demoulding
The vulcanized liquid silicone rubber is easy to adhere to the surface of the metal, and the flexibility of the product will make it difficult to demould. The high-temperature tear strength of LSR can make it demould under normal conditions, and even larger products will not be damaged. The most common demolding techniques include stripper plate demolding, stripper pin demoulding and pneumatic demoulding. Other common technologies are roller scraping, stripping of the export plate and automatic mold control.
When using a demoulding system, it must be kept within a high precision range. If the gap between the push pin and the guide pin sleeve is too large, or the gap becomes larger due to long-term wear of the parts, it may cause glue overflow. Inverted cone or mushroom shaped jack pins work well because they allow higher contact pressures to be used for improved sealing.


mold material
Mold pallets are usually made of non-alloy tool steel (no.1.1730, DIN code C45W). For mold pallets that need to withstand high temperatures of 170°C-210°C, considering impact resistance, pre-tempered steel (no. 1.2312, DIN code 40 CrMn-M oS 8 6) Manufactured. For the mold supporting plate with mold cavity, it should be made of nitriding or tempering heat-treated steel to ensure its high temperature resistance.
For LSR with high filling content, such as oil-resistant LSR, it is recommended to use materials with higher hardness to make molds, such as bright chrome-plated steel or powder metal specially developed for this purpose (no.1.2379, DIN code X 155 CrVMo121). When designing molds for high-abrasion materials, those parts that are subject to high friction should be designed to be replaceable, so that the entire mold does not need to be replaced. The inner surface of the mold cavity has a great influence on the finish of the product. The most obvious is that the shaped product will conform exactly to the surface of the mold cavity. Molds for transparent products shall be made of polished steel. Surface-treated Chin/Nickel steel is extremely wear-resistant, while PTFE/Nickel makes mold release easier.


temperature control
Generally speaking, it is advisable to use electric heating for the molding of LSR, usually using a band electric heater, a cartridge heater or a heating plate for heating. The key is to make the temperature field evenly distributed throughout the mold to promote uniform curing of LSR. On large molds, it is a cost-effective heating method when pushing the oil temperature to control the heating.
Covering the mold with a thermal insulation board is beneficial to reduce heat loss. Inappropriateness of any part of the hot mold may cause it to suffer from large temperature fluctuations between operating procedures, or cause outgassing. If the surface temperature drops too low, the curing rate of the rubber compound will slow down, which often makes the product unable to be released from the mold, causing quality problems. A certain distance should be kept between the heater and the parting line to prevent the template from warping and deforming, forming overflowing glue and burrs on the finished product.
If designing a mold with a cold runner system, the hot end and the cold end must be completely separated. Special Chin alloys can be used because of their 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 support to minimize heat loss.
Proper design and conception can ensure LSR injection molding, where tooling is very important. The above-mentioned mold design principles are aimed at filling the mold cavity with rubber material, shortening the curing time, high-quality finished products and high output, so that silicone rubber processors can obtain good economic benefits.


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