What Is NC Machining?- Definition and Basic Guide

NC machining and CNC machining use similar concepts as they are both automatic machines utilized in cutting and shaping metals. NC gives you the option of storing data during the machining process, while CNC offers you more flexibility and capacity in handling logical operations.

In this article, we’ll define NC machining, its working principles, types, applications and explain the differences between NC and CNC machining.

What is NC Machining?

Numerical control (also computer numerical control, and commonly called CNC) is the automated control of machining tools (such as drills, lathes, mills, and 3D printers) by means of a computer.

A CNC machine processes a piece of material (metal, plastic, wood, ceramic, or composite) to meet specifications by following a coded programmed instruction and without a manual operator directly controlling the machining operation.

A CNC machine is a motorized maneuverable tool and often a motorized maneuverable platform, which are both controlled by a computer, according to specific input instructions.

Instructions are delivered to a CNC machine in the form of a sequential program of machine control instructions such as G-code and M-code, then executed.

The program can be written by a person or, far more often, generated by graphical computer-aided design (CAD) software and/or computer-aided manufacturing (CAM) software.

In the case of 3D printers, the part to be printed is “sliced”, before the instructions (or the program) are generated. 3D printers also use G-Code.

CNC is a vast improvement over non-computerized machining that must be manually controlled (e.g. using devices such as hand wheels or levers) or mechanically controlled by pre-fabricated pattern guides (cams).

In modern CNC systems, the design of a mechanical part and its manufacturing program is highly automated.

The part’s mechanical dimensions are defined using CAD software and then translated into manufacturing directives by computer-aided manufacturing (CAM) software.

The resulting directives are transformed (by “post processor” software) into the specific commands necessary for a particular machine to produce the component and then are loaded into the CNC machine.

Since any particular component might require the use of a number of different tools – drills, saws, etc. – modern machines often combine multiple tools into a single “cell”.

In other installations, a number of different machines are used with an external controller and human or robotic operators that move the component from machine to machine.

In either case, the series of steps needed to produce any part is highly automated and produces a part that closely matches the original CAD drawing.

Brief History of the NC

The invention of numerical control has been due to the pioneering works of John T. Parsons in the year 1940, when he tried to generate a curve automatically by milling cutters by providing coordinate motions.

In the late 1940s Parsons conceived the method of using punched cards containing coordinate position system to control a machine tool. The machine directed to move in small increments and generate the desired finish.

In the year, 1948, Parons demonstrated this concept to the US Air Force, who sponsored the series of project at laboratories of Massachusetts Institute of Technology (MIT).

After lots of research MIT was able to demonstrate first NC prototype in the year 1952 and in the next year they were able to prove the potential applications of the NC.

Soon the machine tool manufacturers began their own efforts to introduce commercial NC units in the market. Meanwhile, the research continued as MIT, who were able to discover Automatically Programmed Tools, known as APT language that could be used for programming the NC machines.

The main aim of APT language was to provide the means to the programmer by which they can communicate the machining instructions to the machine tools in easier manner using English like statements.

The APT language is still used in widely in the manufacturing industry and a number of modern programming languages are based on the concepts of APT.

What is a Numerical Control Machine?

Numerical control, popularly known as the NC is very commonly used in machine tools. Numerical control is defined as the form of programmable automation, in which the process is controlled by the number, letters, and symbols.

In case of the machine tools this programmable automation is used for the operation of the machines.

In other words, the numerical control machine is defined as a machine that is controlled by a set of instructions called as the program.

In the numerical control method, the numbers form the basic program instructions for different types of jobs; hence the name numerical control is given to this type of programming.

When the type of job changes, the program instructions of the job also change. It is easier to write the new instructions for each job, hence NC provides lots of flexibility in its use.

The NC technology can be applied to wide variety of operations like drafting, assembly, inspection, sheet metal working, etc.

But it is more prominently used for various metal machining processes like turning, drilling, milling, shaping etc. Due to NC all the machining operations can be performed at the fast rate resulting in bulk manufacturing becoming quite cheaper.

How Does NC Machining Work?

NC machining, or Numerical Control machining, operates through a series of precise steps, each controlled by pre-programmed instructions.

This process allows for the automated and accurate control of machine tools, resulting in consistent and high-quality production.

Let’s break down the main stages of the NC machining process to understand how it works:

• Programming the Machine: The first step in NC machining involves programming the machine with specific instructions. These instructions, often in the form of G codes and M codes, tell the machine how to perform the required operations. This programming can be done using computer-aided design (CAD) and computer-aided manufacturing (CAM) software, ensuring precision in the commands given to the machine.
• Setting Up the Machine Tool: Once the program is ready, the machine tool is set up. This involves installing the necessary cutting tools and securing the workpiece in place. The setup must be accurate to ensure that the machining process proceeds smoothly and the final product meets the desired specifications.
• Executing the Machining Operation: With the program loaded and the machine set up, the machining operation can begin. The NC machine follows the programmed instructions to perform tasks such as drilling, milling, or cutting. Each movement and operation is controlled by the pre-defined instructions, allowing for high precision and repeatability.
• Inspecting the Final Product: After the machining operation is complete, the final product is inspected to ensure it meets the required standards. This inspection can involve measuring the dimensions of the part, checking for any defects, and verifying that the part matches the specifications provided in the design.

