- Text Size:
Information Sheets
Marking
Lasers are now an established and accepted method of marking and coding most materials and products and are a considered alternative solution to and replacement for traditional marking methods such as inkjet, labelling, hot stamp, embossing, dot peen etc.
Laser marking is typically achieved in one of three ways:
- ablation (where a layer of material is removed to reveal substrate and offer contrast)
- chemical change ( where focussed beam encourages a reaction and change of material state, for example CO2 laser will always produce a brown mark on PVC)
- engraving (where a mark is achieved by engraving the material and not necessarily offering a contrast)
There are generally two types of lasers used in today’s packaging and industrial marking applications – CO2 and Nd:YAG. In general CO2 laser at wavelength 10.6 microns will mark most materials except metal and Nd:YAG at wavelength 1.064 microns will mark all metals and is often more suited to marking some plastics and ceramics for example.
The wavelength of any laser dictates the resulting reaction when applied to any material or product, where CO2 at 10.6 microns and Nd:YAG at 1.064 microns are most common types there are other available wavelengths for specific applications. As an example CO2 laser sources and marking systems are also available at 9.3 microns and this type laser is more suited to marking of PET, where a standard CO2 laser at 10.6 microns offers a perfectly acceptable visible engraved mark, a CO2 laser at 9.3 microns offers a whitish mark and foams the surface so not only offers a more visible contrasting code but also reduces any chance of material penetration and production puncture. Similarly where most YAG applications are at 1.064 microns, aerospace cable is marked with a double frequency YAG system at wavelength 532 microns to avoid any surface damage to the cable.
Although initial investment required for laser is normally higher than alternatives there are clear advantages and benefits when using laser that can offer a long term cost effective solution – for example CO2 laser types currently used in the packaging industry are non contact, consumable free and require minimal maintenance. The systems are extremely reliable and provide high quality results with minimal production down time.
CO2 lasers are available in three formats – TEA (transversely excited atmospheric) or more commonly know as mask lasers, dot matrix and vector. TEA lasers are now very rarely used except in very high speed applications or when product vibration will affect code quality and this type laser is a single discharge through a mask or stencil. Dot matrix lasers are now deemed to be obsolete technology as they offer no benefit or cost advantages over currently available and widely used vector or scanning lasers. Vector lasers are generally available in the 10, 15, 25, 30, 50 and 70 watt power ranges and with XY scanning offer high quality, high speed marking at an affordable price.
Vectors lasers with sealed CO2 tubes and therefore no consumables also offer as standard all alphanumeric characters, any font, barcodes, 2D matrix, graphics and logo marking potential and with standard available focus lens options can offer large area scanning – a clear advantage over other methods as only one laser is required to mark multi products.
Nd:YAG lasers are typically used for marking of any metal part or component although many other materials can be marked. Typically YAG lasers are an integral part of a process rather than an on-line coding system. Stand alone marking stations will not only have a YAG laser installed but with also handle and manipulate the product as required. Extremely high quality and intricate marking can be achieved with a YAG laser, as an example YAG lasers are used for hallmarking of precious metals.
As CO2 many types of YAG laser are currently available and power range is typically 10, 30, 50 and 100 watts for marking applications. As an example a 50 watt Diode pumped YAG laser would be used for high speed marking of product either stationary or moving where a 100 watt lamped pumped YAG laser could be used for either deep metal engraving or high speed on the fly applications.
Nd: YAG lasers are not generally used in the packaging industry due to cost and safety considerations. Where CO2 laser system pricing can be anywhere between £10,000 and £40,000 for an installed system and guarding requirements can be achieved by use of clear 8mm Makralon with interlocked access as typical machine guarding, YAG requires light tight enclosures for guarding purposes and typical investment for an installed system will be in excess of £25,000 and a full turnkey solution offering a 100 watt YAG system with 3D product manipulation etc in excess of £100,000.