{"id":6223,"date":"2024-01-18T09:50:58","date_gmt":"2024-01-18T09:50:58","guid":{"rendered":"https:\/\/cowinextrusion.com\/?p=6223"},"modified":"2024-01-26T08:30:48","modified_gmt":"2024-01-26T08:30:48","slug":"understanding-the-impact-of-key-parameters-on-the-screw-extrusion-process-and-performance","status":"publish","type":"post","link":"https:\/\/www.cowinextrusion.com\/it\/understanding-the-impact-of-key-parameters-on-the-screw-extrusion-process-and-performance\/","title":{"rendered":"Comprendere l'impatto dei parametri chiave sul processo di estrusione a vite e sulle sue prestazioni"},"content":{"rendered":"<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_89 counter-hierarchy ez-toc-counter ez-toc-grey ez-toc-container-direction\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Indice dei contenuti<\/p>\n<label for=\"ez-toc-cssicon-toggle-item-6aea099005a12\" class=\"ez-toc-cssicon-toggle-label\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewbox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewbox=\"0 0 24 24\" version=\"1.2\" baseprofile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/label><input type=\"checkbox\"  id=\"ez-toc-cssicon-toggle-item-6aea099005a12\"  aria-label=\"Toggle\" \/><nav><ul class='ez-toc-list ez-toc-list-level-1' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/www.cowinextrusion.com\/it\/understanding-the-impact-of-key-parameters-on-the-screw-extrusion-process-and-performance\/#Extruder_Screw_diameter\" >Estrusore Diametro della vite<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/www.cowinextrusion.com\/it\/understanding-the-impact-of-key-parameters-on-the-screw-extrusion-process-and-performance\/#Extruder_Screw_length-diameter_ratio\" >Estrusore Rapporto lunghezza-diametro della vite<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/www.cowinextrusion.com\/it\/understanding-the-impact-of-key-parameters-on-the-screw-extrusion-process-and-performance\/#Compression_ratio\" >Rapporto di compressione<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/www.cowinextrusion.com\/it\/understanding-the-impact-of-key-parameters-on-the-screw-extrusion-process-and-performance\/#Spiral_rising_angle\" >Angolo di risalita della spirale<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/www.cowinextrusion.com\/it\/understanding-the-impact-of-key-parameters-on-the-screw-extrusion-process-and-performance\/#Pitch_and_groove_width\" >Passo e larghezza della scanalatura<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/www.cowinextrusion.com\/it\/understanding-the-impact-of-key-parameters-on-the-screw-extrusion-process-and-performance\/#Groove_depth\" >Profondit\u00e0 della scanalatura<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/www.cowinextrusion.com\/it\/understanding-the-impact-of-key-parameters-on-the-screw-extrusion-process-and-performance\/#The_gap_between_the_screw_and_the_barrel\" >Lo spazio tra la vite e la canna<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"https:\/\/www.cowinextrusion.com\/it\/understanding-the-impact-of-key-parameters-on-the-screw-extrusion-process-and-performance\/#Screw_head_structure\" >Struttura della testa della vite<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-9\" href=\"https:\/\/www.cowinextrusion.com\/it\/understanding-the-impact-of-key-parameters-on-the-screw-extrusion-process-and-performance\/#The_number_of_heads_of_the_screw_thread\" >Il numero di teste della filettatura della vite<\/a><\/li><\/ul><\/nav><\/div>\n\n<p class=\"wp-block-paragraph\">I parametri principali del <a href=\"https:\/\/www.cowinextrusion.com\/it\/prodotto\/screw-elements\/\">vite<\/a> sono il diametro, il rapporto lunghezza-diametro, il rapporto di compressione, il passo, la larghezza della scanalatura, la profondit\u00e0 della scanalatura, l'angolo dell'elica, lo spazio tra la vite e il cilindro, ecc.<\/p>\n\n\n\n<h2 class=\"wp-block-heading has-medium-font-size\"><span class=\"ez-toc-section\" id=\"Extruder_Screw_diameter\"><\/span><strong>Estrusore Diametro della vite<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Il diametro della vite \u00e8 il diametro esterno della filettatura e la capacit\u00e0 produttiva dell'estrusore \u00e8 approssimativamente proporzionale al quadrato del diametro della vite; a parit\u00e0 di altre condizioni, il diametro della vite aumenta leggermente, causando un aumento significativo del volume di estrusione e il suo impatto \u00e8 persino maggiore dell'aumento del numero di giri della vite sul volume di estrusione. Pertanto, il diametro della vite viene spesso utilizzato per caratterizzare i parametri tecnici delle dimensioni dell'estrusore.<\/p>\n\n\n\n<h2 class=\"wp-block-heading has-medium-font-size\"><span class=\"ez-toc-section\" id=\"Extruder_Screw_length-diameter_ratio\"><\/span><strong>Estrusore Rapporto lunghezza-diametro della vite<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Il rapporto tra la lunghezza della parte operativa della vite e il diametro della vite \u00e8 chiamato rapporto lunghezza-diametro e, quando altre condizioni sono certe (come il diametro della vite), aumentare il rapporto lunghezza-diametro significa aumentare la lunghezza della vite. L'ampio rapporto di aspetto e la ragionevole distribuzione della temperatura favoriscono la miscelazione e la plastificazione delle materie plastiche; inoltre, il tempo di riscaldamento della plastica nella botte \u00e8 pi\u00f9 lungo e la plastificazione della plastica sar\u00e0 pi\u00f9 adeguata e uniforme, in modo da migliorare la qualit\u00e0 della plastificazione.