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Software eases web-gauge control.

A new mathematical model from Eurotherm's Gauging Group in Billerica, Mass., can make diebolt mapping--normally a hands-on, engineering-intensive process--almost as easy as hitting a few computer keys. Introduced just this month, the model is the latest in a progression of software improvements to CIMLine, the company's computer-integrated manufacturing package for flat-web extrusion.

Functioning as part of either a manual or an automatic profile-control system, the Melt Flow Model (MFM) is intended to eliminate the conventional trial-and-error mapping technique--whereby an operator tweaks diebolts and observes the downstream effects on the web as measured by the sensor. The MFM, by contrast, relies on several proprietary algorithms to automatically calculate mapping parameters from known polymer- and die-related flow information. "It's really the first truly deterministic mapping model," says Bob Engel, v.p. of development and marketing.


MFM works by recognizing two distinct regions of the web and applying a different modeling strategy to each one. Engel explains that the edge, or "neck-in," region requires a nonlinear flow analysis to describe its process-and polymer-influenced shrinkage behavior. The web area between these edge regions, by contrast, undergoes mostly a polymer-dependent linear shrinkage, so a different modeling technique is applied here. MFM exercises yet a third set of algorithms to establish the boundaries of these nonlinear and linear zones. At the system's heart are databases containing specific information on polymers and flow characteristics of individual dies.

Touchscreen utilities enable easy configuration of MFM setups, which can be stored as recipes. Die-setup parameters would include the die name, number of bolts, and bolt width, among other things. The polymer setup would include the material name, specific gravity, and additional physical-property information.

Once the appropriate background information has been entered, a user simply presses the "calculate" button. The system then finds the optimal diebolt positioning to maintain a uniform profile. Engel notes that some production situations do not yet fall within the province of the current databases. But he expects the system's applicability to widen over time as the mapping knowledge embodied in its database encompasses more and more real-world situations. Until then, users can dictate their own values for the model to use in its calculations.

MFM's first installation is on a new cast film line from Reifenhauser Inc. of Peabody, Mass. The line produces thick-gauge PP film between 1520 microns as a replacement for PVC in office products.


Also new from Eurotherm are data-acquisition tools for the company's SpectraBeam Full Spectrum Infrared (FSIR) gauging system. This sensor works by monitoring the infrared absorption patterns of the web. Because it can "see" different absorptions for individual components of a multilayer web, it typically serves in coextrusion or extrusion coating.

According to Engel, the software-driven SpectraBeam has always captured the entire near-IR spectrum, but only the final gauging information itself was accessible to the users. Now, the software supporting the system provides access to all the unprocessed sensor data through a Windows,based math package called Matlab from The Math Works Inc. Chief among the advantages, according to Engel, is the ability to conduct continuous on-line adjustments of calibration parameters.

These "dynamic calibrations" use the computerized math tools to automatically calculate and document calibration vectors for specific production runs. The system also provides a means to correlate these on-going calibrations with known standards derived in a lab. "We've decreased the dependency on lab sampling," says Engel. "Now the sensor certifies the product, and the lab only certifies the sensor."The software-driven approach is distinct from earlier IR gauging, which depended not only on laboratory calibrations from hundreds of samples but also on IR filters to adapt the sensor to a variety of web compositions.

Among other recent software updates, Eurotherm has started bundling the CIMLine system with the client/server software that ties together various CIM products. Users essentially just "plug in the pieces," eliminating the need for a professional systems integrator. A related change has been the company's move in the past year to the industry-standard windowing environment called X-Windows, providing a uniform user interface across hardware platforms.
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Author:Ogando, Joseph
Publication:Plastics Technology
Date:Nov 1, 1993
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