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.