How to Prevent Air Traps and Short Shots in Injection Molding?

Air traps and short shots are the two biggest defects in silicone products manufacturing process. They raise scrap rates and waste money.At Better Silicone, 

we fix these problems using vacuum degassing, precision mold venting, injection speed control, and accurate shot sizing.We also use chrome electroplating to

 improve mold surface quality and part release. For hard-to-vent products, our open liquid injection molding method removes bottom-surface bubbles that

 normal closed molds cannot solve.We offer two production platforms — LSR injection molding for high-precision zero-waste parts, and  open liquid injection

molding  for high-cavity-count tooling at lower mold cost. Both methods use professional LSR injection molding troubleshooting to keep silicone part

 quality consistent.

Why these defects happened ?

Air bubbles happen when air gets trapped inside the mold. The silicone cannot push the air out. So the finished part has voids or holes inside.Short shots happen

 when the mold is not fully filled. The silicone stops flowing before it reaches every corner. The part comes out incomplete.Both defects increase scrap rates.

 They also waste raw material and production time. Our team finds the exact cause first. Then we fix it the right way.

How we fix air traps in LSR injection molding? 

1. Vacuum Degassing

We use a vacuum pump before injection. It removes all the air from the mold cavity. No air in the mold means no air bubbles in the product. This is the 

most effective method for LSR injection molding.

2. Mold Venting Design

We add small vents to the mold. These vents let air escape during injection. We put the vents in the right places — where air usually gets stuck. Good 

venting design can cut short shot rates by 60% -80%.

3. Injection Speed Control

We adjust the injection speed carefully. Too fast and air gets folded into the silicone. Too slow and the silicone starts to cure too early. We find the right speed for 

each product. This helps the silicone flow smoothly and fill the mold evenly.

4. Multiple Injection Gates

Some silicone parts are large. One injection gate is not enough. The silicone travels too far and traps air along the way. We add more gates to shorten the flow 

path. This gives a more even fill and fewer air traps.

How we fix short shots in silicone rubber molding

1.Accurate Shot Size

We use sensors to measure the silicone volume every shot. The machine gives the exact amount needed each time. No guessing. No insufficient filling. This keeps silicone part 

quality consistent.

2.Mold Temperature Control

Temperature affects how fast silicone cures. If one area is too hot, the silicone hardens too early. Other areas do not fill properly. We control the temperature in different 

zones of the mold. This gives a smooth and complete fill every time.

3.Regular Gate Cleaning

Blocked gates cause short shots. We clean all gates and runners regularly. We do not wait for a defect to appear. Prevention is better than rework.

4. Mold Surface Electroplating

We treat the mold surface with chrome electroplating. This makes the mold very smooth. A smooth mold surface gives the silicone part a clean finish.

 It also helps the part release from the mold easily. Good mold release means less damage and fewer defects. It also helps the silicone flow better into small corners.

5.Our Open Liquid Injection Molding Method

This is our own special process. We use an open mold design with liquid injection technology. The open mold lets gas escape from the bottom of the part. Normal

 closed molds cannot do this. Gas at the bottom usually gets trapped. With our method, yield rates go up. Bottom-surface bubbles become much less common. 

This process is a type of advanced HCR silicone molding. It works well for many product types.

LSR Injection Molding vs Open Liquid Injection Molding

Which method is better? It depends on your product and your budget. Here is a simple comparison.

Factor	LSR Injection Molding	Open Liquid Injection Molding
Precision	Very high	Good
Material Waste	Almost zero-no sprue or runner waste	Some waste from runners and flash
Runner System	Cold runner with needle valves	Standard runner system
Automation	High-runs with little supervision	Medium-needs more manual steps
Cavities per Mold	Fewer cavities	More cavities-more available space
Mold Cost	Higher- need better steel	Normal-more affordable tooling
Best For	Precision parts, high volume, zero waste	High cavity count, lower tooling budget

LSR Injection Molding

LSR injection molding is great for precision silicone parts. It has almost no waste because there is no sprue. The cold runner system keeps the silicone in liquid

status until the last moment. The needle valve controls the shot precisely. The mold cost is higher. But the quality and automation level are top class.

Open Liquid Injection Molding

The cost for open liquid injection molding is less. The mold can fit more cavities. The platen space is used more efficiently. This is a good choice when mold cost 

matters more than ultra-high precision.Both manufacturing methods are widely used for skilled silicone supplier. LSR injection molding for key precision parts. 

Open liquid injection molding for high-volume standard parts.

Why Choose Better Silicone?

Air bubbles and short shots are not accidents. They happen for specific reasons. We find those reasons and fix them. We have the right machines, the right mold design, 

and years of experience in silicone injection molding troubleshooting. If your silicone parts have quality problems, contact us. We are happy to review your product and

suggest the best solution.

Contact us Today : info@lsr-modling  86 15959286708