AlliedSignal Aerospace

Stereolithography (SL) and the QuickCastTM build style provide the winning combination for meeting critical deadlines in AlliedSignal's development of the TFE 731-20 Turbo Fanjet Engine.

The Challenge
Meeting a critical deadline to develop a new engine teamed AlliedSignal with 3D Systems’ stereolithography QuickCast build style to produce a turbo fanjet engine for a Lear 45 Business Aviation Jet. Metal castings, a major portion of the engine, can take up to eight months to produce. To shorten the production time of the casting pattern, Allied turned to rapid prototyping (RP) for generation of an impeller compressor shroud engine component. This part is the static component that provides the seal for the high-pressure compressor in the engine. Three different designs were required for cold rig, hot rig and first engine to test. With its very complex geometries, would the part meet its rigorous test requirements? A cross section in the hack of the compressor shroud made the part very hard to build. Would RP have the ability to produce such a difficult design?

Meeting engine test schedules was critical and budget concerns were at a premium.

The Results
Faced with rapidly approaching deadlines, two RP processes were applied in tandem through representative service bureaus to build the shroud in efforts to quickly produce accurate castable patterns. 3D Systems’ Technology Center utilized their proprietary QuickCast build style for direct production of investment casting patterns. The QuickCast build style and SL proved to have the edge in the following areas:

• More durable patterns
• Improved accuracy
• Better surface finish
• Larger one-piece patterns

Moreover, the alternate RP technology was unable to maintain tolerances or arrive at the foundry intact. In fact, the pattern generated by the QuickCast build style was so accurate that a design revision error in the assembly fixture was easily detected. Use of QuickCast patterns for casting the nickel-base shroud reduced engine development time for this critical path component, slashing the production casting time by eight to ten weeks. A savings of $50,000 for tooling in the three design iterations was also realized.

"New engine programs are lengthy and expensive — RP provides an ideal tool to get our products to market faster."
                                   - Michael Hyduke,
                                   Manufacturing Engineering Sciences Supervisor II,
                                   AlliedSignal Aerospace

The Process
AlliedSignal developed the CAD file for the shroud and forwarded the file to Precision Castparts Corp. (PCC), a foundry located in Portland, Oregon. PCC then created a CAD solid model of the gating and sent both files, converted to .STL file formats, to the Technology Center. After merging the .STL files, the Tech Center built the shroud, complete with gatings, on their SLA 500 system. The completed pattern was then sent on to Precision Castparts to produce the metal casting.

The SL gated pattern was processed through flash-fire without autoclave, since there was very little wax to remove. The end result was a precision shell investment cast metal part produced directly from a SL generated pattern, bypassing the traditional requirements for expensive and time-consuming hard tooling.

The Tools
• Computervision CADDS 4X software
• SLA 500 system
• QuickCast build style

Company Profile
Headquartered in Phoenix, Arizona, AlliedSignal Aerospace Company is a leader in the production of propulsion engines for business aviation and regional airlines, with emerging business across a broad front of new military and commercial applications. The world-class line of turbine propulsion engines built in Phoenix includes turboprop, turbofan, and turboshaft units for commercial and military aircraft, and turbojet engines for expendable military vehicles.