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What is CNC machining? Overview of CNC machining process

Back to list 发布日期:19年06 月18日 Source: Jindong Metal Products Release Date: June 18, 19

CNC machining is a manufacturing process in which pre-programmed computer software determines the movement of factory tools and machinery. This process can be used to control a range of complex machines, from grinders and lathes to mills and routers. With CNC machining, 3D cutting tasks can be completed in a set of prompts.

An abbreviation of "Computer Digital Control", the CNC process is contrary to-and thus replaced-the limitation of manual control. Manual control requires the on-site operator to instruct and instruct the machining tool through levers, buttons and wheels. To an onlooker, a CNC system may resemble a conventional set of computer components, but software programs and consoles used in CNC machining distinguish it from all other forms of computing.

Information about CNC machining

When the CNC system is activated, the required cutting is programmed into the software and determined by the corresponding tools and machines that perform the specified dimensional tasks, just like a robot.

In CNC programming, the code generator in a numerical system usually assumes that the mechanism is perfect, although there is a possibility of errors, as long as the CNC machine is instructed to cut multiple directions simultaneously, this is even greater. Tool placement in the CNC is outlined by a series of inputs called part programs.

Use a CNC machine to enter the program through the punch card. In contrast, programs for CNC machines are entered into a computer via a keypad. The CNC programming remains in the computer's memory. The code itself is written and edited by the programmer. Therefore, the CNC system provides a wider range of computing capabilities. Most importantly, the CNC system is by no means static because updated reminders can be added to pre-existing programs through revised code.

CNC machine tool programming

In the CNC, the machine is operated by digital control, where a software program is specified to control the object. The language behind CNC machining is called G code, and it is written to control various behaviors of the corresponding machine, such as speed, feed rate and coordination.

Basically, CNC machining can pre-program the speed and position of machine functions and run through repetitive, predictable cycles through software, all of which require little operator intervention. Because of these capabilities, the process has been adopted in all corners of the manufacturing industry, and is particularly important in the metal and plastics production sector.

For beginners, 2D or 3D CAD drawings are conceived and then converted into computer code for execution by CNC systems. After entering the program, the operator performs a trial run to ensure that there are no errors in the coding.

Open / closed loop processing system

Position control is determined by an open-loop or closed-loop system. For the former, the signal runs in a single direction between the controller and the motor. With a closed-loop system, the controller is able to receive feedback for error correction. Therefore, closed-loop systems can correct speed and position irregularities.

In CNC machining, the movement usually points to the X and Y axes. The tool, in turn, is positioned and guided by a stepper or servo motor, which replicates the precise motion determined by the G code. If the force and speed are minimal, the process can be run with open loop control. For everything else, closed-loop control must be performed to ensure the speed, consistency, and accuracy required for industrial applications such as metalworking.

CNC machining is fully automated

In today's CNC protocols, the production of parts through pre-programmed software is largely automated. Use computer-aided design (CAD) software to set the dimensions of a given part in place, and then use computer-aided manufacturing (CAM) software to turn it into an actual finished product.

Any given workpiece requires a variety of machine tools, such as drills and tools. To meet these needs, many machines today combine several different functions into a single unit. Alternatively, the installation may consist of multiple machines and a set of robotic hands that transfer parts from one application to another, but everything is controlled by the same program. Regardless of the setting, the CNC process allows for consistent, even if not impossible, manual copying of parts.

Types of CNC machine tools

The earliest CNC machines date back to the 1940s, when electric motors were first used to control the movement of existing tools. With the advancement of technology, these mechanisms are enhanced by analog computers, and finally by digital computers, thereby promoting the development of CNC machining.

Most CNC libraries today are completely electronic. Some of the more common CNC operations include ultrasonic welding, drilling, and laser cutting. The most commonly used machines in CNC systems include:

CNC milling cutter

CNC milling machines can run programs consisting of numbers and letters based prompts that can guide parts at different distances. Programming for rolling mills can be based on G-code or some unique languages developed by the manufacturing team. The base mill consists of a three-axis system (X, Y, and Z), but most new mills can accommodate three additional axes.

lathe

In a lathe machine, use indexable tools to cut parts in a circumferential direction. Adopting CNC technology, the lathe adopts high cutting precision and high speed. CNC lathes are used to produce complex designs, which is not possible in a manually run version of the machine. Overall, the control functions of CNC rolling mills and lathes are similar. As with the former, the lathe can be orientated by G code or unique proprietary code. However, most CNC lathes consist of two axes-X and Z.

