{"id":3371,"date":"2026-08-15T08:50:03","date_gmt":"2026-08-15T08:50:03","guid":{"rendered":"https:\/\/koreben.com\/?p=3371"},"modified":"2026-08-15T08:50:06","modified_gmt":"2026-08-15T08:50:06","slug":"core-cavity-placement-injection-molding","status":"publish","type":"post","link":"https:\/\/koreben.com\/zh\/core-cavity-placement-injection-molding\/","title":{"rendered":"Core and Cavity Placement in Injection Molding: Designing the Mold to Control Part Release"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\">A part can have the right wall thickness, sufficient draft, and a well-designed gate\u2014and still create an ejection problem if the <strong>core and cavity are positioned incorrectly<\/strong>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Core and cavity placement is one of the fundamental decisions in mold design.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">It determines:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Which mold half forms each surface<\/li>\n\n\n\n<li>Where the part will shrink<\/li>\n\n\n\n<li>Which side will retain the part<\/li>\n\n\n\n<li>Where ejector pins can act<\/li>\n\n\n\n<li>How features such as holes, ribs, and tabs should be drafted<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">The basic objective is simple:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>When the mold opens, the molded part should remain on the side where the ejection system can remove it safely.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">This sounds straightforward. In complex parts, however, shrinkage, draft, texture, and feature geometry can make the result much less predictable.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Engineering Problem<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">An injection mold normally has two primary halves:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>A-side \/ cavity side<\/strong><\/li>\n\n\n\n<li><strong>B-side \/ core side<\/strong><\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">The A-side is generally the stationary side of the mold, while the B-side moves with the machine and contains the ejector system.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">During molding, the resin fills the cavity and cools.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">As the plastic shrinks, it may:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Pull away from one mold surface<\/li>\n\n\n\n<li>Grip another surface<\/li>\n\n\n\n<li>Lock around cores or features<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">This creates a critical engineering question:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Which side will the part stay on when the mold opens?<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If the part remains on the B-side, ejector pins can push it away from the core.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If it unexpectedly remains on the A-side, there may be no effective mechanism to remove it.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">That can lead to:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Sticking<\/li>\n\n\n\n<li>Part deformation<\/li>\n\n\n\n<li>Broken features<\/li>\n\n\n\n<li>Difficult automatic production<\/li>\n\n\n\n<li>Additional tooling complexity<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">The original Protolabs guidance emphasizes that the part should remain with the mold half containing the ejector system, and uses a cup-shaped part to illustrate how shrinkage and core placement determine which side retains the part.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Root Cause: Shrinkage Determines Where the Part Wants to Stay<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">The most important concept is <strong>shrinkage<\/strong>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Consider a simple plastic cup.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If the outside of the cup is formed by the cavity and the inside is formed by a core, the plastic will generally shrink toward the core as it cools.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This is useful.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">When the mold opens:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>The exterior releases from the cavity<\/li>\n\n\n\n<li>The part remains around the core<\/li>\n\n\n\n<li>Ejector pins can push the cup off the core<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">The mold is effectively using shrinkage to assist ejection.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Reverse the arrangement, however, and the part may remain on the wrong side of the mold.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This is why core and cavity placement should be considered during part design\u2014not after the mold structure has already been determined.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Engineering Reference Data<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Unlike draft angle or wall thickness, there is no universal &#8220;correct&#8221; numerical value for core\/cavity placement.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The decision is primarily geometric.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">During DFM review, engineers should evaluate:<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Design Factor<\/th><th>Effect on Mold Design<\/th><\/tr><\/thead><tbody><tr><td>Part shrinkage<\/td><td>Determines likely mold-side retention<\/td><\/tr><tr><td>Draft angle<\/td><td>Controls release direction<\/td><\/tr><tr><td>Surface texture<\/td><td>Can increase mold adhesion<\/td><\/tr><tr><td>Deep internal features<\/td><td>Often favor core-side retention<\/td><\/tr><tr><td>Ribs and bosses<\/td><td>May influence ejection force<\/td><\/tr><tr><td>Through-holes<\/td><td>Require careful core orientation<\/td><\/tr><tr><td>Tabs and thin projections<\/td><td>Can deform during mold opening<\/td><\/tr><tr><td>Cosmetic surfaces<\/td><td>May require controlled cavity release<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">The key principle is:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>The mold should be designed so that shrinkage, draft, and ejection work in the same direction.<\/strong><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Core vs. Cavity: The Basic Arrangement<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">For a typical enclosure, the most straightforward arrangement is often:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Exterior surfaces \u2192 cavity \/ A-side<\/li>\n\n\n\n<li>Interior surfaces \u2192 core \/ B-side<\/li>\n\n\n\n<li>Ejection \u2192 B-side<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">This arrangement allows the molded part to shrink onto the core while releasing from the cavity.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">It also provides a practical location for ejector pins.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">However, this is a starting point\u2014not an automatic rule.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Complex geometry can require a different strategy.