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New mold-analysis software for beginners & sophisticated users.

Pursuing a two-fold strategy, Mold-flow, Inc. in Shelton, Conn., is coming out with a range of new products aimed at both experienced and entry-level users. As explained by William E. Hicock, North American sales and marketing v.p., one development thrust is toward new products to solve specialized problems for established users, typically at the larger companies that have been Moldflow's major customer base so far. This thrust is evident in new software modules for analyzing gas-assisted injection, shrinkage, molded-in stresses, and molecular or fiber orientation.

Hicock says a second major goal is to make it easier for smaller firms and first-time users to realize the benefits of computerized mold analysis. This is reflected in new economical and easy-to-use products, as well as a trend toward "unbundling" software modules so that users can purchase just what they need now and add more later.


First shown at the K'92 exhibition in Dusseldorf last fall, MF/Quickcheck is a Windows-based graphical version of Moldflow's 2-D analysis package, MF/G. MF/Quickcheck is a standalone module that runs on a 386-type PC and costs only $2500, including a generic materials database (vs. $35,000 for a typical full-featured, single-user package). By creating and analyzing a "strip model" or slice of a part, the program helps the user to quickly identify optimum wall thicknesses and gating numbers, sizes and positions. It also identifies filling-pressure requirements and helps to balance melt flows within a cavity and runner sizes for multiple cavities. Runner balancing can be performed automatically.(22)

Earlier this year, Moldflow also came out with the first unit of a Moldflow Learning Program. Called "Inside the Mold," it's a $500 interactive training package on a diskette. This Windows-based package introduces a potential user to the principles and benefits of flow, cooling and warpage analysis. (23)

At the recent SPE ANTEC meeting in New Orleans, Mold-flow introduced a 237-page, hard-bound book, the Flow Analysis Reference Manual, which describes the theoretical background of computer simulation of injection molding. It's designed to give engineers an understanding of the scientific principles behind flow analysis. These include the key materials properties for flow analysis, governing equations of fluid flow, mathematical models of injection molding, and an introduction to finite-element formulation and numerical solution of the mathematical models. Price is $150. (24)


For more sophisticated users, Moldflow has several new and soon-to-be-released packages addressing specialized needs. As reported previously (PT, May '93, p. 74), Moldflow is about to release commercially its gas-injection analysis module, MF/Gas. Developed in cooperation with Cinpres Ltd. of England, the software will be demonstrated at the Interplas '93 exhibition in Birmingham in November. (25)

Just released is a new finite-element package called MF/Shrink. Priced at around $25,000, it offers new capabilities to Moldflow users. One is predicting shrinkage variations across the mold, displayed as a color-coded "map" of the part. The software can also predict a single average shrinkage value for the moldmaker to use, and highlight in color any areas of the part that would be out of tolerance as a result of local shrinkage variations. For particular critical dimensions, MF/Shrink will predict the specific shrinkage value to be used to ensure that tolerances are met on those dimensions.

Most important, says product marketing specialist Mark S. Toussaint, MF/Shrink relates shrinkage to processing conditions and mold design. It helps the tool designer verify that the chosen processing window, polymer, gate positions, and part geometry will give desired molding dimensions. Typical industry practice has been to pick a single generic shrinkage value from the material supplier's data sheets and then build prototype tooling to determine actual shrinkage. The only other options were to rework the production tool after initial sampling, or else modify processing conditions to give acceptable results. The latter could result in long cycles, sink marks, narrow processing windows, and so on, while the other options add expense and time to product development.

This software has been tested and verified during several years of R&D, by comparing the program's predictions to actual moldings made with a variety of wall thicknesses and process conditions. This package currently runs on engineering workstations, but will be made available for PCs next year. (26)

Another major new introduction from Moldflow is MF/Stress. This package performs a finite-element stress analysis to determine how molded-in stresses will affect the mechanical properties of a part. In other words, it considers how processing affects ultimate mechanical properties and how those properties may vary throughout a part (via color-coded map). If used together with another new package called MF/Fibre, MF/Stress can also relate mechanical properties to fiber orientation in reinforced parts. MF/Fibre predicts fiber distribution and orientation through the thickness of the part, accounting for skin and core differences. It can display both the direction and degree of fiber orientation.

