{"id":19512,"date":"2024-05-10T14:03:14","date_gmt":"2024-05-10T06:03:14","guid":{"rendered":"https:\/\/firstmold.com\/?p=19512"},"modified":"2025-08-11T15:54:54","modified_gmt":"2025-08-11T07:54:54","slug":"black-spots-and-black-specks","status":"publish","type":"post","link":"https:\/\/firstmold.com\/pt\/tips\/black-spots-and-black-specks\/","title":{"rendered":"Pontos negros e manchas negras na moldagem por inje\u00e7\u00e3o"},"content":{"rendered":"<p>Hoje, continuarei a discutir os <a href=\"https:\/\/firstmold.com\/pt\/tips\/injection-molding-defects\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>defeitos na moldagem por inje\u00e7\u00e3o<\/strong><\/a>-pontos negros e manchas negras. Estes defeitos aparecem frequentemente na maioria dos processos de moldagem por inje\u00e7\u00e3o e, quanto mais elevados forem os requisitos do produto, mais dif\u00edcil \u00e9 controlar a propor\u00e7\u00e3o de pontos negros, o que pode levar a perdas significativas. Por conseguinte, a redu\u00e7\u00e3o da taxa de defeitos de pontos negros na produ\u00e7\u00e3o tornou-se uma forma importante de os fabricantes pouparem custos!<\/p>\n\n\n\n<p>A ocorr\u00eancia de pontos negros n\u00e3o tem qualquer rela\u00e7\u00e3o com o design do produto, mas os designers industriais devem aprender a identific\u00e1-los.<\/p>\n\n\n\n<figure class=\"wp-block-image aligncenter size-full\"><img fetchpriority=\"high\" decoding=\"async\" width=\"1200\" height=\"675\" src=\"https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/The-Injection-Molding-Research-Laboratory-is-investigating-the-causes-of-black-spot-defects.webp\" alt=\"O Laborat\u00f3rio de Investiga\u00e7\u00e3o de Moldagem por Inje\u00e7\u00e3o est\u00e1 a investigar as causas dos defeitos de pontos negros\" class=\"wp-image-31644\" srcset=\"https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/The-Injection-Molding-Research-Laboratory-is-investigating-the-causes-of-black-spot-defects.webp 1200w, https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/The-Injection-Molding-Research-Laboratory-is-investigating-the-causes-of-black-spot-defects-300x169.webp 300w, https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/The-Injection-Molding-Research-Laboratory-is-investigating-the-causes-of-black-spot-defects-1024x576.webp 1024w, https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/The-Injection-Molding-Research-Laboratory-is-investigating-the-causes-of-black-spot-defects-768x432.webp 768w, https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/The-Injection-Molding-Research-Laboratory-is-investigating-the-causes-of-black-spot-defects-18x10.webp 18w, https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/The-Injection-Molding-Research-Laboratory-is-investigating-the-causes-of-black-spot-defects-600x338.webp 600w\" sizes=\"(max-width: 1200px) 100vw, 1200px\" \/><\/figure>\n\n\n\n<p>Se estiver interessado noutros defeitos da moldagem por inje\u00e7\u00e3o, pode clicar na liga\u00e7\u00e3o abaixo para obter mais informa\u00e7\u00f5es.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table><tbody><tr><th class=\"has-text-align-center\" data-align=\"center\" colspan=\"5\">Compreender os diferentes defeitos de moldagem por inje\u00e7\u00e3o<\/th><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><a href=\"https:\/\/firstmold.com\/pt\/tips\/flash-in-injection-molding\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Flash<\/strong><\/a><\/td><td class=\"has-text-align-center\" data-align=\"center\"><a href=\"https:\/\/firstmold.com\/pt\/tips\/short-shot-in-injection-molding\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Tiro curto<\/strong><\/a><\/td><td class=\"has-text-align-center\" data-align=\"center\"><a href=\"https:\/\/firstmold.com\/pt\/tips\/sink-marks\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Marca de pia<\/strong><\/a><\/td><td class=\"has-text-align-center\" data-align=\"center\"><a href=\"https:\/\/firstmold.com\/pt\/tips\/warpage-in-injection-molding\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Deforma\u00e7\u00e3o\/Deforma\u00e7\u00e3o<\/strong><\/a><\/td><td class=\"has-text-align-center\" data-align=\"center\"><a href=\"https:\/\/firstmold.com\/pt\/tips\/burn-marks\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Marca de queimadura<\/strong><\/a><\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><a href=\"https:\/\/firstmold.com\/pt\/tips\/splay-marks-silver-streaks-in-injeciton-molding\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Marca de Splay\/Risco de Prata<\/strong><\/a><\/td><td