Elements of an Industrial OEM CNC controller

Different Industrial OEM CNC controllers are available in the market with varying basic hardware configurations, but their fundamental working principles are generally the same. Some controllers are specifically designed to work only with a particular CNC system. Companies like SIEMENS, FANUC, MITSUBISHI, YASKAWA, HEIDENHAIN, and REXROTH manufacture popular controllers, each with different models. Among these companies, FANUC and SIEMENS have the highest-selling controllers and are market leaders in the machinery industry. Depending on the design and type of controller, sometimes the PLC and motor driver units function together as a standard enclosed arrangement, while other times they operate as separate components that coordinate with an external controller. The following is a list of accessories incorporated into an advanced CNC system:

1. Central Processing Unit (CPU)
2. Servo Control Unit
3. Motor Driver Unit
4. Operator Panel
5. Machine Control Panel
6. Programmable Logic Controller (PLC)

1. Central Processing Unit (CPU)

The central processing unit (CPU) is considered the heart and brain of a controller as it controls and supervises a complete mechatronics system. It encodes explicit program information stored in the controller memory and decodes it to obtain signals for specific position and velocity movements of the axes. Since it manages the position and velocity of the moving elements (such as axis movements of a machine), it maintains complete control. If it does not match the programmed values, the CPU immediately takes corrective measures. It also checks basic security features of the CNC system, taking remedial action as needed. When the situation exceeds the CPU's limitations, it decides to shut down the machine or system.

2. Servo Control Unit

The input command signals for position and velocity control of movements are generated by the CPU and considered as signals for the servo control unit. The servo control unit generates suitable signals based on each movement command and sends them directly to the servo drive or amplifier unit. The servo drive or amplifier then generates the voltage necessary to rotate the servo motors. The servo control unit also receives the actual position signal from position feedback devices like encoders or linear scales that are integrated with the servo motors. Finally, the feedback signal is sent to the CPU unit for further processing. In summary, the servo control unit facilitates dual communication between the moving elements and the CPU through a command and feedback system. A separate motor driver unit always follows the axes movements, and the displacement depends on the feedback system.

3. Motor Driver Unit 

A motor driver unit is incorporated into a complete CNC system to operate separately controlled mechanisms. Typically, stepper and servo motors are used for controlled movements in a CNC system. A stepper motor driver unit drives the stepper motor, while a servo drive or amplifier rotates the servo motor. In a stepper motor, the motor driver unit generates distinct voltage pulses that turn the motor shaft at specific angles, providing the required torque. A servo amplifier typically provides pulse-width-modulated (PWM) voltage to rotate the servo motor shaft. The working principles of a servo amplifier and stepper motor driver will be discussed later. The following picture shows a stepper motor driver unit and a servo amplifier.

4. Operator Panel

The operator panel serves as a two-way communication system between the operator, the controller, and the machine. Most operator panels consist of two main parts: a video display unit and a keyboard. The video display unit shows the present situation and status of the machine or system, while the keyboard is used for writing programs into the machine and issuing commands. Sometimes, an operator panel may not have a video display unit. The following are two operator panels frequently used with CNC machines in the machining industry, manufactured by SIEMENS and FANUC.

5. Machine Control Panel 

The machine tool and CNC controller are directly connected to the machine operator through a Machine Control Panel (MCP). During a machining operation, the MCP controls the cutting speed or axis feed as well as the spindle speed. It is also used to run the machine in different operational modes like Jog, Incremental, and Automatic modes. The MCP controls the execution of a running program, allowing it to stop or be executed step by step. The following picture shows MCP units manufactured by SIEMENS and FANUC, commonly found in multiple CNC machines.

6. Programmable Logic Controller (PLC)

PLCs are currently used in various advanced mechatronics systems, including the machine tool industry, elevators, process control, and traffic light control. PLCs are typically manufactured by specialized companies and can be customized according to specific requirements with standard hardware. They replace complex relay logic circuits and offer greater versatility and flexibility in circuit design for modern mechatronics systems. In an advanced CNC controller, the PLC is embedded and cannot be identified independently from the outside. However, PLCs can also function as standalone units, coordinating with the CNC controller as a separate device. The supervision and sequence of operation of a complex mechanism are performed by a PLC through programs written inside it. The following picture shows some standalone PLCs coordinating with the CNC controller.

