About the problem of using micro vacuum pump to adsorb objects.doc
Micro vacuum pumps, micro negative pressure pumps, and vacuum pumps are often used for object adsorption. There are several issues that need to be noted:
1. The meaning of vacuum adsorption:
It refers to connecting the suction port of the vacuum pump to the object to be adsorbed through a suction cup, a tube, etc. At this time, the suction cup is similar to a closed container, and the suction cup is evacuated, causing the internal air pressure to change from normal pressure to negative pressure. The effect of pressure difference is to achieve the purpose of attracting objects.
Therefore, you must choose a true miniature vacuum pump, such as PK, PC, VCH and other series products, but not a gas sampling pump, such as SA, SB, PM series (see "Micro vacuum pump, air pump classification" for details.)
2. The theoretical formula for calculating the adsorption force:
Fâ‰ˆ0.01 (101ï¼P absolute pressure) S suction cup area
(Ie Fâ‰ˆ0.01 Ã— the maximum negative pressure of the pump Ã— the area of â€‹â€‹the suction cup)
In the above formula, F: theoretical adsorption force, unit: Kgf (kg force)
P Absolute pressure: the absolute vacuum degree of the micro vacuum pump, the unit is taken: KPa (kPa)
S suction cup area: the effective area of â€‹â€‹the suction cup, the unit is taken: cm 2 (square centimeter)
As can be seen from the above formula, the size of the adsorption force is theoretically independent of the pump flow rate, but in actual use it is related to the flow parameter. The reason is as follows: because the gas circuit system cannot be theoretically sealed, there is always a certain leakage. In this case, the larger the flow rate of the micro vacuum pump, the smaller the proportion of leakage, and the more it is conducive to the pump to maintain a higher vacuum degree, thereby obtaining greater adsorption force. For example, there are two pumps with the same ultimate vacuum degree, the flow rate of pump A is 1L / min, and the flow rate of pump B is 20L / min. Also in the case of leakage of 0.1L / min, the vacuum degree of pump A will be reduced a lot because of 0.1 The leakage of L / min is too large for it. But the leakage of 0.1L / min is nothing to B pump, it can still maintain a high vacuum. Therefore, although the vacuum degree of the two is the same, in practice, the suction force generated by the B pump is greater.
Therefore, when selecting the pump, the two indexes of vacuum degree and flow rate must be considered at the same time. It is impractical to only pay attention to the index of vacuum degree.
For the problem of the speed of adsorption time, please refer to "Vacuum of the Vacuum in the Vessel with the Pumping Time and Calculation Tool when Pumping the Closed Container"
Regarding the release of objects after being sucked. When you need to release the sucked object, you must first stop the pump, do not continue to vacuum. After the pump is stopped, the object may not immediately fall off, because the pump has a certain pressure holding capacity, and the vacuum will continue to be maintained for a while. For immediate release, the gas system should add another branch, connect a switch valve, the pump stops and opens the valve at the same time, immediately eliminate the gas system vacuum, so that the object can be released reliably.
3. The maximum suction force (adsorption force) that can be provided by common micro vacuum pumps + weight list of attracted objects (blue represents the most commonly used model)
Maximum negative pressure (kPa)
(Usually calculated according to local atmospheric pressure = 100kPa)
Maximum adsorption force (Kgf kilogram force)
(Assume that the suction cup area is 1 square centimeter)
Able to lift objects from bottom to top
Maximum weight (g) (in theory)
1. Under the same negative pressure, the micro-vacuum pump with a large flow rate is stronger than the actual suction force with a small flow rate (because the replenishment is fast, for the system, the ability to maintain this negative pressure is strong). For example, the peak flow rate of VCA5038 is 38L / MIN. Compared with 15L / MIN of PCF5015, although the negative pressure is the same, the actual adsorption force is stronger than PCF5015N.
2. The above adsorption weights refer to the situation of vertical upward adsorption (that is, the suction force of the pump is upward, against the gravity of the object downward); vertical downward adsorption and side adsorption are much more complicated because they involve the friction coefficient of the contact surface Factors such as different and different stress conditions, and even the problem of moving after adsorption, can not simply choose based on the above table.
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