Super Air Knife to the Rescue in Machining

Home-made blow-off device

As machined parts require tighter tolerances, the surface has to stay clear during turning operations.  A customer that had a CNC machine needed to make a metal tube with a specific diameter.  The metal tube was 17 ½” (445mm) long.  They made their own blow-off “tree” to keep the surface clean from shavings.  They used five open ports to blow at the part surface (reference photo above).  When they started using their home-made device, they were not getting a consistent cleaning during operation.  They wanted to speak to an expert in this type of area, and they contacted EXAIR to see if we could improve their process.

With a series of open nozzles, it is very difficult to get a consistent force along a linear line.  The air becomes very turbulent, which has changing directions of air flow.  It creates a hazardous noise exposure to the operators, and it also wastes compressed air which costs the company a large amount of money to use.  With laminar air, the path flows in the same direction.  This creates a very consistent force with less noise.  Since air is invisible, I like to use water to show the difference.  The photo below shows turbulent and laminar flows. 

Turbulent to Laminar Water

For linear blow-offs, EXAIR offers a wide range of Super Air Knives.  They give a laminar flow pattern along the entire length.  We have stocked lengths from 3” (76mm) up to 108” (2.74 meters) in different materials.  A benefit of the Super Air Knife is the high amplification ratio of 40:1.  This means that for every 1 part of compressed air, it will entrain 40 parts of ambient air.  So, they are very efficient, safe, and effective.  For the application above, I recommended the model 110218 18” Super Air Knife Kit to cover the length of the metal tube.  It has an 18” (457mm) wide air stream that is very powerful to remove chips during the turning operation.  The kit includes a filter, regulator, and shim set.  The filter will remove contaminants from the compressed air system to keep the surface clean.  The shim set and regulator provide the ability to adjust the air to the ideal force level to remove the debris from the surface of the tube. 

Super Air Knife Kits include a Shim Set, Filter Separator, and Pressure Regulator.

One of the biggest attributes that the EXAIR Super Air Knives can offer is that they use much less compressed air than a series of open nozzles. With the engineered design, it can entrain large amounts of ambient air which means that less compressed air is required.  For the nozzle tree, it was using 105 SCFM of air at 80 PSIG.  The model 110218 only requires 52.2 SCFM at 80 PSIG. That is a difference of 52.8 SCFM; half the amount of compressed air as the home-made nozzles. 

Once they installed the Super Air Knife, the first thing that they noticed was the reduction of noise. The model 110218 Super Air Knife only has a noise level of 69 dBA at 80 PSIG, compared to a noise level of an open port which was over 100 dBA. By replacing the nozzle tree with the Super Air Knife, this company…

1. reduced air consumption

2. saved money

3. reduced noise levels

4. increased the effective blowing force

If you find yourself using a home-made blow-off device, you can be creating a hazardous, costly, ineffective method to “do a job”.  Since precision was needed for the company above, they were delighted to contact an expert in this area.  You can also improve your blow-off device by contacting an Application Engineer at EXAIR for assistance.  We would be glad to help. 

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb

Laminar Flow vs Turbulent Flow for Compressed Air Blowoff

You’ll often hear us refer to laminar vs turbulent flow when discussing our blowoff products. In any blowoff process or application, laminar airflow is going to be much more effective at cooling or drying than the turbulent airflow delivered by commonly found homemade blowoff devices or cheap knockoffs. To read more about the math behind it, check out my colleague John Ball’s previous post here.

Allow me to use the Super Air Knife to help illustrate the benefit of laminar vs turbulent flow. When a wide, even, laminar flow is necessary there isn’t a better option available on the market than EXAIR’s Super Air Knife. What really sets EXAIR’s Super Air Knife above the competition is the ability to maintain a consistent laminar flow across the full length of the knife compared to similar compressed air operated knives. This is even more evident when compared against blower operated knives or fans. A fan “slaps” the air, resulting in a turbulent airflow where the airflow particles are irregular and will interfere with each other. A laminar airflow, by contrast, will maintain smooth paths that will never interfere with one another.

visual representation of a turbulent flow on top and laminar flow on bottom

The effectiveness of a laminar airflow vs turbulent airflow is particularly evident in the case of a cooling application for automotive computers coming out of a wave soldering machine. The chart below shows the time to cool computers to ambient temperatures for an automotive electronics manufacturer. They used a total of (32) 6” axial fans, (16) across the top and (16) across the bottom as the computers traveled along a conveyor. The computers needed to be cooled down before they could begin the testing process. By replacing the fans with just (3) Model 110012 Super Air Knives at a pressure of just 40 psig, the computers were cooled from 194°F down to 81° in just 90 seconds. The fans, even after 300 seconds still couldn’t remove enough heat to allow them to test.

While the fans no doubt made for large volume air movement, the laminar flow of the Super Air Knife resulted in a much faster heat transfer rate.

Utilizing a laminar airflow is also critical when the airflow is being used to carry static eliminating ions further to the surface. Static charges can be both positive or negative. In order to eliminate them, we need to deliver an ion of the opposite charge to neutralize it. Since opposite charges attract, having a product that produces a laminar airflow to carry the ions makes the net effect much more effective. As you can see from the graphic above showing a turbulent airflow pattern vs a laminar one, a turbulent airflow is going to cause these ions to come into contact with one another. This neutralizes them before they’re even delivered to the surface needing to be treated. With a product such as the Super Ion Air Knife, we’re using a laminar airflow pattern to deliver the positive and negative ions. Since the flow is laminar, the total quantity of ions that we’re able to deliver to the surface of the material is greater. This allows the charge to be neutralized quickly, rather than having to sit and “dwell” under the ionized airflow.

