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The efficiency of a gas turbine engine is determined, in part, by the dimensional conformity of the turbine blades to the nominal design dimensions. Doncasters Precision Castings in Droitwich UK (DPCD) is involved in the development of next generation designs and as feature complexity increases, so does the dimensional variation of the part. The particle size distribution (P.S.D) of the zircon flour used to make investment slurries was found to significantly impact process capability. P.S.D influenced the rheological properties of slurry, shell build, sintering mechanisms and as a result the annulus length of solid equiaxed tip-shrouded turbine blades. The supplier of zircon flour to DPCD was not capable of controlling the P.S.D during the milling process so a blending technique was developed to reduce the variation of the incoming raw material. Implementation of enhanced process control methods significantly improved the DPCD process. Capabilities of the key process measures; plate weight, viscosity flow time, slurry stability and fired flexural strength were increased. As well as reducing dimensional variation, shell related scrap levels were also improved as a consequence of producing a more consistent ceramic mould system. |
