Brief introduction: Matters needing attention in processing rubber oil seal products
Rubber oil seal is a precision rubber-plastic component used to seal grease and block impurities, which is widely used in the fields of motors, bearings, hydraulic systems, etc. In the processing process, four core links, such as material selection, mold precision, vulcanization process and post-treatment, should be strictly controlled to ensure the sealing performance and service life of products. The specific precautions are as follows:
Accurate material selection, matching working conditions, different working conditions have significant differences on the performance requirements of oil seal materials, which need to be selected as needed: NBR is suitable for diesel oil, engine oil and other media, and it is temperature-resistant at-40℃~120℃, which is suitable for general machinery; Fluorocarbon (FKM) is resistant to strong corrosive medium and high temperature (-20℃~250℃), and is used in chemical industry and automobile engines. Silica gel is resistant to high and low temperature (-60℃~200℃), non-toxic and suitable for food machinery and medical equipment. When selecting materials, the material compliance should be checked at the same time, so as to meet the environmental protection standards such as RoHS and REACH, and avoid the seal failure caused by the use of inferior reclaimed rubber.
Strictly control the mold accuracy and ensure the dimensional consistency. The mold is the key to determine the dimensional accuracy of the oil seal. The tolerance of the mold cavity should be controlled within ±0.01mm, and the parting surface should be flat and smooth to prevent the oil seal from flash and lack of glue. The mould should be cleaned and maintained regularly, and the worn parts should be repaired in time to avoid the appearance and sealing performance of the product being affected by corrosion or glue accumulation in the cavity. In addition, the exhaust groove of the mold should be designed reasonably to exhaust the gas generated in the vulcanization process to prevent bubbles and shrinkage cavities in the oil seal.
Optimizing the vulcanization process and controlling the core parameters are the core processes of rubber oil seal molding, and the three elements of temperature, pressure and time need to be strictly controlled. Vulcanization temperature needs to be adjusted according to the rubber type. For example, the vulcanization temperature of NBR is usually 150℃~160℃ and FKM is 170℃~180℃. If the temperature is too high, it will easily lead to rubber aging and hardness increase. If the temperature is too low, the vulcanization will be incomplete and the elasticity will be insufficient. The curing pressure should be uniform and stable, generally 10~15MPa, to ensure that the rubber compound can fully fill the cavity; Vulcanization time should be accurately controlled and adjusted according to product thickness to avoid under-sulfur or over-sulfur.
Standardize the post-treatment process, improve the product quality. The vulcanized oil seal needs trimming, using freezing trimming or mechanical trimming to remove flash burr, so as to ensure the smooth lip without notch, otherwise it will directly affect the sealing effect. After trimming, it is necessary to clean the surface to remove oil stains and impurities, and then carry out size detection and performance test, including hardness, tensile strength, oil resistance and other indicators. Finally, it should be stored in a dry environment at normal temperature to avoid direct sunlight, high temperature and high humidity and prevent rubber from aging and deformation.
Strengthen process control to avoid quality hazards. It is necessary to keep the production environment clean during the whole process of processing to prevent dust and metal chips from mixing into the rubber compound; When mixing rubber compound, the proportion of compounding ingredients should be strictly controlled to ensure uniform dispersion; Semi-finished rubber compounds should be stored in batches, and the identification management should be done well to avoid mixing. At the same time, each batch of products needs to be tested, a quality traceability system should be established, and abnormal problems in the processing process should be investigated in time.
