Parts of a CNC Milling Machine: Visual Guide
With the new advancements in technology, it is easier than ever to manufacture desired parts. Computer Numerical Control (CNC) has been a game-changer in the manufacturing world. It involves using preprogrammed computer software to control the movement and precision of machine tools.
Common types of CNC machines include; CNC lathe machines, CNC milling machines, CNC routers, 3D printers, and Laser and Plasma Cutters.
In this article, I’ll focus on the basics of CNC milling machines. Keep reading to learn all you need to know – from the parts of a CNC mill to how CNC milling works and everything in between.
Parts of a CNC Milling Machine
CNC milling machines are a popular manufacturing tool with a range of applications across numerous industries. Therefore, it is no surprise that there are many different brands of this equipment and CNC mills will vary from workshop to workshop.
That being said, there are basic components in every CNC mill that allow it to function as intended. I’ve created a list of the standard and most common CNC milling machine parts that you need to know about.
The CNC controller serves as the brain of the machine. It is responsible for controlling the movements and functions of the CNC milling machine.
CNC controllers eliminate the need for manual machining. They read the CNC program or G-code supplied by the input device, and convert these codes into the respective machine movements. The CNC controller then executes the commands by sending the proper signals to the stepper and servo motors. This facilitates efficient and precise machining processes.
Column and Base
The column and base are designed to support all other components in a CNC machine. They also provide rigidity and resist vibrations generated during the machining process. These components are often made of cast iron.
The column and base are also typically filled with epoxy granite which improves their ability to resist vibrations during machining operations. This leads to higher quality machined parts.
The base supports the weight of the whole machine. The column is a vertical component that is connected to the base and it travels along an axis. It holds the tool turret and houses the oil and coolant system.
A knee is a cast iron component that is fixed to the column through a dovetail. It can be moved up and down by a vertical positioning screw. This allows for vertical adjustment of the work table. The knee also provides extra support to the saddle and milling table.
CNC mills are equipped with an automated system that adjusts the position of the knee based on the G-code supplied to the CNC controller. You can also move the knee manually through a hand crank.
The saddle is positioned between the knee and the work table. It is typically made of cast iron and serves to support the work table.
The saddle allows for the vertical and horizontal adjustment of the workpiece.
The feed mechanism of a CNC machine is housed in the knee. This electromechanical system controls the vertical (up and down), longitudinal (left and right), and transverse (in and out) feeds.
The feed mechanism comprises electrical motors that receive signals from the controller and create the desired movement in the workpiece to facilitate the cutting operation.
As the name implies, most machining operations are conducted on the work table. The table is a flat platform used to hold the workpiece during machining. It is mounted on top of the saddle.
In most CNC machines, the worktable is made of cast iron and is equipped with T-slots. These T-slots allow for the workpiece to be secured onto the table through different fastening devices such as clamps or vices.
Work tables are adjustable, and the power feed mechanism is responsible for their movement.
The ram is an adjustable, arm-shaped component that is specific to a vertical milling machine. It’s positioned on top of the column and it serves to hold the milling head.
Just as the ram is specific to vertical milling machines, the overhanging arm is a feature of horizontal milling machines. This cast iron beam is mounted on top of the column and it holds the milling head which supports the milling tool assembly.
The arbor support is a cast iron part that is specific to a horizontal milling machine. It is linked to the spindle via bearings and is responsible for supporting the cutting tool. The arbor support also plays an important role in dampening vibrations generated during machining activities.
A spindle is one of the key components of a CNC system. It consists of a taper that holds the milling tool. The spindle is linked to the main motor of the CNC machine. The CNC controller reads and translates the G-code, rotating the spindle at the specified speed.
Spindle rotation is very important as it drives the cutting tool. This component also houses the milling chuck.
A CNC machine will often utilize an automatic tool changer especially if a workpiece requires different milling operations. This component allows the machine to perform a range of machining operations in a single run, without stopping to engage another cutting tool.
There are different types of tool changers depending on the arrangement of the magazine and the tool holding capacity. For example, an automatic tool changer with a chain magazine can hold over 100 tools while the turret head type accommodates a maximum of 8 tools. A drum-type ATC accommodates a maximum of 3o tools while disc-type ATCs hold 32 to 64 tools.
As the name suggests, the milling tool is the component responsible for the actual cutting operations. This cutting tool is connected to the column, and it performs milling operations based on the G-code supplied by the operator.
