What is CNC Machining?

CNC machining is a manufacturing process known for its precision and versatility, where computer numerical control (CNC) technology is used to automate the control of machining tools such as drills, lathes, mills, and grinders. By interpreting computer-aided design (CAD) files, CNC machines can precisely cut and shape various materials, including metals, plastics, and composites, to produce intricate parts and components with high accuracy.

The process begins with the creation of a 3D design using CAD software. This design is then converted into a CNC program, which translates the digital model into a series of precise commands for the machine's movements and operations. CNC machining stands out for its ability to produce complex geometries with tight tolerances, repeatability, and a high-quality surface finish.

CNC machining is widely used across various industries, including aerospace, automotive, and medical device manufacturing, due to its efficiency in producing high-quality parts, whether in small custom batches or large-scale production runs. Its adaptability and precision make it a cornerstone in modern manufacturing techniques, enabling the creation of components that meet stringent specifications and tolerances.


CNC Machining Process

The CNC machining process is a highly precise and automated method used to manufacture parts with complex shapes and high tolerances. It involves several key steps from design to final product:

  1. Designing the Part: The process begins with creating a detailed 3D model of the part using CAD (Computer-Aided Design) software. This model includes all the geometrical and dimensional information necessary to manufacture the part.

  2. Converting the CAD Model: The CAD model is then converted into a CNC program using CAM (Computer-Aided Manufacturing) software. This step involves selecting the appropriate tools, cutting paths, and setting parameters like speed and feed rate to optimize the machining process.

  3. Setting Up the CNC Machine: Before machining starts, the CNC machine is set up, which includes loading the CNC program, setting up the tools in the tool changer, securing the workpiece onto the machine table, and setting the origin point of the workpiece, which serves as a reference for all machine movements.

  4. Machining the Part: The CNC machine executes the program, automatically controlling the movement of the tools to cut the workpiece according to the specified paths and parameters. Operations such as milling, turning, drilling, and more are performed to remove material and shape the part.

  5. Quality Control and Inspection: After machining, the part is inspected for accuracy and quality. This may involve measuring dimensions, checking surface finishes, and ensuring the part meets all specified tolerances and requirements.

  6. Post-Processing: Depending on the requirements, the part may undergo post-processing operations such as deburring (to remove any sharp edges), surface finishing (such as anodizing, painting, or plating), and heat treatment (to improve material properties).

  7. Final Inspection and Testing: The finished part is inspected and tested again to ensure it meets all final specifications and quality standards. This step confirms the part is ready for use or assembly into the final product.

CNC Machining Operations

CNC (Computer Numerical Control) machining operations encompass a wide range of processes designed to remove material from a workpiece, achieving the desired geometry, precision, and surface finish. These operations are executed by various CNC machines, including mills, lathes, grinders, and more, controlled by programmed instructions. Here's an overview of common CNC machining operations:


Milling is a versatile CNC machining process in which rotating cutting tools remove material from a workpiece to create a desired shape. It can perform a wide array of operations, from simple cuts to complex shapes and features like slots, threads, and gears. Milling machines operate on multiple axes (ranging from 3 to 5 or more), enhancing their capability to produce intricate and precise geometries. The flexibility of milling extends to various materials, including metals, plastics, and composites, making it indispensable in industries such as aerospace, automotive, and electronics. The precision and efficiency of CNC milling allow for high-quality production of components with complex designs and tight tolerances.

CNC Milling Machine


Turning is a CNC machining process where a cutting tool moves linearly while the workpiece rotates, primarily used to create cylindrical parts. This operation enables the production of features like holes, grooves, and threads on the external or internal surfaces of the material. Turning is celebrated for its ability to achieve high precision and smooth finishes, making it essential for manufacturing axles, shafts, and other rotational parts. Its efficiency and precision make turning a cornerstone process in industries requiring components with tight tolerances and smooth surfaces.

cnc turning center


Drilling is a fundamental CNC machining process designed to create round holes in a workpiece using a rotating drill bit. It's characterized by its precision and ability to produce holes of various diameters and depths across different materials. This operation is crucial in almost every manufacturing sector, facilitating the assembly of parts by enabling bolting and fastening, showcasing its versatility and indispensability in component fabrication.

