{"id":183,"date":"2026-07-15T07:55:32","date_gmt":"2026-07-15T07:55:32","guid":{"rendered":"https:\/\/onestepblowmoldingmachine.com\/how-to-optimise-stretch-ratio-and-blow-pressure-on-an-isbm-machine\/"},"modified":"2026-07-15T07:55:32","modified_gmt":"2026-07-15T07:55:32","slug":"how-to-optimise-stretch-ratio-and-blow-pressure-on-an-isbm-machine","status":"publish","type":"post","link":"https:\/\/onestepblowmoldingmachine.com\/zh\/how-to-optimise-stretch-ratio-and-blow-pressure-on-an-isbm-machine\/","title":{"rendered":"How to Optimise Stretch Ratio and Blow Pressure on an ISBM Machine?"},"content":{"rendered":"<nav aria-label=\"\u9762\u5305\u5c51\" style=\"margin-bottom:18px;font-size:13px;color:#666;\"><a href=\"\/zh\/\" style=\"color:#0066cc;text-decoration:none;\">\u5bb6<\/a> &rsaquo; <a href=\"\/zh\/products\/isbm-machines\/\" style=\"color:#0066cc;text-decoration:none;\">ISBM\u673a\u5668<\/a> &rsaquo; <span>How to Optimise Stretch Ratio and Blow Pressure on an ISBM Machine<\/span><\/nav>\n<h2 style=\"font-size:28px;color:#1a2e44;margin-bottom:10px;\">How to Optimise Stretch Ratio and Blow Pressure on an ISBM Machine?<\/h2>\n<p style=\"font-size:16px;line-height:1.8;color:#333;margin-bottom:24px;\">Stretch ratio and blow pressure are the two most directly influential process parameters in stretch blow molding. They determine the degree of biaxial orientation achieved in the bottle wall, which in turn controls wall thickness distribution, mechanical strength, gas barrier performance, optical clarity, and resistance to top-load collapse. Getting these parameters right \u2014 and maintaining them consistently \u2014 is the difference between a process that reliably produces premium containers and one that generates chronic quality defects and excessive scrap.<\/p>\n<p style=\"font-size:16px;line-height:1.8;color:#333;margin-bottom:24px;\">This article is written for process engineers and technical operators who already understand the basics of ISBM and want to systematically optimise their stretch ratio and blow pressure settings to achieve target bottle specifications. Both the theory and the practical trial methodology are covered in depth.<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/onestepblowmoldingmachine.com\/wp-content\/uploads\/2026\/07\/one-step-Injection-stretch-blow-machine-molds-4.webp\" alt=\"ISBM machine blow mold showing stretch rod and blow nozzle configuration for stretch ratio and pressure optimisation\" style=\"width:100%;max-width:100%;height:auto;border-radius:8px;margin-bottom:28px;display:block;\" \/><\/p>\n<h2 style=\"font-size:24px;color:#1a2e44;border-left:4px solid #0066cc;padding-left:12px;margin-top:36px;\">Understanding Stretch Ratio: The Foundation<\/h2>\n<p style=\"font-size:16px;line-height:1.8;color:#333;margin-bottom:16px;\">Stretch ratio describes the degree of deformation the preform undergoes during the stretch-blow process. It is expressed in two directions and their product:<\/p>\n<div style=\"overflow-x:auto;-webkit-overflow-scrolling:touch;margin-bottom:28px;\">\n<table style=\"width:100%;border-collapse:collapse;min-width:500px;\">\n<thead>\n<tr style=\"background-color:#1a2e44;\">\n<th style=\"color:white;background-color:#1a2e44;padding:12px 14px;text-align:left;font-size:14px;\">Ratio<\/th>\n<th style=\"color:white;background-color:#1a2e44;padding:12px 14px;text-align:left;font-size:14px;\">Formula<\/th>\n<th style=\"color:white;background-color:#1a2e44;padding:12px 14px;text-align:left;font-size:14px;\">Typical Range (PET)<\/th>\n<th style=\"color:white;background-color:#1a2e44;padding:12px 14px;text-align:left;font-size:14px;\">Effect on Bottle<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr style=\"background-color:#f8f9fa;\">\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;font-weight:600;\">Axial Stretch Ratio (ASR)<\/td>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">Bottle body length \u00f7 Preform body length<\/td>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">2.5\u20133.5\u00d7<\/td>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">Controls orientation in height direction; wall thickness