{"id":336,"date":"2026-04-26T01:53:45","date_gmt":"2026-04-26T01:53:45","guid":{"rendered":"https:\/\/kurtfoundry.com\/?p=336"},"modified":"2026-04-26T01:53:45","modified_gmt":"2026-04-26T01:53:45","slug":"blank-sand-cast","status":"publish","type":"post","link":"https:\/\/kurtfoundry.com\/fr\/blog\/blank-sand-cast\/","title":{"rendered":"Comment fabriquer une \u00e9bauche moul\u00e9e au sable"},"content":{"rendered":"

Sand casting produces roughly 70% of all metal castings worldwide. The blank you receive from a foundry arrives rough \u2014 gate stubs, parting line flash, and sand texture still attached. Your tolerances, surface finish, and machining stock are all locked in during the production sequence from pattern to shakeout, and each stage gives you specific DFM leverage if you know where to push.<\/p>\n\n\n\n

Pr\u00e9paration du mod\u00e8le et des noyaux<\/h2>\n\n\n\n
\"Mod\u00e8le<\/figure>\n\n\n\n

Every sand casting starts with a pattern \u2014 a physical replica of the finished part, oversized to compensate for metal shrinkage. Shrinkage is not one number you add uniformly. Metal contracts in three distinct phases: liquid contraction as the melt cools to its freezing point, solidification shrinkage as it transforms from liquid to solid (roughly 6% by volume for aluminum), and solid-state contraction as the casting cools to room temperature. Pattern allowance only compensates for that last phase. The first two require proper gating and riser design \u2014 no amount of pattern scaling fixes inadequate feeding.<\/p>\n\n\n\n

Pour les alliages Al-Si, pr\u00e9voyez un retrait lin\u00e9aire de 1,2 \u00e0 1,6\u202f% int\u00e9gr\u00e9 dans le mod\u00e8le. Les angles de d\u00e9pouille \u2014 g\u00e9n\u00e9ralement de 1 \u00e0 3 degr\u00e9s sur les surfaces verticales \u2014 permettent au mod\u00e8le de se retirer proprement du sable sans d\u00e9chirer l'empreinte du moule. Si vous omettez la d\u00e9pouille, votre fonderie soit l'ajoute pour vous (modifiant ainsi vos dimensions), soit lutte contre des bords de moule cass\u00e9s \u00e0 chaque extraction.<\/p>\n\n\n\n

Si votre pi\u00e8ce comporte des passages internes, la fonderie fabrique des noyaux en sable s\u00e9par\u00e9ment et les place dans le moule avant la fermeture. Avant de finaliser votre dessin, v\u00e9rifiez si votre g\u00e9om\u00e9trie interne n\u00e9cessite r\u00e9ellement un noyau ou peut \u00eatre usin\u00e9e \u00e0 partir de mati\u00e8re pleine \u2014 les noyaux ajoutent des co\u00fbts et une incertitude dimensionnelle.<\/p>\n\n\n\n

Moulage et syst\u00e8me d'alimentation<\/h2>\n\n\n\n

The mold is built in two halves: the cope (top) and drag (bottom), packed with sand around the pattern. Where these halves meet creates the parting line \u2014 a feature visible on every blank you receive. Parting line location is not cosmetic. It determines where flash forms, where dimensional variation is highest, and where machining fixtures will reference.<\/p>\n\n\n\n

The gating system \u2014 sprue (vertical entry channel), runners, and gates \u2014 controls how metal fills the cavity. Good gating design prevents 70% of casting defects. Too fast, and turbulent flow traps air and erodes sand into the casting. Too slow, and metal freezes before filling thin sections. Risers \u2014 reservoirs of extra metal at thick sections \u2014 feed shrinkage as the casting solidifies. Every gate and riser leaves a stub on the blank that must be cut after shakeout.<\/p>\n\n\n\n

\"Sch\u00e9ma<\/figure>\n\n\n\n

J'ai vu plus d'\u00e9bauches rejet\u00e9es \u00e0 cause d'un mauvais syst\u00e8me de coul\u00e9e que d'un mauvais choix d'alliage. Si votre fonderie demande de d\u00e9placer un emplacement d'attaque de coul\u00e9e, \u00e9coutez \u2014 ils prot\u00e8gent la qualit\u00e9 de votre pi\u00e8ce.<\/p>\n\n\n\n

Coul\u00e9e et refroidissement<\/h2>\n\n\n\n
\"M\u00e9tal<\/figure>\n\n\n\n

La fonte grise est coul\u00e9e en dessous de 1300 \u00b0C. Les alliages d'aluminium sont coul\u00e9s \u00e0 des temp\u00e9ratures consid\u00e9rablement plus basses. La temp\u00e9rature exacte est importante car un m\u00e9tal coul\u00e9 trop chaud absorbe l'hydrog\u00e8ne de l'humidit\u00e9 pr\u00e9sente dans le sable, cr\u00e9ant une porosit\u00e9 gazeuse \u2014 de petites cavit\u00e9s rondes juste sous la surface qui n'apparaissent qu'apr\u00e8s l'usinage.<\/p>\n\n\n\n

Once the mold is full, cooling rate determines both microstructure and dimensional stability. Controlled cooling inside the sand mold is the professional standard. Some hobby guides recommend quenching freshly cast parts in water to speed handling. For ferrous castings, this causes thermal shock cracks and locked-in residual stress. Even for aluminum, rapid quenching distorts thin sections and generates internal tension that fights your machining later.<\/p>\n\n\n\n

Les temps de cycle pour les pi\u00e8ces petites \u00e0 moyennes vont de 5 \u00e0 30 minutes de la coul\u00e9e au d\u00e9cochage. Les pi\u00e8ces moul\u00e9es de grande taille ou \u00e0 sections \u00e9paisses peuvent prendre des heures.<\/p>\n\n\n\n

