Mold pallets are usually made of non-alloy tool steel. For mold pallets that need to withstand high temperatures of 170°C-210°C, they should be made of pre-tempered steel in consideration of impact resistance. For the LSR forming mold pallet with mold cavity, it should be made of B steel that has undergone nitriding or tempering heat treatment to ensure its high temperature resistance.
For high loading LSRs, such as oil-resistant LSRs, it is recommended to use a harder material for the mold, such as bright chrome-plated steel or powdered metal specially developed for this purpose. When designing molds for high wear materials, those parts that are subject to high friction should be designed to be replaceable so that the entire mold does not have to be replaced.
The inner surface of the cavity has a great influence on the finish of the product. The most obvious is that the shaped article will conform exactly to the cavity surface. LSR forming molds for transparent products should be made of polished steel. Finished Chin/Nickel steel is extremely abrasion resistant, while PTFE/Nickel makes demolding easier.
Generally speaking, it is advisable to use electric heating for the mold of LSR, which is usually heated by a belt heater, a cartridge heater or a heating plate. The key is to have an even distribution of the temperature field throughout the mold to promote uniform curing of the LSR. On large molds, it is a cost-effective heating method when the oil temperature is controlled for heating.
Covering the mold with a thermal insulation board is beneficial to reduce heat loss. Improper fit of any part of the hot mold may subject it to large temperature fluctuations between operations, or cause outgassing. If the surface temperature drops too low, the curing speed of the compound will slow down, which often makes the product unable to release the mold, causing quality problems. A certain distance should be maintained between the heater and the parting line to prevent the template from being warped and deformed, resulting in the formation of overflowing burrs on the finished product.
When designing LSR forming molds for cold runner systems, complete separation must be ensured between the hot and cold ends. It can be made from a special Chin alloy because it has a much lower thermal conductivity than other steels. For an integral mold heating system, the heat shield should be placed between the mold and the mold carrier to minimize heat loss.
Proper design and conception ensures LSR injection molding, where molds are important. The mold design principles are aimed at filling the mold cavity with compound, shortening curing time, high quality finished product, and high output, thus enabling silicone rubber processors to obtain good economic benefits.
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