Gating - Sprues and Runner

Gates and runners can made using a QuickCast material or fabricated wax material or a combination of both. You would either design the entire model with gates to be built and assembled as a QuickCast pattern, or you could leave the gates out of the model and plan to attach molded or hand fabricated wax gates.

There are significant advantages of using QuickCast for the majority if not all of the gates in your assembly.

  • Consistency from pattern to pattern

  • Assembly time savings

  • Elimination of the autoclave step to remove wax from the mold before burning out the plastic.

QuickCast sprues and runners typically make sense only for very small components where the entire assembly can be built in one piece. If QuickCast sprues and runners are used, and they are made in multiple pieces, it is important that a path for airflow is created between the components during assembly. For example, if a QuickCast pattern is to be glued to a QuickCast sprue, holes should be drilled in each of the mating surfaces and aligned so that when they are glued together, there is a path for airflow from one component to the other. That flow path is critical in the burnout phase of processing.

As normal, gating is to be considered not only for feeding the metal into the cast part, but as structural components during the shelling process.  Over-gating will have advantages for QuickCast patterns – it allows for better oxygen flow throughout the assembly during the burnout process; and adds strength to the assembly to withstand forces during the dipping process.

Because the QuickCast pattern is mostly hollow and filled with air, its density is significantly less than that of slurry. Dipping a QuickCast pattern may be somewhat similar to pushing a beach ball under the surface of a pool. The resulting buoyancy forces stress the attachment points, and if the pattern is not attached securely, the pattern can break away from the sprue. Over-gating increases the ability of the assembly to withstand buoyancy forces. In extreme cases, it may be necessary to add additional strengthening features as well.