{"id":8456,"date":"2026-05-28T09:00:00","date_gmt":"2026-05-28T08:00:00","guid":{"rendered":"https:\/\/uplastech.com\/extruder-screw-wear\/"},"modified":"2026-11-02T02:25:24","modified_gmt":"2026-11-02T02:25:24","slug":"extruder-screw-wear","status":"publish","type":"post","link":"https:\/\/uplastech.com\/pl\/extruder-screw-wear\/","title":{"rendered":"Extruder Screw Wear: Measuring It and Knowing When to Replace"},"content":{"rendered":"<style>\n.upl-blog{font-size:17px;line-height:1.78;color:#1f2937}\n.upl-blog p{margin:0 0 18px}\n.upl-blog h2{font-size:26px;line-height:1.3;color:#0b2b33;margin:46px 0 14px;font-weight:700;letter-spacing:-.015em}\n.upl-blog h3{font-size:19.5px;color:#0d3b47;margin:28px 0 10px;font-weight:700}\n.upl-blog ul,.upl-blog ol{margin:0 0 20px;padding-left:22px}\n.upl-blog li{margin:0 0 9px}\n.upl-blog figure{margin:0 0 34px}\n.upl-blog figure img{width:100%;height:auto;display:block;border-radius:10px}\n.upl-blog figcaption{font-size:13px;color:#6b7280;margin-top:10px;line-height:1.5}\n.upl-blog .toc{background:none;border:0;border-radius:0;padding:0;margin:0 0 34px}\n.upl-blog .toc .lwptoc{margin:0}\n.upl-blog .toc h4{margin:0 0 10px;font-size:13px;letter-spacing:.1em;text-transform:uppercase;color:#0d5563}\n.upl-blog .toc ol{margin:0;padding-left:18px;font-size:14.5px}\n.upl-blog .toc li{margin-bottom:6px}\n.upl-blog table{width:100%;border-collapse:collapse;font-size:14.5px;margin:0 0 10px}\n.upl-blog th{background:#0d3b47;color:#fff;text-align:left;padding:11px 13px;font-weight:600;font-size:13.5px;border:0}\n.upl-blog td{padding:11px 13px;border:0;border-bottom:1px solid #e8ebed;vertical-align:top}\n.upl-blog tbody tr:nth-child(even){background:#fafbfc}\n.upl-blog .tablecap{font-size:12.5px;color:#6b7280;margin:0 0 30px}\n.upl-blog .myth{background:#fff8ef;border:1px solid #f6ddbd;border-radius:8px;padding:16px 20px;margin:0 0 26px;font-size:15.5px}\n.upl-blog .myth b{color:#a85c10}\n.upl-blog .callout{background:#f2f8f9;border-radius:8px;padding:18px 22px;margin:0 0 26px;font-size:15.5px;border-left:3px solid #14707f}\n.upl-blog .faq h3{border-top:1px solid #eceff1;padding-top:22px;margin-top:0;font-size:18px}\n.upl-blog .faq h3:first-of-type{border-top:0;padding-top:0}\n.upl-blog .cta{background:linear-gradient(135deg,#0b2b33,#0d5563);color:#fff;border-radius:12px;padding:34px;margin:48px 0 30px}\n.upl-blog .cta h2,.upl-blog .cta .cta-h{color:#fff;margin:0 0 10px;font-size:24px;font-weight:700;line-height:1.3}\n.upl-blog .cta p{color:#c9dee3;margin:0 0 20px;font-size:16px}\n.upl-blog .btn{display:inline-block;background:#e07a1f;color:#fff;text-decoration:none;font-weight:700;padding:13px 26px;border-radius:8px;font-size:15.5px}\n.upl-blog .rel{border-top:1px solid #e8ebed;margin-top:40px;padding-top:26px}\n.upl-blog .rel h4{font-size:13px;letter-spacing:.1em;text-transform:uppercase;color:#6b7280;margin:0 0 14px}\n.upl-blog .rel ul{list-style:none;padding:0;margin:0}\n.upl-blog .rel li{padding:11px 0;border-bottom:1px dashed #e8ebed}\n.upl-blog .rel a{text-decoration:none;font-weight:600;font-size:15.5px}\n@media(max-width:640px){.upl-blog h2{font-size:22px}.upl-blog table{font-size:13px}.upl-blog .cta{padding:24px}}\n\/* \u5355\u7bc7\u9875\u9690\u85cf WhatsApp \u95ee\u5019\u5361\uff0c\u53ea\u4fdd\u7559\u5706\u5f62\u6c14\u6ce1\uff0c\u907f\u514d\u906e\u6321\u4fa7\u680f\u8be2\u76d8\u63d0\u4ea4\u6309\u94ae\u3002\n   \u6ce8\u610f\uff1aClick to Chat \u7684\u70b9\u51fb\u903b\u8f91\u662f\u300c\u95ee\u5019\u5361\u5143\u7d20\u5b58\u5728\u5c31\u4e0d\u8df3\u8f6c\u300d\uff0c\u53ea\u9760 CSS \u9690\u85cf\u4f1a\u8ba9\u6c14\u6ce1\u53d8\u6210\u6b7b\u94fe\u63a5\u3002\n   Code Snippets #9\u300cUPL single post: WhatsApp bubble jumps straight to chat\u300d\u8d1f\u8d23\u628a\u8be5\u8282\u70b9\u4ece DOM \u79fb\u9664\uff0c\n   \u4e0b\u9762\u8fd9\u6761 CSS \u53ea\u662f\u79fb\u9664\u524d\u7684\u89c6\u89c9\u515c\u5e95\u3002\u5220 #9 \u524d\u5fc5\u987b\u5148\u5220\u8fd9\u6761\u89c4\u5219\u3002 *\/\nbody.single-post .ht_ctc_chat_greetings_box{display:none !important}\n<\/style>\n<div class=\"upl-blog\">\n<figure>\n<img fetchpriority=\"high\" decoding=\"async\" src=\"https:\/\/uplastech.com\/wp-content\/uploads\/2026\/11\/extruder-screw-wear.jpg\" alt=\"A long steel extruder screw resting on wooden V-blocks on a workshop floor while a fitter kneels beside it with a digital caliper measuring the flight\" width=\"1536\" height=\"909\"><figcaption>The wear is in the flights, and it is measured in tenths of a millimetre.