CNC Vertical Machining Center

How To Program A CNC Machine

Oct 18, 2023

CNC machining has proved to be a major breakthrough in the machining and manufacturing of parts in different industries. Economical than robotics and more efficient than mechanical work, CNC machines offer a balanced solution for the manufacturing industries.

CNC (Computer Numerical Control) machines perform additive manufacturing processes with pre-programmed computer software. The CNC programs dictate the movement of factory tools and machinery in order to perform different manufacturing operations.

Therefore, programming is very important in the process of CNC machining. Therefore, the importance of CNC programmers can’t be undermined in the whole process of CNC machining. How does CNC programming work? How do you code CNC programs for your machining center?

In this article, we will talk about CNC programming. We will explore how to program a CNC machine and what popular software you can use to design programs for CNC machines. So, let’s get into the topic.


What Is A CNC Program?

As earlier mentioned, the CNC program allows the control of the CNC machine and performs different operations with the help of codes and instructions. Whether cutting, milling, grinding, or tapping, the CNC programming and programs are the crux of the operations performed in machining centers.

However, we can define a CNC program as the code or instructions developed and created by CNC programmers to be used to control the CNC machining centers. The CNC program works with different codes, and G-code is the most common one.

What Is CNC Programming?

 A CNC program is the set of instructions or codes needed to run the CNC machines for performing different operations and, CNC programming is creating the codes and instructions. The whole CNC manufacturing process depends on the CNC programming behind the operation. The precision, consistency, and accuracy of CNC machines in performing operations also depend on the CNC programming.

We can explain CNC programming as converting a CAD or CAM model into machine-readable instructions. It will dictate the description of the cutting tool to be used, feed rate, movement patterns for the tools, and the final design to be produced after cutting.

It will be more appropriate to explain CNC programming as a way to convert ideas into reality and code into carvings on the workpiece. The CNC programmers will work on the CAD or CAM software to create the tool paths and then convert it into a CNC program with the same software.


How Does It Work?

Before we talk about the types of CNC programs or CNC programming, let’s understand how the CNC programming process works for different CNC operations and machining centers.

A CNC programmer is the most important element in the equation of CNC programming. The programmer’s expertise will dictate how precise and accurate the CNC program is coded. What will a CNC programmer exactly do?

He will examine the paper or digital CNC model created using CAD software. The 3D CAD model of the workpiece allows the programmer to understand what series of instructions he will need to feed for creating parts.

Once he has examined the model, he will create codes using the CAM software. The codes entered into the CAM software are translated into machine-readable instructions.

Finally, the programmer will transmit the instructions to the CNC machines, like a mill, lathe, grinder, etc., to perform the machining process.

The CNC machining center will understand the instructions and perform tasks like cutting, grinding, etc., on a workpiece to develop intricate designs.


Types Of CNC Programming

Most CNC programmers use the CAM software for CNC programming. However, experts in different industries use three popular types of CNC programming techniques. We will briefly overview the types of CNC programming and when you can leverage one for performing CNC manufacturing processes in machining centers.

Manual CNC Programming

As the name suggests, the manual is the manual method and more fundamental technique of CNC machine programming. The commands are manually entered into the control console of a CNC machine, and it is a useful technique for simple parts and designs.

Manual CNC programming requires more expertise and laborious efforts for precise programming. There is also a higher chance of errors in manual programming due to a lack of warnings and notifications about program errors. These errors can also damage the machine or tool. Therefore, this type of programming is not popularly used due to the tendency for error.

Conversational Programming

The second type of programming is conversational programming, a built-in interface for programming to guide CNC machines.

G-code is not used in conversational programming, but plain English commands are entered, and the operator will answer a series of guided questions for full programming. Conversational programming, similar to manual programming, best fits simple designs rather than complicated and intricate designs.

CAM Programming

Finally, CAM(Computer-aided manufacturing) programming is used for fully automated machining processes. Software is used to develop codes and instructions for computer-controlled machines. CAM requires three components to function properly: software that will tell machines how to develop working parts, industrial automated machinery to turn raw materials into finished products, and post-processing to convert tool paths into machine-readable instructions or codes.

CAM programming is more popular due to its ability to handle intricate and complicated designs with great precision and accuracy. The prototype CNC machine heavily relies on CAM programming. The benefit of CAM programming also includes unmatched speed and accuracy as compared to manual machining and manual programming.


Coding For CNC Programming To Get Started

We will talk about the most important CNC codes you need to be familiar with to control your CNC machining centers and program the machine accurately. Here is the list of the CNC programming codes you will come across:


In alphabetical order, D comes first. Therefore, we will explain CNC programming code in this order, but it doesn’t imply the importance of one type of code over another.

