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.
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.
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.
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.