Rubber mold is the simplest method in rapid tooling. Generally, RP prototype is duplicated 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 can be used without considering the draft angle, which will not affect the dimensional accuracy. It has good segmentation. It can be directly poured 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 can be divided into two types: addition type and condensation type:
The raw materials and formula adopt special mold silicone rubber, which is sold in double packaging. Component A is rubber, and component B is catalyst. The room temperature, strength and hardness of the mold shall be taken into account when preparing, so as to determine the weight preparation proportion of AB component.

At room temperature of 20-25 ℃, A: B=100:1.5. When the room is low (but not lower than 10 degrees), add 0.1-0.3 portions of component B appropriately. If the room temperature is too high, 0.1-0.3 portions of group B will be reduced. The specific method is to determine the total amount according to the mold volume, then accurately weigh components A and B in proportion, place them in a container and stir them evenly.

Mold making: pour the prepared materials into the clean object to be imitated. In order to save materials, the thinner die can also be painted in several times. The gauze can be pasted to increase the tension of the mold. It can be cured into elastomer in 2 hours at room temperature of 20 ℃, and can be used after one day.

Precautions for silicone rubber mold production:
1. Component B is a catalyst, which is susceptible to moisture hydrolysis, so the cover should be tightly covered after use.
2. Once group A and B are mixed, chemical reaction occurs; Start immediately, and the viscosity will gradually rise, which cannot be stopped. To avoid waste, it should be prepared as needed according to the dosage. After preparation, it should be used immediately without delay.
3. The mix proportion of group A and 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 shall be evenly mixed up and down, and then weighed.
5. Pouring method is suitable for embossing, while brushing method is suitable for making three-dimensional moulds. For the mold of casting relief type, the frame with the length and width of 4-6 cm greater than the original length and width shall be made first. The frame shall be flat and the inner surface shall be smooth. During pouring, place the frame on a clean glass plate, and then place the original in the frame, leaving a 2-3CM gap on each side.

Solution for bubbles during production:
Improve the design of 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
Vacuum pumping with a vacuum machine can increase the exhaust operation on the mold.