Vacuum Cups — Choosing the Right Size, Shape and Quantity

There is a lot to be said about EXAIR’s E-Vac systems. We have over 10 pages dedicated to this in our catalogue, and many blogs. Click here to see a great blog about selecting the correct E-Vac. Once you have selected the correct E-Vac Generator, we now need to set you up with the right accessories. The connectors and hoses are the easy part – this circles and squares. The magic comes when selecting the proper cup size, shape and quantity. Let’s start by looking at the 3 shapes available; Round, Oval and Bellow.

Round Cups are great for smooth, flat surfaces. They will grip and release quickly, and hold their shape well over extended use. These grip very well on vertical surfaces. For light lifting, use the non-cleated cups, and the cleated cups for heavy lifting. AS you see here we offer a small round and a large round cup.

Oval Cups have the largest surface and therefore provide the most vacuum. You will want to use these on the very heavy items. These are designed to handle flat rigid sheet materials like wood, glass, cardboard boxes and the bulkier items with a flat surface.

Bellow Cups are where we turn when your surface is uneven or textured. The “convolutions” or folds, provide a collapsible area that allows the cup to quickly compress when it reaches uneven surfaces. This cup will take longer to attach and to release due to the larger volume of the cup.

It’s important to note that all EXAIR vacuum cups are vinyl and are ideal for general purpose applications and will wear well. The Durometer rating is A50 and the Temp range is 32°F to 125°F.

From the information above, you should be narrowing down the shape of the cup you need based upon your product. But each of these shapes come in different sizes. Here is a table that shows you all the sizing options of each cup. You will want to keep in mind the size of your product, and the size of these cups. You will most likely need multiple cups to lift your item, so be thinking about how the actual size of the cups will fit evenly spaced on your product. The next step will get us home…

Our last step is to determine exactly how many cups we need to make this a viable and safe application. The first step is to calculate the amount of weight we need to lift. This is determined using a safety factor of 2 for cups positioned horizontally, and a factor of 4 for cups positioned vertically. So if you are moving a 10 lb box, and the cups are on top, you need to account for 20 lbs, and if the cups are on the sides, you need to account for 40lbs. Using the table below, you can see how many pounds that a single vacuum cup can hold, according to the “Hg applied. *** “Hg is based upon the E-Vac you chose earlier ***

As we put all this together it would look something like this. Using the example above, with a box size of 12″x12″x12″ weighing 10 lbs. We will be picking this up with the cups on top of the box, so our total safety weight is 20 pounds, You can see that there are many options that can get this job done. You can use 1,2,3, or even 4 vacuum cups. 1, 2, or 3 E-Vac’s. The key here is to think about safety first, and then consider what issues may arise if something goes wrong. In this scenario, I would consider what is in the box. But if it falls, will it break? If it breaks how much will that cost you?. Also, what happens to production if something tweaks the cups and boxes start piling up. If the penalties are low, I would use 1 cup like a large round (900756) and 1 E-Vac that pulls 10 Hg”. This gives me 34.8 pounds of lift. More than enough. If the box falls and will cost a lot of money, break, slow the process, the 1 cup option is still ok, but I would make this 3 small round cups (900755) and 1 E-Vac that will pull 10 Hg”. This gives me 12.1 pounds of lift on each cup, so if one doesn’t seat correctly, the other 2 (or even one) will still protect me. There are multiple other options as well.

At EXAIR, we have a lot of experience walking through these scenarios and helping make recommendations. Please feel free to call and ask for any of the application engineers for questions or assistance.

Application Engineer

Brian Wages

EXAIR Corporation
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Adjustable Vacuum Levels for Different Materials from These Vacuum Generators

When determining a single vacuum generator that will fit a variety of demands, whether it be varying weights, surface finishes or materials, the Adjustable E-Vacs can make quick work of the task at hand. This minimizes the number of parts needed for a variable product line. It also means each application can be adjustable as well. So why would this be needed?

Let’s look at a custom woodworking shop. They could be lifting slabs of lumber that may be rough cut, maybe they are lifting a smooth epoxy river slab, or even sheet of MDF. Each one of these materials will require some adjustment on the vacuum end. The reason being the surface finish and porosity of each material is considerably different.

MDF, expanded out as Medium Density Fiberboard is a common material for woodworkers to use. This material looks and feels smooth and fairly solid. The trick is, it is actually a porous material. You can hook a vacuum hose to one side of it and hold a piece of notebook paper to the other side because the vacuum flow will be pulling through the MDF. This presents a problem when trying to use vacuum to pick and place the board. You will need a higher vacuum flow in order to compensate for the leakage of air when pulling a vacuum. An epoxy coated slab on the other hand, is generally a smooth surface that is non-porous and will require less vacuum flow.

Adjustable E-Vac: How it works

The greatest benefit to the Adjustable E-Vac is being able to easily adapt to meet the needs for both of these materials with a tool-free adjustment. A great example of this is in the video below.

If you would like to discuss which of the Adjustable E-Vacs is right for your variable application, reach out an Application Engineer today. We can all help you determine which of the 4 Adjustable E-Vacs will best fit your application and even help you understand what kind of adjustments will need to be made.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

The Venturi Effect: Discovered by Giovanni Battista Venturi

Giovanni Battista Venturi was born in 1746 to an affluent family in Reggio, Italy. An aspiring student, Giovanni was ordained as a priest and a professor by the age of 23. An avid historian of science at the University of Modena, he was the first to emphasize Leonardo da Vinci as a scientist rather than just an artist as he’s more commonly known. Despite his love for history, it wasn’t long before the University of Modena became aware of his talents in mathematics where they appointed him as professor of geometry and philosophy in 1774. During his tenure at the University of Modena, Giovanni was promoted to the Professor of Experimental Physics, served as the Duke of Modena as the State engineer and auditor, later serving diplomatic roles in both France and Switzerland.

