OnRobot HEX-E QC User Manual page 214

HARDWARE SPECIFICATION
Unused holes can be blinded using a blind screw, and each fitting can be changed to a
different type to match the desired suction cup. The fittings and the blinding screws are
mounted or dismounted by screwing (2Nm tightening torque) or unscrewing them with the
provided 3 mm Allen key.
The thread size is the commonly used G1/8"; allowing for standard fittings, blinders and
extenders to be fitted directly to the VG grippers.
Vacuum
Vacuum is defined as the percentage of absolute vacuum achieved relative to atmospheric
pressure, i.e.:
% vacuum Bar
0% 0.00rel.
1.01 abs.
20% 0.20rel.
0.81 abs.
40% 0.41rel.
0.61 abs.
60% 0.61rel.
0.41 abs.
80% 0.81rel.
0.20 abs.
The vacuum in kPa setting is the target vacuum. The pump will run at full speed until the
target vacuum is achieved, and then run at a lower speed necessary to maintain the target
vacuum.
The pressure in the atmosphere varies with weather, temperature and altitude. The VG
grippers automatically compensate for altitudes up to 2km, where the pressure is about 80%
of sea level.
Air Flow
Air flow is the amount of air that must be pumped to maintain the target vacuum. A completely
tight system will not have any air flow, whereas real life applications have some smaller air
leakages from two different sources:
214
kPa inHg Typically used for
0.00rel. 0.0rel. No vacuum / No lifting capacity
101.3 abs. 29.9 abs.
20.3rel. 6.0rel. Cardboard and thin plastics
81.1 abs. 23.9 abs.
40.5rel. 12.0rel. Light workpieces and long suction cup life span
60.8 abs. 18.0 abs.
60.8rel. 18.0rel. Heavy workpieces and strongly secured grips
40.5 abs. 12.0 abs.
81.1rel. 23.9rel. Max. vacuum. Not recommended
20.3 abs. 6.0 abs.