Rubber mold is the simplest method in rapid mold. Generally, the RP prototype is re-molded with silicone, but the life is very short, only about 10-30 pieces! It has very good elasticity and replication performance. Silicon rubber replication molds do not need to consider draft angle, do not affect dimensional accuracy, have good segmentability, and can be directly cast as a whole without dividing upper and lower molds. Then cut along the predetermined parting line and take out the mother mold.
Room temperature vulcanized silicone rubber is divided into two types: addition molding and condensation:
The raw materials and formula are made of special mold silicone rubber. The product is sold in double packaging. 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 ratio of the AB component.
When the room temperature is 20-25 degrees, A: B = 100: 1.5. When the chamber 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, it decreases by 0.1-0.3 parts in group B. The specific method is to determine the total amount according to the volume of the mold, and then accurately weigh the A and B components according to the proportion, and place them in a vessel to stir evenly.
Molding: Pour the prepared material into the clean object to be copied. In order to save material, thinner molds can be made, which can also be applied in batches. Gauze or the like can be added to increase the pulling force of the mold. It can be cured into an elastomer in 2 hours at room temperature of 20 degrees, and it can be used after one day.
Matters needing attention in making silicone rubber molds:
- Component B is a catalyst, which is susceptible to moisture and hydrolysis, so the lid should be tightly closed after use.
- As soon as the groups A and B are mixed, the chemical reaction starts immediately. The viscosity gradually rises and cannot be stopped. In order to avoid waste, it should be used according to the dosage and used immediately after use.
- The mixing ratio of groups A and B is related to the speed of the chemical reaction and the performance of the mold. The more component B, the faster the response, the higher the strength and hardness of the product, but the toughness decreases. Therefore, weighing is required to be precise.
- Before preparation, the component A should be stirred up and down evenly, and then weighed.
- The pouring method is suitable for relief type, and the brushing method is suitable for making three-dimensional mold. Molds for casting reliefs should be made with a frame that is 4-6cm longer than the original length and width. The border should be flat and the inside should be smooth. Place the frame on a clean glass plate when pouring, and then place the original in the frame, leaving a gap of 2-3CM on each side
Solutions to bubbles during production:
- Improved design of flash grooves and exhaust systems
- Increase the pressure of the press
- Reduce the amount of release agent and spray evenly
- Materials control moisture
- Try adding some defoamer
- Use cold runner
- Use a vacuum machine to evacuate vacuum, and increase the exhaust operation on the mold.