What is CNC machining? A complete guide on processes, applications, pros, and cons

CNC machining is a subtractive manufacturing technology widely used for rapid prototyping and production across numerous industries. This versatile technology creates high-quality components from a wide range of materials. So, what exactly is CNC machining, how does it work, and is it the right solution for your specific manufacturing needs?

This guide thoroughly examines CNC machining, what is a CNC system, and the working principles of CNC machines. The guide also delves into different CNC machining operations, exploring their diverse applications, advantages, and limitations.

What is CNC machining?

How does CNC machining work? Types of CNC machining operations

How does CNC manufacturing work? The CNC machining manufacturing process

CNC design considerations

CNC software

CNC machining terminology and parameters

CNC machining material selection

CNC machining applications

Industries that use CNC Machining

What are the Advantages and Limitations of CNC machining?

Conclusion

What is CNC machining? A Complete Guide on Processes, Applications, Pros, and Cons

CNC machining is a subtractive manufacturing process that creates parts by selectively removing portions of a workpiece using cutting tools or media. To understand CNC machining, it's essential to first grasp what CNC (Computer Numerical Control) is.

CNC is the automated control of machine parts and tools by a computer programmed with machine-readable instructions known as G-code (Geometric code). Specialised CNC programming software generates the G-code from digital 3D models of the objects. In summary, CAM (Computer Aided Manufacturing) software converts a digit model into G-code, which programs the computer to control the speed, direction, movement, and other aspects of a machine's parts and tools. These movements constitute the various CNC machining techniques for manufacturing precise and complex parts.

Before the incorporation of CNC, machining was a semi-manual process, with an operator manually controlling the machine’s movements. Depending on the operation and the machine, the operator manually feeds a rotating cutting tool into a stationary workpiece or a stationary cutting tool into a rotating workpiece, relying on a drawing of the intended finished object. This process is slow, error-prone, has limited capabilities, and can only be accurately performed by highly skilled operators.

With the integration of CNC, a computer precisely controls the movement, speed, and direction of all aspects of the machine. CNC elevates machining to a fast, accurate, and precise process, expanding manufacturing possibilities.

CNC machining is a highly versatile manufacturing process capable of accurately producing an extensive range of complex geometries and shapes. This process is compatible with numerous materials, including metals, plastics, glass, ceramic, foam, paper, wood, etc. CNC machining has opened up a plethora of manufacturing possibilities, driving innovation and facilitating fast, cost-effective production.

Types of CNC Machining Operations

CNC machining comprises various operations and technologies. These operations vary by machine type, geometries and features they produce, material removal techniques, and cutting technology.

The major types of CNC machining operations.

• CNC milling
• CNC turning
• CNC drilling
• CNC routing
• CNC cutting
• Electronic Discharge Machining (EDM)

These operations are executed by dedicated machines and cutting tools or mediums. Together, they make CNC machining a highly capable and versatile manufacturing process. Manufacturing a part may involve one or more of these CNC machining operations.

CNC milling and CNC turning are the most popular forms of CNC machining and account for most CNC machining applications. Some of the other CNC machining operations are variations of these two.

CNC Milling 

CNC milling is the most popular CNC machining operation. It utilises a rotating cutting tool to selectively cut away pieces of a block of material, creating CNC-milled components. In this process, a motor-driven spindle drives the cutting tool into a workpiece mounted on a worktable beneath it. During milling, the cutting tool and workpiece move relative to each other in various axes to provide the cutting tool access to different areas of the workpiece. These movements are controlled by a microprocessor embedded in the machine and executed by mechanical feed mechanisms. The process is executed by CNC milling machines, also called CNC mills

CNC milling service can produce a variety of complex features and shapes, including cubic and parametric geometries. It can also create curves and contours. This CNC machining operation achieves this through a series of cutting techniques, known as milling operations, that include face milling, plane milling, angular milling, and form milling. These operations vary by the shape and orientation of the cutting tool and the type of cut it produces. Milling-cutting tools are typically cylindrical-like and feature teeth at their tip or entire circumferences.

CNC milling is also capable of drilling and routing. However, there are dedicated machines for these processes. The machines have some variations that make them better suited to specific applications.