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img fetchpriority=\"high\" decoding=\"async\" width=\"1024\" height=\"683\" src=\"https:\/\/koreben.com\/wp-content\/uploads\/2026\/08\/Basic-Core-and-Cavity-Arrangement-1024x683.png\" alt=\"\" class=\"wp-image-3379\" srcset=\"https:\/\/koreben.com\/wp-content\/uploads\/2026\/08\/Basic-Core-and-Cavity-Arrangement-1024x683.png 1024w, https:\/\/koreben.com\/wp-content\/uploads\/2026\/08\/Basic-Core-and-Cavity-Arrangement-300x200.png 300w, https:\/\/koreben.com\/wp-content\/uploads\/2026\/08\/Basic-Core-and-Cavity-Arrangement-768x512.png 768w, https:\/\/koreben.com\/wp-content\/uploads\/2026\/08\/Basic-Core-and-Cavity-Arrangement-18x12.png 18w, https:\/\/koreben.com\/wp-content\/uploads\/2026\/08\/Basic-Core-and-Cavity-Arrangement.png 1536w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<h1 class=\"wp-block-heading\">Why the Ejection Side Matters<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">The B-side normally contains:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Ejector pins<\/li>\n\n\n\n<li>Ejector plates<\/li>\n\n\n\n<li>Ejector sleeves<\/li>\n\n\n\n<li>Other ejection mechanisms<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Therefore, the part should ideally remain on this side after mold opening.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This sounds obvious, but part geometry can work against it.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For example, a textured exterior surface may grip the cavity.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A deep internal feature may grip the core.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A poorly oriented hole may cause a small core to retain the part on the wrong side.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The mold engineer therefore needs to balance the retention forces.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Core and Cavity Placement for Enclosures<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Enclosures are one of the most common applications where this decision becomes important.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Consider a rectangular electronic housing with:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Four through-holes<\/li>\n\n\n\n<li>Internal ribs<\/li>\n\n\n\n<li>Mounting bosses<\/li>\n\n\n\n<li>Snap features<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">The basic housing may be easy to mold.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The problem often comes from the secondary features.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A through-hole can be formed by a core pin.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The direction of that core pin matters.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If the core pin is oriented toward the wrong mold half, the part may remain on the cavity side after opening.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A better design often directs the feature so that the core is associated with the ejector side.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>[Engineering Illustration 2: Correct vs. Incorrect Core Placement for a Housing]<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Image requirements:<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Show the same rectangular enclosure in two side-by-side mold designs.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Design A \u2014 Higher Ejection Risk<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Hole core positioned toward the cavity side<\/li>\n\n\n\n<li>Part tends to remain on A-side<\/li>\n\n\n\n<li>No direct ejector support<\/li>\n\n\n\n<li>Highlight the retention problem<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Label:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>&#8220;Core pulls against the ejection strategy&#8221;<\/strong><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Design B \u2014 Preferred Arrangement<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Hole core positioned toward the B-side<\/li>\n\n\n\n<li>Part remains on ejector side<\/li>\n\n\n\n<li>Ejector pins support the molded part<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Label:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>&#8220;Core direction aligned with ejection&#8221;<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Add an arrow showing the mold opening direction.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Draft Direction Is Part of Core and Cavity Design<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Draft is not only about reducing friction.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">It also helps determine <strong>which mold surface releases first<\/strong>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For features that should remain on the B-side, the draft direction should generally encourage release from the A-side and retention around the B-side core.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This becomes particularly important for:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Internal ribs<\/li>\n\n\n\n<li>Tabs<\/li>\n\n\n\n<li>Strips<\/li>\n\n\n\n<li>Bosses<\/li>\n\n\n\n<li>Core pins<\/li>\n\n\n\n<li>Features spanning openings<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Poor draft direction can create a situation where the part wants to remain on the wrong mold half.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Deep Ribs and Internal Features<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Deep internal ribs can create another challenge.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">There are two fundamentally different approaches to forming an internal wall.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Approach A: Deep Pocket Machining<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The mold steel is machined deeply into one side of the mold.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Approach B: Core Formation<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A projecting core forms the interior geometry.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The second approach can often provide a more natural ejection strategy because the molded part shrinks around the core and can then be pushed off by ejector pins.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The correct choice depends on:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Geometry<\/li>\n\n\n\n<li>Depth<\/li>\n\n\n\n<li>Draft<\/li>\n\n\n\n<li>Mold construction<\/li>\n\n\n\n<li>Machining access<\/li>\n\n\n\n<li>Ejection requirements<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>[Engineering Illustration 3: Deep Pocket vs. Core Formation]<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Image requirements:<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Create a side-by-side cross-sectional comparison.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Left: Deep Pocket<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Show a deep cavity machined into mold steel<\/li>\n\n\n\n<li>Highlight difficult machining access<\/li>\n\n\n\n<li>Show potential ejection concerns<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Right: Core Formation<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Show a projecting core forming the internal wall<\/li>\n\n\n\n<li>Show the molded part shrinking around the core<\/li>\n\n\n\n<li>Show ejector pins pushing the part away<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Caption:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>&#8220;The same part geometry can require very different mold strategies.