There are a number of ways to pick something up from where it is, move it to where you want it, and put it down. If it’s on a skid, you can use a forklift. If it’s got an eyebolt – or if you can get a strap or chain around it, you can use a crane…or a forklift, provided you can safely secure the strap or chain to one of the forks. Or, if there’s enough surface area for a suction cup to sit on, you can use vacuum.
The two most popular methods of that are vacuum pumps, and venturi-type vacuum generators. Both are capable of creating a high vacuum for secure attachment of the vacuum cup to the object, and both can generate enough vacuum flow, under moderate vacuum levels, to overcome vacuum leakage when picking up objects with porous or slightly irregular surfaces. In a facility with multiple ‘pick and place’ stations or operations that are some distance from each other, vacuum generators are an inexpensive and easy solution, as they can be installed right at the point of use. If the points of use are relatively close together, though, it can make sense to consider a centralized vacuum pump from an operating cost standpoint…the electricity to run the vacuum pump’s motor is oftentimes cheaper than the compressed air to run the vacuum generators. Vacuum pumps still require a lot of maintenance, and when they break, they’re notoriously expensive to fix, so maintenance cost and reliability are important considerations as well.
EXAIR E-Vac Vacuum Generators are compact, single-stage venturi products that generate rated vacuum on demand. With no moving parts to wear, or electrical components to burn out, they address the concerns I just mentioned about maintenance costs and reliability of electric-driven vacuum pumps. E-Vacs are available in three basic configurations:
- High Vacuum: These are capable of generating up to 27″Hg vacuum levels, and are specified went the object to be lifted has a smooth, non-porous surface for the Vacuum Cups to pull down on. With that kind of tight seal and high vacuum level, they’re effective, safe, and reliable.
- Low Vacuum: Why would you not want the vacuum to be as high as possible? Well, if you’re picking up something with an irregular surface, or if the material is porous, you’re going to have leakage past the lip of the Vacuum Cup, or through the pores of the material, meaning you won’t be able to get that high of a vacuum in any case. EXAIR Low Vacuum E-Vacs are specified for lifting objects like this. They generate sufficient vacuum (up to 21″Hg) and enough vacuum flow at those levels to overcome the leakage for the same effective, safe, and reliable operation as their High Vacuum counterparts.
- Adjustable: These offer a combination of the benefits of the High and Low Vacuum Generators. By threading the plug in or out of the body, you can control the amount of vacuum – and vacuum flow – that they generate. This can be particularly beneficial if your system needs to pick up a variety of loads. They also have a larger throat diameter, so if you’re picking up something with dust or other contamination on the surface, it won’t clog up like an In-Line model (with a much smaller throat) would. These are commonly used for work holding tables as well, since those are almost always pulling in particulate from the surface.
Once we’ve determined the appropriate style of E-Vac Vacuum Generator for the application, we’ll move on to specifying the correct Vacuum Cup(s). EXAIR offers a wide variety of these, from small Bellows style Cups as small as 3/4″ in diameter, to round Vacuum Cups ranging in diameter from 1″ to 6″. We use this table from our catalog to determine how many of which Vacuum Cup to use. They’re rated for the amount of weight each Cup is capable of lifting, at specific vacuum levels.
For example, let’s say we need to pick up a solid object with a flat, smooth top that weighs 5 pounds. We’re going to apply a 2x safety factor, so we’re going to select a Vacuum Cup rated for at least 10 pounds, and since the surface is flat & smooth, we don’t expect a need to overcome any vacuum leakage, so we’ll use the rating at 27″Hg. In this case, we can use a Model 900764 Oval Vacuum Cup, which are rated for 10 pounds at 27″Hg.
If it’s a small-to-medium sized object with a round or square top, you can usually just use one Vacuum Cup to pick it up. For larger objects, you’ll want to use multiple Vacuum Cups to keep it balanced. Let’s say our 5 pound object is a thin plate that’s long and narrow. For that, we can use two Model 900752 1″ Small Round, or two Model 900767 1″ Round Bellows Vacuum Cups (both rated for 5.2 pounds each at 27″Hg), spaced out appropriately for the length, to safely pick and place the object.
If the object’s top surface isn’t smooth & flat, and/or if the material is porous, we’re going to select Vacuum Cup(s) that are rated for the weight (again applying a 2x safety factor) at a lower vacuum level. Let’s say our 5 pound object is a cardboard box. We know a Low Vacuum (Porous) E-Vac can create a vacuum of up to 21″Hg (with no vacuum flow) or 15″Hg with a moderate amount of vacuum flow to overcome leakage. We can use one Model 900754 2″ Round or Model 900769 2″ Bellows Vacuum Cup, which are both rated for at least 10 pounds at 15″Hg. We could also use two Model 900764 Oval Vacuum Cups, since they’re rated for 5.5 pounds each at 15″Hg.
If you’d like to find out more about generating vacuum with compressed air, or if you’d like help in specifying the right E-Vac(s) and Vacuum Cup(s) for your application, give me a call.
Russ Bowman, CCASS
Application Engineer
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