 

What is Controller

A controller serves as the brain of a mechatronics system, connecting various electrical, electronic, and mechanical components to enable system functionality. Its primary function is to interpret external input instructions and provide the necessary outputs to activate actuators, thereby fulfilling the given instructions. The controller collaborates with different elements to successfully trigger the actuators and execute the required actions. Controllers can vary depending on the system and operation. Typically, a microcontroller unit (MCU) is used as a relatively simple controller, sometimes embedded as an 'Embedded Controller' within small mechatronics devices. In complex mechatronics systems where multiple machines coordinate harmoniously within a single structure, advanced controllers such as CNC controllers, computers, or programmable logic controllers (PLCs) are employed.

What is a Microcontroller Unit or MCU?

A microcontroller unit (MCU) is a single integrated circuit specifically designed for managing devices and automating certain applications. MCU finds application in various mechatronics systems, including automobile engine control, washing machines, toys, cameras, and security systems. Most MCUs are battery-operated and require minimal power to function. The MCU consists of a small central processing unit (CPU), random access memory (RAM), programmable read-only memory (ROM), and embedded input-output ports (parallel and serial). Due to its dedicated function within a discrete system, the MCU is compact in size, with all components integrated into a single chip. In some cases, an MCU may have additional components like a small LCD or a seven-segment display unit with a keypad for information retrieval and directions. The image below depicts a simple microcontroller and its fundamental structure.

Programming of a microcontroller is typically done using the "C-language," stored in the controller's flash memory, and is reprogrammable. The MCU has various ports to control output elements or actuators connected to it, enabling ON/OFF control through programming. It also receives signals from different sensors connected to programmable ports on the microcontroller. Actuators linked to the MCU's output ports are automatically controlled based on signals received from sensors and instructions addressed in the programming, functioning without human intervention.

Difference between microcontroller and microprocessor:

Microprocessors are generally used with general-purpose CPUs or computers, whereas microcontrollers function as mini-computers to control multiple devices. Unlike microprocessors, microcontrollers include memory devices, input/output ports, and timers. Microprocessors require additional digital components to operate, while microcontrollers act as standalone units. Microprocessor-based devices are typically more complex and expensive, whereas microcontroller-based devices are cost-effective and straightforward. Most pins of a microcontroller can be efficiently programmed, whereas only a limited number of microprocessor pins can be controlled through programming. Additionally, microprocessors typically have higher access times compared to microcontrollers. In summary, a microcontroller directly interacts with coupled sensors and attachments, while a microprocessor connects input/output devices indirectly through an internal bus, uniting multiple hardware components such as RAM, serial ports, and USB ports. For example, a desktop computer commonly utilizes a microprocessor, whereas a washing machine is controlled by a microcontroller.

Advantages of using a microcontroller:

• Functions as a standalone micro-computer without requiring external digital devices.
• Mechatronics systems integrated with MCUs are relatively manageable and easy to maintain.
• Versatile operation due to easily programmable MCU pins. 
• Low operating response time.
• Additional memory devices and input/output components can be easily integrated.
• Compact size and cost-effective compared to other options.

Disadvantages of a microcontroller:

• The structure of an MCU is more complex than a microprocessor.
• Limited to specific purposes only.
• Cannot directly connect to power devices.
• Suitable only for small-scale equipment.

What is a CNC Controller?

Advanced mechatronics controllers are utilized in managing various robotic systems, CNC machines, and complex material handling systems. These controllers can handle almost all tasks within a mechatronics system and possess the capability to store programs in their memory. The key advantage of using advanced mechatronics controllers over microcontrollers is their programmability to manage complex movements and the integration of additional devices or elements into the system. These controllers primarily operate using two types of instructions: programmed instructions stored in controller memory and instructions entered via a connected control panel. Advanced mechatronics controllers, such as CNC controllers, consist of two separate devices—an integrated programmable logic controller (PLC) and a servo amplifier. The PLC may be embedded within the controller or connected externally. The servo amplifier supplies significant voltage to a servo motor for precise control of movements, such as axis movements in CNC machines. The PLC and servo drive mechanism enable a wide range of motions and complex tasks within an advanced mechatronics system while working in coordination with the controller. In some mechatronics systems and CNC machines, stepper motors are used instead of servo motors. These systems rely on a stepper motor and a driver unit to control all movements. The image below illustrates a typical advanced mechatronics system architecture, including a controller, PLC, servo amplifier, and servo motor.

