# Optimization of AZ91D Process and Corrosion Resistance Using Wire Arc Additive Manufacturing
## 2 Materials and Methods
### Experimental Setup  
The first step in the creation of the WAAM equipment was the development of a motion control system. For this purpose, aluminum frames were used to allow the fabrication of relatively large and heavy components without compromising the structural integrity of the equipment. The system is capable to move in three axes (\(X\), \(Y\), and \(Z\)). Two different frames were created. The first one is used to control the movement of the printing platform in the \(X\) and \(Y\) axes. This frame is placed horizontally, directly over the horizontal plane. The printing bed is belt-driven by two 5V stepper motors (one for each axis). Each axis slides with the use of four barrel-bearings over two steel rods (two bearings per rod), to ensure smooth movement. To hold the substrate in place, a clamping system made from aluminum was created. The \(Z\) axis is controlled by an individual frame. A 12 V motor (used on a Lincoln Electric 140 c MIG welder (Lincoln Electric, Houston, TX, USA)) is used to feed wire. The system is controlled by a couple formed by an Arduino Mega 2650 board and a Ramps 1.4 board (JAMECO Electronics, Belmont, CA, USA). A modified version of the open source firmware Marlin (1.1, Ultimaker, Geldermalsen, NED) is used as operating environment (shown in Figure 1a).  
A Pro-Fusion Dual Arc 82 HFP (Elderfield & Hall, Knoxville, TN, USA) (see Figure 1b) welding machine was selected since it allows the precise control of the current intensity supplied to the system. In low current mode (from 0.1 to 20 Ampere) the parameter can be changed by increments of 0.1 Ampere. When working with higher currents (up to 80 Ampere) the steps become of 0.5 Ampere. The incorporation of \"Pulsation Mode\", in which the current is supplied in alternating on-off intervals, has been found convenient for the reduction of heat affected zones while working with stainless steel. The machine is also equipped with a \"High Frequency\" option, in which the machine sends high frequency pulses through the electrode until a grounded conductive surface is detected. Once a suitable surface is found, an electric arc is automatically started, and the electrode stops emitting high frequency pulses. This mode is highly convenient while printing since the arc will not always remain on. Two different heat sources have been used in this project.  
The created WAAM systems rely on the use of a plasma arc for the melting and fusing of a metallic wire (filler) and a printing bed (substrate). The wire is being fed by 12 V motor through a reinforced conduction line and delivered to the molten metal pool created by the arc. The wire and substrate fuse together while the printing bed moves, creating a 3D line. The final build is affected by several factors, including printing bed speed, wire diameter, arc current density, the position and speed of the wire being fed through. Adjacent lines can be created by directly overlapping the line already printed and the printing path of the new line. Also, lines can be printed upon previous weld lines in order to create 3D structures. WAAM has already proved with our previous work (see Figure 1c,d) that it can produce 3D structured metal. Figure 1c shows 3D structured stainless steel stacked up with 24 lines. Figure 1d shows square shape of 3D printed stainless steel.