Laser marking of the CNC manufactured parts is an important step in production for many industries. Information on the front panel, decors on the aluminum surface, or Data Matrix code on the car parts – each of them should be visible and easy to read for years.
There are well-known methods of engraving and marking parts – screen printing, powder coating, or hand engraving. Each of these has its advantages and disadvantages (eg. marks wear out or are easy to remove) and outside narrow applications – not perfect.
Laser engraving is a good alternative to the traditional marking methods of putting markings on the surface of metal, wood, or polymers. It can be easily included in the CNC machining process – thanks to that clients can get parts that are true to the quote and specification from the one machining shop.
Such a one-stop approach can reduce the possibility of error during production and in many circumstances – decrease the cost of an ordered batch.
What is laser marking and what are the applications?
Laser marking of the products and parts surface is a technique known for years – thanks to the rigidity, wear, and heat resistance of creating markings. The engraving is performed by high-energy light pulses (laser), with the appropriate wavelength. Such surface modification and its final effect are dependent on the work parameters and it can:
- create a discoloration (wanted and unwanted), which is a goal of laser engraving and marking,
- modify the surface structure,
- cause a controlled surface loss (engraving),
- and even cut through the structures.
It is worth mentioning that the markings on the surface are durable, legible, and indelible. Made with the right work parameters do not decrease the rigidity of the processed surface (eg. do not damage the anodized or chromed layer). That feature makes laser marking a standard in many industries.
The most often used technique of a permanent marking surface with a laser beam is annealing. The laser beam creates a high temperature on the marked surface that causes oxidation which leads to a change of color.
What is important – during the said process the part structure is not damaged or changed and well-performed laser marking does not speed up oxidation and/or rusting processes. There is also a difference between laser engraving and marking.
Both of these processes can be performed on the same CNC machines but the main difference is the intensity and power of the beam.
With that in mind:
- laser marking modifies a surface and leads to a controlled discoloration; the deeper structure of the part is not modified and/or damaged,
- laser engraving removes material from the surface and the difference between laser marking and engraving lies in the depth of modification – the second one created a recess from 0.1 mm (0.0039 in), that can be recognized under a fingernail.
On the other hand – the information that can be put on the surface by a laser marker is vast. We can highlight the following applications of that technology:
- typical information about the product (eg. logo or the name of manufacturer/brand),
- brief manuals or instructions of usage particular part or the controller mounted over the marked surface (eg. in the front panels of washing machines or information related to the working specification of a saw blade or cutter),
- branding information (eg. on gadgets or business cards made of unique materials like steel alloys or aluminum),
- symbols and/or data that allow identifying particular parts (eg. Data Matrix or barcodes),
- the vast variety of patterns and motifs on jewelry or decor elements.
What materials can be laser marked or engraved?
The range of materials that can be marked by laser is vast and includes almost all of the types used commonly in CNC machining. Said surface processing can be performed on:
- many types of steel (eg. stainless, casted),
- aluminum (many series and types),
- copper and brass,
- precious metals,
- the vast variety of polymers (eg. POM, PMM, polycarbonate, specialized polymers),
- wood and glass,
- and many more types of materials.
It is worth mentioning that laser marking itself is a non-contact process and does not require specialized preparation of the surface (eg. washing or priming like in many types of painting).
So: is the laser marking permanent? The short answer is: yes, it is.
That technology or marking surface is permanent and the achieved discoloration has very good mechanical properties and their wear resistance is close to the marked material. The markings have very good abrasion resistance, yet possible to remove (with the right technology, eg. by grinding/sanding or with other machining devices like a mill).
It is worth mentioning other types of laser marking processes:
- tempering – applies color markings on the surface by oxidation (that can have chosen color),
- black marking – the specialized process of a metal laser marking that focuses on delivering very short impulses of the laser beam for the surface without increasing the temperature of a machined area. The process creates a unique dark shade in the chosen area,
- laser engraving – during that process the excess material is vaporized due to high temperature on the modified surface.
On the other hand: is laser engraving a permanent type of surface modification? Yes, the said process removes material while creating an oxidized layer on the surface.
Excess material is vaporized and created a recess that is permanent and wear-resistant, with similar characteristics to the machined material. It is worth mentioning that metal laser engraving provides much better resistance than the same process performed on other types of material (eg. polymers or wood).
At what stage of CNC production perform laser marking?
Laser marking and engraving – of polymers, metals, and other materials – is usually the last stage of the manufacturing process. Shaped parts are placed in specialized, industry-grade laser markers/engravers that allow put wanted information on the surface.
On that note – many people use small home laser markers; although the idea and the principle of work are the same, the quality and potential of these devices differ from the industry-grade devices.
Small laser markers, often built on the LED laser, offer small power of the beam (up to 20-25 W), and are currently gaining more and more popularity, especially for small home-based manufacturers.
In many applications they replace small CNC mills and are a good alternative for laser marking polymers, wood, and to some extent even metal – on a (very) small scale. Such devices can cut through plywood or thin sheets of metal but their capacity is limited by the power of a laser and additional equipment (eg. heat or smoke removal).
Although popular and a first glance delivering the same effect do not have a lot in common with an industry-grade CNC laser marker.Professional devices offer higher efficiency, performance, and precision which correlates with the time required to engrave or mark surface and repeatability of the whole process.
Industry-grade CNC laser markers also provide a wider range of work settings and their modification – wavelength, power, or the laser working parameters (eg. continuous, pulsating).
Said devices use many types of professional light sources, eg.:
- CO2 lasers (for wood or polymers marking),
- fiber and MOPA lasers for metal marking/engraving,
- crystal lasers for metal and some types of ceramics.
Such availability and diversity of lasers and their operation parameters provide a better and more efficient finish.
It is worth mentioning that industry-grade CNC laser markers can create engraving – due to the higher power of light beams and more efficient heat dispersion systems. Most "at home” small CNC lasers do not provide such a possibility.
But still: technical aspects of laser marking or engraving remain the domain of professional CNC operators. With close cooperation with said professional, you can order a desired batch of laser-marked parts.
If you need a precise laser marking of CNC machined parts and even deep engraving – contact RADMOT.
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