{"id":25675,"date":"2026-07-20T11:17:32","date_gmt":"2026-07-20T09:17:32","guid":{"rendered":"https:\/\/www.acrn.fr\/?p=25675"},"modified":"2026-07-20T12:14:07","modified_gmt":"2026-07-20T10:14:07","slug":"child-resistant-caps-torque-angle-test","status":"publish","type":"post","link":"https:\/\/www.acrn.fr\/en\/child-resistant-caps-torque-angle-test\/","title":{"rendered":"Child-Resistant Caps: Why the Test Requires Measuring Both Torque and Angle"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\">A child-resistant cap rests on a mechanical paradox: it must resist a child under 52 months while remaining easy to open for a senior adult. This trade-off plays out in a two-step mechanism whose compliance cannot be verified with a simple torque measurement. Two quantities must be measured simultaneously: torque and rotation angle.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This article reviews the applicable standards (ISO 8317, ISO 13127, ASTM D3475), what they actually cover, and the in-production controls needed to guarantee the safety function stays intact batch after batch.<\/p>\n\n\n\n<div class=\"wp-block-rank-math-toc-block\" id=\"rank-math-toc\"><h2>Table of Contents<\/h2><nav><ol><li class=\"\"><a href=\"#what-is-a-child-resistant-cap\">What Is a Child-Resistant Cap?<\/a><\/li><li class=\"\"><a href=\"#iso-8317-iso-13127-astm-d-3475-who-covers-what\">ISO 8317, ISO 13127, ASTM D3475: Who Covers What?<\/a><\/li><li class=\"\"><a href=\"#why-torque-alone-isnt-enough-on-a-two-step-mechanism\">Why Torque Alone Isn&#8217;t Enough on a Two-Step Mechanism<\/a><\/li><li class=\"\"><a href=\"#the-angle-torque-mode-of-the-repea-tork-and-skill-tork\">The Angle + Torque Mode of the RepeaTork and SkillTork+<\/a><\/li><li class=\"\"><a href=\"#what-controls-should-be-implemented-in-production\">What Controls Should Be Implemented in Production?<\/a><\/li><li class=\"\"><a href=\"#acrn-a-french-manufacturer-of-torque-measurement-instruments\">ACRN, a French Manufacturer of Torque Measurement Instruments<\/a><\/li><\/ol><\/nav><\/div>\n\n\n\n<h2 id=\"what-is-a-child-resistant-cap\" class=\"wp-block-heading\">What Is a Child-Resistant Cap?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">A child-resistant cap (or CR closure) requires a combination of movements a young child cannot coordinate: push then turn (push-and-turn), squeeze the sides then turn (squeeze-and-turn), or align a mark before lifting. The ASTM D3475 classification lists these families by the movements, skills, and tools needed to open them.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">These closures are mandatory for many products: medicines, household chemicals labeled as hazardous (CLP regulation in Europe), and nicotine-containing e-liquids. The pharmaceutical sector is the leading user, on syrup bottles and pill containers.<\/p>\n\n\n\n<figure style=\"margin:2.5em 0;\">\n<svg viewbox=\"0 0 800 470\" role=\"img\" aria-label=\"Cutaway diagram of a push-and-turn child-resistant cap: freely rotating outer shell, engagement ratchets, inner cap threaded onto the bottle neck. Two movements: push then turn.