The first NC machines were built in the 1940s and 1950s, based on existing tools that were modified with motors that moved the tool or part to follow points fed to the perforated tape system.[3] These early servomechanisms were quickly expanded with analog and digital computers, creating the modern CNC machine tools that have revolutionized machining processes.

Apart from being applied in machine tools to machine metals with high precision,[4]​ CNC is used in the manufacture of many other joinery, carpentry, etc. products. The application of CNC systems in machine tools has greatly increased production, while making it possible to carry out forming operations that were difficult to do with conventional machines, for example the creation of spherical surfaces while maintaining a high degree of dimensional precision. Finally, the use of CNC has a favorable impact on production costs by lowering the manufacturing costs of many machines, maintaining or improving their quality.[5]​.

Contenido

Se pueden utilizar dos métodos, la programación manual y la programación automática.

Manual programming

In this case, the part program is written solely through reasoning and calculations carried out by an operator. The machining program includes the entire set of data that the machine needs for the machining of the part.

The information as a whole that corresponds to the same machining phase is called a block or sequence and is numbered to facilitate its search. This set of information is interpreted by the command interpreter. A sequence or program block must contain all the geometric functions, machine functions and technological functions of machining. Thus, a program block consists of several instructions. The beginning of numerical control has been characterized by a chaotic development of programming codes since each manufacturer used their own. Subsequently, the need to standardize programming codes was seen as an essential condition so that the same program could be used for various machines as long as they were of the same type. The most commonly used characters, governed by DIN 66024 and 66025, are, among others, the following:

(The direction of rotation of the spindle is seen from behind the machine, not from our point of view as in conventional lathes).

Automatic programming

In this case, the calculations are carried out by a computer, based on data provided by the programmer, resulting in the part program in an exchange language called APT, which will later be translated by a post-processor) into the appropriate machine language for each computer control.

From the structural concept, a Computer Numerical Control (CNC) includes:[6]​.

An industrial controller performs the function of a combiner, such as: a microprocessor, on which an integrated system is based; a programmable logic controller or a more complex control device - an industrial computer. Modern combiners have greater precision and reproducibility, extended memory, high processing speed and improved diagnostics.

An important characteristic of a CNC combiner is the number of axes (channels) that it is capable of synchronizing (controlling). This requires high performance and related software.

Servo controls and stepper motors serve as actuators.

An industrial network is typically used to transfer data between an actuator and the machine control system.[7]​.

In CNC, a "shock" occurs when the machine moves in such a way that it is detrimental to the machine, tools, or parts being machined, sometimes causing bending or breaking of cutting tools, fixture clamps, vises, and fixtures, or causing damage to the machine itself by bending guideways, breaking drive screws, or causing structural components to crack or deform under stress. A minor crash may not damage the machine or tools, but may damage the part being machined and should be discarded. Many CNC tools have no inherent sense of the absolute position of the table or tools when turned on. They must be manually "reset" or "zeroed" to have some reference to work from, and these limits are only to determine the location of the part to work with and are not a strict movement limit on the mechanism. It is often possible to drive the machine outside the physical limits of its drive mechanism, resulting in a collision with itself or damage to the drive mechanism. Many machines implement control parameters that limit axis movement beyond a certain limit in addition to physical limit switches. However, these parameters can often be changed by the operator.

Many CNC tools also do not recognize anything about their working environment. Machines may have load sensing systems on the axles and spindles, but some do not. They blindly follow the provided machining code and it is up to an operator to detect if a lockup is occurring or about to occur, and for the operator to manually abort the active process. Machines equipped with load sensors may stop shaft or spindle movement in response to an overload condition, but this does not prevent a crash from occurring. It can only limit the damage resulting from the crash. Some locks may never overload any axis or spindle drive.

If the drive system is weaker than the structural integrity of the machine, then the drive system simply pushes against the obstruction and the drive motors "slide into place." The machine tool may not detect the collision or slip, so for example the tool should now be at 210 mm in the All future tool moves will have an error of -178mm in the This is common in open-loop stepping systems, but is not possible in closed-loop systems unless mechanical slip has occurred between the motor and the drive mechanism. Instead, in a closed-loop system, the machine will continue to attempt to move against the load until the drive motor enters an overload condition or a servomotor fails to reach the desired position.

It is possible to detect and avoid collisions by using absolute position sensors (optical encoder strips or disks) to verify that motion occurred, or torque sensors or power consumption sensors in the drive system to detect abnormal stress when the machine should be moving and not cutting, but these are not a common component of most hobby CNC tools. Instead, most hobby CNC tools simply rely on the supposed precision of stepper motors that rotate a specific number of degrees in response to changes in the magnetic field. The stepper motor is often assumed to be perfectly precise and never missteps, so tool position monitoring simply involves counting the number of pulses sent to the stepper motor over time. An alternative means of monitoring the stepper position is usually not available, so the detection of collisions or slips is not possible.

Commercial CNC metalworking machines use closed-loop feedback controls for axis movement. In a closed-loop system, the controller monitors the actual position of each axis with an absolute or incremental encoder. Proper programming of the control will reduce the chance of a crash, but it is still up to the operator and programmer to ensure the machine is operated safely. However, during the 2000s and 2010s, software for machining simulation has matured rapidly, and it is no longer uncommon for the entire machine tool envelope (including all axes, spindles, chucks, turrets, toolholders, tailstocks, fixtures, clamps, and stock) to be accurately modeled with 3D solid models, allowing the simulation software to predict fairly accurately whether a cycle will involve a shock. Although such simulation is not new, its accuracy and market penetration are changing considerably due to computer advances.[8]​.