<\/figcaption><\/figure>\n<div class=\"toc\"><\/div>\n<h2 id=\"what\">What wears and why<\/h2>\n<p>The screw and barrel wear against each other because they are not supposed to touch and occasionally do. The flight land runs within a few hundredths of a millimetre of the barrel wall, and any deflection, any hard particle or any moment of starved feeding brings them into contact. Every contact removes a little metal from one or both.<\/p>\n<p>The dominant mechanism in clean polymers is adhesive wear at the flight land. In filled polymers it is abrasive wear, and the abrasive particles are harder than the barrel steel. Glass fibre at 30 percent loading is roughly three times as aggressive as the same polymer unfilled, and carbon fibre is worse again because the fibres are harder and stiffer.<\/p>\n<p>There is a third mechanism that is often missed: corrosive wear. PVC without adequate stabilisation releases hydrogen chloride at processing temperature, and the acid attacks the barrel and the screw root. The result is a pitted surface that holds material and degrades it, which then produces black specks that no amount of purging removes.<\/p>\n<p>The wear is never uniform along the screw. The feed section wears least because the material there is solid and cold. The compression section wears most because that is where pressure and shear peak. The metering section wears moderately but matters most, because that is where the pumping capability is set.<\/p>\n<h2 id=\"numbers\">The numbers that move first<\/h2>\n<p>The first number to move is not quality, it is output. As the flight clearance opens, melt leaks back over the flight instead of being pushed forward. The drag flow stays roughly constant but the pressure flow backwards increases with the cube of the clearance, so a small increase in gap produces a large loss in net output.<\/p>\n<p>The chart on the left is a 60 mm, 30:1 screw running LDPE at 80 rpm. At a flight clearance of 0.10 mm, which is new, output is 420 kg\/h. At 0.40 mm, which is a normal end of life value, output is 375 kg\/h. At 0.85 mm, which is scrap, output is 272 kg\/h. That is 35 percent of the machine's capability lost without a single alarm.<\/p>\n<p>The second number is specific energy, and it moves in the opposite direction. As output falls, the energy per kilogram rises, because the motor is doing the same work for less product. At 0.10 mm clearance the screw uses 0.21 kWh\/kg; at 0.85 mm it uses 0.355 kWh\/kg, a 69 percent increase in energy per kilogram.<\/p>\n<p>The third number is melt temperature stability. A worn screw pumps unevenly, so the pressure at the die fluctuates and the melt temperature follows it. The operator sees this as gauge variation and adjusts the haul-off, which masks the symptom and leaves the cause in place.<\/p>\n<figure>\n<img decoding=\"async\" src=\"https:\/\/uplastech.com\/wp-content\/uploads\/2026\/11\/extruder-screw-wear-chart.jpg\" alt=\"Output falling from 420 to 272 kilograms per hour as flight clearance opens from 0.1 to 0.85 millimetres, with specific energy rising from 0.21 to 0.355 kilowatt hours per kilogram, and a bar chart of wear rate by filler\" width=\"1536\" height=\"909\"><figcaption>Left: output and specific energy against flight clearance on a 60 mm screw. Right: how fast different fillers wear the same screw.<\/figcaption><\/figure>\n<h2 id=\"measure\">Measuring clearance without pulling the screw<\/h2>\n<p>Pulling a screw is a two to three hour job and should not be the routine way to check wear. There are three measurements that can be taken in place, and together they give a clear picture.<\/p>\n<p>The first is the feeler gauge test through the feed throat. With the screw cold and the feed throat open, a set of feeler gauges can be worked between the flight land and the barrel wall at several points along the first few flights. This only reaches the feed section, which wears least, so it gives a lower bound rather than a true value.