\" style=\"width:100%;height:auto;display:block;background:#ffffff;font-family:inherit;\">\n<title>Push-and-turn child-resistant cap: principle of the two-step mechanism<\/title>\n<defs>\n<marker id=\"arr\" markerwidth=\"10\" markerheight=\"10\" refx=\"8\" refy=\"5\" orient=\"auto\"><path d=\"M0,0 L10,5 L0,10 Z\" fill=\"#295C7B\"><\/path><\/marker>\n<\/defs>\n<line x1=\"400\" y1=\"88\" x2=\"400\" y2=\"148\" stroke=\"#295C7B\" stroke-width=\"4\" marker-end=\"url(#arr)\"><\/line>\n<text x=\"418\" y=\"112\" fill=\"#333333\" font-size=\"16\" font-weight=\"600\">1. Push<\/text>\n<path d=\"M 300 175 A 115 38 0 0 1 500 175\" fill=\"none\" stroke=\"#295C7B\" stroke-width=\"4\" marker-end=\"url(#arr)\"><\/path>\n<text x=\"518\" y=\"172\" fill=\"#333333\" font-size=\"16\" font-weight=\"600\">2. Turn<\/text>\n<text x=\"518\" y=\"192\" fill=\"#666666\" font-size=\"13\">while maintaining pressure<\/text>\n<rect x=\"295\" y=\"200\" width=\"210\" height=\"120\" rx=\"8\" fill=\"rgba(41,92,123,0.10)\" stroke=\"#295C7B\" stroke-width=\"2.5\"><\/rect>\n<g stroke=\"#295C7B\" stroke-width=\"1.2\" opacity=\"0.55\">\n<line x1=\"313\" y1=\"206\" x2=\"313\" y2=\"314\"><\/line><line x1=\"331\" y1=\"206\" x2=\"331\" y2=\"314\"><\/line><line x1=\"349\" y1=\"206\" x2=\"349\" y2=\"314\"><\/line><line x1=\"367\" y1=\"206\" x2=\"367\" y2=\"314\"><\/line><line x1=\"433\" y1=\"206\" x2=\"433\" y2=\"314\"><\/line><line x1=\"451\" y1=\"206\" x2=\"451\" y2=\"314\"><\/line><line x1=\"469\" y1=\"206\" x2=\"469\" y2=\"314\"><\/line><line x1=\"487\" y1=\"206\" x2=\"487\" y2=\"314\"><\/line>\n<\/g>\n<path d=\"M 318 262 l 12 -12 l 0 12 l 12 -12 l 0 12 l 12 -12 l 0 12 l 12 -12 l 0 12 l 12 -12 l 0 12 l 12 -12 l 0 12 l 12 -12 l 0 12 l 12 -12 l 0 12 l 12 -12 l 0 12 l 12 -12 l 0 12 l 12 -12 l 0 12 l 12 -12 l 0 12 l 12 -12 l 0 12\" fill=\"none\" stroke=\"#295C7B\" stroke-width=\"2\"><\/path>\n<rect x=\"318\" y=\"268\" width=\"164\" height=\"46\" rx=\"5\" fill=\"#eceff1\" stroke=\"#6b7280\" stroke-width=\"1.5\"><\/rect>\n<rect x=\"330\" y=\"314\" width=\"140\" height=\"118\" fill=\"#ffffff\" stroke=\"#9ca3af\" stroke-width=\"1.5\"><\/rect>\n<g stroke=\"#9ca3af\" stroke-width=\"1.5\">\n<line x1=\"333\" y1=\"330\" x2=\"467\" y2=\"340\"><\/line><line x1=\"333\" y1=\"352\" x2=\"467\" y2=\"362\"><\/line><line x1=\"333\" y1=\"374\" x2=\"467\" y2=\"384\"><\/line><line x1=\"333\" y1=\"396\" x2=\"467\" y2=\"406\"><\/line>\n<\/g>\n<line x1=\"295\" y1=\"240\" x2=\"180\" y2=\"240\" stroke=\"#9ca3af\" stroke-width=\"1\"><\/line>\n<text x=\"172\" y=\"236\" text-anchor=\"end\" fill=\"#333333\" font-size=\"14\" font-weight=\"600\">Outer shell<\/text>\n<text x=\"172\" y=\"254\" text-anchor=\"end\" fill=\"#666666\" font-size=\"12.5\">free rotation without push<\/text>\n<line x1=\"482\" y1=\"256\" x2=\"640\" y2=\"242\" stroke=\"#9ca3af\" stroke-width=\"1\"><\/line>\n<text x=\"646\" y=\"240\" fill=\"#333333\" font-size=\"14\" font-weight=\"600\">Engagement ratchets<\/text>\n<text x=\"646\" y=\"258\" fill=\"#666666\" font-size=\"12.5\">transmitted only<\/text>\n<text x=\"646\" y=\"274\" fill=\"#666666\" font-size=\"12.5\">under axial push<\/text>\n<line x1=\"482\" y1=\"291\" x2=\"640\" y2=\"316\" stroke=\"#9ca3af\" stroke-width=\"1\"><\/line>\n<text x=\"646\" y=\"314\" fill=\"#333333\" font-size=\"14\" font-weight=\"600\">Inner cap<\/text>\n<text x=\"646\" y=\"332\" fill=\"#666666\" font-size=\"12.5\">threaded onto the neck<\/text>\n<line x1=\"330\" y1=\"390\" x2=\"150\" y2=\"390\" stroke=\"#9ca3af\" stroke-width=\"1\"><\/line>\n<text x=\"142\" y=\"386\" text-anchor=\"end\" fill=\"#333333\" font-size=\"14\" font-weight=\"600\">Bottle neck<\/text>\n<text x=\"142\" y=\"404\" text-anchor=\"end\" fill=\"#666666\" font-size=\"12.5\">standard thread<\/text>\n<\/svg>\n<figcaption style=\"font-size:0.85em;color:#666;text-align:center;margin-top:0.75em;\">Push-and-turn principle: without axial push, the outer shell rotates freely over the ratchets; pressure engages the ratchets and transmits rotation to the inner cap. Schematic representation.<\/figcaption>\n<\/figure>\n\n\n\n<h2 id=\"iso-8317-iso-13127-astm-d-3475-who-covers-what\" class=\"wp-block-heading\">ISO 8317, ISO 13127, ASTM D3475: Who Covers What?