Draw-Down Ratio
Calculate an extrudate's draw-down ratio (DDR), DDR = (D_die ÷ D_product)², from the die orifice diameter D_die and the final product diameter D_product, as the ratio of cross-sectional areas. After leaving the die, the extrudate (a wire, tube, filament) is often PULLED and stretched by a haul-off at a speed higher than the exit speed, reducing its cross-section to the final size. The draw-down ratio is how much the section area is reduced. Drawing not only sets the final size but ORIENTS the molecular chains in the pull direction, which can greatly increase the product's mechanical strength in that direction (used in oriented fibers, tapes and films, far stronger than unoriented material). The draw-down ratio, combined with die swell, sets the relation between orifice size and final product. There are limits: excessive drawing can break the extrudate or cause defects. It is a key parameter in making fibers, monofilaments, small-diameter tubes and wire coating. Enter the die diameter and the final product diameter.
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Razão de estiramento (draw-down)
A razão de estiramento (draw-down ratio, DDR) de um extrudado é DDR = (D_matriz ÷ D_produto)², a razão entre as áreas das seções do orifício da matriz e do produto final. Após sair da matriz, o extrudado — um fio, um tubo, um filamento — é frequentemente puxado e estirado por um sistema de tração (haul-off) a uma velocidade maior que a de saída, reduzindo sua seção até a dimensão final. A razão de estiramento mede quanto a área da seção é reduzida nesse processo. O estiramento não apenas dá a dimensão final, mas orienta as cadeias moleculares na direção do puxamento, o que pode aumentar muito a resistência mecânica do produto naquela direção — princípio usado em fibras, fitas e filmes orientados, muito mais resistentes que o material não orientado. A razão de estiramento, combinada com o inchamento da matriz, determina a relação entre o tamanho do orifício e o produto final. Há limites: estiramento excessivo pode romper o extrudado ou causar defeitos de superfície. É um parâmetro-chave na produção de fibras, monofilamentos, tubos de pequeno diâmetro e no revestimento de fios e cabos. Informe o diâmetro da matriz e o diâmetro do produto final.
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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.
Extrusion Specific Energy (SEC)
Calculate the extrusion specific energy consumption (SEC), SEC = power ÷ mass throughput, from the screw motor power (kW) and the mass throughput (kg/h). The result, in kWh/kg, is the energy to process each kilogram of polymer, and the main ENERGY-EFFICIENCY indicator of an extruder. Since extrusion melts and pumps plastic largely by VISCOUS heating (screw mechanical energy converted to heat by shear), specific consumption directly reflects how well the screw is doing its job. Typical values are 0.1-0.4 kWh/kg, varying with polymer (each has a melting enthalpy), screw geometry, speed and temperature. An abnormally HIGH SEC signals problems — wrong screw, excessive shear (which can degrade the material), poor temperature setting — and energy waste (the largest part of an extruder's operating cost). A very low SEC may indicate incomplete melting. Monitoring SEC is central to efficiency, quality and cutting cost and emissions in plastics processing. Enter the power consumed and the mass throughput.
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.
Blow-Up Ratio (Blown Film)
Calculate the blow-up ratio (BUR) in blown-film tubular extrusion, BUR = D_bubble ÷ D_die, from the film bubble diameter D_bubble and the annular die diameter D_die. Blown-film extrusion makes most of the world's plastic films (bags, packaging, sacks, sheeting): the melt is extruded through an annular die forming a tube, which is then INFLATED with compressed air like an elongated balloon and pulled upward at once, stretching the film in two directions to its final thickness (a few micrometres). The blow-up ratio is how much the tube is inflated relative to the die diameter — typically 1.5:1 to 4:1. It controls molecular orientation in the TRANSVERSE (circumferential) direction: a higher BUR stretches the film more in width, balancing its properties in both directions (transverse by blowing and longitudinal by pulling). The balance between blow-up and draw (pulling) sets the biaxial orientation, which determines the film's strength, stiffness, clarity and tear behavior. Adjusting BUR is a main control variable in making blown films with the desired properties. Enter the bubble diameter and the die diameter.
Screw Degree of Fill
Calculate an extrusion screw's degree of fill, η = (actual flow ÷ drag flow) · 100, from the actual production flow and the screw's theoretical drag flow. Degree of fill measures how much of the screw's theoretical pumping capacity (the drag flow, which would occur with no back-pressure) is actually delivered as real flow — the difference is 'lost' to pressure flow (backflow from die resistance). It is thus a measure of the extruder's volumetric EFFICIENCY and operating point on the characteristic curve: a high fill (near 100%) means little back-pressure (open die, simple product); a low fill means strong back-pressure (restrictive die), with much internal backflow. In gravity-fed (flood-fed) extruders the screw runs full, and degree of fill reflects the drag-pressure balance; in metered-feed (starve-fed, common in twin-screw) extruders, degree of fill is deliberately controlled by the feed rate, decoupling flow from speed and giving independent control of residence time and shear. Knowing the degree of fill helps diagnose the process and optimize productivity. Enter the actual flow and the drag flow.
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.
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.