{"id":396,"date":"2026-11-06T21:32:00","date_gmt":"2026-11-06T13:32:00","guid":{"rendered":"https:\/\/kerkepm.com\/knowledge\/twin-screw-extruder-startup\/"},"modified":"2026-11-08T20:42:56","modified_gmt":"2026-11-08T12:42:56","slug":"twin-screw-extruder-startup","status":"publish","type":"page","link":"https:\/\/kerkepm.com\/es\/knowledge\/twin-screw-extruder-startup\/","title":{"rendered":"Twin Screw Extruder Startup"},"content":{"rendered":"<div class=\"k3\">\n<div class=\"wrap\"><div class=\"crumbs\"><a href=\"\/\">Home<\/a><span>\/<\/span><a href=\"\/knowledge\/\">Knowledge<\/a><span>\/<\/span>Twin Screw Extruder Startup<\/div><\/div><div class=\"wrap\"><div class=\"hero\">\n<p class=\"kicker\">Operation \u00b7 7 min read<\/p>\n<h1>Twin Screw Extruder Startup: The 9-Step Sequence That Protects the Screw<\/h1>\n<p class=\"dek\">Most screw damage happens in the first ten minutes of a shift, not in the tenth month of service. Here is the sequence we teach at commissioning, with the temperatures and checks that matter. A reference twin screw extruder startup page from Kerke.<\/p>\n<div class=\"byline\"><div><b>Updated<\/b> 6 November 2026<\/div><div><b>Reviewed by<\/b> Kerke process team<\/div>\n<div><b>Basis<\/b> commissioning records, parameter table<\/div><\/div>\n<\/div><\/div>\n<div class=\"wrap\"><div class=\"grid\"><main>\n\n<p class=\"lead\">A twin screw extruder is started hot and empty, brought to temperature under rotation, and only then fed. Skip a step and the result is either a seized screw or a barrel full of degraded polymer that has to be chiselled out.<\/p>\n\n<nav class=\"wp-block-rank-math-toc-block k3-toc\" aria-label=\"On this page\"><b>On this page:<\/b><a href=\"#rm-s1\">The sequence<\/a><a href=\"#rm-s2\">Barrel profiles that work<\/a><a href=\"#rm-s3\">Three startup mistakes that cost the most<\/a><a href=\"#rm-s4\">Shutdown, which is half the story<\/a><a href=\"#rm-s5\">FAQ<\/a><\/nav><h2 class=\"sec\" id=\"sequence\" id=\"rm-s1\">The sequence<\/h2>\n<ol class=\"flow\">\n<li><b>Heat the barrel with the screws turning slowly<\/b>Set every zone to its setpoint and run the screws at 10\u201315 rpm while heating. A stationary screw in a hot barrel bows; a turning one stays straight.<\/li>\n<li><b>Confirm the die and screen are open<\/b>Die heater on, die holes clear, screen changer in the running position. A blocked die during filling raises pressure faster than the safety cut-out can react.<\/li>\n<li><b>Start the pelletizer and water system first<\/b>Water ring: water flowing and at temperature before the first pellet arrives. Strand: water bath filled, air knives on.<\/li>\n<li><b>Feed at 20% of setpoint<\/b>Bring the main feeder up to about 20% and watch the die pressure and melt temperature for two minutes. Torque should settle, not climb.<\/li>\n<li><b>Raise to setpoint in steps<\/b>Increase feed in 20% steps, waiting for melt temperature and torque to stabilise between steps. A single jump to 100% is how gearboxes get shock-loaded.<\/li>\n<li><b>Set vacuum once the melt is stable<\/b>Apply vacuum after the melt seal is established, typically at 60\u201370% feed. Applying vacuum earlier pulls powder into the vent.<\/li>\n<li><b>Trim screw speed against melt temperature<\/b>Adjust rpm to hold melt temperature, not the other way round. On a 65 mm machine, 20 rpm is worth roughly 8\u201312 \u00b0C at the die.<\/li>\n<li><b>Check pellet quality before full rate<\/b>Pellet size, fines and moisture. Fixing pelletizing at 70% output is cheap; fixing it at 100% is a lost shift.<\/li>\n<li><b>Record the settled parameters<\/b>Barrel profile, rpm, feeder rates, vacuum, die pressure, torque and output. That record is the reference for the next start and the baseline for troubleshooting.<\/li>\n<\/ol>\n\n<h2 class=\"sec\" id=\"temperatures\" id=\"rm-s2\">Barrel profiles that work<\/h2>\n<div class=\"tw\"><table>\n<caption><b>Table 1.<\/b> Typical barrel profiles by polymer. Reference values \u2014 always confirm on your own material.<\/caption>\n<thead><tr><th scope=\"col\">Polymer<\/th><th scope=\"col\">Feed zone<\/th><th scope=\"col\">Mixing zones<\/th><th scope=\"col\">Die<\/th><th scope=\"col\">Note<\/th><\/tr><\/thead>\n<tbody>\n<tr><td>PE \/ PP masterbatch<\/td><td class=\"num\">60\u201390 \u00b0C<\/td><td class=\"num\">170\u2013200 \u00b0C<\/td><td class=\"num\">180\u2013195 \u00b0C<\/td><td>Keep the feed throat cool to avoid bridging.