PETG Stringing on Logos but Not Cylinders: 7 Expert Fixes for Clean Prints
Have you ever felt like your 3D printer is gaslighting you? You spend three hours printing a perfectly smooth, glass-like PETG cylinder—not a single hair, not a blob, just pure additive manufacturing bliss. Then, you decide to print a simple logo or a bit of text on a flat surface, and suddenly your build plate looks like a spider took a hit of espresso and went on a frantic spinning spree. It’s frustrating, it’s messy, and quite frankly, it’s enough to make you want to switch back to PLA and never look back.
I’ve been there. I’ve stared at my Voron and my Prusa, pleading with the "PETG gods" to explain why a circle is fine but the letter 'E' is a disaster. The truth is, PETG (Polyethylene Terephthalate Glycol) is a sticky, hygroscopic beast that behaves differently depending on the geometry of your toolpath. It’s not just about temperature; it’s about how the nozzle moves when it thinks no one is watching. In this guide, we are going to dive deep into the "why" and the "how-to-fix" of PETG stringing on complex geometries versus simple shapes. Pull up a chair, grab a coffee, and let's get those prints looking professional.
1. The Geometry Paradox: Why PETG Stringing Varies by Shape
When you print a cylinder, your printer is essentially doing one long, continuous extrude. The nozzle moves in a rhythmic, circular path. There are very few "starts" and "stops." Since the pressure in the nozzle remains relatively constant, there's no opportunity for the molten PETG to ooze out during a travel move—because there are no travel moves.
Now, think about a logo or text. Each letter is a series of tiny islands. To print the word "TECH," your printer has to:
- Start extruding the 'T'.
- Stop extruding, retract, and travel to the next part of the 'T'.
- Stop again, travel to the 'E'.
- Repeat this hundreds of times per layer.
Every time the nozzle stops extruding and moves (a "travel move"), the internal pressure in the hotend wants to push that sticky PETG out. Because PETG is more viscous and "syrupy" than PLA, it doesn't snap off cleanly. It stretches. That stretch is the string you see.
2. Why PETG Loves to String on Logos: The "Small Island" Effect
The PRIMARY_KEYWORD of our struggle here is PETG stringing. The reason it shows up specifically on logos is due to the "Small Island Effect." When the nozzle finishes a small detail—like the dot on an 'i'—it immediately jumps to the next point.
Unlike a cylinder where the heat is distributed evenly as the nozzle moves, logos involve the nozzle hovering over small areas for short bursts. This keeps the plastic very hot and very fluid. When the travel move happens, the "tail" of the plastic is still molten enough to be pulled along like melted mozzarella on a pizza slice.
3. Retraction Mastery: The Heart of the Problem
If you want to kill the stringing on your logos, you have to look at your retraction settings. Retraction is the process of the extruder motor pulling the filament back slightly to relieve pressure in the nozzle.
Retraction Distance vs. Retraction Speed
For PETG, more is not always better. If you retract too far, you suck air into the nozzle, causing clogs or "blobs" when the extrusion restarts.
| Printer Type | Recommended Distance | Recommended Speed |
|---|---|---|
| Direct Drive | 0.5mm - 1.5mm | 25 - 45 mm/s |
| Bowden Tube | 3.0mm - 6.0mm | 30 - 50 mm/s |
The Secret Sauce: For logos, try increasing your retraction speed rather than the distance. A quick "snap" back of the filament is often more effective at breaking the surface tension of the molten PETG than a long, slow pull.
4. Travel Speed and Acceleration: The Silent Killers
When printing text, the time the nozzle spends traveling between letters is the "danger zone" for stringing. The slower the travel move, the more time gravity has to pull a string out of the nozzle.
Solution: Crank up your Travel Speed. I typically set my travel speed to at least 150mm/s, often 200mm/s if the printer can handle it. You want the nozzle to "teleport" between the letters. This fast motion helps break the string before it can even form.
