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Rubber mold is one of the simplest methods in the 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. It can be copied with silicone rubber without considering draft angle, without affecting dimensional accuracy, with good segmentation, and can be directly poured as a whole without separating the upper and lower dies. Then cut along the predetermined parting line and take out the master mold!
Room temperature vulcanized silicone rubber is divided into two types: addition and condensation
The raw material and formula are special mold silicone rubber, which is sold in double packaging form. Component A is rubber material and component B is catalyst. The room temperature, the strength and hardness of the mould should be considered in the preparation to determine the weight proportion of AB component.
At room temperature of 20-25 ℃, a: B = 100:1.5. When the chamber is low (but not lower than 10 degrees), add 0.1-0.3 of component B appropriately. If the room temperature is too high, it will reduce 0.1-0.3 phr in group B. The specific method is to determine the total dosage according to the mold volume, then weigh the components a and B accurately according to the proportion, and put them in the vessel to mix evenly, that is to say.
Mold making: pour the prepared material into the clean object to be imitated. In order to save materials, the thin mold can also be painted in several times. In order to increase the pulling force of the mould, the gauze can be pasted. 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 catalyst, which is easy to be hydrolyzed by moisture, so the cover should be tightly closed after use.
2. As soon as group A and B are mixed, the chemical reaction will start; the viscosity will rise gradually and cannot be stopped. In order to avoid waste, it should be used according to the dosage and prepared at any time. After the 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 mould. The more component B, the faster the reaction, the higher the strength and hardness, but the lower the toughness. Therefore, weighing requires accuracy.
4. Before preparation, the A-component material shall be evenly stirred up and down, and then weighed.
5. The pouring method is suitable for relief and the brushing method is suitable for the manufacture of three-dimensional mould. For the mold of casting relief type, the frame with length and width greater than the original length and width of 4-6cm shall be made first. 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 bubble solutions in the production process:
Improving the design of flume and exhaust system
Increase the pressure of the press
Reduce the amount of release agent and spray evenly
Material control moisture
Try adding some defoamers
Use cold runner
By using vacuum machine to vacuumize, the exhaust operation can be increased on the mould.
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