{"id":2903,"date":"2026-08-10T10:35:32","date_gmt":"2026-08-10T02:35:32","guid":{"rendered":"http:\/\/0"},"modified":"2026-08-04T17:53:22","modified_gmt":"2026-08-04T09:53:22","slug":"specs-for-injection-molding-surface-finishing-spi-standards","status":"publish","type":"post","link":"https:\/\/www.jcinjectionmolding.com\/pt\/blog\/specs-for-injection-molding-surface-finishing-spi-standards\/","title":{"rendered":"Specs for Injection Molding Surface Finishing: SPI Standards"},"content":{"rendered":"<article style=\"font-family: -apple-system, BlinkMacSystemFont, &#039;Segoe UI&#039;, Roboto, Helvetica, Arial, sans-serif;color: #333333;width: 100%\">\n<section style=\"margin-bottom: 30px\">\n<p style=\"font-size: 18px;line-height: 1.8em;text-align: left;margin-bottom: 24px\">Elevating plastic hardware aesthetics, tactile ergonomics, and electromagnetic performance requires comprehensive post-molding decoration and cavity surface conditioning. Standard raw molded plastic parts frequently display flow lines, parting line seams, or ejection pin marks that compromise visual quality. Applying specialized mold textures, diamond mirror polishes, conductive coatings, or multi-color pad printing transforms bare polymer parts into market-ready retail components. This technical guide reviews SPI polishing standards, VDI texturing, secondary printing methods, and EMI\/RFI shielding technologies.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-2906\" src=\"https:\/\/www.jcinjectionmolding.com\/wp-content\/uploads\/2026\/08\/inspecting-finished-plastic-parts.webp\" alt=\"inspecting-finished-plastic-parts\" width=\"1376\" height=\"768\" srcset=\"https:\/\/www.jcinjectionmolding.com\/wp-content\/uploads\/2026\/08\/inspecting-finished-plastic-parts.webp 1376w, https:\/\/www.jcinjectionmolding.com\/wp-content\/uploads\/2026\/08\/inspecting-finished-plastic-parts-300x167.webp 300w, https:\/\/www.jcinjectionmolding.com\/wp-content\/uploads\/2026\/08\/inspecting-finished-plastic-parts-1024x572.webp 1024w, https:\/\/www.jcinjectionmolding.com\/wp-content\/uploads\/2026\/08\/inspecting-finished-plastic-parts-768x429.webp 768w\" sizes=\"auto, (max-width: 1376px) 100vw, 1376px\" \/><\/p>\n<\/section>\n<p><!-- Table of Contents --><\/p>\n<section style=\"background-color: #f8f9fa;border-left: 4px solid #0056b3;padding: 24px;border-radius: 6px;margin: 40px 0\">\n<h3 style=\"font-size: 22px;font-weight: bold;line-height: 1.5em;margin-top: 0;margin-bottom: 16px;color: #111111\">\u00cdndice<\/h3>\n<ul style=\"list-style-type: none;padding-left: 0;margin: 0\">\n<li style=\"margin-bottom: 12px\"><a style=\"color: #0056b3;text-decoration: none;font-size: 17px;font-weight: 500\" href=\"#spi-vdi-finishes\">1. SPI Mold Polishing (A-1 Mirror Finish) &amp; VDI \/ Mold-Tech Texturing<\/a><\/li>\n<li style=\"margin-bottom: 12px\"><a style=\"color: #0056b3;text-decoration: none;font-size: 17px;font-weight: 500\" href=\"#secondary-operations\">2. Secondary Ops: Pad Printing, Silk Screening, Laser Engraving &amp; Painting<\/a><\/li>\n<li style=\"margin-bottom: 0\"><a style=\"color: #0056b3;text-decoration: none;font-size: 17px;font-weight: 500\" href=\"#emi-shielding\">3. Conductive EMI\/RFI Shielding Coatings for Electronic Enclosures<\/a><\/li>\n<\/ul>\n<\/section>\n<p><!