Solving a Printing Problem with EXAIR Static Eliminators

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Unrolling plastic into this machine created a static charge throughout the process

One of the most common sources of static electricity in automated processes is friction.  As two (or more) materials move against each other, static is produced due to the triboelectric effect.  By definition, the triboelectric effect is a type of contact electrification in which certain materials become electrically charged after they come into frictional contact with a different material.  If these materials are non-conductive, or if they are not grounded, the static charge will remain.  This was the case for the machine shown above.

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Multiple stations of this machine, all experiencing static problems

This machine is a Chesnut 150 Gravure Print Station.  It is used for printing, coating, laminating, and sometimes die cutting of paper, light paperboard, films, polyester, flexible packaging and aluminum foil.

In this application, a roll of plastic is dispensed, but a static charge is preventing proper printing on the plastic as it travels from roll to roll.  As the film is separated from the roll, a static charge is produced, and this charge is carried through the process at values ranging from 3,000 – 20,000 volts.  The manager for this production area contacted EXAIR to see if there’s a viable EXAIR solution to remove this static charge.  They were interested in a solution that could eliminate static on the full width of the plastic, could be mounted 200-300mm away from the rollers, and could be replicated at multiple places along the machine.

With this in mind, the best solution was to use a series of 18” Super Ion Air Knives installed periodically along the path of plastic within the machine.  Operating at a low pressure of 1-2 BARG (14.5 – 29 PSIG), the Super Ion Air Knives create an evenly dispersed, quiet airflow of static eliminating ions with a low compressed air consumption.  Using the laminar, static eliminating airflow from the Super Ion Air Knife, this solution can be mounted away from the static charge, allowing the ions to “rain” down on the affected areas.

For this application finding a solution meant finding a method to keep production on schedule.  Without static elimination this machine faced defects, downtime, and decreased efficiency.  Using EXAIR Super Ion Air Knives brought this application back up to optimal operating speeds, keeping the revenue generating process of this manufacturer ongoing.

Colder weather is here and static comes along with it.  If you’re experiencing a static related problem in your facility, contact one of our Application Engineers.  We’d love to help you find a solution.

Lee Evans
Application Engineer
LeeEvans@EXAIR.com
@EXAIR_LE

Static Eliminators Solve Printing Quality Issues

One of the big issues in winter many manufacturing and process industries experience is static.  An outside sales rep who was responsible for selling and servicing industrial laser printers contacted us after he started to receive more complaints about the quality of the print, especially with customers that used polyester sheets.  One of their customers was printing both sides of a 13” X 19” (33 X 48 cm) sheet, and they noticed that the print on the back side was blurry.  We discussed how static can cause issues like this in printing applications. A static charge can keep ink from landing in the proper location, it can cause ink to spiderweb, spread over defined boundaries or fail to penetrate its target.

Ionizing Bar

Low cost Ionizing Bars eliminate static cling.

Being that EXAIR Corporation is a leader in production and application of active Static Eliminators, we were able to discuss the issues and suggest some possible solutions. Laser printers are designed to use static to pick up toner onto a drum and to apply it to sheets of paper.  If the sheet of paper has a charge on it, that can affect the print quality because like charges repel each other.  In this application, we have two conditions that contributed to the increase in static charge on the polyester sheet, the dry air and the type of material.  Dry air in winter is pretty much a given as cold air cannot hold as much moisture as hot air can.  With a decrease in moisture levels, static fields can build to much higher levels causing discharges, the small “shocks” you experience when you touch a non-conductive material, another person or even a grounded machine.  The other static issue is material.  The type of materials involved in an application determine how they will share electrons when they rub together.  Some materials give up electrons readily and some materials tend to gain electrons.

Getting back to the application; inside the mentioned printer, a rubber roll was used to invert the paper to print on the back side.  If the paper was cellulose, it is harder to generate static as the rubber roll and cellulose are similar in sharing electrons. However, this sheet was made of polyester, it has a higher affinity to take electrons from the rubber roll. A static field would build which was enough to affect the transfer of toner from the drum causing a blurred image.