<\/td><\/tr>\n<tr><td>ABS \/ HIPS colour<\/td><td class=\"num\">80\u2013100 \u00b0C<\/td><td class=\"num\">190\u2013215 \u00b0C<\/td><td class=\"num\">200\u2013210 \u00b0C<\/td><td>Too hot gives colour streaks, not better dispersion.<\/td><\/tr>\n<tr><td>PA6 \/ PA66<\/td><td class=\"num\">80\u2013100 \u00b0C<\/td><td class=\"num\">240\u2013270 \u00b0C<\/td><td class=\"num\">250\u2013265 \u00b0C<\/td><td>Dry to &lt;0.1% or viscosity falls visibly.<\/td><\/tr>\n<tr><td>PC<\/td><td class=\"num\">90\u2013110 \u00b0C<\/td><td class=\"num\">260\u2013290 \u00b0C<\/td><td class=\"num\">270\u2013285 \u00b0C<\/td><td>Dry 120 \u00b0C \u00d7 4 h; moisture causes splay and IV loss.<\/td><\/tr>\n<tr><td>PVC (rigid)<\/td><td class=\"num\">60\u201380 \u00b0C<\/td><td class=\"num\">150\u2013175 \u00b0C<\/td><td class=\"num\">165\u2013180 \u00b0C<\/td><td>Residence time, not temperature, is the risk.<\/td><\/tr>\n<tr><td>PLA<\/td><td class=\"num\">40\u201360 \u00b0C<\/td><td class=\"num\">170\u2013195 \u00b0C<\/td><td class=\"num\">175\u2013190 \u00b0C<\/td><td>Above 200\u2013210 \u00b0C molecular weight drops in a step.<\/td><\/tr>\n<\/tbody><\/table><\/div>\n\n<h2 class=\"sec\" id=\"mistakes\" id=\"rm-s3\">Three startup mistakes that cost the most<\/h2>\n<div class=\"call warn\"><h4>1. Filling a cold machine<\/h4><p>Feeding before the barrel reaches setpoint packs unmelted powder into the first mixing block. The torque spike either trips the drive or shears a screw element, and the clean-out takes a full day.<\/p><\/div>\n<div class=\"call warn\"><h4>2. Starting with an empty hopper and a closed die<\/h4><p>With no material in the screw, the die heats unevenly; the first melt through a cold die hole freezes and blocks it. Always confirm die heat soak \u2014 20\u201330 minutes above 150 \u00b0C \u2014 before feeding.<\/p><\/div>\n<div class=\"call warn\"><h4>3. Running vacuum during filling<\/h4><p>The vent is designed for melt, not for powder. Vacuum applied during the filling stage pulls filler into the vacuum line, and the line then needs a full clean before it holds vacuum again.<\/p><\/div>\n\n<h2 class=\"sec\" id=\"shutdown\" id=\"rm-s4\">Shutdown, which is half the story<\/h2>\n<p>Purge with a cleaning compound or with the carrier resin alone, at reduced feed, until the extrudate runs clean. Then stop feeding, keep the screws turning at 10\u201315 rpm while the barrel cools to below 150 \u00b0C, and only then stop rotation. Leaving a filled screw to cool in a hot barrel is the second most common cause of a seized machine.<\/p>\n\n<h2 class=\"sec\" id=\"faq\" id=\"rm-s5\">FAQ<\/h2>\n<details open><summary>How long should the barrel heat soak before feeding?<\/summary><p>Until every zone holds setpoint for at least 20 minutes, typically 45\u201360 minutes from cold on a 65 mm machine. The die needs its own 20\u201330 minutes because it has far more mass per unit of heater power.<\/p><\/details><details><summary>Can I start with the screws at zero rpm and heat?<\/summary><p>No. A stationary screw bows as the barrel expands; the bow shows up as metal-to-metal noise and liner scoring. 10\u201315 rpm is enough to prevent it.<\/p><\/details><details><summary>What torque should I expect at full rate?<\/summary><p>Typically 60\u201375% of rated torque on a well-matched line. Sustained values above 85% mean the machine is undersized for the formulation, not that the operator is doing something wrong.<\/p><\/details>\n<div class=\"method\"><h2 id=\"rm-s6\">Where these numbers come from<\/h2>\n<p>Values are drawn from the Kerke parameter table, commissioning records and service reports from lines in the field. Temperature windows and consumption figures are typical ranges \u2014 confirm on your own material before they become a production setpoint.<\/p><\/div>\n<div class=\"related\"><h2 id=\"rm-s7\">Related reading<\/h2><div class=\"rel-grid\"><a class=\"rel\" href=\"\/knowledge\/twin-screw-extruder-troubleshooting\/\"><span>Knowledge<\/span>Twin Screw Extruder Troubleshooting: Nine Symptoms, Nine Causes<\/a><a class=\"rel\" href=\"\/knowledge\/extruder-maintenance-schedule\/\"><span>Knowledge<\/span>Extruder Maintenance Schedule: 250 \/ 2,500 \/ 5,000 \/ 10,000 Hours<\/a><\/div><\/div>\n<div class=\"cta\"><div><b>Tell us your material \u2014 we will tell you the line<\/b><p>Send 25\u201350 kg and we run it on our lab extruder: pellets, running video and a capacity report back in 3\u20137 days.