PROCESS CONTROL | DIGITALISATION
Right: Leistritz’s in-line rheometer allows process variation to be detected in real-time to optimise or control production
conditions by conducting experiments and comparing the experi- mental results to the model’s results.
Ursula Stritzinger, a re-
searcher at IPEC, is using such a hybrid modeling approach to describe the conveying behaviour and power consumption of kneading blocks. She conducted more than 3,000 numerical simulations to determine the input for the data-based modelling. The resulting models describe the conveying and power consumption parameters. Additionally, she defined two novel parameters to enable the description of non-convey- ing screw elements. Stritzinger reports, for example, that one model was found to accurately predict the drag flow output within ±3%.
optimise blends while a process monitoring version can be used to control the process to the set point. Tight tolerances can be maintained as the data can expose even slight fluctuations
IMAGE: LEISTRITZ
Below: Coperion’s ZSK compounding extruders now use the company’s open-interface CSpro control
Critical data Measurement is crucial for collecting reliable data that can be used in process models. Wolfgang Pössenberger, Sales Director for Rheometers at Leistritz Extrusion, explained in the same seminar that melt quality can vary without the operator being aware due to raw material variation between batches or variable moisture content in fillers, for example. Continuous, in-line measurement solves this problem by allowing operators to detect any changes in melt quality. Leistritz’s inline rheometer, developed with JKU
researchers, measures both shear and elongational viscosity in the melt and data from the rheometer can be exported to various software programs. A research version of the software can be used, for example, to
in the process that have an impact on melt quality and thus product quality, according to Pössenberger. Laurent Ratte, Sales Manager at Sciences Computers Consultants (SCC), says formulation, setup and scale-up in most compounding operations is typically performed using a trial and error approach. He says that computer-based simulation could save both time and money by eliminating these extrusion trials. SCC’s simulation software uses a combination of mathematical models and data generated by
virtual design of experiments to provide optimal operating conditions. “The software highlights the best combinations for a process machine, material, and operating conditions, without additional real trials on the extruder,” according to Ratte. The company’s software is not designed for automated process control, but it provides data analysis so that a process engineer can use this information to make any changes. Citing the example of recompounding of
plastics recyclate, Ratte says that simulation could be used to take into account the variability of the viscosity of the incoming raw material and to anticipate its impact on the final product. He says that SCC is working with R&D centres in academia and industry to collect data on many materials as, with access to sufficient input data, it can develop a model that could be used to optimise the process to meet product quality targets.
User-friendly tools
While the science and engineering behind the models is important, a benefit of applying tools based on Industry 4.0 principles is that software can take them and make them useable for opera- tors. Getting input from users helps to make such tools user-friendly, according to Coperion. The company says in the recent redesign of the graphical user interface (GUI) for the CSpro control used on its ZSK extruders, the designers inter- viewed users and observed how they used the machine on location during compounding. “The challenges facing operators on a daily basis while operating an extruder, as well as proven
18 COMPOUNDING WORLD | August 2021
www.compoundingworld.com
IMAGE: COPERION
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