Liquid Silicone Injection Molding Process and Abnormal Handling?

2024-10-11

Contents

Liquid silicone injection molding is a high-precision and high-efficiency molding method. Silicone is injected into the mold through an injection molding machine and quickly solidified by high temperature and high pressure. The advantage of injection molding is that it can produce products with complex shapes and products of various colors.

Introduction to liquid silicone injection molding process

Liquid silicone injection molding uses liquid silicone as the main raw material. The two-component material (Part A and Part B) is mixed with a screw and injected into the mold for vulcanization molding. This process can produce high-quality products with the advantages of no waste and automation. Liquid silicone products are soft and widely used to simulate human organs, medical silicone chest pads, etc. In addition, liquid silicone has good thermal stability, cold resistance, and electrical insulation properties. No poisonous substances are produced when burned. Therefore, it has become an irreplaceable material in producing and designing health products, automobiles, baby products, medical products, diving products, kitchen utensils, and seals.

Advantages of liquid silicone injection molding:

High precision
High production efficiency
Low loss
Higher level of automation
Low contamination rate

Disadvantages of liquid silicone injection molding:

High requirements for equipment and molds
High cost of equipment, molds, and materials
Sensitive to humidity

Liquid Silicone Injection Molding Process Flow:

The metering device first pumps a 1:1 mixture of LSR A and B components, distributes it to a static or dynamic mixer, and then distributes it to the metering cylinder of the injection molding machine. Once the two ingredients are mixed, the material can be injected into the corresponding mold. The screw conveyor in the injection cylinder is responsible for injecting and metering the mixed material.

Note: The metering cylinder and agitator temperature do not exceed 40°C.

Classification	Causes	Countermeasures
Bubble Stains	Insufficient vulcanization	Extended vulcanization time
	The air is not completely evacuated.	Fully evacuate the air from the portable tank
	Air mixed in	Be careful to prevent air from entering during the injection
	Mold temperature is too high	Lower mold temperature and pay attention to mold temperature distribution
	Mixing spots	Adjust injection speed, check agitator
Raw Edges	Too much injection volume	Adjust injection speed and increase clamping force
	There is dust on the parting surface	Control the workshop environment and close the protective cover during molding
	Lower clamping force	Increase clamping pressure
	Injection pressure is high	Adjust injection pressure
	The holding time is too long	Select a suitable holding time
Expansion	Insufficient vulcanization	Extend the vulcanization time and increase the temperature
	Insufficient molding pressure	Increase pressure
	Generate bubbles	Fully remove the air from the portable tank
	Uneven vulcanization	Adjust the heating device
Poor gloss	Insufficient vulcanization	Extend the vulcanization time and increase the temperature
Poor gloss	Rough mold surface	Mold electroplating, replacement of release agent
Poor demoulding properties	Insufficient vulcanization	Extend the vulcanization time
	Poor mold surface	Improve mold
	Uneven surface temperature distribution	Check heating method
Nozzle leakage	Nozzle wear and tear	Check the nozzle lock

In addition to material selection, mold development, and setting optimal parameters in the liquid silicone injection molding process, regular equipment maintenance and mold maintenance are also crucial. The production unit strictly controls each process to avoid unnecessary abnormalities and waste.

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