d) In a Selective Laser Melting (SLM) machine, tungsten powder is deposited on a build platform and is melted by a fibre laser. Use the following material properties and conditions to calculate the theoretical energy required to melt 1 kg of tungsten powder, and hence the energy per unit volume in units of J/cm. You should fully define any equations used and show all steps in the calculation. Density of tungsten Melting point of tungsten Average specific heat capacity of tungsten Latent heat of fusion for tungsten Ambient temperature 19250 kg/m 3400 C 134 J/kg K 190 J/g 21 C Given below are example process parameters for building parts from the same tungsten powder in an actual SLM machine, involving discrete exposures separated by point and hatch distances. Show how these parameters may be used to estimate the energy needed to build, layer by layer, a 1 cubic centimetre volume of tungsten, and give the calculated energy per unit volume in J/cm. Laser Power Exposure time Point distance 220 W 3.00 104 s 7.00 x 10-5 m Scan spacing Layer thickness 1.00 10-4 m 56 10-6 m Briefly discuss reasons why the energy per unit mass/volume needed in practice in SLM may be different to the theoretical case, including any assumptions made in either analysis case. [12 marks]