Vacuum suction cups are a common type of vacuum pump used in vacuum transport and CNC machining centers. The main principle is to use the vacuum pump to create a pressure difference at the suction cup to hold various types of workpieces and objects. But how do we know the suction force that the vacuum suction cups can produce in vacuum pump applications?
The estimation of the suction force of vacuum suction cups is mainly based on the pressure formula, F=PS. In vacuum suction applications, the calculation method will be slightly adjusted as follows:
F≈(101-Absolute pressure P)×S suction pad area×10-2
In the formula, F is the theoretical suction force that the vacuum suction pad can produce, measured in kilogram force (Kgf); P is the absolute pressure that the vacuum pump can achieve, measured in kPa; 101 is the standard atmospheric pressure value, which needs to be adjusted in some special altitude areas; S is the effective area of the vacuum suction cup, measured in square centimeters (cm2).
For example, if the vacuum suction pad can achieve a vacuum degree of 10kPa through the vacuum pump, then the pressure difference between it and atmospheric pressure is 101-10=91kPa. At this time, the effective area of the suction cup is 10 square centimeters. Therefore, the suction force of this vacuum suction cup can theoretically reach about 9.1Kgf.
This estimation method ignores the influence of the flow rate of the vacuum pump on the maintenance of vacuum degree and suction force. In actual use, the size of the suction force of the vacuum suction cup is also related to its flow rate. Because the system of rough and low vacuum airflow cannot achieve complete sealing, leakage is always present.
In this case, the larger the flow rate of the vacuum pump, the smaller the proportion of leakage, and the more favorable to maintain the vacuum degree of the suction vacuum system, thus obtaining a larger suction force. At the same time, a larger flow rate can also achieve a faster vacuum suction reaction time.
For example, if two pumps have the same ultimate vacuum degree, Pump A has a flow rate of 1 L/min, and Pump B has a flow rate of 20 L/min. Firstly, the two pumps have a significant difference in pumping speed, so they will reach the predetermined vacuum degree at different times. Secondly, under the same leakage of 0.1 L/min, the vacuum degree of Pump A will decrease significantly, because the leakage of 0.1 L/min is too large for Pump A. However, the same leakage is not a big deal for Pump B, and it can still maintain a higher vacuum degree.
Therefore, although the ultimate vacuum degrees of the two pumps are the same, in reality, the large flow rate vacuum pump can produce a greater and quicker suction force.