FirstMold Half Logo

What is CNC Machining? The Most Comprehensive Basic & Advanced Guide

Share This Article:
Featured Image-What is CNC machining

This article is primarily aimed at those who are newcomers to the manufacturing industry, providing an enlightening introduction to ‘what’s CNC machining’. It also encompasses more advanced knowledge, which might only be partially clear even to those who have been in the field for many years.

The content is comprehensive, with a word count exceeding 4 thousand. FirstMold believes you might find yourself repeatedly reading this article, as each session will enhance your knowledge to a new level. If you are looking to manufacture your products or parts, please click on ‘CNC Machining Services‘. In the link page, you can find more information about the extensive manufacturing capabilities and case studies of FirstMold, a leading factory in the machining world.

Now, Let’s start with the basic understanding of “what’s CNC machining”.

A bird's nest-shaped workpiece is being machined. This picture shows you visually what is CNC machining.
A bird’s nest-shaped workpiece is being machined. This picture shows you visually what is CNC machining.

What’s CNC Machining?

Explanation of CNC Machining

In general, CNC (Computer Numerical Control) refers to computer-controlled machining tools that operate under the guidance of a programmed sequence. This control system is capable of logically processing programs specified by control codes or other symbolic instructions. It translates these instructions via a computer, enabling the machine to perform predetermined actions. By cutting the workpiece with various tools, CNC machines transform raw materials into semi-finished or finished parts.

Simply put, you can think of CNC machining as a process where “computers” control machines. It’s important to note: not everyone working in a CNC workshop is necessarily operating the so-called “computers”.

A brief history of CNC machining

CNC machining has a glorious history that dates back to the several years of the late 1940s and most of 1950. While the United States Air Force System was searching for the method to manufacture the perfect parts of that time repeatably, it happened. They invented the first CNC (Computer Numerical Control) machine that used punch cards to do the control function. The machine called Numerical Control (NC) was a major step for manufacturing, as it enabled mass production.

In the 1960s, the development of CNC machines controlled by a computer made more creative tasks possible. As computer technology was upgraded, the CNC machines went further, and the next versions were 3-axis and 5-axis machines that could generate extremely complicated geometries and parts.

An Early CNC machine
An Early CNC machine

The second significant turning point occurred between 1980 and the turn of the century when the application of industrial PCs facilitated the emergence of new product lines in the CNC machine tool field, such as CNC intelligent green machine tools, among others. This era marked the gradual maturation of the CNC machine tool product system. With the advent of the Industry 4.0 era, the incorporation of cutting-edge technologies such as “AI + NC,” “BD (Big Data) + NC,” “CPS (Cyber-Physical Systems) + NC,” and “Cloud + NC” has propelled the CNC machine tool field to new heights.

CNC Machining Basics

The Process of CNC Machining

The process of CNC machining typically follows these steps:

  1. Reading the drawings and program sheet.
  2. Transferring the corresponding program to the machine tool.
  3. Checking the program, cutting parameters, etc.
  4. Determining the dimensions and allowances of the workpiece in the previous process.
  5. Reasonable clamping of the workpiece.
  6. Accurate alignment of the workpiece.
  7. Precise establishment of the workpiece coordinates.
  8. Reasonable selection of tools and cutting parameters.
  9. Proper clamping of the tool.
  10. Safe trial cutting methods.
  11. Observation of the machining process.
  12. Adjustment of cutting parameters.
  13. Timely feedback of problems to the relevant personnel during the machining process.
  14. Inspection of the workpiece quality after machining is complete.

CNC Machining Processes


Turning uses a lathe that rotates the workpiece. At the same time, a cutting tool takes the shape of the workpiece and eliminates the surplus one that is needed. This process generates cylindrical forms, such as shaft-type or bolt-type parts, and enables the machining of symmetric objects, such as gears.

By clicking on “CNC Turning Service“, you may gain more knowledge about this process.


The mechanism in milling is feeding off a workpiece using a cutting tool; it shapes the workpiece by taking material off it. The cutter itself may operate from multiple directions because the table, which carries the material, moves along the three axes X, Y, and Z. Now, milling will be satisfied by the technique that allows complicated three-dimensional part shapes to be fabricated.

Clicking on “CNC Milling Service” might provide you with a more comprehensive understanding of this technique.

