{"id":5143,"date":"2026-04-19T03:54:07","date_gmt":"2026-04-19T11:54:07","guid":{"rendered":"https:\/\/haifengmachine.com\/?p=5143"},"modified":"2026-04-19T03:59:00","modified_gmt":"2026-04-19T11:59:00","slug":"pu-shoe-injection-machine-troubleshooting-guide","status":"publish","type":"post","link":"https:\/\/haifengmachine.com\/ko\/pu-shoe-injection-machine-troubleshooting-guide\/","title":{"rendered":"PU Shoe Injection Machine Troubleshooting Guide"},"content":{"rendered":"\t\t<div data-elementor-type=\"wp-post\" data-elementor-id=\"5143\" class=\"elementor elementor-5143\" data-elementor-post-type=\"post\">\n\t\t\t\t<div class=\"elementor-element elementor-element-8c28854 e-flex e-con-boxed e-con e-parent\" data-id=\"8c28854\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-b361644 elementor-toc--minimized-on-tablet elementor-widget elementor-widget-table-of-contents\" data-id=\"b361644\" data-element_type=\"widget\" data-e-type=\"widget\" data-settings=\"{&quot;headings_by_tags&quot;:[&quot;h2&quot;,&quot;h3&quot;,&quot;h4&quot;,&quot;h5&quot;],&quot;exclude_headings_by_selector&quot;:[],&quot;marker_view&quot;:&quot;bullets&quot;,&quot;no_headings_message&quot;:&quot;No headings were found on this page.&quot;,&quot;icon&quot;:{&quot;value&quot;:&quot;fas fa-circle&quot;,&quot;library&quot;:&quot;fa-solid&quot;,&quot;rendered_tag&quot;:&quot;&lt;svg class=\\&quot;e-font-icon-svg e-fas-circle\\&quot; viewBox=\\&quot;0 0 512 512\\&quot; xmlns=\\&quot;http:\\\/\\\/www.w3.org\\\/2000\\\/svg\\&quot;&gt;&lt;path d=\\&quot;M256 8C119 8 8 119 8 256s111 248 248 248 248-111 248-248S393 8 256 8z\\&quot;&gt;&lt;\\\/path&gt;&lt;\\\/svg&gt;&quot;},&quot;minimize_box&quot;:&quot;yes&quot;,&quot;minimized_on&quot;:&quot;tablet&quot;,&quot;hierarchical_view&quot;:&quot;yes&quot;,&quot;min_height&quot;:{&quot;unit&quot;:&quot;px&quot;,&quot;size&quot;:&quot;&quot;,&quot;sizes&quot;:[]},&quot;min_height_tablet&quot;:{&quot;unit&quot;:&quot;px&quot;,&quot;size&quot;:&quot;&quot;,&quot;sizes&quot;:[]},&quot;min_height_mobile&quot;:{&quot;unit&quot;:&quot;px&quot;,&quot;size&quot;:&quot;&quot;,&quot;sizes&quot;:[]}}\" data-widget_type=\"table-of-contents.default\">\n\t\t\t\t\t\t\t<div class=\"elementor-toc__header\">\n\t\t\t<h4 class=\"elementor-toc__header-title\">\n\t\t\t\tTable of Contents\t\t\t<\/h4>\n\t\t\t\t\t\t\t<div class=\"elementor-toc__toggle-button elementor-toc__toggle-button--expand\" role=\"button\" tabindex=\"0\" aria-controls=\"elementor-toc__b361644\" aria-expanded=\"true\" aria-label=\"Open table of contents\"><svg aria-hidden=\"true\" class=\"e-font-icon-svg e-fas-chevron-down\" viewBox=\"0 0 448 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M207.029 381.476L12.686 187.132c-9.373-9.373-9.373-24.569 0-33.941l22.667-22.667c9.357-9.357 24.522-9.375 33.901-.04L224 284.505l154.745-154.021c9.379-9.335 24.544-9.317 33.901.04l22.667 22.667c9.373 9.373 9.373 24.569 0 33.941L240.971 381.476c-9.373 9.372-24.569 9.372-33.942 0z\"><\/path><\/svg><\/div>\n\t\t\t\t<div class=\"elementor-toc__toggle-button elementor-toc__toggle-button--collapse\" role=\"button\" tabindex=\"0\" aria-controls=\"elementor-toc__b361644\" aria-expanded=\"true\" aria-label=\"Close table of contents\"><svg aria-hidden=\"true\" class=\"e-font-icon-svg e-fas-chevron-up\" viewBox=\"0 0 448 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M240.971 130.524l194.343 194.343c9.373 9.373 9.373 24.569 0 33.941l-22.667 22.667c-9.357 9.357-24.522 