8 January 2008

Rofin's StarScribe laser range makes selective weakening and perforation easy

Within the consumer goods industry, packaging is considered to be a crucial factor in the consumer's product experience. However, difficulties in opening packages are surprisingly common causing spills and perhaps even minor injuries. The opening process often requires too much initial force and can be hard to control due to poor or inconsistent quality of mechanically created opening lines.

Easy Opening

Rofin laser systems offer a more consistent and reliable solution to a wide range of scribing and perforation applications. The capability of the laser to "select" a particular film layer(s) to scribe enables the generation of precise easy opening tear lines whilst leaving other layers intact which are required to protect the product from light and humidity. Rofin lasers can even be used to scribe freeform lines, for example following a contour on the print therefore providing new inspiration and ideas for packaging designers.

Polymers such as PET, PP or PE have different properties of absorbing and reflecting light at the CO2 laser wavelength. Within multi layer materials the absorption of the laser light in one layer results in ablation, whilst the next layer, made of a different material, will remain 100 percent intact. Aluminum or metallic layers on the other hand act as a highly reflective barrier to the laser light. All of this enables precise location and depth of the desired scribing features within composite packaging materials. The easy opening tear strip can therefore be generated without compromising the barrier or mechanical properties of the bag or pouch ( Fig.1 ).

The opening lines are clearly visible and opening the package therefore becomes much easier for the consumer. Even with strong packaging materials such as PE/PE combinations, Rofin lasers can create perforation lines which can have from as few as 5 holes /cm or up to as many as 50 holes/cm for easy tear- off applications. From the perspective of the product manufacturer laser scribing is a contact and wear free process which guarantees consistent quality and high process reliability.

Perfect Perforations

Rofin lasers are also used to perforate product packaging. Perforations (Fig.2) are used to increase the shelf life of perishables such as salad and other fresh produce, or to control pressure changes within packages being cooked in microwave ovens. Laser perforation lines can also be used for easy-tear-off applications and unlike mechanical tools such as rotating knives or barrel punches, lasers work contact free, suffer minimal wear and tear and offer excellent process integrity.

In perishable foods packaging, quality and shelf life depend on a balance between air circulation and the preservation of humidity. For package perforation applications Rofin lasers offer significant advantages over conventional processes such as needles or flame. Based upon the experience gained in over 25 years of laser perforation, Rofin applies CO2 lasers with high pulse intensities to perforate all layers of the packaging material. The resultant micro-melted edge of each hole prevents the formation of micro-fissures which could damage the packaging integrity. Depending on the production volume and the task at hand, Rofin offers systems which incorporate beam splitters and up to four focusing heads for perforation in the direction of the web, or polygon mirror optics which provide up to 16 perforation lines and can deal with very high web speeds. Optimum climate management can be achieved by producing holes which can range from 60 to 300 µm in diameter, arranged in regular patterns and clusters or even synchronized to match the print on the packaging. Hole pitch can be adjusted from 4mm to 500 mm even within the same line.

StarScribe Family of Lasers

In most cases, laser processing in flexible packaging is performed on web based material. For scribing lines in the web direction, Rofin offers the StarScribe WD System ( Fig.3 ) incorporating beam splitters which distribute the laser to individual focusing heads with each laser beam scribing one line into the web. For materials and applications which require cross web processing such as bags and pouches, the Rofin StarScribe CW (cross web) uses fast scanner heads driven by Galvanometer motors, which are used to deflect the beam across multiple axes. The control software not only enables beam compensation for the web movement it can even be used to create freeform scribing paths such as waves or squares etc. once again opening up new possibilities for packaging designers to make their products more usable, more attractive and unique.

The complete range of StarScribe laser systems includes :-

StarScribe Easy S – a 100W compact turnkey CO2 laser system which can easily be integrated into existing production lines and web handling systems. A flexible articulated arm enables fast beam positioning with minimal effort and the system can also have one, two or four processing heads.

StarScribe Easy Remote – used for applications which require higher power or to obtain higher speeds, this system is available with options of 100W, 200W or 300W laser power.

StarScribe WD – an extremely high performance system which can be integrated into existing slitters from all established manufacturers. Up to 8 processing heads can be used for simultaneous scribing in the web direction with speeds up to 600m/min. Laser power source options for this system range from 100W to 2,000W.

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