In addition to different milling operations, different types of CNC milling machines differ by the number of axes in which the workpiece and cutting tool can move. According to this classification, the most popular CNC milling machines are 3-axis and 5-axis mills.

See our comprehensive CNC milling guide to learn more about the CNC milling process and its processes, types, applications, benefits, and limitations.

3-axis CNC Milling

In 3-axis CNC mills, the cutting tool or workpiece can move in three lateral directions: the X (sideways), Y (back and forth), and Z (up and down) axes. The image below shows a CNC machine with 3-axis milling.

5-axis CNC Milling

As in the image below, 5-axis CNC mills can move in two rotational axes in addition to three lateral axes. The rotational motions may be along the lateral, longitudinal, or vertical axes. Furthermore, the motions may be executed by the workpiece, the cutting tool, or a mix of both. 5-axis CNC machining is faster and more capable than its 3-axis counterpart and is mainly applied in industrial CNC machining applications.

CNC Turning

In CNC turning, the workpiece is mounted on a rotating spindle and a stationary workpiece is fed into it. This process begins with the workpiece, which is a block of material. The workpiece is securely held in place by a chuck on one end. Depending on its size, the workpiece may require additional holding on the other end by a tailstock.

When the machine starts, the chuck rotates the workpiece at very high speeds, and a non-rotating cutting tool moves into it by predetermined depths, effectively carving out the desired shape. Turning cutting tools are usually flat and cubic-like with a sharp tip.

CNC turning primarily produces cylindrical, conical, and hexical shapes and features. This CNC machining operation achieves this through cutting techniques that vary by tool shape and orientation. The most common CNC turning operations include straight cutting, taper cutting, facing, and grooving. While turning is a faster, less complex process than milling, it is limited in the geometries it can produce.

The machines that carry out CNC turning are known as CNC lathe machines or CNC turning machines. There are also advanced turning centres that combine turning with milling capabilities.

CNC Drilling

CNC drilling is the process of creating a straight vertical hole in a workpiece using a rotating cutting tool or drill bit. The application of CNC ensures precision and accuracy in the drilling process. CNC controls the drill speed, depth, hole position, and various other factors.

While CNC milling and CNC turning machines can drill holes in a part, dedicated CNC drilling machines exist. These machines have slight variations that make them better suited for specific drilling applications. For example, CNC drilling machines typically have a large build platform and a gantry x-y motion system that allows these machines to accommodate relatively large, flat workpieces. In addition, the cutting tools are drill bits specifically designed for drilling. However, more advanced CNC drilling machines exist. These machines may have turret-type drill heads that can hold multiple drill bits and cutting tools, swapping between them mid-operation without stopping the machine.

Overall, drilling operations and CNC drilling machines are significantly less complex and less costly than their milling counterparts. Common drilling operations include drilling, tapping, threading, and boring.

CNC Routing 

CNC routing is a surface operation that involves removing portions of a workpiece's surface to trace out a pattern, geometry, or detail. In this CNC machining operation, a rotating cutting tool penetrates the surface of the workpiece by a shallow depth. Similar to drilling, CNC milling machines are also capable of routing operations. However, there are dedicated, less-complex CNC routers. Because routing is a surface operation, CNC routers prioritise speed and fluidity over torque. As a result, these machines, and CNC routing in general, are predominantly applied to softer materials such as wood and aluminium.

A common feature of CNC routers is a gantry x-y motion system that allows these machines to accommodate relatively large, flat workpieces. The cutting head features cutting tools that move in the Z axis by a shallow depth, while the tool typically features teeth at only its tip. Advanced CNC routers are capable of an additional rotational axis of motion, enabling them to perform operations on cylindrical surfaces. Popular CNC routing operations include routing, engraving, and shaping.

CNC Cutting

CNC cutting is the process of cutting through a workpiece. This CNC machining operation uses a cutting tool or medium to slice through the workpiece. In most applications, the workpiece is flat and thin. While CNC cutting is predominantly a step in sheet metal fabrication, the operation is applied in other applications involving other shapes and materials other than sheet metal. Technically speaking, CNC mills and lathes can cut through workpieces. However, “CNC cutting” predominantly refers to slicing operations on sheets and other relatively thin materials. CNC cutters can also carry out surface operations.

