Ultrasonic Casting Inspection Solution

QCC was able to produce a finished part through additive manufacturing with the highest consistent dimensional accuracy of any process that Elliott has attempted.

Acquisition Instrument Open-Ended

Platform for Flexible Configurations

Material Velocity Flaw Testing

Immersion or Bubbler

to identify a source to print the cores. QCC does not own a 3-D sand printer and instead has relied on a small group of vendors to produce sand cores and sand molds. The engineering teams agreed on a core design which would allow the core package to be printed as a single unit. This would create uniformity in the spacing and angle of the vanes. The vanes would be inserted directly into the core at the foundry, after which the entire core package could be placed in the drag with the vanes in them. Once the design was set, QCC placed the order for the core with a vendor that could print the cores. In addition to 3-D printing

the cores, QCC also developed a series of fixtures to ensure the vanes could be inserted into the core at the appropriate depth before being inserted into the sand mold. Te steel vanes are set at the

appropriate positions and glued into place using a hot glue gun through slots incorporated into the top of the core. Tis ensures the vanes do not move while the core is transferred to the mold. Te molders must also take great care to avoid unneces- sary friction between the vanes and the core so the vanes are inserted snug to the core without rubbing loose any significant amount of core sand. A loose-fitting vane in the core introduces a level of variation in the process that both QCC and Elliott strove to avoid. When the glue is dry, the core is (800) 225-8330

30 | MODERN CASTING August 2017

transferred to the mold to be closed and poured. Metal is then poured around the vanes, locking them into place and producing the diaphragm. Due to the different materials and

section thicknesses present in the fin- ished part, the blasting and cleaning processes had to be specially tailored to remove the core sand while pro- tecting the structural integrity of the part. During the first several months of production, the scrap rate from post-casting processing was higher than either QCC or Elliott was willing to accept, but new processes and close process controls brought the scrap rate down to an acceptable range. QCC was able to produce a finished part through additive manu- facturing with the highest consistent dimensional accuracy of any process that Elliott has attempted. Te method of 3-D printing sand

cores for the vanes in the diaphragm casting has proven to be efficient, cost effective and repeatable. It has allowed the total area variation to be held within +/- 0.5% over the entire 23 blade section. Te former processes had a total area variation of approxi- mately 10%, and Elliott had to manu- ally bend the vanes to get the area back into the acceptable range. Unlike the prior two processes, the 3-D printed cores also enable the tooling to be used for both rotations. Tis has saved a significant amount in tooling costs and ensured repeat- ability in the process. Only minor adjustments (change core prints) are required for the tooling to be used for either rotation.

Despite the initial cost increase associated with 3-D printing, the total cost of these parts has been reduced and the part consistency has been significantly improved, thus demon- strating one of the unique ways 3-D printing can be used in the foundry to improve quality, reduce lead times, and ultimately, save money.

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