The voltage required to drive stepper or servo motors, provided by the stepper motor driver or servo amplifier, is commanded through a CNC controller, enabling controlled movements. The PLC plays a crucial role in the controller, providing the necessary voltage to different actuators for additional tasks such as activating solenoid valves and running induction motors. After receiving commands from the controller, these tasks are executed flawlessly and monitored by various sensors and feedback elements. Continuous feedback devices like linear scales, encoders, and resolvers serve as position and velocity feedback elements for servo motors, enabling precise position measurement. Proximity switches, limit switches, pressure switches, and float switches are among the sensors used to monitor events. For instance, sensor input can be used to detect whether the machine door is open or closed, if the workpiece is correctly positioned, if the cutting tool is clamped, and if the cooling system is operational.

How does a CNC machine work

A CNC machine utilizes a dedicated computer known as the Controller, which manages most of the functions and stores programs in its memory. Working in harmony with the Controller are two other components: the Programmable Logic Controller (PLC) and the Servo amplifier & motor. The PLC can be integrated into the CNC Controller or function as a separate unit, providing external support. The servo drive or amplifier supplies the necessary voltage to the servo motors, enabling the machine's axes to move as required. When a command is sent from the Controller, it goes directly to the Servo amplifier unit, which provides the required voltage for axis movement by rotating a servo mechanism linked to the machine axes. The PLC supplies the necessary voltage to energize output elements and actuators such as relays, solenoids, and contactors, enabling various operations like starting an induction motor, controlling coolant flow, automatic workpiece changing, and opening a door. These are miscellaneous functions typically controlled by a PLC.

To ensure the successful completion of the work, the CNC machine continuously monitors the process. Feedback mechanisms are employed, which involve the use of position and velocity feedback devices such as Linear Scales, Encoders, and Resolvers, along with the axis movement path or servo motor shaft. Additionally, sensors like proximity switches, limit switches, pressure switches, and float switches are utilized to monitor different conditions or states of the machine, such as checking if machine doors are closed or if coolant is active. Each operation performed by the CNC machine is continuously monitored, and the confirmed information is sent to the Controller through specific feedback devices. This is why the CNC system is referred to as a closed-loop system. The absence of feedback signals to the Controller generates various fault messages, depending on the type of missing feedback. The block diagram provided illustrates the structure of a CNC machining center.

Upon examining the block diagram, it becomes evident that the CNC Controller serves as the central control unit of the CNC system, working in conjunction with the PLC to carry out all operations. Miscellaneous command information is sent to the Controller through an Operator panel, Numeric keyboard, or Machine control panel. The Monitor displays real-time information about axis position, program details, and any fault messages. Commands for axis movement or spindle rotation are directly transmitted from the Controller to the Spindle & Axes Servo drives, and the servo drives generate the necessary voltages to rotate the Servo Motors. The axis servo motor rotates a Ball-screw, which is connected to the motor shaft via a Coupling, enabling the machine axis or bed to move to the desired position. Simultaneously, the servo motor relays the position and velocity information of the axis movement directly to the Controller and Servo amplifier. The spindle servo motor rotates the cutting tool at high speeds and removes material from the workpiece through a shearing process, achieved through relative movement of the axes. The PLC is responsible for handling input elements or sensors and output elements or actuators associated with auxiliary functions related to the machine. Input elements or sensors provide information about the physical state of a machine part, which is then transmitted as an electrical signal to the Controller through the PLC. Output elements or actuators are employed to modify the physical status of the machine or perform auxiliary functions under the control of the PLC.

