{"id":7690,"date":"2025-08-21T09:00:00","date_gmt":"2025-08-21T08:00:00","guid":{"rendered":"https:\/\/uplastech.com\/vacuum-forming-cooling-cycle-time\/"},"modified":"2025-08-21T09:00:00","modified_gmt":"2025-08-21T08:00:00","slug":"vacuum-forming-cooling-cycle-time","status":"publish","type":"post","link":"https:\/\/uplastech.com\/nl\/vacuum-forming-cooling-cycle-time\/","title":{"rendered":"Cooling and Cycle Time in Vacuum Forming"},"content":{"rendered":"<style>\n.upl-blog{font-size:17px;line-height:1.78;color:#1f2937}\n.upl-blog p{margin:0 0 18px}\n.upl-blog h2{font-size:26px;line-height:1.3;color:#0b2b33;margin:46px 0 14px;font-weight:700;letter-spacing:-.015em}\n.upl-blog h3{font-size:19.5px;color:#0d3b47;margin:28px 0 10px;font-weight:700}\n.upl-blog ul,.upl-blog ol{margin:0 0 20px;padding-left:22px}\n.upl-blog li{margin:0 0 9px}\n.upl-blog figure{margin:0 0 34px}\n.upl-blog figure img{width:100%;height:auto;display:block;border-radius:10px}\n.upl-blog figcaption{font-size:13px;color:#6b7280;margin-top:10px;line-height:1.5}\n.upl-blog .toc{background:none;border:0;border-radius:0;padding:0;margin:0 0 34px}\n.upl-blog .toc .lwptoc{margin:0}\n.upl-blog .toc h4{margin:0 0 10px;font-size:13px;letter-spacing:.1em;text-transform:uppercase;color:#0d5563}\n.upl-blog .toc ol{margin:0;padding-left:18px;font-size:14.5px}\n.upl-blog .toc li{margin-bottom:6px}\n.upl-blog table{width:100%;border-collapse:collapse;font-size:14.5px;margin:0 0 10px}\n.upl-blog th{background:#0d3b47;color:#fff;text-align:left;padding:11px 13px;font-weight:600;font-size:13.5px;border:0}\n.upl-blog td{padding:11px 13px;border:0;border-bottom:1px solid #e8ebed;vertical-align:top}\n.upl-blog tbody tr:nth-child(even){background:#fafbfc}\n.upl-blog .tablecap{font-size:12.5px;color:#6b7280;margin:0 0 30px}\n.upl-blog .myth{background:#fff8ef;border:1px solid #f6ddbd;border-radius:8px;padding:16px 20px;margin:0 0 26px;font-size:15.5px}\n.upl-blog .myth b{color:#a85c10}\n.upl-blog .callout{background:#f2f8f9;border-radius:8px;padding:18px 22px;margin:0 0 26px;font-size:15.5px;border-left:3px solid #14707f}\n.upl-blog .faq h3{border-top:1px solid #eceff1;padding-top:22px;margin-top:0;font-size:18px}\n.upl-blog .faq h3:first-of-type{border-top:0;padding-top:0}\n.upl-blog .cta{background:linear-gradient(135deg,#0b2b33,#0d5563);color:#fff;border-radius:12px;padding:34px;margin:48px 0 30px}\n.upl-blog .cta h2,.upl-blog .cta .cta-h{color:#fff;margin:0 0 10px;font-size:24px;font-weight:700;line-height:1.3}\n.upl-blog .cta p{color:#c9dee3;margin:0 0 20px;font-size:16px}\n.upl-blog .btn{display:inline-block;background:#e07a1f;color:#fff;text-decoration:none;font-weight:700;padding:13px 26px;border-radius:8px;font-size:15.5px}\n.upl-blog .rel{border-top:1px solid #e8ebed;margin-top:40px;padding-top:26px}\n.upl-blog .rel h4{font-size:13px;letter-spacing:.1em;text-transform:uppercase;color:#6b7280;margin:0 0 14px}\n.upl-blog .rel ul{list-style:none;padding:0;margin:0}\n.upl-blog .rel li{padding:11px 0;border-bottom:1px dashed #e8ebed}\n.upl-blog .rel a{text-decoration:none;font-weight:600;font-size:15.5px}\n@media(max-width:640px){.upl-blog h2{font-size:22px}.upl-blog table{font-size:13px}.upl-blog .cta{padding:24px}}\n\/* \u5355\u7bc7\u9875\u9690\u85cf WhatsApp \u81ea\u52a8\u5c55\u5f00\u7684\u95ee\u5019\u5361\uff0c\u53ea\u4fdd\u7559\u5706\u5f62\u6c14\u6ce1\uff0c\u907f\u514d\u906e\u6321\u4fa7\u680f\u8be2\u76d8\u63d0\u4ea4\u6309\u94ae *\/\nbody.single-post .ht_ctc_chat_greetings_box{display:none !important}\n<\/style>\n<div class=\"upl-blog\">\n<figure>\n<img fetchpriority=\"high\" decoding=\"async\" src=\"https:\/\/uplastech.com\/wp-content\/uploads\/2026\/10\/vacuum-forming-cooling-cycle-time.jpg\" alt=\"Chart showing cooling time against sheet thickness in vacuum forming, with mould temperature as the parameter\" width=\"1536\" height=\"909\"><figcaption>Cooling is 45\u201370% of a thermoforming cycle, and it scales roughly with thickness squared. Everything else in the cycle is detail by comparison.<\/figcaption><\/figure>\n<div class=\"toc\"><\/div>\n<h2 id=\"split\">Where the cycle time actually goes<\/h2>\n<p>People new to thermoforming assume the forming step is the slow part. It is not. Forming takes two to ten seconds. Cooling takes two to four times as long, and it is the only part of the cycle that cannot be shortened by doing it faster.<\/p>\n<table>\n<thead>\n<tr>\n<th>Phase<\/th>\n<th>Share of cycle<\/th>\n<th>Typical time (2 mm sheet)<\/th>\n<th>Can it be shortened?<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Load and clamp<\/td>\n<td>5 \u2013 10%<\/td>\n<td>2 \u2013 4 s<\/td>\n<td>Automatisering<\/td>\n<\/tr>\n<tr>\n<td>Verwarming<\/td>\n<td>15 \u2013 25%<\/td>\n<td>8 \u2013 15 s<\/td>\n<td>Better heaters, closer spacing<\/td>\n<\/tr>\n<tr>\n<td>Forming (vacuum + draw)<\/td>\n<td>3 \u2013 8%<\/td>\n<td>2 \u2013 5 s<\/td>\n<td>Faster vacuum, more vent area<\/td>\n<\/tr>\n<tr>\n<td>Cooling in the tool<\/td>\n<td>50 \u2013 70%<\/td>\n<td>15 \u2013 40 s<\/td>\n<td>Mould temperature, air assist<\/td>\n<\/tr>\n<tr>\n<td>Demould and unload<\/td>\n<td>5 \u2013 10%<\/td>\n<td>2 \u2013 5 s<\/td>\n<td>Automatisering<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 1 \u2014 Cycle breakdown for thin gauge. On heavy gauge the cooling share climbs towards 70%: heat enters the sheet quickly but has to leave it through the thickness.<\/p>\n<p>Cooling is the constraint because the part has to be stiff enough to demould without distorting. That is a material property, and the time to reach it is set by heat transfer \u2014 which follows a relationship you can calculate.<\/p>\n<h2 id=\"physics\">The relationship that governs everything<\/h2>\n<p>Cooling time in thermoforming follows the same square law as injection moulding: it scales with the square of the thickness. Double the sheet thickness and the cooling time roughly quadruples.<\/p>\n<p>For a sheet cooled from both faces, the time to reach a given average temperature is approximately:<\/p>\n<p><strong>t \u2248 (s\u00b2 \/ (\u03c0\u00b2 \u00b7 \u03b1)) \u00b7 ln( (8\/\u03c0\u00b2) \u00b7 (T<sub>sheet<\/sub> \u2212 T<sub>mould<\/sub>) \/ (T<sub>demould<\/sub> \u2212 T<sub>mould<\/sub>) )<\/strong><\/p>\n<p>Where <strong>s<\/strong> is thickness, <strong>\u03b1<\/strong> is thermal diffusivity (about 0.10 mm\u00b2\/s for most plastics), and the temperatures are sheet, mould and demould.<\/p>\n<table>\n<thead>\n<tr>\n<th>Sheet thickness<\/th>\n<th>Theoretical cooling<\/th>\n<th>Realistic with air assist<\/th>\n<th>Realistic without<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>0.5 mm<\/td>\n<td>0.6 s<\/td>\n<td>2 \u2013 3 s<\/td>\n<td>4 \u2013 6 s<\/td>\n<\/tr>\n<tr>\n<td>1.0 mm<\/td>\n<td>1.4 s<\/td>\n<td>4 \u2013 6 s<\/td>\n<td>8 \u2013 12 s<\/td>\n<\/tr>\n<tr>\n<td>2.0 mm<\/td>\n<td>3.6 s<\/td>\n<td>10 \u2013 15 s<\/td>\n<td>20 \u2013 28 s<\/td>\n<\/tr>\n<tr>\n<td>3.0 mm<\/td>\n<td>7.0 s<\/td>\n<td>18 \u2013 26 s<\/td>\n<td>35 \u2013 45 s<\/td>\n<\/tr>\n<tr>\n<td>4.0 mm<\/td>\n<td>12 s<\/td>\n<td>28 \u2013 40 s<\/td>\n<td>55 \u2013 70 s<\/td>\n<\/tr>\n<tr>\n<td>6.0 mm<\/td>\n<td>26 s<\/td>\n<td>55 \u2013 80 s<\/td>\n<td>110 \u2013 140 s<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 2 \u2014 Cooling time by sheet thickness. The gap between theory and practice is the tool interface: air gaps, contact quality and mould temperature control.