{"id":12493,"date":"2026-04-30T07:39:43","date_gmt":"2026-04-30T07:39:43","guid":{"rendered":"https:\/\/ideal-pro.com\/?p=12493"},"modified":"2026-04-30T08:24:11","modified_gmt":"2026-04-30T08:24:11","slug":"fix-injection-molding-surface-gloss-defects","status":"publish","type":"post","link":"https:\/\/ideal-pro.com\/ja\/fix-injection-molding-surface-gloss-defects\/","title":{"rendered":"Troubleshooting Guide: How to Fix Poor Surface Gloss in Injection Molding"},"content":{"rendered":"<p>Achieving the perfect surface finish in <a href=\"https:\/\/ideal-pro.com\/ja\/\u30d7\u30e9\u30b9\u30c1\u30c3\u30af\u5c04\u51fa\u6210\u5f62\/\" target=\"_blank\" rel=\"noopener noreferrer\">\u30d7\u30e9\u30b9\u30c1\u30c3\u30af\u5c04\u51fa\u6210\u5f62<\/a> is critical for product quality. However, manufacturers often encounter <strong>surface gloss defects<\/strong>, resulting in dull, matte, or uneven finishes.<\/p>\n<p>Generally, these defects stem from three main categories: <strong>Mold Faults<\/strong>, <strong>Improper Molding Conditions<\/strong>, \u305d\u3057\u3066 <strong>Raw Material Issues<\/strong>. This guide breaks down each cause and provides actionable solutions.<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/ideal-pro.com\/wp-content\/uploads\/2026\/04\/2-3-8.jpg\" alt=\"Comparison of good and bad surface gloss on injection molded parts\"><\/p>\n<hr>\n<h2>Mold Faults and Design Issues<\/h2>\n<p>Since the plastic part is a reproduction of the mold cavity, the condition of the mold is paramount. If the mold surface has scratches, corrosion, or micropores, these imperfections will be replicated on the plastic part.<\/p>\n<h3>Common Mold-Related Causes:<\/h3>\n<ul>\n<li><strong>\u8868\u9762\u4ed5\u4e0a\u3052\uff1a<\/strong> The cavity surface must have excellent smoothness. Polishing or chrome plating the cavity surface is recommended.<\/li>\n<li><strong>Contamination:<\/strong> Oil, moisture, or excessive release agent on the cavity surface can cause darkening. Keep the mold clean and use release agents sparingly and correctly.<\/li>\n<li><strong>Mold Temperature:<\/strong> This is a critical factor.\n<ul>\n<li><em>Too Low:<\/em> The melt solidifies instantly upon contact, preventing the plastic from replicating the mold's texture, leading to poor gloss.<\/li>\n<li><em>Solution:<\/em> Increase the <a href=\"https:\/\/ideal-pro.com\/ja\/injection-molding-shrinkage-how-temperature-speed-affect-quality\/\" target=\"_blank\" rel=\"noopener noreferrer\">mold temperature<\/a>. Using warm water in the cooling circuit helps transfer heat quickly without extending the cycle time significantly.<\/li>\n<\/ul><\/li>\n<li><strong>Design Flaws:<\/strong> Small draft angles, sudden changes in wall thickness, overly thick ribs, or small gates can cause turbulence or poor flow. Poor venting also traps air, affecting the finish.<\/li>\n<\/ul>\n<p><img decoding=\"async\" src=\"https:\/\/ideal-pro.com\/wp-content\/uploads\/2026\/04\/2-4-6.jpg\" alt=\"Polishing injection mold cavity to improve surface finish.\"><\/p>\n<hr>\n<h2>Improper Control of Molding Conditions<\/h2>\n<p>Even with a perfect mold, incorrect machine settings can ruin the surface finish. Parameters such as speed, pressure, and temperature must be balanced.<\/p>\n<h3>Key Adjustments:<\/h3>\n<ul>\n<li><strong>Injection Speed &amp; Pressure:<\/strong> If the speed is too fast or too slow, or if injection pressure is too low, the surface may appear dull.<\/li>\n<li><strong>Holding Pressure &amp; Time:<\/strong> Insufficient holding time or pressure prevents the material from packing tightly against the mold surface.<\/li>\n<li><strong>Nozzle Temperature:<\/strong> A cold nozzle or low barrel temperature results in poor plasticization.<\/li>\n<li><strong>Fiber Reinforcement:<\/strong> For reinforced plastics, <a href=\"https:\/\/ideal-pro.com\/ja\/why-back-pressure-is-critical-in-injection-molding-a-technical-guide-for-process-optimization\/\" target=\"_blank\" rel=\"noopener noreferrer\">poor dispersion of fillers<\/a> can lead to a \"silver foil\" appearance or exposed fibers.<\/li>\n<\/ul>\n<p><strong>Troubleshooting Specific Symptoms:<\/strong><\/p>\n<ul>\n<li><strong>Dark areas near the gate:<\/strong> Try reducing <a href=\"https:\/\/ideal-pro.com\/ja\/how-injection-speed-profiling-affects-injection-molding-part-quality-a-technical-guide\/\" target=\"_blank\" rel=\"noopener noreferrer\">injection speed<\/a>, relocating the gate, increasing gate size, or adding fillet transitions at thickness changes.<\/li>\n<li><strong>Milky white layer:<\/strong> Usually indicates the injection speed is too high; reduce it slightly.<\/li>\n<li><strong>Filler Dispersion Issues:<\/strong> Switch to a resin with better flow or use a screw with stronger mixing capabilities.<\/li>\n<\/ul>\n<p><img decoding=\"async\" src=\"https:\/\/ideal-pro.com\/wp-content\/uploads\/2026\/04\/2-1-10.jpg\" alt=\"Adjusting injection molding machine parameters for better gloss.