There are different cutting tools, each designed for the different types of milling operations. Therefore, your choice of the milling tool depends on the type of operation, i.e., are you performing straddle milling, face milling, angular milling, etc.
Further, different materials will require varying cutting tools. For example, while titanium is machined using rigid tools, copper requires tools with less flute.
The control panel is one of the main components of CNC machines. It provides a gateway for the operator to interact with the CNC machine and control its functions.
The control panel consists of an input device, display unit, keyboard, and other control switches and buttons. It allows the operator to issue commands, select functions, and monitor operations.
Tools Used with CNC Milling Machines
CNC milling tools remove material from a workpiece in a rotary motion. They come in many different designs, each suitable for specific applications.
The choice of a milling tool will depend on the type of machining operation to be performed. For example, face mills are used in face-milling operations to machine flat surfaces. Similarly, end mills are an ideal choice when machining holes and slots on a workpiece. Ball nose mills are a go-to solution when creating intricate geometries, especially in tight spaces.
Other factors to consider when choosing a milling tool are the workpiece material, required surface finish, cutting speed, and material removal per revolution.
CNC milling tools are available in a range of materials, each with its benefits and disadvantages. For example, carbon steel tools are relatively inexpensive but they are only suitable for low-speed operations. Contrarily, high-speed steel (HSS) tools are more efficient in high-speed operations, and they can cut harder materials. Carbide milling tools are designed to handle the toughest of projects and they deliver high quality finishes.
Choosing the right tool for your milling operation is essential to the performance and quality of machined parts.
How Does a CNC Machine Work?
Now that you’re familiar with the standard parts of a CNC mill you may be curious about how this CNC machine works.
So, how exactly does a CNC machine work? In this section, I’ll provide insights into the basic principles and fundamental mechanics of a CNC machine.
With CNC machining, the operator uses a CAD model to generate a custom part. Here is how it works.
The operator converts the CAD model into a set of instructions known as the G-code. Using an input device, this data is entered into the machine control unit (MCU).
The raw material or workpiece is secured onto the work table. A vice may be used to hold the workpiece or it may be directly mounted on the machine bed. To produce highly precise parts, the workpiece needs to be correctly positioned and aligned.
The machine control unit interprets the G-code and transmits the relevant instructions to the driving system. The driving system comprises the motors that move the tool along the different machine axes such as the servo motor.
The machine tool removes material from the workpiece to form the desired part. Typically, machine tools will first remove material quickly with lower precision to create approximate geometry. They’ll then execute a few high-precision passes to produce the desired part.
The feedback system monitors the position and velocity of the machine tool and transmits feedback signals to the machine control unit. In case of errors, the MCU transmits new signals for the necessary adjustments.
After the machining activities, you may need to verify the critical dimensions if tolerances have been provided. The part is then ready for use or post-processing.
In most cases, a CNC milling machine moves along three linear axes; X, Y, and Z axis. In addition to linear motion, advanced systems will also have rotary axes. 5-axis CNC machines can easily manufacture complex geometries.
Factors That Affect The Cost of a CNC Milling Machine
There are different types of CNC milling machines on the market with varying levels of complexity and capability. These differences contribute to the varying price tags of milling machines.
In this section, I’ll explore some of the factors that determine the cost of a CNC mill.
The cost of a CNC mill varies with the size of the work table, the larger the table the more you’ll pay for it. However, larger tables can hold larger workpieces.
If you’re shopping for a CNC milling machine, consider your machining needs and select a table size that best fulfills your requirements.
The spindle power directly affects the milling capability of your machine. However, more powerful spindles require a larger financial investment.
The type of material being machined determines the required spindle power. For example, you’ll need more spindle power to machine a steel workpiece compared to a softer material like plastic.
Also, the cutter size comes into play when deciding on the suitable spindle power. The required spindle power increases as the cutter size increases.
Rigidity of the Frame
Another key factor that impacts the cost of a CNC mill is the frame’s rigidity. The rigidity of a CNC milling machine frame depends on the material of the frame.
A rigid frame results in fewer vibrations during cutting activities, facilitating quality machined parts with better surface finishes.
Since most CNC mills are used to machine metal parts, they typically require a rigid metal frame. Steel is commonly used in CNC mill frames.
Sturdy materials provide better frame rigidity and improve the performance of the mill. However, such mills are generally more expensive.
There you have it! In this article, I have covered the standard CNC milling parts, tools commonly used with the machine, factors affecting the cost of a CNC mill, and how CNC machining works. I hope that you’ve got the basics of this important manufacturing process.
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