{"id":197,"date":"2026-07-15T08:49:30","date_gmt":"2026-07-15T08:49:30","guid":{"rendered":"https:\/\/onestepblowmoldingmachine.com\/how-to-clean-and-purge-an-isbm-machine-when-changing-materials\/"},"modified":"2026-07-15T08:49:30","modified_gmt":"2026-07-15T08:49:30","slug":"how-to-clean-and-purge-an-isbm-machine-when-changing-materials","status":"publish","type":"post","link":"https:\/\/onestepblowmoldingmachine.com\/th\/how-to-clean-and-purge-an-isbm-machine-when-changing-materials\/","title":{"rendered":"How to Clean and Purge an ISBM Machine When Changing Materials"},"content":{"rendered":"<nav aria-label=\"\u0e23\u0e48\u0e2d\u0e07\u0e23\u0e2d\u0e22\u0e02\u0e19\u0e21\u0e1b\u0e31\u0e07\" style=\"margin-bottom:18px;font-size:13px;color:#666;\"><a href=\"\/th\/\" style=\"color:#0066cc;text-decoration:none;\">\u0e1a\u0e49\u0e32\u0e19<\/a> &rsaquo; <a href=\"\/th\/products\/isbm-machines\/\" style=\"color:#0066cc;text-decoration:none;\">ISBM Machines<\/a> &rsaquo; <span>How to Clean and Purge an ISBM Machine When Changing Materials<\/span><\/nav>\n<h2 style=\"font-size:28px;color:#1a2e44;margin-bottom:10px;\">How to Clean and Purge an ISBM Machine When Changing Materials<\/h2>\n<p style=\"font-size:16px;line-height:1.8;color:#333;margin-bottom:24px;\">Material changeovers on an ISBM machine carry a risk that is easy to underestimate: residual polymer from the previous material in the barrel, screw, check valve, hot runner manifold, and nozzle channels can contaminate the incoming material for dozens of shots if the purge sequence is not done correctly. The consequences range from minor (colour tinting in the first batch of the new material) to serious (black specks from thermally degraded residue, reduced preform IV from incompatible polymer mixing, or product quality failures in pharmaceutical applications).<\/p>\n<p style=\"font-size:16px;line-height:1.8;color:#333;margin-bottom:24px;\">This guide provides a systematic procedure for material changeover on one-step ISBM machines, covering PET-to-PP, PP-to-PET, PET-to-PETG, colour changes within the same material, and long production shutdown purge procedures. The correct sequence depends on both the outgoing and incoming material \u2014 there is no single universal purge procedure that applies to all combinations.<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/onestepblowmoldingmachine.com\/wp-content\/uploads\/2026\/07\/isbm-machine-5.webp\" alt=\"ISBM machine barrel and screw assembly during material changeover purge procedure\" 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;\">Why Material Changeover Requires a Planned Procedure<\/h2>\n<p style=\"font-size:16px;line-height:1.8;color:#333;margin-bottom:16px;\">Unlike extrusion or blown film processes where the material flows continuously and can self-purge relatively quickly, ISBM has several areas where residual material can accumulate and require active purging:<\/p>\n<ul style=\"padding-left:22px;line-height:2;font-size:15px;color:#333;margin-bottom:20px;\">\n<li><strong>Barrel dead zones:<\/strong> Areas near the barrel wall, behind the check valve, and in the screw flights where melt velocity is low and material can accumulate and degrade over time<\/li>\n<li><strong>Hot runner manifold:<\/strong> The distribution block maintains material in a molten state between shots \u2014 all material in the runner channels must be displaced by the incoming material<\/li>\n<li><strong>Nozzle channels:<\/strong> Each hot runner nozzle retains a small volume of melt; with multiple nozzles, the total retained volume can be 20\u201350% of one shot weight<\/li>\n<li><strong>Check valve assembly:<\/strong> The screw check valve is a low-velocity zone where degraded material can accumulate over long production runs<\/li>\n<\/ul>\n<h2 style=\"font-size:24px;color:#1a2e44;border-left:4px solid #0066cc;padding-left:12px;margin-top:36px;\">General Purge Principles<\/h2>\n<div style=\"display:flex;flex-wrap:wrap;gap:14px;margin-bottom:28px;\">\n<div style=\"flex:1;min-width:200px;background:#f0f7ff;border-radius:8px;padding:16px;border-top:3px solid #0066cc;\">\n    <strong style=\"color:#1a2e44;font-size:14px;\">Temperature First<\/strong><\/p>\n<p style=\"font-size:13px;color:#555;margin-top:8px;line-height:1.7;\">Always set barrel and hot runner temperatures to the incoming material&#8217;s processing range BEFORE beginning the purge. Never purge the incoming material through temperatures optimised for the outgoing material \u2014 incompatible temperature settings degrade both materials and create more contamination.<\/p>\n<\/p><\/div>\n<div style=\"flex:1;min-width:200px;background:#f0f7ff;border-radius:8px;padding:16px;border-top:3px solid #0066cc;\">\n    <strong style=\"color:#1a2e44;font-size:14px;\">Volume-Based Purge<\/strong><\/p>\n<p style=\"font-size:13px;color:#555;margin-top:8px;line-height:1.7;\">Purge by counting shots, not by time. For a standard 1-cavity ISBM machine, a minimum of 10\u201320 purge shots is needed after the incoming material first appears in the gate; the exact number depends on barrel and hot runner volume relative to shot weight.