During the resin wheel manufacturing process, optimizing the curing process is crucial for reducing internal stress defects. During the curing process, resin molecular chains form a three-dimensional network structure through cross-linking reactions. If the internal stress generated by volume shrinkage is not effectively released, it can lead to wheel deformation, cracking, or performance degradation. Therefore, coordinated optimization of multiple dimensions—temperature control, heating strategies, curing time, and auxiliary methods—is necessary to achieve stress balance and stable performance.
Temperature control is the primary parameter in the curing process. The resin curing reaction is highly sensitive to temperature. Excessively high temperatures accelerate the cross-linking reaction, leading to excessive shrinkage and concentrated internal stress. Excessively low temperatures result in an incomplete reaction, leaving uncured components, which can easily lead to delayed stresses during long-term use. For example, the curing of phenolic resin-bonded grinding wheels typically utilizes a staged temperature ramp: an initial low-temperature preheating phase (60-80°C) ensures uniform resin melting and avoids local overheating; an intermediate phase gradually raises the temperature to 110-120°C to promote a smooth crosslinking reaction; and the final temperature phase (160-190°C) is adjusted based on the required grinding wheel density. High-density grinding wheels require a higher final temperature to ensure complete cure, but the duration of the high-temperature phase must be strictly controlled to prevent overcure and increased brittleness.
Optimizing the heating rate is crucial for reducing thermal stress. Rapid heating creates temperature gradients between the resin surface and interior, leading to uneven shrinkage and, in turn, stress concentration. A slower heating rate (e.g., 0.25-0.5°C/minute) ensures uniform heat penetration, synchronizes the crosslinking of the resin molecular chains, and reduces localized shrinkage differences. For example, in the curing of epoxy resin flywheel rotors, extending the heating time to several hours can significantly reduce the interfacial stress between the carbon fiber and aluminum hub caused by differences in thermal expansion coefficients, thereby improving structural stability.
Controlling the curing time requires a balance between ensuring complete reaction and stress release. Undercure results in incomplete crosslinking of the resin, reducing strength; overcure can lead to internal stresses due to excessive molecular chain shrinkage or degradation. In practice, an appropriate curing cycle should be set based on the resin type, grinding wheel size, and process conditions. For example, a phenolic resin grinding wheel typically cures for 20–25 hours, during which time it needs to be held at an intermediate temperature (e.g., 80°C) to relieve internal stress buildup. High-density grinding wheels manufactured using a hot press process require an additional 8–12 hours of post-curing to ensure complete crosslinking.
Auxiliary methods can further optimize stress distribution. For example, applying vibration or pressure during the curing process can promote resin flow, reduce porosity, and thus mitigate localized stress concentrations caused by pores. Furthermore, a flexible transition layer design, such as an elastic buffer material between the metal insert and the resin wheel body, can absorb some shrinkage stress and prevent crack propagation. For large or complex resin wheels, prestressed mold technology can also be used to apply reverse tension to the mold before curing to offset shrinkage stress during curing and improve dimensional stability. Controlling the curing environment also affects stress levels. Excessive humidity can cause the resin to absorb moisture, affecting crosslink density; poor air flow can lead to localized overheating due to heat accumulation. Therefore, the curing oven should be equipped with a forced ventilation system to ensure temperature uniformity and maintain humidity within a reasonable range. For light-cured resin wheels, the light intensity and wavelength must also be optimized to ensure uniform resin curing and avoid internal stress variations caused by insufficient light penetration.
Post-curing is an effective means of eliminating residual stress. A secondary heating (usually below the primary curing temperature) followed by a holding time allows incompletely reacted resin to continue crosslinking, promoting molecular chain relaxation and stress release. For example, post-curing SLA resin wheels with high-power UV lamps for uniform irradiation can significantly improve mechanical properties and reduce the risk of deformation.
Optimizing the curing process in resin wheel manufacturing requires considering both reaction kinetics and stress release mechanisms. Precisely controlling temperature, heating rate, and curing time, combined with auxiliary measures and environmental control, can effectively reduce internal stress defects and improve the reliability and service life of the resin wheel. This process requires systematic debugging based on material properties and process conditions to achieve a balance between performance and cost.