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Three standards structure the compliance file for a reclosable child-resistant package, and they are not interchangeable:<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table><thead><tr><th>Standard<\/th><th>Nature<\/th><th>Role<\/th><\/tr><\/thead><tbody><tr><td>ISO 8317<\/td><td>Panel testing (children aged 42 to 51 months, adults aged 50 to 70)<\/td><td>Initial certification of the reclosable package<\/td><\/tr><tr><td>16 CFR 1700.20<\/td><td>US panel protocol (CPSC)<\/td><td>Certification for the US market<\/td><\/tr><tr><td>ISO 13127<\/td><td>Instrumented mechanical tests (around ten methods in the annexes: release torque, push-and-turn test, pinch test&#8230;)<\/td><td>Verify that a minor change to an already-certified package has not degraded the function, without repeating a full panel<\/td><\/tr><tr><td>ASTM D3475<\/td><td>Classification of CR package types<\/td><td>Describe and categorize the opening mechanism<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">A point many manufacturers discover too late: <a href=\"https:\/\/www.iso.org\/standard\/53019.html\" target=\"_blank\" rel=\"noopener\">ISO 13127<\/a> itself states it is not intended for routine quality control. It serves as a cost-effective bridge between two panels. Routine control, the kind that guarantees this week&#8217;s production opens the same way as the certified batch, is left for the manufacturer to build. This is exactly where torque + angle measurement comes in.<\/p>\n\n\n\n<h2 id=\"why-torque-alone-isnt-enough-on-a-two-step-mechanism\" class=\"wp-block-heading\">Why Torque Alone Isn&#8217;t Enough on a Two-Step Mechanism<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">On a standard screw cap, a single torque value summarizes the test. On a push-and-turn cap, the same value can hide two opposite behaviors, because the mechanism produces a two-phase torque-angle signature:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Rotation without push<\/strong>: the ratchets must slip without transmitting torque to the thread. If significant torque appears during this phase, the safety function is compromised: a child can open the cap by simply turning it.<\/li>\n\n\n\n<li><strong>Rotation with axial push<\/strong>: the ratchets engage at a precise angle, then unscrewing begins. Engagement that is too late or an opening torque that is too high makes the bottle unusable for a senior adult; erratic engagement signals worn ratchets or a molding defect.<\/li>\n<\/ul>\n\n\n\n<figure style=\"margin:2.5em 0;\">\n<svg viewbox=\"0 0 860 540\" role=\"img\" aria-label=\"Torque-angle curve of a child-resistant cap: without push, torque stays close to zero; with push, the ratchets engage at a defined angle and torque then rises to the opening peak.\" style=\"width:100%;height:auto;display:block;background:#ffffff;font-family:inherit;\">\n<title>Torque-angle signature of a child-resistant cap<\/title>\n<line x1=\"300\" y1=\"70\" x2=\"300\" y2=\"430\" stroke=\"#b6c2cb\" stroke-dasharray=\"4 4\"><\/line>\n<path d=\"M 60 420 l 26 -9 l 4 9 l 26 -9 l 4 9 l 26 -9 l 4 9 l 26 -9 l 4 9 l 26 -9 l 4 9 l 26 -9 l 4 9 l 26 -9 l 4 9 l 26 -9 l 4 9 l 26 -9 l 4 9 l 26 -9 l 4 9 l 26 -9 l 4 9 l 26 -9 l 4 9 l 26 -9 l 4 9 l 26 -9 l 4 9 l 26 -9 l 4 9 l 26 -9 l 4 9 l 26 -9 l 4 9 l 26 -9 l 4 9 l 26 -9 l 4 9 l 26 -9 l 4 9 l 26 -9 l 4 9 l 26 -9 l 4 9 l 20 -6\" fill=\"none\" stroke=\"#9ca3af\" stroke-width=\"2\" stroke-linecap=\"round\"><\/path>\n<path d=\"M 60 426 C 130 422, 220 420, 296 416 C 320 412, 360 360, 420 280 C 470 215, 520 158, 555 