<\/p>\n<p>The gap between the theoretical and realistic numbers is where the money is. A 2 mm part that calculates at 3.6 s and runs at 25 s has 20 seconds of avoidable time in it \u2014 usually from poor contact between sheet and mould, or from a mould that is running too hot.<\/p>\n<h2 id=\"levers\">The four levers you actually have<\/h2>\n<table>\n<thead>\n<tr>\n<th>Lever<\/th>\n<th>Effect<\/th>\n<th>Practical limit<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Mould temperature<\/td>\n<td>Lower mould = faster cooling<\/td>\n<td>Below about 40 \u00b0C causes chill marks and stress<\/td>\n<\/tr>\n<tr>\n<td>Air assist (blown air on the part)<\/td>\n<td>Adds convective cooling on the free face<\/td>\n<td>Needs a nozzle design that does not distort the part<\/td>\n<\/tr>\n<tr>\n<td>Contact quality<\/td>\n<td>Vacuum holds the sheet against the tool<\/td>\n<td>Limited by part geometry and vent area<\/td>\n<\/tr>\n<tr>\n<td>Demould temperature<\/td>\n<td>Eject sooner, at higher temperature<\/td>\n<td>Part must be stiff enough not to distort<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 3 \u2014 The levers. Air assist is the biggest single gain available on an existing tool, and the cheapest to retrofit.<\/p>\n<p>Air assist works by blowing ambient or chilled air onto the exposed face of the part while it is still on the tool. It roughly doubles the heat transfer coefficient on that face, which cuts cooling time by 25\u201340%. A simple manifold of nozzles is enough; it does not need to be a precision system.<\/p>\n<p>The limit is distortion. Blowing air on a part that is still soft will push it out of shape, particularly on thin walls. The usual approach is to delay the air until the part has set enough to hold its shape, then blow hard.<\/p>\n<h2 id=\"mouldtemp\">Mould temperature: the quality constraint<\/h2>\n<table>\n<thead>\n<tr>\n<th>Mould temperature<\/th>\n<th>Koeltijd<\/th>\n<th>Part quality<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>20 \u2013 30 \u00b0C (cold water)<\/td>\n<td>Fastest<\/td>\n<td>Chill marks, high stress, poor detail, possible distortion<\/td>\n<\/tr>\n<tr>\n<td>40 \u2013 60 \u00b0C<\/td>\n<td>Matig<\/td>\n<td>Good balance for thin gauge<\/td>\n<\/tr>\n<tr>\n<td>70 \u2013 90 \u00b0C<\/td>\n<td>Langzaam<\/td>\n<td>Best surface detail, lowest stress<\/td>\n<\/tr>\n<tr>\n<td>100 \u2013 120 \u00b0C<\/td>\n<td>Slowest<\/td>\n<td>Needed for PC and heavy gauge; texture reproduction<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 4 \u2014 Mould temperature trade-off. Running a cold mould to save cycle time costs surface quality and dimensional stability, which usually costs more downstream.<\/p>\n<p>Cold moulds are the most common false economy in thermoforming. A mould at 25 \u00b0C will cut 30% off the cooling time and produce parts with chill marks, high residual stress and a surface that will not hold a texture. The customer sees the surface; nobody sees the cycle time.