<\/p>\n<p>The second is a bore gauge or an internal micrometer through the die end, measuring the barrel inside diameter at several positions, combined with a caliper measurement of the screw outside diameter at the same positions. The difference is the diametral clearance; the radial clearance is half of it. This requires the die to be off, which is a fifteen minute job on most lines.<\/p>\n<p>The third is indirect but very sensitive: the specific output test. Run a known polymer at a fixed screw speed and back pressure, weigh the output over ten minutes, and divide by the energy consumed. Compare the result with the value recorded when the screw was new. A drop of more than 8 percent in specific output is a strong indicator that clearance has opened beyond the point where it is worth running.<\/p>\n<p>Whichever method is used, the measurement has to be taken at the same positions every time, because wear is not uniform and a single reading can be misleading in either direction.<\/p>\n<h2 id=\"pattern\">Reading the wear pattern<\/h2>\n<p>A screw that is worn evenly along its length has been run within its design envelope. A screw that is worn heavily in one short section has been run outside it, and the pattern tells you how.<\/p>\n<p>Heavy wear in the first three flights means the feed section was starved and the screw was running dry, or the material was fed as a hard granule that abraded the land before it melted. This is common on lines with a poorly tuned feeder and on lines running glass-filled regrind with a high bulk density.<\/p>\n<p>Heavy wear in the middle of the compression section means high pressure and high shear in a short distance. That is a screw design issue as much as a wear issue, and replacing the screw with an identical one will reproduce it. A barrier screw or a longer compression zone distributes the work and lasts longer.<\/p>\n<p>A polished band or a groove running along the flight root is a sign of a hard particle trapped between screw and barrel, which scores both. That is not normal wear and the barrel should be checked at the same time, because a scored barrel will destroy a new screw in a few months.<\/p>\n<h2 id=\"replace\">When to replace, when to rebuild<\/h2>\n<p>The decision has three inputs: clearance, output loss and the value of the product. A screw at 0.5 mm clearance running a commodity product at 60 percent of design output is costing more in lost production than a new screw would cost. A screw at the same clearance running a low volume specialty product may be perfectly economic to keep.<\/p>\n<p>Rebuilding by hard facing or by welding the flights and regrinding is a real option and costs 30 to 50 percent of a new screw. The result is a screw with the original geometry restored, but the base metal has been through a thermal cycle and the hard facing may not match the original. Rebuilds are best on screws that are otherwise sound and worn evenly.<\/p>\n<p>Replacement is the right answer when the wear is uneven, when the screw has been run hot enough to lose its hardness, or when the design itself is the problem. A new screw is also an opportunity to change the geometry: a barrier section, a mixing head or a longer compression zone can be added at no extra cost over a like for like replacement.<\/p>\n<p>The barrel is the other half of the decision and is often neglected. A new screw in a worn barrel has a large clearance from day one, and it will wear faster because the flights have to bridge a gap. If the barrel inside diameter is more than 0.15 mm over nominal at any point, it should be honed or replaced at the same time.