Terrance W Thompson of US specialist company PCT Engineered Systems discusses how recent advances in low energy electron beam technology are expanding the options for converters
As interest in electron beam (EB) technology among converters continues to gain momentum, it is sometimes hard to fathom that these systems have been use in industrial applications for more than 30 years. Why are we seeing such a ‘spark’ in a technology that’s been around for so long? Because it’s not the EB technology that continues to capture converters’ imaginations, it’s the growing range of applications EB can provide to them.
For years, leading converters have documented the myriad real world advantages EB generates: improved product performance, product consistency, high throughput, energy savings, and environmental advantages. However, now converters seek more.
New converting applications require smaller, more efficient systems that can integrate directly into existing and new process lines. Equipment providers such as PCT are responding to these requests by introducing innovative new designs that leverage advances in technology and years of industrial EB system experience.
Most of the recent developments in EB equipment have focused on ‘low energy’ systems, which traditionally operate in the range of 70-150kV. This equipment is well suited for curing of inks and coatings used in package printing applications and can also address a variety of non-printing converting applications. Among the key recent innovations are the following factors.
Integrated shield roll design
EB systems require shielding to protect personnel from the x-rays generated by the interaction of the electrons with materials in EB equipment. PCT recently introduced an innovative design that uses an integral chill roll as the shield roll for proper radiation shielding. This technology can be used for EB systems up to 300kV. This patented design employs a temperature controlled roll to support the material while the roll simultaneously serves as a functional portion of the required shielding. The results are reduced size and materials, minimisation of the volume that must be inerted with nitrogen, and easy access for threading and cleaning.
Advances in printing press technology targeted at the flexible packaging market have opened more opportunities for EB systems. An important package printing technology is the use of variable sleeves on web offset presses. This style of press requires the EB system to accept a low web entry height. The web height will also vary as the sleeve diameters change. The latest EB system designs accommodate these web handling requirements and maintain a ‘side fire’ orientation, which is preferred for the maintenance access required to perform a window foil change. In addtion, the small size of this design also facilitates easier retrofits onto existing production lines with a web height of 600mm.
Extended voltage low energy
The first generation of more compact, lower cost EB equipment was introduced about 10 years ago. It operated in the range of 80-125kV, which was suitable for curing relatively thin layers of inks and coatings. Curing adhesives for lamination or crosslinking of thicker materials required industrial EB processors operating from 150-300kV.
In recent years, compact equipment that can operate at up to 175kV has been introduced to the market. These higher energies allow one-side treatment of materials up to 150g/m2 (150 micron for materials with a density of 1.0g/cm3).
Digital high voltage power supply
EB systems have been introduced that now use high frequency switch-mode power supplies. The high frequency switching of the power transistors minimises the voltage ripple to give a power factor above 0.90. This reduces electrical power consumption.
Sealed tube emitters
Sealed tube EB emitters have been in the industry for several years. Recent advances in reliability are now allowing these emitters to be applied in an increasing range of industrial applications. Their integration into appropriate shielding configurations allows processing of a wide variety of materials including webs, flat materials and 3D objects.
Web applications for EB systems based on sealed tube emitters may include narrow web printing, coating, and crosslinking.
Potential applications for narrow web printing include the curing of thick and/or high density ink layers; supplemental curing of UV inks; curing of EB inks and coatings for food packaging; EB adhesive lamination; and EB coldfoil transfer.
A number of new developments in low energy EB equipment address the needs of converters. These developments in equipment technology will continue to facilitate the growth of EB interest worldwide.
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