Types of NC Systems

The two major types of NC systems are:

#1. Point-to-point (PTP) system.

PTP is an NC system, which controls only the position of the components. In this system, the path of the component motion relative to the workpiece is not controlled.

The traveling between different positions is performed at the traverse speed allowable for the machine tool and following the shortest way.

#2. Contouring system.

Contouring NC systems are capable of controlling not only the positions but also the component motion, i.e., the traveling velocity and the programmed path between the desired positions.

Difference Between NC and CNC Machine

CNC and NC are both automatic machines used for machining any metal with accurate dimensions. These machines work on the feeding mechanism in which we command the machine through the program to make it perform a certain operation.

To know more about these machines, read the difference between NC and CNC machines given below:

• NC stands for Numerical Control while CNC stands for Computer Numerical Control. NC machine is a machine that is controlled by a set of instructions in the form of numbers, letters, and symbols called a program. CNC machine is used to control motions of the workpiece and tool with a computer program written in alphanumeric data. The program consists of precise instructions about the manufacturing method as well as the movements.
• In the NC machine, programs are fed into the punch cards. In a CNC machine, the programs are fed directly into the computer using a small keyboard.
• It is very difficult to modify the program in the NC machine if some error occurs and debugging is needed. Modification of the program is very easy on a CNC machine. For NC machines, you will have to change the program in the tape and feed it to the machine again even for a tiny change. In a CNC machine, you just have to change a variable in the computer to modify the program. This machine has memory storage and programs can be stored in its control.
• To operate an NC machine, the high skilled operator is required. For a CNC machine, the less skilled operator will work.
• Maintenance cost is less for NC machines is less as compared CNC machines. You can purchase CNC auto parts in Mumbai for reasonable prices.
• In NC machines, the programs cannot be stored. Whereas in CNC machines, the programs can be stored in the computer and can be used again and again.
• NC machine has no memory storage and it runs off of the tape each time the machine cycles. NC machines have a controller known as Machine Control Unit or MCU that is capable of reading and interpreting a stored program and using the instructions in this to control a machine via actuation devices.
• NC machines offer less flexibility and computational capability. CNC machines offer additional flexibility and computational capability.
• The accuracy of the NC machine is less as compared to CNC.
• On NC machines, more time is consumed for the execution of the job while it takes less time on CNC machines for the execution of the job.
• It is not possible to run NC machine continuously but you can run CNC machine continuously for 24 hours a day. CNC auto parts in Mumbai are easily available.
• The cost of NC machines is less while the cost of CNC machines is very high.

Applications of numerical control technology

Numerical control technology has applications in a wide variety of production operations such as metal cutting, automatic drafting, spot welding, press working, assembly, inspection, etc.

However, NC finds its principal application in metal machining operations. It is built to do virtually the entire metal removal process. (Example for metalworking Turning, sawing, Grinding, Milling, Drilling, boring).

The production jobs where the numerical control machines are most appropriate are listed below.

• The NC technology is suitable to sequence/series of machining process.
• Job geometry is complex, expensive. Mistakes in the process lead to high loss.
• It is expected engineering design changes in future.
• High metal removal is required.
• The work part required 100% inspection.
• There must be close tolerance on work part.
• When many operations need to be done when processing. It is frequently processed in batches of small lot sizes.

Advantages of NC Machine

• Greater manufacturing flexibility. NC can easily adapt to engineering design changes and a shift in the production schedule.
• Reduced manufacturing lead time. The job can easily and quickly set up with NC.
• Reduced non-productive time. In case of complex machining NC seems helpful to reduce the non-productive time. Because of quick/ automatic tool changing, quick setting up, and reduced workpiece handling time.
• Reduced fixturing. The fixture required in NC operation are simpler and less costly because NC tape does position instead of jig and fixture.
• Reduced inventory. This is the result of fewer setup reduced lead time.
• Quality control improved. No risk of human mistakes. It produces the part with high accuracy. It also reduces the man-hour for inspection.
• Greater operator safety.
• Reduce the scrap. the high accuracy of NC machine helps to reduce scrap material.
• Reduced floor space requirement. since the one NC can do variety of operation it replaces several conventional machines.

Disadvantages of NC Machine

• High investment cost and Maintenance cost. Most complex and sophisticated technology cost more than the conventional machine.
• Require skilled operator. Finding and training of NC personnel should be considered.
• Tearing and wearing of punch tape and less reliable punch tape component.
• Part programming mistake in punched tape.
• No optimal feed and speed. Conventional NC machine do not provide an option to change the cutting speed and feed during the operation.

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