&#8221;<\/strong><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Surface Texture Can Change the Retention Strategy<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Surface finish should also be considered.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A polished surface generally releases more easily than a textured surface.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Texture creates microscopic mechanical engagement between the mold and plastic.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">As a result, a heavily textured exterior surface may remain attached to the cavity longer than expected.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This can interfere with the intended ejection strategy.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For textured parts, engineers should therefore review:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Texture depth<\/li>\n\n\n\n<li>Draft angle<\/li>\n\n\n\n<li>Shrink direction<\/li>\n\n\n\n<li>Ejection force<\/li>\n\n\n\n<li>Cosmetic requirements<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">A surface that looks acceptable in CAD may behave very differently once texture is applied.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Mold Engineering Perspective<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Experienced mold engineers do not simply divide a part into:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>A-side = outside<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>B-side = inside<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">They evaluate the entire retention and ejection system.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The real question is:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>When the mold opens, what forces determine where the part stays?<\/strong><\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">Those forces may include:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Plastic shrinkage<\/li>\n\n\n\n<li>Surface texture<\/li>\n\n\n\n<li>Draft<\/li>\n\n\n\n<li>Core friction<\/li>\n\n\n\n<li>Feature geometry<\/li>\n\n\n\n<li>Ejector force<\/li>\n\n\n\n<li>Part stiffness<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">The objective is to make these forces work together.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A good design creates a predictable sequence:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Mold opens \u2192 part releases from cavity \u2192 part remains on core \u2192 ejectors push part off core<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">That sequence is much easier to automate and repeat.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Common Core and Cavity Design Mistakes<\/h1>\n\n\n\n<h2 class=\"wp-block-heading\">1. Choosing the Parting Line Before Considering Ejection<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">The most visually convenient parting line is not always the best engineering solution.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">2. Ignoring Shrink Direction<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Plastic shrinkage can determine which mold surface retains the part.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">3. Incorrect Core Direction<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Through-holes and internal features can accidentally pull the part toward the wrong mold half.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">4. Ignoring Texture<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Texture can significantly increase surface retention.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">5. Designing Features Without Mold Opening Direction<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Tabs, ribs, bosses, and projections should be evaluated according to the actual mold pull direction.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">DFM Quick Review Checklist: Core and Cavity Placement<\/h1>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Is the intended parting line compatible with ejection?<\/li>\n\n\n\n<li>Will the part remain on the ejector side after mold opening?<\/li>\n\n\n\n<li>Do shrinkage and draft support the intended retention direction?<\/li>\n\n\n\n<li>Are core pins and internal features oriented correctly?<\/li>\n\n\n\n<li>Have texture and cosmetic surfaces been considered?<\/li>\n\n\n\n<li>Can ejector pins support the part without deformation?<\/li>\n\n\n\n<li>Has the mold opening sequence been reviewed in 3D?<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Final Thoughts<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Core and cavity placement is not simply a mold construction decision.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">It is a part-design decision.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A well-designed component should naturally move through the intended molding sequence:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Fill \u2192 Cool \u2192 Shrink \u2192 Release \u2192 Eject<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">When the geometry, draft, shrinkage, core direction, and ejection system all work together, the mold can release the part predictably with minimal force.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">When they work against each other, even a relatively simple component can become difficult to manufacture.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For precision injection molding, the best time to solve a core-and-cavity problem is <strong>before the mold is built<\/strong>.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Learn how core and cavity placement affects part retention, shrinkage, mold opening, and ejection. Practical guidelines for designing injection molded parts for reliable tooling.<\/p>","protected":false},"author":2,"featured_media":3380,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[21,23,14],"tags":[88,22,90,24,89,27,29],"class_list":["post-3371","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-advanced-molding","category-engineering-npd","category-precision-tooling","tag-core-and-cavity","tag-dfm","tag-ejection","tag-injection-molding","tag-parting-line","tag-plastic-part-design","tag-tooling-engineering"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/koreben.com\/zh\/wp-json\/wp\/v2\/posts\/3371","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/koreben.com\/zh\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/koreben.com\/zh\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/koreben.com\/zh\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/koreben.com\/zh\/wp-json\/wp\/v2\/comments?post=3371"}],"version-history":[{"count":3,"href":"https:\/\/koreben.com\/zh\/wp-json\/wp\/v2\/posts\/3371\/revisions"}],"predecessor-version":[{"id":3381,"href":"https:\/\/koreben.com\/zh\/wp-json\/wp\/v2\/posts\/3371\/revisions\/3381"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/koreben.com\/zh\/wp-json\/wp\/v2\/media\/3380"}],"wp:attachment":[{"href":"https:\/\/koreben.com\/zh\/wp-json\/wp\/v2\/media?parent=3371"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/koreben.com\/zh\/wp-json\/wp\/v2\/categories?post=3371"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/koreben.com\/zh\/wp-json\/wp\/v2\/tags?post=3371"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}