D-codes are related to distance and the machine’s offset, which implies the distance between the cutting edge and center line of the cutting tool or how far the tool sticks out from the tool holder.  


F-codes, as the name suggests, are related to the feed rates of the CNC machine. The feed rates are coded using F-codes, defining the varying speeds at which the tool will be required to move during the cutting process.


Regardless of the operations, g-codes are the most commonly and frequently used codes during the CNC machining processes. The G-code refers to the geometry of the CNC processes to be performed on the workpiece. These codes will let the machine know where to start, move from, stop, and move between two points for precise cutting operations.


M stands for miscellaneous, and M-codes will instruct the CNC machine on miscellaneous functions like spindle control,  coolant, etc, and necessarily all non-geometric actions to be performed.


N-codes represent the identified lines or blocks of machine code. In essence, the N-codes help the CNC programmer organize and manually write the CNC code for the machines.


Then comes the S-code, representing the speed codes and dictating the machine’s tool spindle speeds at different times throughout the CNC machining process.


Finally, the T-codes of CNC programming help identify the cutting tool that will be required for a specific machining operation. You can’t just go with any random tool for any operation, but different operations require varying tools, and T-codes help the machine controllers pick the right tool for a specific operation.


Example Of A Program For CNC Machine

Let’s walk through the process of CNC coding and what a complete timeline of CNC coding will look like:

1. First things first, you must be familiar with CNC machining and using the CAD/CAM software to generate codes for running machining centers. You should have sufficient knowledge about which tool is used for what feature, how different materials behave during machining processes, and best practices for optimizing the feed rates, speeds, and tool paths for operations.

2. Then comes the CNC coding, which will begin with exporting the 3D CAD model into CAM software. You might be able to leverage the CAM capabilities in some CAD systems, eliminating the need to export the model to CAM software separately.

3. Once you have exported the model to CAM, you will need to convert the model into tool paths. You can do it manually or allow CAM software to do it, depending on the complexity of the design. However, an important thing to be mindful of is the tool selection, which must be according to the required part features and available tooling.

4. The next step is the verification of tool paths created by CAM software or manually. It implies ensuring that the tool paths are correct and poses no threats to the workpiece as well as the machine. Similar to the creation of CAM tool paths, verification can also be done automatically by a few prompts given to the CAM software.

5. Now, you will download the code to the CNC machine for final performance. It will include the G-code necessarily and any other code depending on what you’ve programmed. Once you have downloaded the code or transferred it to the machine via USB storage, you can run the program and get the desired workpiece.

Tips For CNC Programming For CNC Machine

What are tips for beginners who are just beginning to explore CNC programming for better control over their machining centers? Here are the practical tips you should leverage as a programming expert for CNC machines with different techniques.

Learn Basics And Keep Revisiting Them For Accuracy

You might feel overwhelmed by the programming basics, codes, machining processes, machine types, and a lot more. However, as a programmer, you’re the one having the driving seat and can’t compromise on the basics.

Therefore, you should learn the basics and keep revisiting them. It might sound absurd when using CAM programming, but when you have to do manual or conversational programming, the knowledge will help you ensure that you’re feeding the right specs into the CNC machines.

Customize Feed Rates Using F-codes

We have already talked about the feed rates, which define the speed of the tool and feed of the tool path. In most cases, operators dial in the program by taking a lot of time to ensure the program’s efficiency, consistency, and smoothness. When they are putting in this much time and effort, they usually don’t change it more often. However, customizing certain aspects of CNC programming can help optimize the manufacturing process.

Therefore, putting in extra effort for customized operations and desired results from products, adjusting and customizing spindle feed rates, and tool speed will help you.

Learn About CNC Machine Compensation  Types

CNC machine compensation refers to unpredictable variations that can occur during the machining process. The job of a CNC programmer is to ensure that the margin for such uncalled variations is minimal. It requires perfect coding and calculations for a perfect workpiece and final product. Therefore, a CNC programmer must be familiar with the common compensation types, factors that can influence, and how to program the CNC machines while accounting for these compensation types. For reference, the most common compensation types include cutter radius, tool wear, tool length, tool wear, etc.

Simplify The CNC Machine Programming

A good programmer will simplify the process of CNC programming for himself. It will be time-consuming if you’re programming operations and codes one by one. As a smart programmer, you should shorten the process of programming by using canned cycles. It implies that you will require one block per hole regardless of machining style. With canned cycles, machining additional holes is possible by merely re-programming the coordinates and not the whole program. In short, a programmer should capitalize on every opportunity to simplify the programming and speed up the process.



We have discussed how programming works for CNC machines, how you can program CNC machines, what codes are used for CNC programming, and tips the programmers and operators should leverage when dealing with CNC machining centers. This blog will guide you regardless of which machining operation you will program or what type of machining center you’re targeting. 


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