{"id":3487,"date":"2025-08-19T21:48:17","date_gmt":"2025-08-19T13:48:17","guid":{"rendered":"https:\/\/taichungbro.com\/?p=3487"},"modified":"2025-08-19T21:49:09","modified_gmt":"2025-08-19T13:49:09","slug":"multiphase-injection","status":"publish","type":"post","link":"https:\/\/www.taichungbro.com\/en\/2025\/08\/19\/multiphase-injection\/","title":{"rendered":"Multi-stage firing strategy \u2013 Reduces short shots and burnout"},"content":{"rendered":"<hr class=\"wp-block-separator has-alpha-channel-opacity is-style-wide\"\/>\n\n\n\n<div class=\"wp-block-rank-math-toc-block\" id=\"rank-math-toc\"><h2>Table of Content<\/h2><nav><ul><li class=\"\"><a href=\"#\u4e09\u4ef6\u539f\u5247\">Three principles<\/a><\/li><li class=\"\"><a href=\"#\u5148\u6293\u57fa\u6e96\u503c\uff1a\u5148\u505a\u300c\u55ae\u6bb5\u300d\u518d\u5206\u6bb5\">First, establish a baseline value: create a single segment before dividing into multiple segments.<\/a><\/li><li class=\"\"><a href=\"#\u6750\u6599\u5dee\u7570\uff1a-vb-\u7684\u9078\u64c7\u8207\u672b\u901f\">Material differences: Vb selection and final velocity<\/a><\/li><li class=\"\"><a href=\"#\u7f3a\u9677\u5c0d\u7b56\">Defect Countermeasures<\/a><\/li><li class=\"\"><a href=\"#\u76e3\u63a7\u6307\u6a19\uff1a\u628a\u300c\u53ef\u91cd\u8907\u300d\u8b8a\u6210\u65e5\u5e38\">Monitoring indicators<\/a><\/li><\/ul><\/nav><\/div>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity is-style-wide\"\/>\n\n\n\n<p class=\"wp-block-paragraph\">Injection speed isn&#039;t always better the faster it is, nor should it be maintained at a constant speed. The speed profile determines the stability of the melt leading edge and in-mold shear heat: too slow, and it will freeze and stagnate, causing short shots and flow marks; too fast, and it will have high shear and introduce air, causing burnt ends and spray marks. We&#039;ll provide a user-friendly, on-site approach to setting &quot;multi-speed&quot; injection, focusing on fixed fill time, stable injection speed, and pressure within limits. We offer a parameter adjustment process to help you quickly minimize short shots and burnt conditions.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\u4e09\u4ef6\u539f\u5247\">Three principles<\/h2>\n\n\n\n<ol class=\"wp-block-list\">\n<li>Maintain a steady injection speed: Try to keep the speed close throughout the filling process to avoid sudden changes in speed that could cause air entrainment.<\/li>\n\n\n\n<li>The adjustment difference for each mold should not be too large: the variation in filling time for each cavity in the same mold should be controlled within \u00b13%, and the yield will be significantly improved.<\/li>\n\n\n\n<li>There should be a safety margin in the pressure: leave a margin of 10-20% for the peak injection pressure; if the pressure has already reached the upper limit, going faster will only amplify the defects.<\/li>\n<\/ol>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\u5148\u6293\u57fa\u6e96\u503c\uff1a\u5148\u505a\u300c\u55ae\u6bb5\u300d\u518d\u5206\u6bb5\">First, establish a baseline value: create a single segment before dividing into multiple segments.<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Step A | Single-segment speed test<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Fill the mold with the product at a single speed until it is almost full (excluding holding pressure), and ensure that the filling time falls within the following recommended range. Then observe the pressure and appearance.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Suggested fill time (for initial reference only):<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Wall thickness \u2264 1.0 mm: 0.3\u20130.8 s<\/li>\n\n\n\n<li>1.0\u20132.0 mm: 0.8\u20131.5 s<\/li>\n\n\n\n<li>2.0\u20133.0 mm: 1.2\u20132.5 s<\/li>\n\n\n\n<li>\u22653.0 mm: 1.5\u20133.0 s<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Once we obtain this speed that is &quot;runnable, has reasonable pressure, and has an acceptable appearance,&quot; we will use it as the baseline speed Vb.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Step B | Segmentation Strategy<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Section 1 (Initial 10\u201315% volume): 0.3\u20130.5\u00d7Vb, intended to prevent spraying and whitening at the gate.<\/li>\n\n\n\n<li>Second stage (main filling 70\u201380% volume): 0.9\u20131.1\u00d7Vb, maintaining leading edge stability.