class=\"has-text-align-center\" data-align=\"center\"><strong>Mancha escura\/mancha preta<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\"><a href=\"https:\/\/firstmold.com\/pt\/tips\/flow-marks\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Marca de fluxo<\/strong><\/a><\/td><td class=\"has-text-align-center\" data-align=\"center\"><a href=\"https:\/\/firstmold.com\/pt\/tips\/bubbles\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Bolha<\/strong><\/a><\/td><td class=\"has-text-align-center\" data-align=\"center\"><a href=\"https:\/\/firstmold.com\/pt\/tips\/weld-lines\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Linha de soldadura<\/strong><\/a><\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><a href=\"https:\/\/firstmold.com\/pt\/tips\/uneven-color-and-color-difference\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Diferen\u00e7a de cor\/Cor desigual<\/strong><\/a><\/td><td class=\"has-text-align-center\" data-align=\"center\"><strong><a href=\"https:\/\/firstmold.com\/pt\/tips\/ejector-pin-marks\/\" target=\"_blank\" rel=\"noreferrer noopener\">Marca do pino ejetor<\/a><\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\"><\/td><td class=\"has-text-align-center\" data-align=\"center\"><\/td><td class=\"has-text-align-center\" data-align=\"center\"><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"h-what-are-black-spots-and-black-specks-in-injection-molding\">O que s\u00e3o pontos negros e manchas negras na moldagem por inje\u00e7\u00e3o?<\/h2>\n\n\n\n<p>Os pontos negros referem-se a fen\u00f3menos de carboniza\u00e7\u00e3o localizados que se formam ao longo das linhas de soldadura do produto pl\u00e1stico, nervuras posteriores, sali\u00eancias ou perto dos cantos no final do fluxo. Os pontos negros podem tamb\u00e9m aparecer irregularmente em v\u00e1rios locais. Por vezes, estes pontos negros podem mesmo distribuir-se em linhas, formando linhas negras.<\/p>\n\n\n\n<figure class=\"wp-block-image aligncenter size-full\"><img decoding=\"async\" width=\"1280\" height=\"720\" src=\"https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Black-Specks-on-red-injection-molded-parts.webp\" alt=\"Manchas pretas em pe\u00e7as moldadas por inje\u00e7\u00e3o vermelhas\" class=\"wp-image-31640\" srcset=\"https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Black-Specks-on-red-injection-molded-parts.webp 1280w, https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Black-Specks-on-red-injection-molded-parts-300x169.webp 300w, https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Black-Specks-on-red-injection-molded-parts-1024x576.webp 1024w, https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Black-Specks-on-red-injection-molded-parts-768x432.webp 768w, https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Black-Specks-on-red-injection-molded-parts-18x10.webp 18w, https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Black-Specks-on-red-injection-molded-parts-600x338.webp 600w\" sizes=\"(max-width: 1280px) 100vw, 1280px\" \/><\/figure>\n\n\n\n<figure class=\"wp-block-image aligncenter size-full\"><img decoding=\"async\" width=\"1280\" height=\"720\" src=\"https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Black-spots-are-a-relatively-common-defect-in-injection-molding.webp\" alt=\"Os pontos negros s\u00e3o um defeito relativamente comum na moldagem por inje\u00e7\u00e3o\" class=\"wp-image-31641\" srcset=\"https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Black-spots-are-a-relatively-common-defect-in-injection-molding.webp 1280w, https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Black-spots-are-a-relatively-common-defect-in-injection-molding-300x169.webp 300w, https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Black-spots-are-a-relatively-common-defect-in-injection-molding-1024x576.webp 1024w, https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Black-spots-are-a-relatively-common-defect-in-injection-molding-768x432.webp 768w, https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Black-spots-are-a-relatively-common-defect-in-injection-molding-18x10.webp 18w, https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Black-spots-are-a-relatively-common-defect-in-injection-molding-600x338.webp 600w\" sizes=\"(max-width: 1280px) 100vw, 1280px\" \/><\/figure>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-distribution-characteristics-of-black-spots\">Caracter\u00edsticas de distribui\u00e7\u00e3o dos pontos negros<\/h3>\n\n\n\n<p>Os pontos negros e as impurezas s\u00e3o caracterizados por pequenas part\u00edculas pretas ou castanhas, geralmente n\u00e3o reflectoras, e quando grandes, as impurezas aparecem em camadas, quebradi\u00e7as, facilmente quebr\u00e1veis e porosas ap\u00f3s a quebra. Existem duas caracter\u00edsticas principais na sua distribui\u00e7\u00e3o:<\/p>\n\n\n\n<p>A. Algumas distribuem-se irregularmente por todo o territ\u00f3rio, outras s\u00e3o localmente irregulares e, por vezes, s\u00f3 aparecem ocasionalmente numa zona espec\u00edfica.