However, distinguishing between turning and milling through text alone is not very intuitive. We will be releasing a series of videos to explain their differences in detail.


CNC drilling refers to a machining process where holes are drilled into the surface of a product using a drill bit. Typically, when performing drilling operations on a drill press, the drill bit must complete two simultaneous movements:

  • The primary motion, which is the rotational movement of the drill bit around its axis (cutting motion).
  • The secondary motion, which is the linear movement of the drill bit along its axis towards the workpiece (feeding motion).

CNC drilling is a very common process in CNC activities, and we will dedicate a separate article to explain it in detail.


CNC grinding involves the use of grinding tools to process the surface of a workpiece through numerical control technology. Most grinding operations are performed with a high-speed rotating grinding wheel, while a minority use oilstones, sand belts, and other grinding tools and free abrasives for processing.

The frequency of grinding processes is slightly lower than drilling, and we will also publish a detailed article on grinding later.

Diagram of three types of machining: turning, milling, and grinding
Diagram of three types of machining: turning, milling, and grinding

Types of CNC machines

The four basic CNC machining processes mentioned require specific equipment to perform these operations, which are what we refer to as CNC machines. Indeed, the term “CNC machines” is quite broad since there are many types of CNC machines: there are approximately 20 major categories and over 40 subcategories of commonly used machine tools.

In this article, we will introduce some common CNC machines:

CNC MachineMain Function
CNC LathesRotational machining of workpieces, commonly for creating cylindrical parts.
Turning CentersAdvanced lathes featuring additional capabilities such as milling and drilling.
CNC Milling MachinesMachining of workpieces using rotary cutters to remove material.
CNC Profile Milling MachinesMilling complex profiles and contours in workpieces.
Machining CentersVersatile machines capable of a variety of machining operations including drilling and milling.
CNC Drilling MachinesCreating holes in workpieces with precision.
CNC Boring MachinesEnlarging holes or machining cavities of precise dimensions in workpieces.
CNC Grinding MachinesFinishing surfaces of workpieces through grinding.
Grinding CentersSpecialized for comprehensive grinding operations, combining multiple grinding processes.
CNC Broaching MachinesMachining grooves or slots in workpieces through linear tool motion.
CNC Laser Machining CentersCutting, engraving, or marking materials using laser technology.

3-Axis, 4-Axis, and 5-Axis CNC Machining

After gaining an understanding of the commonly used CNC machining processes and the typical CNC machines, it’s important to highlight several specialized machining methods. These methods originate from CNC milling operations and are classified based on the number of axes involved in their operation:

3-axis CNC machining

3-axis CNC machining involves operating along three different linear axes, typically moving up and down, front and back, and side to side.

This setup allows machining on a single surface at a time, making it suitable for processing disc-shaped parts. However, it poses limitations for parts that require holes or grooves to be machined on multiple surfaces.

a 3-axis CNC machine
a 3-axis CNC machine

4-axis CNC machining

4-axis CNC machining adds a rotary axis to the three linear axes, typically allowing for 360° rotation in the horizontal plane. This rotation is not high-speed but is suitable for machining box-shaped parts.

Most 4-axis CNC machines can rotate work pieces around the X-axis. This is called the B-axis and is used for milling and turning the workpiece. It significantly speeds up the machining process and achieves high precision.

GF+ 4-axis CNC machine
GF+ 4-axis CNC machine

5-axis CNC machining

5-axis CNC machining introduces an additional rotary axis to the 4-axis setup, typically allowing for 360° rotation in the vertical plane. With 5-axis machining, comprehensive processing is possible, enabling machining in a single setup. This reduces setup costs and minimizes the risk of scratching or damaging the product.

Due to its high versatility, 5-axis CNC machining is used to manufacture complex and precise parts. Examples include medical components such as artificial limbs or bones, aerospace components, titanium parts, oil and gas machinery parts, and military products.

Each type of CNC machining has its pros and cons and is better suited for specific applications. For instance, 3-axis machining is a cost-effective and user-friendly option, making it suitable for small-scale businesses or startups. However, if a higher precision level is required or the part is more intricate, then a 4 or 5-axis machining may be essential.

Overall, the choice of machine depends on the specific needs of the application and the complexity of the part being produced. CNC machining has revolutionized the manufacturing industry, allowing for greater precision, efficiency, and versatility in producing high-quality parts.

