Virtu glass print line
Sophie Matthews-Paul visits WP Digital to check out this finely tuned printer development.
With glass being an inorganic material many might have believed that to print it using organic UV-curable inks would mean countless adhesion problems ruling it impractical for the digital printing market.
However, machine manufacturers are reporting success printing direct to glass and one of these, WP Digital, now has a production line which has been honed to accommodate this material. These printers are available in the UK from sole distributor, Digital Print Innovations, which arranged a visit to the Swiss producer of the Virtu range of UV-curable machines.
The company's 2.5m and 3.5m machines, designated the Virtu RS25 and RS35, can now be integrated as the key part of a combination platform suitable for the industrial and decorative application of ink to glass. With a maximum addressable resolution of 1200 x 1016dpi, and using Fujifilm Dimatix Spectra SE-128 printheads, output can be in four or six colours with the additional white, either as an overprint or an underprint.
Printing onto glass necessitates special handling that, in WP Digital's line, starts with a specialist surface treatment and cleaning. This treatment needs to incorporate a bonding layer so that the surface of the material, that is inorganic and non-porous, is suitable for acceptance of the UV-curable inks. Because the entire production line is repetitive, it makes sense to incorporate it into an integrated process so that treating, printing and curing can all be carried out without manual intervention.
Although preparation of glass can be carried out manually, automatic cleaning and pre-treatment are preferable, particularly in continuous production runs. Mechanical cleaning is used to remove all possible contamination, with a heavy-duty chemical cleaning agent used to eradicate grease and other residue which can arise during handling. Once the surface has been purified, the next phase changes the microscopic layer of the glass, providing a roughness to encourage the effectiveness of the adhesion promotor. This is applied immediately after flame coating in order to form an organic bridge between the ink and the glass surface, increasing stability.
Because glass is normally heavier than relative sizes of typical display materials, the support and power of the vacuum table needs to be able to handle it efficiently. This factor has been incorporated into the WP Digital Virtu glass production solution which also takes into account the breakable nature of the material and the fact that it needs to be treated with care.
Although both the Virtu RS25 and RS35 are also available as standard units for UV-curable ink-jet production, they have been adapted successfully to integrate into a glass production line. Alternatively, they can be added to existing cleaning and pre-treatment stations on a client site.
WP Digital sees the digital printing of glass using UV-curable inks as being just as relevant to the decorative market sectors as to the industrial marking arena for which the company's machines were originally developed. Because they are already extremely sturdy and solidly constructed, and well able to handle the idiosyncratic behaviour of glass before and during printing, the Virtu RS25 and RS35 are well suited to the needs of commercial applications.
The machine's printing table is sectioned in vacuum zones that can be operated independently by two vacuum pumps in a choice of modes, with the strength of the power being controlled within the operator panel. An integral ionising unit eliminates any likelihood of static electricity.
Thus, the awareness of using colour within a wide range of applications is gaining appeal in the area of home decor and furniture, as well as within the display sector. Not surprisingly, architects increasingly are wanting to optimise decorated glass in new and refurbished buildings.
The machine at the heart of the WP Digital glass production line uses piezo drop-on-demand inkjet technology. The Virtu RS25 features a vacuum table with 21 individually adjustable vacuum zones whilst the wider RS35 model has 30 separate zones. In its 36 head version it is available in CMYKLcLm or four colours and two white channels. The 48 head unit option has six colours and two channels of white.
Solidly made, the Virtu models incorporate linear motors instead of belts for smooth and consistent production. They accept output from most major RIP suppliers, including Caldera and Onyx, and connectivity is via ethernet. The continuous feed option is suitable for use with a range of rigid substrates, including glass up to 3mm thickness. In addition, they handle most rigid and flexible materials, including digital textiles.
Prices start at ?295,000 for the four-colour plus white version of the 2.5m Virtu RS25. Fully automated glass lines vary in cost according to end-user requirement.