<\/p>\n\n\n\n<p>B. Estes pontos negros e impurezas aparecem, por vezes, apenas \u00e0 superf\u00edcie do produto e, por vezes, tanto \u00e0 superf\u00edcie como nas camadas mais profundas. No entanto, os pontos negros internos mais pr\u00f3ximos da superf\u00edcie s\u00e3o mais claros do que os da superf\u00edcie e os pontos negros mais profundos n\u00e3o s\u00e3o de todo vis\u00edveis.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"h-how-to-identify-black-spots\">Como identificar os pontos negros? <\/h2>\n\n\n\n<p>Alguns poder\u00e3o perguntar-se: os pontos negros precisam de ser identificados? Os pontos negros n\u00e3o s\u00e3o apenas pontos que diferem na cor do pr\u00f3prio produto a que todos chamamos pontos negros? Se observar o seu produto num microsc\u00f3pio com uma amplia\u00e7\u00e3o de 200 vezes, \u00e9 quase imposs\u00edvel distinguir um produto que n\u00e3o tenha quaisquer pontos de cor diferente (completamente de uma s\u00f3 cor). Ap\u00f3s a amplia\u00e7\u00e3o, ver\u00e1 muitos pontos negros de cores diferentes na superf\u00edcie do produto... Por conseguinte, deve haver um padr\u00e3o para avaliar qualquer produto.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-standards-for-judging-black-spots\">Normas de avalia\u00e7\u00e3o dos pontos negros<\/h3>\n\n\n\n<p>De onde v\u00eam as normas? Para os fornecedores de moldagem por inje\u00e7\u00e3o, \u00e9 essencial ter a no\u00e7\u00e3o clara de duas normas:<\/p>\n\n\n\n<p>A. Normas de controlo de pontos negros fornecidas pelo fornecedor das mat\u00e9rias-primas. <\/p>\n\n\n\n<p>B. As normas de inspe\u00e7\u00e3o da apar\u00eancia dos clientes correspondentes do produto (normas de controlo dos pontos negros).<\/p>\n\n\n\n<p>Se os padr\u00f5es de controlo das manchas de cores diferentes da mat\u00e9ria-prima forem inferiores aos padr\u00f5es de controlo do cliente para o aspeto do produto, pode haver uma taxa significativa de defeitos nas manchas de cores diferentes durante a produ\u00e7\u00e3o. Assim, os fornecedores de moldagem por inje\u00e7\u00e3o t\u00eam de garantir que as normas de controlo do material para as manchas de cores diferentes s\u00e3o consistentes com o produto <a href=\"https:\/\/firstmold.com\/pt\/tips\/quality-and-acceptance-standards-for-injection-molded-parts\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>normas de aceita\u00e7\u00e3o dos clientes<\/strong><\/a> (de prefer\u00eancia mais rigorosas do que as normas do cliente).<\/p>\n\n\n\n<p><em>Sugest\u00f5es: Para conhecer as normas do cliente, pode clicar em \"<a href=\"https:\/\/firstmold.com\/pt\/tips\/quality-and-acceptance-standards-for-injection-molded-parts\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>Normas de aceita\u00e7\u00e3o de pe\u00e7as moldadas por inje\u00e7\u00e3o<\/strong><\/a>\" para saber mais.<\/em><\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-methods-to-identify-black-spots\">M\u00e9todos de identifica\u00e7\u00e3o de pontos negros <\/h3>\n\n\n\n<p>As formas normalmente observadas s\u00e3o diferentes; a maior parte do que \u00e9 visto a olho nu \u00e9 \"circular\", enquanto que, sob amplia\u00e7\u00e3o, podem ser vistas formas como escamosa, v\u00e1rios pontos agrupados, em forma de nuvem, em forma de tira, etc. Por isso, geralmente julgamos com base na \u00e1rea dos pontos. Isto significa que temos de inspecionar minuciosamente cada parte da superf\u00edcie do produto para detetar pontos negros? Isso pode consumir muito tempo. Normalmente, os clientes finais do produto t\u00eam um m\u00e9todo de inspe\u00e7\u00e3o padr\u00e3o: sob uma ilumina\u00e7\u00e3o padr\u00e3o, a uma dist\u00e2ncia padr\u00e3o entre o produto e os olhos, os produtos que n\u00e3o apresentem (pontos de cor diferente) num per\u00edodo de tempo padr\u00e3o s\u00e3o geralmente produtos qualificados.