in sidewall<\/td>\n<\/tr>\n<tr>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;font-weight:600;\">Hoop Stretch Ratio (HSR)<\/td>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">Bottle body diameter \u00f7 Preform body diameter<\/td>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">3.0\u20134.0\u00d7<\/td>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">Controls circumferential orientation; hoop strength; barrier<\/td>\n<\/tr>\n<tr style=\"background-color:#f8f9fa;\">\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;font-weight:600;\">Biaxial Stretch Ratio (BSR)<\/td>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">ASR \u00d7 HSR<\/td>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">8\u201312\u00d7<\/td>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">Overall orientation intensity; strain-induced crystallinity in PET; barrier performance<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p style=\"font-size:16px;line-height:1.8;color:#333;margin-bottom:16px;\">The ASR is primarily determined at the preform design stage \u2014 the preform body length relative to the target bottle body length sets the axial stretch ratio before the machine is even started. However, the effective ASR can be adjusted within limits by modifying the stretch rod stroke on the machine, or by changing the preform design. The HSR is similarly set by the relationship between preform and bottle body diameters. This means that stretch ratio optimisation begins with preform design, not just with machine parameter adjustment.<\/p>\n<div style=\"background-color:#e8f4fd;border-radius:8px;padding:20px 22px;margin-bottom:24px;\">\n  <strong style=\"color:#1a2e44;\">Key Insight:<\/strong><\/p>\n<p style=\"font-size:14px;color:#333;margin-top:8px;line-height:1.7;\">If the preform design gives ASR 2.8\u00d7 and HSR 3.5\u00d7, the BSR is 9.8\u00d7 \u2014 within the PET target range. If your bottle is showing poor barrier or low top-load strength despite correct conditioning temperatures, the first thing to check is whether the preform dimensions are giving the target stretch ratios, not just the blow parameters.<\/p>\n<\/div>\n<h2 style=\"font-size:24px;color:#1a2e44;border-left:4px solid #0066cc;padding-left:12px;margin-top:36px;\">What Happens When Stretch Ratio is Wrong<\/h2>\n<div style=\"display:flex;flex-wrap:wrap;gap:14px;margin-bottom:28px;\">\n<div style=\"flex:1;min-width:220px;background:#f8d7da;border-left:4px solid #dc3545;border-radius:4px;padding:16px;\">\n    <strong style=\"color:#dc3545;font-size:14px;\">BSR Too Low (Under-Oriented)<\/strong><\/p>\n<ul style=\"margin:10px 0 0 0;padding-left:16px;font-size:13px;line-height:1.9;color:#444;\">\n<li>Poor top-load crush strength \u2014 bottles fail in pallet stack<\/li>\n<li>Higher oxygen and CO2 permeability \u2014 shorter product shelf life<\/li>\n<li>Greater creep under sustained pressure load<\/li>\n<li>Heavier base material (thick gate area not stretched away)<\/li>\n<li>Lower drop impact resistance \u2014 shatters rather than deforms<\/li>\n<\/ul><\/div>\n<div style=\"flex:1;min-width:220px;background:#d4edda;border-left:4px solid #28a745;border-radius:4px;padding:16px;\">\n    <strong style=\"color:#28a745;font-size:14px;\">BSR in Target Range (Optimally Oriented)<\/strong><\/p>\n<ul style=\"margin:10px 0 0 0;padding-left:16px;font-size:13px;line-height:1.9;color:#444;\">\n<li>Maximum tensile strength per unit weight<\/li>\n<li>Minimum gas permeability for the material<\/li>\n<li>Crystal clarity with minimal haze<\/li>\n<li>Uniform wall thickness distribution<\/li>\n<li>Excellent drop impact resistance<\/li>\n<\/ul><\/div>\n<div style=\"flex:1;min-width:220px;background:#f8d7da;border-left:4px solid #dc3545;border-radius:4px;padding:16px;\">\n    <strong style=\"color:#dc3545;font-size:14px;\">BSR Too High (Over-Oriented)<\/strong><\/p>\n<ul style=\"margin:10px 0 0 0;padding-left:16px;font-size:13px;line-height:1.9;color:#444;\">\n<li>Stress whitening and crazing at gate area<\/li>\n<li>Very thin base at gate \u2014 risk of field failure under abuse conditions<\/li>\n<li>Fibrillation \u2014 wall splits