and variable quantities. This presents a challenge for not only essential castings, but for the tooling required to produce them.
Non-recurring and recurring
costs as well as design and delivery lead times all become important variables in this decision process.
While there
have been numerous efforts to improve the cost and lead time of castings [1, 2, 3, 4], there remains a need to make dramatic improvements in both cost and capabilities of castings for small turbine engines. To address the necessary
improvements, Renaissance Services has worked with the US Air Force Research Laboratory (AFRL) to develop various advanced tooling methods that leverage additively manufactured tooling for low- cost production of castings. The team consists of foundries and small turbine engine programs/OEMs. Included are parts
for rotating and non-rotating
components (rotors, impellers, stators) as well as structural components (casings, housings). Materials range from nickel- based alloys to steel and aluminum. The program focuses on multiple tooling options for the optimal solution to address overall cost, lead time, and technical capabilities.
The tooling
concepts combine 3D-printing of ceramic molds, patterns, and limited life injection dies.
Most importantly,
the tooling approaches have enabled the low-cost production of advanced turbine castings that previously have been extremely difficult and expensive to produce. These include compressor sections
that combine multiple rows
of airfoils into a single casting; and integrally vaned stators with cast-in cooling holes.
1.1 Investment Casting and Ceramic 3D-Printing Many of the component parts used in turbine engines are made from castings; Specifically, investment castings where wax patterns are traditionally used to provide the three-dimensional form of the desired part. As shown in Figure 1, the traditional
investment casting process has many steps and starts with the creation of
Continued on pg 30 Figure 5: Ceramic 3D-Printing: From 3D Cad Model to Nickel Casting August 2023 ❘ 29 ® Figure 4: Small Turbojet Engine – Cast Component Part Families
Figure 3: Casting Process With 3D Printed Ceramic Mold
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