<\/p>\n<table>\n<thead>\n<tr>\n<th>Flight clearance<\/th>\n<th>Output loss<\/th>\n<th>Specific energy<\/th>\n<th>Dzia\u0142anie<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>0.10 mm, new<\/td>\n<td>Baseline<\/td>\n<td>Baseline<\/td>\n<td>Record it as the reference<\/td>\n<\/tr>\n<tr>\n<td>0.20 mm<\/td>\n<td>About 2 %<\/td>\n<td>Plus 2 %<\/td>\n<td>Monitor, no action<\/td>\n<\/tr>\n<tr>\n<td>0.30 mm<\/td>\n<td>About 5 %<\/td>\n<td>Plus 8 %<\/td>\n<td>Plan a replacement in the next shutdown<\/td>\n<\/tr>\n<tr>\n<td>0.40 mm<\/td>\n<td>About 11 %<\/td>\n<td>Plus 17 %<\/td>\n<td>Rebuild or replace at the next opportunity<\/td>\n<\/tr>\n<tr>\n<td>0.55 mm<\/td>\n<td>About 19 %<\/td>\n<td>Plus 31 %<\/td>\n<td>Replace now, check the barrel<\/td>\n<\/tr>\n<tr>\n<td>0.70 mm and above<\/td>\n<td>About 27 %<\/td>\n<td>Plus 49 %<\/td>\n<td>Replace, barrel almost certainly worn too<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 1 \u2014 Clearance against what it costs on a 60 mm screw<\/p>\n<h2 id=\"pair\">Screw and barrel as a pair<\/h2>\n<p>The clearance is a property of the pair, not of either component. Measuring the screw outside diameter and finding it within tolerance tells you nothing if the barrel has worn by the same amount. The two have to be measured together and the difference recorded.<\/p>\n<p>Barrel wear is concentrated in the same places as screw wear and for the same reasons. It is harder to measure because the bore is not accessible, but a bore gauge through the die end at three positions along the length is enough to establish a trend. A barrel that has worn into a taper, wider at the die end, will produce a pressure profile the screw was never designed for.<\/p>\n<p>The practical rule is to replace both or neither. A new screw in a worn barrel runs at a large clearance and loses output from the first day, which is the most expensive possible outcome: you paid for a new screw and got none of the benefit.<\/p>\n<h2 id=\"log\">A wear log that earns its keep<\/h2>\n<p>The value of a wear log is not the individual reading, it is the trend. A screw that has lost 0.05 mm of flight in 20,000 hours is on course for a decade of life. A screw that has lost 0.05 mm in 2,000 hours is on course for replacement in two years, and the cause is worth finding before the second screw goes the same way.<\/p>\n<p>The log should record the measurement position, the method, the polymer, the filler content and the hours run since the last measurement. Without the material record the trend is meaningless, because a line that switched to 30 percent glass will show a step change in wear rate that has nothing to do with the machine.<\/p>\n<table>\n<thead>\n<tr>\n<th>Filler<\/th>\n<th>Wear rate, um per 1,000 h<\/th>\n<th>Expected life to 0.4 mm<\/th>\n<th>Note<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Unfilled PE or PP<\/td>\n<td>15<\/td>\n<td>About 20,000 h<\/td>\n<td>Baseline, adhesive wear only<\/td>\n<\/tr>\n<tr>\n<td>Glass fibre 20 %<\/td>\n<td>45<\/td>\n<td>About 6,500 h<\/td>\n<td>Coupling agent helps<\/td>\n<\/tr>\n<tr>\n<td>Talc 30 %<\/td>\n<td>55<\/td>\n<td>About 5,500 h<\/td>\n<td>Softer than glass but very abrasive<\/td>\n<\/tr>\n<tr>\n<td>Calcium carbonate 40 %<\/td>\n<td>60<\/td>\n<td>About 5,000 h<\/td>\n<td>Particle size matters more than loading<\/td>\n<\/tr>\n<tr>\n<td>Glass fibre 30 %<\/td>\n<td>75<\/td>\n<td>About 4,000 h<\/td>\n<td>Bimetallic barrel strongly advised<\/td>\n<\/tr>\n<tr>\n<td>Carbon fibre 20 %<\/td>\n<td>130<\/td>\n<td>About 2,300 h<\/td>\n<td>Consider a carbide lined barrel<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 2 \u2014 Wear rate by filler on a nitrided 60 mm screw<\/p>\n<p>Two things shorten those lives dramatically and are worth recording separately. Running below the recommended feed temperature raises the viscosity and therefore the shear at the flight land. Running with a starved feed does the same and adds direct metal to metal contact. Both show up as a step change in the log, and both are process problems rather than material problems.<\/p>\n<div class=\"faq\">\n<h3>How often should flight clearance be measured?<\/h3>\n<p>Every 2,000 running hours for unfilled polymers, every 1,000 hours for glass or mineral filled. On a line that runs continuously that is roughly twice a year and four times a year respectively. The measurement takes fifteen minutes with the die off.<\/p>\n<h3>Can I keep running at 0.6 mm clearance if the parts are still in specification?<\/h3>\n<p>You can, but you are paying for it. At that clearance the machine is producing roughly 25 percent less than it could for the same energy, and the melt temperature is less stable. The parts may pass, but the cost per kilogram is not competitive.