-- Section 1 --><\/p>\n<section id=\"spi-vdi-finishes\" style=\"margin-bottom: 50px\">\n<h2 style=\"font-size: 28px;line-height: 1.5em;font-weight: bold;margin-top: 40px;margin-bottom: 24px;color: #111111;border-bottom: 1px solid #eaeaea;padding-bottom: 8px\">SPI Mold Polishing (A-1 Mirror Finish) &amp; VDI \/ Mold-Tech Texturing<\/h2>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-2904\" src=\"https:\/\/www.jcinjectionmolding.com\/wp-content\/uploads\/2026\/08\/vdi-mold-cavity-texturing.webp\" alt=\"vdi-mold-cavity-texturing\" width=\"1376\" height=\"768\" srcset=\"https:\/\/www.jcinjectionmolding.com\/wp-content\/uploads\/2026\/08\/vdi-mold-cavity-texturing.webp 1376w, https:\/\/www.jcinjectionmolding.com\/wp-content\/uploads\/2026\/08\/vdi-mold-cavity-texturing-300x167.webp 300w, https:\/\/www.jcinjectionmolding.com\/wp-content\/uploads\/2026\/08\/vdi-mold-cavity-texturing-1024x572.webp 1024w, https:\/\/www.jcinjectionmolding.com\/wp-content\/uploads\/2026\/08\/vdi-mold-cavity-texturing-768x429.webp 768w\" sizes=\"auto, (max-width: 1376px) 100vw, 1376px\" \/><\/p>\n<p style=\"font-size: 18px;line-height: 1.8em;text-align: left;margin-bottom: 24px\">Specifying professional <a href=\"https:\/\/www.jcinjectionmolding.com\/pt\/service\/surface-finishes\/\"><strong>injection molding surface finishing<\/strong><\/a> begins during mold cavity toolmaking. Cavity surface preparation follows international Society of the Plastics Industry (SPI) polishing standards. Achieving an <strong>SPI A-1 mirror finish<\/strong> requires progressive hand-polishing using diamond paste compounds on hardened <strong>S136 stainless steel<\/strong>, eliminating micro-scratches for optical lenses and high-gloss <strong>polycarbonate (PC)<\/strong> covers. Applying <strong>VDI 3400 texturing<\/strong> ou <strong>Mold-Tech chemical etching<\/strong> imparts controlled matte, leather, or geometric textures directly onto mold cavity faces. Chemical texturing masks flow lines and sink mark shadows while enhancing tactile grip on consumer electronic housings.<\/p>\n<p><!-- Numbered List --><\/p>\n<p style=\"font-size: 18px;line-height: 1.8em;text-align: left;margin-bottom: 16px\">Mold cavity surface finishing standards include:<\/p>\n<ol style=\"font-size: 18px;line-height: 1.8em;margin-bottom: 24px;padding-left: 24px;list-style-type: decimal\">\n<li style=\"margin-bottom: 12px;text-align: left\"><strong>SPI A-1 diamond polishing<\/strong>\u2014Lapping hardened steel with 3-micron diamond paste creates a high-gloss optical mirror surface.<\/li>\n<li style=\"margin-bottom: 12px;text-align: left\"><strong>VDI 3400 spark erosion texturing<\/strong>\u2014Electrical discharge machining produces controlled matte micro-textures ranging from VDI 12 to VDI 36.<\/li>\n<li style=\"margin-bottom: 12px;text-align: left\"><strong>Mold-Tech chemical etching<\/strong>\u2014Acid etching creates complex leather, woodgrain, or geometric patterns directly on cavity steel.<\/li>\n<li style=\"margin-bottom: 12px;text-align: left\"><strong>Draft angle compensation<\/strong>\u2014Increasing vertical draft by 1\u00b0 for every 0.025 mm of texture depth ensures clean part ejection without scuffing.<\/li>\n<\/ol>\n<\/section>\n<p><!