24 Jul LASER ENGRAVING OPTIONS
In recent years the subject of engraving has witnessed the migration of many industries away from the traditional methods of rotating cutters, chemical etching and many other established means of permanently marking components. One of the causes of this migration is the way in which more advanced methods have become much more affordable and therefore accessible to a much wider audience.
The most accessible and affordable means of laser engraving is with a CO2 laser source. Typically based around a water-cooled glass tube and machine bed sizes from A4 upwards, CO2 machines will usually cut non-metals as well as engrave them and offer impressive results on plastics, woods and leather. They also produce fine results on coated metals such as anodised aluminium and power coated steel. However, they are unable to engrave onto uncoated metals without first applying an aerosol or brush applied ceramic marking compound. Available in several colours, once dried the compound can be burnt into the surface of the material using a CO2 laser. The excess compound is simply washed away to produce an impressive contrasting finish, particularly on shiny metals such as stainless steel and brass. Because of their relatively large bed sizes, CO2 engraving and cutting machines are well suited to engraving large numbers of small components using a located jig arrangement. Because of the machines cutting capability it can even manufacture its own jig !
HPC recommend that for CO2 engraving, a maximum laser tube power of 80W is chosen which offers a typical working life of around 3,000 hours. Larger tubes can prove difficult to control when engraving intricate designs and some of the detail may be lost.
This traditional method of CO2 engraving involves the laser head repeatedly moving left to right whilst indexing forward with each pass, much like an inkjet printer. Whilst extremely accurate and well suited to large batch runs it is a time-consuming process.
The next generation of CO2 laser engraving machines utilise a “Galvo” static laser head fitted with a series of dynamic internal mirrors that direct the laser beam with incredible accuracy and precision. The machine typically utilises a conventional 60W or 80W water cooled CO2 tube and so will not engrave onto uncoated metals unless the ceramic marking compound is applied first and allowed to dry. A Galvo machine is not well suited to cutting either, unless very thin materials such as paper or card are involved. However, the speed at which the engraving magically appears before your very eyes really is incredibly impressive. Around 10 times faster than a conventional CO2 laser machine, the Galvo has no external moving parts and therefore requires little maintenance. However, the marking area is usually limited to around 300 x 300mm maximum and so parts usually need to be engraved individually.
For the ultimate in laser marking on uncoated metallic components, the ideal solution is a fibre marking machine. Once again incorporating the Galvo head, an air-cooled fibre optic laser source is installed in preference to the CO2 option and offers a typical working life of around 100,000 hours. The compact design of the fibre laser source means the machine is much smaller than the CO2 equivalent and is ideally suited to engraving uncoated metals with incredible speed and precision. Laser powers are usually between 20-50W and marking area once again limited to 300 x 300mm maximum. However, the incredible speed and accuracy offered by a fibre engraving machine on uncoated metals is extremely difficult to achieve using any other means.