Vacuum coating machine water ring vacuum pump selection vacuum coating coating construction application method and analysis of common problems

This paper describes the construction methods of vacuum coatings and the problems encountered in the application process and the corresponding solutions.

Because of its light weight and easy processing, plastic is widely used in various fields of the national economy. However, it is an insulator, non-conductive, and has poor mechanical properties, which limits its application range. A layer of metal film is vacuum-coated on the surface to obtain a series of properties such as wear resistance, electrical conductivity and decoration, which greatly expands the application range. Moreover, the process produces almost no pollution problems such as waste water and waste, and meets the requirements of national energy conservation and emission reduction policies. In the vacuum coating process, the coating plays an essential role in closing the substrate, bonding the plastic, and adhering to the coating layer and protecting the decoration. The application of vacuum coating coatings and coatings plays a crucial role in the quality of coating products. Therefore, the construction method will be described first.

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Construction method

There are many construction methods for coatings, and there are two common types of dip coating and air spraying.

Commonly used dip coating methods include manual dip coating, transmission dip coating, rotary dip coating, vacuum dip coating, dip coating - flow coating and centrifugal dip coating. Centrifugal dip coating is suitable for small parts, such as beads. The process is to put the workpiece into the basket, then immerse it in the tank, put it into the bucket immediately after immersion, remove excess paint through the high-speed rotary machine, and then blow it. dry. The large dip tank can be dried by passing through the filter port of the temperature control device and the ventilation device that removes the solvent vapor.

Air spray can be used to obtain a thick and uniform coating film with high construction efficiency. Generally, compressed air with a pressure of 0.2~0.4MPa is used, and the range is between 200mm and 300mm. After spraying, the coated workpiece is placed in a clean room for 10~25min and then dried in an oven.

In order to improve efficiency, electrostatic spraying can be used, which not only saves time and electricity, but also reduces pollution and reduces paint waste. It is generally used when spraying a top coat on a coating layer.

Drying of paint

The drying method can be classified into the following categories depending on the properties of the coating.

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1) Heat carrier drying: Commonly used heat carriers are air, water and oil, such as electric heating and steam heating.

2) Infrared heating: At present, hot air or steam convection is generally used, and direct drying is performed in an oven or a drying room. When using the latter to dry, be sure to pay attention to ventilation, so as not to be dissolved by the organic solvent in the vapor, so that it is difficult to dry, which is also a difficult problem that the builder often encounters.

The choice of water ring vacuum pump for vacuum coating equipment, we know that when the pump is working, you need to pay attention to the following two aspects:

1. As far as possible, it is required to operate in the high efficiency zone, that is, in the area of critical vacuum or critical exhaust pressure.

2. Avoid running near maximum vacuum or maximum exhaust pressure. Operating in this area is not only extremely inefficient, but also unstable in operation and prone to vibration and noise. For vacuum pumps with a high degree of vacuum, cavitation often occurs in this area, and the obvious sign of this phenomenon is noise and vibration in the pump. Cavitation can cause damage to parts such as the pump body and impeller, so that the pump cannot work.

According to the above principle, when the vacuum or gas pressure required by the pump is not high, it can be selected firstly in the single-stage pump. If the degree of vacuum or exhaust pressure of the vacuum coating machine is high, the single-stage pump is often unable to meet, or the pump is required to have a large volume under the condition of higher vacuum, that is, the performance curve is required to be flat at a higher vacuum. A two-stage pump is available. If the vacuum coating equipment requires a vacuum of -710mmHg or more, an optional water ring-atmosphere pump or water ring-Roots vacuum unit can be used as the vacuuming device.

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If it is only used as a vacuum pump, it is better to use a single-acting pump. Because the single-acting pump is simple in construction, easy to manufacture and maintain, and has good cavitation resistance under the high vacuum condition of the vacuum coating machine. If only a large volume compressor is used, it is more suitable to use a double acting pump. Because the double-acting pump has a large gas volume, small volume, light weight, and the radial force can be automatically balanced, the shaft is not prone to fatigue fracture, and the service life of the pump is long.

Selecting the vacuum pump according to the amount of gas required by the system After the pump type is initially selected, for the vacuum pump, the pump model is also selected according to the amount of gas required by the system.