How to solve the problem of high shrinkage rate in silicone mold making?
Both industrial grade mold silicone and food grade mold silicone are two-component liquid silicone, and during the molding process, shrinkage may occur to some extent; Industrial grade mold silicone generally refers to condensation type silicone, which produces low molecules during cross-linking reactions and has a relatively high shrinkage rate. High quality condensation type mold silicone has a shrinkage rate of ≤ 0.2%; Food grade mold silicone generally refers to addition molding silicone, which does not produce low molecules in cross-linking reactions and has a relatively low shrinkage rate. High quality addition molding silicone has a shrinkage rate of ≤ 0.1%.
The reason for the large shrinkage rate of silicone mold:
1. Any material has a certain degree of shrinkage, and silicone rubber has a relatively small shrinkage rate compared to many materials;
2. The mold storage method is incorrect;
3. The larger the product size, the more obvious the shrinkage;
4. Making large products without adding fiberglass cloth;
5. Mold makers often do not adjust the glue according to the mixing ratio of AB components provided by the manufacturer, but instead increase the proportion of curing agent based on their own experience;
6. The mold is not completely cured, and the hardness of the silicone is not stable. Rushing to demold or produce in advance can cause deformation and shrinkage of the silicone mold.
Solution to shrinkage of silicone mold:
1. It is necessary to enlarge the original mold by 2-3% proportionally to ensure that the size of the produced product is within the range;
2. When the mold is not in use, fill it with gypsum water for storage. When it is produced again, remove the gypsum and start production. This way, storing the silicone mold will not shrink;
3. Adjust the adhesive according to the mixing ratio of AB components provided by the manufacturer;
4. When making large product molds, fiberglass cloth should be added, preferably with 2-3 layers of fiberglass cloth or gauze, to prevent the mold from deforming or becoming larger;
5. The mold must be completely cured before demolding, and can only be put into production after being left for 24 hours;