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-how-to-handle-black-spotted-injection-molded-parts\">Como lidar com pe\u00e7as moldadas por inje\u00e7\u00e3o com manchas negras <\/h3>\n\n\n\n<p>Todas as pe\u00e7as moldadas por inje\u00e7\u00e3o que apresentem pontos negros, manchas negras ou linhas negras s\u00e3o consideradas como produtos defeituosos. Estas pe\u00e7as defeituosas devem ser imediatamente identificadas e separadas da produ\u00e7\u00e3o aceit\u00e1vel para evitar misturas. O tipo de defeito (ponto, mancha, linha) e a localiza\u00e7\u00e3o na pe\u00e7a devem ser documentados para efeitos de rastreabilidade e an\u00e1lise. A ocorr\u00eancia de pontos negros desencadeia uma investiga\u00e7\u00e3o obrigat\u00f3ria sobre a causa principal do processo de moldagem por inje\u00e7\u00e3o. Todas as ocorr\u00eancias de tais defeitos devem ser comunicadas ao Supervisor de Produ\u00e7\u00e3o e ao Departamento de Qualidade para an\u00e1lise e a\u00e7\u00e3o corretiva. As pe\u00e7as defeituosas confirmadas que contenham pontos negros s\u00e3o designadas para elimina\u00e7\u00e3o imediata ou retrabalho controlado (se aplic\u00e1vel e aprovado).<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"h-how-are-black-spots-formed\">Como se formam os pontos negros?<\/h2>\n\n\n\n<p>As fontes de pontos negros s\u00e3o geralmente de dois tipos: Carboniza\u00e7\u00e3o do material - degrada\u00e7\u00e3o do material a altas temperaturas (ou durante longos per\u00edodos); Contamina\u00e7\u00e3o - impurezas.<\/p>\n\n\n\n<figure class=\"wp-block-image aligncenter size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"1280\" height=\"720\" src=\"https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Causes-affecting-the-formation-of-black-spots-in-injection-molding.webp\" alt=\"Causas que afectam a forma\u00e7\u00e3o de pontos negros na moldagem por inje\u00e7\u00e3o\" class=\"wp-image-31642\" srcset=\"https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Causes-affecting-the-formation-of-black-spots-in-injection-molding.webp 1280w, https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Causes-affecting-the-formation-of-black-spots-in-injection-molding-300x169.webp 300w, https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Causes-affecting-the-formation-of-black-spots-in-injection-molding-1024x576.webp 1024w, https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Causes-affecting-the-formation-of-black-spots-in-injection-molding-768x432.webp 768w, https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Causes-affecting-the-formation-of-black-spots-in-injection-molding-18x10.webp 18w, https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Causes-affecting-the-formation-of-black-spots-in-injection-molding-600x338.webp 600w\" sizes=\"(max-width: 1280px) 100vw, 1280px\" \/><\/figure>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-carbonization\">Carboniza\u00e7\u00e3o <\/h3>\n\n\n\n<p>A maioria dos materiais com elevado teor de pol\u00edmeros tem de ser aquecida e cortada durante o processamento. Durante este processo, a carboniza\u00e7\u00e3o do material \u00e9 inevit\u00e1vel (100%). Para <a href=\"https:\/\/firstmold.com\/pt\/guides\/injection-molding-machine\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>m\u00e1quinas de moldagem por inje\u00e7\u00e3o<\/strong><\/a>No entanto, existem muitos locais que podem aumentar a probabilidade de carboniza\u00e7\u00e3o:<\/p>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"h-1-wear-on-the-screw-surface\">(1) Desgaste da superf\u00edcie do parafuso <\/h4>\n\n\n\n<p>O desgaste na superf\u00edcie do parafuso pode fazer com que a fus\u00e3o permane\u00e7a a\u00ed, levando \u00e0 carboniza\u00e7\u00e3o ao longo do tempo; <\/p>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"h-2-residual-molten-plastic\">(2) Res\u00edduos de pl\u00e1stico fundido <\/h4>\n\n\n\n<p>Em v\u00e1rios pontos de liga\u00e7\u00e3o da m\u00e1quina, como a cabe\u00e7a de foguete do parafuso, o bocal, <a href=\"https:\/\/firstmold.com\/pt\/tips\/types-of-flanges\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>flange<\/strong><\/a>etc., podem facilmente formar-se lacunas onde a fus\u00e3o pode permanecer e produzir pontos negros carbonizados.<\/p>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"h-3-long-production-cycles\">(3) Ciclos de produ\u00e7\u00e3o longos <\/h4>\n\n\n\n<p>Durante a produ\u00e7\u00e3o, ciclos longos ou m\u00e1quinas grandes (produtos pequenos) podem fazer com que o material permane\u00e7a demasiado tempo no barril, aumentando a probabilidade de carboniza\u00e7\u00e3o. <\/p>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"h-4-adhesion\">(4) Ader\u00eancia<\/h4>\n\n\n\n<p>Quando o pl\u00e1stico arrefecido \u00e9 fundido novamente, muitos materiais de engenharia (como o PC, que adere bem \u00e0s superf\u00edcies met\u00e1licas ap\u00f3s o arrefecimento) podem permanecer na superf\u00edcie met\u00e1lica mesmo quando reaquecidos. Com o tempo (a altas