Metering and Feeding Systems in LSR Processing: What Affects Dosing Accuracy?

In liquid silicone rubber (LSR) injection molding, the metering and feeding system plays a decisive role in determining final product quality. Because LSR is a two-component platinum-cured material that requires precise 1:1 mixing, even small deviations in dosing accuracy can lead to defects such as incomplete curing, inconsistent hardness, or dimensional instability. Modern production systems rely on high-precision metering pumps, static mixing units, and temperature-controlled feed lines to ensure stable output across long production cycles.

How Metering Accuracy Directly Impacts LSR Quality

The accuracy of dosing in LSR systems is not only a mechanical issue but also a chemical balance problem. If component A and B are not mixed in a perfect ratio, cross-linking reactions may be incomplete or excessive. This results in either soft, under-cured parts or overly brittle structures. Research in silicone processing shows that pressure stability, pump wear conditions, and material viscosity variations all influence long-term dosing consistency during continuous injection molding cycles.

Key Factors That Influence Feeding System Stability

Pump Precision and Wear Behavior

LSR metering systems typically rely on gear pumps or piston pumps. Over time, mechanical wear slightly changes volumetric output, which gradually shifts mixing ratios. High-end systems therefore integrate real-time calibration mechanisms to maintain stability during mass production.

Temperature Control in Feed Lines

ALSR viscosity is highly sensitive to temperature changes. If the material in feed lines becomes too warm, pre-curing may begin inside the system, leading to blockage or inconsistent flow resistance. Conversely, overly cold material increases viscosity and affects metering pressure accuracy.

Material Viscosity Variation Between Batches

Even within the same formulation, slight differences in filler dispersion or molecular weight distribution can affect flow behavior. This is why stable raw material sourcing is essential for maintaining long-term dosing consistency.

Industrial Optimization Strategies for Stable Dosing

Advanced LSR production systems integrate closed-loop pressure feedback and automated ratio correction algorithms. These systems continuously adjust pump displacement based on flow resistance and injection feedback, ensuring that even under fluctuating environmental conditions, the dosing ratio remains within strict tolerance limits.

FAQs

Q1: Why is LSR metering more sensitive than plastic injection molding?

A:Because LSR relies on chemical curing rather than cooling solidification, any ratio imbalance directly affects cross-linking reactions.

Q2: What is the typical mixing ratio for LSR?

A:Most systems use a 1:1 A/B component ratio, but accuracy tolerance is extremely tight, often within ±1%.

Q3: Can manual feeding systems be used?

A:Only for prototyping. Industrial production requires automated metering systems for consistency.