Vacuum Metalising Machine for Christmas Balls
This vacuum metallizing coating machine designed to coat a glass or plastic Christmas ball with an extremely thin film of metal(usually high purity aluminum), to obtain a mirror-like silvering effect. After that, coloring paint is sprayed on the metal film, and various golden, red, blue and other shining Christmas balls can be obtained.
In a high vacuum chamber, the metal (aluminum wire or aluminum foil) is heated and evaporated, so that its atoms or molecules are splashed out and evenly attached to the inner surface of the rotating Christmas balls to form a firm metal thin film.
Other applications: The same technology is also widely used in other industries.
Such as:
Toy industry: toy parts. Automotive industry: interior parts (car logo, decorative strip).
Household items: cosmetic packaging bottles, tableware handles, lamp accessories, etc.
Electronic products: provide electromagnetic shielding layer for plastic parts.
Production Flow
- Pretreatment-Cleaning and Priming
Christmas balls (usually made of plastic or glass) first need to be thoroughly cleaned to remove oil and dust from the surface.
Then, a layer of primer is sprayed on the inner surface to be coated. This paint is critical because it provides a smooth, uniform attachment surface for the subsequent aluminum layer, which directly affects the final gloss and mirror effect. - Racking-fixing the Christmas balls
The primed and dried Christmas balls are densely fixed on the special rotating frame (planetary frame) of the machine with the opening downward. The rack will slowly revolve and rotate in the vacuum chamber to ensure that the inner surface of each ball is evenly covered by metal vapor. - Vacuuming pumping
Put the shelf with Christmas balls into the cavity of the vacuum coating machine, close and seal the cabin door.
Start the vacuum pump set (usually including mechanical pump, Roots pump, diffusion pump, etc.) to pump out the air in the cavity and make it reach a very high vacuum degree (for example, 1010 ³ to 1010 Pa).
Why do we need a high vacuum?
Avoid the oxidation reaction between the oxygen in the air and the evaporated aluminum, which will affect the metallic luster.
Reduce the obstruction of air molecules, so that aluminum atoms can fly in a straight line and adhere evenly to the surface of the sphere. - Premelting and metal(aluminum) evaporation
A heating device (usually a tungsten wire evaporation boat or an electron gun) is arranged at the bottom of the cavity.
Wrap the high-purity aluminum wire around the tungsten wire, or place the aluminum foil in the evaporation boat.
A large current is applied to heat the tungsten wire to a very high temperature (exceeding the vaporization point of aluminum, about 1200 ° C), and the aluminum wire quickly melts and evaporates into metal vapor, which diffuses upward in the whole cavity.
Aluminum vapor diffuses upward in the vacuum and encounters the inner wall of the Christmas ball, which is constantly rotating and at room temperature.
Aluminum vapor condenses instantly when it is cooled, forming a very thin (about tens of nanometers), uniform and bright metal aluminum film, which is firmly attached to the primer. - Pick up from vacuum metallizing chamber
Turn off the heating power, wait for the cavity to cool down, and then inject air into the cavity to make the air pressure return to normal (called "vacuum breaking"). \Open the hatch and take out the shelf. By this time, the inner walls of all the Christmas balls had turned into shiny silver mirrors.
A protective topcoat (usually colored clear) is applied over the aluminum film. This finish protects the fragile aluminum film from scratches and oxidation, while giving the Christmas ball a variety of colors (such as gold, red, etc.).