When integrated with Moldflow's existing warpage analysis module known as MF/Warp, MF/Stress can simulate the stresses produced when constraining a warped component within a rigid assembly--for example, a dashboard in a vehicle. Unlike generic finite-element stress-analysis packages, MF/Stress is designed specifically for plastics and contains no irrelevant features, so learning to use it is easier and quicker, requiring few specialized skills, the company says. (27)


Moldflow's latest generation of its MF/Flow software, release 8.1, began shipping in May. As reported previously (PT, April '93, p. 13), it contains numerous features designed to enhance CAD integration and facilitate interpretation of results. For example, it contains a built-in IGES translator to import CAD models. Release 8.1 also has automatic graphical runner balancing, and graphical display of sink-mark predictions.

A menu-driven graphical interface (Motif for workstations and Windows for PCs) has replaced the previous keyboard commands. For example, simulated mechanical "sliders," as are found on a molding-machine control panel, are displayed on-screen for the purpose of programming injection-speed profiles.

New dynamic memory allocation enhances speed by assigning only the amount of computer memory required for the analysis (determined by the number of nodes and mesh elements in a model), thereby increasing computer processing efficiency.

Other new features increase the accuracy of flow analysis. For example extensional and shear pressure drops are now used to calculate entrance pressure losses in small gates and geometric constrictions in a mold. Clamp-tonnage predictions are also enhanced by using pvT/compressibility material data to simulate the common molding practice of stopping the ram before the cavity is completely filled, allowing the compressed melt to expand into the remaining area. (28)


In October, Moldflow plans to issue release 8.2 of MF/Flow. It will have a number of incremental improvements, according to Toussaint, as well as some important advances, upon which he declined to elaborate. Two significant elements of future releases were revealed, however. One will answer users' frequently expressed need for an easier way to convert 3-D solid models to the "2.5-D" mid-plane geometry necessary for mold analysis. Hicock says a future release will automatically convert from solids to mid-plane geometry. A second new feature will extend the software's ability to recommend optimum molding conditions based on shear and other data derived from mold analysis. Such optimization features are currently available in 2-D analysis with MF/G or MF/Quick-check, but soon they will be extended to 3-D finite-element analysis. This will enhance accuracy and also require less expertise on the part of the user to achieve a meaningful result. Also, a future release will automatically recommend gate locations, a feature not available today in any version of the software.

In general, says Hicock, process optimization with "artificial intelligence" will be a major thrust for Moldflow in the future. That is, "taking the expertise of a good plastics engineer and putting it into the software," he says. The company is working on automatic generation of recommended injection-speed profiles. And farther down the road, Moldflow plans to introduce real-time optimization software to modify the actual molding operation based on flow-analysis calculations and in-mold sensors.

The next step in the direction of post-molding analysis (shrinkage, warpage, and stress) will be to predict creep phenomena as a result of molding conditions.

By November's Interplas '93 exhibition in Birmingham, England, Mold-flow plans to introduce MF/TSETS, a version of MF/Flow for thermosets. It will be applicable to injection and transfer molding of epoxy molding compounds and polyester BMC. MF/TSETS has been verified extensively through beta testing in integrated-circuit encapsulation operations, which reportedly have achieved dramatically increased yields in production with the aid of this software.

And farther back in R&D, Mold-flow is investigating prediction of wall-thickness and temperature distributions in blow molding and thermoforming.
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Title Annotation:Technology News: Mold Analysis
Author:Naitove, Matthew H.
Publication:Plastics Technology
Date:Aug 1, 1993
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