Types of CNC Machines

CNC machines are classified according to the nature of the work they perform. Popular CNC machines include CNC Machining centers, CNC Turning Centers, CNC Grinding machines, CNC Laser cutting machines, CNC Plasma cutting machines, CNC Routers, and 3D Printers, all of which have various applications. However, the most commonly used metal cutting machines in different modern industries are the CNC machining center and CNC turning center. CNC machining centers are typically categorized as vertical or horizontal machining centers, depending on the direction of the spindle movement. In vertical machining centers, the spindle movement is perpendicular to the base, while in horizontal machining centers, it is parallel. Most CNC machining centers are equipped with automatic tool change and workpiece changing systems. Sometimes, a single CNC machine is capable of performing two different machining operations, such as milling and turning, and is referred to as a turn-mill center. CNC machines are also classified based on the number of controlled axes they have, such as two, three, four, and five-axis CNC machines. The selection of a CNC controller usually depends on the number of axes to be controlled. A basic CNC controller is suitable for managing two to three axes, while an advanced CNC controller is capable of handling simultaneous movements of five or more axes. The basic working principle of all types of CNC machines is roughly the same. The following pictures depict various types of CNC machines.

 

CNC Machining center 

A CNC machining center (also known as CNC milling center or CNC milling machine) is a computer-controlled machine tool used for machining various materials, primarily metal, but also plastics and wood. The term "CNC" stands for Computer Numerical Control, which means that the machine's movements and operations are controlled by a computer program and precise numerical commands. CNC machining centers are capable of performing a wide range of cutting operations, such as milling, drilling, tapping, reaming, and other precision machining processes. These machines are widely used in manufacturing industries for producing complex and precise parts with high accuracy and repeatability.

The CNC machining center is the most popular machine tool used for milling operations. In milling machines, the cutting tool is clamped with the machine spindle and rotates at high speed. It removes excess material from the workpiece, which is mounted on the machine bed and moves in different directions. Horizontal and vertical milling machines are two types of CNC machining centers widely used in the machining industry. The spindle movement is perpendicular to a vertical milling machine and horizontal to the other. Most CNC machining centers offer 3 to 5 axes and can have a single or multi-spindle for complex milling operations. Some CNC machining centers are equipped with automatic tool changing and automatic pallet changing facilities to improve efficiency.

CNC Turning center

Another popular machine used in the machining industry is the CNC turning center, where the workpiece is clamped with the machine spindle and rotates at high speed. With the controlled movement of a stationary cutting tool, the material is removed from the workpiece. Turning is a machining process used to manufacture cylindrical parts. A turret with different cutting tools is affixed to the machine and programmed to remove material from the workpiece to achieve the desired dimensions. Two types of CNC turning centers are commonly used in the machining industry: slant bed type and flatbed type. Among them, the slant bed type turning center is widely employed and may have additional facilities.

CNC turning centers are widely used in various industries, including automotive, aerospace, medical, and general manufacturing. They are capable of producing precise and intricate components with excellent surface finish and dimensional accuracy. CNC turning is particularly well-suited for high-volume production of cylindrical parts, making it an essential tool in modern manufacturing processes.

CNC Turn-mill center

A turn-mill center is capable of performing both turning and milling operations on the same machine. It is a turning machine where milling operations are also performed on a cylindrical workpiece. The turret of the machine contains multiple fixed cutting tools for turning processes, and live tools (which can rotate) are added for milling operations. The machine is programmed to remove material from the cylindrical workpiece. Sometimes, mill-turn machines are also found, where milling is the primary operation and turning is a supplementary machining process.

CNC turnmill centers typically have a main spindle that is used for turning operations, and a sub-spindle that is used for milling operations. The main spindle is usually located in the center of the machine, while the sub-spindle is located on the side of the machine. CNC turnmill centers can be configured with a variety of tools, including turning tools, milling tools, and drilling tools. This allows them to be used to manufacture a wide range of parts, from simple to complex. CNC turnmill centers are a valuable tool for manufacturers who need to produce high-quality parts with high accuracy and repeatability. They are also a good choice for manufacturers who need to produce complex parts that would be difficult or impossible to manufacture on traditional lathes or milling machines.