There are different types of CNC cutting technologies, with the critical differentiating factor between them being the means of cutting. The subject of the cutting medium gives rise to a broad aspect of engineering and manufacturing. Basic CNC cutters typically utilise a sharp metal blade capable of slicing through relatively thin, soft materials. Advanced CNC cutters take this further by using energy, liquids, and other forms of matter. The most common types of CNC cutting technologies are:

• Waterjet cutting
• Laser cutting
• Plasma cutting

While these cutting operations and their executing machines are not always referred to as CNC machining operations and machines, they technically are. The operations create parts via subtractive technique, removing portions of materials from a workpiece. In addition, CNC controls the cutting mechanisms, movements of the machine parts, and various other aspects of these operations.

Water Jet Cutting 

As the name implies, waterjet cutting utilises a water jet to cut through materials. In this process, a highly pressurised stream of water flows through a tiny nozzle at extreme speeds. At these speeds, the stream acts as a physical blade. The nozzle focuses the jet stream onto the workpiece, and the stream cuts through it on contact.

CNC controls the movement of the nozzle, the water pressure, and the flow activation. This process may utilise plain water or abrasive water containing abrasive particles. It can cut through various materials, such as metals, plastics, foam, etc., and geometries, including sheets and tubes. CNC waterjet cutting service can cut, engrave, and etch. See our water jet cutting overview to learn more about this process.

Laser Cutting

Laser cutting is similar to its waterjet counterpart. However, this process utilises a high-energy laser instead. Optics in the machine beam down the laser onto a workpiece below. The laser cuts the workpiece by melting, vaporising or burning through the material. CNC controls the laser's movements and intensity.

Laser cutting can cut through a workpiece or cut to a set depth, making this CNC machining process capable of cutting, engraving, and etching. This process is compatible with various materials, including metals, wood, and plastics. See our laser cutting overview to learn more about this process.

Plasma Cutting

Plasma obtained from highly energised gas serves as the cutting medium in plasma cutting. A distinguishing characteristic of plasma cutting is that it is an electrical one. When the cutter ejects the plasma through the nozzle onto the workpiece, the plasma creates an electric arc with the workpiece on contact, creating enough heat to melt through it. This characteristic means plasma cutting is only compatible with electrically conductive materials like metals. This CNC cutting process can cut thicker cross-sections than its waterjet and laser counterparts. CNC controls the activation, intensity, and movement of the plasma. See our plasma cutting overview to learn more about this process.

Electrical Discharge Machining

Electrical Discharge Machining (EDM) is a precise manufacturing process that removes material from a workpiece using thermal energy. Unlike other CNC machining methods that use mechanical force to cut materials, EDM employs electrical discharges (sparks) to erode material from the workpiece. This method is particularly effective for machining hard materials or creating complex shapes that are difficult to achieve with conventional machining techniques.

In the EDM process, a tool electrode and the workpiece are submerged in a dielectric fluid. The tool electrode, often made of graphite or copper, does not touch the workpiece. Instead, a series of rapid electrical discharges occur between the tool and the workpiece. These discharges generate intense heat, melting and vaporising the material at precise locations. The dielectric fluid cools the vaporised material, flushing away the debris and preventing arcing.

How to Select the Right CNC Machining Operation

Depending on the desired geometries and features, manufacturing an object may involve one or a combination of multiple CNC machining operations or machines. Note that certain operations aren't restricted to specific machines. For example, CNC mills can also drill and route. The following factors influence the selection of a CNC machining operation and, by extension, a CNC machine.

• Shape and geometry: Part geometry is the primary consideration when selecting a CNC machining operation. Milling mainly produces cubic and parametric shapes along with circular features, while turning produces cylindrical and circular shapes.
• Features: In addition to the overall workpiece and finished product geometry, individual features are also vital. For example, holes require drilling, while surface patterns require routing. Similarly, through cuts require cutting.
• Specific application: Different machines can perform some CNC machining operations. For example, CNC drills, mills, and lathes can drill holes. Similarly, both CNC routers and CNC milling machines can perform routing. However, the specific application determines the appropriate machine. For example, a CNC drill is more appropriate than a mill for drilling multiple holes in sheet metal. Likewise, routing a relatively soft material requires a CNC router.