CNC Drilling


Boring refines the diameter of an existing hole, enhancing its accuracy and surface finish. This CNC machining process uses a single-point cutting tool, making it ideal for achieving precise hole sizes and for creating tapered or contoured internal surfaces. Boring is crucial for applications requiring exceptionally tight tolerances and smooth internal surfaces, such as in the manufacturing of engine cylinders.

CNC Boring CNC Machining


Reaming is a finishing operation that slightly enlarges a pre-drilled hole to improve its diameter accuracy and surface smoothness. Utilizing a multi-edged tool called a reamer, this process ensures holes are of precise dimensions and ready for assembly. Reaming is essential in applications where tight tolerances and high-quality finishes are critical, such as in the aerospace and automotive industries.


Broaching is a unique machining process that removes material with a toothed tool, or broach, creating precise cuts in one pass. This method is highly efficient for producing unique shapes like keyways, splines, or complex profiles in both internal and external surfaces. Broaching stands out for its ability to achieve high precision and surface quality in parts that are difficult to machine by other methods.


Sawing in CNC machining involves the use of a saw blade to cut through material, typically to separate a piece from a larger stock or to cut the workpiece down to size. It's characterized by its straightforwardness and efficiency in cutting straight or curved lines. CNC sawing ensures precise cuts and is often used for preparing materials before other machining processes or for cutting structural shapes.


Grinding achieves high precision and surface finish by using a rotating abrasive wheel to remove material from the workpiece. This process can handle hard materials and is used for finishing operations, where it achieves dimensions and tolerances unattainable by other machining processes. Grinding is essential for applications requiring extreme accuracy and smooth finishes, such as tool and die making or finishing automotive parts.

CNC grinding stainless steel machining service


Tapping is the process of cutting internal threads in a pre-drilled hole using a tap tool. It is crucial for manufacturing components that require threaded holes for screws and bolts. Tapping ensures the threads are precise, uniform, and have a high-quality finish, making it indispensable in virtually every industry where assembly of parts is required.


Knurling involves forming a patterned surface on a workpiece to improve grip or aesthetic appeal. A knurling tool presses against a rotating workpiece to create a textured pattern. This operation does not remove material but deforms it to form the desired feature. Knurling is widely used on tool handles, knobs, and other components where a secure grip is necessary.


What are the Different Types of CNC Machines?

CNC (Computer Numerical Control) technology has revolutionized manufacturing processes, offering high precision and automation. There are several types of CNC machines, each designed for specific manufacturing tasks. Here's an overview of the most common types:

  1. CNC Mills: CNC milling machines are perhaps the most common and versatile type of CNC machine. They use computer controls to cut and shape material into different products with precision. Mills can operate on various axes (typically 3-axis to 5-axis) for complex geometries.

  2. CNC Lathes or Turning Machines: These machines rotate the workpiece on its axis to perform various operations like cutting, sanding, knurling, drilling, or deformation with tools that are applied to the workpiece to create an object with symmetry about an axis of rotation. CNC lathes are mainly used for machining cylindrical parts.

  3. CNC Routers: Similar to mills, CNC routers are generally used for cutting softer materials like wood, plastics, and foam. They are widely used in woodworking for furniture making, sign making, and producing detailed decorative pieces.

  4. CNC Plasma Cutters: Plasma cutters use a plasma torch to cut through metal materials by melting them away with a jet of hot plasma. These are used for cutting heavy material in the construction and demolition industries and for metal fabrication.

  5. CNC Laser Cutters: These machines use a laser to cut materials with high precision. CNC laser cutters are used for cutting metals, plastics, wood, and many other materials, offering clean cuts and the ability to handle complex geometries.

  6. CNC Grinders: CNC grinders use a rotating grinding wheel to remove material and achieve a fine finish on the workpiece. They are used for finishing surfaces to high precision and are commonly used in the metalworking industry.

  7. CNC Electrical Discharge Machines (EDM): EDM involves using electrical sparks to mold workpieces into specific shapes. There are two main types: wire EDM and sinker EDM. This process is used for hard metals or those that would be impossible to machine with traditional techniques.

  8. CNC Waterjet Cutters: Waterjet cutting uses a high-pressure stream of water, sometimes mixed with abrasive materials, to cut through materials. It's known for its ability to cut through almost any material without generating heat, making it ideal for materials that are sensitive to high temperatures.