CNC Grinding Machine

Grinding is a machining process that uses a rotating abrasive wheel as a cutting tool. Each grain on the wheel's surface cuts or removes a tiny chip from the workpiece. Grinding machines are commonly used for hard and fine machining, removing a small amount of material. Sometimes, a center-less cylindrical grinder is used for grinding with rotated workpieces. A CNC grinding machine is a type of machine tool that uses a rotating grinding wheel to remove material from a workpiece. This allows the machine to perform complex grinding operations with high precision and repeatability.

 

CNC grinding machines are commonly used in various industries, including automotive, aerospace, tool and die making, medical, and precision engineering. They are employed for grinding tasks such as cylindrical grinding, surface grinding, centerless grinding, internal grinding, and form grinding. These machines are known for their ability to produce extremely accurate and high-quality finished parts with tight tolerances and excellent surface finishes.

CNC Laser cutting machine

Laser cutting is a thermal process where a focused laser beam is used to melt the material, forming the expected dimensions. In this process, a laser beam is applied to vaporize or melt and remove the material slowly from the workpiece. CNC laser cutting typically uses optics, supporting gas, and a control system to precisely direct and focus the laser beam into the workpiece. A continuous cut is generated by passing the laser beam or sometimes moving the workpiece under CNC control. This process is suitable for cutting a wide range of materials such as metal, plastic, wood, glass, and paper.

The process of laser cutting involves focusing a concentrated beam of light, typically from a CO2 or fiber laser, onto the surface of the workpiece. The intense heat of the laser beam melts, burns, or vaporizes the material, creating a narrow cut known as the kerf. The CNC laser cutting machine's computer controls the positioning and movement of the laser beam, allowing it to follow the desired cutting path precisely. CNC laser cutting machines are widely used in various industries, including manufacturing, aerospace, automotive, electronics, and signage. They offer several advantages, such as high cutting precision, fast cutting speeds, minimal material wastage, and the ability to cut intricate and complex shapes. Laser cutting is particularly suitable for cutting thin to medium-thickness materials, making it an essential tool in modern metal fabrication and sheet metal processing.

CNC Plasma cutting machine

Plasma cutting is a process where an accelerated jet of hot plasma is forced at high speed through a nozzle to cut a workpiece. In this process, an electric arc is injected into the gas to ionize and form a plasma, which is then used to machine the metal. An electrical current passing through the ionized air between an electrode and the workpiece generates tremendous heat, melting the metal and blowing it away. CNC plasma cutting refers to the cutting of metals using a plasma torch, precisely controlled by a CNC controller.

The process of plasma cutting involves creating an electrical circuit between the plasma cutting torch and the workpiece. When the torch comes into contact with the material, an electric arc is formed, ionizing the gas (typically air, nitrogen, or oxygen) and creating plasma. The plasma reaches extremely high temperatures, melting through the material, while the high-velocity gas blows away the molten metal, resulting in a clean cut. Plasma cutting is especially suitable for cutting thick metals and producing parts with smooth edges. It is a cost-effective method for high-speed cutting of metal sheets and plates, making it a popular choice for industrial cutting applications.

CNC Router

A manual router is a hand-held electric power tool commonly used to rout or cut different materials such as wood and plastic into different shapes. It has a high-speed rotating cutter and removes the wood or plastic in its path when an operator pushes it forward. A CNC router functions similarly to a hand-held router but is operated through a CNC milling operation, accurately controlled by a controller. CNC wood routers are widely employed to create complex wood crafts by precisely controlling the movement of axes.

CNC routers are designed to handle a wide range of materials and thicknesses, and they can produce intricate designs with excellent detail. They are often used for tasks such as 2D and 3D carving, contouring, pocketing, drilling, and engraving. CNC routers come in various sizes, from small desktop models suitable for hobbyists and small workshops to large industrial machines used for heavy-duty production. The choice of CNC router depends on the specific application, the size of the workpieces, and the level of precision and complexity required.

EDM wire-cutting machine

Electrical Discharge Machining (EDM) is a process of machining where a 'tool' discharges thousands of sparks onto a metal workpiece. With an EDM wire-cutting machine, electrical discharge between a 'wire' and the workpiece creates sparks that rapidly cut away material. Non-ferrous wires, such as steel, titanium, and brass, are commonly used in EDM machining. The material melts or evaporates instead of being cut, leaving behind minute debris and providing very accurate dimensions. As the charged wire never contacts the workpiece, there are no cutting forces involved, making it possible to manufacture tiny and precise parts with EDM wire-cutting machines.

