If you want to print on plastic, it’s challenging – most plastics are chemically inert and non-porous. That means you can apply all the ink you want; it’s not going to stick. In the 1950’s, a Danish engineer named Verner Eisby experimented with various techniques to overcome these challenges. He found that exposing the surface to be printed on to gas flame or sparks modified the surface to improve adhesion with the ink. It did so, though, in a crude & uneven manner, leaving imperfections & inconsistencies in the printed product. He then tried applying a high frequency corona discharge in a linear array. The plasma (gas in an ionized state) generated left a homogeneously treated surface on which to print, smoothly & evenly.
This has become the “industry standard” for many of the labels we see on commercial products, from shampoo & wine bottles on the grocery store shelf, to pennants & banners at public events. It also leaves the surface even more prone to picking up a static charge from rolling or unrolling, stacking, sliding, etc.
One of our customers makes a great many labels for all kinds of these commercial products, and uses an EXAIR Gen4 Ionizing Bar immediately prior to the printing operation:
A company that made credit cards was having issues in their print quality, and static was the culprit. They used PVC sheets as a base material to print on, and like with any non-conductive materials, static can be generated easily and create problems. For this company, static was attracting dirt to the surface of the material, causing blemishes in the print. They contacted EXAIR to find a solution.
When non-conductive materials slide, hit, peel, and rub; electrons from the surface can move from one atom to another; thus, creating static. The type of material and the amount of movement governs the amount of static forces. These strong static forces can attack debris and fibers, as well as generate shocks, misalignment, and machine jamming. Another feature of static is that it can regenerate if the materials continue to slide, hit, peel, and rub.
For the company above, they were printing on 30 cm by 48 cm (12” X 19”) PVC sheets. They used three different processes to print a complete credit card; silkscreen, digital, and offset. After each printing process, they would lose sections of the sheet due to poor image quality. At the end, they were losing between 20 to 30% in visual rejections.
For this application, we had to do two operations; remove the static and clean the surface from debris. The Gen4 Super Ion Air Knife can do both of these operations at the same time. With the laminar air stream that comes from the Super Air Knife, it can carry both positive and negative ions from the attached Gen4 Ionizing Bar. Together, they can remove any type of static charge as well as becoming a very effective tool as a non-contact wiper to remove debris. With this ability, the print quality would not be affected during cleaning. Since static is a surface phenomenon, I recommended to also remove the static from the other side of the sheets. We did not want to have any dirt or debris that could be remaining on the bottom surface to transfer from one surface to the next during stacking. This could scrape the finish during loading and unloading of the sheets.
I recommended two pieces of a model 112012 Gen4 Super Ion Air Knives that are manufactured to 12” (30 cm) in length. This customer can easily mount one above the sheet and one below the sheet prior to printing. To operate the attached Gen4 Ionizing Bar, EXAIR offers two types of power supplies, a two-output unit, model 7960, and a four-output unit, model 7961. They can save you money when needing multiple Static Eliminators to operate in your system. With a model 7960 Gen4 Power Supply, they now had a system to remove static and clean the sheets. Once they installed the Gen4 Super Ion Air Knives onto their system, the rejection rate dropped to near zero.
Rejected parts are costly, wasteful, and reduce production rates. If you have rejection from static problems in your system, EXAIR has a large line of Static Eliminators to help you. You can contact an Application Engineer to review your application. For the customer above, the Gen4 Super Ion Air Knives made it possible to generate more credit cards per sheet.
I feel like I blog about this frequently, but this time it’s different I promise. With technology and information moving faster and faster every day it is very easy to request information be sent to you and expect it to reach you immediately. Some of us, including myself, prefer to have a good old fashion print catalog. A picture of my EXAIR Catalog 24 is below.
I know I use my catalog every day with almost every single customer I talk to. I’m one of those people that have all our information at the click of the mouse but when it comes to looking something up I rely on the print catalog. I know where the new products have been placed in the PDF files and so in my mind they are there.
If you are one of those people then you probably do just like I do. If I am looking for something on the internet I request a catalog from whatever site I’m on that offers it. What surprises me is how long it takes to get some of the catalogs. I requested a catalog from a well known wood working supply house over three weeks ago and still have yet to see the catalog.
Here at EXAIR if you request a print catalog we will ship it out same day. Not only will we send it out same day, we will send it out Priority Mail that day. This goes hand in hand with all of our stock product; if you place an order by 3:30 pm EST and we are shipping within the states, then we will ship your order that same day. If you want a catalog we can even throw that in there too!
If you aren’t like me and you like to have the most up to date electronic version of a catalog then hop on our website and download the PDF files for free. We even have an entire section optimized for E-Readers and iPads. We do ask you to register for the downloads, but it is a one time thing which gets you access to our application database, CAD Library, and catalog files.