Introduction
Selecting the right CNC machining type offers unmatched accuracy, high precision, and sharp tolerances. There are different types of CNC machining specifically for operations from cutting to surface finishing.
There are many ways to produce a part using CNC machining, but not all CNC operations will find an application for your part. Read this guide to understand the different CNC machining types and how to select the right one.
CNC Machining Definition
CNC machining is an automated subtractive machining process that removes material from a workpiece using CNC-controlled movement. This process uses different machining types each designed for a specific task to achieve final shape.
CNC milling can not only perform surface cuts but also drilling operations, reducing any separate drilling machines. Likewise, CNC turning specializes in cylindrical geometry while CNC grinding is for surface finish and precision.
Common CNC Machining Types
Whether you’re a designer, engineer, or machinist, these CNC machining operations are the most basic types and when used together can achieve any shape and surface finish.
CNC Milling
CNC milling uses a rotating cutting tool attached to a spindle rotating at high speeds to make contact with the workpiece and in turn remove material in small amounts. Only the tool moves and the workpiece remains stationary.
CNC milling can cut in three dimensions and is generally used for square or rectangular workpieces. CNC milling has many smaller operations like face milling, contour milling and profile milling.
Advantages
- CNC milling can produce tolerances of 0.0025mm
- It is possible to modify the milling process by editing the G-code
- CNC milling offers unmatched cutting speeds for round parts
Challenges With Milling
- It cannot produce undercut features in parts
- CNC milling is limited by the machine’s bed size. Large parts require larger beds which is expensive.
- It takes more time to produce cylindrical or round features. Use CNC turning for round parts.
- It is expensive to machine tough materials like titanium.
CNC Turning
Turning uses a fixed-cutting tool that feeds into a rotating workpiece on a lathe machine. The cutting tool can move inwards and out while translating side to side making round contour outlines on the workpiece.
Traditionally CNC turning makes complex outlines on round workpieces. CNC turning can automatically produce tapers, grooves and perform parting operations.
Advantages
- CNC turning produces extremely high cylindrical part accuracy
- Higher roundness in parts
- Turning has a better surface finish and quality on round features
Challenges With CNC Turning
- CNC turning cannot produce square features and corners
- Turning operations are for cylindrical workpieces
- The workpiece is held in a chuck which is conventionally smaller than other CNC machines therefore, workpiece size is limited
- CNC turning is not efficient for small workpieces with large quantities because the blank has to be replaced after each part.
CNC Grinding
Grinding is a surface finishing operation that uses abrasive tools and abrasive media to remove material layers from the surface of the workpiece. CNC grinding automates the material removal and offers more control over machining parameters.
CNC grinders can automatically switch grinding tools according to the part profile and operations like centerless grinding, surface grinding, internal grinding, and cylindrical grinding.
CNC grinding is more precise because it automatically controls speed and material removal rate.
Advantages
- Offers the highest level of precision and surface finish up to 2-4 RMS
- Can work with brittle materials that are at risk of breaking with CNC turning and milling
- No damage or stress below the surface layer
- Efficiently removes micron layers with accuracy on surfaces
Challenges With CNC Grinding
- CNC grinding is an expensive operation and requires precise machining parameters by CNC machinists.
- Like most CNC machines, CNC grinders are limited by their size and fixtures
- CNC grinding tools are expensive to replace and maintain.
CNC EDM
CNC electrical discharge machining is the most accurate and precise way to create corners, sharp edges, and parts with zero tolerance. With most CNC machining, it is not possible to achieve a corner without a small radius but discharge machining can produce exact dimensions.
CNC EDM works using a thin wire that produces sparks and removes tiny bits of material from the workpiece. It is also called spark eroding or die sinking.
There is no contact between the wire and the workpiece instead, the high current spart is produced when the wire is near the workpiece. Dielectric fluid flushes away the eroded material and the tool proceeds to machine the part.
Advantages
- Production of custom parts that require zero tolerance and corners
- CNC EDM can easily cut through carbides and tough materials
- It is possible to create intricate internal geometry unlike milling and turning
- There are no cutting forces
Challenges With CNC EDM
- CNC EDM are expensive machines
- Although they are highly accurate, the material removal rate is very low making part production slow
- It is not possible to machine parts made of tungsten, lead, and titanium because they are non-conductive metals
- EDM machining workpieces can produce stresses around the cut parts due to high heat that vaporizes metal.
CNC Laser Cutting
CNC laser cutting involves using a high-intensity and energy laser beam concentrated in a narrow area and converged through lenses to focus on the material to vaporize or melt it.
The controller automatically adjusts the intensity as the laser cutting progresses. CNC laser cutters use a fiber laser to cut through materials like steel, aluminum, and copper.
CNC laser cutting is a versatile CNC machining operation because, through adjustments, you can even etch and engrave materials. There is no contact with the tool, but there are affected zones due to the thermal nature of the machining.