<\/p>\n<h2 id=\"heavy\">Heavy gauge: where the cycle becomes a different problem<\/h2>\n<p>Above about 4 mm the cooling time dominates so completely that the process economics change. A 6 mm part might have a 90-second cooling time against a 30-second heating time, which means the machine is idle for two-thirds of the cycle unless it is designed for it.<\/p>\n<table>\n<thead>\n<tr>\n<th>Benadering<\/th>\n<th>How it works<\/th>\n<th>Effect<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Accept the cycle<\/td>\n<td>Run slow, one part at a time<\/td>\n<td>Simple, but low output<\/td>\n<\/tr>\n<tr>\n<td>Multiple tools on a carousel<\/td>\n<td>Several tools cycle through one heating station<\/td>\n<td>Machine runs continuously; capital cost<\/td>\n<\/tr>\n<tr>\n<td>Twin-sheet or shuttle<\/td>\n<td>Two stations alternate<\/td>\n<td>Hides cooling behind heating<\/td>\n<\/tr>\n<tr>\n<td>Cooling fixtures<\/td>\n<td>Part moves to a separate cooling jig<\/td>\n<td>Frees the tool for the next part<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 5 \u2014 Handling long cooling times on heavy gauge. The carousel and the cooling fixture are the two that actually work; the rest just accept the loss.<\/p>\n<p>The cooling fixture is the cheapest of these. The part comes off the tool while still warm and slightly flexible, is transferred to a shaped jig that holds it while it cools, and the tool is free for the next cycle. The jig costs a fraction of a second tool and it can cut effective cycle time by 40%.<\/p>\n<h2 id=\"measuring\">Measuring and improving<\/h2>\n<table>\n<thead>\n<tr>\n<th>Measurement<\/th>\n<th>How<\/th>\n<th>Target<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Part surface temperature at demould<\/td>\n<td>IR gun or contact probe<\/td>\n<td>Below the resin's demould temperature<\/td>\n<\/tr>\n<tr>\n<td>Mould surface temperature<\/td>\n<td>Probe at three points<\/td>\n<td>Uniform within 5 \u00b0C<\/td>\n<\/tr>\n<tr>\n<td>Cooling water \u0394T<\/td>\n<td>Inlet vs outlet<\/td>\n<td>Under 3 \u00b0C<\/td>\n<\/tr>\n<tr>\n<td>Cycle time by phase<\/td>\n<td>Stopwatch or machine log<\/td>\n<td>Cooling under 65% of total<\/td>\n<\/tr>\n<tr>\n<td>Distortion after 24 h<\/td>\n<td>Measure key dimensions<\/td>\n<td>Within tolerance<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 6 \u2014 What to measure to improve the cycle. The water \u0394T is the fastest diagnostic: a high \u0394T means the mould is not transferring heat as designed.<\/p>\n<p>Part temperature at demould is the number that tells you whether the cooling time is right. If the part comes off at 70 \u00b0C when the resin needs to be below 60 \u00b0C, it will distort after demould and the cycle is being pushed too hard. If it comes off at 45 \u00b0C, there is cooling time to give back.<\/p>\n<div class=\"faq\">\n<h3>How much of a vacuum forming cycle is cooling?<\/h3>\n<p>45\u201355% on thin gauge and around 70% on heavy gauge. It is the single largest phase and the only one that cannot be shortened by running faster \u2014 only by better heat transfer or a cooler mould.<\/p>\n<h3>Why does cooling time quadruple when thickness doubles?<\/h3>\n<p>Because heat has to conduct through the thickness, and conduction distance enters the equation squared. It is the same relationship as injection moulding, and it is why thick-gauge parts have such long cycles.<\/p>\n<h3>Does air assist really help?