With lengths from 3”-108” and (4) four different materials all available from stock, EXAIR has the right Super Air Knife for your application. In addition to shipping from stock, it’ll also come backed up by our unconditional 30-day guarantee. Test one out for yourself to see just how effective the Super Air Knife is on a wide variety of cooling, cleaning, or drying applications.

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

Understanding Air Entrainment or Amplification Ratios and Air Knives

Super Air Knife has 40:1 Amplification Ratio, entrainment is illustrated as the curved blue arrows.

EXAIR’s Super Air Knife is the top performer among our engineered air knives and it dramatically reduces compressed air usage and noise when compared to other blow-off systems. The Super Air Knife delivers a uniform sheet of laminar airflow across the entire length of the air knife. Even at high pressure of 80 PSIG (5.5 BAR), the sound level is surprisingly quiet at 69 dBA for most applications.

One feature of the Super Air Knife is its Amplification Ratio, or the ratio of ambient air to compressed air within the forceful blast of air from the Super Air Knife. The design of the Super Air Knife entrains ambient air at an amplification ratio of 40:1 (ambient air to compressed air). Entrainment is defined in the simplest of terms as: to draw in and transport (something, such as solid particles or gas) by the flow of a fluid. The Super Air Knife design produces two low pressure areas where surrounding air is pulled into the primary compressed air stream and is delivered to your target. EXAIR’s Intelligent Compressed Air® products use the principle of entrainment to give you more air volume than just the compressed air being introduced from your air compressor.  This will maximize the force value for your application with the minimum amount of compressed air. Any pipe, manifold, or fitting can be modified to blow compressed air, however, these homemade blow offs will be very noisy and perform poorly when it comes to air entrainment, or amplification ratios. In contrast EXAIR’s intelligent compressed air solutions are engineered to be very quiet and use conservative amount’s of compressed air while maximizing the output volume through entrainment. 

Furthermore, the table below demonstrates the differences between blow-off systems and the efficiency of EXAIR’s Super Air Knife. You can see that the Super Air Knife outperforms all or most other options when comparing purchase price, sound level, maintenance, horsepower required and electrical costs.

The use of EXAIR’s Super Air knife not only save air consumption but you can notice the lower decibel rating which meets or exceeds OSHA Standard 29 CFR-1910.95(a) for maximum allowable noise exposure. If you have questions or need help with EXAIR’s Super Air Knife or any of our Intelligent Compressed Air Products please contact us and let us help you.

Eric Kuhnash
Application Engineer
E-mail: EricKuhnash@exair.com
Twitter: Twitter: @EXAIR_EK

Adjust Force and Air Consumption with Super Air Knife Shim Sets

EXAIR’s industry leading Super Air Knife dramatically reduces compressed air usage and noise when compared to other blowoff methods. The Super Air Knife is available in lengths ranging from 3”-108” and in Aluminum, 303 Stainless Steel, 316 Stainless Steel, and PVDF for corrosive applications. Even at high pressures of 80 psig, the Super Air Knife is able to maintain a sound level of just 69 dBA for most applications! Air is entrained from the ambient environment at a rate of 40:1, maximizing the force and flow from the Super Air Knife. In addition, these knives meet or exceed OSHA maximum dead-end pressure and noise requirements.

completeAirknifesets
From left to right – plastic shims, SS shims, PTFE shims.

Adjustability of both the force and flow from the Super Air Knife has a huge range of adjustability. Right out of the box from the factory the Super Air Knife comes stock with a .002” thick shim installed. This sets the gap between the body and cap of the knife and determines how much compressed air can flow through the precise, slotted orifice. An accessory that EXAIR has available for the Super Air Knife is the shim set. For the aluminum knives, a .001”, .003”, and .004” plastic shims come in the shim set. To reduce the flow and force, a .001” can be used. If more force is required, a thicker shim can be installed. For the stainless steel and PVDF knives, (3) .002” shims are included in the set. Stainless steel shims for the stainless knives and a PTFE shim for the PVDF. These, as well as the plastic shims, can be stacked on top of one another to create an even larger gap. One thing that is important to keep in mind however, the larger the air gap the greater the air consumption. Installing a .004” shim in a Super Air Knife will double the flow and consumption of the knife when compared to the stock .002” shim.

Installing a new shim in your Super Air Knife is very simple to do. Check out this quick video from Neal Raker that walks you through the steps:

While the different shims are available for you to make gross adjustments to the force and flow of your Super Air Knife, there is one additional method. By using a pressure regulator, you can fine-tune the input pressure that is supplied to the Super Air Knife. This will also greatly impact the force and flow. At 40 psig, the Super Air Knife will consume 1.7 scfm/inch and provide 1.1 oz/inch of force. At 80 psig, it will consume 2.9 scfm/inch and provide 2.5 oz/inch of force. EXAIR offers pressure regulators in a variety of different sizes to accommodate any of our Super Air Knives from 3” all the way up to 108”.

If you’re wasting air in your facility using cheap nozzles, drilled pipes, or any other inefficient solution give us a call. An Application Engineer will gladly investigate your application and help to design a better, safer, and more cost-effective solution!

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