<\/p>\n<h3>Does a hard-faced screw last longer?<\/h3>\n<p>Yes, typically two to three times longer in abrasive service, at roughly 30 to 50 percent more cost. It is worth it above about 20 percent filler loading. Below that, the base metal wears by adhesion rather than abrasion and the hard facing adds little.<\/p>\n<h3>Why did my new screw lose output in the first month?<\/h3>\n<p>Almost certainly the barrel. A worn barrel means the new screw starts with a large clearance, and the flights wear faster because they have to bridge the gap. Measure the barrel bore before fitting a new screw.<\/p>\n<h3>Can screw wear cause black specks?<\/h3>\n<p>Yes, in two ways. A worn flight leaves a stagnant layer that degrades over time and releases as specks, and a corroded screw root pits and holds material. If specks persist after a full purge and a die clean, wear is the next thing to check.<\/p>\n<h3>Is it cheaper to rebuild or replace?<\/h3>\n<p>Rebuild costs 30 to 50 percent of new and restores the geometry, but the base metal has been thermally cycled. It suits evenly worn screws in non-critical service. Replace when the wear is uneven, when the design is the problem, or when the product cannot tolerate another wear cycle.<\/p>\n<\/div>\n<div class=\"cta\">\n<p class=\"cta-h\">Machine running below its rated output?<\/p>\n<p>Send the screw diameter, the polymer and filler, the running hours and the current output. We will tell you whether the clearance is the cause and what a replacement would recover.<\/p>\n<p><a class=\"btn\" href=\"https:\/\/uplastech.com\/pl\/rozwiazania-w-zakresie-wytlaczania-tworzyw-sztucznych\/\">Ask about screw wear<\/a>\n<\/div>\n<div class=\"rel\">\n<h4>Continue reading<\/h4>\n<ul>\n<li><a href=\"https:\/\/uplastech.com\/pl\/extrusion-line-shutdown\/\">Extrusion Line Shutdown: Leaving the Machine in a State You Can Restart<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/pl\/melt-pump-extrusion\/\">Melt Pumps: Taking Pressure Control Away From the Screw<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/pl\/extrusion-cutter-types\/\">Cutter Types: Matching the Cut to the Profile<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/pl\/extrusion-haul-off-speed\/\">Haul-Off Speed: The Setting That Decides the Wall<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/pl\/extrusion-gravimetric-dosing\/\">Gravimetric Dosing: Controlling the Recipe by Weight<\/a><\/li>\n<\/ul>\n<\/div>\n<\/div>","protected":false},"excerpt":{"rendered":"<p>A worn screw does not fail. It quietly gives up throughput, then specific energy, then mixing, and by the time the parts look wrong the machine has been running below its capability for a year. The clearance is the number to watch.<\/p>","protected":false},"author":1,"featured_media":8454,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17],"tags":[],"class_list":["post-8456","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-plastic-extrusion-process"],"meta_box":{"post-to-quiz_to":[]},"_links":{"self":[{"href":"https:\/\/uplastech.com\/pl\/wp-json\/wp\/v2\/posts\/8456","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/uplastech.com\/pl\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/uplastech.com\/pl\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/uplastech.com\/pl\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/uplastech.com\/pl\/wp-json\/wp\/v2\/comments?post=8456"}],"version-history":[{"count":1,"href":"https:\/\/uplastech.com\/pl\/wp-json\/wp\/v2\/posts\/8456\/revisions"}],"predecessor-version":[{"id":8815,"href":"https:\/\/uplastech.com\/pl\/wp-json\/wp\/v2\/posts\/8456\/revisions\/8815"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/uplastech.com\/pl\/wp-json\/wp\/v2\/media\/8454"}],"wp:attachment":[{"href":"https:\/\/uplastech.com\/pl\/wp-json\/wp\/v2\/media?parent=8456"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/uplastech.com\/pl\/wp-json\/wp\/v2\/categories?post=8456"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/uplastech.com\/pl\/wp-json\/wp\/v2\/tags?post=8456"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}