\"><\/p>\n<hr>\n<h2>Raw Material Incompatibility<\/h2>\n<p>Sometimes the issue lies within the plastic pellets themselves. Using materials that do not meet processing requirements is a common cause of gloss failure.<\/p>\n<h3>Material Checklist:<\/h3>\n<table>\n<thead>\n<tr>\n<th style=\"text-align: left;\">Issue Category<\/th>\n<th style=\"text-align: left;\">Cause<\/th>\n<th style=\"text-align: left;\">Recommended Solution<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td style=\"text-align: left;\"><strong>Moisture<\/strong><\/td>\n<td style=\"text-align: left;\">High moisture or volatile content creates condensation between melt and mold.<\/td>\n<td style=\"text-align: left;\">Pre-dry the raw material thoroughly.<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\"><strong>Degradation<\/strong><\/td>\n<td style=\"text-align: left;\">Resin or colorant decomposition due to heat.<\/td>\n<td style=\"text-align: left;\">Use higher temperature-resistant resins\/colorants.<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\"><strong>Flow Rate<\/strong><\/td>\n<td style=\"text-align: left;\">Material viscosity is too high (poor flow).<\/td>\n<td style=\"text-align: left;\">Switch to free-flowing resin, add lubricant, or increase temp.<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\"><strong>Contamination<\/strong><\/td>\n<td style=\"text-align: left;\">Mixed foreign materials or incompatible polymers.<\/td>\n<td style=\"text-align: left;\">Replace with virgin\/new material.<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\"><strong>Particle Size<\/strong><\/td>\n<td style=\"text-align: left;\">Uneven particle size distribution.<\/td>\n<td style=\"text-align: left;\">Sieve the material to remove outliers.<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\"><strong>Crystallinity<\/strong><\/td>\n<td style=\"text-align: left;\">Uneven cooling in crystalline resins (e.g., PP, PE).<\/td>\n<td style=\"text-align: left;\">Control mold temp carefully; cool thick parts in a cold press immediately after ejection.<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\"><strong>Recycled Material<\/strong><\/td>\n<td style=\"text-align: left;\">Too high a percentage of regrind affects uniformity.<\/td>\n<td style=\"text-align: left;\">Reduce the ratio of recycled material.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><img decoding=\"async\" src=\"https:\/\/ideal-pro.com\/wp-content\/uploads\/2026\/04\/2-2-11.jpg\" alt=\"Plastic raw materials and regrind affecting injection molding quality.\"><\/p>\n<hr>\n<h3>Summary<\/h3>\n<p>Fixing surface gloss defects requires a systematic approach. Start by inspecting the <strong>mold surface and temperature<\/strong>, then optimize your <strong>injection parameters<\/strong> (speed\/pressure), and finally, verify the quality and dryness of your <strong>raw materials<\/strong>.<\/p>","protected":false},"excerpt":{"rendered":"<p>Achieving the perfect surface finish in plastic injection molding is critical for product quality. However, manufacturers often encounter surface gloss [&hellip;]<\/p>\n","protected":false},"author":2,"featured_media":12499,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_seopress_robots_primary_cat":"none","_seopress_titles_title":"Troubleshooting Guide: How to Fix Poor Surface Gloss in Injection Molding","_seopress_titles_desc":"Struggling with dull plastic parts? Discover the root causes of poor surface gloss in injection molding\u2014from mold faults to material issues\u2014and how to fix them.","_seopress_robots_index":"","site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"default","adv-header-id-meta":"","stick-header-meta":"default","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"set","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[21],"tags":[36,130],"class_list":["post-12493","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-blog","tag-injection-molding","tag-plastic-manufacturing"],"acf":[],"_links":{"self":[{"href":"https:\/\/ideal-pro.com\/ja\/wp-json\/wp\/v2\/posts\/12493","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ideal-pro.com\/ja\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ideal-pro.com\/ja\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ideal-pro.com\/ja\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/ideal-pro.com\/ja\/wp-json\/wp\/v2\/comments?post=12493"}],"version-history":[{"count":3,"href":"https:\/\/ideal-pro.com\/ja\/wp-json\/wp\/v2\/posts\/12493\/revisions"}],"predecessor-version":[{"id":12503,"href":"https:\/\/ideal-pro.com\/ja\/wp-json\/wp\/v2\/posts\/12493\/revisions\/12503"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/ideal-pro.com\/ja\/wp-json\/wp\/v2\/media\/12499"}],"wp:attachment":[{"href":"https:\/\/ideal-pro.com\/ja\/wp-json\/wp\/v2\/media?parent=12493"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ideal-pro.com\/ja\/wp-json\/wp\/v2\/categories?post=12493"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ideal-pro.com\/ja\/wp-json\/wp\/v2\/tags?post=12493"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}