An analytical model of energy distribution in laser direct metal deposition

The direct metal. deposition (DMD) process is suitable for functional rapid prototyping, rapid tooling and part refurbishment, and can be operated with CO2, Nd:YAG (neodymium-doped yttrium aluminium, garnet) or high-power diode lasers. In this work, a quasi-stationary coaxial DMD system is modelled-in terms of power balances. Novel modelling methods and matching to experimental results are used to derive a series of equations, from which the power distribution, melt pool length and mean melt pool temperature can be derived for different initial laser powers, system parameters and build material properties. The model is applied to a real system and predicts results in agreement with established values. The model highlights laser radiation reflection from the melt pool and conduction to the substrate as the major power distribution routes and reveals the importance of evaporation losses from the melt pool at higher laser powers. Application of the model is able to explain some of the differences in the process found when using alternative types of lasers as the power source.