Geomiq saves you the hassle of analysing options. Simply upload a CAD model of your part and select your preferred material, and our manufacturing experts will decide the best operation(s) to create the exact geometries you require.

How does CNC manufacturing work? The CNC machining manufacturing process 

Manufacturing a part via CNC involves one or more CNC machining operations. However, regardless of the process or CNC machine, the CNC manufacturing process, from conceptualisation to finished product, typically consists of five steps:

• Designing a digital 3D model
• Converting the model to G-code
• Preparing the CNC machine and the workpiece
• Executing the process
• Post-processing

3D Model Design

The first step in the CNC machining process is creating a 3D digital replica of the part to be manufactured. In the CNC design step, a designer creates a model of the part using Computer-Aided Design (CAD) software. The 3D CAD model contains all the necessary information about the part, including dimensions, machining tolerances, and material. During the CNC design stage, designers and engineers carry out a process known as Design For Manufacturing (DFM), ensuring that the design is optimised for seamless and cost-effective manufacturing. DFM accounts for size, tolerance, and geometry limitations. Upload your CAD design on our instant quoting platform to receive complimentary DFM service.

Other digital model creation methods include 3D scanning and digital photography, followed by 3D geometry extraction in photo-telemetric software. However, these methods are error-prone and require the product to exist. After creating the CAD model, the designer exports it in a suitable file format. See our CNC basics design guide to learn more about creating optimised designs for CNC machining.

Converting The Model to CAD

CNC machines do not read CAD or digital models directly in their native formats. Models must first be converted to machine-readable language known as G-code that the machines’ computers can read and interpret. CNC machining experts use specialised Computer-Aided Manufacturing (CAM) software programs to carry out this conversion.

The designer imports the model into CAM software, which analyses it and generates a corresponding set of commands in G-code. Designers may also use Computer-Aided Engineering (CAE) software to perform advanced real-life analysis on a part. The image below is an excerpt of G-code for CNC machining a part.

Sample G-code for a CNC milling operation

G-code contains instructions that dictate several parameters of the CNC process. Depending on the CNC machine and operation, these parameters include tool speed, cutting depth, feed, rotating speed, and temperature. CAM software also generates additional instructions, such as M-code (Miscellaneous code), that guide other aspects of the machining process.

Preparing the Workpiece and The CNC Machine

In this stage, an operator imports the G-code file to the CNC machine. The operator prepares the workpiece, securing it to the machine's worktable or holding mechanism, and then proceeds to set up the machine. The setup process varies slightly between CNC operations. It may involve determining the cutting orientation, setting the cutting tool’s starting point, preparing cutting fluid, and various other processes.

Executing the Machining Process

After setting up the machine and workpiece, the operator switches on the CNC machine, and the operation begins. Depending on the specific project, human intervention may be optional. In contrast, some projects may require an operator to reposition the workpiece or switch cutting tools. The machining process continues until the desired object, feature, or geometry forms.

Post-processing 

Post-processing refers to the operations and processes carried out on a finished part to give it specific properties or capabilities. Post-processing may be functional or aesthetic and is only sometimes critical, as CNC machines can produce parts that are usable as machined. This ability is one of the many advantages of CNC machining. The part in the image below has undergone bead blasting and red anodising post-processing.

Bead blasted, anodised CNC machined part

CNC milling post-processing options include:

• Surface finishing: Deburring, polishing, blasting, sanding, dyeing, powder coating, and painting.
• Coating: Galvanizing (zinc), electroplating (chrome, nickel), and anodising.
• Treatment: Annealing, quenching, hardening, tempering, and normalising.

Our CNC machining surface finish gallery comprehensively explores available CNC machining post-processing options.

CNC Design Considerations

The design phase is crucial for achieving high-quality results and optimising manufacturing. Understanding the key CNC design considerations can significantly impact your production's efficiency and accuracy. The following are some CNC design considerations to ensure seamless manufacturing and produce high-quality parts.

Tolerance

While CNC machining is a highly accurate manufacturing process, It is impossible to manufacture a part with 100% perfection. Tolerance is the permissible deviation of an object’s dimension from its intended value that will still allow the object to perform its intended function. Tolerances vary by project requirements and characteristics. However, the following industry-wide machining tolerances commonly apply to CNC machining operations.