<\/p>\n<\/p><\/div>\n<div style=\"flex:1;min-width:200px;background:#f0f7ff;border-radius:8px;padding:16px;border-top:3px solid #0066cc;\">\n    <strong style=\"color:#1a2e44;font-size:14px;\">Visual Confirmation<\/strong><\/p>\n<p style=\"font-size:13px;color:#555;margin-top:8px;line-height:1.7;\">Always confirm purge completeness visually \u2014 hold a preform to light and look for any colour tinting, streaks, or specks from the previous material. Do not declare changeover complete based on shot count alone; visual inspection of the last 3 purge preforms is mandatory.<\/p>\n<\/p><\/div>\n<div style=\"flex:1;min-width:200px;background:#f0f7ff;border-radius:8px;padding:16px;border-top:3px solid #0066cc;\">\n    <strong style=\"color:#1a2e44;font-size:14px;\">Use Purging Compounds for Incompatible Materials<\/strong><\/p>\n<p style=\"font-size:13px;color:#555;margin-top:8px;line-height:1.7;\">For changeovers between incompatible polymers (PET to PP, PP to PET, any to coloured), a commercial purging compound provides faster and more complete material displacement than the incoming resin alone. Recommended compounds: Asaclean, Purgex, or equivalent ISBM-compatible grade.<\/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;\">Changeover Procedures by Material Combination<\/h2>\n<div style=\"overflow-x:auto;-webkit-overflow-scrolling:touch;margin-bottom:28px;\">\n<table style=\"width:100%;border-collapse:collapse;min-width:540px;\">\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;\">Changeover<\/th>\n<th style=\"color:white;background-color:#1a2e44;padding:12px 14px;text-align:left;font-size:13px;\">Temperature Sequence<\/th>\n<th style=\"color:white;background-color:#1a2e44;padding:12px 14px;text-align:left;font-size:13px;\">Purge Material<\/th>\n<th style=\"color:white;background-color:#1a2e44;padding:12px 14px;text-align:left;font-size:13px;\">Minimum Purge Shots<\/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;\">PET \u2192 PP<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">Reduce barrel to PP range (230\u2013260\u00b0C); reduce hot runner to PP range (230\u2013250\u00b0C) before starting purge<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">Purging compound first (10 shots), then PP resin (10+ shots)<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">20+ shots total; visual clear before production<\/td>\n<\/tr>\n<tr>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;font-weight:600;\">PP \u2192 PET<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">Raise barrel to PET range (255\u2013280\u00b0C); raise hot runner to PET range (270\u2013285\u00b0C) before purge<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">Purging compound first (10 shots), then PET resin (15+ shots)<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">25+ shots total; visual clear before production<\/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;\">PET \u2192 PETG<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">Reduce barrel slightly (PETG 245\u2013270\u00b0C vs PET 255\u2013280\u00b0C); hot runner similar range<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">PETG resin direct (compatible); no compound needed<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">10\u201315 shots; visual clear<\/td>\n<\/tr>\n<tr>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;font-weight:600;\">Colour change (same material)<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">No temperature change required<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">Natural (uncoloured) resin first (10 shots), then new colour<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">15\u201320 shots; visual match to target colour before production<\/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;\">Shutdown purge (any material)<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">At production temperature; purge before cooling down<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">Purging compound (10 shots) to displace production resin before shutdown<\/td>\n<td style=\"padding:9px 14px;border-bottom:1px solid #e0e0e0;font-size:13px;\">10 shots minimum; leave purging compound in barrel for shutdown<\/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;\">Long-Shutdown Procedure (Weekend \/ Extended Downtime)<\/h2>\n<p style=\"font-size:16px;line-height:1.8;color:#333;margin-bottom:16px;\">For shutdowns longer than one shift (weekend, holiday, maintenance stop), additional steps beyond a standard material changeover are required to prevent resin degradation in the barrel and hot runner during the downtime period:<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/onestepblowmoldingmachine.com\/wp-content\/uploads\/2026\/07\/isbm-machine-factory-2.webp\" alt=\"ISBM machine shutdown procedure showing barrel purge and hot runner temperature management for extended downtime\" style=\"width:100%;max-width:100%;height:auto;border-radius:8px;margin-bottom:20px;display:block;\" \/><\/p>\n<ol