Super Air Knife Shims & How They Affect Performance

To Shim or not to Shim… The Super Air Knife is a fabulous piece of equipment. Between the quiet laminar flow of air, and the intense 40 to 1 ratio of entraining the ambient air around it, this Knife is definitely cutting edge (pun intended). As you look at the front edge of the Super Air Knife, or as we call it “the place where the magic happens”, you will see that there is a very small slit or gap where the air flows. The gap in that metal is caused by the shim that is inside the Super Air Knife. We control the size of this gap with shims. Hark, what light through yonder air gap breaks?… Sorry, I get carried away sometimes.

The shims in the Aluminum Super Air Knives are made of a polyester plastic, the PVDF Super Air Knife Shims are made of PTFE, and I will give you two guesses what the Stainless Steel Super Air Knife Shims are made of, you guessed it… Flubber… Just kidding, they are stainless steel of course.

All of our Super Air Knives, regardless of material, ship standard with a 2 thou shim installed. 2 thou you ask? I did too. That is 2 thousandths of an inch, or 0.002″. This is the height of the gap where the Air Flows out. When you are looking at all of our published numbers in the catalogue or on the website, all of those performance numbers are based on this 2 thou shim. Here is the Super Air Knife performance table:

Pic by Conmongt, licensed by Pixabay

So, what if you need more or less air than what’s on this list? We can adjust the gap. We can add shims up to @ 0.01″ to increase the flow. Or we can go down to 0.001″ (1 thou). This poses the question of, what happens to performance? The good news with the shims is that the Air Consumption is a direct linear proportion to this performance table, and the force is very close to the same. So if you double to a 4 thou shim, you double the air consumption and force. Velocity and sound level will vary, but I do not have data to what degree.

As we size these, generally see people wanting more air, larger gaps (more shims), But conversely, we can decrease the air flow down to a 1 thou shim (1/2 of the published values above). Technically we can go smaller than 1 thou, but there is a limit to where a hole is no longer a hole. Here is a breakdown of our stock shims, with colors and sizes for the Super Air Knives:

The Super Air Knives are in a class of their own. As long as you feed the Super Air Knives enough air (SCFM) you can run them at most any psig to retrieve the desired air flow for you application. As an added means of flexibility, you can change the gap size with shims. I have put in a request to change the name of these to Super Flexible Air Knives, but I’m not holding my breath.

Public Domain Picture Licensed by Pixabay

One more thing about Shims. We can customize your shims!! Now I am not talking about putting your logo on them (but money talks!!), but we can customize your length. Let me give you an example. Let’s say that you need 58″ of airflow, no more no less. Our standard length Super Air Knives are 54″ and 60″. We can make you a custom knife, which is a great option, but for 1 or 2, this is probably not very cost-effective. But we can make you a custom shim. We can have the knife only push 58″ of air with a shim blocking the rest. Furthermore, you can decide if you want 58″ centered on the knife, or all 58″ starting from the left, or right side. It is a very cost-effective way to get a custom flow width.

Please let me know of you have any questions, or would like to discuss any of this further.

Thank you for stopping by,

Brian Wages

Application Engineer

EXAIR Corporation
Visit us on the Web
Follow me on Twitter

Custom Shims – Literally A Breeze For EXAIR

As proud as we are of being able to ship most any catalog product, same day, from stock (99.9831% of the time for on-time shipping in 2017…22 years straight for 99.9% or better,) we take a certain amount of pride in our ability to offer custom solutions for challenging applications as well. Our Engineering and Production teams have a deep well of resources (knowledge, experience, and capability) to draw from, which allows us to meet those challenging applications head-on, in short order.

The one I’m writing about today isn’t exactly one of those challenging ones…

A machine fabricator had a special need for an Air Knife. It had to be Stainless Steel, and it had to be 30″ long. No problem so far…that’s a Model 110030SS 30″ Stainless Steel Air Knife, and it’s on the shelf. Thing is, they only needed 26″ worth of air flow; a full 30″ width was going to disturb, and maybe damage, the edges of the sheet of material that the air was being blown onto.

So we made a custom shim for the Air Knife.  Now, we make these all the time, in all kinds of configurations…hence the term “custom.”  Since this one was blowing onto a web where they didn’t want to disturb the material on the far edges, we made this shim to provide 26″ of flow, on center.  We could just as easily made it to provide 26″ of flow starting at one end or the other, or a specified distance from one end or the other.  Or 13″ of flow on both ends, with 4″ of no flow in the middle, for a total of 26″.

If your application is more challenging than a custom shim, we’ve also made Air Knives with (left to right) curved radius, special material (glass filled PEEK shown here,) flat, double-sided, and even one with end-mount threaded holes.

Regardless of how challenging (or not) your compressed air product application is, we’re here to discuss, any time you’re ready.  Call us.