Flowfront Oct. 2003: The magazine of choice for plastics professionals

Moldflow Plastics Laboratories (MPL) offers material testing and related services that are focused specifically on meeting the material data requirements for plastics processing simulations. Since Moldflow first began offering material testing services two decades ago, MPL has built up a wealth of experience and a reputation for innovation. Working closely with customers worldwide as well as Moldflow research and development (R&D) staff, MPL constantly strives to deliver improved testing technologies as well as the material properties data required for accurate CAE analyses.

MPL works closely with the Moldflow product development teams, providing a unique insight into the performance of CAE technology. The MPL project team works on customer-based projects, providing focused customer support and continual assessment and improvement. In addition, Moldflow maintains global partnerships with customers, universities, material suppliers and injection molding machine suppliers, driving innovation in direct response to customer expectations.

Today, Moldflow customers can contact MPL easily through any of the more than 30 sales and support offices located in 14 countries. The company also maintains R&D centers in the United States, Australia, and Europe. MPL facilities are located in Ithaca, New York, US, and Melbourne, Australia, facilitating the close interaction with R&D to which Moldflow is committed.

MPL offers a full range of material testing and data analysis services, with a special emphasis on Moldflow-recommended, injection molding-based test methods. MPL also offers test methods developed to meet C-MOLD material data requirements (C-MOLD was acquired by Moldflow in April 2000). The newly expanded and updated MPL facility in Ithaca significantly increases the company's material testing presence in the US, providing faster and more competitive response to local customers for the complete range of Moldflow material tests.

The newly expanded and updated MPL facility in Ithaca, New York, significantly increases the company's material testing presence in the US.	MPL material testing services include:
	Moldflow Group Tests: MPI / MPA Filling MPI / MPA Filling and Packing MPI Filling, Packing and Shrinkage MPI Filling, Packing, Shrinkage and Mechanical Properties MPI Reactive Molding MPI Underfill Encapsulation	C-MOLD Group Tests: C-MOLD Filling C-MOLD Filling and Packing C-MOLD Filling, Packing and Shrinkage

Moldflow has long recognized the importance of characterizing materials under actual processing conditions in order to obtain the most accurate material properties for use in CAE simulations. MPL has developed innovative material test methods to address these specific requirements. Injection molding machines form an integral part of the MPL material testing strategy.

Moldflow's injection molding simulation software predicts the flow of polymer through mold geometries. Accurate flow analysis requires the most relevant and accurate material rheological data. Moldflow studies have shown that rheological characteristics measured on instrumented injection molding machines yield better simulation results for both filled and unfilled materials.

This view is validated by leading researchers Professor Robert Malloy, of the University of Massachusetts Lowell, and Professor Philip Coates, of the University of Bradford, United Kingdom.

Professor Malloy states, "The overall 'processability' of a polymer or plastic melt is influenced by a variety of factors, but most importantly, by its rheological behavior. A realistic characterization of a polymer melt's shear flow behavior is particularly important for engineers engaged in any type of polymer process design, including injection molding simulations. Obtaining shear viscosity data at the pressures, temperatures, and shear rates associated with the injection molding process is most commonly accomplished using conventional capillary rheometers. These laboratory instruments offer outstanding precision, but their 'melting mechanism' is purely conductive heat transfer. This is unlike injection molding, where both conductive heat transfer and viscous heating during plastication and injection can play an important role (i.e. shear history). Rheological data generated with a more realistic melting mechanism should lead to more realistic process simulation results. This is particularly important for fiber reinforced thermoplastics where the shear history associated with injection and plastication can have a very significant influence on fiber length and, therefore, flow behavior. Injection molding based rheometers also offer a wealth of other advantages. They are especially useful when working with materials where mixing is critical. In addition, the effects of masterbatch additives (added at the hopper) can be easily evaluated. They offer advantages in terms of test time, and these rheometers can be easily automated."

Professor Coates adds to this by stating, "Basically, in-line rheometry (and other in-process measurements which include flow visualization, rheo-optical measurements, ultrasound, Raman, IR and UV spectroscopy) offers information about the polymer under relevant process history conditions (temperature, strain and stress histories), which off-line rheometry certainly does not. This is particularly important for 'process sensitive' materials. Using off-line measurements can, therefore, be very misleading. In-line measurements in injection molding can also allow thermal stability assessments which are not possible using off-line rheometers, where temperature soak times are often several times the typical polymer residence time in normal processing."

MPL recommends injection molding rheometry to generate optimum data for Moldflow simulations.

MPL offers traditional capillary rheometry services for those who need this type of data.

Moldflow Plastics Insight^® (MPI^®) 4.1 simulations allow the use of three types of shrinkage data and models:

Moldflow strongly recommends using the CRIMS model to achieve the best simulation results. The CRIMS technique achieves unprecedented accuracy in the prediction of shrinkage and warpage using the predicted residual in-mold stress to correct the shrinkage predicted during the flow simulation.

Moldflow analyzed more than 20,000 moldings, each with varied process conditions, thickness, or material. The purpose was to compare the accuracy of predictions based on mathematical theory alone and those based on CRIMS. Greater than 85 percent of the predictions based on CRIMS were within 20 percent of the experimental result, whereas less than 15 percent achieved this result for the prediction based on mathematical theory alone.

Mold verification demonstrates the ability of a given material data set and simulation program to predict cavity pressure as compared to experimental molding observations. Plaques are molded on an injection molding machine which is instrumented with cavity pressure sensors. Moldings are performed at the recommended melt and mold temperatures, at various flow rates and multiple part thicknesses, as outlined in a design of experiments (DOE). Flow simulations are performed at each of the molding conditions using the measured flow, thermal, and pvT data. The predicted cavity pressures are compared to the experimental measurements to validate the material data set.

MPL offers a full range of tests for thermoset material characterization, providing thermal conductivity, solid density, specific heat, curing kinetics, and shear viscosity data:

The combination of these tests gives MPL an unparalleled capability to characterize the properties of thermoset materials. Thermoset material data is required for MPI/Reactive Molding, MPI/Microchip Encapsulation, and MPI/Underfill Encapsulation simulations.

Moldflow Plastics Laboratories (MPL) is committed to strengthening its ties to the material supplier community in the interests of providing Moldflow customers with the broadest range of high-quality data for CAE simulations. The Web-based MPL/Data Fitting utility gives material suppliers the ability to create material data files that can be imported directly into Moldflow Plastics Insight and Moldflow Plastics Advisers^® (MPA^®) software.