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Silicone rubber mold making method and precautions

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Rubber mold is one of the simplest methods in the rapid mold. Generally, the RP prototype is re-molded with silicone, but the lifespan is very short, only about 10-30 pieces! It has good elasticity and replication performance, and the silicone rubber replication mold does not need to consider the draft angle, does not affect the dimensional accuracy, has good segmentation, and can be directly cast as a whole without dividing the upper and lower molds. Then cut along the predetermined parting line and take out the master mold!

Room temperature vulcanized silicone rubber is divided into two types: addition type and condensation type:

The raw material and formula are made of special mold silicone rubber, which is sold in two-packs. Component A is the rubber compound, and component B is the catalyst. When formulating, the room temperature, the strength and hardness of the mold should be considered to determine the weight preparation ratio of the AB component. When the room temperature is 20-25 degrees, A:B=100:1.5. When the room is low (but not lower than 10 degrees), add 0.1-0.3 parts of component B appropriately. If the room temperature is too high, group B will be reduced by 0.1-0.3 copies. The specific method is to determine the total amount according to the volume of the mold, and then weigh the components A and B accurately in proportion, and place them in a vessel to stir evenly, and that’s it.

Molding: Pour the prepared materials onto the clean object to be imitated. In order to save material, a thinner mold can be made, and it can also be painted in batches. In order to increase the tension of the mold, gauze and the like can be pasted. It can be cured into an elastomer in 2 hours at room temperature of 20 degrees, and can be used after one day.

Precautions for making silicone rubber molds:

1. Component B is a catalyst, which is easily hydrolyzed by moisture, so the lid should be tightly closed after use.
2. Once the A and B groups are mixed, the chemical reaction starts immediately, and the viscosity gradually rises and cannot be stopped. In order to avoid waste, it should be prepared according to the dosage, and it should be used immediately after preparation without delay.
3. The mixing ratio of group A and group B is related to the speed of chemical reaction and the performance of mold. The more component B, the faster the reaction, the higher the strength and hardness of the product, but the lower the toughness. Therefore, weighing requires precision.
4. Before preparation, component A should be stirred up and down evenly, and then weighed.
5. The pouring method is suitable for relief, and the brushing method is suitable for the production of three-dimensional molds. The mould for pouring relief should first make a frame whose length and width are larger than the original length and width of 4-6CM. The border should be flat and the inner surface should be smooth. When pouring, place the frame on a clean glass plate, and then place the original in the frame, leaving a gap of 2-3CM on each side

There are bubbles in the production process solution:

Improve the design of flash groove and exhaust system;
increase the pressure of the press;
Reduce the amount of release agent and spray it evenly;
Material controls moisture;
You can try adding some defoamers;
Use cold runners;
Evacuate with a vacuum machine, and the exhaust operation can be added to the mold.

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