9.375-33.901.04L224 227.495 69.255 381.516c-9.379 9.335-24.544 9.317-33.901-.04l-22.667-22.667c-9.373-9.373-9.373-24.569 0-33.941L207.03 130.525c9.372-9.373 24.568-9.373 33.941-.001z\"><\/path><\/svg><\/div>\n\t\t\t\t\t<\/div>\n\t\t<div id=\"elementor-toc__b361644\" class=\"elementor-toc__body\">\n\t\t\t<div class=\"elementor-toc__spinner-container\">\n\t\t\t\t<svg class=\"elementor-toc__spinner eicon-animation-spin e-font-icon-svg e-eicon-loading\" aria-hidden=\"true\" viewBox=\"0 0 1000 1000\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M500 975V858C696 858 858 696 858 500S696 142 500 142 142 304 142 500H25C25 237 238 25 500 25S975 237 975 500 763 975 500 975Z\"><\/path><\/svg>\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-b86a2bc elementor-widget elementor-widget-author-box\" data-id=\"b86a2bc\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"author-box.default\">\n\t\t\t\t\t\t\t<div class=\"elementor-author-box\">\n\t\t\t\t\t\t\t<a href=\"https:\/\/www.linkedin.com\/in\/jiacheng-dai-haifeng-automation\/%20EEAT\u80cc\u4e66\" class=\"elementor-author-box__avatar\" target=\"_blank\" rel=\"noopener\">\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/haifengmachine.com\/wp-content\/uploads\/2026\/04\/6f52b74a24f1daff3840682463cc195c-300x300.png\" alt=\"Picture of Jiacheng Dai\" loading=\"lazy\" title=\"\">\n\t\t\t\t<\/a>\n\t\t\t\n\t\t\t<div class=\"elementor-author-box__text\">\n\t\t\t\t\t\t\t\t\t<a href=\"https:\/\/www.linkedin.com\/in\/jiacheng-dai-haifeng-automation\/%20EEAT\u80cc\u4e66\" target=\"_blank\" rel=\"noopener\">\n\t\t\t\t\t\t<span class=\"elementor-author-box__name\">\n\t\t\t\t\t\t\tJiacheng Dai\t\t\t\t\t\t<\/span>\n\t\t\t\t\t<\/a>\n\t\t\t\t\n\t\t\t\t\t\t\t\t\t<div class=\"elementor-author-box__bio\">\n\t\t\t\t\t\t<p>Vice President, Sales & Marketing of Zhejiang Haifeng Automation Equipment Co., Ltd<\/p>\n\t\t\t\t\t<\/div>\n\t\t\t\t\n\t\t\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-1099066 e-flex e-con-boxed e-con e-parent\" data-id=\"1099066\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-9c7306c elementor-widget elementor-widget-text-editor\" data-id=\"9c7306c\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<h2><strong><b>Introduction<\/b><\/strong><\/h2><p>PU shoe injection machines are the core equipment in polyurethane footwear production, especially for safety shoes, work boots, and dual-density soles. In daily operation, even a well-configured machine can run into issues\u2014unstable foaming, poor bonding, uneven density, or mechanical faults.<\/p><p>A practical troubleshooting approach helps reduce downtime, improve product quality, and extend machine life. This guide summarizes common problems and how to deal with them on-site.<\/p><h2><strong><b>Common Problems and Causes<\/b><\/strong><\/h2><h3><strong><b>1. Uneven Foam Density<\/b><\/strong><\/h3><p><strong><b>Symptoms:<\/b><\/strong>\u00a0Sole density varies, bubbles are inconsistent, or structure looks rough.<br \/><strong><b>Possible causes:<\/b><\/strong><\/p><ul><li>Incorrect mixing ratio of polyol and isocyanate<\/li><li>Poor mixing head performance<\/li><li>Temperature fluctuation in raw materials<\/li><\/ul><p><strong><b>Solution:<\/b><\/strong><br \/>Check metering pumps and recalibrate ratio settings. Clean or service the mixing head. Maintain stable material temperature (usually 20\u201325\u00b0C depending on formulation).