148 Q 568 145, 578 152 C 620 190, 700 300, 830 392\" fill=\"none\" stroke=\"#295C7B\" stroke-width=\"2.5\" stroke-linecap=\"round\"><\/path>\n<circle cx=\"560\" cy=\"147\" r=\"5\" fill=\"#295C7B\" stroke=\"#ffffff\" stroke-width=\"2\"><\/circle>\n<line x1=\"60\" y1=\"66\" x2=\"60\" y2=\"430\" stroke=\"#9ca3af\" stroke-width=\"1.5\"><\/line>\n<polygon points=\"60,56 55,68 65,68\" fill=\"#9ca3af\"><\/polygon>\n<line x1=\"60\" y1=\"430\" x2=\"826\" y2=\"430\" stroke=\"#9ca3af\" stroke-width=\"1.5\"><\/line>\n<polygon points=\"836,430 824,425 824,435\" fill=\"#9ca3af\"><\/polygon>\n<text x=\"-245\" y=\"26\" transform=\"rotate(-90)\" text-anchor=\"middle\" fill=\"#666666\" font-size=\"14\">Torque (N\u00b7m)<\/text>\n<text x=\"445\" y=\"464\" text-anchor=\"middle\" fill=\"#666666\" font-size=\"14\">Rotation angle<\/text>\n<text x=\"50\" y=\"444\" fill=\"#999999\" font-size=\"12\">0<\/text>\n<text x=\"308\" y=\"90\" fill=\"#333333\" font-size=\"14\" font-weight=\"600\">Ratchet engagement angle<\/text>\n<text x=\"308\" y=\"108\" fill=\"#666666\" font-size=\"12.5\">must occur within a defined window<\/text>\n<text x=\"578\" y=\"132\" fill=\"#333333\" font-size=\"14\" font-weight=\"600\">Opening torque (peak)<\/text>\n<text x=\"578\" y=\"150\" fill=\"#666666\" font-size=\"12.5\">compared against its tolerance<\/text>\n<g font-size=\"13.5\">\n<line x1=\"70\" y1=\"500\" x2=\"102\" y2=\"500\" stroke=\"#295C7B\" stroke-width=\"3\"><\/line>\n<text x=\"110\" y=\"505\" fill=\"#333333\">With axial push (normal opening)<\/text>\n<line x1=\"430\" y1=\"500\" x2=\"462\" y2=\"500\" stroke=\"#9ca3af\" stroke-width=\"3\"><\/line>\n<text x=\"470\" y=\"505\" fill=\"#333333\">Without push: the ratchets slip, torque near zero<\/text>\n<\/g>\n<\/svg>\n<figcaption style=\"font-size:0.85em;color:#666;text-align:center;margin-top:0.75em;\">Torque-angle signature of a two-step mechanism: without push, the shell slips over the ratchets; with push, engagement occurs at a defined angle and torque then rises to the opening peak. Schematic representation.<\/figcaption>\n<\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">The torque value therefore only makes sense when paired with the angle at which it occurs. It is the angle that pinpoints the mechanical event: ratchet engagement, ratchet jump, start of unscrewing. Two caps can display the same peak torque, one compliant, the other with a degraded mechanism.<\/p>\n\n\n\n<h2 id=\"the-angle-torque-mode-of-the-repea-tork-and-skill-tork\" class=\"wp-block-heading\">The Angle + Torque Mode of the RepeaTork and SkillTork+<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">ACRN&#8217;s instruments dedicated to <a href=\"https:\/\/www.acrn.fr\/en\/torque-measurement\/\">torque measurement<\/a> offer a test mode that simultaneously records torque and cumulative rotation angle. The <a href=\"https:\/\/www.acrn.fr\/en\/product\/torque-tester-skilltork\/\">SkillTork+<\/a> captures the full curve in instrumented manual mode; the <a href=\"https:\/\/www.acrn.fr\/en\/motorized-torque\/\">RepeaTork motorized torque tester<\/a> adds constant rotation speed and controlled push, two conditions essential for repeatability on a two-step mechanism.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Each test produces a Pass\/Fail result on both quantities: torque must fall within its tolerance window, and the event must occur within the expected angle range. Results are exported with batch statistics to feed control charts.<\/p>\n\n\n\n<h2 id=\"what-controls-should-be-implemented-in-production\" class=\"wp-block-heading\">What Controls Should Be Implemented in Production?