• 3-axis milling: ± 0.13 mm (0.005″)
• 5-axis milling: ± 0.13 mm (0.005″)
• Lathe: ± 0.13 mm (0.005″)
• Router:  ± 0.13 mm (0.005″)
• Engraving: ± 0.13 mm (0.005″)
• Screw Machining: ± 0.13 mm (0.005″)
• Steel Rule Die Cutting: ± 0.381 mm (0.015″)
• Surface Finish: 125RA.

Geometries and Features

It is essential to account for the machines' limitations during CNC design. The following are some features and geometry considerations for CNC machining.

• Design internal edges with radii. Milling and routing cutting tools are typically cylindrical, making it difficult for them to produce 90-degree straight internal edges.
• Avoid too deep cavities. Cavities deeper than six times the diameter of the cutting tool are considered too deep and can damage the tool and make chip evacuation difficult. Furthermore, a cavity should be a maximum of four times its width.
• Avoid excessively thin walls. As walls get thinner, they are more susceptible to breaking under vibrations during the CNC machining process.
• Use standard hole sizes. While CNC machining can create holes of various sizes, we recommend designing holes with standard diameters. For depth, we recommend a maximum depth of four times the hole diameter.
• Limit the number of threads. The holding force of threads usually resides in the first few teeth at a depth of about 1.5 times the diameter of the hole. Threads longer than three times the nominal diameter are not necessary.

See our CNC design guide for a full breakdown of how to design for CNC machining.

CNC software

Because CNC machining is a largely computerised process, it requires applying specialised software to transform a part from an idea in the creator's mind to actionable CNC machine programming that CNC machines can interpret and execute. The three categories of software programs that enable CNC machining manufacturing are:

• CAD (Computer-Aided Design)
• CAM (Computer-Aided Manufacturing)
• CAE (Computer-Aided Engineering)

The incorporation of these software programs provides some of the critical advantages of CNC machining, including accuracy and speed. Each software category tackles a different aspect of the CNC machining manufacturing process and is used in the CNC design stage. Some software programs combine these capabilities into one package.

• CAD

CAD software provides a means to create a tangible version of an idea. These programs enable designers to create exact 3D digital replicas of products, incorporating size, dimensions, and tolerance. The programs typically feature drawing tools, geometries, shapes, and operations that designers use to build objects step-by-step from scratch.

Some CAD programs allow users to apply materials to a model and create photorealistic versions of the object. Users can create parts, assemblies, and 2D drawings. The design possibilities using CAD are endless. However, take note not to design non-machinable features. CAD programs store all the information in a CAD file, with the most popular file format being STEP (.STP).

• CAM

CAM software programs are responsible for converting the 3D CAD model from a digital model to machine language. When a CAM software program receives a CAD model, it analyses the model and generates the corresponding G-code, which contains instructions that the CNC machine needs to follow to create the object.

In addition to generating tool paths, CAM programs dictate optimal machining parameters such as speed, depth, feed, and temperature, thereby improving machining efficiency. These programs also allow users to simulate the machining process to verify tool paths and identify potential errors.

• CAE

CAE software programs don't directly influence the CNC machining process but ensure, from the CNC design stage, that the manufactured objects will be able to perform their expected functions seamlessly. These programs allow users to simulate real-life conditions and perform analyses, such as finite element analysis (FEA) and computational fluid dynamics (CFD), on 3D models to see how they perform. CAE also seeks to optimise designs for specific required properties such as strength, durability, and weight.

CNC Machining Terminology and Parameters

Certain terminologies describe various aspects of the CNC machining process. Some of these terminologies are parameters critical to a machining operation's success. These parameters, which describe various aspects of the CNC machining process, affect the efficiency and accuracy of the process, as well as the outcome of the finished product. Similarly, some terminologies describe other aspects of CNC machining, such as machine parts and tools. Understanding these parameters and technologies is vital to comprehensively answering the question, what is CNC machining?

Cutting Tool

CNC machining cutting tools are critical components that cut away portions of a workpiece. These tools come in various shapes and sizes, each designed for specific tasks such as drilling, milling, or turning. CNC cutting tools include end mills, face mills, drills, reamers, and taps. Each type serves a distinct function: end mills create complex contours and profiles, face mills for flat surfaces, drills for making holes, reamers for finishing holes to precise dimensions, and taps for threading holes.