temperaturas), forma-se uma camada carbonizada. Esta \u00e9 uma fonte de defeitos de pontos negros na produ\u00e7\u00e3o. Por conseguinte, \u00e9 necess\u00e1rio isolar durante paragens curtas (&lt;4H) para evitar que o material no parafuso endure\u00e7a e adira, enquanto uma temperatura de isolamento mais baixa n\u00e3o conduzir\u00e1 \u00e0 carboniza\u00e7\u00e3o. Assim, a temperatura de isolamento recomendada \u00e9 geralmente cerca de 20 \u2103 -30 \u2103 acima do ponto de amolecimento (por exemplo, o ponto de amolecimento do PC \u00e9 cerca de 147 \u2103, com uma temperatura de isolamento recomendada de cerca de 180 \u2103). Durante as paradas, \u00e9 necess\u00e1rio expulsar o material do barril e passar um material menos propenso \u00e0 carboniza\u00e7\u00e3o pela m\u00e1quina antes de desligar diretamente a energia.<\/p>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"h-5-screw-capacity\">(5) Capacidade do parafuso<\/h4>\n\n\n\n<p>O tamanho do produto e o tamanho do parafuso determinam o tempo de perman\u00eancia. O facto de produtos pequenos se depararem com m\u00e1quinas grandes significa que o pr\u00f3prio material pode permanecer demasiado tempo no tambor. Um tempo prolongado pode fazer com que as pequenas mol\u00e9culas se degradem e carbonizem facilmente. Para a maioria dos materiais, um tempo de perman\u00eancia inferior a 5 minutos \u00e9 o ideal. O tempo m\u00e1ximo n\u00e3o deve exceder 15 minutos. Para dura\u00e7\u00f5es mais longas, \u00e9 conveniente baixar a temperatura na extremidade posterior do barril para reduzir o tempo a temperaturas elevadas. F\u00f3rmula de c\u00e1lculo do tempo de perman\u00eancia: <\/p>\n\n\n\n<p><em>Volume m\u00e1ximo de inje\u00e7\u00e3o da m\u00e1quina * densidade da massa fundida * ciclo * coeficiente (2,0-2,5) \/ peso do produto; ou Comprimento m\u00e1ximo de medi\u00e7\u00e3o * ciclo * coeficiente \/ (posi\u00e7\u00e3o de regula\u00e7\u00e3o do solvente - material de inje\u00e7\u00e3o residual)<\/em><\/p>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"h-6-connection-dead-angles\">(6) \u00c2ngulos mortos de liga\u00e7\u00e3o<\/h4>\n\n\n\n<p>No ponto de liga\u00e7\u00e3o entre o parafuso e a cabe\u00e7a do foguete, a flange, o bocal, etc., no interior do tambor, podem formar-se alguns \"\u00e2ngulos mortos\" onde a massa fundida n\u00e3o flui facilmente (permanece), causando longos tempos de espera e conduzindo \u00e0 degrada\u00e7\u00e3o e descolora\u00e7\u00e3o (resultando em algumas estrias amarelas, manchas pretas, etc.). Em primeiro lugar, durante a montagem, assegure-se de que o <a href=\"https:\/\/firstmold.com\/pt\/uncategorized\/types-of-threads\/\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>fios<\/strong><\/a> e montagem precisa, e a face da extremidade de contacto n\u00e3o deve ser danificada. Em caso de danos graves, \u00e9 necess\u00e1rio proceder \u00e0 sua substitui\u00e7\u00e3o!<\/p>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"h-7-surface-wear\">(7) Desgaste da superf\u00edcie<\/h4>\n\n\n\n<p>As superf\u00edcies irregulares s\u00e3o mais propensas ao desgaste da superf\u00edcie do parafuso, facilitando a \"perman\u00eancia\" do material do revestimento do parafuso, o que tem um impacto significativo nos defeitos de pontos negros. Os parafusos de tambor met\u00e1lico, dependendo do material, desgastam-se de forma diferente. Geralmente, o PC ou o PMMA requerem um parafuso endurecido (revestido). Para materiais com enchimento (fibra de vidro, p\u00f3 mineral), \u00e9 necess\u00e1rio um parafuso de liga met\u00e1lica. E mesmo com um parafuso de liga met\u00e1lica, este tem de ser substitu\u00eddo ap\u00f3s um determinado per\u00edodo de tempo!<\/p>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"h-8-chemical-corrosion\">(8) Corros\u00e3o qu\u00edmica<\/h4>\n\n\n\n<p>\u00c1gua corrosiva, CO2, O2, halogenetos de hidrog\u00e9nio - como o \u00e1cido clor\u00eddrico, res\u00edduos \u00e1cidos, electr\u00f3litos e outras impurezas. Durante o processo de processamento, a corros\u00e3o na superf\u00edcie do parafuso ou do tambor tamb\u00e9m pode fazer com que a superf\u00edcie \"permane\u00e7a\" e produza pontos negros. \u00c0 semelhan\u00e7a do desgaste, para materiais gerais, os parafusos nitretados comuns podem satisfazer os requisitos, mas para materiais \u00e0 prova de fogo, um parafuso (barril) com nitreta\u00e7\u00e3o + n\u00edvel de revestimento, ou mesmo tratamento de revestimento espesso, \u00e9 melhor para evitar a corros\u00e3o qu\u00edmica.