Vacuum generators are designed to create a level of vacuum that is required for object handling tasks. These devices create a vacuum either pneumatically using compressed air or electrically using a displacement pump. The electrical generators are often referred to as vacuum pumps.
This article will provide all the relevant information on vacuum generators, what they are and how they work!
Table of Contents
- Vacuum Generators
- Vacuum Generators vs Vacuum Pumps
- Vacuum Generator Selection Criteria and Considerations
- FAQs (Frequently Asked Questions)
Vacuum generators are generally classed as being either pneumatic vacuum generators or electric vacuum generators (vacuum pumps). Here, we will take a look at both!
Pneumatic Vacuum Generators
The pneumatic vacuum generator, also commonly referred to as a vacuum ejector, uses a pneumatically driven nozzle to generate a vacuum. These models can be integrated directly into the system due to their lightweight and compact design and are suitable for applications that involve short and rapid cycle times.
Vacuum generators operate based on the venturi effect, hence commonly being known as a venturi vacuum generator. Depending on the number of nozzle pairs in use, pneumatic vacuum generators can be divided into the following 3 types:
Single-stage venturi vacuum generators consist of a venturi nozzle or jet nozzle through which compressed air is passed. Due to the narrowing feature of the jet nozzle on the compressed air vacuum generator venturi, the air is forced to accelerate. As the air passes through the nozzle and starts to expand, a vacuum is created at the expanded side of the gas vacuum generators.
This allows for the air to be drawn through the inlet and the compressed air exits through the silencer.
A Multi-stage vacuum generator venturi has multiple venturi nozzles arranged in a row. The compressed air is supplied through the connection port and then passes through the several vacuum generator venturi nozzles. As the vacuum is then created, the air is drawn through the inlet.
The typical suction rate from the inlet is the total suction from the individual nozzle of the vacuum generator multi-stage. In comparison to the single-stage vacuum generator, multi-stage vacuum generators can provide a far higher suction rate for the same amount of compressed air.
Compact vacuum generators have integrated valves with system monitoring technology. This allows these types of pneumatic vacuum generators to make it easier to control the pick-up and blow-off without the aid of an external valve. You will find these designs typically being used for completely automated handling systems.
Advantages of Pneumatic Vacuum Generators
- Typically very compact and lightweight which allows them to be closely installed to applications
- No moving parts which results in low wear and almost no maintenance
- No heat generation
- The vacuum is generated very fast
- Relatively low initial investment needed
Disadvantages of Pneumatic Vacuum Generators
- Compressed air must always be available
- The cost of compressed air will increase the total operation cost in the long run
Electric Vacuum Generators (Vacuum Pump)
The electric vacuum generator, also known as a vacuum generator vacuum pump, is typically used when high suction capacity is a requirement or when there is a lack of compressed air availability. The vacuum generator vacuum pumps operate by removing the air molecules from the vacuum chamber.
They generally consist of an eccentrically mounted rotary impeller that uses carbon blades. The impeller is pressed against the wall of the housing by the centrifugal force which allows there to be an excellent seal. The rotation of the impeller changes the size of each chamber and as the chamber becomes larger in size, the air inside it will expand.
This then causes the pressure to drop in the chamber which will create a partial vacuum. The air is thus drawn in, compressed, and expelled through the outlet. This high compression factor helps the vacuum generator vacuum pump provide high suction capacity and generate a high vacuum.
Advantages of Electric Vacuum Generators
- Capable of creating a very high vacuum, combined with a high evacuation volume
- Require small amounts of maitnenance
- Do not require compressed air systems
- One vacuum can be used as a hub to generate multiple vacuum locations
Disadvantages of Electric Vacuum Generators
- Not as simple as pneumatic vacuum generators in design
- Often larger in size
- Need a higher inital investment
Vacuum Generators vs Vacuum Pumps
When it comes to comparing the differences between compressed air vacuum generators and electrical vacuum generators, the key difference is that the pneumatic vacuum generators build up a vacuum quickly and have short cycle times. Due to their simple and compact design, they can be integrated directly into the system close to the vacuum suction cups.
In contrast, vacuum generator vacuum pumps create a high suction rate and high levels of vacuum. Since the vacuum is created using an electric motor, they are suited for applications where compressed air is not available.
Pneumatic vacuum generators are mainly used in pick and place robots in virtually all industries. A few examples are feeder applications in the automotive industry and end-of-line applications such as food packaging. Electric vacuum generators are mostly used as central vacuum generators in gantry systems as well as for packaging machinery.
Vacuum Generator Selection Criteria and Considerations
When it comes to the selection of the right vacuum generator, you must consider the following 5 points:
- Suction rate
- Vacuum level
- Evacuation time
- Air consumption
One easy comparison to make on vacuum generators is their suction rate. The values are based on standard conditions which means ambient temperature (68 Fahrenheit) and ambient pressure at sea level (14.7 PSI). The suction rate is usually given in CFM. To learn more about CFM, visit our What Is CFM and What Does CFM Mean on An Air Compressor?
The maximum suction rate is defined as the maximum flow rate that the vacuum generator evacuates from the environment. This results in free-flow, so the flow rate is lower when a workpiece is picked up. The required suction rate is a result of the internal volume of the suction pads and the piping.
You may require higher suction rates for porous materials like cardboard, this is more important than a high vacuum level.
The vacuum level is typically given as a percentage or a relative value. The vacuum level is specified in relation to the ambient pressure. A vacuum level of 80% means that the pressure is 80% lower than the ambient pressure.
If the ambient pressure is absolute pressure (14.7 PSI), an 80% vacuum will result in an absolute vacuum pressure of 2.94 PSI.
The evacuation time is the time in seconds that is required to create a specific vacuum level.
The air consumption is the amount of compressed air in SCFM consumed by the generator to generate its specific vacuum level. Visit our SCFM Vs ACFM Vs ICFM – What’s The Difference? Converting & Calculating or our SCFM vs CFM for Air Tools & Air Compressors to learn more about SCFM.
Depending on the requirement for your application, vacuum generators can either be powered pneumatically or electrically. The electrical generators are suitable for applications where compressed air is not available.
FAQs (Frequently Asked Questions)
There are many different types of vacuum generators that work slightly differently, but all on the same principle. Vacuum generators use nozzles or venturi’s to reduce the space for flowing air, as this air is forced through the nozzle its speed increases and the air expands. This causes a vacuum to be created on the expanded side.
A pneumatic vacuum generator, also commonly known as a vacuum ejector, uses a pneumatically driven (compressed air) nozzle to generate a vacuum. These models have a lightweight and compact design which allows them to be easily integrated directly into the system. They are typically suited to applications that have short and rapid cycle times.
To choose a suitable vacuum cleaner generator, you must consider the suction rate, vacuum level, evacuation time, air consumption, and operation of the vacuum generator. The maximum suction rate is defined as the maximum flow rate that the vacuum generator evacuates from the environment and is probably the most important consideration of them all. The vacuum level is typically given as a percentage which indicates at what pressure the vacuum is lower than the ambient pressure. The evacuation time is the time in seconds that is required to create the specified vacuum level, while the air consumption is a rating given in SCFM.
Pneumatic vacuum generators consist of a venturi nozzle or jet nozzle through where compressed air is passed. Due to the jet nozzle having a narrowing feature, the compressed air is forced to accelerate and expand as it passes through the nozzle, creating a vacuum at the expanded side. This, therefore, allows for the air to be drawn through the inlet and the compressed air exits through the silencer.
If you have any questions about vacuum generators, please leave a comment below, with a photo if applicable, so that someone can help you!