in the digital system usually assumes that the mechanism is perfect. Although there is the possibility of error, the possibility of error is even greater when the numerical control machine tool is instructed to cut in multiple directions at the same time. The position of tool in CNC system is described by a series of inputs called part program.

On CNC machine tools, programs are input through punched cards. In contrast, the programs of CNC machine tools are input into the computer through the keypad. CNC programming is stored in computer memory. The code itself is written and edited by programmers. Therefore, the numerical control system provides a wider range of computing capabilities. Most importantly, the CNC system is by no means static, because the updated tips can be added to the pre-existing programs by modifying the code.

Programming of CNC machine tools

In the numerical control system, the machine is operated by digital control, in which a software program is specified to control an object. The language behind CNC machining is also called G code, which is written to control various behaviors of corresponding machines, such as speed, feed speed and coordination.

Basically, CNC machining can pre-program the speed and position of machine tool functions, and run them in repeated and predictable cycles through software, almost without operator's participation. Because of these capabilities, this process has been adopted in every corner of manufacturing industry, especially in the field of metal and plastic production.

Firstly, imagine a 2D or 3D CAD drawing, and then translate it into computer code for CNC system to execute. After the program is input, the operator conducts a trial run to ensure that there are no errors in the coding.

Open loop/closed loop machining system

Position control is determined by open-loop or closed-loop system. For the former, the signal is transmitted unidirectionally between the controller and the motor. For the closed-loop system, the controller can receive feedback, which makes error correction possible. Therefore, the closed-loop system can correct the irregularity of speed and position.

In CNC machining, motion usually points to X axis and Y axis. In turn, the tool is positioned and guided by a stepping motor or servo motor, which replicates the precise motion determined by the G code. If the force and speed are minimum, the process can be operated by open-loop control. For everything else, closed-loop control is necessary to ensure the speed, consistency and accuracy required for industrial applications such as metal processing.

In CNC machining, motion usually points to X axis and Y axis.

CNC machining is fully automated

In today's numerical control protocol, the production of parts by pre-programmed software is mostly automated. The size of a given part is set in place by computer aided design (CAD) software, and then converted into an actual finished product by computer aided manufacturing (CAM) software.

Any given workpiece may require various machine tools, such as drills and tools. In order to meet these requirements, many machines today combine several different functions into one unit. Or, an installation may consist of several machines and a set of robots that transfer parts from one application to another, but everything is controlled by the same program. Regardless of the settings, the CNC process allows consistency in the production of parts, which is difficult (if not impossible) to copy manually.

Different types of CNC machine tools

The earliest CNC machine tools can be traced back to the 1940s, when the motor was first used to control the movement of existing tools. With the development of technology, analog computer enhanced the mechanism, and finally digital computer enhanced the mechanism, which led to the rise of CNC machining.

Nowadays, most numerical control arsenals are completely electronic. Some common CNC machining processes include ultrasonic welding, drilling and laser cutting. The most commonly used machines in CNC system include:

CNC milling machine

CNC milling machine can run programs consisting of prompts based on numbers and letters, which guide workpieces through different distances. Programming for milling machines can be based on G code or some unique language developed by the manufacturing team. The basic milling cutter consists of a three-axis system (x, y and z), although most newer milling cutters can accommodate three additional axes.

Some common CNC machining processes include ultrasonic welding, drilling and laser cutting.

Turning machine

On the lathe, the workpiece is cut in the circumferential direction with a rotary cutter. Using numerical control technology, the cutting of lathe is carried out with high precision and high speed. CNC lathe is used to produce complex designs, which is impossible on manually operated machines. Generally speaking, the control functions of CNC milling machine and lathe are similar. Like the former, lathe can be controlled by G code or unique proprietary code. However, most CNC lathes are composed of two axes-X axis and Z axis.

Plasma cutting machine

In a plasma cutting machine, materials are cut with a plasma torch. This process is first applied to metal materials, but it can also be applied to other surfaces. In order to generate the speed and heat required for cutting metal, plasma is generated by the combination of compressed air and electric arc.

Electric discharge machine

Electrical discharge machining (EDM), also known as die sinking and EDM, is a process of forming a workpiece into a specific shape by EDM. In EDM, current discharge occurs between two electrodes, which will remove a given workpiece.

When the space between the electrodes becomes smaller, the electric field becomes stronger and therefore stronger than the dielectric. This makes it possible for current to pass between the two electrodes. Therefore, a part of the workpiece is removed by each electrode. Subtypes of EDM include:

WEDM, using EDM corrosion to remove parts from conductive materials.

Submerged EDM, in which electrodes and workpieces are immersed in dielectric fluid to form workpieces.

In a process called flushing, the debris on each finished workpiece is taken away by the liquid dielectric, and once the current between the two electrodes stops, the liquid dielectric will appear to eliminate any further charge.

Water jet cutting machine

In CNC machining, water jet is a tool for cutting hard materials (such as granite and metal) with high pressure water. In some cases, water is mixed with sand or other strongly abrasive substances. Factory machine parts are usually formed by this process.

For materials that can't bear the high heat processing of other CNC machine tools, water sprayer is a cold choice. Therefore, water jet is used in a series of industries, such as aerospace and mining, where the process is very effective for carving and cutting purposes, among other functions. Water jet cutting machines are also used in applications that require very complex cutting on materials, because lack of heat will prevent any changes in the inherent properties of materials that may be caused by metal-to-metal cutting.

CNC lathe is used to produce complex designs, which is impossible on manually operated machines.

What else can CNC machine tools do?

As shown by a large number of video demonstrations of CNC machine tools, this system is used to make very detailed metal cutting for industrial hardware products. In addition to the above machines, other tools and components used in the numerical control system include:

CNC machine tools at work

  • embroidery machine

  • Wooden router

  • Turret piercer

  • Bending machine

  • Foam cutter

  • Laser cutting machine

  • Cylindrical grinder

  • 3d printing

  • glass cutting machine

When a workpiece needs to be cut at different levels and angles, it can be finished in a few minutes on a CNC machine tool. As long as the machine is programmed with the correct code, the machine functions will perform the steps specified by the software. If everything is coded according to the design, once the process is completed, a product with details and technical value will appear.