What are the key points of quality control in the rivet pressing process?
The materials of riveted components and workpieces to be riveted shall comply with design requirements, possessing corresponding mechanical properties such as strength, hardness, and toughness, as well as good stamping performance and surface quality. For instance, for stainless steel riveted components, their corrosion resistance must meet the requirements of the service environment.
The dimensional accuracy of raw materials directly affects the quality of rivet pressing. The dimensional tolerances of riveted components, such as outer diameter, inner diameter, and length, shall be within the specified range. The dimensions of workpieces to be riveted, including thickness and hole diameter, also need to be strictly controlled to ensure the fitting accuracy during rivet pressing.
The mold structure shall be designed based on the shape, size of riveted components and workpieces to be riveted, as well as the requirements of the rivet pressing process. For example, for riveted components with complex shapes, multi-station molds or special positioning devices may be required to ensure accurate rivet pressing positions and avoid deviation or skewing.
The machining accuracy of molds is crucial to the quality of rivet pressing. The accuracy indicators of molds, such as cavity size, surface roughness, perpendicularity, and parallelism, shall meet design requirements to ensure the dimensional accuracy and surface quality of riveted components. Meanwhile, the mold manufacturing materials shall have sufficient strength and wear resistance to guarantee the service life and stability of the molds.
Appropriate rivet pressing equipment shall be selected according to factors such as the material, size, and production batch of riveted components. Common types of rivet pressing equipment include pneumatic rivet presses, hydraulic rivet presses, and electric rivet presses. For example, hydraulic rivet presses shall be selected for large-sized riveted components or occasions requiring large rivet pressing force; pneumatic rivet presses or electric rivet presses can be used for small-sized riveted components with high production efficiency requirements.
Before rivet pressing, the equipment shall be commissioned to ensure that various parameters of the equipment, such as rivet pressing force, stroke, and speed, can be accurately controlled and meet the process requirements. At the same time, check whether the transmission system and control system of the equipment are operating normally to avoid affecting the quality of rivet pressing due to equipment failures.
Rivet pressing force is one of the key parameters affecting the quality of rivet pressing. Excessive rivet pressing force may lead to excessive deformation of riveted components, damage to workpieces to be riveted, or increased mold wear; insufficient rivet pressing force may result in insecure connection between riveted components and workpieces to be riveted. The appropriate rivet pressing force shall be determined through tests and calculations based on factors such as the material, thickness, and size of riveted components and workpieces to be riveted, and strictly controlled during the production process.
The rivet pressing stroke shall be determined according to the length of riveted components and the thickness of workpieces to be riveted, ensuring that riveted components can be fully pressed into the prefabricated holes of workpieces to be riveted without being pressed too deeply or too shallowly. Generally, the control accuracy of the rivet pressing stroke shall be within ±0.1mm.
Rivet pressing speed also affects the quality of rivet pressing. Excessively high speed may prevent air between riveted components and workpieces to be riveted from being discharged in a timely manner, resulting in air holes or false riveting; excessively low speed will affect production efficiency. Usually, the rivet pressing speed shall be adjusted according to the material properties and the performance of the rivet pressing equipment, generally ranging from 10 to 50mm/s.
Before mass production, first article inspection shall be conducted to comprehensively inspect the appearance, dimensional accuracy, and connection strength of riveted components. Mass production can only be carried out after confirming that the requirements are met. First article inspection can promptly identify whether the process parameter settings are reasonable and whether there are problems with the molds, avoiding the occurrence of batch quality issues.
During the production process, regular in-process inspection shall be conducted to check the quality status of riveted components, including appearance quality and dimensional accuracy. At the same time, observe whether the operating status of the rivet pressing equipment and process parameters are stable, and promptly identify and handle problems arising during the production process. For example, if scratches are found on the surface of riveted components, check in a timely manner whether the mold surface is worn or has foreign objects.
Finished product inspection shall be conducted on the products after rivet pressing, mainly including appearance inspection, dimensional accuracy measurement, tensile test, and torque test, to ensure that the product quality meets standards and customer requirements. For non-conforming products, they shall be marked, isolated, and analyzed. The causes shall be identified and corresponding corrective measures shall be taken to prevent non-conforming products from flowing into the next process or to customers.