-- Section 2 --><\/p>\n<section id=\"secondary-operations\" style=\"margin-bottom: 50px\">\n<h2 style=\"font-size: 28px;line-height: 1.5em;font-weight: bold;margin-top: 40px;margin-bottom: 24px;color: #111111;border-bottom: 1px solid #eaeaea;padding-bottom: 8px\">Secondary Ops: Pad Printing, Silk Screening, Laser Engraving &amp; Painting<\/h2>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-2908\" src=\"https:\/\/www.jcinjectionmolding.com\/wp-content\/uploads\/2026\/08\/pad-printing-plastic-housing.webp\" alt=\"pad-printing-plastic-housing\" width=\"1376\" height=\"768\" srcset=\"https:\/\/www.jcinjectionmolding.com\/wp-content\/uploads\/2026\/08\/pad-printing-plastic-housing.webp 1376w, https:\/\/www.jcinjectionmolding.com\/wp-content\/uploads\/2026\/08\/pad-printing-plastic-housing-300x167.webp 300w, https:\/\/www.jcinjectionmolding.com\/wp-content\/uploads\/2026\/08\/pad-printing-plastic-housing-1024x572.webp 1024w, https:\/\/www.jcinjectionmolding.com\/wp-content\/uploads\/2026\/08\/pad-printing-plastic-housing-768x429.webp 768w\" sizes=\"auto, (max-width: 1376px) 100vw, 1376px\" \/><\/p>\n<p style=\"font-size: 18px;line-height: 1.8em;text-align: left;margin-bottom: 24px\">Secondary post-molding operations add functional symbols, branding logos, and protective coatings to molded <strong>ABS<\/strong> ou <a href=\"https:\/\/www.jcinjectionmolding.com\/pt\/materials\/abs\/\"><strong>PC\/ABS<\/strong><\/a> parts. Utilizing multi-color <strong>pad printing<\/strong> transfers silicone pad ink onto complex three-dimensional curves and textured surfaces seamlessly. Laser engraving burns away superficial paint coats on backlit buttons, creating precise, light-transmitting symbols. Automated liquid spray painting and UV hard-coat applications improve scratch resistance and chemical immunity on automotive interior trims.<\/p>\n<\/section>\n<p><!-- Section 3 --><\/p>\n<section id=\"emi-shielding\" style=\"margin-bottom: 50px\">\n<h2 style=\"font-size: 28px;line-height: 1.5em;font-weight: bold;margin-top: 40px;margin-bottom: 24px;color: #111111;border-bottom: 1px solid #eaeaea;padding-bottom: 8px\">Conductive EMI\/RFI Shielding Coatings for Electronic Enclosures<\/h2>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-2905\" src=\"https:\/\/www.jcinjectionmolding.com\/wp-content\/uploads\/2026\/08\/conductive-emi-shielding-coating.webp\" alt=\"conductive-emi-shielding-coating\" width=\"1376\" height=\"768\" srcset=\"https:\/\/www.jcinjectionmolding.com\/wp-content\/uploads\/2026\/08\/conductive-emi-shielding-coating.webp 1376w, https:\/\/www.jcinjectionmolding.com\/wp-content\/uploads\/2026\/08\/conductive-emi-shielding-coating-300x167.webp 300w, https:\/\/www.jcinjectionmolding.com\/wp-content\/uploads\/2026\/08\/conductive-emi-shielding-coating-1024x572.webp 1024w, https:\/\/www.jcinjectionmolding.com\/wp-content\/uploads\/2026\/08\/conductive-emi-shielding-coating-768x429.webp 768w\" sizes=\"auto, (max-width: 1376px) 100vw, 1376px\" \/><\/p>\n<p style=\"font-size: 18px;line-height: 1.8em;text-align: left;margin-bottom: 24px\">Electronic enclosures housing sensitive circuit boards require protection against electromagnetic interference. Applying conductive <strong>EMI\/RFI shielding coatings<\/strong> inside plastic housings prevents stray radio frequency signals from disrupting internal electronics. Specialized spray painting utilizes nickel, copper, or silver conductive paint formulations to form a continuous grounding barrier. Achieving low surface resistance below 0.1 \u03a9\/sq meets global FCC and CE electromagnetic compatibility regulations for medical and aerospace devices.<\/p>\n<p><!