Abstract
High energy heat sources used to melt and fuse metal are widely used in industry. While laser and electron beam processing have been in use for 50 years or more, and arc welding for more than a century, the fundamentals of these processes are often poorly understood. The increased automation of these metal processing systems further remove the operator or engineer from the basic function and control of these heat sources, the molten pool and ultimately the fused metal deposit. AM metal processing systems often operate within the confines of an enclosed chamber and at high speeds creating extremely small molten pools further obscuring the basic functioning of the process. This chapter describes the basic function of these heat sources, what happens when a high energy beam or arc heats a metal surface to melt and fuse powder or wire into shaped parts. The use of auxiliary and additional heat sources during AM processing and post-processing is introduced.
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Notes
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Figure courtesy of Lawrence Livermore National Laboratory, reproduced with permission.
- 2.
High powered CO2 lasers operating at kilowatt levels were the first to see wide use in metal welding and cutting. The 10.6 micron wave length required reflective optics such as copper mirrors and could not be transported in quartz fibers or windows, limiting their use during the development of the first laser based AM systems. Nd:YAG laser followed first with pulsed beams relying on pulsing flash lamps inside a reflective cavity to pump a laser rod of Nd:YAG doped quartz. Nd:YAG laser could be focused into and delivered by optical fibers and easily passed through windows into glove boxes, adding to their versatility. Flash lamps had a limited lifetime and required alignment and maintenance of optical elements. Lasers using multiple laser cavities and sequential pulsing to create quasi-continuous wave beams were also used in early AM systems. Optical diodes eventually replaced the flash lamps to pump the laser cavity, offering longer lifetimes and reduced service requirements. Disk lasers offered benefits to beam quality and direct diode laser array offered high-efficiency lasers for metal processing such as cladding at the cost of beam quality. The advent of fiber laser technology offered significant improvements in robustness and cost in a compact size.
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Article from EDU.photonics.com, Fiber Lasers New Types and Features Expand Applications, Bill Shiner, IPG Photonics, http://www.photonics.com/EDU/Handbook.aspx?AID=25158, (accessed March 17, 2015).
- 4.
Courtesy of The FABRICATOR, an FMA publication; reproduced with permission.
- 5.
Courtesy of Donald E. Powers under CC BY-SA 3.0: https://creativecommons.org/licenses/by-sa/3.0/.
- 6.
The European Commission report Final Report Summary—FASTEBM (High Productivity Electron Beam Melting Additive Manufacturing Development for the Part Production Systems Market, Project Reference 286695, http://cordis.europa.eu/result/rcn/153806_en.html, (accessed March 17, 2015).
- 7.
Source Dr. Dmitri Kopeliovich, “Plasma Arc Welding (PAW),” Subs Tech substances & technologies, http://www.substech.com/dokuwiki/doku.php?id=plasma_arc_welding_paw. Reproduced with permission.
- 8.
Source Dr. Dmitri Kopeliovich, “Metal Inert Gas Welding (MIG, GMAW),” SubsTech substances & technologies, http://www.substech.com/dokuwiki/doku.php?id=metal_inert_gas_welding_mig_gmaw. Reproduced with permission.
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Milewski, J.O. (2017). Lasers, Electron Beams, Plasma Arcs. In: Additive Manufacturing of Metals. Springer Series in Materials Science, vol 258. Springer, Cham. https://doi.org/10.1007/978-3-319-58205-4_5
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DOI: https://doi.org/10.1007/978-3-319-58205-4_5
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