One of the most common and frustrating issues in 3D printing is stringing. These thin strands of plastic span across your print, marring the surface. But don’t despair – this guide covers everything you need to know to troubleshoot stringing and get cleaner, professional quality prints.
What Causes Stringing on 3D Prints?
Stringing refers to thin threads of plastic that strech across gaps or surfaces of a 3D printed part. It stems from the natural oozing of molten plastic from the hot nozzle.
As the nozzle moves across gaps in the print, tiny strands of filament ooze out and solidify, creating strings spanning the open space. The effect is particularly bad on models with small holes or enclosed spaces.
Anything that increases oozing will make stringing worse. Common culprits include:
- High temperature – Too hot for the filament causes excess oozing.
- Low retraction – Fails to fully counteract nozzle pressure.
- Slow print speed – Gives filament more time to ooze during travel moves.
- Wet filament – Moisture creates popping and inconsistencies during extrusion.
Stringing only occurs during non-print travel moves when filament continues to seep from the nozzle. Reducing ooze will eliminate the problem at its source.
Effects of Stringing on Print Quality
Strings themselves are often just a cosmetic nuisance on the surface. But excessive stringing can negatively impact prints in other ways:
- Strings sticking to nozzle – Can dislodge printed parts from the bed or damage fine details.
- Clogged nozzle – Strands collecting around the nozzle can eventually jam it.
- Messed up internal cavities – Stringing inside small holes or gaps create unwanted internal debris.
- Weaker parts – Strings don’t fully fuse, leaving micro-porosity weak points in the model.
So while mostly just ugly artifacts, bad stringing can ruin critical dimensions, trap unwanted plastic internally, and ultimately lead to print failures.
How to Reduce and Prevent 3D Printer Stringing
Several important settings and techniques can help reduce stringing at the source:
Lower Print Temperature
Printing hotter than needed allows excess filament to leak out under pressure. Try lowering nozzle temperature in 5-10 degree increments until you find the lowest stable temp.
But don’t drop too far – uneven extrusion and clogging can also occur when too cold. Find the sweet spot for your particular filament.
Increase Retraction Distance
Retracting filament during travel pulls back ooze and relieves pressure. Experiment with increasing retraction distances from 5mm until stringing is eliminated. Don’t exceed 8mm though to avoid stripping the filament.
Faster Retraction Speeds
Increasing retraction speed helps filament retract quickly before oozing resumes. Try speeds of 40-70mm/sec to minimize ooze windows. But too fast can strip or jam filament in the gears.
Avoid Ooze Buildup
Wiping the nozzle over an ooze pad in the print can collect leaked material before continuing the print. Alternatively, avoid staying too long in one spot while hot.
Slower Non-Print Moves
Giving filament less time to ooze while traveling between print sections reduces stringing opportunities. But don’t slow too much as increased print times can bring other issues.
Dry Filament
Wet filament pops and sputters, increasing erratic pressure and seepage from the nozzle. Always use properly dried material to minimize ooze inconsistency.
Nozzle Wipe and Brush
Some printers include automatic systems to wipe nozzles and brush away strings between print sections to keep things clean. Look for models with these ooze prevention features.
How to Remove Existing 3D Printer Stringing
Even with the best tuning, some strings may still occur. Here are ways to clean them up post-print:
Hot Air Gun
A simple hot air gun heated to around 200°C can soften strings so they can be manually pulled or brushed off with pliers or wire brush. Take care not to overheat and warp the print.
Sandpaper and Files
Light sanding with fine grit removes superficial strings along flatter print surfaces. Needle files or hobby knives can also slice away stubborn strands in hard to reach areas. Avoid damaging the actual print geometry.
Acetone Vapor Bath (ABS only)
For ABS prints, an acetone vapor bath can effectively dissolve strings while leaving the rest of the part intact. Suspend the print above a small container of acetone. Seal and let acetone vapors smooth everything.
Masking Fluid (PLA only)
After printing PLA, brush on liquid masking fluid onto the stringing areas and let dry. Peel away the dried fluid to remove stringing in one sheet while leaving the print untouched.
Post Processing Tools
Dedicated smoothing tools like the Print Smoothing Station use heat and scrappers to remove stringing quickly from PLA and PETG prints. Similar to sanding but gentler on the model.
Best Printers for Avoiding Stringing
Not all printers are created equal when it comes to minimizing stringing thanks to different hotend and cooling designs:
- Prusa i3 MK3S – Excellent heatbreak and cooling fan keeps oozing low. Great overall performance minimizing stringing.
- Ultimaker S5 – Wiper systems and optimized airflow profiles ensure ultra clean prints.
- Formlabs Form 3 – SLA printing’s lack of hot extrusion eliminates stringing entirely.
- Original Prusa MINI+ – Compact hotend makes retractions fast and effective for crisp prints.
- FlashForge Creator Pro 2 – Fully enclosed chamber and high quality components reduce stringing.
Look for models with effective cooling, priming stations, and wiping functions purpose-built to reduce stringing rather than basic extruders prone to lots of oozing.
Is Stringing Always Bad?
In some cases, stringing may just be a cosmetic nuisance and can be tolerated:
- Purely decorative prints – Strings don’t compromise function or dimensions.
- Easy post-print removal – Simple sanding or vapour bath cleanup.
- Internal prints – Strings trapped inside make no difference visually.
If stringing occurs on non-critical regions and post-processing can quickly fix it, you may choose to accept minor instances rather than prolong print tuning.
But any strings that affect function, precision fittings, measurements, or safety should be addressed at the source with proper calibration.
When to Take Further Action
If the above adjustments fail to significantly reduce stringing, more intervention may be required:
- Nozzle replacement – Worn nozzles can develop grooves that encourage ooze. Swap in a new nozzle.
- Hotend maintenance – Take apart the hotend completely and clean any debris or old filament.
- Firmware settings – Adjustment firmware retraction settings if slicer changes alone don’t help.
- Hardware upgrades – All-metal hotends, better cooling, or hardened steel nozzles can improve performance.
- Different filament – Lower quality or impure filament can cause excess stringing even when tuned.
Eliminating stringing should always be possible with patience and methodically testing each variable. Persist until you pinpoint the specific factor allowing those pesky strings!
Stringing Troubleshooting Recap
Follow this general process when confronted with stringing:
- Lower nozzle temperature incrementally.
- Increase retraction distance up to 8mm max.
- Adjust retraction speed to 40-70mm/sec.
- Enable coasting, wipe, and ooze shield if available.
- Slow down non-print moves below 150mm/sec.
- Replace nozzle.
- Disassemble and clean hotend thoroughly.
- Try alternate filament brands – could be a bad spool.
- Upgrade hotend, extruder, fans if hardware is under-performing.
With some experimentation, stringing can always be brought under control for that perfect professional 3D print finish.
Conclusion
Stringing is one of the most frustrating 3D printing artifacts, but thankfully can be managed with the right techniques. Focus on reducing oozing through temperature, retraction, coasting, and print speed adjustments for the best preventative results.
For occasional strings that do appear, post-processing tools like heat guns, sandpaper, and acetone baths can improve finished prints. With quality filament and a properly tuned printer, you’ll be ready to conquer stringing and take your print quality to the next level.
