OnRobot VGC10 User Manual page 166

Hardware Specification
Vacuum
Vacuum is defined as the percentage of absolute vacuum achieved relative to atmospheric pressure, i.e.:
% vacuum Bar
0.00rel.
0%
1.01 abs.
0.20rel.
20%
0.81 abs.
0.41rel.
40%
0.61 abs.
0.61rel.
60%
0.41 abs.
0.81rel.
80%
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 g rippers
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:
• Leaking vacuum cup lips
• Leaking workpieces
The smallest leak under a vacuum cup can be hard to find (see picture below).
Leaking workpieces can be even harder to identify. Things that look completely tight might not be tight at
all. A typical example is coarse cardboard boxes. The thin outer layer is often requiring a lot of air flow to
create a pressure difference over it (see figure below).
Therefore, the users must be aware of the following:
• VG grippers are not suitable for most uncoated, coarse cardboard boxes.
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.
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