A machining center is a type of CNC machine tool. CNC milling machines without a tool magazine are called CNC milling machines, while those equipped with a tool magazine are referred to as machining centers or CNC machining centers. Machining centers, also known as Computerized Numerical Control Machines (CNC), are highly efficient automated machine tools composed of mechanical equipment and numerical control systems used for processing complex-shaped workpieces.
What Equipment Does a Machine Tool Include?
Machining methods such as turning, milling, planing, grinding, boring, drilling, electrical discharge machining (EDM), sheet metal shearing, bending, and laser cutting are all part of mechanical machining. Mechanical machining is the process of transforming metal raw materials into the required shapes, encompassing both dimensional accuracy and geometric precision. Equipment capable of performing these functions is referred to as machine tools, with CNC machine tools being an advancement over conventional ones, using digital control systems.
After installing a CNC system on a machine tool, it becomes a CNC machine tool. Of course, the development from conventional machine tools to CNC machine tools is not as simple as merely adding a system. For example, the transition from a milling machine to a machining center involves changes in the machine’s structure, with the key addition being the tool magazine, significantly enhancing precision. The primary function of a machining center is milling, boring, and drilling.
Machining center definition
When discussing CNC equipment, it primarily refers to CNC machine tools and machining centers. In general, a machining center is a type of CNC machine tool. A CNC milling machine without a tool magazine is called a CNC milling machine, while one with a tool magazine is referred to as a machining center or CNC machining center. A machining center is equipped with a tool magazine and has an automatic tool change function, allowing for multi-process machining of workpieces after a single clamping. It is a highly integrated electromechanical product, where the CNC system controls the machine tool to automatically select, change, and adjust tools, spindle speed, feed rate, and more, completing various processes such as drilling, boring, milling, tapping, and more. This significantly reduces workpiece clamping time, measurement, machine tool adjustments, and other auxiliary processes, making it highly cost-effective for parts with complex shapes, high precision requirements, and frequent model changes.
Classification of Machining Centers by Number of Axes
Machining centers can be classified into three-axis, four-axis, and five-axis machining centers based on the number of axes.
Three-axis CNC Machining Centers
Three-axis CNC Machining Centers milling remains one of the most popular and widely used machining processes. In 3-axis machining, the workpiece remains fixed, and the rotating tool cuts along the x, y, and z axes. It is a relatively simple form of CNC machining, suitable for manufacturing products with simple structures. However, it may not be ideal for processing complex geometric shapes or components.
As it can only cut along three axes, the machining speed may be slower than that of four-axis or five-axis CNC, as the workpiece may require manual repositioning to achieve the desired shape.
Four-axis CNC Machining Centers
Four-axis CNC Machining Centers milling adds a fourth axis to the cutting tool’s motion, allowing rotation around the x-axis. Thus, there are four axes – x, y, z, and a (rotating around the x-axis). Most four-axis CNC machines also allow workpiece rotation, referred to as the b-axis, enabling the machine to function as both a milling machine and a lathe.
When drilling on the side of a workpiece or on a curved surface of a cylinder, 4-axis CNC machining is the preferred choice, significantly speeding up the machining process and achieving high machining accuracy.
Five-axis CNC Machining Centers
Five-axis CNC Machining Centers milling adds an additional rotating axis compared to four-axis CNC. The fifth axis revolves around the y-axis, also known as the b-axis. The workpiece may also rotate on some machines, sometimes referred to as the b-axis or c-axis.
With 5-axis CNC machining offering high versatility, it is used to manufacture complex precision parts, such as the universal 5-axis gantry machining center shown below. Examples include medical components for artificial limbs or bones, aerospace parts, titanium components, oil and gas machinery parts, military products, and more.
Classification of Machining Centers by Table Position
Machining centers are generally classified based on the relative position of the spindle to the worktable, divided into horizontal, vertical, and universal machining centers.
- Horizontal machining center: The spindle axis is parallel to the worktable. It is mainly used for processing box-type components.
- Vertical machining center: The spindle axis is perpendicular to the worktable. It is suitable for processing plate-like, disc-like, mold, and small-sized complex components.
- Universal machining center (also known as multi-axis linked machining center): By controlling the angle of the spindle axis and the worktable’s rotational axis, it can perform complex spatial surface machining. It is suitable for processing components with complex spatial surfaces, such as impellers, rotors, molds, cutting tools, and more.
Top 5 Significant Differences Between Machining Centers and CNC Mill
Machining Centers and CNC Mills are both types of Computer Numerical Control (CNC) machine tools used in the manufacturing industry. While they share some similarities, they have distinct differences in their design, capabilities, and applications. Here are the key differences between Machining Centers and CNC Mills:
Differences 1#: Design and Structure
- Machining Center: A machining center is a highly versatile CNC machine tool that combines the functionalities of a CNC mill, CNC drill, and sometimes a CNC lathe. It is designed with an automatic tool changer (ATC) and may also have additional features like a rotary table or tilting head to enable multi-axis machining. Machining centers are used for complex and multi-process machining of workpieces.
- CNC Mill: A CNC mill is a specific type of machining center that is primarily designed for milling operations. It is equipped with a rotating cutting tool that moves along the x, y, and z axes to remove material from a workpiece, shaping it into the desired form.
Differences 2#: Functionality
- Machining Center: Besides milling, machining centers can perform various other operations like drilling, boring, tapping, reaming, and turning (if equipped with a lathe spindle). They are capable of multi-axis simultaneous machining, making them suitable for complex parts with intricate geometries.
- CNC Mill: CNC mills are primarily used for milling operations, where the cutting tool removes material from the workpiece to create flat surfaces, contours, and pockets. While some CNC mills may have limited additional functionalities, their main focus is on milling tasks.
Differences 3#: Workpiece Complexity
- Machining Center: Machining centers are ideal for processing complex-shaped workpieces that require multiple operations on different surfaces. They are commonly used in industries like aerospace, automotive, and medical, where precision and intricate designs are crucial.
- CNC Mill: CNC mills are best suited for simpler workpieces with 2D or 2.5D features. While they can handle some level of complexity, they are not as versatile as machining centers for handling intricate 3D shapes or performing complex multi-process machining.
Differences 4#: Tool Capacity
- Machining Center: Machining centers are equipped with a tool magazine that holds multiple cutting tools, allowing for automatic tool changes during operations. This tool-changing capability enables machining centers to perform various operations without manual intervention.
- CNC Mill: CNC mills may also have an ATC, but their tool capacity is typically lower compared to machining centers. They are more commonly used for specific milling operations that do not require frequent tool changes.
Differences 5#: Versatility
- Machining Center: Machining centers are highly versatile and can handle a wide range of workpiece geometries and materials. Their multi-axis capabilities make them suitable for intricate and complex parts.
- CNC Mill: CNC mills are more specialized in milling operations and are suitable for simpler workpieces. They are commonly used for rapid material removal and creating basic geometries.
Summary
A machining center is a type of CNC machine tool. Without a tool magazine, it is referred to as a CNC milling machine, while one with a tool magazine is called a machining center or CNC machining center. A machining center is equipped with a tool magazine and an automatic tool change function, enabling it to perform multi-process machining after a single clamping. It is a highly efficient, versatile, and precise CNC machine tool used for producing complex-shaped workpieces in various industries.
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