laser research

Laser cutting

Laser cutting is a technology that has been used in industry since the 1970’s. The first common application was mainly cutting acrylic for sign-making.  Since then the process has been adapted by virtually every industry, and is now a significant process in a lot of manufacturing economy. Laser cutting is excellent at processing many different materials. Unlike physical machining laser profiling is not affected by the hardness of a material, meaning materials such as high carbon steels can be cut as easily as standard mild steel.

Laser cutting works by melting, burning or vapourising the material, while an assist gas is employed to "clear" the cut zone of the molten / burnt material or the gas vapour. In the early days of laser cutting the setting of the laser to produce the desired effect was a manual process and very complex. The latest machines now come with many of the common parameters pre-programmed, allowing much easier setting. However operators still require many hours of training to run a laser safely, efficiently and economically.

The cutting process is very complex, but basically involves pre-piercing the material outside the area of desired cut, moving the laser beam into the cutting area to apply heat, and finally use an assist gas to remove the heated material and produce the cut. The type of assist gas employed is critical, and is dependent on the material to be laser cut; most commonly used are Oxygen (used predominantly for carbon steels), Nitrogen (used for non-ferrous steels & non-metals) and Argon (used for more exotic materials such as titanium).

There are many different methods in cutting using lasers, with different types used to cut different material. In vaporization cutting the focused beam heats the surface of the material to boiling point and generates a keyhole. The keyhole leads to a sudden increase in absorptivity quickly deepening the hole. As the hole deepens and the material boils, enlarging the hole further. Non melting material such as wood, carbon and plastics are usually cut by this method.

Melt and blow or fusion cutting uses high-pressure gas to blow molten material from the cutting area, greatly decreasing the power requirement. First the material is heated to melting point then a gas jet blows the molten material out of the kerf avoiding the need to raise the temperature of the material any further. Materials cut with this process are usually metals

Thermal stress cracking is used for brittle materials are particularly sensitive to thermal fracture, a feature exploited in thermal stress cracking. A beam is focused on the surface causing localized heating and thermal expansion. This results in a crack that can then be guided by moving the beam. Thermal stress cracking is usually used in cutting of glass.

Laser engraving, is the practice of using lasers to engrave an object. Laser marking on the other hand just discolors the surface, without cutting into the surface. The technique does not involve the use of inks, nor does it involve tool bits which contact the engraving surface and wear out. These properties distinguish laser engraving from alternative engraving or marking technologies where inks or bit heads have to be replaced regularly.

The impact of laser marking has been more pronounced for specially designed "laserable" materials and also for some paints. These include laser-sensitive polymers and novel metal alloys.

The term laser marking is also used as a generic term covering a broad spectrum of surfacing techniques including printing, hot-branding and laser bonding. The machines for laser engraving and laser marking are the same, so that the two terms are sometimes confused by those without knowledge or experience in the practice.

Laser Engraving or Laser Etching is a surface technology. The laser interacts with different types of material in different ways. For Organic Materials such as Wood the laser burns the surface of the material, almost like a very accurate branding iron. The depth can be varied and 3D effects can be created. For Polymers such as Acrylic the laser vapourises part of the surface, changing its appearance. For Natural Materials such as Granite or Stone the laser actually causes tiny fractures in the surface, and this results in a textural and contrast difference with the material. We can only do 2D engraving with these materials.

For Metals the normal method of marking is to use a YaG laser to alter the structure of the material surface. Coated metals are different - for example with painted brass we remove the paint, with anodised aluminium we change the colour of the anodised surface.

The demand for personalized jewellery has made jewellers more aware of the benefits of the laser engraving process.

 Jewellers found that by using a laser, they could tackle an engraving task with greater precision. In fact, jewellers discovered that laser engraving allowed for more precision than other types of engraving. At the same time, jewellers discovered that laser applied engravings had a number of other desirable features.

 At one time jewellers who attempted to do laser engraving did need to use large pieces of equipment. Now the devices that perform laser engraving come in units. Some entrepreneurs have placed such units in mall kiosks. That has made laser engraving jewellery much more accessible. The makers of machines for laser engraving jewellers have developed some very specialized equipment. They have designed machines that can engrave the inside of a ring. They have also created machines that have the ability to engrave the back of a watch.

 A laser can cut into both flat and curved surfaces such as the surfaces on jewellery. That points out the reason why jewellers have welcomed all the adaptations for the creation of laser engraved jewellery.