For products with high aesthetic requirements, rivet adhesion or riveting galling is a fatal defect and an accelerating factor in abnormal tool wear. Overcoming adhesion requires a systematic approach from the perspectives of materials science, surface engineering, and tribology.
- Microscopic Mechanism of Adhesion Formation
Under the high pressure and local temperature rise during riveting, the oxide film at the contact points ruptures. Intense plastic deformation and friction cause the two surfaces to diffuse into each other, forming microscopic “welds.” When relative motion occurs between the mold and the workpiece, these welds undergo shear fracture, causing the material to be “torn” and adhere to the mold surface, resulting in adhesion.
- Four Key Factors Leading to Adhesion
Improper Matching: Similar or mutually soluble hardness between the mold and workpiece materials makes diffusion and adhesion highly likely.
Poor Surface Quality: Low surface finish, microscopic defects, or insufficient hardness of the mold working surface provide “gripping points” for the workpiece to tear.
Lubrication Failure: Lack of effective lubrication leads to hard friction and a sharp increase in temperature.
Improper Parameters: Excessive force or speed generates frictional heat, softening the material and exacerbating adhesion.
- Systematic Solutions
Follow the “Hardness Difference” Principle: Ensure the mold hardness is significantly higher than the workpiece material.
Reduce Material Inter-solubility: Select mold materials or coatings with different crystal lattice structures than the workpiece to minimize atomic inter-diffusion.
Ultra-precision Machining: Polish the mold working surface to a mirror finish, significantly reducing microscopic contact points.
Anti-friction Coatings: High-performance coating treatments, such as vapor deposition, titanium nitride, and titanium carbonitride, improve hardness and reduce friction to prevent adhesion.
Gentle Force Curve: Utilize the programmable control function of the servo riveting machine to achieve flexible contact.
Optimize Riveting Motion Trajectory: Adjust the technical parameters of orbital riveting to find the optimal trajectory.
Ensure Effective Lubrication: Use specialized extreme pressure lubricants when the process allows.
- Shuntai Technology’s Collaborative Support
Shuntai Technology not only provides servo orbital riveting machines capable of precise and gentle control but also offers one-stop solutions based on the customer’s materials. This includes mold manufacturing, mirror polishing, and coating services to assist customers in solving adhesion problems.
Conclusion:
Overcoming rivet adhesion requires a comprehensive strategy. Through scientific material matching, meticulous surface treatment, gentle process control, and rigorous tool maintenance, it is entirely possible to achieve flawless, high-quality riveting, thereby improving product quality and extending tool life.