In precision hardware machinery parts processing, vibration is a key factor affecting machining accuracy and surface quality. Its generation stems from multiple factors, including the interaction between the tool and workpiece, insufficient machine tool dynamic characteristics, and rigidity defects in the process system. To effectively reduce vibration, a systematic solution needs to be constructed from dimensions such as tool optimization, machine tool adjustment, process parameter control, and fixture design.
Optimizing tool geometry parameters is the primary step in suppressing vibration. The tool tip radius must be properly matched with the depth of cut: when the depth of cut is less than the tip radius, radial force dominates the cutting process, easily leading to the "tool not being held down" phenomenon; while when the depth of cut exceeds the tip radius, axial force becomes dominant, significantly improving cutting stability. For example, in the finishing of pin-type parts, adjusting the fillet radius from 0.4mm to 0.2mm fundamentally solves the vibration mark problem. The selection of the principal cutting edge angle is equally crucial; increasing the principal cutting edge angle can strengthen the axial cutting force and weaken the radial force, thereby reducing the risk of vibration. When turning slender shafts, using a 90° lead angle tool with a flexible center effectively disperses the cutting load. When machining thin-walled workpieces, a 90° square shoulder end mill reduces vertical pressure, minimizing vibration.
Enhancing the dynamic characteristics of the machine tool is the core foundation for improving vibration resistance. The machine tool spindle system needs to increase contact stiffness by reducing bearing clearance and applying preload, while optimizing the clearance fit between the spindle and bearings, and between the slide and wedge, to avoid forced vibration caused by mechanical loosening. For deep hole machining scenarios, using intermediate guide supports or damped vibration-reducing turning tools can significantly improve the rigidity of the tool overhang. For example, deep cavity turning tools with built-in "real-time response" damper modules improve machining stability by more than 30% by absorbing high-frequency vibration energy. Furthermore, optimizing the rigidity of the machine tool foundation structure is also crucial. Cast iron, due to its excellent vibration absorption properties, is often used to manufacture key components such as machine feet and bearing housings.
Precise control of process parameters is a key means of balancing cutting efficiency and vibration risk. While reducing cutting speed can decrease cutting force, it's necessary to simultaneously increase the feed rate to maintain machining efficiency and avoid self-excited vibrations caused by cutting force fluctuations. In milling, using non-uniform pitch tools can interrupt harmonic effects, especially suitable for large cut widths and long overhangs. For multi-tooth end mills, cutting power can be reduced by disassembling inserts, but it's crucial to ensure a uniform feed per tooth. For example, a 10-flute end mill should be disassembled into 5 flutes, requiring removal of every other insert to maintain dynamic balance. Furthermore, using large programmable fillets and reducing the feed rate at corners can prevent impact vibrations caused by sudden changes in cutting direction.
The rigidity design of the fixture system is crucial for ensuring workpiece stability. Four-jaw chucks, due to their higher rigidity, are superior to three-jaw chucks in precision machining; direct screw mounting of the workpiece to the faceplate further improves positioning accuracy. For slender shaft parts, auxiliary supports such as the center rest or follow rest can effectively disperse cutting forces, preventing bending vibrations caused by insufficient workpiece rigidity. In tool clamping, open collets, using a ring-like fixing method, offer more than twice the rigidity compared to screw clamping, making them particularly suitable for high-precision applications such as internal turning.
Through the synergistic effect of tool geometry optimization, machine tool dynamic strengthening, precise control of process parameters, and fixture rigidity design, vibration issues in precision hardware machinery parts processing can be systematically resolved. This process requires not only theoretical guidance but also dynamic adjustments tailored to specific machining scenarios. For example, tool parameters can be flexibly selected based on material hardness, cutting allowance, and equipment performance, ultimately achieving a dual improvement in machining accuracy and efficiency.