Why Cylinders Hide This:
In a cylinder, there are no long-distance travels across open air. The nozzle is always "on the job." In a logo, the nozzle is constantly commuting. If your commute is slow, you're going to leak filament.
5. The Z-Hop Dilemma: Friend or Foe?
Z-hop is a setting where the nozzle lifts up slightly before a travel move. On paper, it sounds great—it prevents the nozzle from hitting the print. However, for PETG, Z-hop can actually make stringing worse.
When the nozzle lifts, it creates a vertical "tail" of plastic. As the nozzle then moves horizontally, that tail gets dragged, creating a beautiful, messy cobweb.
6. Wet Filament and Cooling Realities
If you are doing everything right in your slicer and still seeing PETG stringing, your filament is probably wet. PETG is like a sponge; it absorbs moisture from the air. When that moisture hits the 240°C heater block, it turns into steam, creating internal pressure that forces filament out of the nozzle—even during a retraction!
- Dry your PETG: 65°C for at least 6 hours.
- Cooling Fan: For logos and text, you actually need more cooling than for a structural cylinder. While PETG loves low cooling for strength, small details need a blast of air (30-50%) to solidify the plastic before the nozzle moves away.
7. Slicer Tricks for Professional Text
Advanced slicers like PrusaSlicer, OrcaSlicer, or Cura have specific settings that can save your logo prints.
- Combing (Cura): Set to "Not in Skin." This forces the nozzle to stay within the printed areas during travel moves, so any strings are hidden inside the print.
- Wipe While Retracting: This moves the nozzle back over the just-printed line while it retracts, "cleaning" the nozzle tip.
- Coasting: This stops extruding a tiny fraction of a millimeter before the end of a line, using the remaining pressure to finish the path. It’s a godsend for PETG.
8. Visual Guide: PETG Troubleshooting
The PETG Stringing Fix Hierarchy
Lower nozzle temp by 5°C increments. If it's too hot, it will flow like water.
Increase speed, then distance. Tune "Wipe" settings to clean the nozzle.
Set travel to 150mm/s+. Speed is your best friend to break the 'syrup' strings.
Dry your filament! Use 30-50% fan for small text details.
9. Frequently Asked Questions (FAQ)
Q1: Why does PETG string more than PLA?
A: PETG has a higher melt strength and is more viscous. It behaves like hot glue or syrup, whereas PLA has a "sharper" melting point that allows it to snap off more easily during travel moves.
Q2: Can I use a heat gun to remove the strings?
A: Yes! A quick pass with a heat gun or even a lighter will shrivel up PETG strings instantly. Just be careful not to deform the actual logo.
Q3: Is my nozzle worn out?
A: It's possible. A worn nozzle tip (especially brass) becomes rounded, which makes it harder to "wipe" the filament cleanly, leading to more oozing.
Q4: What is the best temperature for PETG?
A: Usually between 230°C and 250°C. For logos, try to stay on the lower end of your filament's recommended range to reduce liquidity.
Q5: Does print speed affect stringing?
A: Yes. Slower print speeds for the actual logo can help with detail, but the travel speed must remain high.
Q6: Should I use a silicone sock?
A: Absolutely. A silicone sock prevents PETG from sticking to the heater block and then falling onto your print as a giant burnt blob.
Q7: Is "Combing" the same as "Avoid Crossing Perimeters"?
A: They are very similar. Both aim to keep the nozzle over already-printed parts to hide any potential oozing. Use them!
10. Final Thoughts: Perfection is a Few Clicks Away
Look, printing PETG is a rite of passage. If you can master a clean, string-free logo with PETG, you can print pretty much anything. The key takeaway is to remember that cylinders are easy because they are consistent. Logos are hard because they are chaotic. By mastering your travel speed, disabling Z-hop, and ensuring your filament is bone-dry, you're taking the chaos out of the equation.
Don't be afraid to experiment. Change one setting at a time, print a small "text torture test," and see what happens. You've got this.
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