Tag: venturi vacuum generator

In-Line High Vacuum E-Vac Solves Workholding Fixture Problem

Published on by Russ BowmanLeave a comment

Workholding refers to any method of keeping an object in a fixed position while force is exerted onto it. If you’ve ever put something in a clamp or vise to loosen (or tighten) a bolt or screw into it, you’ve performed workholding. In fact, if you’ve ever wrapped a napkin around a cold bottle of your favorite beverage to get a better grip while twisting the cap off, that’s workholding too.

In manufacturing and machining settings, any number of different clamps, fixtures, jigs, chucks, vises, etc., are commonly used for workholding. For efficiency, the main feature of a good workholding device is an easily repeatable setup that can secure the piece quickly, and release it just as quickly. The table of a milling machine, for example, will commonly have t-handle clamps for this.

In addition to mechanically clamping parts, they can also be held in place with vacuum. The basic principle is kind of like an air hockey table, but in reverse: instead of floating the puck on a thin curtain of air being blown out of the holes on the table, it’d be held in place by pulling air back through the holes, to draw a vacuum between the top of the table and the bottom of the puck. Vacuum pump systems can be used for this, but they can get pricey if you don’t already have one (with enough extra capacity) to tie in to. Those pumps have moving parts, so they’re going to need maintenance from time to time as well.

EXAIR E-Vac Vacuum Generators, on the other hand, don’t have any moving parts to wear or electric motors to burn out. They’re compact, they draw rated vacuum as soon as you start supplying compressed air to them, and they drop that vacuum off just as soon as you turn the air off.

For most common workholding applications, we’ll specify an Adjustable E-Vac, for a couple of reasons:

  • Because they’re adjustable, you can quickly dial in different vacuum – and vacuum flow – levels needed to hold parts of different sizes, shapes, and/or weights.
  • They have a large enough throat diameter to pass small amounts of chips or coolant, so the part doesn’t have to be perfectly clean when you place it in the fixture.
The wide throat diameter of the Adjustable E-Vac makes it suitable for applications where small amounts of particulate and/or liquid may be drawn through.

Of course, not EVERY application is a COMMON one…case in point, I had the pleasure of helping a caller from a tool & die company the other day, who wanted to make a fixture to hold a metal block in a V-shaped fixture with two flat surfaces that correspond to the two flat surfaces of the block that won’t be worked on. The idea was to put several holes in each surface, with shallow countersinks for o-rings, so that when the block was set, the o-rings would make a positive seal, and pull vacuum on those holes with an E-Vac. Since there’s a tight seal between the blocks & fixture, and the blocks will be clean & dry, this doesn’t require the chip/coolant passage of an Adjustable E-Vac. And since the cutting & drilling will exert a good amount of force, in several directions, we DO want a high vacuum level to make sure it doesn’t move. At all. No matter what.

For this application, we specified a Model 810023M In-Line High Vacuum E-Vac. It’ll generate 27″Hg worth of vacuum, and in case of any minuscule movement or misalignment of the block, it’ll provide an impressive 2.67 SCFM worth of vacuum flow (to overcome any leakage past the o-rings) and still hold the block in place with 24″Hg.

EXAIR E-Vacs provide instantaneous vacuum response, and are engineered for high efficiency to minimize air consumption.

If you’d like to find out more about EXAIR Vacuum Generators for workholding, pick-and-place material handling, vacuum forming/filling/pressing, or any other application where you need any more than a few inches of mercury worth of vacuum, give me a call.

Russ Bowman, CCASS

Application Engineer
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Adjustable E-Vacs For All Kinds Of Vacuum Applications

Published on by Russ BowmanLeave a comment

EXAIR makes three different engineered compressed air products that are capable of pulling vacuum:

  • Air Amplifiers generate a very high vacuum flow (up to 25 times the compressed air flow rate) but not very much vacuum head. This makes them great for fumes, smoke, and airborne dust.
  • Line Vacs generate a moderate vacuum flow and head so they can easily convey bulk solids.
  • E-Vac Vacuum Generators generate a high vacuum head, but not a lot of vacuum flow. They’re commonly used with Vacuum Cups in pick-and-place applications, or a number of other applications where you measure the required vacuum in inches of mercury (the Air Amplifiers’ and Line Vacs’ vacuum heads are measured in inches of water.)

Our Adjustable E-Vac Vacuum Generators are the ones that typically fall into the “number of other applications” category above. While the In-Line E-Vacs are compact and reliably generate rated vacuum on demand, the Adjustable E-Vacs have some distinct advantages in certain cases:

Larger throat diameter. In-Line E-Vacs have a very tight throat, which generally doesn’t matter if they’re just hooked to Vacuum Cups that’ll be placed on a relatively clean surface. The wider throat of the Adjustable E-Vacs means that they can pass small debris from less-than-pristine surfaces that a Vacuum Cup might lift, or shavings that might fall into a work holding fixture on a machine tool. They can even pass liquids, so they’re sometimes used for small spill cleanup.

Adjustability. It’s right in the name, of course, but it IS a big deal. While you can regulate the supply pressure of almost any compressed air operated device to vary the performance level, you can thread the plug into, or out of, the body of an Adjustable E-Vac to literally put it in a whole new performance band. This is beneficial if you’re picking up, or holding down, pieces of different sizes, shapes, and weights. Just loosen the locking collar, make the adjustment, tighten it back up, and it’s ready for use.

With four distinct models to choose from, we can specify one with the vacuum performance and adjustability of range needed for your application. If you’d like to find out more, give me a call.