Giovanni is most well-known for his work in developing what is now known as the venturi effect. In 1797, he published a study on the flow of water through short cylindrical tubes. It wasn’t until 1888 that Venturi’s design was applied to something practical when a man named Clemens Herschel received a patent for the first commercial venturi tube. The original purpose of the venturi tube was to measure the amount of water used in individual water mills and is still used to this day as a means of measuring fluid flows.

Venturi tube.jpg
Venturi Tube

The venturi effect is a principle in fluid dynamics and states that a fluid’s velocity must increase as it passes through a constricted pipe. As this occurs, the velocity increases while the static pressure decreases. The pressure drop that accompanies the increase in velocity is fundamental to the laws of physics. This is known as Bernoulli’s principle. Below is an illustration of how the venturi effect works inside of a constricted tube.

venturi

In everyday life, the venturi principle can be found inside of many small engines such as lawn mowers, gas powered scooters, motorcycles and older style automobiles. Inside the carburetor, there is a small tube through which filtered air flows from the intake. Inside of this tube is a short narrowing. When the air is forced to constrict, its velocity increases and creates a vacuum. This vacuum draws in fuel and mixes with the air stream causing it to atomize.  As the throttle valve is opened further, more fuel is forced into the engine. This increases the RPM and creates more power.

inlineworks
In-Line E-Vac

This principle is also applied to EXAIR’s line of E-Vac products to create vacuum. The .gif below illustrates how an In-Line E-vac works. (1) Compressed air flows through the inlet (2) and is directed through a nozzle, constricting the flow of air. (3) As the air stream exhausts, it expands causing a decrease in pressure and an increase in velocity prior to passing through the venturi. (4) A vacuum inlet tangential to the primary airflow is located at the suction point between the orifice and the venturi. (5) The airflow that is drawn through the vacuum inlet mixes with the primary airstream, then exhausts on the opposite end.

The venturi effect is used in a variety of other EXAIR products used for cooling, drying and cleaning, in addition to the vacuum generators. If you have a process in your facility that may benefit from an Intelligent Compressed Air solution, give us a call. We’d be happy to discuss your application and implement a solution to both reduce your compressed air costs and improve worker safety.

Tyler Daniel
Application Engineer
E-mail: TylerDaniel@exair.com
Twitter: @EXAIR_TD

Photo: Venturi Tube with labels by ComputerGeezer and Geof.  GNU Free Documentation License

How To Choose The Right Style & Size Vacuum Cup

When you are using vacuum to pick and place different objects, how do you know which style vacuum cup and size you need?  EXAIR offer’s (3) different styles of vacuum cups in a variety of sizes to cover a wide variety of applications.

The first is the round cup, they are suited to smooth, flat surfaces.  They grip and release quickly, hold their shape with frequent use, and grip well when used with vertical loads.  Also, round cups are offered with cleats for a better gripping power when the load is heavy.  Vacuum Cups with cleats provide extra rigidity that lends itself to heavy loads.  The extra rigidity prevents the cup from peeling away or deforming when a heavy load is required.

Large Round Cleated Vacuum Cup
Round Cup With Cleats

Next we have the Oval Cup, they provide the most gripping power due to their larger surface area.  They naturally lend themselves to heavier loads.  They are ideal for flat rigid sheet materials such as wood, glass, cardboard and composites.

Oval cup
Oval Cups Provide The Most Vacuum Which Make Them Ideal For Heavy Loads Due To Their Larger Contact Area

Last but not least we have the Bellows Cup, they are best suited for curved, uneven or textured surfaces.  The bellows or more accurately called “convolutions”, provide a collapsible area that allows the cup to quickly compress when it contacts the surface of item to be moved.  Please know that the grip/release time is greater due the the larger internal volume of the cup.

bellows cup
Bellows Cup Are Excellent For Uneven Or Textured Surfaces, However They Longer Pick-Up & Release Times

Here is an example: If we want to pick up a sheet of glass that weighs 20 lbs, what size vacuum cup(s) do we need?  Fortunately we have published charts in our catalog with the math already completed, but this is how we arrived at the answer.  Using the formula below:

Cup Diameter Formula

D = Cup Diameter
W = Weight of item
N = Factor of safety ( We recommend a safety factor of 2 for horizontal lifting and 4 for vertical lifting).  For this exercise we will use a safety factor of 4.
U = # of cups (Remember it takes a minimum of 3 points to make a plane)
V = Vacuum level (psi) – Exair Porous E-Vac’s are rated to 21″ HG, Non – Porous 27″ HG and the Adjustable E-Vac 25″ HG.   (Each inch of HG equals .491154 PSI)
π = 3.14159
μ = Vertical surface friction coefficient (.5 for typical non-porous materials such as metal, glass, stone, etc..)

Cup Diameter Formula Solved

The calculated diameter is 2.26″ so we would choose the next standard size which is 2.5″ diameter.

When you are looking for Vacuum Cup application assistance or expert advice on safe, quiet and efficient point of use compressed air products give us a call.   We would enjoy hearing from you!

Russ Bowman, CCASS

Application Engineer
EXAIR Corporation
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