A deeper look at casting solidification software.
Under increasing pressure to improve quality and reduce expenses, many foundries are turning to advanced software packages. These software packages help foundry engineers reduce or eliminate the need for trial-and-error prototyping.
Using today's software programs, foundry engineers can model casting variables and identify rigging and mold designs that are likely to cause shrinkage, cold shuts or other defects before any tooling is built, much less any metal poured.
Given the ability to evaluate casting designs through solidification software, the question for many engineers is not whether to use it, but which package best meets the needs for their foundry. Finding the best package, however, isn't easy.
There are dozens of commercial software packages available, ranging from PC-run two-dimensional (2-D) programs to sophisticated three-dimensional (3-D) packages that require the power and performance of a supercomputer.
Sifting through the range of packages and performance capabilities available can be challenging. In general, though, the software can be grouped by price, platform and performance.
Purchase cost is probably the least accurate way to evaluate solidification software because it doesn't account for accuracy and capability. A low-cost software package is a waste of money if it doesn't provide the capabilities required. A high-cost software package is also a waste if its advanced capabilities aren't used.
In addition, foundries should be aware of "hidden" costs. These include costs such as: additional software and hardware that may be required, personnel who may be required to operate the software, technical support and software upgrades to provide additional capabilities or handle additional casting processes. Before purchasing or leasing any software, foundry engineers should determine how that package will fit into their current and future operations.
The software packages surveyed in this article run on three types of platforms: DOS-based, 386 or 486 personal computers (PCs), Unix-based workstations and supercomputers. Each has its own advantages, and some companies offer the same product for both high performance machines and PCs.
PCs are the most affordable, but may not provide the computational or visualization performance needed to take full advantage of the software.
Workstations made by Silicon Graphics, Inc., Sun Corp., Hewlett-Packard, Digital Equipment Corp. and IBM provide the performance, but at a moderately expensive price.
The supercomputers made by companies like Cray are among the most powerful and the most expensive systems available.
The actual run-time needed to model an application depends on the computer, software and complexity of the application. Generally, workstations are much faster than the PCs, while supercomputers are much faster than workstations. However, a PC model may achieve a usable result faster than a workstation model, even though the workstation is "faster." Some companies use a supercomputer to perform intense computation and output the data to a workstation for visualization.
In terms of evaluating performance, there are several subcategories to look at, including preprocessing capabilities, calculations, post-processing capabilities, ease of use, visualization and support.
Preprocessing--Choices include 2-D or 3-D representation. A 3-D representation can provide more detail and insight, while 2-D software is less expensive. Some software packages are designed to receive geometry from a customer, eliminating the need for solid modeling. Other software programs contain built-in geometry modeling tools, while others use commercially available CAD software.
Another issue is whether the software uses finite element method (FEM), finite difference method (FDM) or an empirical (geometric) method. Complex shapes can more easily be described using the FEM, but it typically takes longer to run. Empirical-based software is fast, although not as accurate as software using either FDM or FEMs.
Solutions--All software packages model solidification--they just do it in different ways. Empirical-based software packages use approximate calculations, rather than complete solutions. Other software programs use Chvorinov's rules (ratio of volume to surface area) to provide quick solutions. Some software packages just solve heat transfer, while others also solve Navier-Stokes equations to model the entire mold filling process and/or fluid flow once the mold is full.
Highly sophisticated packages account for free surfaces and natural convection effects such as temperature and density variations. They also model conduction, convection and radiation, as well as turbulence. Many are beginning to offer solidification kinetics (micromodeling) capabilities. Some can transfer that information to commercially available stress analysis software packages.
Post-processing--Most packages feature built-in post-processors. However, some provide the ability to use commercially available packages, such as PATRAN, ANSYS or ABAQUS. Advanced solidification software not only models hot spots, but other defects such as microporosity and differences in alloy concentration.
Ease of use--Several packages are designed for use without extensive training by engineers on the foundry floor. Software packages with more sophisticated capabilities often require more specialized training. Advanced ease-of-use capabilities include: built-in, complete materials database, pull-down menus, "soft" buttons (on the screen) instead of keyboard commands and point-and-click mouse operations.
Visualization--Basic solidification software can show temperature, solidification time and critical fraction solidified plots as 2-D color maps. Advanced software packages offer: 3-D capabilities; animation; interactive object slicing; a variety of shading options; full color adjustment; and the ability to visualize transient and nontransient data, including modulus, macroporosity, microporosity, dendritic data, grain size, turbulence and shrinkage by different criteria.
Support--All software companies provide documentation. Other types of support may include: on-site training seminars, telephone/fax support, bulletin boards and direct computer links, worldwide user groups and various consulting and engineering services. Some firms tailor their software programs for specific applications.
By comparing the features and capabilities with their budgets and needs, foundry engineers can find the right software package for their requirements.
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|Title Annotation:||Computers in the Foundry; includes directories of 17 leading solidification packages|
|Article Type:||Cover Story|
|Date:||Jul 1, 1994|
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