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2_Kap_VT_EN_2016_VT_KAT 18.02.16 09:36 Seite 46
PA01019111_inh_EN.pdf
Vacuum Knowledge
System Design – Calculation Example
PA01019111_inh_EN.pdf Weight Calculation of a Workpiece PA01019111_inh_EN.pdf

Schmalz - The Company It is important to determine the weight (m) of the workpiece to continue with additional calculations. It is calculated based on the

following formula:

Vacuum Knowledge m = L x B x H x ρ
= Weight [kg]
m
L = Length [m]
B = Width [m]
H
= Height [m]
Vacuum Suction Cups ρ = Density [kg/m ]
3

Our example:
m = 2.5 m x 1.25 m x 0.0025 m x 7,850 kg/m³
Special Grippers m = 61.33 kg

Vacuum Grip- ping Systems Theoretical Holding Force of a Suction Cup

To calculate the theoretical holding force, we show and describe the three most important and most frequently occurring load cases
(handling sequences).
Mounting Elements Important:

For the following, simplified representations of the load cases the calculation must be based on the worst load case with the highest,
theoretical holding force. This is the only way to ensure that the suction cup grips the workpiece safely during the entire handling process.

Vacuum Generators Safety factor S:
The safety factor S must be adjusted in accordance with the condition of workpiece surface . The safety factor has a minimum value of
1.5 for smooth and dense workpieces. A safety factor of 2.0 or greater must be used for critical, heterogeneous, porous, rough or oiled
workpieces.

Valve Technology Friction coefficient μ:
The friction coefficient μ describes the relationship between friction force and normal force. We cannot issue generally valid specificati-
ons for the friction coefficient between suction cup and workpiece. The friction coefficient μ therefore has to be determined correctly
Switches and Monitoring The following can be used as reference values.
through tests.

= 0.2 … 0.3 for wet surfaces
= 0.5
Filters and Connections = 0.6 for rough surfaces
for wood, metal, glass, stone, etc.

Calculation for oiled surfaces:
For standard suction cups without specified lateral force, the recommended reference value is μ = 0.1 to 0.3. To obtain a more precise
Services value, tests must be completed on the original workpiece.

For suction cups that have an explicitly specified lateral force on a dry or oiled surface, the friction coefficient μ can be calculated
using the following formula:
Contact µ = F / F N
R
Lateral force on a dry or oiled surface/suction force
Index of Products The calculated μ value can then be used in the formula of the respective load case (I to III).

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PA01019111_inh_EN.pdf