Don’t say a 5-axis CNC machining is better than a 3-axis one.

Applications of CNC Machining

Having gained an understanding of the basic processes and workflows of CNC machining, let’s explore the diverse applications of CNC machining to truly appreciate its utility:

Aerospace Components Machining

The aerospace industry demands the manufacturing of parts such as engine components, flight controllers, and wing structures, which require high levels of accuracy and complexity. CNC milling machines meet these needs by offering precision, speed, and reliability, significantly reducing the margin for human error.

Medical Devices Parts Machining

The production of medical devices involves the creation of highly precise components, including artificial joints, prosthetics, and surgical tools. CNC machines play a crucial role in achieving the exacting standards required for these components, ensuring unparalleled precision.

Automotive Parts Machining

CNC machinery is widely used in the automotive industry to mill parts such as engine components, brake systems, and steering units. This technology supports both mass production and the fabrication of specific parts for particular car models.

Electronic Equipment Machining

Electronic devices often require intricate parts that necessitate precision, such as heat sinks, PCB (Printed Circuit Board) mounts, and casings. CNC machines are capable of machining these components with exceptional accuracy.

Shipbuilding and Marine

In the shipbuilding and marine industry, CNC machines are instrumental in fabricating ship hull parts, marine engine components, and marine equipment, ensuring their quality and reliability.

Tools and Molds

Manufacturing tools and molds demand a high degree of precision. CNC machines, equipped with capabilities for processes such as stamping, injection molding, and die casting, are essential for producing these intricate molds.

Engraving and Artwork

CNC machines have a broad range of industrial applications, including the creation of engravings and artworks. Their high level of accuracy and precision makes them ideal for machining a variety of materials into detailed artistic works or complex decorative items.

The applications of CNC in modern life extend far beyond those listed above. To better understand the power of CNC machining, I can confidently tell you: all solid materials can be processed by CNC.

Of course, that’s more of a jest. In industrial production activities, we should explore what types of products are more suitable for CNC machining.

Scope of CNC Machining

To give a simple example: chassis panels (typically more than 5mm thick) are not processed using laser cutting for the following reason: When machining openings in workpieces of such thickness, a pronounced cross-section is left, which is difficult to polish internally. Therefore, such products are more suitably processed using CNC machining.

What Parts Are Suitable for CNC Machining?

Complex Shapes

These are parts with irregular shapes that usually have poor rigidity and require multi-position mixed processing of points, surfaces, and lines. It’s difficult to ensure the deformation and precision of complex shapes, making them challenging to process on conventional machine tools. CNC machining is needed for these parts.

Discs, Sleeves, and Plate Parts

These parts have surface hole systems, keyways, radial holes, and curved surfaces on shaft parts. Conventional machine tools generally cannot process these parts. Curved parts require a CNC vertical machining center, and parts with holes require a CNC horizontal machining center.

Box-type Parts

These parts generally have a series of holes, internal cavities, and specific length-width-height ratios. They are mostly used in automotive, medical equipment, and aircraft manufacturing fields. These parts have relatively high machining requirements and usually go through milling, drilling, reaming, boring, counterboring, and tapping processes, almost covering all machining operations. Conventional machine tools are time-consuming and cannot guarantee machining accuracy, so these parts are typically processed using CNC machining centers.

Advantages of CNC Machining

Reduces the Need for Multiple Jigs and Fixtures:

CNC machining significantly decreases the number of tools and fixtures required. For parts with complex shapes, there’s no need for complicated jigs or fixtures. If there’s a need to change the shape and size of a part, it only requires modifications to the machining program. This is particularly advantageous for the development and modification of new products, offering great flexibility in prototyping and production adjustments.

High Processing Quality and Precision:

CNC machining ensures stable quality, high machining precision, and high repeatability. This level of consistency meets the stringent requirements of aerospace components and other precision-critical industries. The ability to maintain uniform quality across high volumes of parts reduces the risk of defects and increases overall reliability in the manufacturing process.

A CNC machine can process high precision products
A CNC machine can process high-precision products

Efficient for Varied and Small-Batch Production:

In situations involving the production of multiple varieties and small batches, CNC machining stands out for its high efficiency. It reduces the time needed for production preparation, machine tool adjustments, and process inspections. Moreover, the use of optimal cutting parameters minimizes cutting time, enhancing the overall production efficiency without sacrificing quality.

