Silicone gasket miscellaneous parts are widely used in automotive, electronics, medical and other industries, and their size accuracy directly determines the sealing performance and assembly adaptability. To achieve effective size control, it is necessary to implement systematic management throughout the production process, focusing on four core links.
1. Material Selection and Pre-control
The shrinkage rate of silicone material is the core factor affecting product size. It is recommended to select low-shrinkage silicone (shrinkage rate ≤0.8%) for production, and strictly control the batch consistency of materials to ensure that the shrinkage fluctuation between batches is within ±0.1%. For products with different hardness requirements, note that the shrinkage rate of soft silicone (30 Shore A) is 3%-4%, while that of hard silicone (60 Shore A) is only 1.2%-1.5%, and corresponding mold compensation adjustments should be made according to this difference.
2. Mold Design and Precision Control
Mold accuracy is the foundation of size control. The cavity processing accuracy should be matched with the product requirements: ultra-precision products (tolerance ±0.01-0.03mm) require cavity accuracy of ±0.005mm, while conventional products (tolerance ±0.05-0.1mm) can use cavities with ±0.02mm accuracy. At the same time, the shrinkage compensation should be accurately calculated according to the material shrinkage rate and product structure, and the mold cavity size should be appropriately enlarged to offset the size reduction caused by silicone vulcanization shrinkage. In addition, the mold positioning mechanism should adopt double positioning such as conical pins to ensure that the positioning deviation is ≤0.05mm.
3. Process Parameter Optimization
Stable molding process is the key to reducing size fluctuation. First, control the vulcanization parameters: adopt PID closed-loop temperature control to ensure that the mold temperature fluctuation is ±1℃, and the temperature difference between each area is within ±2℃; the injection pressure fluctuation should be ≤5%, and multi-stage injection can be used to avoid uneven filling caused by excessive speed deviation. Second, reasonably set the holding time and cooling time: the holding time is adjusted according to the product thickness, and the cooling time is controlled to ensure that the demolding temperature is ≤40℃, reducing post-shrinkage deformation. Finally, avoid demolding too early to prevent size rebound due to incomplete silicone shaping.
4. Detection and Post-processing Correction
Establish a full-process detection system: conduct full-size inspection of the first piece of each shift and each mold, use visual inspection systems for online automatic detection during mass production, and sample inspection with coordinate measuring machines (accuracy ±0.01mm) every hour to monitor size fluctuation in real time. For products with slight size deviation, low-temperature shaping treatment (60℃×2h, applying 0.5MPa pressure) can be used to correct the size and improve the qualification rate. At the same time, establish a shrinkage rate database, and dynamically adjust mold compensation and process parameters according to the actual shrinkage rate of each batch of products.
Through the above four-link control, the size tolerance of silicone gasket miscellaneous parts can be stably controlled within the required range, meeting the application needs of different industries from conventional industrial scenarios to high-end fields such as medical treatment and semiconductors.
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