Compressed Air Super Air Knife vs. Blower-type Air Knife for Plastic Film Manufacturing

A plastic company produced many kinds of films and sheets.  They were having issues with one particular film, an OPS (Polystyrene) film which was 0.012” (300 microns) thick and 30” (762mm) wide.  As the material was extruded into a flat sheet, they would run it over a cold roll drum (Reference photo above).  The cold drum is a large cylinder that has chilled water running through it.  To keep the sheet on the surface of the cold drum, they used a blower air knife system.  With the blower air knife, they were having variation in thickness as well as stretch marks.  They heard about the EXAIR Super Air Knife, and they wanted me to do a comparison.  I was glad to compare the EXAIR 110230 30” Super Air Knife Kit to their blower-type air knife system.

Super Air Knife Kits include a Shim Set, Filter Separator, and Pressure Regulator.
  1. “Stretch” marks on the plastic film:
    • Blower System – Hot air is generated by the blower system. When the hot air hits the cool surface, it would cause an uneven hardening of the material, causing stretch marks.
    • Super Air Knife – It has a 40:1 amplification ratio. That means that 40 parts of the ambient air is entrained with 1 part of compressed air.  Being that the ambient air is much cooler than the hot air from the blower system, it actually aides in cooling.  There is no thermal shock to the sheet material, and hardening is consistent and faster.
  2. An even force across the plastic film:
    • Blower System – Their design had one 4” (102mm) line feeding into the side of the blower air knife. This would cause two issues for an even force.  As the velocity of the air hits the opposite side of the knife, the closed end, a turbulent air flow is developed.  Also, there would be a slight negative pressures at the entrance caused by the velocity of the air entering.  This chaotic turbulent flow caused an uneven force on the surface of the film.
    • Super Air Knife – The flow that is delivered from the Super Air Knife is laminar. This means that the force and velocity is consistent across the entire length, even on the target.  With this even force, the film was held evenly and securely on the cold drum.  With a filter, shim set, and regulator that is included in the kit, the force can be easily adjusted to the perfect requirement.
  3. Maintenance requirements:
    • Blower System – Preventative maintenance is a requirement. The blower filters have to be changed regularly, and the mechanical and electrical components have to be checked.  This requires downtime to the system.  In addition to this, blower motors are mechanical devices.  The bearings will wear and the motor will fail.  If a mechanical failure does occur, the downtime can cost days of operation.  These items should be checked quarterly as a PM which increases the cost of ownership.
    • Super Air Knife – No moving parts to wear out. The only maintenance would be to change the compressed air filter once a year.  There is no worry about catastrophic failure.
  4. Noise levels:
    • Blower System – With the blower motor and turbulent air flow, the system makes a lot of noise. They have a sound level near 93 dBA which would need PPE for nearby operators.
    • Super Air Knife – These units are very quiet. At a pressure of 100 PSIG (6.9 bar), the sound level is only 72 dBA.  No additional cost for PPE or the constant nagging disturbance of loud noises.
  5. Compact Design:
    • Blower System – The foot print of the blower is large and it takes up much floor space. The 4” (102mm) duct has to be ran to an oversized air knife (Reference photo below).  With the turbulent flow, the blower air knife has to be mounted close to the film surface.  So, it can make it difficult to optimize the placement.
    • Super Air Knife – With the compact design, the Super Air Knife has a large force in a small package. The model 110230 Super Air Knife has a footprint of 1 ¾” X 1 ½” X 30” long (44 X 38 X 762mm respectively) with only two ¼” NPT compressed air lines feeding it.  The force measurement is the same from 3” (76mm) to 12” (305mm) away from the surface; giving flexibility in placement.

When it comes to using the EXAIR Super Air Knives, it has many benefits over the blower-type air knives.  We can even include the initial purchase price in which the Super Air Knife would be about 1/10 the cost, and the company was able to increase production with a cooler blowing device.  They were delighted to remove the large blower-type system and replace it with a simple Super Air Knife.  If you would like to discuss the advantages of the Super Air Knife against a blower system, an EXAIR Application Engineer will be happy to assist.

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

Video Blog: Selecting the Right Air Knife

The following short video explains the differences between the three styles of Air Knives offered by EXAIR – The SuperStandard and Full-Flow

Please reach out to myself or one of our application engineers if you need help figuring which Air knife suits your application best!