style=\"padding-left:22px;line-height:2.2;font-size:15px;color:#333;margin-bottom:20px;\">\n<li>At end of last production run, purge barrel with purging compound (10 shots) to displace production resin \u2014 do not leave PET or PP in the barrel at processing temperature during shutdown<\/li>\n<li>Reduce barrel temperatures to standby temperature (PET: 200\u00b0C; PP: 180\u00b0C) \u2014 low enough to prevent resin degradation but high enough for quick restart purge<\/li>\n<li>Reduce hot runner to standby temperature (same as barrel standby)<\/li>\n<li>On restart, bring barrel and hot runner to production temperature; allow 30 minutes for full thermal soak; then purge 5\u201310 shots before beginning production. Inspect first 10 production preforms carefully before releasing to blow station<\/li>\n<li>For extended shutdowns (&gt;72 hours), reduce temperatures to ambient or switch off entirely after thorough purging \u2014 restarting from cold requires a full thermal soak cycle (typically 45\u201360 minutes)<\/li>\n<\/ol>\n<p style=\"font-size:16px;line-height:1.8;color:#333;margin-bottom:24px;\">For machine-specific purge procedures and recommended purging compound grades for your <a href=\"\/th\/products\/isbm-machines\/\" style=\"color:#0066cc;text-decoration:underline;\">ISBM machine model<\/a>, <a href=\"\/th\/contact-us\/\" style=\"color:#0066cc;text-decoration:underline;\">contact our technical support team<\/a>. We can provide a written material changeover SOP tailored to your specific machine and material combination.<\/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;\">Can I purge PET out with PP resin directly without a purging compound?<\/summary>\n<div style=\"padding:14px 16px;font-size:15px;line-height:1.8;color:#444;\">Not recommended. PET and PP are incompatible polymers \u2014 at the processing temperatures where they overlap, a mixed PET\/PP melt forms a degraded material that is difficult to clear from dead zones. PP alone is less effective at displacing PET from the hot runner channels than a commercial purging compound, which is formulated to sweep dead zones more aggressively. Always use a purging compound between incompatible polymer classes.<\/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;\">How do I know the purge is complete for a pharmaceutical production changeover?<\/summary>\n<div style=\"padding:14px 16px;font-size:15px;line-height:1.8;color:#444;\">For pharmaceutical applications, visual inspection alone is insufficient. The changeover validation should include: (1) total purge shot count documented in the batch record; (2) visual inspection of last 5 purge preforms under white light and UV if applicable; (3) measurement of preform weight within tolerance band (confirms consistent shot weight from the new material); (4) for colour changeovers, spectrophotometric measurement of a preform sample against the previous colour standard to confirm absence of contamination. For new material or colour combinations, conduct a worst-case validation purge study to establish the minimum number of shots needed to pass contamination specifications.<\/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 should I do if I see black specks during purging?<\/summary>\n<div style=\"padding:14px 16px;font-size:15px;line-height:1.8;color:#444;\">Black specks during purging indicate thermally degraded resin being displaced from dead zones. Continue purging \u2014 do not stop prematurely. If specks persist beyond 30 shots, the hot runner manifold or a specific nozzle channel may have a degraded material deposit that requires manual cleaning (hot runner disassembly and mechanical cleaning of runner channels). Persistent black specks also suggest that the outgoing material was exposed to excessive temperature or residence time in the previous production run \u2014 investigate processing conditions.<\/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;\">Need a Material Changeover SOP for Your ISBM Machine?<\/h3>\n<p style=\"color:#cde;font-size:15px;margin-bottom:20px;line-height:1.7;\">We can provide a machine-specific changeover procedure document for your material combination \u2014 including purge temperature profiles, shot counts, and confirmation criteria.<\/p>\n<p>  <a href=\"\/th\/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 a Changeover SOP<\/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 Clean and Purge an ISBM Machine When Changing Materials\",\n            \"description\": \"Step-by-step guide for ISBM machine material changeover including PET to PP, PP to PET, colour change, and shutdown purge procedures with temperature sequences and purge shot counts.\",\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\": \"Can I purge PET out with PP resin directly without a purging compound?\",\n                    \"acceptedAnswer\": {\n                        \"@type\": \"Answer\",\n                        \"text\": \"Not recommended. 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