Vacuum suction cup will not hold: causes and air ingress inspection

If a vacuum gripper stops holding a workpiece, increasing the vacuum setpoint does not replace diagnosis. The fault may be in the circuit, the cup or a changed workpiece. Identify what changed first: material, surface, cups, hoses or cycle conditions.

The cover is an illustration of a generic gripper on a supported workpiece, not a photograph of a particular model or client site.

Match the symptom to the inspection

Symptom	First inspection focus
Fault started after a hose change	Connections, kinks, internal diameter and line length
Only one cup loses vacuum	Sealing lip, contact, contamination and that branch's fitting
A nonporous reference surface works but the new workpiece does not	Porosity, roughness, coating and cup suitability
All cups evacuate slowly	Generator, filter, valves and flow restrictions
Vacuum is established but the part slips during the cycle	Gripper arrangement, contact, load direction and motion

Vacuum condition and holding ability are related but distinct checks. A reading at the generator may not describe conditions at a remote cup.

Prepare a comparable test

Use a supported workpiece and the manufacturer's service mode. Do not use a suspended load as a test fixture. Record workpiece type, surface condition, generator mode, time to setpoint and pressure measurement location.

Compare sound and suspect branches under the same conditions. Isolate circuit sections only where the procedure permits it. Record disconnected consumers: isolation changes the system, so a different operating mode must not be mistaken for a successful repair.

When airborne ultrasound helps

Under a pressure differential, an accessible hose, fitting or seal defect may produce a distinguishable ultrasonic signal. A directional airborne sensor supports localization. See the vacuum system inspection route.

Ultrasound does not select cup material or verify load capacity. No signal does not prove tightness; consider access, background noise and flow. LEAKChecker or SDT340 with an airborne sensor can support source localization.

Gather cup selection data

Provide workpiece material and shape, surface condition, temperature, oil or moisture, dimensions and mass, motion direction, cycle parameters and the available vacuum system. Lip material, shape and effective contact area must suit the task. Nominal diameter alone does not define an allowable load.

Select and accept the gripper using manufacturer documentation and testing in the required operating mode, including motion. Replacing a worn lip may remove air ingress but cannot compensate for an unsuitable surface or arrangement.

Verify the repair

Record the leak location, replaced component, before-and-after conditions and repeat cycle results. For KEG TRK, attach a circuit diagram and fitting photos to help select an inspection method by task.

Related: air and gas leak detection, compressed air inspection route.

Sources

Schmalz suction cup design, cup materials, FQE troubleshooting manual and SDT airborne sensor documentation. This article outlines an initial inspection approach, not model-specific operating parameters.