Jordan Shouse
Application Engineer

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Find us on the Web 
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Twitter: @EXAIR_JS

 

Super Air Wipe Provides Long-Lasting Solution for Extrusion Blowoff Application

 

The Super Air Wipe has no moving parts to wear out requiring little to no maintenance when supplied with clean, dry compressed air. I recently spoke with a maintenance manager who worked for a company that had been using the same unit for over 7 years. In this application, the Super Air Wipe was used to remove a light coating of oil from the exterior of extruded shapes. Despite showing some obvious signs of wear and tear (and perhaps a little bit of residual oil from the environment), it was still serving the needs of the application as-is.

It may be dirty, but it is still working to remove a light coating of oil from an extrusion!

The Super Air Wipe is available in aluminum construction in sizes ranging from 3/8” – 11” in diameters. All Super Air Wipes comes with stainless steel hardware and stainless steel shims. Sizes up to 4” include a brass tee that supplies one half of the Super Air Wipe while a stainless steel wire braided hose supplies the other side. Sizes over 4” should be piped directly to each ¼ NPT compressed air inlet. In addition to aluminum construction, the Super Air Wipe is also available in 303 stainless steel for corrosive or high temperature applications. The Stainless Steel Super Air Wipe can withstand temperatures up to 800°F and is available in sizes from ½”-4” from stock.

Much like the Super Air Knife, the Super Air Wipe has ¼-20 tapped holes along the downstream side that can be used for mounting. Smaller Super Air Wipes can be supported by rigid compressed air pipe that is used to supply the air into the product. The Super Air Wipe is also infinitely adjustable through the use of shim sets or a pressure regulator. Kits will include the Super Air Wipe, shim set to make gross adjustments to the airflow, an auto-drain filter to keep the air clean and dry, and a pressure regulator. By adjusting the input supply pressure to the Super Air Wipe, you regulate both the force and flow that is projected onto the target material. Increasing the input supply pressure will increase both the force and flow from the Super Air Wipe.

If you’re processing any type of hose, wire, or extruded shapes that could benefit from installing a Super Air Wipe give us a call. With all sizes shipping from stock on an order received by 2:00 pm ET we can have one to you as early as tomorrow!

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

Customize Air Knives Specific to Your Application!

EXAIR’s Super Air Knife utilizes a source of compressed air to create a laminar sheet of high velocity air. This supplied compressed air mixes with ambient air that is entrained into the primary airstream. The Super Air Knife entrains ambient air at a rate of 40:1, making it VERY effective in a variety of drying, cleaning, and cooling applications. Available in lengths ranging from 3”-108” and in a variety of different materials of construction, there’s a Super Air Knife available for just about any application. Any time you have product moving along a conveyor that needs to be cleaned, dried, or cooled off, a Super Air Knife is the ideal fit.

The Super Air Knife is available in aluminum, Type 303 & Type 316 stainless steel, as well as in PVDF with Hastelloy bolts for extremely corrosive applications.  While there are numerous options available off the shelf ready to ship same day, not all applications can be served by a stock option. Since EXAIR handles all of the manufacturing of these products in our sole facility in Cincinnati, Ohio, we have a great deal of control over the manufacturing process. If your application cannot accept something right off the shelf, we’re constantly producing special customized knives to fit any requirement.

Any of our knives can be manufactured in a special length if a stock length won’t fit in your application. We’ll use the same design and profile and can build it to the precise length you require in order to fit perfectly onto your machine. If the dimensional profile of an existing knife isn’t suitable, we can change that too! The Super Air Knife shown below utilizes a very thin design and has been completely modified to achieve the thinnest overall profile possible.

All Super Air Knives come stock with ¼ NPT air inlets and ¼-20 tapped holes along the bottom that can be used for mounting. Unfortunately, that isn’t always going to work for every application, so we also manufacture specials with custom air inlets as well as additional mounting holes to fit right onto any custom bracket. The photo below shows a modified stainless steel Super Air Knife with additional mounting holes machined onto the end.

We don’t just offer them in different shapes and sizes as a special, but we’ve also manufactured stock length knives out of entirely different materials. Shown below are two knives of different materials that aren’t already on the shelf. On top is a knife manufactured from PVC and on the bottom a glass filled PEEK material with brass hardware and a PTFE shim. In this application, the customer was noticing ground interference due to the aluminum knife construction. They specified this particular material and we were able to machine a knife completely customized for this application.
Each and every year new requests come across that is something we haven’t done before. Just because you don’t see it in the catalog doesn’t mean it isn’t possible when you deal with EXAIR. We’re here to make sure you get the most out of our products, and sometimes custom features or materials are necessary to get that accomplished. Contact an Application Engineer today if you’d like to discuss your application and begin the process of identifying your next custom solution!

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