Advantages
- There is no need for tools and custom cutting tools which makes it ideal for saving tooling costs
- It can etch and engrave custom designs
- It is the only CNC machining with minimal material deformation
- No tool change in CNC laser cutting makes it efficient
- It can make cleaner edges compared to CNC plasma cutting
Challenges With CNC Laser cutters
- CNC laser is not useful for materials that reflect light or don’t absorb that wavelength
- CNC laser cutters can only cut materials up to a certain thickness. For carbon steels, this is around 25 mm.
- It is an expensive process in the long run
- Like wire edm, it also produces stresses and physical changes in the surrounding area of the cut.
CNC Routing
CNC routing machine or CNC routers have the same controls as any CNC machine. So, what’s the difference? CNC routers use different tools. CNC routing is typically used for wood or acrylic machining and relies on a spindle with tools like bits, trim bits, surfacer, and ball cutters.
You can use a router to craft intricate designs and shapes on different materials and it is great for large workpieces because it has a large bed. Most routers feature air cooling instead of fluid and oil coolants which limits the material choices.
Advantages
It is a cheaper option for DIY enthusiasts looking to machine plastic, acrylic and soft metals.
Challenges With CNC Laser cutters
- The router capabilities limit it to softer materials like plastics, brass, and copper
- It is fairly large and takes up space
- You cannot replace a milling machine with the router but a CNC mill can perform router tasks.
CNC Plasma Cutting
CNC plasma works with conductive materials and uses a CAD file uploaded to the CNC controller in the form of a G-code. The CNC plasma cutter adjusts the intensity, movement of part, and tool path to make the desired cut.
Plasma cutting uses a high-frequency spark to torch the compressed gas through a nozzle that burns at thousands of degrees. The plasma melts away the metal, cutting it.
Advantages
- It cuts fast through thick materials at higher speeds than EDM and laser cutters
- It can cut up to 1.5 cm thick plates using less power
- You don’t need to remove any coatings or rust on the workpiece
- It can be used in submerged places where other CNC cutters fail
Challenges With CNC plasma machining
- The plasma is thicker than laser and EDM wire tools
- CNC plasma can deform or worse warp the materials
- It has smaller precision for a CNC machining operation and tiny holes are not accurate.
How To Choose The Right Type of CNC Machining
It is important to select the correct CNC machining process for your custom part. Different machining type are suited for various materials and tolerances.
Material–Conductive materials can be machines using CNC EDM machining and non-conductive materials rely on CNC lathes and turn-mills. For highest accuracy in part features use CNC EDMs.
Geometry–For cylindrical parts and contours, CNC turning is best. CNC milling can perform layer cutting for 3 directional cutting.
Tolerance–For sharp tolerance for your part then, CNC grinding provides exact surface tolerances and superior surface finishing.
Sheet metal–CNC plasma cutting is ideal for fast production are needed. While CNC laser cutting for high accuracy and clean edges.
Applications of CNC Machining Type In Industry
Here are some important industries and their CNC applications.
Aerospace
CNC grinding for lightweight and high precision parts because it removes material in micron layer, while CNC turning and milling for structural and engine parts with tight tolerances.
Electronics
Use CNC laser cutting for PCB boards and CNC EDM for precise internal cuts in the PCB boards. Use CNC milling, for enclosures and heatsinks.
Medical
CNC milling and turning make implants. Specifically, milling produces dental implants.
Conclusion
Computer Numerical Code allows for control of the cutting tool in 3 or more axes and the controller allows adjustment of cutting parameters. CNC turning is suitable for round and cylindrical parts and CNC milling is reserved is ideal for complex geometries and flat surfaces.
- CNC Milling is best for multi-axis cutting
- CNC turning is ideal for cylindrical workpieces
- Grinding is a suitable machining type for finishing operations
- CNC laser and plasma cutting are great no-contact machining types
- CNC routing for soft materials like silicon, rubber, and wood.
Understanding the advantages and challenges of each CNC machining type allows manufacturers to select the most effective method for specific parts.
This guide offers an in-depth resource on CNC machining types and helps you decide the best CNC machining process for your part.
FAQ
What are the 5 common types of CNC machines?
The 5 common types of CNC machines are CNC milling machines, CNC routers, CNC EDM, CNC lathe machines, and CNC grinding machines
How many types of CNC operations are there?
There are many CNC operations and the most widely used are CNC milling, turning-milling, CNC plasma cutting, multi-axis CNC machining and CNC grinding.
What is 7 axis machining?
7-axis CNC machining uses 2 more axes than 5-axis CNC. These axes are the C axis around the Z axis and the E axis which produces a twisting motion.
What are metal CNC machining types?
Metal CNC machining is achieved using CNC Mills, CNC lathes, CNC drills, plasma cutters, and grinders.
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