CNC EDM wire cutting machines are widely used in various industries, such as aerospace, automotive, tool and die making, and precision engineering. The wire EDM process provides high precision, excellent surface finish, and the ability to work with hard materials or delicate components without causing mechanical stresses. CNC EDM wire cutting machines are essential tools in modern manufacturing for producing molds, dies, tooling, and various intricate parts that require extreme accuracy and intricate details.

3D Printing machine

3D printing, or additive manufacturing, is a process of creating three-dimensional solid objects by depositing materials layer by layer, following a 3D digital model or programming. A 3D-printed object is constructed using additive manufacturing, which involves laying down successive thin slices of material until the object is complete. It can be considered the opposite of subtractive manufacturing processes like milling and turning.

There are several types of 3D printing technologies, each with its own unique approach to creating three-dimensional objects. Some common types of 3D printings are :

• ·  Fused Deposition Modelling or FDM - Here the printers use a heated nozzle to extrude and deposit thermoplastic filament layer by layer to build the object.
• ·   Stereolithography or SLA – Here the printers use a liquid photopolymer resin that is cured layer by layer using an ultraviolet (UV) laser or a light source.
• ·  Selective Laser Sintering or SLS – Here the printers use a high-powered laser to selectively fuse powdered materials (typically plastic, metal, or ceramic) layer by layer, creating durable and functional objects.

 

The Basic Elements of CNC machine

The basic elements of a CNC machine can be classified into three principal sections: the machine tool, the machine control unit (MCU), and programming. In the machining industry, different types of machine tools include milling machines, lathes, grinders, laser cutters, and plasma cutters. Typically, a machine tool has linear axes (X, Y, Z) and rotary axes (A, B, C) that facilitate the movement of the workpiece or cutting tool to achieve the desired dimensions. In some cases, CNC machines may also feature a tilt or additional axis.

The machine control unit (MCU) is the heart of a CNC machine, comprising various interconnected components that work in harmony to achieve the desired output in terms of axis movement and auxiliary functions. CNC machine programming involves a detailed set of instructions that guide the machine tool. Each command in a program specifies the axis position within the coordinate system (X, Y, Z) and the corresponding movement or auxiliary functions (ON/OFF). The elements of a CNC machine can be further categorized into the following groups.

Apart from the machine tool, a CNC machine consists of a combination of electronics and electrical elements, with the CNC controller being one of them. The CNC controller is a specialized type of computer that serves as the brain of the CNC system. It receives input signals from an external computer or operator panel and translates them into mechanical motion through motor output. Different CNC controllers are utilized based on capacity and system requirements. Another controller operating with a separate program, known as a PLC or PMC, helps to control the machine sequentially. Servo amplifiers and motors are employed together to facilitate movement along different axes. CNC machines are also equipped with various actuators to perform auxiliary functions, while sensors ensure the precise completion of processes.

Mechanical elements of a CNC machine typically refer to the machine structure, guideways, bearings, mechanical power transmission systems, and spindle mechanisms. A hydraulic power pack unit, composed of various hydraulic components, generates hydraulic pressure in a CNC machine. A hydraulic pump is typically used to generate system pressure and distribute it to different work areas, such as automatic tool changers (ATC), automatic pallet changers (APC), and tool clamping/unclamping mechanisms. Solenoid valves and pressure regulators are also utilized to control the pressure lines. Additionally, some CNC machines may feature a pneumatic pressure system that employs pressurized air to actuate cylinder pistons or other mechanical elements. The pneumatic pressure is usually supplied from a separate compressor unit located outside the machine area.

Various additional accessories can be found with different CNC machines, including rotary axes/tables, automatic tool change units, automatic pallet changer units, lubrication systems, coolant systems, chip conveyor systems, FRL (Filter-Regulator-Lubricator) units, manual pulse generators, servo-controlled voltage stabilizers, data communication devices, and probing systems. These accessories enhance the operational efficiency and functionality of the machine in specific ways. Most CNC machines come with some added equipment as standard accessories or as optional features. For example, a CNC machining center typically includes a tool magazine and an automatic pallet-changing system, while a CNC turning center utilizes a tool turret for tool-changing operations.

