During CNC lathe machining of thin-walled parts, vibration-induced deformation is a key issue affecting machining accuracy and surface quality. Due to their lack of rigidity, thin-walled parts are prone to elastic deformation under cutting forces, leading to dimensional errors, shape distortion, and even machining failure. To address this issue, coordinated improvements are required across multiple dimensions, including process design, tool selection, fixture optimization, cutting parameter control, and vibration suppression technologies.
During the process design phase, sequential machining should be employed to reduce the risk of deformation. During roughing, a large cutting allowance and clamping force should be used to quickly remove excess material; during finishing, clamping force should be reduced to avoid deformation caused by residual stress generated during roughing. For example, for internal hole machining, the outer diameter and end faces can be rough-turned first, followed by finish turning the inner hole. This step-by-step stress relief reduces deformation accumulation. Furthermore, the use of a shaft guard can effectively control external machining accuracy. A thin-walled sleeve with a pre-machined inner hole is inserted into the shaft guard and secured with front and rear centers to prevent deformation caused by clamping forces during external machining.
Optimizing tool geometry is crucial for reducing vibration. Increasing the tool's rake angle improves cutting edge sharpness and reduces cutting forces; decreasing the tool's clearance angle increases the contact area between the tool and the workpiece, reducing vibration transmission through vibration-damping design. For example, when fine-turning thin-walled workpieces, the toolholder must have sufficient rigidity and the wiper blade length must be kept within a reasonable range to avoid excessive length, which can exacerbate vibration. Furthermore, the tool's lead angle must balance radial and axial cutting forces. For thin-walled parts, increasing the lead angle can reduce radial forces, thereby reducing vibration.
Improving the fixture and clamping method is key to suppressing vibration. Traditional three-jaw chucks are prone to localized deformation due to three points of contact. However, sector-jaw, four-jaw, or six-jaw chucks increase the number of contact points, distributing the clamping force and reducing pressure per unit area. The use of collet-type chucks and pneumatic/manual chucks can further improve workpiece rigidity by increasing the force-bearing area and precisely controlling the clamping force. Furthermore, diaphragm chucks, which utilize diaphragm deformation to fine-tune the clamping force, are suitable for machining thin-walled parts that are sensitive to deformation.
Properly setting cutting parameters is key to balancing efficiency and quality. Cutting speed, feed rate, and back-cut depth need to be dynamically adjusted based on material properties and workpiece structure. For example, during roughing, a larger back-cut depth and feed rate can be used, but excessive cutting forces that cause vibration must be avoided. During finishing, deformation can be controlled while maintaining surface quality by reducing back-cut depth and increasing cutting speed. For thin-walled parts, it is recommended to maintain feed rates within a reasonable range, and to minimize back-cut depth during finishing to reduce cutting force impact.
The comprehensive application of vibration suppression technologies can significantly improve machining stability. Filling the interior of thin-walled workpieces with damping materials such as soft rubber tubing, cotton yarn, or foam can absorb vibration energy and reduce deformation. Furthermore, installing dampers and vibration isolation pads can block vibration transmission paths and reduce the risk of resonance between the machine tool and the workpiece. For tools with long overhangs, damped milling cutters or modular toolholder systems can reduce vibration caused by insufficient tool rigidity through dynamic balancing.
When CNC lathe machining thin-walled parts, preventing vibration-induced deformation must be implemented throughout the entire process. From process design and sequential machining, tool parameter optimization, fixture improvement, precise cutting parameter control, to the comprehensive application of vibration suppression technology, every step must focus on reducing cutting forces and improving workpiece rigidity. Only through systematic technical collaboration can high-precision and high-stability machining of thin-walled parts be achieved.
