How to deal with the exhaust problem of liquid silicone mold?

In the field of mold manufacturing, liquid silicone rubber (LSR) is widely used in various industries such as medical, electronic, automotive, and daily consumer goods due to its excellent elasticity, temperature resistance, aging resistance, and biocompatibility. However, during the injection molding process of liquid silicone, exhaust issues often become a key factor affecting product quality and production efficiency. Effective exhaust not only ensures that the product is defect free, but also improves the service life and production stability of the mold.

1、 The root cause of exhaust problem in liquid silicone molds

During injection molding, liquid silicone is prone to forming bubbles or air pockets in the mold cavity due to factors such as the viscosity of the material itself, mold temperature, injection pressure, and speed. These bubbles mainly come from the following aspects:
1. Unreasonable mold design: Improper positioning, insufficient quantity, or small size of exhaust slots result in the inability to smoothly discharge gas.
2. Insufficient precision in mold processing: The precision of the mold parting surface, slider and other mating surfaces is not high, resulting in poor sealing and the entry of external air.
3. Improper setting of injection molding process parameters: Excessive injection speed, high pressure, or insufficient holding time may compress gas inside the rubber material.
4. Raw material issues: Water, volatile substances, or impurities in liquid silicone gel may not be completely removed, and gases may also be generated during the injection molding process.

2、 The impact of exhaust problems in liquid silicone molds

Poor exhaust can directly lead to the following quality issues with the product:
Surface defects, such as bubbles, shrinkage cavities, depressions, etc., seriously affect the appearance and sealing of the product.
Decreased dimensional accuracy: Due to internal gas expansion or contraction, the product dimensions are unstable.
Weakening of mechanical properties: Bubbles can reduce the strength and toughness of the product, affecting its usability.
Mold damage: Long term poor exhaust may cause local overheating and increased wear of the mold, shortening its service life.

3、 Strategy for solving the exhaust problem of liquid silicone molds

The exhaust problem of liquid silicone molds can be solved from the following aspects:
1. Optimize mold design
Reasonably set up exhaust slots: According to the product structure and mold layout, sufficient number and size of exhaust slots should be set up at appropriate positions to ensure smooth gas discharge.
Optimize channel design: Reasonably design the channel layout and size, reduce the flow resistance of the rubber material, and lower the risk of gas compression.
Improve mold processing accuracy: Ensure that the mold parting surface, slider and other mating surfaces meet the design requirements, and reduce the possibility of air infiltration.
2. Adjust the injection molding process parameters
Control injection speed: Reduce the injection speed appropriately to ensure smooth filling of the mold cavity with the rubber material and reduce gas generation.
Adjust injection pressure and holding time: Based on the material characteristics and mold structure, set the injection pressure and holding time reasonably to ensure that the rubber material is fully compacted and gas is discharged.
-Optimize mold temperature: Keeping the mold temperature within an appropriate range is beneficial for the flow of rubber and reduces gas generation.3. Strictly control the quality of raw materials
Strengthen raw material inspection: Ensure that liquid silicone has been fully dried before injection molding, removing moisture and volatile substances.
Select high-quality raw materials: Choose liquid silicone suppliers with stable quality to reduce exhaust problems caused by raw material issues.

4. Introduce advanced technology and equipment

Adopting vacuum injection molding technology: Vacuum treatment is applied to the mold before injection molding to effectively reduce air residue inside the mold.
Install online monitoring system: Real time monitoring of mold temperature and gas content during injection molding process, and timely adjustment of process parameters.
4、 Daily maintenance and upkeep
Regularly clean the exhaust duct: prevent blockage of the exhaust duct and keep it unobstructed.
Check the mating surface of the mold: Regularly inspect the wear of the mold parting surface, slider and other mating surfaces, and repair or replace them in a timely manner.
Keep the mold clean: Clean the residual rubber and impurities on the surface of the mold after each injection molding to prevent affecting the exhaust effect.