The workpiece program or part program of a CNC machine is a detailed set of commands that are typically stored in the CNC controller's memory. This program guides the machine by specifying the coordinate values of the tool's movement path. It can be written manually or using computer software. G-code programming languages are commonly employed for workpiece programming in CNC machines.

Preface

Manufacturing an excellent workpiece requires maintaining precise dimensions and achieving a superior surface finish. It is challenging to achieve this level of quality using traditional machines. If a conventional machine is capable of performing the task, it would take a long time, with the operator continuously monitoring every step and measurement. Without such meticulous monitoring, satisfactory results cannot be obtained after machining. Therefore, automated motion control is necessary, replacing the various types of hand-wheel control used in conventional machines. NC or CNC machines provide the required automation for motion control. Consequently, workpieces produced using NC or CNC machines ensure precise and accurate dimensions, as well as a beautiful surface finish.

Initially, NC machines were used for basic machining operations such as milling and turning. However, there was a need for a multi-axis control system to perform different types of complex machining on the same machine. By connecting the NC machine to a computer, the CNC machine was developed, offering much more flexibility in machining operations. Initially, earlier CNC machines were limited to basic machining operations, but over time, additional operations such as drilling, boring, and tapping were incorporated. To increase efficiency and save time in machining operations, additional accessories like an automatic tool changing system (ATC) and automatic work-pallet changing system (APC) were gradually introduced with CNC machines. In addition to traditional machining operations, CNC machines are now involved in various processes such as laser cutting and 3D printing.

What is Numerical Control or an NC Machine?

A Numerical Control or NC machine is a machine that operates based on a specific machining program and receives movement instructions in the form of numbers, letters, and symbols. It can work automatically or semi-automatically according to the coded instructions it receives. Typically, these instructions are provided through a Punch Tape. In an NC machine, a program instruction is designed for a particular task or part of a task, and the machine operates continuously based on that program. If the task needs to be modified, the program instructions must be changed accordingly. However, the utilization of NC machines is currently limited in the machining industry.

What is Computer Numerical Control or a CNC Machine?

In simple terms, a Computer Numerical Control or CNC machine is a modern version of the former NC machine. It employs a Microcontroller-based CNC controller, servo motors and drives, and a programmable logic controller or PLC instead of a Punch Tape. The CNC controller, servo drive, and PLC work together to control the precise movements and speed of the machine's axes. Additionally, a CNC machine can perform auxiliary functions such as automatic tool change (ATC) and automatic palette change (APC). In a CNC machine, cutting tools and their operations are closely monitored. The controller stores programs for different cutting tools and their functions, allowing for easy program changes according to requirements. As a result, CNC machines offer more flexibility compared to NC machines. The image below shows a CNC Turning center and a Machining center.

Difference between CNC and NC machines

There are several differences between CNC and NC machines. NC machines typically operate using magnetic or punched tape with coded instructions, while CNC machines store the directions for operation in computer memory. NC machines are commonly used for repetitive tasks of the same type, whereas CNC machines can perform various tasks on the same machine. The dimensional accuracy and surface finish of products manufactured on CNC machines are generally superior to those produced on NC machines. Additionally, features like automatic tool change and automatic palette change are only available on CNC machines. Finally, complex machining operations, such as 5-axis machining, can only be performed using CNC machines.

Advantages of CNC machines

CNC machines offer numerous benefits, including:

• The ability to prepare different types of work on the same machine.
• The capability to perform multiple machining tasks on a single machine.
• The ability to complete tasks within specific cycle times.
• Independence from the operator's skill level.
• Precise dimensional accuracy of workpieces.
• Lower production waste generated during machining.
• Enhanced operator safety compared to other machines.
• Reduced production costs.

Disadvantages of CNC machines

Despite being widely used for various machining operations, CNC machines have some disadvantages, including:

• Higher prices compared to conventional machines.
• Potential unemployment due to the reduced need for laborers when operating CNC machines.
• Lower skill requirements, result in a shortage of skilled workers.