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Laser Engraving Industrial

Laser Engraving Industrial - Cutting


Lasers of high power have the capability of not only engraving, but cutting material. The same basic techniques and considerations are used in fabrication of many cut shapes, whether in wood or in stacked fabric for apparel manufacture, or even metals (plasma cutting). It is just all done at power levels which allow the laser to penetrate quickly through the piece rather than only at the surface level. Evacuation of released gases is often provided by a forced-air "snout" trained directly on the laser cutting area. The process is also referred as laser converting in some industies.


Laser Engraving - Printing


Direct laser engraving of flexo photopolymer plates or sleeves (which fit over a mandrel) is attracting wider interest following some recent technical developments and mergers of vendors. Up to now the process has been associated with wide-web flexo printing of, for example, film or paper packaging (flexible packaging). Here it competes with rotary gravure, although direct laser engraving is also being introduced. For the less expensive flexo process, the technology is being adapted for smaller formats suitable for engraving flexo plates or sleeves mounted on the actual printing cylinders.

This includes narrow and mid-web flexo presses (up to 20-24 inches wide), which could open up the market for self-adhesive label and packaging converters interested in the digital - that is filmless - route. With this process there is no integral ablation mask as with direct laser imaging (see below). Instead a high-power carbon dioxide laser head burns away, or ablates, unwanted material. The aim is to form sharp, relief images with steep, smooth edges to give a high standard of process color reproduction. A short water wash and dry cycle follows, which is a lot less involved than in the post-processing stages for direct laser imaging or conventional flexo platemaking using photopolymer plates.


Laser Engraving - Direct Laser Imaging


Closely related is the direct imaging of a digital flexo plates or sleeves 'in-the-round' on a fast-rotating drum, or cylinder. This is carried out on a platesetter integrated within a digital prepress workflow, that also supports digital proofing. Again, this is a filmless process, which removes one of the variables in obtaining the fine and sharp dots for screened affects, including process color printing.

With this process the electronically-generated image is scanned at speed to a photopolymer plate material that carries a thin black mask layer on the surface. The infrared laser-imaging head, which runs parallel to the drum axis, ablates the integral mask to reveal the uncured polymer underneath. A main ultraviolet exposure follows to form the image through the mask. The remaining black layer absorbs the ultraviolet radiation, which polymerizes the underlying photopolymer where the black layer has been removed. The exposed digital plate still needs to be processed like a conventional flexo plate. That is, using solvent-based washout with the necessary waste recovery techniques, although some water-washable digital plates are in development. This technology has been used since 1995 and is only now becoming more widely used around the world as more affordable equipment becomes available. Trade sources say there are around 650 digital platesetters installed in label, packaging and trade platemaking houses.

In flexo direct laser engraving can be done using a CO2-laser. This makes it possible to direct ablate the non-printing area. This way steps like UV-exposing, chemical washing and drying are not necessary anymore. Before the year 2000 lasers only produced lower quality in rubber-like materials. In these rubber-like materials, which had a rough structure, higher quality was impossible. At the Drupa 2004 the direct engraving of polymer plates was introduced. This had also an effect on the rubber-developers who, in order to stay competitive, came with new high quality rubber-like materials. Since then direct laser engraving of flexo-printingforms is seen by many as the modern way to make printing-forms for it is the first real digital way