The image below shows outlines for the following cutting tool types and applications: 

• 1-3 Flat, Bull, and Ball heads: Slots, grooves, cavities, and vertical walls. They are selected by the required form or bottom radii of a cavity.
• 4 Drills: Standard size holes.
• 5 slot cutters: Their head diameter is larger than the shaft, enabling them to create undercuts along vertical walls.
• 6 Taps are used for threaded holes
• 7 Face milling cutters remove material from large flat surfaces.

Cutting tools are typically made from materials like high-speed steel (HSS), carbide, and ceramics, each chosen for its durability and suitability for different materials and cutting conditions. Proper selection and maintenance of cutting tools are essential to optimising machining operations, improving surface finish, and extending the lifespan of both the tools and the CNC machine itself.

Tool Path

The programmed path that the tool follows to machine a part is generated by CAM software and contained in the G-code. This parameter is critical as deviations from the predetermined tool path can have grave implications, such as geometric inaccuracies, tool damage, and machining failure. CAM software enables users to generate the most efficient path for a CNC machining operation.

Cutting Speed

Also known as spindle speed or speed, this parameter is the rotational speed of the cutting tool or workpiece (as in turning). The spindle speed influences the cutting force, material removal rate, and heat generation. The correct speed is essential for optimal cutting, minimising tool wear, and achieving a good surface finish.

This parameter varies with the CNC machining operation and material. For example, CNC routing uses faster speeds than milling. Similarly, harder materials require slower speeds. Cutting speed is measured in Revolutions per minute (RPM). Recommended cutting speeds vary by material, geometry, and CNC machining operation and may vary by machine brand. It can also be calculated using formulas. In addition, advanced CAM software programs also provide optimal recommendations.

Feed Rate

The feed rate is the speed at which the cutting tools move into the workpiece. This crucial parameter directly impacts the quality of the cut, the surface finish, and the tool life. At optimal feed, the cutting tool has enough time to cut away pieces before moving further into the workpiece. Conversely, incorrect feeds can cause tool breakage, rough cuts, poor surface finish, and workpiece damage. Like speed, optimal feed rates can also be calculated using formulas and vary by material, geometry, and CNC machining operation. CNC machine manufacturers may also provide optimal recommendations.

Depth of Cut

Depth or cut depth is the thickness of material the cutting tool removes in a single pass. It is the distance from the top of the workpiece surface to the cut surface. Depth affects various aspects of CNC machining operations. Deep cuts reduce machining time and increase material removal rates. Conversely, they also generate more heat, put more load on the tool, increase the probability of tool deflection, and may increase vibration and surface roughness. Finding a balanced depth is critical to efficient machining.

Surface Finish

Surface finish is the level of the finished part's surface roughness after machining. A smooth finish can reduce friction, wear, and the risk of corrosion. It may also be for aesthetic and functional requirements. Note that certain applications may require relatively rough surfaces. CNC machining is capable of producing high-quality surface finishes. However, this parameter is influenced by material, speed, feed, and depth. The desired surface finish can also be achieved via post-processing operations.

Jigs and Fixtures

Jigs and fixtures are CNC machine add-ons that hold the workpiece and guide the cutting tool. These add-ons ensure the accuracy and repeatability of a CNC machining operation and are mainly used in batch productions. Jigs are tools that guide the direction of a work tool while holding the workpiece in place during machining, typically drilling operations. They work like stencils or templates for specific geometries. However, with the incorporation of highly accurate CNC, jigs are no longer commonplace in CNC machining operations, as these processes are highly accurate and rely only on precise G-code for guidance.

Fixtures, on the other hand, hold the workpiece in a specific position or orientation and vary by CNC machine type. They can be mechanical, hydraulic, or pneumatic and may be generic or custom-made. Custom fixtures are designed with the workpiece's final geometry in mind, enabling precise tool access to required areas.

CNC Machining Material Selection

One of the most beneficial advantages of CNC machining is its compatibility with an extensive variety of materials. This manufacturing process is compatible with metals, plastics, composites, wood, glass, stone, ceramics, foam, and paper.

