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Engraving is the most common of all Laser marking applications, the engraving process is produced by the Laser beam removing material to create a mark, where the Laser acts like a chisel and blows away selected areas of the subject material.
This application insight explores two different types of Laser engraving, both Light and Deep engraving. Looking at different materials including stainless steel, tool steel and silver, it shows specific examples of Laser engraving and the benefits of using a Pulsed Fiber Laser for engraving over other technologies.
There are two types of Laser engraving. Light engraving is where a relatively shallow trench is created, between 5µm and 25µm. The depth achievable depends on the material, and also the power and the dwell time of the Laser. Deep engraving is used for making moulds and dies, stamps, etc. The depth that can be achieved is entirely dependent on how the material absorbs the Laser, how much energy the Laser has, and how long the Laser can dwell on the target. Deep engraving is usually a fairly slow process.
Both types of engraving can be carried out on surfaces such as different metals and some plastics. Engraving can be used to make marks, for example identification numbers, and logos and can also engrave complex images created in graphics packages.
Lasers have many advantages over older technologies such as machining. The main advantage is that there is no contact between machine parts which means there is no tool wear. Lasers also offer greater precision and can engrave more complex patterns and images.
Fiber Lasers are a relatively new technology that have shown very promising results in the field of Laser engraving. Compared to other types of Lasers, they can offer better quality in marking and deep-engraving thanks to short pulse duration minimising thermal effects and faster speed processing with high peak power pulses.
Figure 1 & 2. Examples of Deep Engraving by our redENERGYG4 Pulsed Laser – Images courtesy of LMco
We manufacture a redENERGY G4 Pulsed Fiber Laser which is one of the best Lasers in its class. It offers unrivalled peak power, has high frequency repetition and unprecedented control, with the ability to fine-tune operations to get the best results. For Laser engraving this means reduced processing times, clearer marks and better mark depths.
When performing deep engraving as illustrated by the two examples in the next sections higher pulse energies and higher peak powers are required to achieve greater ablation. Also Deep engraving needs lower frequencies for greater spot overlap. Typically this means slower speeds.
Using our redENERGY G4 Pulsed Fiber Laser, complex decorations can be engraved into silver (Figure 1). For this example, the Laser was operating from CW-500kHz giving total control of peak power and the pulse energy giving fine processing control. First the engraving was made using two cross-hatch passes at 2m/s and at 25kHz Waveform.
This removed a depth of approximately 0.13mm. A final pass was made smoothing the engraved surface and whitening the mark. This was done as a single pass at 3m/s at 250kHz Waveform 3.
Deep engraving in steel can be done using our redENERGY G4 Pulsed Fiber Laser (Figure 2). In this case three passes are made. The first two passes perform the engraving while the last pass polishes the surface giving a distinctive mark.
High precision deep engraving can be achieved by careful selection of pulsed wave forms and other process variables (Figure 3). The unrivaled flexibility of our redENERGY G4 Pulsed Fiber Laser enables optimisation of the pulse characteristics such as peak power, pulse length, pulse energy and pulse frequency to give the best engraving.
Figure 2: Stainless Steel engraving with 30W Laser. Figure 3. Precision deep metal engraving – Sample supplied by ACSYS Lasertechnik GmbH.
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