On an F123 Series 3D Printer, there is a setting for the first layer material. This changes if the first layer that is printed is model material or support material. 

The main benefit of printing model material as the first layer is better adhesion. If you are printing in a material, layer resolution, or certain geometry that makes the part more likely to curl, changing this setting to print model material first may provide some benefit. However, the increased adhesion also has a downside - it is very difficult or impossible to remove from the tray. To read more about this, visit GrabCAD's support page and scroll down to the First Layer Material section.

It can be difficult to tell if you are printing with model material first if you are using a white or ivory model material. Since the support material is also white, it is difficult to tell the difference. The telltale sign in that case is that you cannot remove the raft from the build plate. If you are printing with a non-white model material, it is very easy to tell because you will see a non-white material as the first layer.

Changing this setting is simple, but you may need to change it on both the printer and in GrabCAD Print. To do so, follow the instructions and screenshots below: