{"id":3255,"date":"2026-06-10T09:57:09","date_gmt":"2026-06-10T09:57:09","guid":{"rendered":"https:\/\/www.shengweimachine.com\/bag-seal-types-comparison\/"},"modified":"2026-06-10T10:27:37","modified_gmt":"2026-06-10T10:27:37","slug":"bag-seal-types-comparison","status":"publish","type":"page","link":"https:\/\/www.shengweimachine.com\/zh\/bag-seal-types-comparison\/","title":{"rendered":"\u888b\u53e3\u5bc6\u5c01\u65b9\u6cd5\u6bd4\u8f83\uff1a\u70ed\u5c01\u3001\u8109\u51b2\u3001\u5e26\u5f0f\u53ca\u8d85\u58f0\u6ce2\u5bc6\u5c01"},"content":{"rendered":"\t\t<div data-elementor-type=\"wp-page\" data-elementor-id=\"3255\" class=\"elementor elementor-3255 elementor-bc-flex-widget\" data-elementor-post-type=\"page\">\n\t\t\t\t<div class=\"elementor-element elementor-element-fd7ecff e-con-full e-flex e-con e-parent\" data-id=\"fd7ecff\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t<div class=\"elementor-element elementor-element-ca0e51d elementor-widget elementor-widget-html\" data-id=\"ca0e51d\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"html.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<div class=\"sw-page\">\n\n<section class=\"sw-hero-kb\">\n    <div class=\"sw-shell\">\n      <div class=\"sw-hero-kb-grid\">\n\n        <div class=\"sw-hero-kb-copy\">\n\n          <nav class=\"sw-breadcrumb\" aria-label=\"Breadcrumb\">\n            <a href=\"\/\">Home<\/a><span class=\"sw-breadcrumb-sep\">\u203a<\/span>\n            <a href=\"\/buying-guides\/\">Buying Guides<\/a><span class=\"sw-breadcrumb-sep\">\u203a<\/span>\n            <span>Bag Sealing Methods Compared<\/span>\n          <\/nav>\n\n          <div class=\"sw-article-meta\">\n            <span class=\"sw-meta-author\">By <strong>Hellena Ji<\/strong>, International Sales Manager at <a href=\"\/about-us\/\">ShengWei Machine<\/a><\/span>\n            <span class=\"sw-meta-sep\">\u00b7<\/span>\n            <span class=\"sw-meta-date\">Published June 2026<\/span>\n            <span class=\"sw-meta-sep\">\u00b7<\/span>\n            <span class=\"sw-meta-readtime\">12-minute read<\/span>\n          <\/div>\n\n          <h1 class=\"sw-hero-kb-title\">\n            Bag Sealing Methods Compared: Heat Seal, Impulse, Band &amp; Ultrasonic:\n            <span class=\"sw-hero-kb-subtitle\">The Seal Integrity, TPT Window &amp; Failure-Mode Guide<\/span>\n          <\/h1>\n\n          <aside class=\"sw-tldr\">\n            <div class=\"sw-tldr-label\">The Short Answer<\/div>\n            <p>Four methods seal a bag, and they differ in how heat reaches the film. <strong>Constant-heat hot bars<\/strong> are the simple, low-cost workhorse. <strong>Impulse and band sealers<\/strong> cool the film under pressure, which can support cleaner seals on demanding structures. <strong>Ultrasonic<\/strong> makes heat inside the film by vibration with a cold tool, which can help with some in-seal contamination and recyclable mono-materials. Above all: seal <em>strength<\/em> and seal <em>leak-tightness<\/em> are different things \u2014 test both.<\/p>\n            <a href=\"javascript:void(0)\" class=\"sw-tldr-cta\" onclick=\"elementorProFrontend.modules.popup.showPopup({id:840})\" data-elementor-open-popup=\"840\">Skip the analysis \u2014 send your film and product spec \u2192<\/a>\n          <\/aside>\n\n        <\/div>\n\n        <figure class=\"sw-hero-kb-visual sw-figure-zoom\">\n          <img decoding=\"async\" src=\"https:\/\/www.shengweimachine.com\/wp-content\/uploads\/2024\/09\/Automatic-Six-Column-Three-Side-Sealing-Vertical-Packaging-Machine-653x1024.webp\"\n               alt=\"ShengWei six-column vertical packaging machine forming three-side-seal sachets across multiple lanes\"\n               loading=\"eager\" fetchpriority=\"high\"\n               width=\"653\" height=\"1024\">\n          <button type=\"button\" class=\"sw-figure-zoom-badge\" aria-label=\"View larger image\" tabindex=\"-1\">\n            <svg viewBox=\"0 0 20 20\" aria-hidden=\"true\"><path d=\"M9 1a8 8 0 105.293 14.293l4.207 4.207 1.414-1.414-4.207-4.207A8 8 0 009 1zm0 2a6 6 0 110 12 6 6 0 010-12zm-1 3v2H6v2h2v2h2v-2h2V8h-2V6H8z\"\/><\/svg>\n          <\/button>\n        <\/figure>\n\n      <\/div>\n    <\/div>\n  <\/section>\n\n<div class=\"sw-trust-strip-wrap\">\n    <div class=\"sw-shell\">\n      <div class=\"sw-trust-strip\">\n        <div class=\"sw-trust-item\">\n          <p class=\"sw-trust-label\">Authored by<\/p>\n          <p class=\"sw-trust-value\">Hellena Ji, International Sales Manager<\/p>\n        <\/div>\n        <div class=\"sw-trust-item\">\n          <p class=\"sw-trust-label\">Lead Time<\/p>\n          <p class=\"sw-trust-value\">15\u201320 days ex-works<\/p>\n        <\/div>\n        <div class=\"sw-trust-item\">\n          <p class=\"sw-trust-label\">Markets<\/p>\n          <p class=\"sw-trust-value\">80+ countries served<\/p>\n        <\/div>\n        <div class=\"sw-trust-item\">\n          <p class=\"sw-trust-label\">Sealing<\/p>\n          <p class=\"sw-trust-value\">Tuned to your film stack, not a fixed setpoint<\/p>\n        <\/div>\n      <\/div>\n    <\/div>\n  <\/div>\n\n<nav class=\"sw-guide-nav\" aria-label=\"In this guide\">\n    <div class=\"sw-shell\">\n      <div class=\"sw-guide-nav-inner\">\n        <span class=\"sw-guide-nav-label\">In this guide<\/span>\n        <div class=\"sw-guide-nav-scroll\">\n          <ol class=\"sw-guide-nav-list\">\n            <li><a class=\"sw-guide-nav-link\" href=\"#thesis\">A Process Window, Not a Bag Shape<\/a><\/li>\n            <li><a class=\"sw-guide-nav-link\" href=\"#methods\">How the Four Methods Seal<\/a><\/li>\n            <li><a class=\"sw-guide-nav-link\" href=\"#matrix\">Decision Matrix<\/a><\/li>\n            <li><a class=\"sw-guide-nav-link\" href=\"#window\">The Sealing Window<\/a><\/li>\n            <li><a class=\"sw-guide-nav-link\" href=\"#integrity\">Strength vs Integrity<\/a><\/li>\n            <li><a class=\"sw-guide-nav-link\" href=\"#failure\">Failure Modes &amp; RFQ<\/a><\/li>\n            <li><a class=\"sw-guide-nav-link\" href=\"#ultrasonic\">The Ultrasonic Boundary<\/a><\/li>\n            <li><a class=\"sw-guide-nav-link\" href=\"#tooling\">Tooling, Jaws &amp; Inspection<\/a><\/li>\n            <li><a class=\"sw-guide-nav-link\" href=\"#machines\">How ShengWei Seals<\/a><\/li>\n            <li><a class=\"sw-guide-nav-link\" href=\"#faq\">FAQ<\/a><\/li>\n          <\/ol>\n        <\/div>\n      <\/div>\n    <\/div>\n  <\/nav>\n\n<section class=\"sw-section\" id=\"thesis\">\n    <div class=\"sw-shell\">\n      <h2 class=\"sw-section-title\" style=\"text-align:left\">Sealing Is a Process Window, Not a Bag Shape<\/h2>\n\n      <p>Bag-type pages explain finished pouch formats. This guide compares the sealing technologies and failure modes behind those bags \u2014 seal strength, leak risk, film compatibility, tooling, inspection, and cost. If you are still choosing a finished pouch format \u2014 stand-up, gusseted, flat-bottom \u2014 start at our <a href=\"\/pouch-types\/\">Pouch Types Hub<\/a>; this page is about how those bags are actually welded shut and how that weld fails.<\/p>\n\n      <p>The single most useful idea in sealing is that a seal is not a setting \u2014 it is a <strong>process window<\/strong>. A heat seal forms when the film's inner sealant layer is taken into a band of temperature, pressure, and dwell time where it flows and fuses without distorting the rest of the structure. Too cold or too brief and the weld is weak; too hot or too long and the film thins, burns through, or warps. That window is a property of <em>your film<\/em>, not of the machine, which is why the same sealer is set differently for a polyethylene stand-up pouch than for a high-barrier laminate.<\/p>\n\n      <p>Two further decisions sit downstream of that window and are the reason this guide exists. First, the four common ways of delivering heat to the film \u2014 a constant-heat hot bar, an impulse ribbon, a continuous band, or ultrasonic vibration \u2014 behave differently on demanding films, and the right one is a genuine engineering choice rather than a default. Second, a seal that <em>looks<\/em> strong can still leak, so strength and leak-tightness have to be verified separately. The sections below take those in turn. For the machine-selection layer above this \u2014 which family of bagger suits your product and run \u2014 see our <a href=\"\/how-to-choose-packaging-machine\/\">guide to choosing the right packaging machine<\/a>; for how forming bags inline compares with filling pre-made pouches, see <a href=\"\/premade-bag-vs-vffs\/\">Premade Bag vs VFFS<\/a>.<\/p>\n    <\/div>\n  <\/section>\n\n<section class=\"sw-section sw-section-alt\" id=\"methods\">\n    <div class=\"sw-shell\">\n      <h2 class=\"sw-section-title\" style=\"text-align:left\">How the Four Sealing Methods Form a Weld<\/h2>\n\n      <p>All four methods end in the same place \u2014 molten sealant fused under pressure and then frozen \u2014 but they reach it differently, and that difference is what makes one suit a fragile laminate and another a recyclable mono-film.<\/p>\n\n      <p>A <strong>constant-heat hot bar<\/strong> is the workhorse. Two heated jaws are held at a steady temperature and clamp the film for a set dwell; heat conducts in from the outside. It is simple, robust, and fast to set up, but because the jaws stay hot, the seal is still warm and soft at the moment the jaws open, which gives it lower initial strength \u2014 its <em>hot-tack<\/em> \u2014 until it cools in air.<\/p>\n\n      <p>An <strong>impulse sealer<\/strong> heats only during a brief pulse of current through a ribbon element, then keeps the film clamped while it cools. Because the weld solidifies under pressure rather than in open air, impulse can produce a cleaner, more stable seal on thin or demanding structures \u2014 at the cost of a slower cycle, since each seal waits through a heat-then-cool step.<\/p>\n\n      <p>A <strong>band (rotary continuous) sealer<\/strong> carries the film between moving belts through separate heating, compression, and cooling zones in sequence. That makes it well suited to high-throughput continuous motion and to pre-made pouches, since the seal is both formed and cooled under control before the bag leaves the belts.<\/p>\n\n      <p>An <strong>ultrasonic sealer<\/strong> works on a different principle entirely: a vibrating horn drives high-frequency mechanical motion into the film, and the heat is generated <em>inside<\/em> the material by internal friction at the interface \u2014 the tool itself stays cold. Because the energy is deposited only where the layers meet and only during a short weld pulse, ultrasonic can place a narrow, repeatable seal with very little heat spread, which is the root of its advantages on heat-sensitive and recyclable films. We return to where that boundary actually pays off, and where it does not, further down.<\/p>\n\n      <figure class=\"sw-content-figure sw-figure-zoom\">\n        <img decoding=\"async\" src=\"https:\/\/www.shengweimachine.com\/wp-content\/uploads\/2026\/06\/bag-sealing-methods-mechanisms.webp\"\n             alt=\"Cross-section comparison of four sealing methods \u2014 constant-heat hot bar, impulse ribbon, continuous band, and ultrasonic \u2014 showing where heat is generated in each\"\n             loading=\"lazy\" width=\"800\" height=\"533\">\n        <button type=\"button\" class=\"sw-figure-zoom-badge\" aria-label=\"View larger image\" tabindex=\"-1\">\n          <svg viewBox=\"0 0 20 20\" aria-hidden=\"true\"><path d=\"M9 1a8 8 0 105.293 14.293l4.207 4.207 1.414-1.414-4.207-4.207A8 8 0 009 1zm0 2a6 6 0 110 12 6 6 0 010-12zm-1 3v2H6v2h2v2h2v-2h2V8h-2V6H8z\"\/><\/svg>\n        <\/button>\n        <figcaption>Where each method puts the heat: conducted in from hot jaws (hot bar, impulse, band) versus generated inside the film by vibration with a cold tool (ultrasonic).<\/figcaption>\n      <\/figure>\n    <\/div>\n  <\/section>\n\n<section class=\"sw-section\" id=\"matrix\">\n    <div class=\"sw-shell\">\n      <h2 class=\"sw-section-title\" style=\"text-align:left\">Decision Matrix \u2014 Where the Four Methods Genuinely Differ<\/h2>\n\n      <p>The comparison below is deliberately qualitative. Seal-strength and temperature figures are properties of a specific film, sealant, and line speed, not of a method in the abstract, so a clean ladder of numbers would mislead more than it helps. Use this to narrow the field; settle the exact setpoints on your own film during a trial.<\/p>\n\n      <div class=\"sw-decision-table-wrap\">\n        <table class=\"sw-decision-table\">\n          <thead>\n            <tr><th>Dimension<\/th><th>Constant-Heat Hot Bar<\/th><th>Impulse<\/th><th>Band \/ Rotary<\/th><th>Ultrasonic<\/th><\/tr>\n          <\/thead>\n          <tbody>\n            <tr>\n              <td data-label=\"Dimension\"><strong>How heat reaches the film<\/strong><\/td>\n              <td data-label=\"Hot Bar\">Conducted in from permanently hot jaws.<\/td>\n              <td data-label=\"Impulse\">Pulsed through a ribbon, then cooled under clamp.<\/td>\n              <td data-label=\"Band\">Conducted through belts in heat \u2192 compress \u2192 cool zones.<\/td>\n              <td data-label=\"Ultrasonic\">Generated inside the film by vibration; tool stays cold.<\/td>\n            <\/tr>\n            <tr>\n              <td data-label=\"Dimension\"><strong>Initial hot-tack<\/strong><\/td>\n              <td data-label=\"Hot Bar\">Lower \u2014 seal opens warm and soft.<\/td>\n              <td data-label=\"Impulse\">Higher \u2014 weld solidifies under pressure.<\/td>\n              <td data-label=\"Band\">Controlled \u2014 dedicated cooling zone before release.<\/td>\n              <td data-label=\"Ultrasonic\">High \u2014 very short, localised heat input.<\/td>\n            <\/tr>\n            <tr>\n              <td data-label=\"Dimension\"><strong>Seal-width tendency<\/strong><\/td>\n              <td data-label=\"Hot Bar\">Wider, traditional seal bands.<\/td>\n              <td data-label=\"Impulse\">Narrow to moderate.<\/td>\n              <td data-label=\"Band\">Moderate, continuous.<\/td>\n              <td data-label=\"Ultrasonic\">Narrow and precise.<\/td>\n            <\/tr>\n            <tr>\n              <td data-label=\"Dimension\"><strong>Throughput tendency<\/strong><\/td>\n              <td data-label=\"Hot Bar\">High and continuous.<\/td>\n              <td data-label=\"Impulse\">Lower \u2014 heat-then-cool cycle per seal.<\/td>\n              <td data-label=\"Band\">High \u2014 built for continuous motion.<\/td>\n              <td data-label=\"Ultrasonic\">High \u2014 very short weld cycles.<\/td>\n            <\/tr>\n            <tr>\n              <td data-label=\"Dimension\"><strong>Recyclable mono-material fit<\/strong><\/td>\n              <td data-label=\"Hot Bar\">Workable with engineered sealant layers and tight control.<\/td>\n              <td data-label=\"Impulse\">Good \u2014 cooling under clamp helps a narrow window.<\/td>\n              <td data-label=\"Band\">Good with zoned temperature control.<\/td>\n              <td data-label=\"Ultrasonic\">Often favoured \u2014 little heat spread.<\/td>\n            <\/tr>\n            <tr>\n              <td data-label=\"Dimension\"><strong>In-seal contamination tolerance<\/strong><\/td>\n              <td data-label=\"Hot Bar\">Low \u2014 product in the seal commonly causes leaks.<\/td>\n              <td data-label=\"Impulse\">Low to moderate.<\/td>\n              <td data-label=\"Band\">Low to moderate.<\/td>\n              <td data-label=\"Ultrasonic\">Can be better in specific, validated cases (see below).<\/td>\n            <\/tr>\n            <tr>\n              <td data-label=\"Dimension\"><strong>Capex tier (directional)<\/strong><\/td>\n              <td data-label=\"Hot Bar\">Entry \u2014 lowest-cost workhorse.<\/td>\n              <td data-label=\"Impulse\">Entry to mid.<\/td>\n              <td data-label=\"Band\">Mid.<\/td>\n              <td data-label=\"Ultrasonic\">Premium \u2014 added generator and tooling.<\/td>\n            <\/tr>\n          <\/tbody>\n        <\/table>\n      <\/div>\n\n      <h3 class=\"sw-title-sub\">Quick view \u2014 levers, not a verdict<\/h3>\n\n      <p><strong>Lean toward a constant-heat hot bar when<\/strong> the film is forgiving, throughput and the lowest machine cost matter most, and a well-tuned window holds the seal you need.<\/p>\n      <p><strong>Lean toward impulse or band when<\/strong> the structure is thin, heat-sensitive, or recyclable and benefits from cooling under pressure before release.<\/p>\n      <p><strong>Lean toward ultrasonic when<\/strong> in-seal contamination, a narrow recyclable-film window, very narrow seals, or energy-on-demand are the deciding factors \u2014 and the film, product, tooling, and a validation trial support it. These are engineering levers \u2014 contamination risk, film sensitivity, barrier-foil fragility, throughput, and budget \u2014 not a bag-shape lookup.<\/p>\n    <\/div>\n  <\/section>\n\n<section class=\"sw-section sw-section-alt\" id=\"window\">\n    <div class=\"sw-shell\">\n      <h2 class=\"sw-section-title\" style=\"text-align:left\">The Sealing Window \u2014 and Why Recyclable Film Is Harder<\/h2>\n\n      <p>Every heat seal lives inside a window defined by three variables working together: <strong>temperature, pressure, and dwell time<\/strong> \u2014 the TPT window. Raise one and you can often lower another \u2014 more dwell lets you seal cooler, more pressure improves contact on a textured film \u2014 but step outside the window in any direction and the seal fails in a characteristic way. Below it, the sealant never fully flows and you get a cold, weak weld; above it, the film distorts, the seal embrittles, or the web burns through.<\/p>\n\n      <figure class=\"sw-content-figure sw-figure-zoom\">\n        <img decoding=\"async\" src=\"https:\/\/www.shengweimachine.com\/wp-content\/uploads\/2026\/06\/sealing-process-window.webp\"\n             alt=\"The sealing process window where temperature, pressure and dwell time overlap to give a good seal, bounded by cold weak seals on one side and film distortion on the other\"\n             loading=\"lazy\" width=\"800\" height=\"533\">\n        <button type=\"button\" class=\"sw-figure-zoom-badge\" aria-label=\"View larger image\" tabindex=\"-1\">\n          <svg viewBox=\"0 0 20 20\" aria-hidden=\"true\"><path d=\"M9 1a8 8 0 105.293 14.293l4.207 4.207 1.414-1.414-4.207-4.207A8 8 0 009 1zm0 2a6 6 0 110 12 6 6 0 010-12zm-1 3v2H6v2h2v2h2v-2h2V8h-2V6H8z\"\/><\/svg>\n        <\/button>\n        <figcaption>A good seal lives where temperature, pressure and dwell overlap. Under-seal on one edge, film distortion on the other \u2014 and recyclable mono-material narrows the band between them.<\/figcaption>\n      <\/figure>\n\n      <p>This is where recyclable packaging changes the engineering. A traditional laminate pairs a high-melting outer layer with a low-melting inner sealant, so the temperature that fuses the seal is comfortably below the temperature that damages the structure \u2014 a wide, forgiving window. A recyclable <strong>mono-material<\/strong> film made of a single polymer family does not have that separation: the layer you melt to seal and the layer that gives the bag its strength are chemically close, so the sealing window narrows and process control gets tighter and less forgiving. That is the practical reason brands moving to recyclable structures often re-evaluate the sealing step rather than treating it as a drop-in.<\/p>\n\n      <p>The regulatory push behind this is real but frequently overstated, so it is worth being precise. The EU's Packaging and Packaging Waste Regulation (<a href=\"https:\/\/environment.ec.europa.eu\/topics\/waste-and-recycling\/packaging-waste\/packaging-packaging-waste-regulation_en\" rel=\"nofollow noopener\" target=\"_blank\">Regulation 2025\/40<\/a>) requires that packaging placed on the EU market be recyclable by 2030, graded against design-for-recycling criteria. It does <em>not<\/em> explicitly mandate mono-material construction \u2014 but because multi-layer laminates tend to grade poorly for recyclability, mono-material has become a common practical route to compliance, and with it the narrower sealing window. Methods that limit heat spread \u2014 impulse, band with zoned cooling, and ultrasonic \u2014 are part of how packers keep that narrower window under control, alongside engineered sealant layers on a well-controlled hot bar.<\/p>\n    <\/div>\n  <\/section>\n\n<section class=\"sw-section\" id=\"integrity\">\n    <div class=\"sw-shell\">\n      <h2 class=\"sw-section-title\" style=\"text-align:left\">Seal Strength vs Seal Integrity: Which Test Finds What<\/h2>\n\n      <p>The most expensive mistake in sealing is assuming a strong seal is a leak-tight seal. They are different properties, measured by different tests, and a pack can pass one while failing the other. <strong>Seal strength<\/strong> is how much force it takes to pull the seal apart; <strong>seal integrity<\/strong> is whether the seal has a leak path, however small. A wide, firmly bonded seal with a single fine channel across it can be both strong and leaking at once.<\/p>\n\n      <p>The recognised seal-test standards each answer a narrower question than people assume, and the scope matters \u2014 many originate in medical-device packaging and do not transfer wholesale to a food pouch:<\/p>\n      <ul>\n        <li><strong>Seal strength (peel):<\/strong> <a href=\"https:\/\/www.astm.org\/Standards\/F88.htm\" rel=\"nofollow noopener\" target=\"_blank\">ASTM F88<\/a> measures the force to separate a seal and the way it fails (peel, tear, or delamination). It tells you the seal is strong \u2014 not that it is leak-free.<\/li>\n        <li><strong>Fine-channel leaks, food and consumer pouches:<\/strong> <a href=\"https:\/\/www.astm.org\/Standards\/F3039.htm\" rel=\"nofollow noopener\" target=\"_blank\">ASTM F3039<\/a> is the dye-penetration test for <em>nonporous<\/em> flexible packaging \u2014 the right reference for most barrier food pouches. (The older <a href=\"https:\/\/www.astm.org\/Standards\/F1929.htm\" rel=\"nofollow noopener\" target=\"_blank\">ASTM F1929<\/a> dye test is scoped to <em>porous<\/em> medical packaging and should not be cited for a food pouch.)<\/li>\n        <li><strong>Gross leaks:<\/strong> <a href=\"https:\/\/www.astm.org\/Standards\/F2096.htm\" rel=\"nofollow noopener\" target=\"_blank\">ASTM F2096<\/a> is a simple bubble test under internal pressure that catches larger gross leaks. It is sensitive and inexpensive, but it is a gross-leak screen, not a fine-channel or burst test.<\/li>\n        <li><strong>Burst and creep:<\/strong> <a href=\"https:\/\/www.astm.org\/Standards\/F1140.htm\" rel=\"nofollow noopener\" target=\"_blank\">ASTM F1140<\/a> (unrestrained) and <a href=\"https:\/\/www.astm.org\/Standards\/F2054.htm\" rel=\"nofollow noopener\" target=\"_blank\">ASTM F2054<\/a> (restrained between plates) pressurise the pack until the seal fails, to find the weakest point.<\/li>\n        <li><strong>Vacuum decay and validation:<\/strong> ASTM F2338 (vacuum-decay leak detection) and <a href=\"https:\/\/www.iso.org\/standard\/70800.html\" rel=\"nofollow noopener\" target=\"_blank\">ISO 11607-2<\/a> (sterile-barrier process validation, IQ\/OQ\/PQ) cover regulated and high-barrier work.<\/li>\n      <\/ul>\n\n      <p>The takeaway for a buyer is to specify both a strength test and a leak test for the product, and to match the leak test to the package \u2014 a bubble test for gross screening, a dye-penetration test for the fine channels that defeat a strong-looking seal. Different finished formats present the seal differently, too, which is part of why the bag style and the sealing method are chosen together:<\/p>\n\n      <div class=\"sw-components-grid sw-components-grid--4col\">\n        <div class=\"sw-component-card\">\n          <img decoding=\"async\" class=\"sw-component-card__img sw-component-card__img--dark\" src=\"https:\/\/www.shengweimachine.com\/wp-content\/uploads\/2024\/01\/3-Side-Seal-Pouch.webp\" alt=\"Three-side-seal pouch with seals on three edges\" loading=\"lazy\" width=\"500\" height=\"500\">\n          <div class=\"sw-component-card__body\">\n            <p class=\"sw-component-card__name\">Three-side seal<\/p>\n            <p class=\"sw-component-card__desc\">Three weld lines and one folded edge to verify.<\/p>\n          <\/div>\n        <\/div>\n        <div class=\"sw-component-card\">\n          <img decoding=\"async\" class=\"sw-component-card__img sw-component-card__img--dark\" src=\"https:\/\/www.shengweimachine.com\/wp-content\/uploads\/2024\/01\/4-Side-Seal-Pouch.webp\" alt=\"Four-side-seal sachet sealed on all four edges\" loading=\"lazy\" width=\"500\" height=\"500\">\n          <div class=\"sw-component-card__body\">\n            <p class=\"sw-component-card__name\">Four-side seal<\/p>\n            <p class=\"sw-component-card__desc\">Four weld lines \u2014 the most seal length to inspect.<\/p>\n          <\/div>\n        <\/div>\n        <div class=\"sw-component-card\">\n          <img decoding=\"async\" class=\"sw-component-card__img sw-component-card__img--dark\" src=\"https:\/\/www.shengweimachine.com\/wp-content\/uploads\/2024\/01\/Back-Seal-Pouch.webp\" alt=\"Back-seal pouch with a seam down the back\" loading=\"lazy\" width=\"500\" height=\"500\">\n          <div class=\"sw-component-card__body\">\n            <p class=\"sw-component-card__name\">Back seal<\/p>\n            <p class=\"sw-component-card__desc\">A back seam plus top and bottom welds \u2014 three to check.<\/p>\n          <\/div>\n        <\/div>\n        <div class=\"sw-component-card\">\n          <img decoding=\"async\" class=\"sw-component-card__img sw-component-card__img--dark\" src=\"https:\/\/www.shengweimachine.com\/wp-content\/uploads\/2024\/01\/Fin-Seal-Pouch.webp\" alt=\"Fin-seal pouch with a fin seam where the film inner faces meet\" loading=\"lazy\" width=\"500\" height=\"500\">\n          <div class=\"sw-component-card__body\">\n            <p class=\"sw-component-card__name\">Fin seal<\/p>\n            <p class=\"sw-component-card__desc\">Inner faces welded into a standing fin \u2014 a common leak point.<\/p>\n          <\/div>\n        <\/div>\n      <\/div>\n      <p>Different seam geometries put the seal in different places \u2014 which is why format and sealing method are specified together. For the full set of finished formats, see the <a href=\"\/pouch-types\/\">Pouch Types Hub<\/a> and the <a href=\"\/3-side-seal-pouch-packing-machine\/\">three-side-seal<\/a>, <a href=\"\/4-side-seal-pouch-packing-machine\/\">four-side-seal<\/a> and <a href=\"\/back-seal-pouch-packing-machine\/\">back-seal<\/a> machine pages.<\/p>\n    <\/div>\n  <\/section>\n\n<section class=\"sw-section sw-section-alt\" id=\"failure\">\n    <div class=\"sw-shell\">\n      <h2 class=\"sw-section-title\" style=\"text-align:left\">The Failure Modes You'll Actually Meet \u2014 and the RFQ That Pre-empts Them<\/h2>\n\n      <p>Seals fail in a small number of recognisable ways, and naming the ones relevant to your product is half of writing a good request for quotation. Each has a mechanism and a test that catches it.<\/p>\n\n      <ul>\n        <li><strong>Product-in-seal capillary leak<\/strong> \u2014 a common, high-risk path: powder, fines, grease, or liquid lands on the seal surface and leaves a microscopic channel that a dye-penetration test reveals even though the seal pulls strong. This is the failure ultrasonic is sometimes brought in to address.<\/li>\n        <li><strong>Cold or under-seal<\/strong> \u2014 too little temperature, pressure, or dwell, so the sealant never fully fuses; the seal looks closed but peels open or leaks.<\/li>\n        <li><strong>Burnt or over-seal<\/strong> \u2014 too much heat or dwell thins and embrittles the film at the seal edge, so it cracks under flex.<\/li>\n        <li><strong>Wrinkle or crease leak<\/strong> \u2014 a fold caught in the seal leaves a channel; common at corners and at zipper or gusset transitions.<\/li>\n        <li><strong>Barrier-foil micro-crack<\/strong> \u2014 hard jaw impact fractures a thin foil layer, opening a slow leak that only vacuum-decay testing tends to find.<\/li>\n        <li><strong>Edge-shear and delamination<\/strong> \u2014 the seal survives but thins the film at its edge, or the layers separate, weakening the pack over its shelf life.<\/li>\n      <\/ul>\n\n      <figure class=\"sw-content-figure sw-figure-zoom\">\n        <img decoding=\"async\" src=\"https:\/\/www.shengweimachine.com\/wp-content\/uploads\/2026\/06\/seal-failure-modes.webp\"\n             alt=\"Diagram of common seal failure modes \u2014 product-in-seal channel, cold seal, burnt seal, wrinkle leak, barrier-foil crack and delamination\"\n             loading=\"lazy\" width=\"800\" height=\"533\">\n        <button type=\"button\" class=\"sw-figure-zoom-badge\" aria-label=\"View larger image\" tabindex=\"-1\">\n          <svg viewBox=\"0 0 20 20\" aria-hidden=\"true\"><path d=\"M9 1a8 8 0 105.293 14.293l4.207 4.207 1.414-1.414-4.207-4.207A8 8 0 009 1zm0 2a6 6 0 110 12 6 6 0 010-12zm-1 3v2H6v2h2v2h2v-2h2V8h-2V6H8z\"\/><\/svg>\n        <\/button>\n        <figcaption>The seal failure modes worth naming in an RFQ, each paired with the test that catches it.<\/figcaption>\n      <\/figure>\n\n      <p>A good RFQ states the film structure and sealant, the product and whether it dusts or carries grease, the bag format and any zipper or gusset, the throughput, and the seal-integrity standard you will test against. That lets a supplier specify the right method, jaw design, and inspection up front rather than discovering the failure mode in production.<\/p>\n    <\/div>\n  <\/section>\n\n<section class=\"sw-section\" id=\"ultrasonic\">\n    <div class=\"sw-shell\">\n      <h2 class=\"sw-section-title\" style=\"text-align:left\">The Ultrasonic Boundary: Where a Cold Tool Earns Its Premium<\/h2>\n\n      <p>Ultrasonic sealing attracts a lot of claims, so it is worth separating the mechanism \u2014 which is sound \u2014 from the marketing. Because the heat is generated inside the film during a short weld pulse and the tool stays cold, ultrasonic concentrates energy precisely at the seal interface. Ultrasonic systems such as Herrmann's commonly run at around 20\u201335 kHz with controlled amplitudes on the order of 9\u201335 microns, tuned to the film and the seal geometry; in that Herrmann\/Mespack source, higher-frequency systems are positioned for narrower seals (vendor and OEM figures, application-specific). That precise, low-spread energy is the real basis for its two headline advantages.<\/p>\n\n      <p>The first is contamination tolerance, and the honest version is conditional. In a widely cited trade case, the Oberto beef-jerky line moved from hot-bar to ultrasonic sealing on a vertical bagger and reported that the seals could close through jerky fines that had been causing leakers \u2014 the bags held a two-hour test at 25 inches of vacuum from the start, the seal surface shrank from about 1.25 inches to under a quarter of an inch, and output rose from roughly 35\u201340 to 75 bags per minute (<a href=\"https:\/\/www.packagingstrategies.com\/articles\/89966-case-study-the-oberto-sausage-company-seeks-a-sealing-change\" rel=\"nofollow noopener\" target=\"_blank\">Packaging Strategies, 2017<\/a>). That is a real, named result \u2014 but it is one product, one machine, one validation. The right way to generalise it is narrow: ultrasonic <em>can<\/em> improve sealing through some in-seal contamination, on the right film, after a trial proves it for your product. It is not a universal \"seals through anything\" capability, and some release additives and trapped moisture can interfere with it.<\/p>\n\n      <p>The second advantage is energy and material. Because there is no warm-up and no heated tool to hold at temperature, the generator draws power only during the weld; Herrmann reports up to around 75% less sealing energy than continuously heated jaws (vendor claim). Narrower seals can also trim film: one snack-package case reported about an 11% material saving by shrinking the end seals, under that application's specific conditions \u2014 a case figure, not a guaranteed number. Ultrasonic has also been licensed for sealing <em>uncoated paper<\/em> (Syntegon handed exclusive rights for the process to Herrmann in 2023), which matters as paper-based recyclable formats grow. The takeaway is not that ultrasonic wins \u2014 it is that on contamination-prone, heat-sensitive, recyclable, or narrow-seal work it is worth evaluating against a well-controlled hot bar, which remains the broader, lower-cost default everywhere else.<\/p>\n    <\/div>\n  <\/section>\n\n<section class=\"sw-section sw-section-alt\" id=\"tooling\">\n    <div class=\"sw-shell\">\n      <h2 class=\"sw-section-title\" style=\"text-align:left\">Tooling, Jaw Control &amp; Inspection: Where Reliability Is Won<\/h2>\n\n      <p>Once the method is chosen, day-to-day seal reliability is decided by the tooling and the control of the jaws \u2014 the unglamorous details that separate a seal that holds for a shift from one that drifts.<\/p>\n\n      <p>On heat sealers, the jaw face does the work: serration or knurling patterns set how the film is gripped and how heat transfers, and a clean, flat, evenly heated face is what keeps a seal consistent across its width. Worn or contaminated jaws are a leading cause of intermittent leaks. <strong>Jaw control<\/strong> matters just as much as jaw shape \u2014 a hard mechanical clamp lands the full force in an instant, while a <em>servo-driven<\/em> jaw can soft-land and apply force in stages. That staged force can reduce impact damage to fragile barrier foils and improve seal consistency at speed (a control feature worth asking about where foil micro-cracking is a risk). Ultrasonic brings its own tooling discipline: the horn and anvil are precision acoustic parts, the energy-director geometry shapes the weld, and abrasive fillers wear the horn over time, so tooling life is part of the cost case.<\/p>\n\n      <figure class=\"sw-content-figure sw-figure-zoom\">\n        <img decoding=\"async\" src=\"https:\/\/www.shengweimachine.com\/wp-content\/uploads\/2026\/03\/dual-sealing-station-premade-bag-granule-packing-machine.webp\"\n             alt=\"Close-up of a dual heat-sealing station on a ShengWei premade-bag packing machine, showing the sealing jaws\"\n             loading=\"lazy\" width=\"571\" height=\"343\">\n        <button type=\"button\" class=\"sw-figure-zoom-badge\" aria-label=\"View larger image\" tabindex=\"-1\">\n          <svg viewBox=\"0 0 20 20\" aria-hidden=\"true\"><path d=\"M9 1a8 8 0 105.293 14.293l4.207 4.207 1.414-1.414-4.207-4.207A8 8 0 009 1zm0 2a6 6 0 110 12 6 6 0 010-12zm-1 3v2H6v2h2v2h2v-2h2V8h-2V6H8z\"\/><\/svg>\n        <\/button>\n        <figcaption>A dual heat-sealing station on a ShengWei premade-bag machine \u2014 independent seal bars let one pass pre-flatten and the next finish the seal.<\/figcaption>\n      <\/figure>\n\n      <p>Inspection closes the loop. For most food and consumer work, a combination of a periodic destructive test on the line (a peel test and a dye or bubble leak test on sampled packs) plus continuous visual or vision checking is enough to hold quality. Sterile, medical, and high-barrier packaging go further, into formal process validation and in-line vacuum-decay or seal-monitoring systems. Whatever the level, the principle from the test section holds: verify strength and leak-tightness separately, because the line that only checks one will eventually ship the other.<\/p>\n    <\/div>\n  <\/section>\n\n<section class=\"sw-section\" id=\"machines\">\n    <div class=\"sw-shell\">\n      <h2 class=\"sw-section-title\" style=\"text-align:left\">How ShengWei Seals \u2014 and Proves the Sealing Window<\/h2>\n\n      <p>Across ShengWei's published machines, heat sealing is configured around the bag format and film rather than fixed; where ultrasonic is relevant to your product, treat it as a separate validation and add-on discussion. Our vertical form-fill-seal machines build the bag and seal it inline: the <a href=\"\/full-automatic-vertical-packing-machine\/automatic-six-column-three-side-sealing-vertical-packaging-machine\/\">six-column three-side-seal machine<\/a> and <a href=\"\/full-automatic-vertical-packing-machine\/automatic-six-column-four-side-sealing-vertical-packaging-machine\/\">six-column four-side-seal machine<\/a> run multi-lane sachets, while the <a href=\"\/full-automatic-vertical-packing-machine\/automatic-ten-columns-back-sealing-vertical-packaging-machine\/\">ten-column back-seal machine<\/a> forms a back seam at high lane counts. These sit on our wider <a href=\"\/full-automatic-vertical-packing-machine\/\">full-automatic vertical platform<\/a>.<\/p>\n\n      <p>For pre-made pouches, a <a href=\"\/premade-bag-packing-machine\/\">premade-bag machine<\/a> grips a finished bag and seals it across dedicated stations \u2014 often a first pass to flatten and a second to finish the seal, with temperature controlled per station. Where you want the bag-format decision first, start at the <a href=\"\/pouch-types\/\">Pouch Types Hub<\/a> and the format pages for <a href=\"\/stand-up-pouch-packing-machine\/\">stand-up pouches<\/a>, <a href=\"\/gusset-bag-packing-machine\/\">gusseted bags<\/a>, and <a href=\"\/flat-bottom-pouch-packing-machine\/\">flat-bottom pouches<\/a>; a re-closable <a href=\"\/zipper-pouch-packing-machine\/\">zipper<\/a> is a closure feature added to those formats, with its own seal-integrity considerations at the zipper track.<\/p>\n\n      <p>For sample trials and project validation, we can run your film and product and check sample seals before shipment, so the sealing window is proven on a trial rather than discovered at your plant \u2014 ask us to include sample seal checks in the pre-shipment plan. You can see how we inspect and run-test equipment at the <a href=\"\/factory\/\">Factory &amp; Quality Center<\/a>. For where the sealing choice sits in the wider quote, see our <a href=\"\/packaging-machine-price-guide\/\">Packaging Machine Price Guide<\/a>; for the dosing system that fills the bag, our <a href=\"\/multi-head-weigher-vs-auger-filler\/\">dosing-methods comparison<\/a>.<\/p>\n    <\/div>\n  <\/section>\n\n<section class=\"sw-section sw-section-alt\" id=\"faq\">\n    <div class=\"sw-shell\">\n      <h2 class=\"sw-section-title\" style=\"text-align:left\">Frequently Asked Questions<\/h2>\n\n      <div class=\"sw-accordion\">\n\n        <details>\n          <summary><h3>What is the difference between heat seal, impulse, band, and ultrasonic sealing?<\/h3><\/summary>\n          <p>They differ in how heat reaches the film. A constant-heat hot bar clamps the film between permanently hot jaws and conducts heat in from outside. An impulse sealer heats only during a brief pulse and holds the film clamped while it cools, which can give a cleaner seal on thin film. A band or rotary sealer carries the film through separate heating, compression, and cooling zones for continuous running. An ultrasonic sealer vibrates a cold horn to generate heat inside the film itself, placing a narrow, low-heat-spread seal. The right one depends on your film, format, throughput, and budget.<\/p>\n        <\/details>\n\n        <details>\n          <summary><h3>What is the sealing window, and why does it matter?<\/h3><\/summary>\n          <p>The sealing window is the range of temperature, pressure, and dwell time in which a particular film seals well. Inside it, the sealant flows and fuses without damaging the rest of the structure; below it the seal is cold and weak, and above it the film distorts or burns through. The window is a property of your film, not of the machine, which is why setpoints are proven on a trial rather than copied between products. Recyclable mono-material films have a narrower window than traditional laminates, so they demand tighter process control.<\/p>\n        <\/details>\n\n        <details>\n          <summary><h3>Why do my bags leak even when the seal looks strong?<\/h3><\/summary>\n          <p>Because seal strength and seal integrity are different things. Strength is the force needed to pull the seal apart; integrity is whether any leak path exists. A wide, firmly bonded seal can still carry a microscopic channel \u2014 most often where product, powder, grease, or a wrinkle landed in the seal area \u2014 and that channel leaks even though the seal pulls strong. The fix is to test both: a peel test for strength and a dye-penetration or bubble test for leaks.<\/p>\n        <\/details>\n\n        <details>\n          <summary><h3>How do I test seal integrity \u2014 and which test for what?<\/h3><\/summary>\n          <p>Match the test to the question. ASTM F88 measures seal strength by peeling the seal apart. For leaks in nonporous food and consumer pouches, ASTM F3039 is the dye-penetration test that finds fine channels; ASTM F1929 is the equivalent for porous medical packaging only. ASTM F2096 is a quick bubble test for larger gross leaks. ASTM F1140 and F2054 pressurise the pack to burst to find the weakest point. Vacuum-decay testing and ISO 11607-2 validation cover high-barrier and sterile work. Specify at least one strength test and one leak test appropriate to your package.<\/p>\n        <\/details>\n\n        <details>\n          <summary><h3>Can ultrasonic sealing work through powder or grease in the seal area?<\/h3><\/summary>\n          <p>Sometimes, and only after validation. Because ultrasonic generates heat inside the film and disturbs the interface, it can in specific cases seal through light contamination that defeats a hot bar \u2014 a widely cited beef-jerky line reported sealing through product fines and passing a two-hour vacuum test after switching to ultrasonic. But that is one validated application, not a general guarantee: the result depends on the film, the type and amount of contamination, the horn and anvil geometry, and a trial on your own product. Treat it as something to evaluate, not assume.<\/p>\n        <\/details>\n\n        <details>\n          <summary><h3>Why is recyclable mono-material film harder to seal?<\/h3><\/summary>\n          <p>A traditional laminate uses a high-melting outer layer and a low-melting inner sealant, so there is a wide gap between the temperature that seals and the temperature that damages the film. A mono-material film is a single polymer family, so the sealing layer and the structural layer melt at close temperatures and the safe window between \"sealed\" and \"distorted\" narrows. That means tighter temperature control and often a method that limits heat spread \u2014 impulse, zoned band, or ultrasonic \u2014 though a well-controlled hot bar with an engineered sealant layer can also work.<\/p>\n        <\/details>\n\n        <details>\n          <summary><h3>When is ultrasonic worth it versus heat sealing?<\/h3><\/summary>\n          <p>Ultrasonic earns its higher cost on a bounded set of problems: in-seal contamination that causes leakers, heat-sensitive or recyclable films with a narrow window, very narrow precise seals, and a wish to cut sealing energy. Outside those, a constant-heat hot bar remains the broader, lower-cost workhorse for most food and consumer bags. The decision is not \"which is better\" but \"does my specific problem fall inside ultrasonic's boundary\" \u2014 and that is settled by a trial on your film and product.<\/p>\n        <\/details>\n\n        <details>\n          <summary><h3>What causes a barrier-foil micro-leak, and how is it reduced?<\/h3><\/summary>\n          <p>A thin foil or metallised barrier layer can crack when the sealing jaws land hard, opening a slow leak that often only vacuum-decay testing detects. It is reduced by controlling how the jaws close: a servo-driven jaw can soft-land and apply force in stages rather than slamming shut, which lowers peak impact on the foil, and by keeping jaw faces clean and flat. Where foil micro-cracking is a known risk, ask suppliers about servo jaw control and about in-line vacuum-decay or seal monitoring.<\/p>\n        <\/details>\n\n        <details>\n          <summary><h3>What lead time should I expect on a sealing machine from China?<\/h3><\/summary>\n          <p>ShengWei base models \u2014 standard configurations of our vertical and premade-bag machines \u2014 ship in 15\u201320 days ex-works. Custom multi-lane builds and complete integrated lines run longer; confirm the scope in the RFQ. Add roughly four to six weeks of ocean transit when comparing an ex-works lead time against a delivered one, and treat seal-integrity testing equipment and any special tooling as line items in the quote rather than afterthoughts.<\/p>\n        <\/details>\n\n      <\/div>\n    <\/div>\n  <\/section>\n\n<section class=\"sw-cta-dark\" id=\"cta\">\n    <div class=\"sw-shell\">\n      <div class=\"sw-cta-grid\">\n        <div>\n          <span class=\"sw-eyebrow\">Ready to Decide<\/span>\n          <h2 class=\"sw-section-title\" style=\"text-align:left\">Send Your Film and Product for a Sealing Recommendation<\/h2>\n          <p class=\"sw-lead\">Send us your film structure and sealant, your product and whether it dusts or carries grease, the bag format, your throughput, and the seal-integrity standard you test against. We'll write back with a recommended sealing method, the machine it runs on, the jaw and tooling notes that matter for your film, whether your product warrants ultrasonic, and lead time and shipping notes for your region. We usually reply within one business day, on business days.<\/p>\n          <p class=\"sw-workflow-text\">info@shengweimachine.com &middot; +86 181 2511 2025 &middot; or <a href=\"\/contact\/\">contact our engineering team<\/a> directly<\/p>\n          <div class=\"sw-sales-signature\" id=\"author\">\n            <img decoding=\"async\" src=\"https:\/\/www.shengweimachine.com\/wp-content\/uploads\/2026\/04\/hellena-ji-international-sales-manager-150x150.webp\"\n                 alt=\"Hellena Ji, International Sales Manager at ShengWei Machine\"\n                 loading=\"lazy\" width=\"80\" height=\"80\">\n            <div>\n              <strong>Hellena Ji<\/strong><br>\n              International Sales Manager &middot; <a href=\"\/about-us\/\">ShengWei Machine<\/a>\n            <\/div>\n          <\/div>\n        <\/div>\n      <\/div>\n\n      <div class=\"sw-cta-buttons\">\n        <a href=\"javascript:void(0)\"\n           onclick=\"elementorProFrontend.modules.popup.showPopup({id:840})\"\n           data-elementor-open-popup=\"840\"\n           class=\"sw-btn-primary\">Send my film and product spec &rarr;<\/a>\n      <\/div>\n    <\/div>\n  <\/section>\n\n<script type=\"application\/ld+json\">\n  [\n    {\n      \"@context\": \"https:\/\/schema.org\",\n      \"@type\": \"BreadcrumbList\",\n      \"itemListElement\": [\n        {\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\/\/www.shengweimachine.com\/\"},\n        {\"@type\":\"ListItem\",\"position\":2,\"name\":\"Buying Guides\",\"item\":\"https:\/\/www.shengweimachine.com\/buying-guides\/\"},\n        {\"@type\":\"ListItem\",\"position\":3,\"name\":\"Bag Sealing Methods Compared\",\"item\":\"https:\/\/www.shengweimachine.com\/bag-seal-types-comparison\/\"}\n      ]\n    },\n    {\n      \"@context\": \"https:\/\/schema.org\",\n      \"@type\": \"Article\",\n      \"headline\": \"Bag Sealing Methods Compared: Heat Seal, Impulse, Band & Ultrasonic: The Seal Integrity, TPT Window & Failure-Mode Guide\",\n      \"description\": \"Heat seal, impulse, band, or ultrasonic? Compare bag sealing methods on the sealing window, seal integrity versus seal strength, leak failure modes, recyclable-film fit, tooling, and cost.\",\n      \"image\": \"https:\/\/www.shengweimachine.com\/wp-content\/uploads\/2024\/09\/Automatic-Six-Column-Three-Side-Sealing-Vertical-Packaging-Machine.webp\",\n      \"datePublished\": \"2026-06-10\",\n      \"dateModified\": \"2026-06-10\",\n      \"author\": {\n        \"@type\": \"Person\",\n        \"name\": \"Hellena Ji\",\n        \"jobTitle\": \"International Sales Manager\",\n        \"worksFor\": {\"@type\":\"Organization\",\"name\":\"ShengWei Machine\"},\n        \"sameAs\": \"https:\/\/www.shengweimachine.com\/about-us\/\"\n      },\n      \"publisher\": {\n        \"@type\": \"Organization\",\n        \"name\": \"ShengWei Machine\",\n        \"url\": \"https:\/\/www.shengweimachine.com\/\",\n        \"logo\": {\"@type\":\"ImageObject\",\"url\":\"https:\/\/www.shengweimachine.com\/wp-content\/uploads\/2024\/01\/shengwei-logo.webp\"}\n      },\n      \"mainEntityOfPage\": {\"@type\":\"WebPage\",\"@id\":\"https:\/\/www.shengweimachine.com\/bag-seal-types-comparison\/\"},\n      \"inLanguage\": \"en-US\"\n    },\n    {\n      \"@context\": \"https:\/\/schema.org\",\n      \"@type\": \"FAQPage\",\n      \"mainEntity\": [\n        {\"@type\":\"Question\",\"name\":\"What is the difference between heat seal, impulse, band, and ultrasonic sealing?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"They differ in how heat reaches the film. A constant-heat hot bar clamps the film between permanently hot jaws and conducts heat in from outside. An impulse sealer heats only during a brief pulse and holds the film clamped while it cools, which can give a cleaner seal on thin film. A band or rotary sealer carries the film through separate heating, compression, and cooling zones for continuous running. An ultrasonic sealer vibrates a cold horn to generate heat inside the film itself, placing a narrow, low-heat-spread seal. The right one depends on your film, format, throughput, and budget.\"}},\n        {\"@type\":\"Question\",\"name\":\"What is the sealing window, and why does it matter?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"The sealing window is the range of temperature, pressure, and dwell time in which a particular film seals well. Inside it, the sealant flows and fuses without damaging the rest of the structure; below it the seal is cold and weak, and above it the film distorts or burns through. The window is a property of your film, not of the machine, which is why setpoints are proven on a trial rather than copied between products. Recyclable mono-material films have a narrower window than traditional laminates, so they demand tighter process control.\"}},\n        {\"@type\":\"Question\",\"name\":\"Why do my bags leak even when the seal looks strong?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Because seal strength and seal integrity are different things. Strength is the force needed to pull the seal apart; integrity is whether any leak path exists. A wide, firmly bonded seal can still carry a microscopic channel \u2014 most often where product, powder, grease, or a wrinkle landed in the seal area \u2014 and that channel leaks even though the seal pulls strong. The fix is to test both: a peel test for strength and a dye-penetration or bubble test for leaks.\"}},\n        {\"@type\":\"Question\",\"name\":\"How do I test seal integrity \u2014 and which test for what?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Match the test to the question. ASTM F88 measures seal strength by peeling the seal apart. For leaks in nonporous food and consumer pouches, ASTM F3039 is the dye-penetration test that finds fine channels; ASTM F1929 is the equivalent for porous medical packaging only. ASTM F2096 is a quick bubble test for larger gross leaks. ASTM F1140 and F2054 pressurise the pack to burst to find the weakest point. Vacuum-decay testing and ISO 11607-2 validation cover high-barrier and sterile work. Specify at least one strength test and one leak test appropriate to your package.\"}},\n        {\"@type\":\"Question\",\"name\":\"Can ultrasonic sealing work through powder or grease in the seal area?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Sometimes, and only after validation. Because ultrasonic generates heat inside the film and disturbs the interface, it can in specific cases seal through light contamination that defeats a hot bar \u2014 a widely cited beef-jerky line reported sealing through product fines and passing a two-hour vacuum test after switching to ultrasonic. But that is one validated application, not a general guarantee: the result depends on the film, the type and amount of contamination, the horn and anvil geometry, and a trial on your own product. Treat it as something to evaluate, not assume.\"}},\n        {\"@type\":\"Question\",\"name\":\"Why is recyclable mono-material film harder to seal?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"A traditional laminate uses a high-melting outer layer and a low-melting inner sealant, so there is a wide gap between the temperature that seals and the temperature that damages the film. A mono-material film is a single polymer family, so the sealing layer and the structural layer melt at close temperatures and the safe window between sealed and distorted narrows. That means tighter temperature control and often a method that limits heat spread \u2014 impulse, zoned band, or ultrasonic \u2014 though a well-controlled hot bar with an engineered sealant layer can also work.\"}},\n        {\"@type\":\"Question\",\"name\":\"When is ultrasonic worth it versus heat sealing?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Ultrasonic earns its higher cost on a bounded set of problems: in-seal contamination that causes leakers, heat-sensitive or recyclable films with a narrow window, very narrow precise seals, and a wish to cut sealing energy. Outside those, a constant-heat hot bar remains the broader, lower-cost workhorse for most food and consumer bags. The decision is not which is better but whether your specific problem falls inside ultrasonic's boundary \u2014 and that is settled by a trial on your film and product.\"}},\n        {\"@type\":\"Question\",\"name\":\"What causes a barrier-foil micro-leak, and how is it reduced?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"A thin foil or metallised barrier layer can crack when the sealing jaws land hard, opening a slow leak that often only vacuum-decay testing detects. It is reduced by controlling how the jaws close: a servo-driven jaw can soft-land and apply force in stages rather than slamming shut, which lowers peak impact on the foil, and by keeping jaw faces clean and flat. Where foil micro-cracking is a known risk, ask suppliers about servo jaw control and about in-line vacuum-decay or seal monitoring.\"}},\n        {\"@type\":\"Question\",\"name\":\"What lead time should I expect on a sealing machine from China?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"ShengWei base models \u2014 standard configurations of our vertical and premade-bag machines \u2014 ship in 15-20 days ex-works. Custom multi-lane builds and complete integrated lines run longer; confirm the scope in the RFQ. Add roughly four to six weeks of ocean transit when comparing an ex-works lead time against a delivered one, and treat seal-integrity testing equipment and any special tooling as line items in the quote rather than afterthoughts.\"}}\n      ]\n    }\n  ]\n  <\/script>\n\n  <div id=\"sealLightboxOverlay\" class=\"sw-lightbox\" onclick=\"sealCloseLightbox(event)\" role=\"dialog\" aria-modal=\"true\" aria-label=\"Enlarged figure\" aria-hidden=\"true\">\n    <img class=\"sw-lightbox__img\" alt=\"\" id=\"sealLightboxImg\">\n    <button type=\"button\" class=\"sw-lightbox__close\" onclick=\"sealCloseLightbox(event)\" aria-label=\"Close enlarged figure\">&times;<\/button>\n    <div class=\"sw-lightbox__caption\" id=\"sealLightboxCap\"><\/div>\n  <\/div>\n\n  <script>\n  (function(){\n    var overlay = document.getElementById('sealLightboxOverlay');\n    if (!overlay) return;\n    var img = document.getElementById('sealLightboxImg');\n    var cap = document.getElementById('sealLightboxCap');\n\n    function show(src, alt, caption){\n      img.src = src;\n      img.alt = alt || '';\n      cap.textContent = caption || '';\n      overlay.classList.add('is-open');\n      overlay.setAttribute('aria-hidden', 'false');\n      document.body.style.overflow = 'hidden';\n    }\n    function openFig(figure){\n      var i = figure.querySelector('img');\n      if (!i) return;\n      var c = figure.querySelector('figcaption');\n      show(i.currentSrc || i.src, i.alt, c ? c.textContent.trim() : '');\n    }\n    function openCard(card){\n      var i = card.querySelector('img');\n      if (!i) return;\n      var n = card.querySelector('.sw-component-card__name');\n      var d = card.querySelector('.sw-component-card__desc');\n      var caption = [n ? n.textContent.trim() : '', d ? d.textContent.trim() : ''].filter(Boolean).join(' \u2014 ');\n      show(i.currentSrc || i.src, i.alt, caption);\n    }\n    function closeFig(){\n      overlay.classList.remove('is-open');\n      overlay.setAttribute('aria-hidden', 'true');\n      document.body.style.overflow = '';\n    }\n\n    document.querySelectorAll('.sw-figure-zoom').forEach(function(fig){\n      fig.addEventListener('click', function(e){\n        if (e.target.closest('a')) return;\n        e.preventDefault();\n        openFig(fig);\n      });\n    });\n    document.querySelectorAll('.sw-component-card').forEach(function(card){\n      card.addEventListener('click', function(e){\n        if (e.target.closest('a')) return;\n        openCard(card);\n      });\n    });\n\n    window.sealCloseLightbox = function(e){\n      if (e && e.target && e.target.tagName === 'IMG' && e.target.id === 'sealLightboxImg') return;\n      closeFig();\n    };\n\n    document.addEventListener('keydown', function(e){\n      if (e.key === 'Escape' && overlay.classList.contains('is-open')) closeFig();\n    });\n  })();\n  <\/script>\n\n<\/div>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"","protected":false},"author":0,"featured_media":1587,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-3255","page","type-page","status-publish","has-post-thumbnail","hentry"],"_links":{"self":[{"href":"https:\/\/www.shengweimachine.com\/zh\/wp-json\/wp\/v2\/pages\/3255","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.shengweimachine.com\/zh\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.shengweimachine.com\/zh\/wp-json\/wp\/v2\/types\/page"}],"replies":[{"embeddable":true,"href":"https:\/\/www.shengweimachine.com\/zh\/wp-json\/wp\/v2\/comments?post=3255"}],"version-history":[{"count":1,"href":"https:\/\/www.shengweimachine.com\/zh\/wp-json\/wp\/v2\/pages\/3255\/revisions"}],"predecessor-version":[{"id":3256,"href":"https:\/\/www.shengweimachine.com\/zh\/wp-json\/wp\/v2\/pages\/3255\/revisions\/3256"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.shengweimachine.com\/zh\/wp-json\/wp\/v2\/media\/1587"}],"wp:attachment":[{"href":"https:\/\/www.shengweimachine.com\/zh\/wp-json\/wp\/v2\/media?parent=3255"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}