Process efficiency measurements in the laser engineered net shaping process
- PDF / 722,668 Bytes
- 10 Pages / 606.24 x 786 pts Page_size
- 86 Downloads / 252 Views
6/1/04
8:27 PM
Page 143
Process Efficiency Measurements in the Laser Engineered Net Shaping Process R.R. UNOCIC and J.N. DuPONT A study of laser energy transfer efficiency, melting efficiency, and deposition efficiency has been conducted for the laser-engineered net-shaping process (LENS) for H-13 tool steel and copper powder deposits on H-13 tool steel substrates. This study focused on the effects of laser deposition processing parameters (laser power, travel speed, and powder mass flow rate) on laser beam absorption by the substrate material. Measurements revealed that laser energy transfer efficiency ranged from 30 to 50 pct. Laser beam coupling was found to be relatively insensitive to the range of processing parameters tested. Melting efficiency was found to increase with increasing laser input power, travel speed, and powder mass flow rate. A dimensionless parameter model that has been used to predict melting efficiency for laser beam welding processing was investigated for the LENS process. From these results, a semiempirical model was developed specifically for the LENS processing window. Deposition efficiency was also investigated and results show that under optimum processing conditions, the maximum deposition efficiency was approximately 14 pct. A semiempirical relation was developed to estimate deposition efficiency as a function of process efficiencies and LENS processing parameters. Knowledge of LENS process efficiencies measured in this study is useful to develop accurate heat flow and solidification models for the LENS process.
I. INTRODUCTION
LASER-engineered
net shaping (LENS*) is a solid
*LENS is a trademark of Sandia National Laboratory, Albuquerque, NM.
freeform fabrication process that has the capability of producing dense, near-net-shaped parts through the use of a computer-aided drawing (CAD). Fabrication of these structures is made possible when a continuous wave Nd:YAG laser is coupled with an underlying substrate to create a molten pool. Powder material is then injected into the molten pool through four nozzles and upon solidification, a metallurgical bond is formed between the substrate and the incoming powder. A schematic illustration of the process can be seen in Figure 1. The component is constructed in a line-by-line, layer-by-layer manner in a shape that is dictated by the CAD model. After the deposition of a single layer, the nozzles, as well as the focusing lens of the laser, are incremented in the () z-direction to begin the deposition of subsequent layers, thereby building the three-dimensional form of the component. Successive layers are deposited atop one another until the three-dimensional part is completed in a layer-by-layer manner. Powders that have not been fused to the workpiece can often be recycled since the entire process is performed in an inert argon environment; however, the powder must first be sifted in order to remove unwanted contaminants and agglomerated powder particles. Research on this rapid prototyping process has thus far dealt with a diverse ran
Data Loading...