<\/h3>\n<p>Yes, 25\u201340% reduction in cooling time. Blowing air on the free face roughly doubles the heat transfer coefficient there. The constraint is distortion: the air has to be delayed until the part is stiff enough not to be pushed out of shape.<\/p>\n<h3>Can I run a colder mould to speed up the cycle?<\/h3>\n<p>You can, and you will get chill marks, high residual stress, poor surface detail and dimensional instability. Below about 40 \u00b0C the quality loss usually costs more than the cycle time saves. The exception is very thin, non-cosmetic parts.<\/p>\n<h3>How do I know when to demould?<\/h3>\n<p>Measure the part surface temperature. Every resin has a demould temperature below which it is stiff enough \u2014 typically 60\u201370 \u00b0C for PS and ABS, 80\u201390 \u00b0C for PP, 100\u2013120 \u00b0C for PC. If it comes off hotter, it will distort.<\/p>\n<h3>What is the biggest cycle time mistake?<\/h3>\n<p>Setting cooling time by trial and error and then never revisiting it. Most machines run with 20\u201330% more cooling time than necessary because the setting was made once for a difficult part and never adjusted for easier ones.<\/p>\n<h3>Does the sheet thickness tolerance affect cycle time?<\/h3>\n<p>Yes. A sheet at the top of its thickness tolerance needs noticeably more cooling than one at the bottom, and if the cycle is set for the thin end, thick sheets will distort. Setting the cycle for the thickest sheet in the batch is the safe choice.<\/p>\n<h3>Is there a way to cool both sides?<\/h3>\n<p>On female tools with a male plug, the plug can be temperature controlled, which cools the inside. On simple vacuum forming there is only one tool face, which is why air assist exists \u2014 it is the only way to cool the free side.<\/p>\n<\/div>\n<div class=\"cta\">\n<p class=\"cta-h\">Cycle time longer than it should be?<\/p>\n<p>Send us the part drawing, material, gauge and current cycle breakdown. We will calculate what the cooling time should be and tell you whether the limit is the mould temperature, the contact, or the demould temperature.<\/p>\n<p><a class=\"btn\" href=\"https:\/\/uplastech.com\/nl\/vacuumvorming\/\">Talk to a thermoforming engineer<\/a>\n<\/div>\n<div class=\"rel\">\n<h4>Continue reading<\/h4>\n<ul>\n<li><a href=\"https:\/\/uplastech.com\/nl\/vacuum-forming-heater-types\/\">Vacuum Forming Heater Types: Ceramic, Quartz and Calrod<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/nl\/thermoforming-sheet-heating-temperature-window\/\">Sheet Heating in Thermoforming: The Temperature Window<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/nl\/vacuum-forming-tooling-cost\/\">Vacuum Forming Tooling Cost: What Drives the Price<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/nl\/vacuum-forming-mold-design\/\">Vacuum Forming Mold Design: Materials, Draft and Tool Life<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/nl\/thick-gauge-vs-thin-gauge-thermoforming\/\">Thick Gauge vs Thin Gauge Thermoforming<\/a><\/li>\n<\/ul>\n<\/div>\n<\/div>","protected":false},"excerpt":{"rendered":"<p>Cooling is 45-70% of the cycle. How sheet thickness, mould temperature, air assist and demould temperature set the achievable cycle \u2014 and where the shortcuts fail.<\/p>","protected":false},"author":1,"featured_media":7684,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_seopress_titles_title":"Cooling and Cycle Time in Vacuum Forming","_seopress_titles_desc":"Cooling is 45-70% of the cycle. 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