<\/p><h3><strong><b>2. Poor Sole Bonding (Upper Separation)<\/b><\/strong><\/h3><p><strong><b>Symptoms:<\/b><\/strong>\u00a0Sole separates from upper after demoulding or during testing.<br \/><strong><b>Possible causes:<\/b><\/strong><\/p><ul><li>Insufficient adhesive or primer<\/li><li>Incorrect mold temperature<\/li><li>Contaminated upper surface<\/li><\/ul><p><strong><b>Solution:<\/b><\/strong><br \/>Ensure proper primer application and drying time. Adjust mold temperature to recommended range. Keep uppers clean and dry before injection.<\/p><h3><strong><b>3. Air Bubbles or Voids<\/b><\/strong><\/h3><p><strong><b>Symptoms:<\/b><\/strong>\u00a0Visible holes or internal voids in the PU sole.<br \/><strong><b>Possible causes:<\/b><\/strong><\/p><ul><li>Moisture in raw materials<\/li><li>Air trapped during mixing<\/li><li>Low injection pressure<\/li><\/ul><p><strong><b>Solution:<\/b><\/strong><br \/>Use dry materials and sealed storage. Check degassing if applicable. Increase injection pressure and ensure smooth material flow.<\/p><h3><strong><b>4. Machine Not Injecting Properly<\/b><\/strong><\/h3><p><strong><b>Symptoms:<\/b><\/strong>\u00a0No material output or unstable injection.<br \/><strong><b>Possible causes:<\/b><\/strong><\/p><ul><li>Blocked mixing head<\/li><li>Pump failure or leakage<\/li><li>Control system fault<\/li><\/ul><p><strong><b>Solution:<\/b><\/strong><br \/>Inspect and clean the mixing head. Check seals and pump condition. Verify PLC or control panel signals.<\/p><h3><strong><b>5. Inconsistent Color or Surface Finish<\/b><\/strong><\/h3><p><strong><b>Symptoms:<\/b><\/strong>\u00a0Color variation, streaks, or dull surface.<br \/><strong><b>Possible causes:<\/b><\/strong><\/p><ul><li>Poor pigment mixing<\/li><li>Inconsistent raw material supply<\/li><li>Mold contamination<\/li><\/ul><p><strong><b>Solution:<\/b><\/strong><br \/>Improve pigment dispersion and mixing accuracy. Stabilize feeding system. Clean molds regularly.<\/p><h2><strong><b>Key Maintenance Tips<\/b><\/strong><\/h2><ul><li>Regularly clean the mixing head to avoid material buildup<\/li><li>Check seals, valves, and pipelines for leaks<\/li><li>Calibrate metering pumps periodically<\/li><li>Maintain stable workshop temperature and humidity<\/li><li>Train operators to follow standard procedures<\/li><\/ul><p>Consistent maintenance reduces most production issues before they happen.<\/p><h2><strong><b>How to Choose the Right PU Machine Setup<\/b><\/strong><\/h2><p>Troubleshooting often comes back to machine configuration. A well-designed system reduces problems from the start.<\/p><p>When selecting or upgrading equipment, consider:<\/p><ul><li>Accuracy of metering and mixing system<\/li><li>Stability of temperature control<\/li><li>Quality of mixing head (high-pressure vs low-pressure)<\/li><li>Automation level and ease of operation<\/li><li>Availability of remote support and spare parts<\/li><\/ul><p>For factories planning expansion or new projects, a complete PU production line with proper layout design can significantly improve efficiency and reduce long-term maintenance costs.<\/p><h2><strong><b>FAQ<\/b><\/strong><\/h2><p><strong><b>What is a PU shoe injection machine?<\/b><\/strong><br \/>It is a machine that mixes and injects polyurethane \u0645\u0648\u0627\u062f into molds to form shoe soles, commonly used in safety shoes and industrial footwear production.<\/p><p><strong><b>How does it work?