Abstract
For plastic processing extruders with grooved feed sections, the design of the feed section by means of analytical calculation models can be useful to reduce experimental costs. However, these models include assumptions and simplifications that can significantly decrease the prediction accuracy of the throughput due to complex flow behavior. In this paper, the accuracy of analytical modeling for calculating the throughput in a grooved barrel extruder is verified based on a statistical design of experiments. A special focus is placed on the assumptions made in the analytics of a backpressure-independent throughput, the assumption of a block flow and the differentiation of the solids conveying into different conveying cases. Simulative throughput tests with numerical simulation software using the discrete element method, as well as experimental throughput tests, serve as a benchmark. Overall, the analytical modeling already shows a very good calculation accuracy. Nevertheless, there are some outliers that lead to larger deviations in the throughput. The model predominantly overestimates the throughputs, whereby the origin of these deviations is often in the conveying angle calculation. Therefore, a regression-based correction factor for calculating the conveying angle is developed and implemented.
Highlights
In terms of quantity, single-screw extrusion is one of the most important processing methods for thermoplastics
Numerical simulations using the discrete element method (DEM) are becoming more widespread for describing solids conveying in extruders because, here, relative movements between the particles are possible per definition
The previously described development of analytical models for describing solids conveying based on mathematical–physical considerations came to a temporary end at the beginning of the 2000s, as numerical simulations based on the discrete element method (DEM) made their way into plastics technology
Summary
Single-screw extrusion is one of the most important processing methods for thermoplastics. There are different analytical calculation methods that take solids conveying mechanisms into account so that no time-consuming trial-and-error experiments have to be conducted. For a better understanding and discussion of the topic, some general theoretical basis on solids conveying in single-screw extruders is given. State of the Art and Historical Development of Treatment of Solids Conveying in Feed. State of the Art and Historical Development of Treatment of Solids Conveying in Feed Sections of Single-Screw Extruders of Single-ScrewSections.
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