parallel to stretch direction on impact<\/li>\n<li>Gate puncture or tearing during stretch-blow<\/li>\n<\/ul><\/div>\n<\/div>\n<h2 style=\"font-size:24px;color:#1a2e44;border-left:4px solid #0066cc;padding-left:12px;margin-top:36px;\">Blow Pressure \u2014 Understanding the Role of Pre-Blow and Main Blow<\/h2>\n<p style=\"font-size:16px;line-height:1.8;color:#333;margin-bottom:16px;\">Blow pressure in ISBM is delivered in two sequential stages, each with a distinct mechanical function:<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/onestepblowmoldingmachine.com\/wp-content\/uploads\/2026\/07\/blowing-nozzle.webp\" alt=\"ISBM machine blow nozzle assembly showing pre-blow and main blow air circuit connections\" style=\"width:100%;max-width:100%;height:auto;border-radius:8px;margin-bottom:20px;display:block;\" \/><\/p>\n<div style=\"display:flex;flex-wrap:wrap;gap:16px;margin-bottom:24px;\">\n<div style=\"flex:1;min-width:240px;border:2px solid #0066cc;border-radius:8px;padding:18px;\">\n<h3 style=\"color:#0066cc;font-size:16px;margin-bottom:8px;\">Stage 1 \u2014 Pre-Blow (Low Pressure)<\/h3>\n<p style=\"font-size:14px;color:#444;line-height:1.8;\"><strong>Pressure range:<\/strong> 4\u20138 bar<br \/><strong>Timing:<\/strong> Introduced simultaneously with or just before stretch rod descent<br \/><strong>Function:<\/strong> Contacts the inner preform wall, creating a pressure cushion that prevents the stretch rod tip from puncturing the gate area. Also begins the controlled radial expansion of the preform body against the blow mold before high pressure is applied. Pre-blow pressure must be precisely timed relative to rod movement \u2014 too early inflates the preform before the rod reaches the gate; too late allows the rod to contact the gate without air cushion.<\/p>\n<\/p><\/div>\n<div style=\"flex:1;min-width:240px;border:2px solid #0066cc;border-radius:8px;padding:18px;\">\n<h3 style=\"color:#0066cc;font-size:16px;margin-bottom:8px;\">Stage 2 \u2014 Main Blow (High Pressure)<\/h3>\n<p style=\"font-size:14px;color:#444;line-height:1.8;\"><strong>Pressure range:<\/strong> 15\u201340 bar<br \/><strong>Timing:<\/strong> Applied after stretch rod has reached full stroke (or near-full); often with a brief overlap with pre-blow switch<br \/><strong>Function:<\/strong> Provides the force to fully expand the preform outward against all mold surfaces, including fine panel details, shoulders, and base profile. Must be high enough to fully fill the mold cavity \u2014 insufficient pressure leaves flat spots and incomplete shoulder radius. Must be held for sufficient time (typically 0.3\u20131.5 seconds) for the walls to contact the chilled mold and begin cooling before exhausting.<\/p>\n<\/p><\/div>\n<\/div>\n<h2 style=\"font-size:24px;color:#1a2e44;border-left:4px solid #0066cc;padding-left:12px;margin-top:36px;\">Step-by-Step Optimisation Protocol<\/h2>\n<p style=\"font-size:16px;line-height:1.8;color:#333;margin-bottom:16px;\">Follow this systematic sequence when optimising stretch ratio and blow pressure for a new bottle program or after a fault recovery:<\/p>\n<div style=\"overflow-x:auto;-webkit-overflow-scrolling:touch;margin-bottom:28px;\">\n<table style=\"width:100%;border-collapse:collapse;min-width:500px;\">\n<thead>\n<tr style=\"background-color:#1a2e44;\">\n<th style=\"color:white;background-color:#1a2e44;padding:12px 14px;text-align:left;font-size:13px;\">Step<\/th>\n<th style=\"color:white;background-color:#1a2e44;padding:12px 14px;text-align:left;font-size:13px;\">Action<\/th>\n<th style=\"color:white;background-color:#1a2e44;padding:12px 14px;text-align:left;font-size:13px;\">What to Measure<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr style=\"background-color:#f8f9fa;\">\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;font-weight:600;\">1<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">Calculate target ASR, HSR, BSR from preform and bottle drawings. Verify rod stroke setting achieves target ASR.