Metals and thermoplastic are the most predominant CNC machining materials. Various industries use these engineering materials for numerous applications. Geomiq offers a broad selection of different metals and plastics. These materials have varying properties, making each best suited for different applications. The following are some factors to consider when selecting the best CNC machining material for an application.

• End use: The material must have the properties required for its end use. For example, aerospace applications require materials with high strength-to-weight ratios. Likewise, an application may require hardness, toughness, electrical conductivity or any other property. Conversely, properties may not be critical to the application. For example, proof-of-concept prototypes may not require critical selection.
• Work environment: Materials need to withstand the operating environment and conditions of the finished product. For example, products used in harsh chemical environments require chemical-resistant materials. The same goes for high-temperature and high-pressure conditions, among others. Finished products for such environments require materials with the corresponding resistances.
• Availability: Some materials are more readily available than others. Unless a specific scarce material is critical, consider more available options, especially in batch productions.
• Machinability: Similar to availability, machinability varies in different materials. This consideration is particularly imperative in batch productions as it increases machining time and cost and limits repeatability.
• Cost: Cost is a vital consideration for material selection. However, this consideration should come after other critical factors.

CNC Machining Metals

Metals are the most used engineering materials, so it is no surprise that they are the most machined. Various types of metals and metal alloys have different properties and applications. The table below details the most common CNC machining metals.

CNC machining metals: alloys, properties, and applications

CNC Machining Plastics

CNC machining can also manufacture products from various rigid plastics. However, it is important to take fume safety precautions when machining plastics, as certain plastics release toxic fumes at very high temperatures. The table below shows the properties and applications of some of the most common CNC machining plastics. See our CNC plastic machining article to learn more.

CNC machining plastics: properties and applications

CNC Machining Applications 

CNC machining is a highly versatile manufacturing process with numerous applications across various industries. CNC machining operations produce various sizes, shapes, and object geometries. These objects may be components of a larger assembly or end-use, standalone parts. The image below shows some parts manufactured via CNC machining.

There are three major categories of CNC machining applications:

• Rapid prototyping
• Custom one-off productions
• Batch production

Rapid Prototyping

As the name implies, Rapid prototyping is the process of quickly manufacturing a new part to test its feasibility or functionality. Due to its ability to produce custom parts fast, CNC machining is one of the go-to technologies of most manufacturers for rapid prototyping. An example of a rapid prototyping application is Geomiq's collaboration with Small Robot, an agrotech company in the UK. Geomiq facilitated their prototyping process for the creation of agro robots by providing them with engineering consulting and rapid custom parts.

Custom One-off Productions

Many CNC machining applications are custom productions. This application has many use cases, one of which is manufacturing spare parts. If a part in a piece of equipment breaks, engineers can quickly create a replacement part using CNC machining instead of waiting for a replacement from an OEM. Another use case is the manufacture of custom parts for specific purposes. For example, CNC machining can create a custom knee replacement for a specific patient.

Furthermore, creators and manufacturers can create non-existent custom parts from scratch using CNC machining operations, as well as replicas of existing parts.

Batch Production

Companies regularly use CNC machining to mass-produce objects, which may be end-use parts or components in an assembly.

Industries that Apply CNC Machining

CNC machining's versatility and numerous other capabilities make it widely applied in numerous industries. Some of these industries include:

• Automotive and Aerospace
• Medical and healthcare
• Machinery and equipment
• Consumer products
• Non-industrial applications

Automotive and Aerospace

CNC machining's precision and accuracy make this manufacturing technology indispensable in industries such as aerospace and automobile, where part accuracy is crucial. This manufacturing method produces engine parts, gears, bearings, ducts, and countless other critical parts from a wide range of products.

CNC-machined aerospace component

Medical and healthcare

Another industry where CNC machining's speed, accuracy, and ability to produce custom parts are indispensable is medicine and healthcare. Custom CNC machining creates precisely fitting custom prosthetics and medical implants, such as titanium bone and joint replacements, cobalt chrome teeth, and prosthetics. Other applications of medical CNC machining include batch production of medical paraphernalia, such as precise surgical instruments.