  9. CNC Drilling Machines: These machines are designed specifically for drilling holes in workpieces. CNC drilling machines can perform precise holes in a variety of materials and thicknesses.

Each type of CNC machine offers distinct advantages and is chosen based on the material, complexity, and precision required for the project. Advances in CNC technology continue to expand the capabilities of these machines, making them integral to modern manufacturing processes.

Benefits of CNC Machining

CNC machining offers numerous benefits that make it a preferred choice in various industries for the production of precise and complex parts. Some of the key advantages include:

  1. High Precision and Accuracy: CNC machines are capable of producing parts with extremely tight tolerances, ensuring consistent quality even in complex geometries. This precision is crucial for industries where parts must fit together perfectly, such as aerospace and medical devices.

  2. Efficiency and Productivity: The automation of CNC machines allows for continuous operation without the need for frequent breaks or shifts changes, significantly increasing production speed. The ability to produce parts quickly and efficiently can lead to reduced lead times and increased throughput.

  3. Versatility: CNC machining can work with a wide range of materials, including metals, plastics, and composites, allowing for the production of parts for various applications. The flexibility to easily switch between materials and designs makes it ideal for custom or specialized projects.

  4. Reduced Labor Costs: Since CNC machines are automated and can operate with minimal supervision, the need for manual labor is significantly reduced. This can lead to cost savings in terms of wages and training for skilled operators.

  5. Improved Safety: Automation minimizes the need for direct interaction with the cutting tools, reducing the risk of accidents and improving safety in the manufacturing environment.

  6. Consistency and Reproducibility: CNC machining ensures that each part is produced exactly to specifications, making it easy to reproduce parts with the same high level of accuracy and quality, even over long production runs.

  7. Reduced Waste: The precision of CNC machining means that materials are used efficiently, with minimal waste produced. This not only reduces material costs but also supports more sustainable manufacturing practices.

  8. Enhanced Design Flexibility: The advanced capabilities of CNC machines allow for the creation of designs that would be difficult or impossible to achieve with manual machining processes, enabling more innovative and complex product designs.

These benefits make CNC machining a key component in the manufacturing processes of industries that demand precision, efficiency, and flexibility.

Hybrid Micro Machining

Applications of CNC Machining

CNC machining's versatility and precision enable its application across a wide range of industries and for various purposes. Here are some key applications:

  1. Aerospace: In an industry where precision and reliability are paramount, CNC machining is used to produce complex parts such as engine components, landing gear parts, and structural components. The ability to work with high-strength, lightweight materials like titanium and aluminum alloys is particularly valuable.

  2. Automotive: CNC machining aids in the manufacture of custom and high-performance parts, including engine components, suspension parts, and custom gears. It's also used for prototyping new designs and for the production of jigs and fixtures used in automotive assembly lines.

  3. Medical Devices: The medical industry relies on CNC machining for the production of precise and sterile components, including surgical instruments, implants, and orthotic devices. The capability to work with biocompatible materials and to achieve extremely tight tolerances is crucial.

  4. Electronics: CNC machining is used to create custom enclosures, heat sinks, and other components that require precise dimensions and thermal properties to protect sensitive electronic components.

  5. Energy: In the energy sector, including oil and gas, wind, and nuclear energy, CNC machining produces complex components such as valves, pistons, and turbine parts that can withstand extreme environments and pressures.

  6. Defense and Military: This sector utilizes CNC machining for the production of highly reliable and precise components for vehicles, weaponry, and electronic systems, where failure is not an option.

  7. Industrial Machinery and Equipment: CNC machining is essential for creating both the parts that go into complex machinery and the tools used to assemble and maintain them. This includes gears, fasteners, and structural components for manufacturing equipment.

  8. Consumer Products: From electronics to sporting goods, CNC machining is used to create durable and complex components that meet the aesthetic and functional requirements of consumer products.

  9. Prototyping: Beyond production, CNC machining is invaluable in the prototyping stage for almost any industry, allowing engineers to test and refine designs quickly and cost-effectively before mass production.

  10. Custom and Specialty Items: The flexibility of CNC machining supports the production of custom parts and one-offs, such as bespoke furniture components, custom motorcycle parts, and specialized tools.

These applications highlight CNC machining's role as a cornerstone in modern manufacturing, enabling innovation and efficiency across a broad spectrum of fields.