Russ Bowman, CCASS

Application Engineer
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E-Vac Porous vs Non-Porous materials

Published on by Al WooffittLeave a comment

EXAIR’s E-Vacs are a great solution for many applications including pick and place, chucking, surface mounting, lifting, and vacuum forming. When selecting which is the right model for you, there are several points you need to consider. Although selecting the right vacuum cup size is important, and knowing the size and weight of the part is necessary, one of the main considerations is evaluating the nature of the material you are working with. Specifically, is the material porous or non-porous?

Porous materials, as the name suggests, have many holes in them. This will allow air to flow through them when trying to pull a vacuum. This can be a challenge when trying to use an E-Vac. To overcome this, you need a high vacuum flow. Non-porous materials, on the other hand, will not allow air to flow through them, so a higher vacuum level can be achieved with a low vacuum flow. If you know which category your material falls into, we can select the correct E-Vac.

Cardboard – Photo by OpenClipart Vectors and licensed by Pixabay

 If you are working with porous materials such as paper, cardboard, or some fabrics, we would recommend one of our vacuum generators that produces a low vacuum level and high vacuum flow. With vacuum levels up to 21” Hg and vacuum flows up to 18.5 SCFM, this style generates more vacuum flow to overcome the porosity and leakage. An additional benefit is that they can also be used to lift or hold delicate materials and prevent any warping or disfiguring of the surface due to excessive vacuum.

Glass – Photo by dflamini and licensed by Pixabay

Alternatively, if your material is non-porous, like glass, steel sheet, or plastic, you will need a generator that produces a high vacuum level with lower vacuum flow. EXAIR’s non-porous high vacuum units can achieve vacuum levels of up to 27” Hg and vacuum flows up to 15.8 SCFM. These vacuum generators offer maximum holding capacity for heavy materials. Sizes are available with compressed air requirements as little as 2.3 SCFM at 80 PSIG and up to 30.8 SCFM for the largest and heaviest materials.

If you would like to talk to an Application Engineer to help you determine the best option for your application, give me a call!

Al Wooffitt
Application Engineer

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How EXAIR Uses Fluidics To Make Efficient, Quiet, and Safe Compressed Air Products

Published on by Russ BowmanLeave a comment

EXAIR Intelligent Compressed Air Products incorporate several distinct principles of fluidics into our engineered designs. To be clear, these principles aren’t exclusive to making quiet and efficient compressed air products. I personally have used them all for business and pleasure over the years. In the Navy, for example, the air ejectors that pulled vacuum on the main condensers where our turbines dumped their ‘used’ steam were basically great big Venturis – they restricted the diameter through which a fluid (steam, in this case) flowed, gradually increased that diameter, and doing so, changed the velocity so that a low pressure area (or vacuum) developed in the throat:

Graphic representation of the Venturi effect.

EXAIR E-Vac Vacuum Generators use the Venturi effect to draw vacuum of up to 27″Hg. They’re typically used with Vacuum Cups for pick-and-place material handling applications.

Here are a few examples of Mr. Venturi’s discovery, implemented in modern industry.

I first learned about the Bernoulli principle on a grade school field trip to the National Air Force Museum at Wright Patterson Air Force Base, about an hour from where I grew up. See, this Bernoulli guy discovered that when there is an increase in the speed of a fluid, a simultaneous decrease in fluid pressure occurs at the same time. That’s why airplane wings are shaped like they are – flat on the bottom and curved on top…when the air flowing that extra distance over the top speeds up to get to the back of the wing as fast as the air that’s simply flowing underneath the wing does, the decrease in pressure on top causes the wing (and the plane it’s attached to) rise in the air.

Bernoulli’s Equation: this is the math that proves it works.

The Bernoulli principle is incorporated in to the design & operation of EXAIR engineered Air Knives, Air Wipes, Air Amplifiers, and Air Nozzles.

The Coanda effect is the third fluidics principle that’s incorporated into the design & operation of many EXAIR engineered compressed air products. Its namesake, Henri Coanda, was an early 20th Century aeronautical engineer who discovered that if a jet of fluid exiting an orifice flows across a surface, it’ll tend to not only adhere to and follow that surface (even if it curves or bends), but also entrain fluid from the surrounding area.

EXAIR Intelligent Compressed Air Products such as (left to right) the Air Wipe, Super Air Knife, Super Air Nozzle, and Air Amplifier all use the Coanda effect to entrain enormous amounts of air from the surrounding environment.

There are a couple of easy – and interesting – experiments that demonstrate the Coanda effect, both of which I used when I was a Cub Scout leader and our Pack’s Webelos den was earning their Science Activity Pin:

Turn a faucet on and let the running water flow over the convex ‘bottom’ of a spoon. Everything we know about the laws of gravity say that when the water reaches the ‘bottom-most’ point on the spoon’s convex surface, it ought to fall straight down…but it doesn’t:

Another experiment that defies everything we think we know about gravity can be performed with a ball, and a source of air flow. Here’s a short video, showing how the air flow from an Air Amplifier ‘wraps’ around a ball and holds it in that jet of air:

The Webelos den did this with a leaf blower and a playground ball. Unlike a lot of things I’ve done, I DEFINITELY encourage you to try THAT at home.

For forty years now, EXAIR has been putting these principles of fluidics into practice by engineering & manufacturing the most efficient, quietest, and safest compressed air products on the market. If you’d like to find out how we can help you get the most out of our products – and your compressed air system – give me a call.

Russ Bowman, CCASS

Application Engineer
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