Plasma cutting machine

In a plasma cutter, the material is cut with a plasma torch. This method is most importantly applied to metallic materials, but can also be used on other surfaces. In order to generate the speed and heat required to cut metal, a plasma is created by a combination of compressed air and an electric arc.

Electric spark machine

Electrical discharge machining (EDM)-alternatively known as die sinking and spark machining-is a process for molding a workpiece into a specific shape with electrical sparks. With EDM, a current discharge occurs between the two electrodes, which eliminates part of a given workpiece.

When the space between the electrodes becomes smaller, the electric field becomes stronger and therefore stronger than the dielectric. This allows current to pass between the two electrodes. Therefore, each electrode removes a part of the workpiece. EDM subtypes include:

Electrical discharge wire cutting, in which electrical spark erosion is used to remove portions from electronically conductive materials.

The EDM is settled, where the electrodes and workpiece are immersed in a dielectric fluid to form a sheet.

In a process called flushing, debris from each finished work piece is carried away by the liquid dielectric, which appears once the current between the two electrodes stops, and means any further charge is eliminated.

Water jet cutting machine

In CNC machining, water jets are tools for cutting hard materials such as granite and metals using high-pressure water applications. In some cases, water is mixed with sand or other powerful substances. Factory machine parts are usually formed through this process.

Water jets are used as a cooler substitute for materials that cannot withstand the heat-intensive processes of other CNC machines. As a result, water jets are used in a range of fields, such as the aerospace and mining industries, where the process is powerful for engraving and cutting as well as other functions.

Further application of CNC machine tools

As shown in numerous 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 CNC system include:

Embroidery machine

Wooden router

Turret punch

Wire bending machine

Foam cutting machine

laser cutter

Cylindrical grinding machine

3D printer

Glass cutting machine

When complex cutting at different levels and angles on a workpiece is required, it can be done in minutes on a CNC machine. As long as the machine is programmed with the correct code, the machine functions will perform the steps indicated by the software. Everything provided is coded as designed, and once the process is complete, details and technical value products will emerge.

CNC machine programming error

CNC machining is not a foolproof process. In some cases, the workpiece or the machine itself may be guided in a harmful manner. When this happens, a crash may occur, resulting in damage to tools or machine parts. Tools that may be damaged by a collision may include vise or clamps that hold the workpiece in place. When damage occurs in the machine, slight screw breaks and severe structural deformation may occur.

In fact, CNC equipment lacks the feeling of knowing exactly which distances are too far away. Therefore, the tools must be precisely programmed for trouble-free operation. If the program code is calculated incorrectly, the CNC machine may be driven beyond its physical boundaries and cause an internal collision. Although most CNC machines today are manufactured with parametric boundaries, these inputs can be manipulated by the operator.

Similarly, CNC tools ignore specific environments. Although some CNC machine tools are equipped with spindle load sensing, other CNC machine tools lack this feature. In the latter case, the software must be coded correctly to ensure that there are no parameters, otherwise a crash would be a possible result. Even if the CNC machine is equipped with a load sensor, a collision may still occur. When tool functions go astray, the operator corrects the situation.

Anti-collision of different types of CNC machine tools

By installing an encoder disc position sensor, the possibility of a collision can be detected in advance and prevented. Alternatively, a torque sensor can help determine if the CNC machine is moving as expected and detect unwanted cuts.

In a garage numerical control system, the tool relies on the rotation accuracy of the stepper motor to reach the correct degree. To monitor the tool position, the pulse into the stepper must be calculated, because in most cases there is no form of backup monitoring.

On industrial CNC machines, closed-loop control is used so that the controller always knows the axis position. If properly controlled, the chance of a crash is greatly reduced, but it remains the responsibility of the programmer to ensure that the code is entered accurately for safety.

Over the past two decades, CNC software has evolved to a variety of machine tools-axes, fixtures, fixtures, spindles, turrets-that can be accurately based on 3D solid models. Programming these specifications into code makes it easier to determine if a crash will occur at a particular cycle.