When customizing silicone rubber products, many customers hope that the silicone products can reach their desired size. In the actual production process, there will be a small change in size between the customer's customized requirements and the produced product. This is what we call tolerance. There are many factors that affect the tolerance range and accuracy. Most people think that it is difficult to control the accuracy of a smaller size, and it is relatively easy to control a large size. In fact, it is more difficult to control the accuracy of products with too large dimensions. Next, let everyone understand how much the accuracy limit of silicone products can be achieved!
The thickest can be 15-20mm, if it is a sphere, the diameter can be 30mm. The thickness is generally recommended to be no greater than 3mm. When it is greater than 3mm, it will take more curing time and increase costs. The thinnest can be up to 0.2mm in theory, but in the design, the thinnest is generally 0.3mm, and 0.4mm is recommended.
In terms of thickness difference, it is recommended not to exceed 3 times the thinnest part and the thickest part. Such problems mainly depend on the temperature and pressure requirements of the material during vulcanization.
The shrinkage rate of silicone material is related to the hardness of the material. The secondary materials provided by the manufacturer are mostly between 1.022 and 1.042. For the material of 40 to 50 degrees, the shrinkage rate is generally 1.03. Compared with plastic, silicone products will not produce similar obvious surface defects due to shrinkage.
Since most silicone products have multiple cavities in one mold, there are many cavities compared to plastic products. Therefore, the size control is not as convenient as plastic products. The general accuracy is plus or minus 0.1mm, and the precision products are plus or minus 0.05mm. When the fit is used for the fit between the hole of the plastic part and the button, the minimum gap is 0.1mm on one side, and the recommended value is 0.2mm on one side.
For rubber sleeve parts, it is generally sufficient to provide the original drawing to the mold factory according to the appearance drawing of the product, and the explanation of the matching problems is left to the mold factory's own decision. Under normal circumstances, depending on the size of the product, the fit between the rubber sleeve and the product is generally a negative deviation of 0.2mm~0.5mm smaller on one side.