Precision Engineering 34 (2010) 101–112 Contents lists available at ScienceDirect Precision Engineering journal homepage: www.elsevier.com/locate/precision Investigation of laser and process parameters for Selective Laser Erosion E. Yasa ∗ , J.-P. Kruth Department of Mechanical Engineering, Catholic University of Leuven, Celestijnenlaan 300B, 3001 Heverlee, Belgium article info Article history: Received 21 August 2007 Received in revised form 29 October 2008 Accepted 6 April 2009 Available online 18 April 2009 Keywords: Laser erosion Parameter study abstract The process of Selective Laser Erosion (SLE) was investigated to study the effects of different process and laser parameters on the process outputs such as surface quality and erosion rate. The SLE process is a direct method to remove material in a layer-by-layer fashion due to high energy densities provided by the laser beam. In addition to its direct use as a subtractive manufacturing method, SLE may be used in combination with layer-additive techniques such as Selective Laser Melting (SLM). Such combination mainly makes sense when both processes can be performed with the same laser. However, one of the major problems involved in SLE process is the high number of the laser and process parameters (laser power, pulse frequency, scan speed, scan spacing, ambient atmosphere, etc.) and the complexity of the relations between them which has not yet been investigated completely. This paper presents an overview of the laser erosion process with nano-second Nd:YAG laser pulses and the results of several single-factor experiments that were carried out to determine the influence of the major parameters on the depth of erosion per layer and surface roughness. Additionally, the relations between the parameters are studied to investigate the interactions between them. The results from single- factor experiments showed that some relations were highly governed by the power intensity of the laser beam and also that cross interactions between the parameters play an important role on the output characteristics. The paper explains how multiple parameters (spot size, pulse frequency, scan speed, scan spacing) can be combined to define two indirectly controlled geometrical parameters, namely the scan and pulse overlap factors. Those two parameters allow calculating the number of hits of the laser beam on a same location on the workpiece possible which is the first step in physical modeling the topography of the surface left behind. © 2009 Elsevier Inc. All rights reserved. 1. Introduction Lasers find wide applications in manufacturing industry due to their precise operation and flexibility. This holds for laser marking [1], engraving, laser milling [2,3], laser drilling [4–6], laser cutting [7,8], enhancement of surface morphology [9,10] or surface hard- ness, or for the generation of three-dimensional (3D) parts [11]. Yet, laser erosion is a comparatively new technology. It can be used in conjunction with rapid manufacturing (RM) and rapid prototyping (RP) and to machine parts in a wide range of materials including most metals, glass, ceramics and plastics. It is particularly suited for hard materials which cannot easily be machined by conventional manufacturing methods without sacrificing time and cost [12,13]. The Selective Laser Erosion (SLE) process is defined as the removal of material due to the heat provided by the incident laser beam in a layer-by-layer fashion. It is not only used as a self-standing process, but can also be employed to enhance other laser processes such as Selective Laser Melting [14]. ∗ Corresponding author. Tel.: +32 16 322552; fax: +32 16 322987. E-mail address: evren.bal@student.kuleuven.be (E. Yasa). Laser erosion has some advantages over conventional material removal processes as it is a non-contact process; it has microma- chining capability and is applicable to a wide range of materials. Being a non-contact process, there is no mechanical interaction and no tool wear during the process. The diameter of the laser beam can be reduced to as small as a dozen micrometers allowing very small internal radii and fine details to be produced giving SLE capa- bility of micromachining [5,15]. Moreover, it is applicable to any material that absorbs light in a spectrum covering the wavelength of the laser source utilized on the machine. On the other hand, there are some short-comings of the process such as long process- ing times, heat-affected zones, process inefficiency and difficulty in machining vertical walls and the stair-effect, which is inher- ent to the layer-wise production. One of the major impediments in laser erosion is the high number of process and laser parame- ters. Moreover, their influences on the process and the interactions between them have not yet been completely studied and explored. The suitable processing strategies compromise between efficiency and precision [2]. Some studies are investigating the effect of some process param- eters for laser marking applications. Qi et al. studies the effect of the pulse frequency on mark quality through single-factor 0141-6359/$ – see front matter © 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.precisioneng.2009.04.001