CNC milling is a machining process that uses a high-speed rotating multi-edged tool to cut a stationary workpiece. Its most significant characteristic is that the tool performs the main rotary motion, while the workpiece (or tool) performs linear or curved feed motions in the X/Y/Z directions. It excels at machining planes, grooves, cavities, complex curved surfaces, and contours, and is particularly suitable for manufacturing non-rotating parts such as box-shaped, plate-shaped, and mold-shaped components. A CNC milling machine is a machine tool that uses numerical control technology to perform milling operations. It can automatically control the tool position according to a pre-programmed sequence, achieving automated machining of complex, high-precision parts.
Common Process Types: Common milling methods include face milling, contour milling, cavity milling, and hole machining. Face milling aims to quickly obtain large-area, high-precision planes; a typical tool is a face milling cutter. Contour milling is used to machine the external or internal contour shapes of parts; a typical tool is an end mill. Cavity milling is used to remove material from closed or open areas to form recesses or cavities; a typical tool is an end mill. Hole machining includes drilling, reaming, boring, and tapping. Typical tooling includes drills, reamers, taps, and boring tools.
Tooling System: Key tool types in CNC milling include end mills, face mills, ball nose end mills, ball end mills, and special-purpose end mills. Face mills are used for large-area planar milling, offering high efficiency, high material removal rate, and good surface quality. End mills are categorized based on whether the end cutting edge crosses the centerline: those for vertical cutting and those for contour and stepped surface machining. Ball end mills are used for machining spatial curved surfaces and complex shapes. High-speed CNC milling machines utilize HSK tool holders to achieve high-efficiency machining.
Cutting Parameters and Strategies: Core cutting parameters include cutting speed, spindle speed, feed per tooth, depth of cut, and width of cut. Cutting speed is the linear velocity of the tool edge relative to the workpiece. Spindle speed is calculated based on the cutting speed and tool diameter. Feed per tooth is the thickness of material cut into each cutting edge per revolution. Depth of cut and width of cut together determine the material removal rate and cutting load. Roughing aims for high metal removal rates, allowing for large depth of cut, large cut width, and moderate feed per tooth. Finishing prioritizes surface quality, requiring small depth of cut, small step distance, appropriate feed per tooth, and high speed. On CNC machine tools such as machining centers, climb milling (co-directional milling) is typically the preferred cutting method due to its superior cutting effect and surface quality, provided the machine tool, fixture, and workpiece conditions permit. Conventional milling (reverse milling) is only suitable for specific scenarios such as machine tool feed mechanism backlash, workpiece surface hardening, or machining hard materials.
Equipment Composition and Classification: CNC milling machines consist of hardware and software. Core hardware components include the bed, spindle box, worktable, servo motor, and constant power speed control system. The core software is the CNC control system. Machining centers are machine tools based on CNC milling machines, equipped with automatic tool changers. The development trend of modern high-end CNC systems includes online monitoring of cutting forces, tool wear, vibration, and other conditions, and the realization of intelligent adaptive control.
