A vacuum chamber and a pressure pot are commonly used equipment in mold-making and casting processes. They both serve the purpose of removing air bubbles from the project, ensuring a smooth and bubble-free surface on the final product. Understanding the differences between them can help you integrate or improve bubble elimination techniques in mold-making and casting processes.
1. What is a Vacuum Chamber?
The working principle of a vacuum chamber is to expand the air trapped in bubbles, causing them to rise to the top and burst. Therefore, it is recommended that the mixing container should be at least 3-5 times the volume of the material to prevent overflow. By repeatedly opening and closing the air inlet valve dozens of times, the bubbles will gradually decrease until they disappear. However, some materials seem to continue foaming indefinitely until the vacuum pump is turned off.
vacuum chamber
The viscosity of liquid silicone determines the speed of vacuum degassing, with lower viscosity materials degassing more quickly. To maximize the removal of bubbles, it is advisable to choose a vacuum pump that can achieve a vacuum pressure of 29.6 inches of mercury.
How to Use a Vacuum Chamber
2. What is a Pressure Pot?
The principle of a pressure pot is to compress air bubbles to the point where they are not visible to the naked eye. Technically, a pressure pot does not eliminate bubbles but rather compresses them to an invisible state. Typically, a pressure range of 60-80 psi can significantly reduce bubbles that are visible to the naked eye. To ensure effectiveness, it is recommended to open the pot only after the liquid material has completely cured. Otherwise, if the pressure is released prematurely, bubbles may expand. Additionally, being under pressure ensures that all intricate details of the mold are filled with the liquid material.
pressure pot
How to Use a Pressure Pot
3. When to Use a Pressure Pot or a Vacuum Chamber
Both devices have their own advantages and disadvantages, and there is no definitive answer as to which one is better. It depends on the specific details of your particular project and which method is more suitable.
In simple terms, a vacuum chamber is used to remove bubbles by sucking out the air, making it more suitable for degassing liquid silicone before pouring. Most resins do not have a viscosity that requires vacuum, especially polyurethane resins which have a very short working time, about 100 seconds. Creating a vacuum in a chamber takes a longer time. In these cases, a pressure cooker is the preferred equipment because it can quickly pressurize, faster than using a vacuum pump to create a vacuum.
In summary, a vacuum chamber is primarily used for eliminating bubbles in rigid materials, while both a vacuum chamber and a pressure pot can be used for degassing rubber materials, with a particular suitability for organic silicone and polyurethane rubbers. In some cases, a combination of both methods might be used. For example, you could vacuum degas your material to remove the bulk of the air bubbles and then use a pressure pot to compress any remaining tiny bubbles.
Please note that whichever device you choose, be sure to carefully read the operating instructions and understand all safety procedures. By taking the time to understand each method and the materials you are working with, you'll achieve the best results for your project.
4. Summary
In summary, a vacuum chamber uses a vacuum pump to remove air from liquid materials, while a pressure pot uses a compressor to increase pressure, reducing bubbles in the material.
Vacuum Chamber = Remove Bubbles
Pressure Pot = Conceal Bubbles