Machining parts for the automotive and aerospace industries with CNC machining processes
Machining parts for the automotive and aerospace industries with CNC machining processes

Capability to Machine Complex Surfaces:

CNC machining can process complex surfaces that are difficult, if not impossible, to achieve with conventional methods. It even allows for the machining of parts that cannot be easily observed. This capability opens up possibilities for manufacturing intricate and sophisticated designs that require precise internal contours or detailed surface patterns.

CNC process can process complex shapes of parts
CNC process can process complex shapes of parts

CNC Machining Materials

In CNC machining, there has been a saying circulating: if the material is not right, everything is in vain!

To develop and produce satisfactory products, material selection is the most basic and critical step. CNC machining can be selected from a wide range of materials, including metallic, non-metallic, and composite materials.


Common metal materials include:

  • Aluminum
  • Brass
  • Copper
  • Stainless steel
  • Steel
  • Titanium
  • Zinc

The aforementioned metal materials can be further subdivided into many types, such as aluminum alloys like 6061 and 7075, as well as steels like 45# steel and 40Cr steel, etc. However, these will not be detailed here. Interested individuals can explore our “CNC machining materials” page for more information.


Some common types of plastic materials used in CNC machining include:

Plastic MaterialProperties
Acetal (Delrin)High strength, stiffness, and hardness; excellent dimensional stability; good wear resistance; easy to machine
AcrylicExcellent optical clarity and transparency; good impact resistance; easy to machine and polish; prone to cracking
NylonHigh strength and toughness; good wear resistance; excellent dimensional stability; absorbs moisture.
PolycarbonateGood impact resistance; excellent dimensional stability; high-temperature resistance; prone to scratching
PolyethyleneLow friction and good wear resistance; chemical resistance; excellent impact strength; low strength and stiffness
PolypropyleneGood chemical resistance; low density; excellent impact strength; low stiffness and temperature resistance
PTFE (Teflon)Very low friction; excellent chemical resistance; good electrical insulation; difficult to machine
PVCGood chemical resistance; low cost; good impact strength; prone to UV degradation
different kinds of plastic materials
different kinds of plastic materials


Composite materials are composed of two or more materials and exhibit excellent physical and mechanical properties. Common composite materials include glass fiber-reinforced plastics (GRP) and carbon fiber-reinforced plastics (CFRP). These materials are suitable for machining various high-performance components, such as aerospace parts and automotive components.

It’s worth mentioning that both product designers and CNC operators should consider the material selection based on the environmental requirements, technical specifications, physical performance criteria, appearance, and surface treatment requirements, as well as processing performance considerations of the product itself.

When you’ve reached this point, you already have a basic understanding of CNC machining. You know what CNC machining is, its process, its applications, the materials it can process, and so on. However, CNC machining is not just a simple process. Next, we will continue to explore the advanced knowledge of CNC machining.

CNC Machining Advanced

CNC programming

CNC programming is a vital component of computer numerical control (CNC) technology. It involves encoding the machine’s motion trajectories, processing methods, process parameters, and other information to achieve automated machining on CNC machines. CNC programming typically involves writing machining programs, setting machining parameters, selecting tools, configuring cutting speeds, and feed rates.

CNC programming software
CNC programming software

CNC programming languages refer to specific languages used to write CNC machining programs, with G-code and M-code being the most common ones. G-code defines machining paths, tool trajectories, work coordinate systems, and other machining-related information, while M-code controls auxiliary functions of the machine, such as starting, stopping, and tool changes. The use of CNC programming languages enables the implementation of complex motion functions such as linear interpolation, circular interpolation, and helical interpolation.

G code sample of CNC machining
G code sample of CNC machining

For newcomers who have never dealt with CNC programming before, these two paragraphs might seem intimidating. However, the reality is that CNC programming is relatively straightforward. Let’s take a look at a comment from a user on Quora: “CNC programming isn’t difficult, it depends on what level you want to learn. Generally, the operation is quite simple. With someone teaching you, you can learn it in 2 days. Programming mainly involves remembering those codes, and you’ll get familiar with them after some time.”