D\u00e9cochage et nettoyage<\/h2>\n\n\n\n
\"\u00c9bauche<\/figure>\n\n\n\n

Le d\u00e9cochage est exactement ce \u00e0 quoi cela ressemble \u2014 le moule en sable est bris\u00e9 pour lib\u00e9rer la pi\u00e8ce coul\u00e9e. Ce qui en sort n'est pas une pi\u00e8ce finie. L'\u00e9bauche porte des amorces de canal, des plots de masselotte, des bavures de plan de joint (fines ailettes m\u00e9talliques l\u00e0 o\u00f9 les ch\u00e2ssis sup\u00e9rieur et inf\u00e9rieur ne se sont pas parfaitement scell\u00e9s), et une surface brute de coul\u00e9e avec une texture de sable incrust\u00e9e.<\/p>\n\n\n\n

Les amorces de canal et les masselottes sont coup\u00e9es \u00e0 l'aide de scies ou de meuleuses. Les bavures sont \u00e9barb\u00e9es ou meul\u00e9es. La surface restante est grenaill\u00e9e. L'\u00e9tat de surface des faces brutes de coul\u00e9e est g\u00e9n\u00e9ralement de 250 \u00e0 500 micropouces Ra \u2014 bien plus rugueux que toute surface usin\u00e9e.<\/p>\n\n\n\n

Most defects trace back to three root causes: moisture in the sand (gas porosity), inadequate riser feeding (shrinkage cavities with jagged internal surfaces), or temperature problems during pour (cold shuts where two metal fronts meet without fusing, or hot tears from uneven cooling). When you receive a blank with defects, work backwards from the riser \u2014 the answer is usually there.<\/p>\n\n\n\n

Erreurs courantes dans les sp\u00e9cifications qui augmentent les co\u00fbts<\/h2>\n\n\n\n

The most common mistake I see from design engineers is specifying tolerances tighter than the process can deliver. Standard sand casting achieves CT8-12 tolerance class per ISO 8062, with CT9 typical. Anything tighter than CT8 on an as-cast feature means you are paying for machining whether you intended to or not. Specify as-cast tolerances where the function allows, and call out machined surfaces explicitly \u2014 2 mm is a common machining allowance on medium-diameter features.<\/p>\n\n\n\n

Deuxi\u00e8mement : ignorer les transitions d'\u00e9paisseur de section. Visez des transitions de paroi progressives avec un rapport d'\u00e9paisseur inf\u00e9rieur \u00e0 1:4. Un bossage \u00e9pais adjacent \u00e0 une paroi mince refroidit \u00e0 des vitesses diff\u00e9rentes, attirant la porosit\u00e9 de retrait dans la jonction.<\/p>\n\n\n\n

\"Sch\u00e9ma<\/figure>\n\n\n\n

Troisi\u00e8mement : placer des caract\u00e9ristiques critiques \u00e0 travers le plan de joint. La variation dimensionnelle est toujours la pire au niveau du plan de joint en raison de la tol\u00e9rance d'alignement entre les ch\u00e2ssis sup\u00e9rieur et inf\u00e9rieur. D\u00e9placez les r\u00e9f\u00e9rences critiques vers une seule moiti\u00e9 du moule chaque fois que possible.<\/p>\n\n\n\n

Votre liste de contr\u00f4le DFM avant de commander une \u00e9bauche<\/h2>\n\n\n\n

Specify as-cast tolerances at CT9 or wider on non-machined surfaces, and add explicit machining stock on features that need precision. Check that all vertical surfaces have at least 1 degree of draft. Keep section thickness ratios below 1:4, and use generous fillets at every wall junction. Confirm that your critical dimensions sit on one side of the parting line, not across it.<\/p>\n\n\n\n

Une \u00e9tape que la plupart des ing\u00e9nieurs n\u00e9gligent : parler \u00e0 la fonderie avant de publier le dessin. Une conversation de 15 minutes sur l'emplacement du plan de joint et l'acc\u00e8s au syst\u00e8me de coul\u00e9e permet d'\u00e9conomiser des semaines d'it\u00e9rations d'\u00e9chantillons et des milliers d'euros en r\u00e9visions de mod\u00e8le.<\/p>","protected":false},"excerpt":{"rendered":"

Sand casting produces roughly 70% of all metal castings worldwide. The blank you receive from a foundry arrives rough \u2014 […]<\/p>\n","protected":false},"author":3,"featured_media":331,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"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":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","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":[1],"tags":[],"class_list":["post-336","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-blog"],"_links":{"self":[{"href":"https:\/\/kurtfoundry.com\/fr\/wp-json\/wp\/v2\/posts\/336","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/kurtfoundry.com\/fr\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/kurtfoundry.com\/fr\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/kurtfoundry.com\/fr\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/kurtfoundry.com\/fr\/wp-json\/wp\/v2\/comments?post=336"}],"version-history":[{"count":1,"href":"https:\/\/kurtfoundry.com\/fr\/wp-json\/wp\/v2\/posts\/336\/revisions"}],"predecessor-version":[{"id":741,"href":"https:\/\/kurtfoundry.com\/fr\/wp-json\/wp\/v2\/posts\/336\/revisions\/741"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/kurtfoundry.com\/fr\/wp-json\/wp\/v2\/media\/331"}],"wp:attachment":[{"href":"https:\/\/kurtfoundry.com\/fr\/wp-json\/wp\/v2\/media?parent=336"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/kurtfoundry.com\/fr\/wp-json\/wp\/v2\/categories?post=336"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/kurtfoundry.com\/fr\/wp-json\/wp\/v2\/tags?post=336"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}