A laser is a piece of equipment that produces photons of energy for many different applications. The word "laser" comes from the words “Light Amplification by Stimulated Emission of Radiation”.
Since the 1960’s, when the first working lasers were demonstrated, the variations and applications of laser technology have propagated into many different industries. The focus of this article is the application of laser technology to welding in Small to Medium Enterprises.
Main industrial laser types and applications include:
Nd:YAG: This solid state laser produces photons at a wavelength of 1064 nm up to 10kW of continuos wave (CW) power. They can be lamp or diode pumped, have a pulsed or CW output and be fibre coupled. These systems are generally used for welding, cutting, heat treatment and drilling. Nd:YAG systems have been in wide commercial use for the last 15 to 20 years.
CO2: A gas laser system producing photons at a wavelength of 10.6 um with powers up to 60kW. As the 10.6 um wavelength energy is absorbed by fibres, these lasers cannot utilise fibre coupling thus use mirrors and lenses to control laser characteristics. The main applications for CO2 lasers include cladding, cutting and heat treatment. The CO2 technology has been in commercial operation for over 20 years and is a mature product.
Diode: Uses semiconductor (diodes) to produce photons with a wavelength between 808 and 980 nm — Low IR range. Powers are up to tens of kW’s. These lasers can be fibre coupled and are gnerally CW. These systems are reaching maturity and are used for brazing, cladding, heat treatment and welding.
Excimer: A gas laser system producing photons between 157 to 353 nm or UV range. Excimer systems are generally used for micromachining applications. 3-Dimensional laser cutting with an Nd:YAG fibre delivered laser system integrated with a robot.
Some applications and examples of laser welding:
Laser welding is used in the aerospace, automotive, electronics, medical and many other industries. Some applications for these industries include:
Aerospace: welding of turbine components, structural components in titanium, steels and aluminium.
Automotive: welding small instrument packages (air bag initiators, fuel injectors), structural welding and body panel brazing.
Electronic: welding small instrument packages (capacitor cans, battery cases, packages) in various materials.
Medical: pacemaker and implant case welding, tool welding.
Requirements for a Laser System Installation:
There are four main areas that need to be considered for a laser welding installation. These include the laser itself, the ancillary equipment (such as materials handling, chillers, power supplies, etc), safety equipment and the staffing requirements.
The first is the laser source equipment. The laser needs to be selected so that the photon characteristics (such as wavelength, beam quality, spot sizes, etc) match the materials and process requirements. Some materials that can be laser welded include steels, aluminium, copper, many different alloys, some dissimilar metals (eg copper to aluminium) plastics, etc. The diode and Nd:YAG systems are most commonly used for welding and cutting of three dimensional products.
Ancillary equipment is required to support the work-piece and provide services to the laser source. A laser source requires power and cooling. Power is supplied via distribution boards and transformers. The cooling is usually supplied from a water chiller unit. Robots and X-Y tables are used to move the optics or the work- to the correct location for welding. Materials handling equipment (cranes, hoists, and vonveyors) are used to move the work piece to and from the work area.
Due to the wavelength and power of the laser systems, safety enclosures are required. A typical laser welding system is classified as a class 4 laser device and can potentially cause eye and skin injuries if they are not guarded. Therefore a laser welding system requires solid guarding as well as personal protective equipment for an operator. Safety interlocks are required so as the laser becomes inoperative if the interlocks are open.
Staff education is the final requirement for a welding laser system. As there are many parameters involved in laser welding (materials, process speeds, laser settings, optics and process gasses), a high level of education is required for engineering staff. An organisation considering laser welding would need to have access to technical knowledge of the process, laser safety requirements and materials handling.
Some Advantages of Laser Welding for SMEs:
There are three main advantages for SMEs utilising laser welding. They are the laser as a technology enabler, the product improvements achieved from laser welding and competitive advantages.
The technology enabler allows an SME to perform processes including intricate cutting (eg 3D cutting), fine welding detail, can welding of sealed electronic components, dis-similar materials welding, deep keyhole welding, plastics welding and smaller part processing (micron level). Some of these processes cannot be achieved using any other process except laser.
Some product improvements include quality of the weld (achieve a more homogenous and consistent weld characteristics resulting in higher strength and durability), minimised heat affected zones, speed of welding operation and reduction of post processing operations (e.g. grinding and cleaning of welds).
Some competitive advantages from laser welding include improved product quality, faster process speeds, achievement of difficult product weld geometries and dis-similar materials. The products most suited to laser welding include high value (low volume) components, high volume components and products not able to be produced by any other process.
Some disadvantages of lasers in SMEs:
The main disadvantages of laser welding systems centre on mobility, flexibility and cost. Firstly, the mobility of a laser welding system is limited. As a laser welding system is usually a fixed installation requiring guarding, chillers, materials handling systems, it is difficult to move to another site. However, some smaller compact systems are semi-mobile for on-site jobs and projects.
The second disadvantage is the flexibility of a welding system to weld different parts and geometries. Generally high volume products result in a dedicated laser facility. A dedicated laser facility can require substantial re-tooling costs for different products. These costs need to be added to product prices. Where as high quality (low volume) products require a facility that can accommodate a number of different products.
The final disadvantage is the capital cost of a laser welding system. The cost for a laser welding system can range from a few hundred thousand dollars to millions of dollars. This cost can be accommodated in the prices for a high volume and high value product environment. However, the capital cost is very difficult to justify if the product is outside the high volume/value/quality product category.
To summarise:
Why would SME’s consider lasers? There are three reasons for using laser welding. The first is that laser welding can produce parts not possible by any other process. There are productivity improvements in weld quality and speed. They should also be considered for high quality, high volume and high value components.
What are the advantages (and disadvantages) of lasers? The main advantages include technology enablement, productivity and competitiveness. The disadvantages include lack of mobility, some lack of flexibility compared to traditional MIG and TIG welding and cost justification.
What criteria would laser welding (processing) fulfil? The best use of laser welding equipment is for high volume/value/quality components.
A typical laser processing installation includes a laser system, optics (beam delivery), power supply, chilled water supply, materials handling system (robot/X-Y table/gantry/cranes/etc) and guarding. In addition, staff training and/or access to technical knowledge is required.
Notes: This article first appeared in the WTIA Publication — Australian Welding Volume 51, Fourth Quarter, 2006. Authors were Andrew Gotley — General Manager and John Grace — Managing Director, Raymax Applications Pty Ltd.
www.raymax.com.au
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