<\/p><\/div>\n<div class=\"acts\"><a href=\"\/get-a-quote\/\">Get a quote<\/a>\n<a class=\"alt\" href=\"\/get-a-quote\/#trial\">Send material for trial<\/a><\/div><\/div>\n<\/main>\n<aside><h5>On this page<\/h5><ol><li><a href=\"#sequence\">The sequence<\/a><\/li><li><a href=\"#temperatures\">Barrel profiles that work<\/a><\/li><li><a href=\"#mistakes\">Three startup mistakes that cost the most<\/a><\/li><li><a href=\"#shutdown\">Shutdown, which is half the story<\/a><\/li><li><a href=\"#faq\">FAQ<\/a><\/li><\/ol>\n<div class=\"sidecard\"><b>Question not covered?<\/b><p>Send the material, the machine model and the symptom. We answer with a parameter sheet, not a brochure.<\/p>\n<a class=\"btn\" href=\"\/get-a-quote\/\">Ask an engineer<\/a>\n<a class=\"btn ghost\" href=\"\/knowledge\/\">All articles<\/a><\/div><\/aside><\/div><\/div>\n<script type=\"application\/ld+json\">{\"@context\": \"https:\/\/schema.org\", \"@graph\": [{\"@type\": \"TechArticle\", \"headline\": \"Twin Screw Extruder Startup: The 9-Step Sequence That Protects the Screw\", \"description\": \"Most screw damage happens in the first ten minutes of a shift, not in the tenth month of service. 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The die needs its own 20\u201330 minutes because it has far more mass per unit of heater power.\"}}, {\"@type\": \"Question\", \"name\": \"Can I start with the screws at zero rpm and heat?\", \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"No. A stationary screw bows as the barrel expands; the bow shows up as metal-to-metal noise and liner scoring. 10\u201315 rpm is enough to prevent it.\"}}, {\"@type\": \"Question\", \"name\": \"What torque should I expect at full rate?\", \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"Typically 60\u201375% of rated torque on a well-matched line. Sustained values above 85% mean the machine is undersized for the formulation, not that the operator is doing something wrong.\"}}]}]}<\/script>\n<div class=\"wrap\"><section class=\"k3-more\" id=\"rm-more\"><h2>Twin screw extruder startup \u2014 the short version<\/h2><figure class=\"k3-fig\"><img decoding=\"async\" src=\"\/wp-content\/uploads\/2026\/11\/kte-65b-co-rotating-twin-screw-extruder-01-1200.webp\" alt=\"twin screw extruder startup\" loading=\"lazy\" width=\"1200\" height=\"675\"><figcaption>Kerke test line, Nanjing \u2014 where the figures on this page were measured<\/figcaption><\/figure><p>Note on Twin screw extruder startup: every figure on this page is a reference range measured on Kerke's own test line in Nanjing, not a catalogue maximum. If your material differs from the one in the table, send 25\u201350 kg and we will replace the range with a measured number.<\/p><p>Planning a twin screw extruder startup upgrade this quarter? Send the material and the target output \u2014 the configuration comes back within one working day.<\/p><p>Every twin screw extruder startup quotation lists the wear package as a separate line, so its cost is visible from day one.<\/p><p>Twin screw extruder startup questions are answered the same day, in English or Chinese.<\/p><p class=\"k3-rel\"><b>Related on this site:<\/b> <a href=\"\/machines\/co-rotating-twin-screw-extruder\/\">Twin screw extruder range<\/a> \u00b7 <a href=\"\/applications\/\">Extrusion lines by application<\/a> \u00b7 <a href=\"\/get-a-quote\/\">free extrusion line quotation<\/a> \u00b7 <a href=\"https:\/\/en.wikipedia.org\/wiki\/Pelletizing\" target=\"_blank\" rel=\"noopener\">Wikipedia: Pelletizing<\/a><\/p><\/section><\/div>\n<\/div>","protected":false},"excerpt":{"rendered":"<p>Home\/Knowledge\/Twin Screw Extruder Startup Operation \u00b7 7 min read Twin Screw Extruder Startup: The 9-Step Sequence That Protects the Screw Most screw damage happens in the first ten minutes of a shift, not in the tenth month of service. Here is the sequence we teach at commissioning, with the temperatures and checks that matter. 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