Causes of bubbles

1 vulcanization temperature too low

Vulcanization temperature is an important parameter during silicone rubber molding. Generally, silicone products are set at 160 ~ 200 ℃, but sometimes the mold does not enter the machine for heating for a long time due to too long operation time outside the mold or other reasons, resulting in low temperature of silicone molding mold, which will cause bubbles in the product after molding. For this, we need to raise the forming temperature, or warm the empty mold for a period of time before operation to solve the problem.

2. The vulcanization temperature is too high

Low vulcanization temperature will cause silica gel forming bubbles. In many cases, too high molding temperature will also cause silica gel forming bubbles. Why? When the molding temperature is too high, the silica gel raw material on the surface has begun to form in the process of clamping and pressurization. At this time, the air has been trapped in it and it is difficult to discharge, so it will cause forming bubbles. For this reason, just reduce the forming temperature appropriately.

3. Too short vulcanization time

Like vulcanization temperature, vulcanization time is also one of the important parameters of silica gel molding. The length of vulcanization time determines whether silica gel can be completely vulcanized.

4 mold purchase

The unreasonable structure of the mold and the unreasonable design of the silica gel forming mold will also cause bubbles in silica gel forming.

The design of exhaust structure is unreasonable. The exhaust position should be designed at the end of product molding. If necessary, vacuum pumping in the mold should be designed.

5 mold cleaning

The mold is not cleaned when cleaning. Pay attention to the method when cleaning the mold. Try to scrub gently with soft fabric to avoid mold deformation.

6. The design of glue injection port is unreasonable

For some large liquid silica gel products, in order to improve the rubber filling, multiple glue injection ports are often designed. It is recommended to design only one glue injection port as far as possible. Although the liquid silica gel raw material looks very viscous, it actually has good fluidity. Generally, there is no need to worry about filling. If multiple glue injection ports must be designed, the position of the glue injection port must be balanced and symmetrical, and the exhaust port shall be designed at the corresponding position.

7 exhaust problem of feeding system

LSR feeding system: when loading or replacing new materials, if there is air in the pump body, exhaust the pump body. The way to judge whether there is air in the pump body is to open the exhaust ball valve of the pump body, press the glue pump up or down to see whether there are bubbles or sounds in the glue from the exhaust ball valve of the pump body. If there is, it means there is air.

The exhaust system is designed for Kawasaki silica gel feeding system, and the specific operation steps are as follows:

1. Unplug the quick plug

2. Open the stripping balloon valve

3. Lower pressure plate

The air will be discharged from the stripping balloon valve. When the liquid silica gel without air enters the transparent hose, it indicates that the air has been exhausted, and close the stripping balloon blowing valve.

Quantitative cylinder exhaust:

1. Switch to the automatic state, and the rubber will automatically enter the quantitative cylinder. The system stops automatically when the quantitative cylinder is full.

2. Open the exhaust ball valve of quantitative cylinder

3. Switch to the manual state, turn it to the quantitative cylinder for operation for 1 minute, and then turn it to the quantitative cylinder for operation for 1 minute, and the silicone oil and air will be discharged. Repeat until the AB glue pressure is consistent.

4. After the rubber without silicone oil and air flows out, close the exhaust ball valve.