Liquid Injection Molded Silicone (LIM)
Liquid Injection Molded Silicone (LIM) Process Description:
The Liquid Injection Molding (LIM) process starts with a two part liquid silicone compound formula ( A & B parts) that are delivered at a fixed ratio, typically 1:1, from material drums or pails by a hydraulic or pneumatic metered pumping system to a static mixer. The static mixer blends the two components into a homogenous suspension; this mixing process activates the compounds platinum cure system. The liquid silicone material from the static mixer flows to the injection unit. The LSR material is then injected into the mold cavity through a runner and gate system where it is held in the mold under high pressure and elevated temperature until material is cured (rubber is vulcanized). The cycle time is established to reach an optimal level of cure. At the end of the cycle, the parts are removed or ejected from the cavities and the next cycle begins.
Advantages of Liquid Injection Molding (LIM):
- Shorter cure times compared to traditional compression molding
- High level of repeatability, good for tight tolerance / precision components
- Superior clarity, material can be pigmented in-line with material flow to produce colors
- Closed mold injection supports molding of complex geometries and over-molding
Disadvantages of Injection Molding vs. other rubber molding methods:
- Higher start-up / shutdown costs, better suited for high volume applications
- Runner systems can lead to increased gross material weights when cold runner systems or other low waste options are not utilized.
Liquid Injection Molding (LIM)Steps:
- Two part liquid silicone delivered from material drums to static mixer
- Static mixer blends the two components into a homogenous suspension
- Material is injected from injection unit through runner system & gates into cavities.
- Mold remains closed under pressure and temperature to reach optimal cure
- Parts are removed from the mold and the process is ready to begin again