Extruder Drag Flow
Calculate the drag flow of a single-screw extruder, Q_d = ½·π²·D²·N·H·sin(φ)·cos(φ), from the barrel diameter D (m), screw speed N (rev/s), metering-zone channel depth H (m) and helix angle φ (degrees). Drag flow is an extruder's main pumping mechanism: the melt is dragged forward by the relative motion between the rotating screw and the fixed barrel, like a screw pushing a nut that cannot turn. This viscous drag is proportional to screw speed and channel geometry, and would be the maximum theoretical flow with no back-pressure. In practice the net flow is the drag flow MINUS the pressure flow (the backflow from die/head resistance). The balance between drag and pressure sets the extruder's operating point on its characteristic curve. Drag flow is the basis of extrusion screw design, the process that makes pipes, profiles, films, sheets, wire and the pellets of nearly all transformed plastic. Enter the diameter, speed, channel depth and helix angle.
Resultado
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Vazão de arraste da extrusora
A vazão de arraste (drag flow) é o mecanismo principal de bombeamento de uma extrusora monorrosca, Q_d = ½·π²·D²·N·H·sen(φ)·cos(φ), a partir do diâmetro do barril D, da rotação da rosca N, da profundidade do canal na zona de dosagem H e do ângulo de hélice φ. O fundido é arrastado para frente pelo movimento relativo entre a rosca, que gira, e o barril, que fica parado — exatamente como um parafuso empurraria uma porca impedida de girar. Esse arraste viscoso é proporcional à rotação e à geometria do canal, e seria a vazão máxima teórica se não houvesse contrapressão. Na prática, a vazão líquida é a vazão de arraste menos a vazão de pressão (o refluxo que a resistência do cabeçote e da matriz empurra de volta canal acima). O equilíbrio entre arraste e pressão define o ponto de operação da extrusora na sua curva característica, e a vazão de arraste é a base do projeto e do dimensionamento de roscas — o processo que produz tubos, perfis, filmes, chapas, fios e os próprios pellets que alimentam quase toda a transformação de plástico do mundo. Informe o diâmetro, a rotação, a profundidade do canal e o ângulo de hélice.
Related Tools
Screw Compression Ratio
Calculate an extrusion screw's compression ratio, CR = H_feed ÷ H_metering, from the channel depth in the feed zone H_feed and the metering zone H_metering. An extrusion screw has three zones: feed (deep channel, receiving solid pellets), compression (transition, channel tapering) and metering (shallow channel, homogenizing and pumping the melt). The compression ratio is how much the channel narrows from inlet to outlet — typically 2:1 to 4:1. This compression is essential: by reducing channel volume it compacts the pellets, expels trapped air (which must vent back through the feed, not go forward) and generates the shear and pressure that melt the polymer by viscous heating (plus barrel heat). The right ratio depends on the polymer: materials melting with large volume reduction and amorphous ones need different ratios from semicrystalline. A wrong ratio causes incomplete melting, air pumping, flow instability (surging) or degradation. It is one of the parameters that define whether a screw suits a given material. Enter the feed and metering channel depths.
Screw Channel Shear Rate
Calculate the average shear rate in an extrusion screw channel, γ̇ = (π·D·N) ÷ H, from the barrel diameter D (m), screw speed N (rev/s) and channel depth H (m). Shear rate is the velocity gradient the molten polymer experiences between the moving screw surface and the fixed barrel, and it is central to plastics processing for a key reason: molten polymers are NON-Newtonian pseudoplastic fluids whose viscosity DECREASES as shear rate rises (shear thinning). Knowing the shear rate lets you estimate the material's real viscosity in the machine (via the power law) and thus pressure, power and viscous heating. Very high shear can degrade the polymer (chain scission by shear and heat); too low leaves melting incomplete. Each polymer has a suitable range. This screw-channel shear rate differs from the (much higher) die shear rate at the exit restriction. It is a basic processing-rheology calculation. Enter the diameter, speed and channel depth.
Screw L/D Ratio (Injection)
Compute the L/D (length/diameter) ratio of an injection or extrusion screw by dividing the effective length by the diameter. It is a central parameter of the plasticizing design: long screws (L/D 20–24) give better melt mixing and homogenization; short ones (L/D < 18) plasticize less but are more robust. It defines melt quality and the ability to process different materials. Enter the screw length and diameter.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.