Types of vacuum generators
Vacuum ejectors can be classified according to three main criteria: number of vacuum stages, physical principle of vacuum generation, and mounting type.
Single-stage and multi-stage ejectors
According to the number of vacuum stages, we distinguish between single-stage and multi-stage ejectors.
Single-stage ejectors perform the entire vacuum generation process in one step. This offers simplicity but limits the achievable vacuum level.
Multi-stage ejectors utilize a series of stages to progressively increase the vacuum. This multi-step approach allows them to achieve higher vacuum levels with a lower supply pressure compared to single-stage models, resulting in greater efficiency.
Venturi vacuum generators
Venturi vacuum generators operate on the Venturi effect, which utilizes Bernoulli's principle. As compressed air speeds up through a narrowed nozzle, the pressure decreases according to Bernoulli's principle. This creates a low-pressure zone that draws in surrounding air, resulting in suction.
Venturi vacuum generators are suitable for 80% of applications due to their simplicity and flexibility. For specific applications, such as handling sensitive or porous workpieces, other vacuum systems such as contactless vacuum grippers may be more suitable.
Individual and block-mounting type vacuum generators
Vacuum generators come in two main mounting configurations: individual and block.
Individual mounting is ideal for situations where you only need a single ejector. It offers a simple and cost-effective solution.
Block mounting is recommended when you require multiple ejectors that need to be grouped together and controlled centrally. This allows for efficient use of space and centralized control via industrial communication systems like fieldbuses.
SMC offers even more flexibility with hybrid systems that integrate valves and ejectors into a single unit. These simplify the control of applications requiring both positive and negative pressure, while also streamlining machine design. These hybrid vacuum units provide remote and flexible vacuum control through various industrial communication protocols, including IO-Link.
Typical applications of vacuum ejectors
Vacuum ejectors demonstrate their versatility across a wide range of applications. They are particularly well-suited for:
- Systems with low vacuum flow requirements
- Point-to-point use of one or more vacuum grippers for handling
- Environments without a vacuum supply
What advantages do vacuum ejectors offer compared to other vacuum generation systems?
Industrial vacuum ejectors offer the following advantages:
- Maintenance-free and flexible mounting: Compared to other systems, they have no rotating parts, are therefore maintenance-free and offer more flexibility in mounting.
- Installation in any position and at any point in the application: They can be installed anywhere in the system.
- High response speed and vacuum generation: They quickly reach the desired vacuum level.
- Compact and lightweight: They are space-saving and easy to handle.
- No heat generation: They do not contribute to heating the environment.
- Energy-saving functions: They have integrated energy-saving functions.
- Additional integrated functions: They make control and monitoring easier.
Selection criteria for vacuum generators
Selecting the ideal vacuum ejector involves considering several key factors:
- Nozzle and Diffuser Design: These components significantly impact both the maximum suction flow (speed) and the achievable vacuum pressure (strength). A smaller nozzle diameter creates a higher vacuum but with a lower flow rate. Conversely, a larger nozzle offers a higher flow rate but with a lower achievable vacuum.
- Suction Flow and Vacuum Pressure Requirements: Determine the specific suction flow (air volume) needed for your application and the desired final vacuum pressure for effective handling. Remember, the response time of your system (how quickly it reaches the desired vacuum) is influenced by both the chosen flow rate and the piping diameter.
- Leakage Considerations: The workpiece itself can impact performance due to leaks caused by its shape, porosity, or other factors. For applications with potential leaks, SMC recommends using a lower vacuum pressure setting and an ejector with a higher suction capacity. This helps compensate for these leaks and ensures successful operation.
