A vacuum gripper doesn't grip by squeezing — it grips by pressure difference. A pump evacuates the air trapped under a rubber cup pressed against the object, and atmospheric pressure on the outside pushes the cup (and the object) inward against that low-pressure pocket. The holding force is simply that pressure difference times the sealed contact area, summed over every cup that still has a good seal.
F_hold = ΔP · A_cup · n_cups
ΔP = P_atm − P_vacuum
dP/dt = k_pump·(P_target − P) + k_leak(surface)·(P_atm − P)
F_required = S · m · (g + a)
- Target vacuum — how hard the pump works to pull the cups down toward absolute vacuum; higher means more holding force per cup, but real pumps top out well short of a perfect vacuum.
- Active suction cups — a clogged filter or torn cup takes a cup out of service; fewer active cups means less total sealed area for the same payload.
- Surface material — a rough or porous surface (cardboard, textured wood) never seals perfectly: air constantly leaks back in, so the achieved vacuum settles below the pump's target. Smooth glass or painted metal seals almost perfectly.
- Move acceleration — lifting and swinging the payload adds an inertial load on top of its static weight; a safety factor (2×) is required so a jolt during the move doesn't exceed the margin.
Real-world relevance: vacuum end-effectors are the default for flat, non-porous parts in electronics and glass handling and for large flat cartons in palletizing — but they fail unpredictably on leaky packaging, which is exactly why cup count, pump capacity and surface compatibility all have to be verified together before deployment.