PETG is a popular filament among 3D printing enthusiasts, prized for its combination of strength, flexibility, and ease of use. However, anyone who’s printed with PETG for long enough will be familiar with a frustrating side effect: nozzle buildup and the dreaded “boogers” that stick to prints. These messy blobs can ruin the appearance and structural integrity of your finished objects. If you’re tired of dealing with PETG stringing, oozing, and those unsightly blobs, this guide will help you troubleshoot and avoid nozzle buildup for consistently clean prints.
Understanding Nozzle Buildup and “Boogers”
Nozzle buildup refers to the accumulation of excess, partially melted filament around the hot end of your printer’s nozzle. Over time, this material can drip or get dragged across your print, leaving behind bumps or stringy “boogers.” PETG, in particular, tends to be more prone to these issues than PLA or ABS because of its sticky, slightly gooey nature at printing temperatures. If the filament is too hot, is left sitting on the nozzle, or if your retraction and cooling settings aren’t dialed in, PETG can start to accumulate and cause ongoing problems.
Essential Printer and Filament Settings
Achieving clean PETG prints starts with your printer’s settings. PETG typically prints best at nozzle temperatures between 230°C and 250°C. Printing too hot can lead to excessive oozing and buildup, while printing too cool can cause under-extrusion and poor adhesion. Always consult your filament manufacturer’s recommendations, and consider running a temperature tower to find the sweet spot for your specific setup.
Retraction settings are also crucial. PETG usually requires less retraction than PLA, as too much retraction can lead to clogs or jams. Start with a retraction distance of 1–3mm and a retraction speed of 20–40mm/s, then tweak as needed. Enable your cooling fan after the first few layers—PETG likes a moderate fan setting (30–60%) to help solidify extruded material and prevent stringing. Finally, pay attention to your first layer: a slightly higher first-layer height and proper bed leveling will ensure good adhesion without excess squish, which can contribute to nozzle buildup.
Printer Maintenance for Clean Prints
Routine maintenance is often overlooked but vital for clean printing. Start each print with a clean nozzle. Use a brass brush to gently remove residue from the nozzle’s exterior while it’s hot (but not printing). Periodically perform cold pulls—heating the nozzle, inserting a piece of nylon or cleaning filament, then pulling it out at a lower temperature—to remove stubborn internal debris.
Consider running a few centimeters of cleaning filament through your nozzle every few prints, especially when switching between filament types. If you’re using PETG often, this habit can drastically reduce buildup and improve print consistency.
Slicing Tips to Minimize Buildup
Your slicer’s settings have a huge impact on PETG’s behavior. Adjust the extrusion multiplier (sometimes called “flow rate”) so that your printer isn’t over-extruding. Over-extrusion is a common cause of blobs and buildup. Retraction settings, as mentioned earlier, are vital—experiment with distance and speed to find what works best for your printer and filament.
Enable features like “coasting,” which tells your printer to stop extruding slightly before the end of a travel move. This lets the residual pressure in the nozzle finish the extrusion, reducing blobs. Similarly, look for “wipe” or “comb” features in your slicer; these options keep the nozzle moving within the infill or already-printed areas, minimizing visible stringing and buildup.
Handling PETG Filament for Best Results
PETG’s tendency to absorb moisture from the air can make nozzle buildup worse, as wet filament behaves unpredictably. Store your PETG in a dry, sealed container with desiccant whenever possible. If your filament has been exposed to humidity, dry it in a filament dryer or a low-temperature oven before use. Clean filament means fewer chances for debris to enter your nozzle, reducing buildup even further.
Troubleshooting Common PETG Printing Issues
Even with the best preparation, issues can sometimes appear mid-print. If you notice sudden blobs, try pausing the print, letting the nozzle cool slightly, and carefully removing the buildup with tweezers or a brush. Persistent problems may require you to swap in a new or different-size nozzle; for frequent PETG use, a hardened steel or plated copper nozzle can better resist wear and buildup compared to brass.
If blobs consistently appear at specific print locations, double-check your slicer settings for retraction, coasting, and extrusion. Sometimes, simply updating your slicer or switching to a profile designed for PETG can solve persistent issues.
Summary & Best Practices
Nozzle buildup and “boogers” are common frustrations with PETG, but they’re not inevitable. By dialing in your printer settings, practicing good maintenance, optimizing your slicer configuration, and handling your filament with care, you can dramatically reduce mess and enjoy consistently clean, strong prints. Don’t be afraid to experiment—every printer and spool of PETG is a little different. Keep tweaking your process and you’ll find the perfect combination for smooth, blob-free 3D printing. If you have your own tips or want to troubleshoot a specific issue, share your experience in the comments below—let’s help each other achieve flawless PETG prints!