Product category:
Fluid, thermal, noise and vibration analysis software
News Release from: Flow Science | Subject: Flow-3D
Edited by the Engineeringtalk Editorial
Team on 12 November 2002
Simulation solves tricky gravity casting
problem
Computer simulation of the casting process can save time and money by making it possible for engineers to design more-effective systems reducing waste and speeding production.
Computer simulation of the casting process can save time and money by making it possible for engineers to design more-effective systems reducing waste and speeding production Gemini of Cannon Falls, MN, manufacturer of fine dimensional letters, logos and plaques since 1933, was faced with a difficult design problem for a cast bronze plate recently
This article was originally published on Engineeringtalk on 4 Feb 2002 at 8.00am (UK)
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Gemini approached Flow Science for help in solving the problem through computer simulation.
Simulation can answer many questions and provide detailed insight about numerous aspects of the metal casting process.
Gemini was asked to design an approximately 43 x 34 x 0.35in bronze plaque for one of its customers when it discovered a problem with early solidification and incomplete filling of the thin-walled casting.
The casting is made by pouring the molten metal (the bronze alloy C92200, Navy M bronze, was being used) from a crucible as the cast iron mould is rotated 60 degrees throughout the course of the pour.
Numerous efforts resulted in incomplete filling and metal exiting one of the designed vents.
Further reading
All-round upgrade for CFD software
The latest version of Flow-3D offers users several new and useful physical models and significant improvements to key features of the solver.
CFD software gains six degrees of freedom
Flow Science has made available a major new release of its Flow-3D computational fluid dynamics software.
CFD software adds more modelling options
The latest Flow-3D offers users an advanced new VOF technique, extensions to the powerful general moving objects model introduced last year and numerous other enhancements to users' modelling options.
Failed attempts to correct these problems led the design staff at Gemini to consider another approach: simulation.
Flow Science was contacted about the problem and Flow-3D was put to work.
Using Gemini's design, and after multiple alternatives were identified, an optimum filling was designed and run.
The simulation results, however, were not optimum.
After a fill time of 20s, the minimum fluid temperature was approximately 616C, which is significantly below the solidus temperature for the bronze alloy of 826C.
Approximately 61% of the alloy was solidified by the end of the simulation.
Semisolidified alloy folded back on itself, leaving porosity adjacent to previously solidified alloy as shown in the adjacent picture.
Due to this premature solidification, some of the molten alloy leaked out a top vent before the mould filled.
Most important, however, the mould did not completely fill, most likely due primarily to the leakage out the vent.
After looking at several alternatives, a solution was proposed.
The recommendations were: first to coat the mould to reduce heat losses; secondly to increase the initial mould temperature (the temperature in the design was 700F); thirdly to increase the pouring temperature (the pouring temperature in the design was 2100F); and finally to eliminate the vent opposite the inlet into the cast.
There were some unknowns about the material properties of Navy M bronze, so two simulations were run to bound the problem.
Such flexibility is made easy by the power of modern computers and the robustness of Flow-3D.
In the first case, the same assumptions regarding alloy properties, heat transfer and fill velocity as the first pass were used.
In the second case, some of the assumptions concerning the material properties of Navy M bronze, which are were not fully known, were changed.
There were some differences in results between the two cases.
Mainly, the solidification of the metal at the end of the filling was somewhat lower in the first case, both in total and at the coldest location in the mould.
The key for the customer, however, was that, in both cases, Flow-3D predicted that the cast part would fill completely.
With these results and implementing the changes suggested by the simulations, the customer had the information it needed to proceed with confidence in casting the part.
Simulation can answer many questions and provide detailed insight about many aspects of the metal casting process.
The maximum advantage to be gained from simulation is usually realized by breaking a process down into its basic parts and then asking "what if" questions.
By giving the engineer the ability to test those "what-ifs", Flow-3D was able to solve Gemini's filling and solidification problems with its bronze plaque.
Users are also discovering that simulation can be profitably extended to other areas, such as sand core blowing, lost foam casting, shot cylinder performance, and more.
The key is that numerical simulation offers a fast, cost-effective way to improve cast products.
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