Our strategy for applying static elimination solutions is to determine the point of static generation and locate the static elimination equipment just downstream of the problem area.  In this instance, it was after the roller just before printing. The space was limited, so the customer went with model 7012 Ionizing bar with the 7901 power supply.  The positive and negative ions that are emitted from the Ionizing Bar will neutralize static fields of positive or negative polarity bringing the surface of the polyester material back to neutral.  The length of the bar was slightly shorter than the width of the sheet, however it still has plenty of capacity to neutralize the outside edges.  The end user mounted the Ionizing Bar in the center of the sheet about 0.5” (13mm) away from the surface.  After he plugged in the Ionization Bar, the static field was removed and the printing on the back side was now clear.  The end user was so impressed that he contacted the manufacturer of the laser printer to suggest they add effective static elimination as  an option for troublesome applications like his.

If you have static issues and you want to remove the pain they cause in the form of injury, lost production time and material waste, contact EXAIR and speak to one of our experienced Application Engineers.

John Ball, Application Engineer
E-mail: johnball@exair.com
Twitter: @EXAIR_jb

Cleaning A Super Air Knife? Know Your Materials.

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An Aluminum Super Air Knife, disassembled and showing how a clean unit should look

While having dinner with some friends a few days ago, another engineer in the room asked what I did for a living and where I work.  When I told them I work for EXAIR, they immediately knew the name and commented on our Super Air Knives.  This gentleman was an automation engineer and has used our Super Air Knives for automated blow off.

The ability to automate and control an instantaneous blow off makes the Super Air Knife a versatile tool in an automation application.  But, how do they stand up to cleaning over time?

The answer, is that when properly configured for the application a Super Air Knife can last indefinitely.  If the temperatures are below 82C (180F) and there is no caustic chemical used for wash-down, an aluminum knife can usually fit the bill.  But, when a caustic chemical is to be used for wash-down, a stainless steel knife, or specially configured aluminum knife must be used.

This advice was not heeded by one of our overseas customers, and the results of what happens over time are shown below.

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Polyester shim of an aluminum Super Air Knife after the unit was cleaned with Sea Foam

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Cap of an aluminum Super Air Knife after the unit was cleaned with Sea Foam

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Body and cap of an aluminum Super Air Knife showing the results of improper cleaning

This customer coated the exterior of an aluminum Super Air Knife with a product by the name of Sea Foam.  The surfaces and air slot of the knife were completely covered with Sea Foam, and then the exterior was wiped down.  Over time, the Sea Foam entered into the plenum chamber of the knife and caused the polyester shim to deteriorate.

Sea Foam is a wonderful product that has found a home in many shops and maintenance departments, and for many applications it presents an excellent cleaning agent.  But, for an Aluminum Super Air Knife, it poses a problem.  But why?

Sea Foam is a combination of Isopropyl Alcohol (10%-20%), Naphtha (25%-35%), and Pale Oil (40%-60%).  Isopropyl alcohol is a solvent, naphtha is petroleum distillate that is highly flammable, and Pale Oil is a heavy distillate naphthenic oil refined from wax-free crude oil.  These characteristics make the product a “go-to” cleaner for carbon/dirt buildup, especially on metal surfaces.  But, these same characteristics are “bad news” for polyester (Aluminum Super Air Knifes use polyester shims), and over time will cause the polyester to break down (as shown in the photos above).

So, what is the solution?  First and foremost, the solution is to follow the cleaning instructions found in our Installation and Maintenance (I&M) guide.  We provide an I&M guide with every product we sell, and have free downloads available on our site here.  But, to remedy the current condition in this application we recommended one of two actions.  The first is to use a Stainless Steel Super Air Knife which will be able to handle Sea Foam.  And, the second is to make a stainless steel shim for this aluminum knife made of 0.002″ stainless steel shim stock.  Either of these solutions will not only correct the present condition, but will prevent such a problem from occurring in the future.

For our end user in this case, a short, thorough discussion with an EXAIR Application Engineer could have saved them downtime and headache.  If you have an application involving EXAIR products, never hesitate to give us a call.

Lee Evans
Application Engineer
LeeEvans@EXAIR.com
@EXAIR_LE

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