Doug Bartholomew, Samuel Greengard, Glenn Hasek, John Jesitus, Scott Leibs, Kristin Ohlson, Robert Patton, Barb Schmitz, Tim Stevens, and John Teresko contributed to this article. Simulating the flow of plastics into a mold has traditionally been a complex and often time-consuming endeavor, because there are many variables that can affect manufacturability. If the plastic material enters the mold at the wrong temperature, if the material is injected at the wrong locations, or if the plastic's viscosity is too high, the mold will not fill correctly and defective parts will be produced. It has not been until a design is complete that a company finds out whether or not a part can be produced. When problems occur at this stage, changes are not only costly but can knock a company off its time-to-market schedule. One company, Moldflow Corp., is taking the guesswork out of injection molding with its Part Adviser software by allowing the manufacturability of plastic parts to be determined early in the design process. Part Adviser addresses key manufacturing concerns by visualizing filling patterns of parts in the design software, so designers can see how their selected materials will flow into their proposed designs. This solution was designed to fit into the traditional design process by working directly off a solid model produced by many of the leading CAD systems and by not requiring any translation of geometry. By integrating the software with popular CAD systems, such as Pro/ENGINEER and SolidWorks, product designers and engineers can launch Part Adviser by simply clicking on a menu button while in their CAD system. The system then walks the user through each of the plastic-analysis steps. A data library is included to make material selection easy. Once the material is selected, the user defines filling points for the mold and enters other production-related information using a series of menu prompts and dialogue boxes. To make the process easier and more intuitive for design engineers, who by and large are not familiar with injection molding, the software displays a graphical confidence-of-fill diagram. This shows the part in color, designating areas where confidence that the part will fill is high, medium, or low. "With traditional plastics-analysis software, design engineers don't know what to do with all the results," says Peggy Cicalis, marketing manager at Moldflow. "So we created a confidence-of-fill plot that basically interprets the results for them and then gives them a red-light/green-light type of plot to point them in the right direction." As the simulation proceeds, the state of the plastic flow is displayed. If there is a problem, the design engineer can use the simulation as a road map to make changes to the part or in choosing a different material or fill locations. The software's online adviser capability helps users out when they are uncertain about issues regarding materials, fill locations, confidence of fill, air traps, etc. The tips include graphics that clearly illustrate how changes to a design will affect the part's overall produceability. Roland Thomas, vice president of R&D at Moldflow, believes that one of the key benefits of Part Adviser is the fact that parts can be simulated while the design is evolving, rather than waiting until the design is complete. "You can continuously take snapshots and get feedback on the design as it's progressing," says Thomas, "not just at the end." David Ruscak, a principal engineer in R&D at Polaroid Corp., Cambridge, Mass., illustrates how Part Adviser helped his company save valuable time. "When designing a part, we would run it through Part Adviser, and it might say, 'This part will not fill.' At this point, I go back to my design, and I might make one section thicker or add a rib. The tool maker would not have spotted that problem. They would have made the tool and then found out that it didn't fill. At this point, they were probably ready to do a manufacturing pilot, but that's all held up for maybe a week while they figure out what they are going to do. The cost of losing that one week at that point in a project is significant."
Moldflow Corp.Lexington, Mass.