Background: What is stringing or oozing

Stringing, also called oozing, is one of the most common problems in 3D printing. Stringing usually takes on two common forms:

1) Larger, thicker strings of material, along the path between where the nozzle moves during printing:

2) Finer, wispy strings, also along the same path, but because the strings are so light, they tend to also float around or move from your cooling fan:

Whenever your printer stops printing to travel to another area, then resumes printing, there's the potential for stringing to occur. For example, any part with two separate towers or columns can display stringing.

Basically, when the extruder stops pushing, the material in your hotend continues heating up-and expands-which builds pressure behind the nozzle. There are two ways this pressure is relieved: filament oozes out of the nozzle, which causes that pesky stringing, or, your extruder "retracts" or pulls back the filament. And if these retractions not well-tuned, oozing can still occur. "Retraction settings" usually refer to the retraction distance and retraction speed, and even advanced settings like retraction retract speed.

Factors that can cause stringing

Other factors can complicate the process even more. For instance, hot-end temperature and layer height can change the situation enough where previously good retractions no longer relieve that pressure. Travel speed or print speed can have an effect too, but in our experience, these are not as dominant. Sometimes the toolpath can unnecessarily induce more stringing-or do a good job of hiding it.

Thankfully, we've prepared some of the most common solutions to stringing. Let's dive in!

1. Retraction

Getting retraction settings sorted is key! Retraction settings are typically the cause of stringing. Increasing both retraction speed and retraction distance are important to eliminating stringing. Best practice is to increase retraction speed by increments of 5 mm/sec and increasing retraction distance by 0.5mm. Print a small part and see if there is stringing. If there is, increase retraction speed and retraction distance by 5mm/sec and 0.5mm respectively. Just before careful going too high on these settings, otherwise problems like under-extrusion can be prone to occur.

2. Nozzle Temperature

Nozzle temperature can have an effect on stringing. 3D printing filaments often ooze or become more liquid at higher temperatures, thus increasing stringing. A common practice is to reduce the nozzle temperature by increments of 5C. At lower temperatures the filament is harder and less likely to fall out of the nozzle. However, be careful not to go below the manufactures specifications otherwise you may compromise layer adhesion resulting in weak prints. Some rough guide lines of print temperature can be found below.

• PLA: 180-220 C
• ABS: 200-250 C (90-100 C print bed)
• PETG: 215-235 C
• TPE: 210-240 C (20-70 C print bed)
• PVA: 160-190 C (60 C print bed)
• TPU: 230-250 C (60 C print bed)

3. Travel Speed vs Print Speed

Travel Speed: The speed at which the print head moves when it is not extruding filament. Print speed: The speed at which the print head moves while its extruding filament.

Between travel and print speed, travel speed typically has a larger influence on stringing. This is because stringing does not happen while extruding, it happens when the print head is finished extruding and moves to another area of the print. Increasing the travel speed lowers the amount of time the filament has to ooze out of the nozzle. If there is no time for the material to leave the nozzle, then it simply won't, resulting in less stringing. Don't go crazy with travel speed though as it may cause the motors or belts to skip, leading to layer shifting.

4. Moisture in Filament

Hygroscopic filament-or material that tends to absorb moisture-is especially prone to stringing. It is good practice to always store filament in a dry filament box or dry your filament before or during use. Materials like PETG are prone to this problem if not stored properly. Nylon is so hygroscopic that it's recommended to keep it environmentally controlled even while you're printing. Some common hygroscopic materials are listed below, and should be kept in a dry environment.

• Nylon
• ABS
• PETG and PET
• TPU (Flexible)
• Polycarbonate

5. Material hanging from nozzle

An unexpected source of stringing can occur from material catching on the outside of your nozzle. During printing, it may catch on printed areas and get pulled around and catch on different areas of your print. This can still happen even when your settings are perfectly tuned! We see this very often when printing with materials like PETG.

In summary, it is often best to trouble shoot stringing by printing a temperature tower. Some of the most common causes of stringing include:

• Retractions turned off
• Wrong choice of retraction speed or distance
• Printing with a temperature too high (or less commonly, too low!)
• Other settings like travel speed, wiping, or combing, which help, but are not the main factors
• Using filament which has absorbed too much moisture
• Letting filament accumulate on the outside of your nozzle

Want to fix your stringing and print with confidence?

Printing "temperature towers" is a common method for tuning temperature. The same approach works for tuning retraction distance and retraction speed. If it's not a physical problem with your printer or material, getting these settings right almost always fixes the problem. Try our free temperature/retraction calibration tower generator tool to troubleshoot your settings.

Already know how to tune these settings manually and want an easier way? We've done 100s of experiments with many materials and printers, especially Creality printers, and we've built an AI engine that gives you everything you need. No more guessing settings or even configuring Cura. We give you a 3mf file already set up with everything for your printer.