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Lift a part with vacuum suction

Holding direction matters even with a large suction force. Distinguish force pulling away from the pad from force sliding along its surface.

Normal suction holding on the left and tangential friction holding on the right, with separate suction, load and friction arrows.NormalTangentialFnWΔpDFnFfWSame Δp and area · different holding direction
Left: normal holding from a horizontal pad. Right: friction holding at a vertical pad. Fn is normal suction force, W is load and Ff is friction support.

What you will understand

  • Use pressure difference at the pad, not supply pressure
  • Separate normal holding from friction holding
  • Distinguish calculated margin from seal and leakage behavior

Blue: defined conditions · Red: calculated quantities. Diagrams are schematic.

  • Δp, D: pressure difference and effective diameter
  • Fn: normal suction / Ff: friction support
  • W: force due to weight and acceleration

The examples below are illustrative. Each example button loads its fixed values, units and mode. Ordinary calculator links do not load an example.

Define effective area and pressure difference

Δp is ambient absolute pressure minus pressure at the suction interface. Do not use ejector supply pressure directly. D is the effective suction diameter, which may differ from the pad outside diameter.

  • Actual pressure difference at the pad and ambient absolute pressure
  • Effective diameter, pad count and load distribution
  • Surface sealing, holes, grooves, roughness and porosity

Theoretical normal force Fn = Δp × nπD²/4

Choose the holding direction

Use Fn for a load normal to the pad and friction-based μFn for a tangential load. Reusing the same capacity after changing orientation can miss sliding.

For practical review

The model assumes equal load sharing and maintained seals. Eccentric CG, peeling moments and lateral acceleration require separate assessment. S and μ cannot universally account for every effect.

Comparison capacity: Fn/S normal, μFn/S tangential / required force W = m(g+a)

Read capacity minus required force

S reduces the theoretical force for comparison. Choose it for actual conditions; defaults are not recommendations. Distinguish a positive/negative difference from a complete selection decision.

Example: change orientation with the same pad inputs

Inputs

  • D = 50 mm; 2 pads; Δp = 0.06 MPa
  • Ambient absolute pressure 0.101325 MPa; m = 5 kg; a = 1 m/s²
  • S = 3; μ = 0.5 for tangential holding (illustrative assumptions)

Results

  • Theoretical normal force Fn ≈ 235.619 N; required W ≈ 54.033 N
  • Normal: comparison capacity 78.540 N → difference +24.507 N
  • Tangential: comparison capacity 39.270 N → difference −14.763 N

The tangential case does not meet the entered demand. A positive normal margin is not a safety approval because seals, leakage, eccentric loads and product ratings remain unchecked. S = 3 is not a recommendation.

Load the fixed values, units and mode for this illustration. Then edit them for your conditions.

Check leakage, response and loss of supply

Vacuum build-up time, leakage during motion and pad deformation matter in practice. Check the real part throughout the operating cycle, not only while stationary.

  • Pressure during pickup, transfer, stopping and release
  • Piping, valve and generator flow, leakage and monitoring response
  • Eccentric CG, peeling, allowable lateral force and pad deformation
  • Holding/fall prevention on supply loss and protection of people/equipment

Keep a review checklist

This checklist is a personal reminder, not a safety score or an automatic approval. It is not sent or saved.

Continue with another guide

Reference information and illustrative calculations. This content does not guarantee suitability or safety of a design. Confirm the actual materials, component specifications and operating conditions.