Time to read: 6 min
CNC (Computer Numerical Control) machines are sophisticated pieces of equipment engineered for the automatic production of parts from a diverse array of materials, including metal, plastic, and wood. Among the many configurations of CNC machines, CNC mills and CNC lathes are the most prevalent. While CNC lathes are ideal for working with cylindrical parts, mills are versatile for flat, curved, or angular parts.
In this article, we will detail the various parts that constitute a CNC machine, highlighting the components that are universal across different machine types and those exclusive to specific configurations. For instance, components like tailstocks and headstocks are unique to CNC lathes.
1. Input Device
The "input device" for a CNC machine is the interface through which CNC programs are introduced into the system. This could be a keyboard for manual input of G-code commands, a USB flash drive for transferring a pre-compiled program from another computer, or wireless communication for downloading a program from another system on the local network.
2. Machine Control Unit (MCU)
The MCU, or Machine Control Unit, is the electronic hardware and software suite responsible for reading the G-code from the input device and converting it into executable instructions for the tool drivers. This component is pivotal in the operation of CNC machines. The MCU deciphers G-code coordinates into movements executed by servo motors along the machine's various axes and manages tool changers and coolant activation as directed by the G-code.
3. Machine Tools
"Machine tools" is a collective term for any tool that performs a process on a workpiece, predominantly cutting tools. The form of these tools varies with the type of CNC machine. While CNC lathes utilize stationary tools and rotate the raw material against the tool for cutting, CNC mills move the tools against stationary material. Advanced 5-axis machines can manipulate both the tool and the workpiece, enabling the creation of intricate features in the final product. Machine tools are often stored in "tool libraries," and a tool changer automates the process of removing a tool from the spindle, placing it in the library, and installing the next tool.
4. Driving System
The driving system encompasses the motors that facilitate the movement of the tool along the machine's various axes. In a standard CNC mill, the table moves horizontally along the x- and y-axes, while the cutting tool moves vertically along the z-axis. In contrast, the driving system in a standard CNC lathe moves the cutting tool parallel to the workpiece's rotation axis. Movement in a CNC machine is typically controlled by servo motors, ball screws, and linear guides, ensuring precise positioning of components like the table and spindle.
5. Feedback System
The feedback system is integral for verifying and adjusting the position of mechanical components post-movement. This system utilizes linear or rotary encoders attached to the servo motors to measure the machine's position accurately. Special probing tools are also employed to zero the machine and measure the workpiece during machining, allowing for adjustments to meet dimensional specifications.
6. Display Unit
The display unit is an interface that presents vital information to the operator. While some units feature large, high-resolution screens displaying extensive information, others may have smaller, low-resolution screens showing only essential data. This unit is crucial for operator interaction with CNC machine functions, such as inputting G-code or adjusting machine settings, and also indicates the current operating status of the machine.
7. Headstock
The headstock is a distinctive section of a lathe that houses the main drive, bearings, and gears necessary for rotating the chuck at the required speeds for machining. Typically located on the left side of a CNC lathe, the headstock is usually enclosed and accessible through removable inspection panels.
8. Tailstock
The tailstock is a component exclusive to CNC lathes, designed to axially support long, cylindrical workpieces on one end, with the chuck supporting the other end and rotating the material. The tailstock is crucial for withstanding the forces generated during cutting, preventing material deflection away from the cutter. The raw material is centered on the tailstock quill, which rotates freely within the tailstock.
9. Tailstock Quill
The tailstock quill, located within the tailstock, features a conical end aligned with the spindle and chuck axis. For long-shaft machining, a blind hole is often drilled into the workpiece's end to accommodate the quill for support. The quill has a limited range of motion and is actuated using pneumatic or hydraulic pressure to secure the raw material in place.
10. Chuck
The chuck is a lathe-specific component used to grip the raw material during machining on a lathe. Rotated at high speeds by the spindle, a chuck typically features three or four pneumatically or hydraulically actuated grips. Three-jaw chucks are self-centering, with all grips moving radially in unison. Four-jaw chucks offer individual grip adjustment and are more precise, accommodating eccentric cutting to account for raw material variations.
11. Control Panel
The control panel houses the input device, display unit, keyboard, and additional control buttons, facilitating operator interaction with the CNC machine. Often mounted on an extendable arm, the control panel allows the operator to position the screen for convenient access.
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