<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">Rod stroke setting (mm); preform and bottle dimension drawings<\/td>\n<\/tr>\n<tr>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;font-weight:600;\">2<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">Set conditioning temperature to mid-range of material window (e.g. 95\u00b0C for PET). Allow machine to reach thermal equilibrium (10+ cycles minimum).<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">IR gun reading at multiple preform body points<\/td>\n<\/tr>\n<tr style=\"background-color:#f8f9fa;\">\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;font-weight:600;\">3<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">Set pre-blow to 5 bar. Set main blow to 20 bar. Blow first articles. Inspect for gate puncture, incomplete fill, and overall shape.<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">Visual inspection; bottle height; overall weight<\/td>\n<\/tr>\n<tr>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;font-weight:600;\">4<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">If incomplete panel fill: increase main blow in 2-bar increments, blowing 3 cycles per setting, until full panel definition achieved.<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">Panel definition (visual); sidewall flat-spot absence<\/td>\n<\/tr>\n<tr style=\"background-color:#f8f9fa;\">\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;font-weight:600;\">5<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">Measure wall thickness at 5 points on cross-section. Compare to target wall distribution. Identify heaviest zone.<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">Ultrasonic wall thickness gauge or physical cut-section measurement<\/td>\n<\/tr>\n<tr>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;font-weight:600;\">6<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">If base is too heavy (insufficient ASR): increase rod stroke by 2mm increments. If sidewall is too heavy (insufficient HSR): adjust conditioning temperature profile or preform design.<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">Wall thickness after each adjustment; gate condition<\/td>\n<\/tr>\n<tr style=\"background-color:#f8f9fa;\">\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;font-weight:600;\">7<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">Once wall distribution is acceptable, perform functional tests: top-load, drop test, pressure hold (CSD only).<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">Top-load force (N); drop height; CO2 pressure hold time<\/td>\n<\/tr>\n<tr>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;font-weight:600;\">8<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">If top-load fails: confirm BSR is in target range. If BSR is correct but top-load fails, increase conditioning temperature by 2\u00b0C to improve orientation mobility.<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">Top-load force before and after conditioning temperature change<\/td>\n<\/tr>\n<tr style=\"background-color:#f8f9fa;\">\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;font-weight:600;\">9<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">Record all confirmed optimal parameters in a Master Process Record. Validate stability over 100 consecutive bottles before releasing to production.<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">Sample every 10 bottles: weight, visual, top-load spot-check<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<h2 style=\"font-size:24px;color:#1a2e44;border-left:4px solid #0066cc;padding-left:12px;margin-top:36px;\">Material-Specific Stretch Ratio and Blow Pressure Targets<\/h2>\n<div style=\"overflow-x:auto;-webkit-overflow-scrolling:touch;margin-bottom:28px;\">\n<table style=\"width:100%;border-collapse:collapse;min-width:560px;\">\n<thead>\n<tr style=\"background-color:#1a2e44;\">\n<th style=\"color:white;background-color:#1a2e44;padding:12px 14px;text-align:left;font-size:14px;\">\u8303\u56f4<\/th>\n<th style=\"color:white;background-color:#1a2e44;padding:12px 14px;text-align:left;font-size:14px;\">PET<\/th>\n<th style=\"color:white;background-color:#1a2e44;padding:12px 14px;text-align:left;font-size:14px;\">PP (rCopolymer)<\/th>\n<th style=\"color:white;background-color:#1a2e44;padding:12px 