-- Table 1: Finishing Comparison Table --><\/p>\n<div style=\"margin: 32px 0\">\n<table style=\"width: 100%;border-collapse: collapse;font-size: 16px;text-align: left;min-width: 600px\">\n<thead>\n<tr style=\"background-color: #f8f9fa;border-bottom: 2px solid #dee2e6\">\n<th style=\"padding: 16px;border: 1px solid #dee2e6;font-weight: 600;color: #111111\">Surface Finishing Method<\/th>\n<th style=\"padding: 16px;border: 1px solid #dee2e6;font-weight: 600;color: #111111\">Roughness \/ Thickness<\/th>\n<th style=\"padding: 16px;border: 1px solid #dee2e6;font-weight: 600;color: #111111\">Compatible Substrate<\/th>\n<th style=\"padding: 16px;border: 1px solid #dee2e6;font-weight: 600;color: #111111\">Primary Aesthetic \/ Functional Benefit<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr style=\"border-bottom: 1px solid #dee2e6\">\n<td style=\"padding: 16px;border: 1px solid #dee2e6;color: #333333\">SPI A-1 Diamond Polish<\/td>\n<td style=\"padding: 16px;border: 1px solid #dee2e6;color: #333333\">Ra &lt; 0.012 \u03bcm<\/td>\n<td style=\"padding: 16px;border: 1px solid #dee2e6;color: #333333\">PC, PMMA, Optical Resins<\/td>\n<td style=\"padding: 16px;border: 1px solid #dee2e6;color: #333333\">High-gloss transparency for optical lenses &amp; light guides<\/td>\n<\/tr>\n<tr style=\"border-bottom: 1px solid #dee2e6\">\n<td style=\"padding: 16px;border: 1px solid #dee2e6;color: #333333\">VDI 24 Spark Texture<\/td>\n<td style=\"padding: 16px;border: 1px solid #dee2e6;color: #333333\">Ra = 1.6 \u03bcm<\/td>\n<td style=\"padding: 16px;border: 1px solid #dee2e6;color: #333333\">ABS, PC\/ABS, PP, PA66<\/td>\n<td style=\"padding: 16px;border: 1px solid #dee2e6;color: #333333\">Matte tactile finish masking sink marks &amp; scratches<\/td>\n<\/tr>\n<tr style=\"border-bottom: 1px solid #dee2e6\">\n<td style=\"padding: 16px;border: 1px solid #dee2e6;color: #333333\">Conductive Nickel Coating<\/td>\n<td style=\"padding: 16px;border: 1px solid #dee2e6;color: #333333\">25 &#8211; 50 \u03bcm dry film<\/td>\n<td style=\"padding: 16px;border: 1px solid #dee2e6;color: #333333\">ABS, PC\/ABS, PBT<\/td>\n<td style=\"padding: 16px;border: 1px solid #dee2e6;color: #333333\">EMI\/RFI shielding (&lt; 0.1 \u03a9\/sq) for electronic housings<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/section>\n<p><!-- FAQ Section --><\/p>\n<section id=\"faq\" style=\"margin-bottom: 40px\">\n<h2 style=\"font-size: 28px;line-height: 1.5em;font-weight: bold;margin-top: 40px;margin-bottom: 24px;color: #111111;border-bottom: 1px solid #eaeaea;padding-bottom: 8px\">Frequently Asked Questions (FAQs)<\/h2>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-2907\" src=\"https:\/\/www.jcinjectionmolding.com\/wp-content\/uploads\/2026\/08\/measuring-surface-roughness-ra.webp\" alt=\"measuring-surface-roughness-ra\" width=\"1376\" height=\"768\" srcset=\"https:\/\/www.jcinjectionmolding.com\/wp-content\/uploads\/2026\/08\/measuring-surface-roughness-ra.webp 1376w, https:\/\/www.jcinjectionmolding.com\/wp-content\/uploads\/2026\/08\/measuring-surface-roughness-ra-300x167.webp 300w, https:\/\/www.jcinjectionmolding.com\/wp-content\/uploads\/2026\/08\/measuring-surface-roughness-ra-1024x572.webp 1024w, https:\/\/www.jcinjectionmolding.com\/wp-content\/uploads\/2026\/08\/measuring-surface-roughness-ra-768x429.webp 768w\" sizes=\"auto, (max-width: 1376px) 100vw, 1376px\" \/><\/p>\n<div style=\"margin-bottom: 30px\">\n<h3 style=\"font-size: 22px;line-height: 1.5em;font-weight: bold;margin-top: 24px;margin-bottom: 12px;color: #111111\">What is the difference between SPI A-1 and VDI 24 surface finishes?