The first NC machines were built in the 1940s and 1950s, based on existing tools that were modified with motors that moved the tool or part to follow points fed to the perforated tape system.[3] These early servomechanisms were quickly expanded with analog and digital computers, creating the modern CNC machine tools that have revolutionized machining processes.

Apart from being applied in machine tools to machine metals with high precision,[4]​ CNC is used in the manufacture of many other joinery, carpentry, etc. products. The application of CNC systems in machine tools has greatly increased production, while making it possible to carry out forming operations that were difficult to do with conventional machines, for example the creation of spherical surfaces while maintaining a high degree of dimensional precision. Finally, the use of CNC has a favorable impact on production costs by lowering the manufacturing costs of many machines, maintaining or improving their quality.[5]​.

Contenido

Se pueden utilizar dos métodos, la programación manual y la programación automática.

Manual programming

In this case, the part program is written solely through reasoning and calculations carried out by an operator. The machining program includes the entire set of data that the machine needs for the machining of the part.

The information as a whole that corresponds to the same machining phase is called a block or sequence and is numbered to facilitate its search. This set of information is interpreted by the command interpreter. A sequence or program block must contain all the geometric functions, machine functions and technological functions of machining. Thus, a program block consists of several instructions. The beginning of numerical control has been characterized by a chaotic development of programming codes since each manufacturer used their own. Subsequently, the need to standardize programming codes was seen as an essential condition so that the same program could be used for various machines as long as they were of the same type. The most commonly used characters, governed by DIN 66024 and 66025, are, among others, the following:

(The direction of rotation of the spindle is seen from behind the machine, not from our point of view as in conventional lathes).

Automatic programming

In this case, the calculations are carried out by a computer, based on data provided by the programmer, resulting in the part program in an exchange language called APT, which will later be translated by a post-processor) into the appropriate machine language for each computer control.

From the structural concept, a Computer Numerical Control (CNC) includes:[6]​.

An industrial controller performs the function of a combiner, such as: a microprocessor, on which an integrated system is based; a programmable logic controller or a more complex control device - an industrial computer. Modern combiners have greater precision and reproducibility, extended memory, high processing speed and improved diagnostics.

An important characteristic of a CNC combiner is the number of axes (channels) that it is capable of synchronizing (controlling). This requires high performance and related software.

Servo controls and stepper motors serve as actuators.

An industrial network is typically used to transfer data between an actuator and the machine control system.[7]​.

In CNC, a "shock" occurs when the machine moves in such a way that it is detrimental to the machine, tools, or parts being machined, sometimes causing bending or breaking of cutting tools, fixture clamps, vises, and fixtures, or causing damage to the machine itself by bending guideways, breaking drive screws, or causing structural components to crack or deform under stress. A minor crash may not damage the machine or tools, but may damage the part being machined and should be discarded. Many CNC tools have no inherent sense of the absolute position of the table or tools when turned on. They must be manually "reset" or "zeroed" to have some reference to work from, and these limits are only to determine the location of the part to work with and are not a strict movement limit on the mechanism. It is often possible to drive the machine outside the physical limits of its drive mechanism, resulting in a collision with itself or damage to the drive mechanism. Many machines implement control parameters that limit axis movement beyond a certain limit in addition to physical limit switches. However, these parameters can often be changed by the operator.

Many CNC tools also do not recognize anything about their working environment. Machines may have load sensing systems on the axles and spindles, but some do not. They blindly follow the provided machining code and it is up to an operator to detect if a lockup is occurring or about to occur, and for the operator to manually abort the active process. Machines equipped with load sensors may stop shaft or spindle movement in response to an overload condition, but this does not prevent a crash from occurring. It can only limit the damage resulting from the crash. Some locks may never overload any axis or spindle drive.

If the drive system is weaker than the structural integrity of the machine, then the drive system simply pushes against the obstruction and the drive motors "slide into place." The machine tool may not detect the collision or slip, so for example the tool should now be at 210 mm in the All future tool moves will have an error of -178mm in the This is common in open-loop stepping systems, but is not possible in closed-loop systems unless mechanical slip has occurred between the motor and the drive mechanism. Instead, in a closed-loop system, the machine will continue to attempt to move against the load until the drive motor enters an overload condition or a servomotor fails to reach the desired position.

It is possible to detect and avoid collisions by using absolute position sensors (optical encoder strips or disks) to verify that motion occurred, or torque sensors or power consumption sensors in the drive system to detect abnormal stress when the machine should be moving and not cutting, but these are not a common component of most hobby CNC tools. Instead, most hobby CNC tools simply rely on the supposed precision of stepper motors that rotate a specific number of degrees in response to changes in the magnetic field. The stepper motor is often assumed to be perfectly precise and never missteps, so tool position monitoring simply involves counting the number of pulses sent to the stepper motor over time. An alternative means of monitoring the stepper position is usually not available, so the detection of collisions or slips is not possible.

Commercial CNC metalworking machines use closed-loop feedback controls for axis movement. In a closed-loop system, the controller monitors the actual position of each axis with an absolute or incremental encoder. Proper programming of the control will reduce the chance of a crash, but it is still up to the operator and programmer to ensure the machine is operated safely. However, during the 2000s and 2010s, software for machining simulation has matured rapidly, and it is no longer uncommon for the entire machine tool envelope (including all axes, spindles, chucks, turrets, toolholders, tailstocks, fixtures, clamps, and stock) to be accurately modeled with 3D solid models, allowing the simulation software to predict fairly accurately whether a cycle will involve a shock. Although such simulation is not new, its accuracy and market penetration are changing considerably due to computer advances.[8]​.