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With new MPI version 5.0, 3D simulation predicts the influence of an insert (or the first shot in two-shot molding) on part rigidity and warpage (left). View above shows deflection without taking the insert into account.
Improved part meshing, part modeling, and process simulation in 3D were the focus of new software developments previewed by Moldflow Corp., Wayland, Mass., at this year’s International Moldflow Users’ Group meeting held this May in Frankfurt, Germany. The meeting was attended by 240 users from 25 countries. Moldflow’s user group meetings play a key role in setting priorities for Moldflow’s product development and give customers an opportunity to learn about updates and enhancements to Moldflow’s software. Users at the meeting use M-Vote, a company-designed electronic voting system that captures and correlates product-enhancement requests.
One of the top new features of Moldflow’s enhanced 3D simulation include meshing an insert together with the part and calculating its effect on shrinkage and warpage. Also new is the ability to model the cooling, shrinkage, and warpage of two overmolded materials. There is also 3D simulation of gas-assisted injection molding. These are some of the developments in release 5.0 of Moldflow Plastics Insight (MPI) simulation software, which is being announced this month.
Whereas traditional 2.5D simulation is geared only toward use with thin-walled parts, full 3D simulation is a newer technology that performs true 3D simulation of thick, solid parts and ones that have extreme thickness changes.
There was also news from Moldflow’s new Manufacturing Solutions business unit based in Moorpark, Calif. It will roll out a new version of Moldflow Manufacturing Solutions (MMS 2.0) that will have new automated process set-up, optimization, and monitoring functions.
Advances in 3D simulation
Compared with the previous MPI 4.1 version, MPI 5.0 updates the MPI/3D user interface, solver, modeling and meshing tools, and simulation output, according to Dr. Franco Costa, manager of CAE development at Moldflow’s campus in Melbourne, Australia. Cooling and warpage were two areas upgraded in the latest 3D simulation technology. MPI/3D Cool and 3D Warpage now consider the thermal effects of molded-in inserts. This applies to insert overmolding as well as two-shot or sequential overmolding applications, where the first shot is not yet cold. “We can now fully predict the thermal behavior of both materials,” says Costa.
To simulate a two-shot sequential overmolding process, users previously had to run separate simulations with each material, where the simulation of the second material regards the first material as already “cold”—even though that is not necessarily accurate. Now, the actual temperature result from the first shot is used as the initial insert temperature at the start of the second shot, and the new software can model how both resins cool and shrink in the tool. It also reveals the influence of a metal or plastic insert on overall shrinkage, warpage, and physical properties such as stiffness. Model preparation is easier because there is no need to force a perfectly matching tetrahedral mesh where the part and insert make contact.
There are new capabilities in MPI 5.0 to model the flow of gas in the filling and packing stages in gas-assist injection molding. Use of 3D tetrahedral mesh eliminates the need for special modeling techniques to represent the gas channels, substantially reducing model preparation time and facilitating a more accurate representation of the part. Gas-assist applications that were previously unsuitable for modeling with a midplane mesh can now be analyzed—for example, thick parts like door handles and furniture armrests.
Several other enhancements in MPI 5.0 improve the efficiency of the MPI/3D meshing process and the quality of the resulting mesh. The 3D mesher is now more tolerant of poor surface meshes with long triangle edges and also reduces the total number of tetrahedral elements required to represent a model, thus allowing a 3D analysis to be completed faster.
Also new in MPI 5.0 is a core-shift analysis for both 2.5D and 3D simulations. This new, fully coupled structural analysis is said to be unique in the industry. It analyzes the deflection of the core caused by melt pressure during injection. Core deflection will alter the flow dynamics in the cavity by changing the part thickness. For high-precision parts, core shift can lead to rejects or premature part failure.
A new Fast Fill Solver in MPI 5.0 can be used to run several preliminary filling analyses to quickly review flow patterns and try out different gate locations and numbers of gates. It can also be used to validate the mesh quality.
Improved 2.5D simulation
Moldflow also upgraded MPI/ Fusion, its proprietary form of 2.5D simulation that generates the mesh directly from the 3D model and eliminates the need to create a midplane, thereby reducing modeling time. The software uses a “Dual Domain” approach that models the top and bottom surfaces of the part, then segments the space between the surfaces into 12 invisible layers (or laminae) to produce more accurate results.
The latest Fusion solver has an improved mesh-matching ratio that better conforms the mesh of the top surface to that of the bottom surface. The time to create the mesh has been reduced by 5% to 10% of the overall project time. (Conventional 2.5D midplane analyzers require that a new mesh be created every time the model undergoes iteration, while MPI/Fusion automatically generates the mesh.)
The Fusion technology also now models the sequential valve-gate technology of Synventive Molding Solutions, Peabody, Mass., and now also can model the cooling and shrinkage of two materials in multi-shot molding. The software even accounts for cooling that occurs during a pause in the process between the first and second shot. It can simulate coinjection or micro-encapsulation.
Moldflow Manufacturing Solutions, a real-time machine monitoring system, was just upgraded to version 2.0, which boasts new process set-up, optimization, and monitoring abilities for multi-barrel injection equipment. Other enhancements include tracking of machine-related activities by individual operator—such as data entry for scrap, downtime for flash removal, and changes to mold cavitation or material lots. MMS 2.0 can track more than one operator assigned to a single machine—such as a separate operator for flash removal.
Part of MMS 2.0 is the Moldflow Plastics Expert (MPX) software for automating set-up and monitoring, which also has gained new capabilities in the latest MPX 1.1 version. The system now reportedly better predicts part defects during the filling, velocity, and packing phases based on visual and dimensional defect perimeters defined during set-up and optimization. The module also now optimizes cooling time and has a new cavity-pressure control feature, as well as a new capability to display melt pressure in the nozzle or injection hydraulic pressure.