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-contamination\">Contamina\u00e7\u00e3o<\/h3>\n\n\n\n<p>Ambiente de produ\u00e7\u00e3o: As cores de outras subst\u00e2ncias no ambiente externo podem ser diferentes e a sua resist\u00eancia \u00e0 temperatura pode ser inferior, o que facilita a produ\u00e7\u00e3o de pontos negros. Para materiais de cor clara, se produzidos num ambiente de oficina aberto, utilizando equipamento de secagem de ar quente comum. Neste caso, existem pelo menos dois problemas: <\/p>\n\n\n\n<p>A. Secagem a longo prazo, o ar aspirado do ambiente aberto e aquecido na tremonha, se exceder 16H, os materiais transparentes comuns podem transformar-se em part\u00edculas cinzentas claras... o que significa que a taxa de defeito pode atingir 100%. Na produ\u00e7\u00e3o normal, o ciclo da tremonha \u00e9 de 4-12H, mas a propor\u00e7\u00e3o de contamina\u00e7\u00e3o da entrada de ar \u00e9 ainda muito elevada. <\/p>\n\n\n\n<p>B. Durante a produ\u00e7\u00e3o, uma superf\u00edcie de molde comum, apenas aberta por um curto per\u00edodo de tempo, acumular\u00e1 muito p\u00f3 (a m\u00e1quina em si \u00e9 um dispositivo el\u00e9trico, embora esteja ligada \u00e0 terra, n\u00e3o pode ser \"0 est\u00e1tica\"), e o processo de produ\u00e7\u00e3o \u00e9 tamb\u00e9m um fator de \"manchas de cores diferentes\". Por conseguinte, para os produtos de cor clara, que exigem elevados padr\u00f5es de \"manchas de cor diferente\", recomenda-se a produ\u00e7\u00e3o numa sala limpa. <\/p>\n\n\n\n<p>Como j\u00e1 foi referido, as part\u00edculas de material s\u00e3o, na sua maioria, processadas por m\u00e1quinas, e elas pr\u00f3prias t\u00eam uma certa propor\u00e7\u00e3o de pontos negros (da\u00ed a necessidade de obter as normas do fabricante). Al\u00e9m disso, a capacidade do material para suportar altas temperaturas e oxida\u00e7\u00e3o a alta temperatura nestas formula\u00e7\u00f5es, em condi\u00e7\u00f5es em que a capacidade \u00e9 insuficiente, o processamento pode ser bastante doloroso, e pode ser f\u00e1cil encontrar amarelecimento (estrias), escurecimento (estrias, manchas) e outros problemas.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"h-how-to-improve-black-spots\">Como melhorar os pontos negros?<\/h2>\n\n\n\n<p>Anteriormente, discutimos o isolamento a curto prazo e algumas precau\u00e7\u00f5es e procedimentos durante as paragens directas. Mas a limpeza do parafuso do tambor requer aten\u00e7\u00e3o ao m\u00e9todo:<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-1-cleaning\">1. Limpeza<\/h3>\n\n\n\n<p>(1) Geralmente, podemos utilizar materiais relativamente duros para limpar o cilindro do parafuso, utilizando o princ\u00edpio da raspagem para limpar preliminarmente alguns dos res\u00edduos da superf\u00edcie, como o material PMMA (dureza relativamente elevada)! Por exemplo: PS n\u00e3o seco, PC (n\u00e3o seco e n\u00e3o derretido rapidamente, tamb\u00e9m um pouco mais duro), etc. <\/p>\n\n\n\n<p>(2) Para tipos de materiais cheios de limpeza, o material PC+GF pode ser usado para limpeza. Como a fibra de vidro (GF) \u00e9 s\u00f3lida sob faixas normais de temperatura de processamento (&lt;= 400 \u2103), todos n\u00f3s entendemos que o vidro \u00e9 muito duro. Nota, n\u00e3o use este m\u00e9todo em parafusos de material comum, pois isso causar\u00e1 desgaste severo. Observe que, durante a limpeza, lembre-se de aumentar repetidamente (20 \u2103) e diminuir (20 \u2103) a temperatura para limpeza. Princ\u00edpio: A, a mudan\u00e7a na viscosidade; B, a mudan\u00e7a na press\u00e3o interna, ambos podem tirar mais res\u00edduos.<\/p>\n\n\n\n<p>(3) Em caso de manchas negras graves, desmontar diretamente o tambor do parafuso para polir.<\/p>\n\n\n\n<figure class=\"wp-block-image aligncenter size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"1280\" height=\"720\" src=\"https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Use-transparent-plastic-materials-to-clean-the-screw-barrel-to-solve-the-problem-of-black-spot.webp\" alt=\"Utilizar materiais pl\u00e1sticos transparentes para limpar o tambor do parafuso e resolver o problema das manchas negras\" class=\"wp-image-31646\" srcset=\"https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Use-transparent-plastic-materials-to-clean-the-screw-barrel-to-solve-the-problem-of-black-spot.webp 1280w, https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Use-transparent-plastic-materials-to-clean-the-screw-barrel-to-solve-the-problem-of-black-spot-300x169.webp 300w, https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Use-transparent-plastic-materials-to-clean-the-screw-barrel-to-solve-the-problem-of-black-spot-1024x576.webp 