<\/b><\/strong><br \/>The machine precisely meters and mixes two main components (polyol and isocyanate), then injects the mixture into a mold where it reacts and forms foam or solid PU.<\/p><p><strong><b>What is the typical lifespan?<\/b><\/strong><br \/>With proper maintenance, key components can last many years. Mixing heads and seals may require periodic replacement depending on usage.<\/p><p><strong><b>What is the best setup for stable production?<\/b><\/strong><br \/>A system with accurate dosing, stable temperature control, and a reliable mixing head is essential. Automation and operator training also play a big role.<\/p><p><strong><b>What are the most common issues?<\/b><\/strong><br \/>Foam defects, bonding problems, and injection instability are the most frequent. Most can be traced back to material control, machine calibration, or maintenance.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-9643509 e-flex e-con-boxed e-con e-parent\" data-id=\"9643509\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-a16d63c elementor-widget elementor-widget-image\" data-id=\"a16d63c\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t\t\t\t\t\t\t\t\t<figure class=\"wp-caption\">\n\t\t\t\t\t\t\t\t\t\t\t<a href=\"https:\/\/haifengmachine.com\/solutions\/\">\n\t\t\t\t\t\t\t<img fetchpriority=\"high\" decoding=\"async\" width=\"800\" height=\"800\" src=\"https:\/\/haifengmachine.com\/wp-content\/uploads\/2026\/03\/R-C-8.jpg\" class=\"attachment-large size-large wp-image-3790\" alt=\"\" srcset=\"https:\/\/haifengmachine.com\/wp-content\/uploads\/2026\/03\/R-C-8.jpg 800w, https:\/\/haifengmachine.com\/wp-content\/uploads\/2026\/03\/R-C-8-300x300.jpg 300w, https:\/\/haifengmachine.com\/wp-content\/uploads\/2026\/03\/R-C-8-150x150.jpg 150w, https:\/\/haifengmachine.com\/wp-content\/uploads\/2026\/03\/R-C-8-768x768.jpg 768w\" sizes=\"(max-width: 800px) 100vw, 800px\" title=\"\">\t\t\t\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t\t\t\t<figcaption class=\"widget-image-caption wp-caption-text\">Footwear Solutions<\/figcaption>\n\t\t\t\t\t\t\t\t\t\t<\/figure>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"<p>PU Shoe Injection Machine<\/p>","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[1],"tags":[],"table_tags":[],"class_list":["post-5143","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"acf":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/haifengmachine.com\/ko\/wp-json\/wp\/v2\/posts\/5143","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/haifengmachine.com\/ko\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/haifengmachine.com\/ko\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/haifengmachine.com\/ko\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/haifengmachine.com\/ko\/wp-json\/wp\/v2\/comments?post=5143"}],"version-history":[{"count":5,"href":"https:\/\/haifengmachine.com\/ko\/wp-json\/wp\/v2\/posts\/5143\/revisions"}],"predecessor-version":[{"id":5148,"href":"https:\/\/haifengmachine.com\/ko\/wp-json\/wp\/v2\/posts\/5143\/revisions\/5148"}],"wp:attachment":[{"href":"https:\/\/haifengmachine.com\/ko\/wp-json\/wp\/v2\/media?parent=5143"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/haifengmachine.com\/ko\/wp-json\/wp\/v2\/categories?post=5143"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/haifengmachine.com\/ko\/wp-json\/wp\/v2\/tags?post=5143"},{"taxonomy":"table_tags","embeddable":true,"href":"https:\/\/haifengmachine.com\/ko\/wp-json\/wp\/v2\/table_tags?post=5143"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}