Plastic Injection Parts Medical Industry
Plastic Injection Parts Toy Products
Plastic Injection Parts Consumer Electronics Industry
Plastic Injection Parts Aerospace Industry

Metal Materials for CNC Machining

CNC machining is compatible with a wide variety of metal materials, each offering different properties that make them suitable for specific applications. Here's an overview of some common metals used in CNC machining:

  1. Aluminum: Known for its lightweight and corrosion resistance, aluminum is easy to machine and is commonly used in aerospace, automotive, and consumer electronics for parts like enclosures, gears, and structural components.

  2. Stainless Steel: Highly resistant to corrosion and oxidation, stainless steel is used in medical devices, food processing equipment, and marine applications. It's harder to machine than aluminum but provides excellent strength and durability.

  3. Carbon Steel: Offering a good balance of strength, ductility, and cost, carbon steel is used in the manufacturing of a wide range of parts, from machinery components to automotive parts. It's more challenging to machine than aluminum but less so than stainless steel.

  4. Titanium: With its exceptional strength-to-weight ratio and corrosion resistance, titanium is ideal for aerospace, medical implants, and high-performance automotive applications. However, it is more difficult and expensive to machine than many other metals.

  5. Brass: Known for its low friction and non-sparking properties, brass is easy to machine and is often used for gears, valves, and fittings in the electrical and plumbing industries.

  6. Copper: Excellent for electrical conductivity, copper is commonly used in electrical components, heat sinks, and radiators. It's malleable and softer than many other metals, making it relatively easy to machine.

  7. Bronze: This alloy of copper and tin, often with additional elements such as aluminum or nickel, is known for its wear resistance and strength. Bronze parts are used in bearings, bushings, and gears.

  8. Nickel Alloys: Including Inconel, these alloys are known for their extreme heat and corrosion resistance, making them suitable for aerospace, chemical processing, and power generation applications. They are, however, challenging to machine.

  9. Magnesium: Being the lightest structural metal, magnesium alloys are used in aerospace and automotive applications where weight reduction is critical. They are easier to machine than aluminum but require special handling due to flammability.

  10. Tool Steel: Known for its hardness and resistance to abrasion and deformation, tool steel is used to manufacture cutting tools, molds, dies, and other high-strength applications. It is generally more challenging to machine.

Each of these metals has its unique set of properties, including strength, ductility, corrosion resistance, and thermal conductivity, making them suitable for specific uses in CNC machining projects. The choice of material depends on the desired properties of the final part, including its strength, weight, and resistance to environmental conditions.

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Plastic Materials for CNC Machining

CNC machining can also be applied to a wide range of plastic materials, each offering unique properties that make them suitable for various applications. Here's an overview of some common plastics used in CNC machining:

  1. ABS (Acrylonitrile Butadiene Styrene): Known for its toughness and impact resistance, ABS is a popular choice for automotive components, consumer goods, and prototypes. It's relatively easy to machine and can be finished to a high standard.

  2. Polycarbonate (PC): Offering exceptional strength and transparency, polycarbonate is used for applications requiring high impact resistance and optical clarity, such as protective covers, lenses, and medical devices. It machines well but requires care to prevent cracking.

  3. Polypropylene (PP): This material is known for its excellent chemical resistance, elasticity, and fatigue resistance. It's commonly used in living hinges, containers, and automotive parts. Polypropylene can be challenging to machine due to its low stiffness.

  4. POM (Polyoxymethylene), also known as Acetal/Delrin: POM is renowned for its high precision, stiffness, low friction, and excellent dimensional stability, making it ideal for gears, bearings, and electrical insulators. It machines very well, producing a smooth surface finish.

  5. PTFE (Polytetrafluoroethylene), also known as Teflon: PTFE is known for its outstanding chemical resistance, high temperature tolerance, and low friction. It's used in applications such as seals, gaskets, and bushings. Machining PTFE requires specific considerations due to its softness.

  6. Nylon (Polyamide): Nylon is valued for its wear resistance, strength, and flexibility. It's used for mechanical parts like gears, bushings, and plastic fasteners. Nylon absorbs moisture, which can affect its dimensional stability during machining.

