Fast & easy flow analysis.

A new generation of analysis software appeals to a wider range of non-expert users. The new products predict moldability at the beginning of the design process - even at the 'napkin-sketch' stage.

Fast and easy are two words not often associated with computer-aided engineering for injection molding. But a new breed of mold-filling simulation software and other moldability-analysis programs is challenging old perceptions with much faster analysis times and set-ups as simple as a half-dozen mouse clicks. These programs, which C-Mold's chief operating officer Peter Medina characterizes as "desktop CAE," even run well on Windows-based personal computers without special graphics capabilities.

The new software is expected to greatly expand the universe of potential users of flow and moldability analysis. Although the new packages are by no means all the same in function and level of simplicity, they generally require less expertise to operate than high-end flow-simulation systems.

The new software packages represent more than just speed and simplicity. They also make moldability analysis and mold-filling simulation possible at the very beginning of the design process, where they can help you weed out or improve unworkable part designs when it is easiest and cheapest to do so. "The highest impact for filling simulation comes when you can use it to drive the design iterations, not just validate what's already been done," explains Ken Welch, v.p. at Moldflow Corp. "It's the difference between fixing problems and preventing them."

The same design-screening advantage goes for preliminary moldability analyses, which can give molders a glimpse of potential manufacturing pitfalls even at the "napkin sketch" stage. "These desktop products raise red flags very early on in the design process," says Medina.

Despite their appeal, no one suggests that the newest desktop analysis tools will meet every need. Users must understand what these tools can and cannot do. "Simplified solutions have their limitations, says Plastics & Computer president Anne Bernhardt, who cautions against the temptation to substitute easy analysis for a proper understanding of the molding process. Still, she agrees there are plenty of applications where faster, simpler, and lower-cost software packages are justified. Bernhardt estimates that more than half of the analysis requests her firm receives are simply to size and balance runner systems. "Why do rocket science when you don't have to?" she asks.

DON'T GET CAUGHT IN THE MESH

The newest generation of filling simulation tools - "Part Adviser" from Mold flow and "3D QuickFill" from C-Mold - outwardly have much in common, including price tags under $5000. Both programs work off a CAD solid model. Both already have been integrated into a wide variety of 3D CAD packages, enabling an analysis to be run within the design environment. Both products also allow users to run the software on a Windows-based PC as a stand-alone package. Users simply import an .STL file of the solid model, so even molders without CAD solids can use them.

According to their developers, Part Adviser and 3D QuickFill often clock in with analysis times well under 10 min, including set-up time. And these programs spare users all the specialized preparation steps required for a traditional filling analysis. At no point in the analysis does the user have to create, view, or repair a finite-element mesh. All they have to do with both programs is define one or more gate locations (using mouse clicks), select a material, and hit a single key to launch the analysis.

Neither program, however, allows users to transfer these .STL files directly into a midplane mesh for a more detailed simulation. For that you'd have to go back to the original CAD solid model.

Both Part Adviser and 3D QuickFill have limitations when it comes to detailed simulation work. Analysis tasks such as cooling, warpage, shrinkage, and fiber-orientation analysis, as well as gate-sizing tasks and simulation of injection-compression molding, profiled injection, or post-filling are still left to the high-end products. Nor do the simplified programs have what it takes to do much mold design. For example, gate sizes can't be specified in either Part Adviser or 3D QuickFill. (However, C-Mold's Medina reports that some users get around this limitation by modeling the sprue, runner, gate, and cavity as a unified solid. The only problem with this approach has been that the predicted pressure in the runner and gate tends to be underestimated by roughly a factor of two).

Moldflow's Welch concedes these limitations, but notes that a more detailed analysis can be performed later, if necessary, to optimize a design as it reaches completion. "It's a matter of having the right tool for the right time," he says.

Medina also makes a distinction between the level of detail needed to quickly evaluate designs and that needed to solve complex molding problems. "3D QuickFill targets people who are short on time but need to make decisions based on sound technology," he says.

CAE vendors insist that although the "fast-and-easy" simulation programs based on CAD solid models provide less detailed results than their high-end products, they are every bit as accurate. While the products are too new to have accumulated real-world user feedback comparable to the more established simulation packages, Moldflow and C-Mold do publish validation information on their Web sites (www.moldflow.com and www.cmold.com).