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Three control points cover the lifecycle of a child-resistant cap in production:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>On receipt of cap batches<\/strong>: sample by mold cavity, since a ratchet defect is almost always localized to one specific cavity.<\/li>\n\n\n\n<li><strong>At the capper outlet<\/strong>: application torque affects opening behavior. The applicable ranges are detailed in our <a href=\"https:\/\/www.acrn.fr\/en\/tightening-torque-for-caps-how-to-measure-and-control-it-during-production\/\">cap tightening torque guide<\/a>.<\/li>\n\n\n\n<li><strong>After any change<\/strong>: material, mold, supplier, capper torque. If the change affects the packaging itself, the ISO 13127 mechanical tests can document equivalence before deciding whether a new panel is required.<\/li>\n<\/ul>\n\n\n\n<h2 id=\"acrn-a-french-manufacturer-of-torque-measurement-instruments\" class=\"wp-block-heading\">ACRN, a French Manufacturer of Torque Measurement Instruments<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">ACRN has designed and manufactured its torque testers in Normandy since 1997, with mandrels custom-made for your child-resistant caps (diameter, grip geometry, axial push). Every instrument ships with a calibration certificate traceable to national standards.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">To define a torque + angle control plan suited to your CR closures, <a href=\"https:\/\/www.acrn.fr\/en\/contact-us\/\">contact our engineers<\/a> with the mechanism type, your torque ranges, and your production rate: we will recommend the right instrument, mandrel, and Pass\/Fail criteria.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>A child-resistant cap rests on a mechanical paradox: it must resist a child under 52 months while remaining easy to open for a senior adult. This trade-off plays out in a two-step mechanism whose compliance cannot be verified with a simple torque measurement. Two quantities must be measured simultaneously: torque and rotation angle. This article [&hellip;]<\/p>\n","protected":false},"author":3,"featured_media":25691,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_et_pb_use_builder":"","_et_pb_old_content":"","_et_gb_content_width":"","footnotes":""},"categories":[332],"tags":[],"dipi_cpt_category":[],"class_list":["post-25675","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-our-news"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.acrn.fr\/en\/wp-json\/wp\/v2\/posts\/25675","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.acrn.fr\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.acrn.fr\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.acrn.fr\/en\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/www.acrn.fr\/en\/wp-json\/wp\/v2\/comments?post=25675"}],"version-history":[{"count":12,"href":"https:\/\/www.acrn.fr\/en\/wp-json\/wp\/v2\/posts\/25675\/revisions"}],"predecessor-version":[{"id":25700,"href":"https:\/\/www.acrn.fr\/en\/wp-json\/wp\/v2\/posts\/25675\/revisions\/25700"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.acrn.fr\/en\/wp-json\/wp\/v2\/media\/25691"}],"wp:attachment":[{"href":"https:\/\/www.acrn.fr\/en\/wp-json\/wp\/v2\/media?parent=25675"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.acrn.fr\/en\/wp-json\/wp\/v2\/categories?post=25675"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.acrn.fr\/en\/wp-json\/wp\/v2\/tags?post=25675"},{"taxonomy":"dipi_cpt_category","embeddable":true,"href":"https:\/\/www.acrn.fr\/en\/wp-json\/wp\/v2\/dipi_cpt_category?post=25675"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}