14px;text-align:left;font-size:14px;\">PETG<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr style=\"background-color:#f8f9fa;\">\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">Target ASR<\/td>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">2.5\u20133.5\u00d7<\/td>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">2.0\u20133.0\u00d7<\/td>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">2.0\u20133.0\u00d7<\/td>\n<\/tr>\n<tr>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">Target HSR<\/td>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">3.0\u20134.0\u00d7<\/td>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">2.5\u20133.5\u00d7<\/td>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">2.5\u20134.0\u00d7<\/td>\n<\/tr>\n<tr style=\"background-color:#f8f9fa;\">\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">Target BSR<\/td>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">8\u201312\u00d7<\/td>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">5\u20139\u00d7<\/td>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">6\u201310\u00d7<\/td>\n<\/tr>\n<tr>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">Pre-blow pressure<\/td>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">4\u20138 bar<\/td>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">5\u201310 bar<\/td>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">4\u20138 bar<\/td>\n<\/tr>\n<tr style=\"background-color:#f8f9fa;\">\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">Main blow pressure<\/td>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">15\u201335 bar<\/td>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">20\u201340 bar<\/td>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">15\u201330 bar<\/td>\n<\/tr>\n<tr>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">Main blow hold time<\/td>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">0.5\u20131.5 s<\/td>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">0.5\u20132.0 s<\/td>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">0.5\u20131.5 s<\/td>\n<\/tr>\n<tr style=\"background-color:#f8f9fa;\">\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">Preform conditioning temp<\/td>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">90\u2013105\u00b0C<\/td>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">125\u2013140\u00b0C<\/td>\n<td style=\"padding:10px 14px;border-bottom:1px solid #e0e0e0;font-size:14px;\">90\u2013100\u00b0C<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<h2 style=\"font-size:24px;color:#1a2e44;border-left:4px solid #0066cc;padding-left:12px;margin-top:36px;\">Common Optimisation Mistakes and How to Avoid Them<\/h2>\n<p><img decoding=\"async\" src=\"https:\/\/onestepblowmoldingmachine.com\/wp-content\/uploads\/2026\/07\/one-step-Injection-stretch-blow-machine-molds-5.webp\" alt=\"ISBM machine blow mold cross section showing wall thickness distribution affected by stretch ratio optimisation\" style=\"width:100%;max-width:100%;height:auto;border-radius:8px;margin-bottom:20px;display:block;\" \/><\/p>\n<div style=\"display:flex;flex-wrap:wrap;gap:14px;margin-bottom:28px;\">\n<div style=\"flex:1;min-width:220px;border:1px solid #dde4ec;border-radius:8px;padding:16px;\">\n    <strong style=\"color:#dc3545;font-size:14px;\">Mistake 1: Changing multiple parameters simultaneously<\/strong><\/p>\n<p style=\"font-size:13px;color:#555;margin-top:8px;line-height:1.7;\">When troubleshooting wall thickness problems, changing pre-blow pressure, main blow pressure, and conditioning temperature all at once makes it impossible to identify which variable caused any observed change. Change one parameter per trial run; document each result before moving to the next change.<\/p>\n<\/p><\/div>\n<div style=\"flex:1;min-width:220px;border:1px solid #dde4ec;border-radius:8px;padding:16px;\">\n    <strong style=\"color:#dc3545;font-size:14px;\">Mistake 2: Measuring only visual quality, not dimensional quality<\/strong><\/p>\n<p style=\"font-size:13px;color:#555;margin-top:8px;line-height:1.7;\">A bottle can look acceptable visually but have non-uniform wall thickness that will cause top-load failure in distribution. Always measure wall thickness during optimisation, not just visual assessment. At minimum, cut 3 representative bottles for physical wall measurement.