  7. PEEK (Polyether Ether Ketone): With its high temperature resistance, excellent mechanical properties, and chemical resistance, PEEK is used in demanding applications in the aerospace, medical, and automotive industries. It's expensive but machines well for high-performance parts.

  8. PVC (Polyvinyl Chloride): PVC has good mechanical properties, chemical resistance, and is easy to machine. It's used in pipe fittings, valves, and medical devices. Care must be taken when machining PVC due to the potential release of harmful chlorine gas.

  9. PET (Polyethylene Terephthalate): Known for its good mechanical properties and dimensional stability, PET is often used in mechanical parts, containers, and in applications requiring good wear resistance. It machines well and is also used in food contact and medical applications.

  10. PMMA (Polymethyl Methacrylate), also known as acrylic: Acrylic is known for its clarity, making it an ideal choice for optical applications, signs, and light fixtures. It machines well but is brittle and requires care to prevent cracking.

Choosing the right plastic material for CNC machining depends on the specific requirements of the application, including mechanical strength, thermal resistance, chemical compatibility, and aesthetic considerations. Each plastic material offers a unique set of properties that can be leveraged to achieve the desired outcome in the final machined part.

cnc plastic parts

Surface Finishes of Machining Parts

Surface finishes in CNC machining play a crucial role in determining the appearance, performance, and longevity of machined parts. The finish affects not just the cosmetic look but also the mechanical properties like friction, wear resistance, and corrosion resistance. Here’s an overview of common surface finishes for machined parts:

  1. As-Machined Finish: This is the basic finish straight from the machining process, with marks from the cutting tool visible. The degree of roughness can vary based on the tool used and the machining parameters. It's suitable for applications where the surface finish is not critical.

  2. Smoothed Finish: Parts are smoothed to reduce the roughness left by the machining process, often using fine machining or sanding. This finish improves the part's aesthetic and reduces friction in moving components.

  3. Bead Blasted Finish: Bead blasting involves blasting the part with small glass or ceramic beads to create a uniform matte or satin surface finish. It's often used to remove tool marks and improve the part's appearance without significantly affecting its dimensions.

  4. Anodized Finish: Anodizing adds a thin, hard, non-conductive ceramic coating on the surface of aluminum parts, enhancing their corrosion and wear resistance. It can also be used for coloration purposes.

  5. Powder Coated Finish: This finish involves applying a protective and decorative layer of powder to a part's surface, which is then cured under heat to form a skin. It offers excellent durability and corrosion resistance and is available in a wide range of colors.

  6. Electroplated Finish: Electroplating coats the part with a thin layer of metal, such as nickel, chrome, or gold, via an electrochemical process. This enhances the part's corrosion resistance, electrical conductivity, and aesthetic appeal.

  7. Brushed Finish: Achieved by polishing the metal with a fine abrasive, a brushed finish creates a unidirectional satin finish. It's often used for decorative purposes and can help hide fingerprints and minor imperfections.

  8. Polished Finish: Polishing results in a highly reflective, mirror-like surface. This finish is achieved through mechanical or chemical means and is used for parts that require a high aesthetic appeal.

  9. Chemical Film Coating (Chromate Conversion Coating): This coating is applied to aluminum parts to increase corrosion resistance and prepare the surface for painting or other coatings. It's commonly used in the aerospace and defense industries.

  10. Black Oxide: A black oxide finish is a conversion coating for ferrous materials and is used to improve corrosion resistance and minimize light reflection.

Each of these finishes can be applied based on the requirements of the application, balancing factors such as cost, durability, corrosion resistance, and aesthetic preferences. The choice of surface finish will depend on the material of the part, its intended use, and the environmental conditions it will be exposed to.

Metal Surface Finishing

Let the RALLY experts help you

Elevate the precision and aesthetics of your machined parts with the expertise of RALLY's team. Our specialized approach in applying surface finishes enhances the durability, performance, and visual appeal of your components. Whether you're seeking to improve wear resistance, corrosion protection, or simply achieve a sleek, professional look, RALLY has the solution. Our comprehensive range of finishes, including anodizing, powder coating, bead blasting, and more, ensures that every part meets the highest standards of quality and functionality.

Trust RALLY to provide the finishing touch that sets your project apart. Contact us today and let our experts guide you to the perfect surface finish solution tailored to your specific needs. Make the right call to action and see the difference RALLY can make.

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