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Curing on a flexo press: UV, LED or nitrogen?


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This is a guest blog from Marcus Greenbrook, Director International Sales of GEW.Marcus Greenbrook GEW

GEW has been in the UV curing industry since 1991 and has been extremely successful in narrow web. We have headquarters based in South East England, with offices in Germany, USA and a global network of distributors.

I started at GEW in September 1998 and have just celebrated 20 years. I started as a Service Technician carrying out installation and service work all over the world before moving into the Service Office taking calls from customers and arranging the Service Technicians work. I then became the Service Manager. In 2004 I moved into Technical Sales, before moving to Australia to head up our Sales and Service Department to support our customers. On returning to the UK in 2009, I became the International Sales Manager. In July 2017, I was promoted to Director, International Sales.

UV, UV LED or specialised applications?

GEW’s core business is in narrow web flexo presses, but over the years we have found that the narrow web is becoming wider and, in some cases, moving into the mid web range. We offer both traditional UV arc and UV LED for this industry as well as specialised applications such as inert gas curing.

We also supply UV systems onto wide web applications such as coating lines, of which we have supplied our longest system to date which is 2.5 metres. With the onset of our UV LED system, this has allowed us to enter other applications such as sheetfed offset.

GEW UV led dryer on MPS EF flexo press

GEW LED curing solution on an MPS EF flexo press

Reducing oxygen: N2 Nitrogen drying

Oxygen reduces the effectiveness of UV curing in some inks and coatings. Reducing the oxygen level within the UV curing area (or chamber) by introducing an inert gas, typically nitrogen, increases the curing performance which then allows an increase in production speeds to be achieved. Our system can reduce the PPM (Parts Per Million) level of oxygen to under 1000, and in some cases as low as 50PPM, depending on the application.

MPS customer Milkpack already uses these nitrogen dryers from GEW. Read more here.

The N2 Nitrogen drying system is more of a specialised system that requires additional equipment that is integrated into the conventional UV lamphead and control system, such as:-

  • A water chill roller – The UV lamphead and inert chamber must be mounted to a water-cooled chill roller as this better controls the movement of the web and allows for smaller gaps on the inlet and outlet of the web, so as not to drag in oxygen.
  • An inert gas curing chamber – Where the printed / coated material meets the UV lamp.
  • Oxygen analyser – Measures the oxygen level in PPM with the curing chamber.
  • HMI/touch screen – This displays the PPM level inside the curing chamber.
  • Inert gas feed – The customer needs to arrange this as an added service to the electrical power, compressed and air extraction system, on a standard UV system.

Effect of Oxygen Concentration on Curing

When to use inert gas drying

The nitrogen drying system is used mainly for coating lines or on the final varnish station of a flexo press, as well as free radical silicone coatings. It can also improve curing for low migration inks for food packaging.

If you’re interested in printing with low migration inks, this blog might be interesting to read.

The response from customers is very positive as our system allows the operator to adjust the required N2 level as well as set upper and lower alarm levels on the HMI. The HMI displays this information in a very clear and logical way with red, amber and green colour codes that can be easily seen by the operator, allowing him to concentrate on the printing aspect of the application.

GEW inert gas unit

MPS & GEW: focus on the operator

With some more demanding applications, I see the N2 system as a needed technology for now and in the future, but it has to be easy for the operator to integrate, implement and control - which is what you get with the GEW inert system.  

The systems that GEW have supplied so far to MPS have been on the final print station for coating. These have been integrated onto the GEW chill roller and mounted in the lower position of the press. We have supplied several systems which have predominantly been for the same end user group within Europe and the US.

If you would like to know more about  the N2 nitrogen curing system or any other GEW curing solution, please feel free to contact me: mgreenbrook@gewuv.com

Marcus Greenbrook is Director of International Sales at GEW, serving over 20 years with the supplier of UV curing systems.

Tags: EF Press, Printing Technology, Flexo printing

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