3.2. Design of experiments
Studies were conducted in line with the experiment designs. The three level full factorial design for three factors was utilized and component values of scan velocity and laser power were analyzed. For comparison purposes of the resultant model, a rotatable orthogonal design was prepared and conducted to assess the influence of the resultant scan velocity and laser power.
3.2.1. Three level full-factorial design for three factors
Three level full-factorial design for three factors was prepared assessing the influence of the laser power and components of scan velocity parameter (distance between points (ptdistance),
Fig. 2 – Metallographic specimen sampled from AZ31 magnesium alloy produced using SLM (Specimen no. 6 – central rotatable composite design).
Fig. 3 – Scheme of the three level full-factorial design for three factors.
and exposure time of laser beam at a point (texposure)). Three level design was chosen in order to determine interactions between the analyzed factors and to increase the degree of the polynomial describing the process (Fig. 3).
The determined range of analyzed parameters is shown in Table 2. The design was prepared using Minitab 17 software taking into consideration 27 different experiments (specimens to be created with varying sets of parameters), which was additionally repeated three times.
The results of the conducted experiment enabled to elaborate quadratic function of regression in a standard form Eq. (5):