Rubber mold is one of the most simple methods in rapid mold. Generally, RP prototype is re molded with silica gel, but its service life is very short, only about 10-30 pieces! It has good elasticity and replication performance. 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 poured as a whole without dividing the upper and lower mold. Then cut along the predetermined parting line and take out the master mold!

RTV silicone rubber can be divided into addition type and condensation type
The raw material and formula are special mold silicone rubber. The product is sold in the form of double packaging. Component A is rubber and component B is catalyst. The room temperature, the strength and hardness of the mold should be taken into account in the preparation, so as to determine the weight proportion of AB component.
At room temperature of 20-25 ℃, a: B = 100:1.5. 0.1-0.3 parts of component B should be added when the temperature is low (but not lower than 10 degrees). The higher the room temperature, the less 0.1-0.3 phr in group B. The specific method is to determine the total amount according to the mold volume, and then weigh the components a and B in proportion accurately, put them in the vessel and stir them evenly.
Mold making: pour the prepared material into the clean object to be imitated. In order to save materials, the mold can be made thinner, which can also be painted in several times. In order to increase the tension of the mold, paste gauze and so on. It can be cured into elastomer in 2 hours at room temperature of 20 ℃, and can be used in one day.

Precautions for making silicone rubber mold:
1. Component B is a catalyst and easy to be hydrolyzed by moisture, so the cover should be tightly closed after use.
2. As soon as group A and group B are mixed, the chemical reaction will start immediately, and the viscosity will gradually rise, which cannot be stopped. In order to avoid waste, it should be prepared according to the dosage, and it should be used immediately without delay.
3. The mix proportion of group A and group B is related to the speed of chemical reaction and the performance of the mold. The more component B, the faster the reaction, the higher the strength and hardness of the product, but the toughness decreases. Therefore, accurate weighing is required.
4. Before preparation, component A should be stirred up and down evenly, and then weighed.
5. Pouring method is suitable for relief, brushing method is suitable for the production of three-dimensional mold. Casting relief mold should first make the length and width are greater than the original length and width of each 4-6cm frame. The border should be flat and the inside 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. Solutions:
Design of improved flash groove and exhaust system
Increase the pressure of the press
Reduce the amount of release agent and spray evenly
Material control moisture
Try adding some defoamer
Use cold runner
With the vacuum machine vacuum pumping, the mold can increase the exhaust operation.