To evacuate the pvd coating machine, a mechanical pump must be used. The mechanical pump is also called a backing pump. The mechanical pump is the most widely used low vacuum pump. It uses oil to maintain the sealing effect and relies on mechanical methods to continuously change the internal pressure of the pump. The volume of the suction cavity causes the volume of the gas in the pumped container to continuously expand to obtain a vacuum. There are many types of mechanical pumps, the four commonly used types are slide valve type, piston reciprocating type, fixed vane type and rotary vane type.

Mechanical pumps are often used to extract dry air, but they cannot extract gases with high oxygen content, explosive and corrosive gases. Mechanical pumps are generally used to extract permanent gases, but they are not good for water vapor. effect, so it cannot extract moisture. The main components in the rotary vane pump are the stator, rotor, springs, etc. The rotor is inside the stator but has a different spindle from the stator, like two inscribed circles. There are two springs in the rotor slot, and a spring is installed in the middle of the two springs. Ensure that the shrapnel is tightly attached to the inner wall of the stator.
Its two shrapnels alternately play two roles. On the one hand, it sucks in gas from the air inlet, and on the other hand, it compresses the sucked gas and discharges the gas out of the pump. For each revolution of the rotor, the pump completes two suctions and two discharges. When the pump continuously rotates clockwise, the rotary vane pump continuously inhales gas through the air inlet and continuously discharges it from the exhaust port to achieve the purpose of pumping air from the container. In order to improve the ultimate vacuum degree of the pump, the stator of the pump is immersed in oil. In this way, enough oil is always maintained in the gaps and harmful spaces everywhere to fill the gaps. Therefore, the oil plays a lubricating role on the one hand and also plays a role in lubrication on the other hand. On the one hand, it also plays the role of sealing and blocking gaps and harmful spaces, preventing gas molecules from flowing back through various channels to spaces with low pressure.
The mechanical pump starts working from the atmosphere. Its main parameters include ultimate vacuum and pumping rate. This is an important basis for the design and selection of the mechanical pump. The single-stage pump can pump the container from the atmosphere to the ultimate vacuum of 1.0*10-1PA, and the double-stage mechanical pump can pump the container from the atmosphere to 6.7*10-2PA, or even higher.
The pumping rate refers to the volume of gas that can be discharged per unit time when the rotary vane pump operates at the rated speed. It can be calculated using the following formula:
Sth=2nVs=2nfsL
fs represents the cross-sectional area of the cavity at the end of suction, L represents the length of the cavity, the coefficient indicates that there are two exhaust processes per rotation of the rotor, Vs represents that when the rotor is in the horizontal position, the suction ends, and the volume in the cavity is the largest at this time , the rotation speed is n.
The exhaust effect of the mechanical pump is also related to the speed of the motor and the tightness of the belt. When the belt of the motor is relatively loose and the motor speed is very slow, the exhaust effect of the mechanical pump will also become worse, so regular maintenance is required. Inspection, the sealing effect of mechanical pump oil also needs to be checked frequently. If there is too little oil, the sealing effect cannot be achieved, and air will leak in the pump. Too much oil will block the suction hole, making it impossible to inhale and exhaust. Generally, in The oil level is 0.5 cm below the line.
Roots pump: It is a mechanical pump with a pair of double-leaf or multi-leaf rotors that rotate synchronously at high speed. Since its working principle is the same as that of Roots blower, it can also be called Roots vacuum pump. This pump is in 100-1 There is a large pumping speed in the Pa pressure range, which makes up for the shortcomings of the mechanical pump's insufficient exhaust capacity in this range. This pump cannot start from the atmosphere, nor can it directly discharge the atmosphere. Its function is only to increase the air intake. The pressure difference between the inlet and exhaust port needs a mechanical pump to complete the rest. Therefore, it must be equipped with a mechanical pump as a backing pump.

When using the mechanical pump of the pvd coating machine, you must pay attention to the following issues:
1. The mechanical pump should be installed in a clean and dry place.
2. The pump itself must be kept clean and dry. The oil in the pump has sealing and lubricating effects, so it must be added in the specified amount.
3. Pump oil must be replaced regularly. When replacing, the previous waste oil must be discharged first. The cycle should be at least three months to six months.
4. Connect the wires according to the instructions.
5. Before stopping the mechanical pump, close the air inlet valve first, then cut off the power and open the air valve, and let the atmosphere into the pump through the air inlet.
6. During the operation of the pump, the oil temperature cannot exceed 75 degrees Celsius, otherwise the sealing will be loose due to the low viscosity of the oil.
7. Check the belt tightness of the mechanical pump, the speed of the motor, the speed of the Roots pump motor, and the sealing effect of the sealing ring from time to time.