Troubleshooting Liquid Silicone Rubber Injection Molding Issues

[christinescoms]

Hi everyone,

I’m working with liquid silicone rubber (LSR) injection molding and have run into a few challenges.

I’m having trouble with achieving consistent part quality.

I’m noticing some issues with air bubbles and incomplete fills.

Can anyone share tips on how to optimize mold design or adjust process parameters to address these problems?

Any advice on selecting the right LSR material for better results would be greatly appreciated.

 

[ZipZapOuch]

Are you applying vacuum to your uncured pot after mixing (but before viscosity builds during curing? There is a lot of dissolved or entrained air in these resins. The heat generated during curing causes
1) air to come out of solution (hot liquids don't dissolve as much gas as cold liquids can hold
2) bubbles get bigger with temperature

It's very difficult to cast a perfectly clear part without degassing with vacuum.

 

[aliarifat794]

Ensure that the mold has adequate ventilation to allow air to escape. This can help in reducing air bubbles. Vents should be placed strategically to ensure they do not compromise the integrity of the final part.

 

[ZipZapOuch]

Ensure that the mold has adequate ventilation to allow air to escape. This can help in reducing air bubbles. Vents should be placed strategically to ensure they do not compromise the integrity of the final part.

LSR is cast (poured) into a mold and the top is left open to the atmosphere. I'm not sure how "venting" can be handled in a liquid system without plugging the vent holes. Also, since the issue is haze, and the viscosity builds and traps the bubbles to create the haze, I'm not sure how vent holes will help.

Please show or elaborate on what you are talking about.