Types of vacuum ejectors
Vacuum ejectors, or vacuum generators, can be classified according to three main criteria: the number of vacuum stages, the physical principle of vacuum generation, and the type of mounting.
Single-stage and multi-stage ejectors
Vacuum ejectors are available in two main mounting configurations: single-stage and multiple-stage.
- Single-stage ejectors generate vacuum in a single step, offering simplicity but with limited vacuum levels.
- Multi-stage ejectors use multiple stages to gradually increase vacuum, achieving higher levels with lower supply pressure for greater efficiency.
Venturi-effect vacuum ejectors
Vacuum ejectors operate thanks to the Venturi effect, which relies on Bernoulli's principle. When compressed air accelerates through a narrow nozzle, the pressure drops, creating a low-pressure zone that draws in surrounding air, generating suction.
Venturi vacuum ejectors are suitable for 80% of applications due to their simplicity and flexibility. For specific applications, such as handling delicate or porous parts, other vacuum systems—like non-contact grippers—may be more appropriate.
Single and manifold-mounted vacuum ejectors
Vacuum ejectors are available in two main mounting configurations: single and manifold.
- Single mounting is ideal when only one ejector is required. It provides a simple and cost-effective solution.
- Manifold mounting is recommended when multiple ejectors need to be grouped and centrally controlled. This allows efficient use of space and centralized control via industrial communication systems such as fieldbuses.
SMC offers even greater flexibility with hybrid systems that integrate valves and ejectors into a single unit. These systems simplify the control of applications requiring both positive and negative pressure, streamlining machine design. These hybrid vacuum units provide flexible remote vacuum control through various industrial communication protocols, including IO-Link.
Typical applications of vacuum ejectors
Vacuum ejectors are highly versatile and suitable for a wide range of applications, including:
- Systems with low vacuum flow requirements
- Point-to-point use of one or more vacuum gripping systems for handling
- Environments without a vacuum supply
What advantages do vacuum ejectors offer compared to other vacuum generation systems?
Ejectors provide the following advantages:
- Flexible, maintenance-free mounting: Unlike other systems, they have no rotating parts, requiring no maintenance and allowing flexible installation.
- Installation anywhere in the application: They can be installed at any point in the system.
- High response speed and vacuum generation: They quickly reach the desired vacuum level.
- Compact and lightweight: They are small and easy to handle.
- No heat generation: They do not contribute to environmental heating.
- Energy-saving functions: They include built-in energy-saving features.
- Additional integrated functions: They facilitate control and monitoring.
How can I select the right vacuum ejector?
Choosing the ideal vacuum ejector involves considering several key factors:
- Nozzle and diffuser design: These components significantly affect both the maximum suction flow (speed) and the achievable vacuum level (force). A smaller-diameter nozzle creates a higher vacuum level but lower flow. Conversely, a larger nozzle provides higher flow but a lower vacuum level.
- Suction flow and vacuum level requirements: It is important to determine the specific suction flow (air volume) required for the application and the desired final vacuum level for effective handling. Additionally, the system’s response time (how quickly it reaches the desired vacuum level) is influenced by both the selected flow and the pipe diameter.
- Consideration of leaks: The workpiece itself may impact performance due to leaks caused by its shape, porosity, or other factors. For applications with potential leaks, SMC recommends using a lower vacuum level and an ejector with higher suction capacity. This helps compensate for losses and ensures successful operation.