CNC programming uses G-code language to program a CNC machine. These codes consist of various types of codes such as N-codes, T-codes, S-codes, etc.
Each code plays a specific role in determining the functionality of the CNC machine. However, N-codes generally do not have any practical significance in operating the CNC machine.
Then what exactly are N-codes, and why are they used in G-code programming?
This article discusses the structure and purpose of using N-codes in CNC programming and helps you understand its application through a practical example.
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Structure of a CNC Program
What is a CNC Program?
A CNC program is a computer-aided code used in numerical control that helps create and modify the geometry of a part or design for machining on a computer numerically controlled (CNC) machine.
It specifies to the machine which operations are to be carried out on a workpiece in a language CNC controllers can understand.
Structure
Given below is a sample CNC program
N15 G10 G30
N20 M05 T4
N25 M06 S1350
N30 G02 X1 Y1
N35 Z0.1
N40 G01 Z-0.125 F5
N45 X3 Y2 F10
N50 G01 Z1
N55 X0 Y1
N60 M05
N65 M20This CNC program contains a set of instructions for the CNC machines. It tells the machine what type of operation to perform and how to perform it.
It is represented in an alphanumerical format, and sometimes can also consist of symbols. Following are some of the letters used in CNC programs.
A, B, C, F, G, I, J, K, N, M, R, S, X, Y, ZThere are many different types of letter codes used in CNC programming, but the most popular ones are G-codes (red), N-codes (green), M-codes (blue), and T-code (yellow).
N15 G10 G30
N20 M05 T4
N25 M06 S1350N-Code and its Purpose
N-codes are a type of letter code used in G-code programs for CNC machines. They typically start with the letter “N” and are followed by a number to uniquely identify a block of code. This number acts as line number and helps the programmer to keep track of his code.
N15 G10 G30
N20 M05 T4
N25 M06 S1350
N30 G02 X1 Y1
N35 Z0.1
N40 G01 Z-0.125 F5
N45 X3 Y2 F10
N50 G01 Z1
N55 X0 Y1
N60 M05
N65 M20On most CNC programs, you can see each line of code starting with an N-code, and many CNC machinists program the code with a uniform incremental value.
For example, in the above-given code, the N-codes are implemented with an incremental value of 5. That is, after N15 comes N20, and so on.
This leaves behind four spaces in between each row of code. It is a good practice in CNC programming to leave incremental spaces.
It gives you flexibility in programming and allows you to add additional lines of code in the future as per your need.
These spacings are not necessary, but they can help make your CNC program easier to follow and modify.
Application of N-code Explained with an Example
Following is an example of a CNC program used for drilling holes on a workpiece using a CNC mill having an automatic tool changer.
It uses N-codes, and I’ll explain how it comes in handy during specific situations.
%
N5 T1 M6
N10 S8000 M3
N15 M8
N20 G00 X-0.05 Y-0.05
N25 G43 Z-0.2 F18.
N30 G98 G81 Z-0.25 R0.1 F12
N35 G98 G81 Z-0.50 R0.1 F12
N35 G80
N40 Z1
N45 M5
N50 M9
N55 G91 G28 Z0
N60 G91 G28 X0 Y0
N65 M30
%From the above-given program, only two lines of code perform the actual drilling operation.
The rest are for selecting the tool, setting the spindle speed, setting the tool coordinates, etc.
N30 G98 G81 Z-0.25 R0.1 F12 – Drills the hole with a depth of 0.25″
N35 G98 G81 Z-0.35 R0.1 F12 – Second drilling cycle that drills the hole with a depth of 0.5″
Now, if you want to drill the second cycle with a different tool, you can do so by adding more codes to the four spacings left between each line of code.
N30 G98 G81 Z-0.25 R0.1 F12
N31 M5
N32 M9
N33 T2 M6
N34 S5000 M8
N35 G98 G81 Z-0.50 R0.1 F12So I was able to add four extra lines of code (highlighted in red) to the program and change the tool while setting a new RPM value fitting the tool diameter.
You can use these N-codes creatively on your CNC program to leave out empty spaces and later add different operations to your program code.
Frequently Asked Questions
What software do CNC programmers use?
CNC programmers use many software tools to design, program, and machine parts. For example, CAD (computer-aided design) software is used to make 2D and 3D designs of the parts they want to machine, and CAM (computer-aided manufacturing) software is used to generate toolpaths for each part that they want to machine. Finally, control software programs are used to control the CNC machine to perform the desired machining operation. In addition, many programmers use simulation software to preview how part programs act on a specific machine setup.
Which language is used in CNC programming?
The language used in CNC programming is G-code. It was originally developed to be used with CNC milling machines, but it was later adopted by various other machine tools and has seen widespread use in the manufacturing industry.
What are some of the best software for CNC programming?
Some of the best software for CNC programming are MeshCAM, CamBam, EstlCAM, and OpenBuilds CAM. These software programs can convert designs made using CAD software to code that you can send to the machine.
