A flat plate can be manufactured by a new spray deposition method with a reciprocating spray nozzle and moving substrate. The shape and the temperature of the deposit produced by this process is analyzed by numerical method. An integral model for this spray deposition process has been developed and some necessary data of the spray deposition apparatus are measured experimentally.
The model of temperature calaulation consists of three step : atomization, spray and deposition. In atomization step the size distribution of the powder is calculated. In the spray step the cooling of each size droplet is calculated and average droplet temperature at a given spray distance is calculated. In the deposition step the temperature of deposit is calculated. The unique feature of this process is the variation of deposition rate with time due to the variation of the position of the spray nozzle. As deposition rate is varying, the mesh size of the finite difference method also varies. Governing equation of temperature change is 1 dimensional heat conduction equation and solved by Fully Implicit FDM and TDMA.
Deposition rate is oscillating due to the reciprocating nozzle and the peak of each cycle increases to a maximum point and then decreased due to the travelling substrate. The thickness of the deposit is governed by substrate speed and roughness is governed by the reciprocating speed of the nozzle. Since the cooling rate of the deposit is governed mainly by the deposit thickness, the substrate speed is its main controlling factor. Except in a extremely slow case, the nozzle reciprocating speed has little effect on the cooling rate. Because deposition rate is varying, average cooling rate is not uniform across the deposit thickness. The overall cooling rate of the deposit is quite slow and the control of substrate temperature is required.