CNC Tools

CNC tools are cutting tools used in CNC machine tools for various metal cutting processes.

In CNC machining, tools are an essential skill that every CNC operator must master, playing a crucial role. However, CNC tools are relatively complex due to their variety. Common tools include End Mills, Drills, Taps, Reamers, etc., and we will write a dedicated article to explain them in the future.

We only need to understand the performance requirements of tools, including:

  1. Model, specifications, and precision level of CNC tools.
  2. Good cutting performance.
  3. High precision.
  4. High reliability.
  5. High durability.

When selecting tools, the following factors need to be considered:

  1. Select tools based on the cutting performance of the parts and materials.
  2. Choose tools according to the machining stages of the parts.
  3. Select tools and geometric parameters based on the characteristics of the machining area.

How to Choose Tool Paths?

Tool paths refer to the trajectory and direction of the tool relative to the workpiece during CNC machining. The rational selection of tool paths is crucial because it is closely related to the CNC machining precision and surface quality of the parts. When determining tool paths, the following points should be considered:

  1. Ensure the machining accuracy requirements of the parts.
  2. Facilitate numerical calculations and reduce programming workload.
  3. Seek the shortest CNC machining path to reduce air-cutting time and improve CNC machining efficiency.
  4. Minimize the number of program segments.
  5. Ensure the roughness requirements of the workpiece contour surface after CNC machining. The final contour should be machined continuously with the last tool path.
  6. Carefully consider the tool’s approach and retract paths to minimize stopping the tool at the contour (causing elastic deformation due to sudden changes in cutting force) and leaving tool marks. Also, avoid vertical tool entry on the contour surface to prevent scratching the workpiece.

Workflow of Precision CNC Machining

In the CNC machining basics above, we’ve mentioned the general process of CNC machining. However, in precision machining, we often further divide the machining process. Precision part machining targets precise components of precision equipment, requiring high precision. This necessitates understanding not only the specific material requirements for machining parts and common machining techniques but also the stages involved in the precision machining of precision components.

Here, FirstMold’s setup operator shares with you the five stages of machining precision mechanical parts.

1. Rough Machining:

The task here is to remove most of the excess metal from the raw material, shaping it into the final shape and size of the part. Therefore, the main objective is to improve productivity.

2. Semi-finishing:

The task is to achieve a certain level of accuracy on the main surfaces while leaving machining allowances, preparing for the precision machining of the main surfaces (such as precision turning and grinding). It can also complete some secondary surface machining, such as drilling, tapping, and milling keyways.

3. Finishing Stage:

The task here is to ensure that all main surfaces meet the specified dimensional accuracy and surface roughness requirements. The primary goal is to ensure overall machining quality.

4. Super Finishing

For surfaces on parts with very high accuracy and surface roughness requirements (above IT6 level, with surface roughness below Ra0.2um), super finishing is required. The main purpose is to improve the accuracy of precision part machining and reduce surface roughness, without improving positional accuracy.

The 4 stages of precision part machining progress from coarse to fine, gradually refining the precision of mechanical parts. Through these 4 stages of machining, the accuracy of mechanical parts can meet the requirements of customers.

CNC Machining Trend, Challenge & Opportunities

With the continuous development of technology, the CNC machining industry is undergoing constant transformation and innovation. From smart manufacturing to Industry 4.0, from green manufacturing to sustainable development, the CNC machining industry is facing numerous challenges and opportunities. Next, FirstMold will explore the industry trends, challenges, and opportunities for the next 5-10 years.

Current Status of CNC Machining Industry

First, we need to understand the current status of the CNC machining industry. Currently, the CNC machining industry remains an indispensable part of the global manufacturing industry. Whether in fields such as automotive, aerospace, medical, marine, electronics, etc., high-quality components or finished products provided by the CNC machining industry are required. In the current economic situation, the market demand for the CNC machining industry remains extensive.

Although in the past few decades, the CNC machining industry has faced competition from low-wage countries, now more and more companies are realizing the importance of CNC machining and choosing to internalize their production processes. This trend has led to sustained growth in market demand for the CNC machining industry.

Market Size

The market size of the machining industry is expanding continuously, closely related to the development of the manufacturing industry. According to statistics, the global machining market size reached $13 trillion in 2019. In the coming years, the market size of the machining industry will continue to expand, with the global machining market size expected to reach $15 trillion by 2025.

