How to calculate Vacuum Force?

Question

Hi, if I have a suction cup of 10mm dia, connected to vacuum pump. the pump able to set to 0.1torr, 0.01torr. what is the suction force(kg) at 0.1torr & 0.01torr.

Answer 1

Technically there is no vacuum force. What you have is a lack of pressure on the vacuum side, opposing atmospheric pressure on the other side.

This differential force is the differential pressure times area.

Atmospheric pressure  is 101,325 Pascals. One torr is 1/760 of an atmosphere.

For the suction cup,

Area = pi*D^2/4 = 0.25*pi*10^-6m^2.

DeltaPressure1 = (1 - 1/760*.1)  atmospheres

DeltaPressure2 = (1 - 1/760*.01) atmospheres

Then, F = DeltaPressure * area

Force will be in Newtons, as Pascal = N/m^2. kg is a unit of mass, not force. SI does not recognize gravimetric units, so don't do kgf. But, if you insist, you can find conversion factor from N to kgf.

Force is about the same for both; that is why we don't bother with hard vacuum for suction applications.