<\/p>\n<\/p><\/div>\n<div style=\"flex:1;min-width:220px;border:1px solid #dde4ec;border-radius:8px;padding:16px;\">\n    <strong style=\"color:#dc3545;font-size:14px;\">Mistake 3: Ignoring pre-blow timing<\/strong><\/p>\n<p style=\"font-size:13px;color:#555;margin-top:8px;line-height:1.7;\">Pre-blow pressure value and pre-blow initiation timing are independent variables. An incorrect pre-blow timing (too late) will cause gate marks even if the pressure is correct. Always optimise pre-blow timing and pressure together, not just pressure in isolation.<\/p>\n<\/p><\/div>\n<div style=\"flex:1;min-width:220px;border:1px solid #dde4ec;border-radius:8px;padding:16px;\">\n    <strong style=\"color:#dc3545;font-size:14px;\">Mistake 4: Optimising at startup temperature, not at thermal equilibrium<\/strong><\/p>\n<p style=\"font-size:13px;color:#555;margin-top:8px;line-height:1.7;\">Parameters that produce acceptable bottles at cold startup may produce defects after 30\u201360 minutes when the machine reaches full thermal equilibrium. Always wait for thermal stabilisation (typically 20+ cycles after reaching setpoint) before locking parameters.<\/p>\n<\/p><\/div>\n<\/div>\n<p style=\"font-size:16px;line-height:1.8;color:#333;margin-bottom:24px;\">For process-specific guidance on stretch ratio and blow pressure optimisation for your bottle and material, or to request a remote process review, <a href=\"\/zh\/contact-us\/\" style=\"color:#0066cc;text-decoration:underline;\">contact our process engineering team<\/a>. We offer structured process optimisation support for all <a href=\"\/zh\/products\/isbm-machines\/\" style=\"color:#0066cc;text-decoration:underline;\">ISBM machines in our range<\/a>.<\/p>\n<h2 style=\"font-size:24px;color:#1a2e44;border-left:4px solid #0066cc;padding-left:12px;margin-top:36px;\">Frequently Asked Questions<\/h2>\n<details style=\"border:1px solid #dde4ec;border-radius:6px;margin-bottom:10px;\">\n<summary style=\"padding:14px 16px;cursor:pointer;font-weight:600;font-size:15px;color:#1a2e44;background:#f5f8fc;border-radius:6px;list-style:none;\">How do I know if I am achieving the target BSR without specialised lab equipment?<\/summary>\n<div style=\"padding:14px 16px;font-size:15px;line-height:1.8;color:#444;\">Calculate BSR from preform and bottle dimensions \u2014 this tells you the theoretical BSR the process is targeting. Confirm it is being achieved by measuring wall thickness: if the wall distribution matches the inverse of the stretch ratio map (thinner where stretch is higher), the material is orienting correctly. A functional proxy test is the top-load crush test \u2014 achieving spec top-load is a reliable indicator of adequate BSR in the critical sidewall zone.<\/div>\n<\/details>\n<details style=\"border:1px solid #dde4ec;border-radius:6px;margin-bottom:10px;\">\n<summary style=\"padding:14px 16px;cursor:pointer;font-weight:600;font-size:15px;color:#1a2e44;background:#f5f8fc;border-radius:6px;list-style:none;\">Can I increase BSR by raising blow pressure alone?<\/summary>\n<div style=\"padding:14px 16px;font-size:15px;line-height:1.8;color:#444;\">No \u2014 blow pressure alone cannot increase BSR. BSR is determined by the geometric relationship between preform and bottle dimensions, and by the axial rod stroke. Increasing blow pressure beyond what is needed to fill the mold cavity does not increase stretch ratio; it only risks mold flash and excessive stress on the mold parting line. If BSR is insufficient, the preform design (dimensions) or the rod stroke must be adjusted.<\/div>\n<\/details>\n<details style=\"border:1px solid #dde4ec;border-radius:6px;margin-bottom:10px;\">\n<summary style=\"padding:14px 16px;cursor:pointer;font-weight:600;font-size:15px;color:#1a2e44;background:#f5f8fc;border-radius:6px;list-style:none;\">What is the minimum blow pressure I need to fully form a standard 500ml PET bottle?