<\/li>\n\n\n\n<li>Section 3 (end 10\u201315% volume): 0.6\u20130.8\u00d7Vb, reducing end compressed air and charring.<\/li>\n\n\n\n<li>When there are thin ribs\/long flow paths, a second 2.5 stage can be added: slightly increase the flow rate (+10\u201320%) before reaching the thin area to help pass through the bottleneck.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">*The most stable switching condition is achieved by adjusting the screw position; if the cavity pressure is visible, the starting point of the third segment can be aligned with the position where the pressure is about to rise.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\u6750\u6599\u5dee\u7570\uff1a-vb-\u7684\u9078\u64c7\u8207\u672b\u901f\">Material differences: Vb selection and final velocity<\/h2>\n\n\n\n<figure class=\"wp-block-table aligncenter\"><table class=\"has-fixed-layout\"><thead><tr><th>Material<\/th><th>Main filling Vb (relative to single-stage test speed)<\/th><th>End speed recommendation<\/th><th>Remark<\/th><\/tr><\/thead><tbody><tr><td>PP\/PE<\/td><td>0.9\u20131.1\u00d7<\/td><td>0.7\u20130.8\u00d7<\/td><td>Semi-crystalline structure, avoid hesitation, primary filling needs to be fast enough.<\/td><\/tr><tr><td>ABS\/HIPS<\/td><td>0.7\u20130.9\u00d7<\/td><td>0.6\u20130.7\u00d7<\/td><td>It&#039;s easy to burn, so slow down and add exhaust at the end of the race.<\/td><\/tr><tr><td>PC\/PMMA<\/td><td>0.6\u20130.8\u00d7<\/td><td>0.5\u20130.6\u00d7<\/td><td>High viscosity makes it easier to spray, but the initial spraying time is a bit slower.<\/td><\/tr><tr><td>PA6\/66<\/td><td>0.9\u20131.1\u00d7<\/td><td>0.7\u20130.8\u00d7<\/td><td>Good water flow, emphasis on drying and exhaust.<\/td><\/tr><tr><td>POM<\/td><td>0.9\u20131.1\u00d7<\/td><td>0.7\u20130.8\u00d7<\/td><td>The flow is fast; be careful to slow down at the ends to avoid jetting.<\/td><\/tr><\/tbody><\/table><figcaption class=\"wp-element-caption\">The table is for general reference only; actual conditions may vary depending on factors such as gate type, flow length, and mold temperature.<\/figcaption><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\u7f3a\u9677\u5c0d\u7b56\">Defect Countermeasures<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Objectives: Stable filling time, pressure not exceeding peak, and OK appearance.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Short shots (especially on the thin ribs\/far end)\n<ol class=\"wp-block-list\">\n<li>Increase the speed of the second segment by 10\u201320%.<\/li>\n\n\n\n<li>Add a short burst of speed before it reaches the thin ribs.<\/li>\n\n\n\n<li>Adjust the mold temperature by +5\u201310\u00b0C or increase the gate size by one level, then confirm.<\/li>\n<\/ol>\n<\/li>\n\n\n\n<li>End charring\/scorch marks\n<ol class=\"wp-block-list\">\n<li>The third segment starts earlier, and the speed drops to 0.6\u20130.7 \u00d7 Vb.<\/li>\n\n\n\n<li>Add end exhaust (or replace the exhaust steel).<\/li>\n\n\n\n<li>Lower the material temperature by 5\u201310\u00b0C; if that doesn&#039;t work, switch to V\/P earlier.<\/li>\n<\/ol>\n<\/li>\n\n\n\n<li>Jetting\/Serpentine Pattern\n<ol class=\"wp-block-list\">\n<li>The first stage should be reduced to 0.3\u20130.4 \u00d7 Vb, or changed to a small rounded corner guide.<\/li>\n\n\n\n<li>Let the molten adhesive &quot;attach to the mold&quot; first, then accelerate to the second stage.<\/li>\n<\/ol>\n<\/li>\n\n\n\n<li>Flow marks\/ripples\n<ol class=\"wp-block-list\">\n<li>The first segment is slightly faster (+10\u201315%) to make the leading edge more stable.<\/li>\n\n\n\n<li>Increase the mold temperature and add radius (R) to the gate connection area.<\/li>\n<\/ol>\n<\/li>\n\n\n\n<li>Rough edges accompanied by scorching\n<ol class=\"wp-block-list\">\n<li>Deceleration at the end of the range + earlier entry into the third stage;<\/li>\n\n\n\n<li>Check the mold clamping and parting surfaces;<\/li>\n\n\n\n<li>The pressure limit is lowered by 5\u201310% to avoid over-compressing the air.<\/li>\n<\/ol>\n<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\u76e3\u63a7\u6307\u6a19\uff1a\u628a\u300c\u53ef\u91cd\u8907\u300d\u8b8a\u6210\u65e5\u5e38\">Monitoring indicators<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Fill Time: Variation \u2264 3%.<\/li>\n\n\n\n<li>Peak injection pressure: 10\u201320 TP3T margin.<\/li>\n\n\n\n<li>Cavity pressure: The main filling should be smooth and flat, and there should be no sharp peaks or sudden surges at the end.