Grand View Research’s report indicates that the global AI in the manufacturing market was valued at $513.6 million in 2020 and is forecast to grow at a CAGR of 41.2% from 2021 to 2028. AI technology integration has contributed to the significant growth of CNC machines, enhancing their capabilities.

Predicting CNC machine spindle problems using artificial intelligence
Predicting CNC machine spindle problems using artificial intelligence

Smart Manufacturing

Smart manufacturing is one of the important trends in the machining industry. By integrating technologies such as artificial intelligence, the Internet of Things, and big data with production lines, automation, intelligence, and flexibility in the production process can be achieved. This will greatly improve production efficiency, reduce machining costs, and enhance product quality.

Industry 4.0

Industry 4.0 refers to the use of technologies such as the Internet of Things, big data, and cloud computing to realize data collection, analysis, and control in the production process. This achieves intelligence and automation in the production process. Industry 4.0 will bring higher production efficiency, lower production costs, and better product quality to the machining industry.

Green Manufacturing

With the increasing environmental awareness, green manufacturing has become an important trend in the machining industry. Green manufacturing requires reducing energy consumption, lowering waste emissions, and improving resource utilization in the production process, achieving sustainable development in the production process.

Modularization and Standardization

Modularization and standardization are important means for the machining industry to achieve efficient production. By decomposing products into multiple modules, modularization of the production process can be achieved; by establishing standardized production processes, production efficiency can be improved, and production costs can be reduced.

Challenges In CNC Industry

Technological Innovation

Facing increasingly fierce market competition, machining enterprises need to constantly innovate technologically to adapt to market changes. However, technological innovation requires a large amount of capital investment, and many enterprises may face the dilemma of insufficient funds.

Talent Shortage

With the development of technology, the machining industry has an increasing demand for talents. However, talent shortage has become a bottleneck for the development of many enterprises. Enterprises need to increase the training and introduction of talents to meet the needs of development.

Market Competition

With the advancement of globalization, market competition is becoming increasingly fierce. Enterprises need to enhance the competitiveness of their products to adapt to market changes. However, market competition requires enterprises to constantly innovate, improve production efficiency, reduce production costs, and improve the cost-effectiveness of products.

Environmental Requirements

Environmental protection has become a hot topic of global concern, and the machining industry is no exception. With the continuous increase in environmental requirements, the machining industry is also continuously optimizing production processes, reducing environmental pollution. For example, using new materials, new processes, reducing emissions of exhaust gas, wastewater, and waste slag, achieving green production. In the future, as environmental requirements continue to increase, the machining industry will continue to introduce more environmentally friendly production methods and products to meet market demand.

Future Opportunities

We need to recognize that the machining industry still needs talents. Although digital technology and automation equipment can greatly improve production efficiency and quality levels, these equipment still require human operation and maintenance.

Moreover, the machining industry still needs professional technical personnel to research and develop more advanced technologies and equipment to meet the changing market demands. In addition, the machining industry still needs skilled craftsmen with high-level skills and experience to process complex components. All of these require talents with relevant skills and knowledge to accomplish.

Therefore, it can be concluded that the machining industry still has a future. Although digital technology and automation equipment have had a profound impact on the machining industry, these technologies and equipment cannot completely replace the role of humans. The machining industry requires talents with high-level skills and experience to process complex components.

So, how can the machining industry ensure sustainable development and adapt to future changes? First, the machining industry needs to strengthen its integration with digital technology and automation equipment, actively explore and adopt new technologies and equipment to improve production efficiency and quality levels. Second, the machining industry needs to strengthen the training and development of talents, attract more young people to join the industry, and improve the overall technical level and competitiveness of the


Above is FirstMold’s most comprehensive interpretation of “What is CNC Machining”, from basic knowledge to advanced discussions on the industry’s future. We believe you have gained valuable insights from it.

That’s pretty much the end of the introduction to CNC machining. My name is Lee Young. I have been working at Firstmold for over 10 years and have decades of experience in the industry. I am always here to assist you with any questions you may have about the machining industry. Don’t hesitate to reach out to me, and I will do my best to provide you with the answers and guidance you need.

Table of Contents

One Response

Leave a Reply

Your email address will not be published. Required fields are marked *