Rubber mold is the simplest method in rapid mold. Generally, the RP prototype is remoulded with silica gel, but the life is very short, only about 10-30 pieces! It has good elasticity and replication performance. Using silicone rubber to replicate the mold does not need to consider the draft angle, which will not affect the dimensional accuracy. It has good segmentation and 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 is divided into two types: addition type and condensation type:


The raw material and formula use special-purpose mold silicone rubber, which is sold in double packs, component A is the rubber compound, and component B is the catalyst. The room temperature, the strength and hardness of the mold should be considered during the preparation, so as to determine the weight preparation ratio of AB components.


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 B component appropriately. If the room temperature is too high, reduce group B by 0.1-0.3 parts. The specific method is to determine the total dosage according to the mold volume, then weigh components A and B accurately in proportion, put them in a vessel and stir evenly, and it is ready.


Mold making: 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 stages. In order to increase the pulling force of the mould, 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 easy to be hydrolyzed by moisture, so the lid should be tightly closed after use.


2. Once the A and B groups are mixed, the chemical reaction will start immediately, and the viscosity will gradually increase, which cannot be stopped. In order to avoid waste, it should be prepared according to the amount used. It should be used immediately after preparation without delay.


3. The mixing ratio of groups 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 accordingly. Therefore, weighing requires precision.


4. Before preparation, component A should be stirred evenly up and down, and then weighed.


5. The pouring method is suitable for relief sculptures, and the brushing method is suitable for the production of three-dimensional molds. The mold for pouring reliefs should first make a frame whose length and width are 4-6 cm larger than the original length and width. The frame should be flat and the inner surface should be smooth. When pouring, place the frame on a clean glass plate, then place the original in the frame, leaving a gap of 2-3CM on each side


Solutions for bubbles in the production process:


    Improved flash slot and exhaust system design

    Increase the pressure of the press

    Reduce the amount of release agent and spray evenly

    Materials Control Moisture

    You can try adding some defoamer

    use cold runner

    Use a vacuum machine to vacuum the air, and the exhaust operation can be added on the mold.


About silicone rubber, please check the details:
https://www.siliconefoam.net/product-iota-f663a,b-liquid-silicone-rubber-foam-.html