Vacuum casting is to use SLA laser rapid prototyping or CNC machining as the prototype, and then use silica gel to do the mold, and use PU material for casting in vacuum, and thus clone a copy as the same as the original prototype. Due to the fast speed and low cost, vacuum casting greatly reduces the product development costs, cycle and risk. And vacuum casting works almost the same way as steel mold but they are in different use and technology.
Silicone molding materials are: domestic and imported silicone, transparent silicone and special silicone.
Factors that cause the deformation of the vacuum casting prototypes
However, in the process of vacuum casting, prototype become deformed due to various reasons, which affects the accuracy of the prototype. Then what factors will lead to deformation of the vacuum casting prototype?
1. Mold silica gel is put into use before it is fully cured. Although the mold can generally be removed within a few hours after casting, but it takes at least a week for the it to be fully cured. If time permits, experienced master usually take out the prototype a month later.
2. The quality of the mold silica used is too poor, or the shrinkage is too high or there is too much filler (to reduce the cost of mold plastic). Shrinkage rate of high-grade silicone molds are within 0.1% and about 3% for the ordinary. Poor ones may go up to 10% or more.
3. Vacuum casting prototype need for high temperature in the injection, and due to the impact of thermal expansion and contraction, silicone liquid may be perfect at that time but may be much smaller than the actual size once it is cooled down and shrinkages.