Milling Made Easy: A Beginner’s Guide to CNC Milling

CNC milling process

The initial stages may seem complex and challenging if you enter the vast milling field. CNC technology plays a vital role in the automation of the manufacturing industry. It involves using computer programs to control the movement and operation of machines, resulting in accurate and consistent results. Manufacturers use a variety of CNC milling operations to shape the workpiece depending on the type of material, design features and complexity. However, this article will only cover the milling process, including its steps, various operations, types of milling and everything you need to know!

What is CNC milling?

CNC milling is a subtractive manufacturing approach that involves removing material to transform a workpiece into a desired shape using a CNC router. The material removal process uses CNC cutting tools such as end mills and drills, where the cutting tools are controlled and operations are run by a computer program that determines the tool path and cutting parameters such as cutting speed and depth of cut.

The milling process uses CNC milling machines, which are highly versatile and allow a wide range of milling operations. They are capable of cutting a variety of different materials, from plastics and composites to metals and alloys. Typically, CNC milling technology can produce parts with tolerances ranging from ±0.001 inch to ±0.005 inch. However, the CNC router must be exact and accurate to achieve these tolerances.

Difference Between CNC Milling and CNC Turning

CNC milling and turning are two computer-controlled machining processes that differ significantly in their ability to create different shapes and features, the number of axes they operate on, and the types of workpieces they can handle. Therefore, understanding the differences helps select the appropriate machining process for a particular job.

Workbench: CNC Milling vs. Turning

CategoriesMillingCNC turning
Cutting toolRotary multi-point cutting toolSingle-point cutting tool
TreatmentMaterial is removed from the workpiece using rotating cutting tools controlled by a computer program.Material is removed from the rotating workpiece using a stationary cutting tool controlled by a computer program.
ApplicationsManufacturing of a wide range of parts, including complex shapes and characteristics.Production of cylindrical parts such as shafts, bushings and flanges, often for high-volume production.
MaterialsCan work with various different materials, including metals, plastics, composites, etc.
PeculiaritiesCapable of producing pockets, grooves, holes, threads, chamfers and complex 3D shapes.Possibility of producing threads, grooves, chamfers and other cylindrical elements.
AdvantagesVersatility for complex shapes and functions. Accuracy and repeatability. And Flexibility in the choice of materials.Efficiency in large-scale production. Easy to install and operate. Cost-effective for large-scale production.
RestrictionsCost, especially for large or high-precision machines, setup time for tool changes and workpiece alignment, and material waste during the milling process.Limited to the production of cylindrical shapes and elements. Less versatility for complex parts. It is less accurate for complex parts with tight tolerances.

Components and Features of CNC Routers

Starting the CNC milling journey inevitably leads to understanding the intricacies of the machine. Although each piece looks like a simple metal part, they form a symphony of precision and accuracy. Let’s look at the key components and their essential roles.

Table: Key components of CNC milling machines

ComponentMain roleFunctionality and importanceMaintenance and Additional Notes
DesktopBasics of the milling processHolds the workpiece and provides stability. Provides immobility of the workpiece when interacting with the tool.Must remain in excellent condition, without obstacles or debris.
SaddleA bridge between desktop and machineEnsures proper alignment while supporting the workbench. Maintains balance and stability of the installation.It is vital to prevent unnecessary displacement or movement during operations.
knee-Raising or lowering the work tableAdjusts the height of the desktop. Indispensable for workpieces of various sizes and specific cutting depths.Presented in the form of CNC machine legs, facilitating height adjustment.
ColumnCNC Router BasicsProvides support for spindle, elbow and other components. Provides structural integrity.Its reliability and rigidity are essential in ensuring a stable milling process.
SpindleOperates the machineDetermines the rotation and movement of the tool. Cut quality is affected by speed, alignment and position.Regular maintenance and calibration are critical for optimal performance.
Machine ToolInteracts with the workpiecePhysically shapes the workpiece. Depends on the milling operation, such as drills and end mills.Each tool is designed for a particular task, ensuring precision in milling processes.

To appreciate these components, it is essential to understand their interactions. Their coordinated movement, guided by the CNC machine software, determines the success of the milling operation. For example, as the spindle controls the movement of the machine, the work table, supported by the saddle and adjusted by the knee, holds the workpiece securely. This synchronized ballet ensures perfect interaction between the machine and the workpiece while the column ensures stability.

CNC Router Parts

What are small CNC machines?

A small CNC router is a type of milling machine smaller than traditional CNC routers. This makes small CNC routers more suitable for home workshops or small businesses. Additionally, they can work with metal, plastic, and wood to create precise cuts, holes, and shapes with high precision.

Small CNC machines

Below are a few examples of using a small CNC router.

● Non-standard parts for machinery or equipment

● Rapid Prototyping for New Products

● Decorative objects such as signs or sculptures

● Jewellery and other small items

● Parts for model aeroplanes or other hobby projects

● Overall, a small CNC router can be a versatile tool for anyone who aspires to create precise parts or complex-shaped objects.

A small CNC router can be a versatile tool for creating small parts or complex-shaped objects. Additionally, it can be a great piece of equipment for your workshop to learn and understand how CNC milling operations work.

