Riveting deformation is a common problem that can lead to part rejection, assembly interference, reduced dimensional accuracy, and decreased strength. The root cause lies in unbalanced forces acting on the workpiece. A systematic solution requires a collaborative approach from two dimensions: process parameter control and mold design optimization, thereby achieving precise management of “force.”
- Root Cause Analysis:
Bending deformation: Caused by non-perpendicular axial forces. Misalignment of the punch axis or non-parallel anvil support generates lateral force components, which act as a lever, causing the workpiece to bend.
Local bulging or indentation: Caused by uneven radial expansion forces. When the rivet material’s flow is restricted within the hole or the anvil support is insufficient, pressure can lead to uncontrolled plastic flow in localized areas.
Thermally induced deformation: Local heat generated during high-speed or large-deformation riveting can lead to uneven thermal expansion, resulting in residual stress and deformation after cooling.
- Process Parameter Optimization Strategies:
Optimizing the force-displacement curve: Using “skillful force” rather than “brute force,” intelligent curve programming for servo-controlled orbital riveting machines can significantly reduce the risk of deformation and avoid single high-impact forces. Use multi-stage or ramped force curves. For example, set a lower initial contact force, then smoothly increase to the forming force, and finally maintain it briefly. This allows the material to flow sequentially and smoothly.
Precise speed control: Reducing the punch speed at the moment of contact can significantly reduce dynamic impact. Maintaining a constant speed during the forming stage helps to ensure uniform stress distribution.
Adaptive function: The machine’s adaptive algorithm can automatically find the optimal balance between sufficient forming force and minimum part deformation during trial production.
- Mold and Fixture Design Optimization:
Ensure absolute alignment: The concentricity error between the punch and the anvil must be minimized. Use high-precision quick-positioning devices to ensure alignment of the punch and workpiece.
Secure part fixation: Ensure that the fixture can completely fix the workpiece and provide sufficient support force to ensure that the rivet is fully supported during the riveting process without uncertain displacement.
Scientific punch design: The shape of the punch head directly affects the direction of material flow. Optimized design for specific materials can guide the metal to efficiently fill the cavity instead of being harmfully squeezed to the sides.
Conclusion:
Preventing deformation is a complex process. ShunTai Technology’s ST-MSF series, with its precise programmable control, combined with professional mold design services, provides customers with a complete solution from process to tooling, ensuring the riveting quality of complex and precision parts.