Only ten years ago, one type of laser, flowing gas Co2, dominated laser materials processing applications. These applications include, welding, soldering, cutting, hardening, brazing, cladding, and marking of materials (generally metals and/or organics), and the market they serve (materials processing) has declined in recent years, going from 1.7 billion U.S. (2008) to roughly 1 billion U.S. (2009). In a recent article on the stat of this industry, the author posited that giving systems builders a better understanding of the optimal technology for each application, could potentially reduce wastage that can occur when a less-than-optimal or efficient laser is used for a given application.
The variety of laser sources available for laser materials processing has grown, each with its own distinct advantages and processing characteristics. New laser technology developments have made selecting the best one more complex in recent years, consequently laser manufacturers can assist in this market’s recovery by educating customers about the optimum technology for a given project. Currently there are four different technologies leading this sector: sealed CO2 lasers, HPDDls, fiber lasers, and flowing gas CO2 lasers, and, subsequently, the ability to distinguish the operating characteristics and output of each is extremely useful in their selection.
HPDDls are built of diode laser bars (a single bar can potentially produce 100 W). HPDDls offer several advantages:
- Lower operating costs
- Require less electricity
- Low integration costs
- Physically compact/lightweight
- Initial capital cost is typically much lower than for equivalent output
The Sealed Co2 Laser
This sealed laser affords the highest power/size ratio available for a sealed laser, capable of delivering up to 1kW of power. The compact size of these lasers makes them very suitable for integrating with desktop equipment or robotic applications.
Co2s offer several advantages:
- Require no external gas supply, therefore, no gas tanks storage costs or associated downtime
- Can produce high-quality Gaussian beam with a low M2 (<1.2)
- Small focused spot with almost all the laser power in the center beam
- More precise cuts and/or higher cut speeds
- Highly efficient use of power, minimal electrical consumption
- Naturally produces square wave shaped pulses
For these lasers output power depends on the available pump power and the quality of the fiber (efficiency). They fall into two categories: single and multi-mode. Commercial single mode fiber lasers are particularly useful for “remote welding and cutting,” in which the focusing optics is a significant distance from the surface being worked on.
Fiber lasers offer several advantages:
- Up to 20 kW of power (commercial multi-mode fiber lasers)
- Well-matched spot size suits many applications
- Less complex and less costly (multi-mode fiber lasers versus single-mode )
- Excellent reliability
- Minimal maintenance
- Electrical conversion efficiency that is second only to HPPDIs
- Low cost of ownership
Flowing gas Co2 Lasers
These lasers are available with multi-mode beam and multi-kilowatt output and are well-suited for applications that require more power.
- Lowest purchase price per watt
- Well known performance and maintenance requirements
- Inexpensive refurbished lasers are available
- Electrical inefficiency
- Require external gas and cooling water
- High cost of ownership
- Require substantial space on the production floor
- Can’t be mounted on a robotic arm or gantry, thus can’t be brought close to work area
- Require complex delivery system
Potentially any of the lasers reviewed could be used to serve low brightness applications, but the HPPDl is considered to be the most practical because it offers the lowest capital and operating costs compared to any industrial laser. In many heat treating and cladding processes, the HPDDl is a great advantage. For many welding applications, fiber laser delivery is ideal.
There are several factors to consider in choosing a laser source for higher brightness applications, such as material absorption characteristics, the nature of the laser/material relationship, cutting speed required, as well as cost considerations. Fully understanding each laser’s strengths and weaknesses, vis-à-vis a given application, will enable consumers to better choose the appropriate laser for their particular project.
The author of this article has gathered sources from http://www.coherent.com/applications/index.cfm?fuseaction=Forms.page&PageID=98 & http://www.coherent.com/downloads/UnderstandingMaterialsProcessingLasers.pdf to write this article.