<\/li>\n\n\n\n<li>Repeatability of weight per mold confirmed: target for short cycle parts \u00b10.2\u20130.4%.<\/li>\n\n\n\n<li>V\/P switching buffer: Retain a small amount of padding (e.g., 3\u20138 mm, depending on the machine) to prevent backflow.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The core of multi-stage velocity is not &quot;the more the better,&quot; but rather stabilizing the leading-edge velocity with the fewest possible stages. In practice, you only need to:<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li>First, use a single segment to determine the appropriate filling time and pressure margin.<\/li>\n\n\n\n<li>It can be divided into 3 sections according to &quot;slow start, fast run, and then slow down&quot;.<\/li>\n\n\n\n<li>Fine-tuning for defects<\/li>\n\n\n\n<li>I always keep an eye on three things: Fill Time, Peak Pressure, and Weight Variation.<\/li>\n<\/ol>\n\n\n\n<p class=\"wp-block-paragraph\">Following this approach, trial molding issues can usually be significantly resolved in a short period of time; subsequently, structural optimization through gate and venting will lead to more stable production. In short, the speed curve is the metronome of molding; by maintaining a stable pace, quality and yield will naturally follow.<\/p>\n\n\n\n<div style=\"height:var(--wp--preset--spacing--30)\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity is-style-wide\"\/>\n\n\n\n<h5 class=\"wp-block-heading has-text-align-center\" id=\"\u60f3\u4e86\u89e3\u6709\u95dc\u7ba1\u87ba\u7d0b\u3001\u76f4\u87ba\u7d0b\u3001\u9310\u87ba\u7d0b\u3001\u5c3a\u5bf8\u8868\u793a\u3001\u82f1\u5236\u7ba1\u87ba\u7d0b\u3001\u516c\u5236\u7ba1\u87ba\u7d0b\u7684\u77e5\u8b58\u55ce\uff1f-\u5ef6\u4f38\u95b1\u8b80\uff1a\u300a\u7ba1\u87ba\u7d0b\u767e\u767e\u7a2e-\u4f60\u90fd\u8a8d\u8b58\u55ce-\u300b\">Want to learn about injection molding monitoring and key injection parameters? <br>Further Reading :<a href=\"https:\/\/www.taichungbro.com\/en\/2025\/07\/29\/mold-sensor\/\" data-type=\"link\" data-id=\"https:\/\/taichungbro.com\/2023\/10\/28\/screw\/\" target=\"_blank\" rel=\"noopener\">Key Technologies for Injection Molding Quality Monitoring \u2013 In-Mold Pressure and Temperature Sensors<\/a><\/h5>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity is-style-wide\"\/>\n\n\n\n<div style=\"height:11px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>","protected":false},"excerpt":{"rendered":"<p>\u591a\u6bb5\u5c04\u51fa\u901f\u5ea6\u662f\u964d\u4f4e\u77ed\u5c04\u8207\u71d2\u7126\u7684\u95dc\u9375\u3002\u672c\u6587\u6559\u4f60\u5148\u7528\u55ae\u6bb5\u901f\u5ea6\u627e\u57fa\u6e96\uff0c\u518d\u4ee5\u4e09\u6bb5\u5f0f\u300c\u6162\u8d77\u3001\u5feb\u8dd1\u3001\u672b\u7aef\u964d\u901f\u300d\u8a2d\u5b9a\uff0c\u4e26\u7528\u87ba\u687f\u4f4d\u7f6e\u5207\u63db\u8207\u7aef\u90e8\u6392\u6c23\u512a\u5316\uff0c\u8b93\u586b\u5145\u6642\u9593\u7a69\u5b9a\u3001\u5cf0\u58d3\u4fdd\u7559\u88d5\u91cf\uff0c\u5feb\u901f\u6536\u6582\u5674\u5c04\u7d0b\u3001\u672b\u7aef\u7126\u75d5\u8207\u6d41\u75d5\uff0c\u63d0\u5347\u826f\u7387\u8207\u5916\u89c0\u4e00\u81f4\u6027\u3002<\/p>","protected":false},"author":2,"featured_media":3489,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[45],"tags":[370,367,368,369,103],"class_list":["post-3487","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-industrial-knowledge","tag-v-p","tag-367","tag-368","tag-369","tag-103"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.taichungbro.com\/en\/wp-json\/wp\/v2\/posts\/3487","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.taichungbro.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.taichungbro.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.taichungbro.com\/en\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.taichungbro.com\/en\/wp-json\/wp\/v2\/comments?post=3487"}],"version-history":[{"count":0,"href":"https:\/\/www.taichungbro.com\/en\/wp-json\/wp\/v2\/posts\/3487\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.taichungbro.com\/en\/wp-json\/wp\/v2\/media\/3489"}],"wp:attachment":[{"href":"https:\/\/www.taichungbro.com\/en\/wp-json\/wp\/v2\/media?parent=3487"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.taichungbro.com\/en\/wp-json\/wp\/v2\/categories?post=3487"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.taichungbro.com\/en\/wp-json\/wp\/v2\/tags?post=3487"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}