Mold processing CNC machining
CNC machining in mold manufacturing utilizes digital control technology to automate the processing of mold parts. By converting machining parameters into digital instructions, it controls machine tools to perform operations such as cutting and grinding. This method offers high precision, efficiency, and flexibility. CNC machining has revolutionized the traditional mold manufacturing model, which relied on manual labor. It is particularly well-suited for machining complex mold parts (such as cavities, cores, and special-shaped cutting edges). It consistently ensures dimensional accuracy and surface quality, and is a core technology in modern mold manufacturing.
CNC machining equipment is plentiful, including CNC milling machines, CNC lathes, CNC grinders, and machining centers. Machining centers are the most widely used in mold processing due to their automatic tool changing and multi-axis linkage capabilities. Vertical machining centers are suitable for machining cavities and flat surfaces in small and medium-sized molds, with spindle speeds reaching 8,000-15,000 r/min and positioning accuracies of ±0.001-±0.005mm. Horizontal machining centers are suitable for machining large molds and complex box-type parts, achieving multi-faceted machining through a rotating worktable, reducing the number of workpiece clampings. Five-axis machining centers can simultaneously control the movement of five coordinate axes and can process complex curved surfaces (such as those found in automotive panel molds). Their machining accuracy reaches ±0.002mm, with a surface roughness of Ra0.8-1.6μm, significantly shortening the processing cycle for complex molds.
Programming for CNC machining is key to achieving automated machining. Machining instructions (G-code and M-code) are generated based on the part’s 3D model (created using CAD software). Programming methods are divided into manual and automatic programming. Manual programming is suitable for simple parts (such as shafts and disks), where instructions are manually entered by calculating the tool path. Automatic programming, on the other hand, utilizes CAM software (such as UG and Mastercam) to automatically generate tool path files and CNC programs, and is suitable for complex parts. During programming, the machining process must be appropriately selected, such as using high feed rates for roughing to quickly remove excess stock, and low feed rates for finishing to ensure accuracy. Tool radius and length compensation must also be set to ensure that the actual machining dimensions match the designed dimensions. For example, when machining the cavity of a mobile phone case mold, UG software is used for automatic programming. The generated program contains over 1,000 instructions, covering processes such as face milling, cavity milling, and contour milling.
The choice of tools and cutting parameters for CNC machining directly impacts machining efficiency and quality. Commonly used tools for mold machining include carbide tools, high-speed steel tools, ceramic tools, and cubic boron nitride (CBN) tools. Carbide-coated tools (such as TiAlN-coated tools) are widely used for roughing and semi-finishing mold steel due to their excellent wear resistance and high cutting speeds (up to 300-600 m/min). Tool geometry should be adjusted based on the material being machined. When machining cast iron molds, the end mill should have a rake angle of 5°-10° and a clearance angle of 8°-12°; when machining aluminum alloy molds, a rake angle of 15°-20° is recommended to reduce cutting forces. For roughing, the feed rate is 0.2-0.5 mm/r and the cutting depth is 2-5 mm; for finishing, the feed rate is 0.05-0.1 mm/r and the cutting depth is 0.1-0.5 mm. Optimizing these parameters can improve machining efficiency by 30%-50%.
The advantages of CNC machining in mold manufacturing are reflected in several aspects: First, stable machining accuracy eliminates manual errors, achieving dimensional consistency within ±0.005mm across parts within the same batch; second, high production efficiency: machining centers can operate continuously 24 hours a day, reducing the machining time for complex cavities by over 50% compared to traditional methods; third, flexibility: simply modifying the CNC program can adapt to the machining of different parts without having to replace a large number of fixtures; and fourth, it can process complex structures that are difficult to achieve with traditional methods, such as deep and narrow grooves and micro-cavities (0.5-2mm in diameter). For example, the cavity of a car bumper mold was machined using a five-axis machining center in just three days, compared to over 10 days with traditional milling, and with superior surface quality. With the advancement of CNC technology, intelligent CNC machining (integrated with the Internet of Things and artificial intelligence) is increasingly being applied to mold manufacturing, enabling real-time monitoring and adaptive adjustments during the machining process, further improving machining capabilities.