<\/summary>\n<div style=\"padding:14px 16px;font-size:15px;line-height:1.8;color:#444;\">For a standard 500ml round PET bottle with simple panel geometry, main blow pressure of 18\u201322 bar is typically sufficient for complete panel fill when the preform temperature is correctly conditioned. Complex panels (facets, sharp edges, deep embossing) and large-diameter bottles may require 25\u201332 bar. The practical test is visual panel definition \u2014 blow at the minimum pressure that gives sharp, fully-formed panels rather than defaulting to maximum available pressure.<\/div>\n<\/details>\n<div style=\"background-color:#1a2e44;color:white;border-radius:10px;padding:28px 24px;margin-top:40px;text-align:center;\">\n<h3 style=\"color:white;font-size:22px;margin-bottom:12px;\">Get Expert Guidance on Stretch Ratio and Blow Pressure Optimisation<\/h3>\n<p style=\"color:#cde;font-size:15px;margin-bottom:20px;line-height:1.7;\">Describe your bottle, material, and current quality issues \u2014 our process engineers can diagnose stretch and pressure parameter problems remotely in most cases.<\/p>\n<p>  <a href=\"\/zh\/contact-us\/\" style=\"background-color:#f0a500;color:#1a2e44;padding:13px 32px;border-radius:6px;text-decoration:none;font-weight:700;font-size:16px;display:inline-block;\">Request Process Support<\/a>\n<\/div>\n<p><script type=\"application\/ld+json\">{\n    \"@context\": \"https:\\\/\\\/schema.org\",\n    \"@graph\": [\n        {\n            \"@type\": \"Article\",\n            \"headline\": \"How to Optimise Stretch Ratio and Blow Pressure on an ISBM Machine?\",\n            \"description\": \"Technical guide for process engineers on optimising axial stretch ratio, hoop stretch ratio, biaxial stretch ratio, pre-blow and main blow pressure on ISBM machines for PET, PP and PETG bottles.\",\n            \"author\": {\n                \"@type\": \"Organization\",\n                \"name\": \"Ever-Power ISBM Machines\"\n            }\n        },\n        {\n            \"@type\": \"FAQPage\",\n            \"mainEntity\": [\n                {\n                    \"@type\": \"Question\",\n                    \"name\": \"How do I know if I am achieving the target BSR without specialised lab equipment?\",\n                    \"acceptedAnswer\": {\n                        \"@type\": \"Answer\",\n                        \"text\": \"Calculate BSR from preform and bottle dimensions. 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Stretch ratio and blow pressure are the two most directly influential process parameters in stretch blow molding. They determine the degree of biaxial orientation achieved in [&hellip;]<\/p>","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_et_pb_use_builder":"","_et_pb_old_content":"","_et_gb_content_width":"","footnotes":""},"categories":[125],"tags":[190,191,192,189,188],"class_list":["post-183","post","type-post","status-publish","format-standard","hentry","category-isbm-machine-blogs","tag-axial-stretch-ratio-blow-molding","tag-biaxial-stretch-ratio-pet","tag-blow-molding-process-parameters","tag-blow-pressure-optimisation","tag-isbm-stretch-ratio-optimisation"],"_links":{"self":[{"href":"https:\/\/onestepblowmoldingmachine.com\/zh\/wp-json\/wp\/v2\/posts\/183","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/onestepblowmoldingmachine.com\/zh\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/onestepblowmoldingmachine.com\/zh\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/onestepblowmoldingmachine.com\/zh\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/onestepblowmoldingmachine.com\/zh\/wp-json\/wp\/v2\/comments?post=183"}],"version-history":[{"count":0,"href":"https:\/\/onestepblowmoldingmachine.com\/zh\/wp-json\/wp\/v2\/posts\/183\/revisions"}],"wp:attachment":[{"href":"https:\/\/onestepblowmoldingmachine.com\/zh\/wp-json\/wp\/v2\/media?parent=183"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/onestepblowmoldingmachine.com\/zh\/wp-json\/wp\/v2\/categories?post=183"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/onestepblowmoldingmachine.com\/zh\/wp-json\/wp\/v2\/tags?post=183"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}