Artificial hip prosthetic with CNC machined components

Through our ISO 9001:2015 and ISO 13485:2016 certifications, Geomiq is officially certified as an exceptional medical equipment manufacturer. These prestigious international certifications officially underline not only our verified high-quality standards and rigorous adherence to international best practices but also our expertise in medical device development and manufacturing. Contact us or upload your designs to our platform to get started, and our team of experts will handle your project with unrivalled dedication and professionalism, whether for one-off custom implants or batch productions.

Machinery and Equipment

CNC machining processes are also widely employed in producing standalone objects, fixtures, and parts for industrial equipment and machinery in numerous industries, including manufacturing, production, construction, oil and gas, agricultural, electronics, defence, energy, and mining.

CNC machined gear

Consumer Products

CNC machining is responsible for a significant number of the products and technologies we use daily. From electronics gadgets and kitchen utensils to jewellery and house furnishings, countless consumer products are manufactured via CNC machining.

Non-industrial applications

CNC machining applications extend beyond industrial fields. Non-industrial fields such as woodworking, jewellery making, fashion, and even arts & crafts employ this manufacturing process to create intricate and functional parts. Examples are custom furniture, personalised gifts, tech accessories, house decor, and signage.

What are the Advantages and Limitations of CNC Machining?

CNC machining has revolutionised manufacturing through its various benefits and characteristics. However, this manufacturing process also has some limitations. On one hand, CNC machining offers unparalleled accuracy, repeatability, and the ability to produce complex parts with minimal human intervention. However, there are limitations, such as high initial setup costs and material wastage. The following are some key benefits and challenges of CNC machining.

Advantages of CNC Machining

• Capability: CNC machining can produce a wide range of parts, shapes, features, and highly complex geometries. This technology allows manufacturers to create both standalone end-use parts and fully functional assemblies, offering significant design freedom and flexibility. Furthermore, it can create both large and minute parts.
• Accuracy and Precision: Provided the CNC design is optimised, CNC machining replicates the design with very high accuracy. CNC machines are highly precise and can produce parts with very low tolerances. Most aspects of the CNC process are computer-controlled, minimising the margin for error and ensuring consistency.
• Speed: CNC machining delivers complex geometries rapidly. This ability is especially beneficial for prototyping applications. Compared to traditional manufacturing methods that involve numerous time-consuming processes, CNC machining offers a faster turnaround time from design to finished part.
• Versatility and Scalability: CNC machining is highly versatile and suitable for both one-off prototypes and medium-scale production batches. This technology can consistently produce multiple units with uniform quality. The range of processes and technologies within CNC machining means there is a suitable method for almost any application requirement.
• Material Compatibility: CNC machining is compatible with many materials, including metals, glass, plastic, stone, and wood. If a material can be procured in a block, it is likely suitable for CNC machining. This compatibility extends beyond standard engineering materials to include more specialised options, providing flexibility for various industrial applications.

Limitations of CNC Machining

• High Setup Cost: The initial setup costs for CNC machining can be substantial. CNC machines are relatively expensive, and the cost of advanced industrial models makes them only practical for large-scale industrial production.
• Speed in Large Batch Productions: CNC machining can produce a single part relatively fast. However, batch production can be time-consuming as most CNC machines typically create only one unit at a time.
• Cost of Complex Geometries: A part's complexity is directly proportional to its machining time, effort, and cost. Producing intricate designs can significantly raise production expenses due to extended operations and more advanced CNC machines.
• Material Wastage: CNC machining is a subtractive manufacturing process that generates a significant amount of waste. The process involves carving away material to create the finished part, resulting in a substantial amount of scrap compared to additive and formative technologies.

Design Limitations: As capable as CNC machining is, it has inherent design constraints. Certain features and geometries, such as curved holes, extremely thin walls, and straight internal edges, cannot be effectively machined. These limitations necessitate design adjustments and optimisations, which can sometimes compromise the original design intent.

Conclusion

Ready to get started on your CNC machining project? Geomiq is your ultimate partner for all your manufacturing needs. Simply head over to our instant quoting platform and upload your design to get started. With a few clicks, receive your finished part in as little as three days. Not sure where to begin? Our team of expert designers and engineers are available to guide you on design, material selection, and custom solutions that precisely match your needs.