Types of CNC Milling Operations

Different types of CNC milling operations are designed to achieve specific results depending on the type of material. These operations differ in the type of cutting tool used, cutting direction, depth of cut, speed and feed rate, and other processing parameters. Additionally, selecting the correct milling operation for a given job is essential to ensure optimal efficiency, accuracy and quality.

Let’s discuss the basic CNC milling operations used in manufacturing.

1. Face milling

The face milling operation involves cutting a flat surface perpendicular to the cutter’s axis of rotation. An end mill contains teeth on the periphery and on the end of the cutter, which allows cutting in both axial and transverse directions.

Used to create a flat surface on a workpiece or level its top. Typical face milling applications include engine blocks, cylinder heads, and other flat surfaces on various workpieces.

2. Peripheral milling

This fast and precise processing method produces high-quality surfaces while avoiding surface roughness. Peripheral milling involves trimming the outer edges of a workpiece using a cutting tool that rotates around the perimeter of the workpiece.

This operation creates complex contours or shapes outside a workpiece, such as gears, splines, and profiles.

3. Slot milling

As the name suggests, slot milling involves cutting a narrow slot or groove into the surface of a workpiece. Depending on the design features, the slots can be of different depths and widths. Slot milling uses cutting tools such as end mills, drill bits, and slot drills. The cutter rotates and grips the workpiece, removing material in a straight line to create a groove.

4. Flat milling

Flat milling is a type of milling operation that creates a flat surface parallel to the cutter’s rotation axis. During operation, the cutter rotates and engages the workpiece, removing material in a flat plane. It can be used to create a flat surface on a workpiece, to level the top of a workpiece, or to cut a groove or groove.

5. Milling pockets

Pocket milling is suitable for creating a closed pocket or cavity on the surface of a workpiece. Various cutting tools such as end mills, ball end mills, and slot drills can create various pocket shapes, including rectangular, round, or irregular. They can be of varying depths and widths.

6. Milling the form

Shape milling is typically used when making parts with complex shapes because it allows the workpiece to be trimmed to a specific shape or contour. The operation uses a tool that matches the desired contour, allowing the device to create a detailed profile or design on the surface of the workpiece.

7. Other milling operations

There are many other milling operations, such as drilling, profiling, thread milling, plunge milling, corner milling and sliding milling.

Steps to Getting Started with CNC Milling

The complex CNC milling process becomes logical and accessible when we break down the procedures into individual steps. Let’s discuss the basic steps required to start the CNC milling process.

Step 1: Complete the drawing

Before beginning the actual milling process, it is essential to have a clear plan or digital drawing of the desired end product. This drawing serves as a road map to guide the CNC machine.

CAD: Computer-Aided Design (CAD) software has become a touchstone in the modern era. Such tools allow you to create accurate digital sketches, ensuring the most minor details are considered.

Detailing: Every curve, angle and measurement in the drawing is translated into machine movements. Thus, ensuring accuracy at this stage is vital.

Consultation: Interaction with experts or fellow designers can help improve the drawing. Good design is thought through to the smallest detail.

During the pre-milling phase, ensuring that all measurements are dimensionally accurate to the desired specifications is critical. Some complex designs may require adjustments to milling capabilities. Additionally, you must ensure that the selected file format is compatible with the specific CNC machine software.

Step 2: Select Material

It is equally important to choose a suitable material. The choice can be influenced by various factors, from tool life to the characteristics of the finished product. The milling requirements for materials such as titanium will differ significantly from softer materials such as pine wood. Here’s a quick breakdown of everyday materials:

Material: TypeGeneral Applications Milling Recommendations

Material typeCommon Use CasesMilling Recommendations
AluminumAircraft components, BanksLightweight, easy to grind, can oxidize
SteelAuto Parts, ToolsDurable, more rigid tools are available in a variety of alloys.
Plastics (eg PVC, acrylic)Signs, ToysGenerally easier to mill, there is a possibility of melting if overheated.
TreeFurniture, SculpturesDepends on hardness, the possibility of splitting

Step 3: Set Options

As mentioned earlier, three factors come into play here: feed rate, spindle speed and depth of cut. But these are only some of the parameters that should be considered.

Tool Path: Determining how the machine will move through the material is determined based on your CAD drawing.

Coolant Flow: Some milling operations require coolant to dissipate heat. The speed and type of flow can be critical.

Tool Selection: The selection of suitable milling tools – end mills, ball mills, etc. – becomes essential depending on the material and complexity of the machining.

Statistics can better illustrate the importance of ideal parameters. For example,” emphasized that almost 28% of inconsistencies in CNC milling occur due to incorrect parameter settings.”

Step 4: Start Milling

CNC router in action

The preparation is complete; it’s time to bring the drawing to life.

Machine Calibration: Before actually milling, it is critical to calibrate the CNC machine to ensure accuracy.

Safety Protocols: Follow safety procedures at all times. This includes wearing protective equipment and ensuring the workplace is free of potential hazards.

Monitoring: While the machine is grinding, constantly monitor the process. Correct any deviations or discrepancies during the process immediately.


Starting your CNC milling journey may seem daunting at first, but with the proper guidance, it becomes a rewarding endeavour. This beginner’s guide gives you a solid foundation to begin your CNC journey. Always remember: every expert was once a beginner. So, practice, learn, and soon you will master the art of CNC routing. And if you are looking someone to take your legwork, there is no better place than Zintilon! They offer CNC milling services and cater to all kinds of needs and demands.

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