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Partendo dal presupposto che i requisiti di qualit\u00e0 della plastificazione rimangono invariati, la velocit\u00e0 di rotazione della vite pu\u00f2 essere aumentata dopo l'incremento del rapporto lunghezza-diametro, aumentando cos\u00ec la quantit\u00e0 di plastica estrusa. Tuttavia, se si sceglie un rapporto di aspetto eccessivamente grande, la potenza consumata dalla vite aumenter\u00e0 di conseguenza, aumenter\u00e0 la difficolt\u00e0 di lavorazione e di assemblaggio della vite e del cilindro, e aumenter\u00e0 anche la possibilit\u00e0 di piegatura della vite, che causer\u00e0 lo sfregamento della parete interna della vite e del cilindro e ridurr\u00e0 la durata di vita.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">In addition, for heat-sensitive plastics, excessive aspect ratios can be thermally decomposed due to long residence time, which affects the plasticization and extrusion quality of plastics. Therefore, the selection of the aspect ratio should be determined according to the physical properties of the processed plastics and the extrusion quality requirements of the product.<\/p>\n\n\n\n<h2 class=\"wp-block-heading has-medium-font-size\"><span class=\"ez-toc-section\" id=\"Compression_ratio\"><\/span><strong>Rapporto di compressione<\/strong><strong><\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Compression, also known as the geometric compression ratio of the screw, is the ratio of the volume of the first screw groove in the screw feeding section to the volume of the last screw groove in the homogenization section. It is determined by the physical compression ratio of the plastic &#8211; that is, the ratio of the density of the part to the performance density of the incoming material. The large compression ratio allows the granular plastic to be fully plasticized and compacted. When the type of plastic being processed is different, the choice of compression ratio should also be different.<\/p>\n\n\n\n<h2 class=\"wp-block-heading has-medium-font-size\"><span class=\"ez-toc-section\" id=\"Spiral_rising_angle\"><\/span><strong>Angolo di risalita della spirale<\/strong><strong><\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">The spiral angle is the angle between the thread and the screw cross-section. If the helix angle is too large, the plasticizing time can not be guaranteed, and the plasticizing quality of the screw will be reduced, and if it is too small, the volume of the screw groove will be reduced, which will affect the extrusion amount. For the feeding section, the 30\u00b0 helix angle is most suitable for the powder; The 15\u00b0 helix angle is suitable for square grains; The helix angle of about 17\u00b0 is suitable for spherical or columnar grains.<\/p>\n\n\n\n<h2 class=\"wp-block-heading has-medium-font-size\"><span class=\"ez-toc-section\" id=\"Pitch_and_groove_width\"><\/span><strong>Passo e larghezza della scanalatura<\/strong><strong><\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">The pitch is the axial distance of the thread, and the groove width is the groove width perpendicular to the ridge. When other conditions are equal, the change of pitch and groove width not only determines the helix angle of the screw, but also affects the volume of the groove, thus affecting the extrusion amount and plasticization degree of the plastic. The increase of the width of the screw groove means that the width of the screw edge decreases, the volume of the screw groove increases accordingly, and the extrusion volume increases. At the same time, the width of the screw edge is reduced, and the frictional resistance of the screw rotation is reduced, so the power consumption is low.<\/p>\n\n\n\n<h2 class=\"wp-block-heading has-medium-font-size\"><span class=\"ez-toc-section\" id=\"Groove_depth\"><\/span><strong>Profondit\u00e0 della scanalatura<\/strong><strong><\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">The depth of the groove is the difference between the outer radius of the thread and the radius of the root. According to the requirements of the compression ratio, the groove depth of the feeding section is greater than that of the molten section, and the groove depth of the molten section is greater than that of the homogenization section.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The deep screw groove of the feeding section is large, which is conducive to improving its conveying capacity; However, if the groove depth is too deep, the strength of the screw will decrease, resulting in the screw shearing under the action of greater torque; Second, it is too deep to make the plastic unevenly mixed and stirred unevenly between the tanks, which affects the heat conduction and thermal balance, and leads to the reduction of the plasticizing capacity of the screw.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The screw groove in the molten section and the homogenization section is gradually shallow, and the screw produces a higher shear rate on the material, which is conducive to the heat transfer from the cylinder wall to the material and the mixing and plasticization of the material. However, if it is too shallow, the volume of the screw groove decreases, which directly affects the extrusion volume.