Dear Poonam,

I recommend you do first calibration measurement with the polymer, the viscosity of which you know, and then according to the scheme proposed by Johan.

Dear Poonam,

I recommend you do first calibration measurement with the polymer, the viscosity of which you know, and then according to the scheme proposed by Johan.

Thanks for your responses. My feed material is a a mixture of flour. So the product coming out of the extruder will be either in puffed form or as cylindrical ribbons. 

The product will be solid. Inside the barrel due to high pressure and temperature,starch will gelatinize and the material will be plasticised. 

Right, there are so many material modification inside the extruder, including starch metling - and not gelatinizing - that you should not expect too much from raw in line measurements, although torque measurement - or motor amperage (intensity of the electric current) -give you the SME. Conversely, there is an abundant litterature on shear viscosity of flours (power law) and its dependence on water content and temperature, which can help you to compute from your processing conditions.

If you do need a true measure of viscosity, then I suggest you look at

http://www.npl.co.uk/publications/in-line-measurement-of-shear-viscosity-using-an-injection-moulding-machine     in which the nozzle of the injection moulding machine (and thus harder to implement than an extruder) is instrumented to determine viscosity. Its not quite in the barrel, but immediately on exit of the barrel.

There are several transitions inthe screw. If there is temperature effect,you should make some real rheological measurements at estimated shear rate in function of temperature.

Polymers are often shear thinning material, so make attention to verify the behavior with shear rate at a fixe temperature.

In principle, the extruder can be adapted to yield real-time torque monitoring, which, if correlated with off-line rheological data obtained trough laboratory essays, could provide reasonable on-line estimates of the rheological data. The recursive least squares algorithm with forgetting factor or a Kalman filtering based approach might be considered for this purpose. For a related estimation strategy, combining agitation with on-line torque measurement for fermenters ─  conceived for energetic optimization and adaptive control ─ you may check: C.M.G.A. Queirós, "Controlo do Oxigénio Dissolvido em Fermentadores para Minimização de Energia Consumida", MSc Thesis, Instituto Superior Técnico, Universidade Técnica de Lisboa, 1997 (in Portuguese); https://www.researchgate.net/publication/233799574_Controlo_do_Oxignio_Dissolvido_em_Fermentadores_para_Minimizao_de_Energia_Consumida?ev=prf_pub

About several parameters that may possibly influence extrusion of ceramic pastes, you may check answers to another question at this forum  ̶  «What are the most important parameters controlling the extrusion of pastes?»: https://www.researchgate.net/post/What_are_the_most_important_parameters_controlling_the_extrusion_of_pastes

Thesis Controlo do Oxigénio Dissolvido em Fermentadores para Minimi...