<\/h3>\n<p style=\"font-size: 18px;line-height: 1.8em;text-align: left;margin-bottom: 24px\">SPI A-1 represents an optical diamond mirror finish polished to a smooth surface roughness Ra under 0.012 microns, ideal for transparent lenses. VDI 24 is a matte spark-erosion texture produced by electrical discharge machining, offering a medium tactile grip that masks cosmetic sink marks and scratch defects on opaque enclosures.<\/p>\n<\/div>\n<div style=\"margin-bottom: 30px\">\n<h3 style=\"font-size: 22px;line-height: 1.5em;font-weight: bold;margin-top: 24px;margin-bottom: 12px;color: #111111\">Why do textured mold cavities require larger draft angles than polished cavities?<\/h3>\n<p style=\"font-size: 18px;line-height: 1.8em;text-align: left;margin-bottom: 24px\">Textured cavity walls feature microscopic peaks and valleys that mechanically grip the shrinking plastic during cooling. Insufficient draft angles cause the plastic skin to drag against the textured steel during ejection, creating unsightly scuff marks. Adding 1\u00b0 of draft for every 0.025 mm of texture depth ensures smooth release without damaging the pattern.<\/p>\n<\/div>\n<div style=\"margin-bottom: 0\">\n<h3 style=\"font-size: 22px;line-height: 1.5em;font-weight: bold;margin-top: 24px;margin-bottom: 12px;color: #111111\">How do conductive spray coatings provide EMI shielding in plastic housings?<\/h3>\n<p style=\"font-size: 18px;line-height: 1.8em;text-align: left;margin-bottom: 24px\">Conductive spray coatings contain microscopic nickel, copper, or silver flakes suspended in a liquid binder. When sprayed onto the internal surfaces of a plastic enclosure, the metal particles form a continuous conductive grid. This metallic layer reflects and absorbs electromagnetic radiation, preventing high-frequency noise from interfering with delicate electronic components.<\/p>\n<\/div>\n<\/section>\n<\/article>","protected":false},"excerpt":{"rendered":"<p>Elevating plastic hardware aesthetics, tactile ergonomics, and electromagnetic performance requires comprehensive post-molding decoration and cavity surface conditioning. Standard raw molded plastic parts frequently display flow lines, parting line seams, or ejection pin marks that compromise visual quality. Applying specialized mold textures, diamond mirror polishes, conductive coatings, or multi-color pad printing transforms bare polymer parts into [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":2909,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-2903","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-blog"],"_links":{"self":[{"href":"https:\/\/www.jcinjectionmolding.com\/pt\/wp-json\/wp\/v2\/posts\/2903","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.jcinjectionmolding.com\/pt\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.jcinjectionmolding.com\/pt\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.jcinjectionmolding.com\/pt\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.jcinjectionmolding.com\/pt\/wp-json\/wp\/v2\/comments?post=2903"}],"version-history":[{"count":0,"href":"https:\/\/www.jcinjectionmolding.com\/pt\/wp-json\/wp\/v2\/posts\/2903\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.jcinjectionmolding.com\/pt\/wp-json\/wp\/v2\/media\/2909"}],"wp:attachment":[{"href":"https:\/\/www.jcinjectionmolding.com\/pt\/wp-json\/wp\/v2\/media?parent=2903"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.jcinjectionmolding.com\/pt\/wp-json\/wp\/v2\/categories?post=2903"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.jcinjectionmolding.com\/pt\/wp-json\/wp\/v2\/tags?post=2903"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}