GLASS PROCESSING


manufactures the 48 series, Firestar and Fenix Flyer CO2


30W laser with an M2


laser markers, all ideal for marking glass. A value of around 1.2 would be


ideal for this application. Synrad has researched laser marking glass and


has identified three methods to control the amount of fracturing caused by the laser radiation. Firstly, the mark can be made using multiple laser passes. Tis heats the material adjacent to the mark and forms a stress gradient to reduce the chances of secondary fracturing. Te method is effective for marking soda lime and borosilicate glass. A second method is by forming a series of ring


fractures, created by the heating and cooling cycle using discrete laser spots. Te method works well with common optical materials and tempered, chemically strengthened, or plain soda lime float glass. A different take on this method uses a larger spot size to produce a crazed surface fracture. It works best with high-quality glass. ‘It’s [glass marking] not a given science, as it


depends on the type of glass and the quality of the glass,’ said Earl. Te laser parameters for branding drinking glasses with a logo, for example, would be different to how a data matrix code would be engraved on a windowpane. ‘Because a windowpane is toughened, the glass tends to reflow


rather than crack,’ Earl continued. ‘Whereas marking a soda glass or a soda-lime-type glass used for bulbs and tableware, you would get small fractures rather than a reflow.’ One way a mark can be created is by laying down


single dots in a raster style. ‘It’s about getting the spacing and spot size of these dots right that give the image resolution,’ Earl noted. ‘But as you go up in spot size, you’ll get a different effect. A large spot size will give a frosting effect, whereas a small spot gives a very fine discrete cracked spot in the glass.’ Laser Lines has customers marking nucleation


points onto the bottom of beer glasses or champagne glasses to encourage bubbles to form. Earl noted that the lens used in the system has to have a sufficient focal length to focus the beam onto the bottom of the inside of the glass. Te laser produces a series of closely spaced dashes, which creates more surface texture. Tis increases the beer bubbling effect on the mark location. Laser marking of window glass is different, says


Earl. Here, vector lines are generally created – rather than discrete dots, which cause the glass to melt locally and reflow to create the mark. ‘Marking window glass is a big business,’ stated Earl, ‘which could be anything from a data matrix code to a customer logo or human readable text.’


Tere is alternative laser technology and


methods for engraving glass, including excimer lasers emitting in the UV and even sub- nanosecond lasers, which, Gäbler says, can be used for marking very thin, high-quality glass. Coherent acquired Innolight last year for its sub-nanosecond laser technology, which has uses in glass engraving. ‘Sub-nanosecond lasers are capable of a


diffractive marking, whereby the diffractive index in the glass is altered to make the mark without microcracks,’ explained Gäbler. Medical ampoules, for instance, can be marked in this way, as can glass bottles containing expensive products for anti-counterfeiting purposes. ‘Tese are applications which in the past have


required expensive femtosecond lasers,’ said Gäbler. ‘However, now this can be achieved with a green sub-nanosecond laser, which is 15 per cent of the cost of a femtosecond laser. Tis new technology might open up new markets.’ While CO2


lasers remain a good tool for cutting


and engraving glass, ultrafast laser technology is opening up new techniques. With mobile phone and display manufacturers potentially turning to sapphire as a cover glass material, there is a huge future market for ultrafast laser systems to cut this brittle material.


500W Fiber Laser Power & Control


The redPOWER® R4 series of ber lasers from SPI has been designed to


meet the highest standards of reliability, performance, repeatability and user safety. SPI’s R4 lasers are constantly nding new cutting, welding and materials processing applications in markets including industrial, medical devices, electronics and printing.


Visit us at Photonics West 2014 booth #4939, or for more information regarding the redPOWER R4 and the entire SPI product range, go to our website >> www.spilasers.com/products


www.lasersystemseurope.com | @lasersystemsmag


ISSUE 21 • WINTER 2013 LASER SYSTEMS EUROPE


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