During the liquid silicone rubber (LSR) injection molding process, quality issues such as incomplete curing, surface defects, and abnormal hardness frequently occur. The following analysis addresses typical problems and provides troubleshooting directions.

Issue 1: Incomplete Curing of Parts

Possible causes include: Mold temperature too low, curing time too short, system and pipeline contamination, mixing problems, non-1:1 mixing ratio, etc.

Troubleshooting directions: Check whether the mold temperature meets process requirements; appropriately extend curing time; clean the system and pipelines; inspect the condition of the screw and mixer; check whether pump pressure is normal; confirm whether components A and B are mixed at a 1:1 ratio.

Issue 2: Undercured Surface (Surface Not Dry)

Possible causes include: Air contamination, improper curing time control, mold release agent interference, surface contamination, etc.

Troubleshooting directions: Check the air lines and replace the oil filter; adjust curing time; replace the mold release agent; check the cleanliness of operators' gloves.

Issue 3: Incorrect Product Hardness

Possible causes include: Improper temperature and curing time, heating rod problems, abnormal sensor position, holding time too short, etc.

Troubleshooting directions: Increase temperature and measure actual mold temperature with a thermometer; check the working condition of heating rods; check sensors and their positions; extend holding time.

Issue 4: Bubbles in Products

Possible causes include: Insufficient mold vacuum, curing time too short, injection speed too slow, injection gate too small, etc.

Troubleshooting directions: Ensure adequate mold vacuum; extend curing time or increase temperature; increase injection speed; enlarge the injection gate size.

Issue 5: Short Shots or Sink Marks on Product Surface

Possible causes include: Insufficient material supply, temperature too high, injection speed too slow, viscosity too high, etc.

Troubleshooting directions: Increase feed pressure; appropriately lower mold temperature; increase injection pressure; enlarge injection gate and runner dimensions.

Process Key Points

The key process parameters for LSR injection molding include: mold temperature controlled within the range of 170–200°C; components A and B must be precisely mixed at a 1:1 ratio; use needle valve nozzles to prevent material leakage; the cold runner system must be maintained at a sufficiently low temperature to prevent premature curing of the material. Through standardized operation and timely troubleshooting, quality defects in injection molded parts can be effectively reduced, and production yield improved.

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