59th Technical Conference & Expo Program
TUESDAY, OCT. 9 8 - 8:10 a.m.
.........................................INTRODUCTION
8:10 - 8:45 a.m. .......................................... Paper No. 10 Alan Kavanagh, DePuy Johnson & Johnson Application of CFD Tools to Investigate Pinhole De- fects in Cast Orthopedic Implants This paper presents results of research carried out within
the EU-funded MedCast project entitled Development of Foundry Casting Methods for Cost-Effective Manufacture of Medical Implants (MedCast, GA number 251269).The partnership is led by DePuy Johnson & Johnson and three university collaborators. Computer numerical modelling of the metal pouring process has been used to investigate the mechanisms of entrained inclusions which contribute to high scrap rates and significant manual rework. Mani- festing themselves as pinholes, the defects are uncov- ered in the post-casting automated machining operations when the cast skin is removed. The general purpose CFD package, Flow3D, with particle tracking capability has been applied to the mold filling process to model surface slag within the crucible and the subsequent transport dur- ing mold filling. Ash particles remaining in certain molds after preheating were also simulated during mold filling. The simulated results have been successfully linked to an in-depth foundry study that examined the relationship be- tween the casting position on the tree to the occurrence of the defect. Scanning Electron Microscopy with Energy Dispersive Spectroscopy characterization of the defects are presented. Unfavorable alloy melting and pouring practices combined with incomplete mold burnout have been seen as the main contributing factors to the occur- rence of the defect.
8:45 - 9:20 a.m.
...........................................Paper No. 11 Victor Okhuysen, Cal Poly Pomona University; Robert Voigt, Penn State University Assessment of Measurement Systems for the Dimensional Inspection of Investment Castings The performance of widely used dimensional inspec-
tion equipment and systems used for investment casting dimensional inspection has been studied. Factors that influence dimensional variability have been identified and compared to the current ICI dimensional tolerance guide- lines. In addition the role of tooling allowances and first- article inspection practices on assuring dimensional con- formance have been established. The poor dimensional repeatability and reproducibility of hand-held inspection devices, even when used by experienced operators, sug- gests that these measurement devices are of limited use by investment casters. Coordinate measuring machines (CMMs) have improved dimensional repeatability and reproducibility. However, even the use of CMMs require
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careful inspection strategies for success. First-article in- spection strategies to minimize centering errors are de- scribed. Recommendations for the selection and use of appropriate foundry dimensional inspection equipment are presented.
9:20 - 9:55 a.m. .......................................... Paper No. 12 Tom Branscomb, Buntrock Industries Alternatives for Zircon Stucco and Flour Casting trials have shown Cerabeads 60 sand to be a suc- cessful substitute for zircon sand in many cases, but not 100% of the time. A new product from Itochu Ceratech, Cerabeads 70 has proven to be a more universal solution as a zircon sand substitute. A zircon flour substitute of alumina and alumino-silicates has been tried in produc- tion tests and has proven to be successful. Casting trials are presented.
9:55 - 10:15 a.m. ................................................. BREAK
10:15 a.m. - 10:50 a.m. .............................. Paper No. 13 Al Torok, Precision Propeller Industries; Conrad Holek, Ransom & Randolph Process Optimization & Cost Reduction Through Supplier Collaboration The fact that manufacturing companies are continually
looking for ways to improve their bottom line is not surpris- ing, especially with the current economic climate. Com- panies are challenged to do more with less and increase their competitiveness. This was no different for Precision Propeller Industries (PPI). A recent area of focus at PPI was the evaluation of the use of a high percentage of zir- con in the primary slurries. The price escalations in zircon made this a focus area for potential cost savings through zircon reduction as replacement seemed unlikely. A De- sign of Experiment study was developed between PPI and Ransom & Randolph and extensive lab work was per- formed to provide a basis for process changes that would reduce overall costs and improve shell performance while maintaining the high surface finish requirements for a ma- rine propeller. This paper will present the details surround- ing the various phases of this process optimization and will give the results found to date. The results of the DOE and lab work and the confirmation production results will be discussed as well.
10:50 - 11:25 a.m. ....................................... Paper No. 14 Grant Bradley, Remet UK Kinetics vs Thermodynamics-How Equilibrium States are Established in Investment Casting Waxes In both the waxes and the slurries employed in invest-
ment casting, the control mechanisms involved in the con- tention between kinetically and thermodynamically driven processes are of joint scientific and practical interest. Par-
September 2012
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