This is the second installment of our blog series on Material Development for EBM: Ferrium C64. For those who have not read the first post introducing both the Ferrium C64 material and the EBM material development process, it can be found here. As discussed in our previous blog, the EBM process includes three steps: Preheat, Melt and Wafer (Supports). Following the development of the preheat theme for Ferrium C64, the next step was to determine the parameters necessary to develop acceptable melt and wafer themes.
Process Tests – Melt Theme
During development of the preheat theme it was possible to run individual experiments without concern of one experiment impacting the next. This was possible because preheat theme development occurred at room temperature inside the EBM chamber so loss of heat during processing was not an issue. In order to conduct melt theme development the testing must be performed at temperature during a typical EBM build process. To evaluate multiple EBM process variables during a build, a Design of Experiments (DOE) was developed. A build model including 16 blocks (simple melt geometry) were organized on the build plate. This model is illustrated in Figure 1 above. A separate melt theme was assigned to each block and two different melt theme parameters (X and Y in the case of Figure 1) were tested at 4 different values. This DOE allowed us to determine how varying the different parameters affected the melt process. Once the build was setup and running, the melt process was monitored to determine if the identified variables needed to be adjusted outside the initially established ranges. During the melt process, we were looking for a smooth consistent melt with minimal sparking and little to no swelling.
Figure 2 below shows the results of the melt theme DOE. The goal of the build was to find the variable combination that produced the best surface quality. For example, in Figure 2, the bottom row of coupons has a better surface finish then the third row, which exhibit a significant amount of surface porosity. The melt study following the build shown in Figure 2 used the parameters of the bottom left coupon to further refine the melt theme.
Process Tests – Wafer Theme
After several melt theme DOE builds, the next step was to introduce the wafer theme. The same DOE build setup was used; however, the parts were floated roughly ¼” above the start plate and supports were generated to connect the parts to the start plate. Multiple DOE builds were run, developing the melt and wafer themes together. Wafer parameters and support geometry (volume, size of teeth) were adjusted to find the optimal theme. This includes supports that fully stabilize the melt (thermally and structurally) and are removable from the parts. Figure 3 below shows the steps of the wafer optimization. The supports in the first build (left) were not sufficient to hold the part, leading to the bottom edges of the block “pulling” off the supports resulting in deformed parts. The supports in the second build (right) could keep the integrity of the melt geometry above them.
Look out for our next blog post where we will discuss the initial testing of our EBM Ferrium C64 material!