<\/p>\n\n\n\n<h2 class=\"wp-block-heading has-medium-font-size\"><span class=\"ez-toc-section\" id=\"The_gap_between_the_screw_and_the_barrel\"><\/span><strong>Lo spazio tra la vite e la canna<\/strong><strong><\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">The gap between the screw and the barrel is half of the difference between the inner diameter of the barrel and the outer diameter of the screw. The size of the gap between the screw and the barrel has a great impact on the quality and output of extrusion, especially for plasticization.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">When the gap between the screw and the barrel is too large, especially when the gap in the homogenization section increases, the counterflow and leakage phenomenon of the plastic increases, which not only causes the fluctuation of extrusion pressure and affects the extrusion amount, but also causes the plastic to overheat due to the increase of these refluxes, which is the result of the aggravation of friction, this overheating, especially in the environment of poor heat dissipation, often leads to the decomposition of the plastic, resulting in poor plasticization and difficult molding. Therefore, the gap between the screw and the barrel is generally controlled at 0.1~0.6mm.<\/p>\n\n\n\n<h2 class=\"wp-block-heading has-medium-font-size\"><span class=\"ez-toc-section\" id=\"Screw_head_structure\"><\/span><strong>Struttura della testa della vite<\/strong><strong><\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">The shape and geometric size of the screw head determine whether the material can enter the machine head from the screw in a balanced manner, and whether it can avoid stagnation, so as not to avoid the thermal decomposition of local materials due to too long heating time.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Different shapes of the screw head will cause the plastic to flow differently from the screw into the machine head. The head of the screw is often shaped with a cone with a small cone angle, and in order to increase the stirring effect, a continuous thread with the screw homogenization section can be made on the cone shape.<\/p>\n\n\n\n<h2 class=\"wp-block-heading has-medium-font-size\"><span class=\"ez-toc-section\" id=\"The_number_of_heads_of_the_screw_thread\"><\/span><strong>Il numero di teste della filettatura della vite<\/strong><strong><\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">When other conditions are the same, compared with the single-head thread, the multi-head thread has a greater positive thrust on the material, the ability to transport the material is stronger, and the backflow phenomenon of the plastic melt can be reduced. However, when all the threads are multi-head threads, it will easily cause fluctuations in extrusion volume and pressure fluctuations due to the melting and homogenization of each screw groove or the inconsistency of the melt conveying capacity, which is not conducive to the extrusion quality. Therefore, sometimes just to improve the ability of the feeding section to convey materials, double-ended threads are set in the feeding section to improve the conveying capacity of plastic particles.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full is-resized\"><img decoding=\"async\" width=\"685\" height=\"228\" src=\"https:\/\/cowinextrusion.com\/wp-content\/uploads\/2024\/01\/Screw.jpg\" alt=\"Vite\" class=\"wp-image-6224\" style=\"width:781px;height:auto\" srcset=\"https:\/\/www.cowinextrusion.com\/wp-content\/uploads\/2024\/01\/Screw.jpg 685w, https:\/\/www.cowinextrusion.com\/wp-content\/uploads\/2024\/01\/Screw-300x100.jpg 300w, https:\/\/www.cowinextrusion.com\/wp-content\/uploads\/2024\/01\/Screw-600x200.jpg 600w\" sizes=\"(max-width: 685px) 100vw, 685px\" \/><\/figure>\n<\/div>\n\n\n<p class=\"wp-block-paragraph\"><\/p>","protected":false},"excerpt":{"rendered":"<p>I parametri principali della vite sono il diametro, il rapporto lunghezza-diametro, il rapporto di compressione, il passo, la larghezza della scanalatura, la profondit\u00e0 della scanalatura, l'angolo dell'elica, lo spazio tra la vite e il cilindro, ecc.<\/p>","protected":false},"author":1,"featured_media":6227,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[41],"tags":[],"class_list":["post-6223","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-knowledge"],"_links":{"self":[{"href":"https:\/\/www.cowinextrusion.com\/it\/wp-json\/wp\/v2\/posts\/6223","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.cowinextrusion.com\/it\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.cowinextrusion.com\/it\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.cowinextrusion.com\/it\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.cowinextrusion.com\/it\/wp-json\/wp\/v2\/comments?post=6223"}],"version-history":[{"count":0,"href":"https:\/\/www.cowinextrusion.com\/it\/wp-json\/wp\/v2\/posts\/6223\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.cowinextrusion.com\/it\/wp-json\/wp\/v2\/media\/6227"}],"wp:attachment":[{"href":"https:\/\/www.cowinextrusion.com\/it\/wp-json\/wp\/v2\/media?parent=6223"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.cowinextrusion.com\/it\/wp-json\/wp\/v2\/categories?post=6223"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.cowinextrusion.com\/it\/wp-json\/wp\/v2\/tags?post=6223"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}