How an ejector works
An ejector (vacuum generator) creates vacuum from compressed air using the Venturi principle. Compressed air passes through a restricted nozzle, the flow velocity rises sharply and the static pressure in that zone drops below atmospheric. The suction port is connected to this low-pressure zone, so air is drawn from the vacuum cup or from the chamber being evacuated. Nothing inside the device moves.
When an ejector beats a vacuum pump
- The gripping point is far from the machine room: mounting the ejector on the gripper keeps the vacuum line very short, which cuts evacuation time and shortens the machine cycle.
- Fast suction and release cycles: an ejector switches instantly with a solenoid valve, which suits high-speed pick-and-place, while a vacuum pump suits continuous duty better.
- Small vacuum demand spread over many points: one small ejector per point is usually cheaper and more flexible than routing a central vacuum system to every station.
- No space for a machine, no maintenance wanted: an ejector has no bearings and no oil; it only needs clean, dry compressed air.
Conversely, when a large suction flow is required for hours on end, a vacuum pump remains more economical because an ejector consumes compressed air the whole time it runs. The common approach is to combine both: a central vacuum system for the base load and ejectors at high-speed gripping points.
How to size an ejector
- Maximum vacuum level (typically -60 to -90 kPa) must suit the material handled: a sealed surface needs a high vacuum level, a porous material needs more suction flow.
- Suction flow determines the evacuation time together with the line volume and the number of cups.
- Supply pressure (usually 4-6 bar) and air consumption; feeding above the design pressure lowers efficiency and wastes air.
- Additional functions: an air-saving valve that shuts the supply once the vacuum level is reached, a fast blow-off valve to release the part on time, and an inlet filter to keep dust out.
Related equipment at AVA
- Vacuum generators (ejectors)
- Vacuum cups and cups from 9 mm to 120 mm
- Damping springs, fittings
- Solenoid valves for suction and release control
- Vacuum pumps & blowers for the base load of the system
Need the right ejector and cup for your product? Send AVA the material, size and cycle time and we will propose a configuration.