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Marking with lasers

An object can be marked using a laser to label various kinds of objects. Basically, laser marking involves modifying the optical appearance of a surface that it hits, or ablation of one or more materials. Among laser material processing methods, marking is a particular subgroup.

Marking with lasers: applications

Over the past several decades, laser marking has been used for a wide variety of purposes.

There are many industrial products which need to be labeled with details such as model and serial numbers, logos, barcodes, “to be used by” dates and the like. Some of these include machine tools, printed circuit boards (PCBs), integrated circuits, cables, keyboard buttons, credit cards, food packages and bottles. Often, these labels have different details for each individual part, so a simple stamping is not an option.For quality control, it is often necessary to add traceable information. A silicon wafer used for photovoltaic cells or electronics may be marked with the boule from which the wafer was cut and at what position. In this way, possible problems can be traced back, allowing them to be identified and solved more quickly.

The advantages of laser marking over other marking technologies, such as ink jet printing and mechanical marking, include very high processing speeds, low operating costs (no consumables), constant high quality and durability of the results, the ability to write very small features, and exceptional automation flexibility. The Laser marking Machine, however, can be quite expensive.

Information about the technology

Another method is to create a whole label in one shot, using a suitable type of mask, placed at an appropriate point in the beam path, such that the mask features are imaged onto the workpiece. Due to the requirement of fabricating masks for the latter method, the pattern cannot be changed from piece to piece. Furthermore, the masks tend to wear out over time and need to be replaced regularly. However, scanning methods appear to be used more and more frequently. Machines that mark with lasers

Laser marking machines typically include a pulsed solid-state laser, a compact beam delivery system, and possibly other auxiliary items, such as fume extractors. A means for inserting and aligning the pieces to be marked is also necessary, as well as an automated movement and alignment machine. Materials are marked “on the fly” in some industrial settings as they move along the marking machine.

CO2 lasers are often used to mark plastics, wood, cardboard, paper, leather, and acrylic. A continuous-wave laser is often used for this purpose.CO2 lasers are less suitable for metallic surfaces due to their small absorption at long wavelengths (around 10 m); laser wavelengths e.g. around 1 m, which can be obtained using lamp- or diode-pumped Nd:YAG lasers (typically Q-switched) or fiber lasers, are more appropriate.

An average laser power of 10 to 100 watts is used for marking. For machines with high throughput, this power can be substantially higher.

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