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Measurement and modelling of wall friction in the ram extrusion of stiff microcrystalline cellulose-based pastes

Accepted version
Peer-reviewed

Type

Article

Change log

Authors

Ayton, HC 
Rough, SL 
Sutcliffe, MPF 
Müller, P 
Schäfer, J 

Abstract

Simulation of paste extrusion requires knowledge of the material–wall interactions and bulk deformation behaviour. A systematic approach to decoupling these is presented for a stiff paste, comprising microcrystalline cellulose/calcium carbonate/water, employing three different experimental configurations to separate paste-wall friction from bulk rheology. The bulk yielding behaviour was identified from ram extrusion testing with orifice dies, while wall friction was characterised using the twin-die extrusion apparatus reported by (Bryan et al., 2018). Further extrusion tests with square and conical entry dies featuring various die land lengths provided data for comparison with simulations. The wall friction exhibited non-linear Navier slip with negligible pressure dependency: this relationship was included within a solid mechanics-based simulation of ram extrusion with ABAQUS. The estimate of the plastic yield stress from orifice die testing was refined using simulations of flow through square-entry dies and predicted the extrusion pressure for conical-entry dies with reasonable accuracy.

Description

Keywords

Extrusion, Modelling, Paste, Wall slip

Journal Title

Powder Technology

Conference Name

Journal ISSN

0032-5910
1873-328X

Volume Title

377

Publisher

Elsevier BV
Sponsorship
Ceratizit Austria GmbH