1024w, https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Use-transparent-plastic-materials-to-clean-the-screw-barrel-to-solve-the-problem-of-black-spot-768x432.webp 768w, https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Use-transparent-plastic-materials-to-clean-the-screw-barrel-to-solve-the-problem-of-black-spot-18x10.webp 18w, https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Use-transparent-plastic-materials-to-clean-the-screw-barrel-to-solve-the-problem-of-black-spot-600x338.webp 600w\" sizes=\"(max-width: 1280px) 100vw, 1280px\" \/><\/figure>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-2-maintenance\">2. Manuten\u00e7\u00e3o<\/h3>\n\n\n\n<p>Durante as paragens: Como j\u00e1 foi referido, \u00e9 essencial limpar os materiais de produ\u00e7\u00e3o (materiais da classe de engenharia), este passo, no meu entender, \u00e9 mais um processo de gest\u00e3o e manuten\u00e7\u00e3o! Limpeza dos materiais residuais no barril, aqui um material de viscosidade relativamente alta \u00e9 uma boa escolha para a limpeza. <\/p>\n\n\n\n<p>Em primeiro lugar, este tipo de material modificado precisa de estar pr\u00f3ximo do material de produ\u00e7\u00e3o em termos de temperatura, em segundo lugar, tem uma boa viscosidade. Recomendamos a utiliza\u00e7\u00e3o de alguns materiais de lavagem especiais para limpeza, este tipo de material de limpeza especial tem uma viscosidade muito boa. Durante o processo de limpeza, a sua capacidade de troca \u00e9 excelente e este material de limpeza tem uma boa atividade qu\u00edmica (muito boa compatibilidade). Isto pode continuar a rea\u00e7\u00e3o qu\u00edmica com alguns dos \"pontos persistentes\", posi\u00e7\u00f5es sem sa\u00edda dos materiais dentro do barril durante uma paragem. No arranque seguinte, pode remover mais res\u00edduos (reduzir a possibilidade de pontos negros). <\/p>\n\n\n\n<p>Depois de limpar a cor (disparar algumas vezes), finalmente disparar em vazio (tempo de espera m\u00ednimo recomendado de 15 minutos, dando-lhe algum tempo para a compatibilidade da rea\u00e7\u00e3o). Naturalmente, a altera\u00e7\u00e3o da produ\u00e7\u00e3o de material tamb\u00e9m pode melhorar os pontos negros. A capacidade de limpeza da cor deste tipo de material \u00e9 muito mais forte do que a dos materiais comuns, o que pode poupar muito tempo de forma muito eficaz. A sua carater\u00edstica \u00e9 que pode permanecer no barril durante um per\u00edodo de tempo relativamente longo. Ao mesmo tempo, \u00e9 compat\u00edvel com alguns dos materiais sem sa\u00edda no interior, reduzindo a produ\u00e7\u00e3o subsequente de pontos negros.<\/p>\n\n\n\n<figure class=\"wp-block-image aligncenter size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"576\" src=\"https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Maintain-the-barrel-of-the-injection-molding-machine-to-prevent-the-occurrence-of-black-specks-defects-1024x576.webp\" alt=\"Manter o tambor da m\u00e1quina de moldagem por inje\u00e7\u00e3o para evitar a ocorr\u00eancia de defeitos de manchas pretas\" class=\"wp-image-31643\" srcset=\"https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Maintain-the-barrel-of-the-injection-molding-machine-to-prevent-the-occurrence-of-black-specks-defects-1024x576.webp 1024w, https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Maintain-the-barrel-of-the-injection-molding-machine-to-prevent-the-occurrence-of-black-specks-defects-300x169.webp 300w, https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Maintain-the-barrel-of-the-injection-molding-machine-to-prevent-the-occurrence-of-black-specks-defects-768x432.webp 768w, https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Maintain-the-barrel-of-the-injection-molding-machine-to-prevent-the-occurrence-of-black-specks-defects-18x10.webp 18w, https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Maintain-the-barrel-of-the-injection-molding-machine-to-prevent-the-occurrence-of-black-specks-defects-600x338.webp 600w, https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/Maintain-the-barrel-of-the-injection-molding-machine-to-prevent-the-occurrence-of-black-specks-defects.webp 1280w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"h-conclusion\">Conclus\u00e3o<\/h2>\n\n\n\n<p>N\u00e3o \u00e9 dif\u00edcil perceber que os pontos negros t\u00eam uma certa rela\u00e7\u00e3o com o equipamento e o ambiente da f\u00e1brica de moldagem por inje\u00e7\u00e3o. Mais ainda, t\u00eam uma rela\u00e7\u00e3o com a gest\u00e3o da oficina por parte da f\u00e1brica de moldagem por inje\u00e7\u00e3o. A First Mold sempre enfatizou a gest\u00e3o 6s da produ\u00e7\u00e3o da oficina. Esta era \u00e9 a era da moldagem por inje\u00e7\u00e3o cient\u00edfica, bem como a era da moldagem por inje\u00e7\u00e3o inteligente.