Parting line
Determining the position of the parting line is one of the first few steps in designing a silicone rubber injection mold. The exhaust is mainly achieved through grooves located on the parting line, which must pass through the area where the injection molding material finally reaches. This helps to avoid internal bubbles and reduce strength loss at the bonding point.

Due to the low viscosity of LSR, the parting line must be precise to avoid overflow. Even so, parting lines can often be seen on shaped products. Demolding is influenced by the geometric dimensions of the product and the position of the parting surface. Designing the product with slight chamfers helps to ensure consistent fit with the desired other half of the mold cavity.

Exhaust
With the injection of LSR, the air trapped in the mold cavity is compressed when the mold is closed, and then discharged through the ventilation groove during the filling process. If the air cannot be completely discharged, it will be trapped in the adhesive material (which often causes some parts of the product to show white edges). The width of the ventilation groove is generally lmm-3mm, and the depth is 0.004mm-0.005mm.

Vacuuming inside the mold can create the best exhaust effect. This is achieved by designing a gasket on the parting line and quickly vacuuming all mold cavities using a vacuum pump. Once the vacuum reaches the rated level, the mold is completely closed and injection pressure begins.

Some injection molding equipment allows for operation under variable closing forces, which allows the processor to close the mold at low pressure until 90% -95% of the mold cavity is filled with LSR (making it easier for air to be discharged), and then switch to higher closing forces to prevent silicone rubber from expanding and causing overflow.

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