<\/p>\n\n\n\n<p>Sou James Li, da First Mold, e sou apaixonado por partilhar experi\u00eancias e conhecimentos relacionados com a moldagem por inje\u00e7\u00e3o e o fabrico de moldes. Se tiver alguma quest\u00e3o, n\u00e3o hesite em contactar-me em <a><strong>firstmold88@gmail.com<\/strong><\/a>.<\/p>","protected":false},"excerpt":{"rendered":"<p>Compreender os m\u00e9todos de identifica\u00e7\u00e3o, aceita\u00e7\u00e3o, causas e solu\u00e7\u00f5es para os pontos negros \/ manchas negras na moldagem por inje\u00e7\u00e3o.<\/p>","protected":false},"author":5,"featured_media":31644,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":""},"categories":[48],"tags":[51,63],"class_list":["post-19512","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-tips","tag-injection-molding","tag-injection-molding-defects"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v22.3 (Yoast SEO v27.5) - https:\/\/yoast.com\/product\/yoast-seo-premium-wordpress\/ -->\n<title>Black Spots and Black Specks In Plastic Molded Parts<\/title>\n<meta name=\"description\" content=\"Understand the identification methods, acceptance, causes, and solutions for black spots \/ black specks in injection molding.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/firstmold.com\/pt\/tips\/black-spots-and-black-specks\/\" \/>\n<meta property=\"og:locale\" content=\"pt_PT\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Black Spots and Black Specks in Injection Molding\" \/>\n<meta property=\"og:description\" content=\"Understand the identification methods, acceptance, causes, and solutions for black spots \/ black specks in injection molding.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/firstmold.com\/pt\/tips\/black-spots-and-black-specks\/\" \/>\n<meta property=\"og:site_name\" content=\"First Mold\" \/>\n<meta property=\"article:publisher\" content=\"https:\/\/www.youtube.com\/@firstmold\" \/>\n<meta property=\"article:published_time\" content=\"2024-05-10T06:03:14+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2025-08-11T07:54:54+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/The-Injection-Molding-Research-Laboratory-is-investigating-the-causes-of-black-spot-defects.webp\" \/>\n\t<meta property=\"og:image:width\" content=\"1200\" \/>\n\t<meta property=\"og:image:height\" content=\"675\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/webp\" \/>\n<meta name=\"author\" content=\"James Li\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:title\" content=\"Black Spots and Black Specks in Injection Molding\" \/>\n<meta name=\"twitter:description\" content=\"Understand the identification methods, acceptance, causes, and solutions for black spots \/ black specks in injection molding.\" \/>\n<meta name=\"twitter:image\" content=\"https:\/\/firstmold.com\/wp-content\/uploads\/2024\/05\/The-Injection-Molding-Research-Laboratory-is-investigating-the-causes-of-black-spot-defects.webp\" \/>\n<meta name=\"twitter:creator\" content=\"@firstmold2011\" \/>\n<meta name=\"twitter:site\" content=\"@firstmold2011\" \/>\n<meta name=\"twitter:label1\" content=\"Escrito por\" \/>\n\t<meta name=\"twitter:data1\" content=\"James Li\" \/>\n\t<meta name=\"twitter:label2\" content=\"Tempo estimado de leitura\" \/>\n\t<meta name=\"twitter:data2\" content=\"11 minutos\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\\\/\\\/firstmold.com\\\/tips\\\/black-spots-and-black-specks\\\/#article\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/firstmold.com\\\/tips\\\/black-spots-and-black-specks\\\/\"},\"author\":{\"name\":\"James Li\",\"@id\":\"https:\\\/\\\/firstmold.com\\\/#\\\/schema\\\/person\\\/41882a87bad7ee7a4cab1e8b0b75a0ae\"},\"headline\":\"Black Spots and Black Specks in Injection Molding\",\"datePublished\":\"2024-05-10T06:03:14+00:00\",\"dateModified\":\"2025-08-11T07:54:54+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\\\/\\\/firstmold.com\\\/tips\\\/black-spots-and-black-specks\\\/\"},\"wordCount\":2157,\"commentCount\":0,\"publisher\":{\"@id\":\"https:\\\/\\\/firstmold.com\\\/#organization\"},\"image\":{\"@id\":\"https:\\\/\\\/firstmold.com\\\/tips\\\/black-spots-and-black-specks\\\/#primaryimage\"},\"thumbnailUrl\":\"https:\\\/\\\/firstmold.com\\\/wp-content\\\/uploads\\\/2024\\\/05\\\/The-Injection-Molding-Research-Laboratory-is-investigating-the-causes-of-black-spot-defects.webp\",\"keywords\":[\"Injection Molding\",\"Injection Molding Defects\"],\"articleSection\":[\"Tips &amp; 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