I have found that stringing and oozing rarely result in failed prints, but require additional work to get a print ready for use or display.
Set retraction distance to 3mm, retract speed to 55 mm/sec, and reduce printing temperature to fix stringing. Also consider increasing print travel speed (not print speed) and keep your print nozzle clean. If these don’t work, keep filament dry and reduce travel distance.
These tips should give you an idea of where to start so lets go into each one and discuss how to tune it more precisely for your printer.
What Are Stringing and Oozing?
When the nozzle moves between parts of a print, over an open area, some of the warm liquid filament in the nozzle may stick to one side of the print. As the nozzle moves across the opening, this liquid filament stretches across the opening like a spiderweb.
This is known as stringing.
Oozing can lead to stringing but is a separate issue. Oozing is caused when your temperature is too high and the filament has become too liquid and runny.
If your temperature is too high, rather than layers being laid down neatly on top of each other, the warm soft and possibly liquidy filament may run down the print before it cools and hardens.
As long as you don’t exceed the maximum recommended temperature for your filament, the most common problem oozing will cause is stringing.
Oozing causes stringing by creating warm liquid filament that flows easily out of the nozzle.
Enable and Configure Retraction
Because filament is being fed into the nozzle to enable printing, there is regular pressure on the liquid filament. Ideally, when the printer is done printing and needs to move the nozzle to another part of the print, the downward pressure would end.
This is not the case as gravity is still constantly pulling down on the liquid filament.
The solution is retraction.
Retraction pulls the filament up out of the nozzle to release the downward pressure and counteract the force of gravity.
There are 2 setting you need to set, retraction distance and retraction speed.
Retraction distance measures how much filament is pulled back by the extruder. A 3mm retraction distance will pull 3mm of filament back.
If you do not retract far enough you will still have stringing issues. Retract too far and the liquid filament will be pulled too far and potentially cause a jam. Too high of a retraction can also leave not enough filament in the nozzle when it come time to resume printing and result in holes in the print.
The general recommendation is to set retraction distance between 1 and 5 mm. Start with 3 mm and see how that works for you.
Retraction speed measures how fast the filament is retracted. A retraction speed that is too slow and you will still see stringing as the filament is not retracted enough in time to prevent it. On the other hand, if the retraction speed is too high, the solid filament may disconnect from the liquid and fail to pull it far enough.
The recommendation is to set speed between 20 and100 mm/sec. Start with 55 mm/sec and see how that works.
Print this simple stringing test print from Thingiverse.
If you keep having stringing and cannot eliminate it using retraction, the next thing to check is the temperature.
Reduce Print Temperature
As the filament heats up in the hot end, it becomes liquid. The hotter the liquid filament, the more liquidy and free-flowing.
When you print at the higher end of the recommended temperature range, the filament will tend to flow easier. The can be good for avoiding a jam at the print nozzle as the filament will more easily flow through.
However, the more easily the liquid filament flows through the nozzle, the more likely it is to flow out and string.
For PLA your print temperature range is 180 °C to 220 °C.
Since there is a trade off between print quality and stinging, you will want to make sure you have retraction as discussed above tuned in as best as you can.
Too high of a temperature can also counteract retraction settings. As noted above, if your retraction speed is too high, the liguid filament will separated from the solid during retraction.
As the temperature of the filament increases, the retraction speed that separates the liquid from the solid filament decreases. That means it is important to configure both setting to prevent stringing.
When calibrating your temperature, you can print this test print, a temperature tower specifically designed for testing stringing from Thingiverse.
Use the temperature that gives an acceptable print quality while minimizing stringing.
Increase Print Travel Speed
Configuring retraction and temperature setting should eliminate stringing in most cases. Don’t worry about travel speed until this setting have been tuned in.
It takes time for liquid filament to ooze out of the nozzle and cause stringing.
By increasing the print travel speed, the speed at which the print head travels while it is not printing, you give less time for the liquid print to ooze out.
If the travel speed is too fast, you may see print artifacts such as ringing or ghosting or misaligned layers.
There are no test prints designed for different travel speeds. Use this simple stringing test print from Thingiverse. Increase your travel speed in 5 mm/sec increments.
Keep an eye on each of the cones and watch for ringing or misaligned layers. When you start to see the cones printing with weird artifacts, you know you have reached too fast a speed.
Clean Your Print Nozzle
Any filament stuck to the end of the print nozzle can lead to stringing. As the nozzle heats up, that filament will also begin to melt. When the nozzle moves across and opening, this residual filament sticks to the print and is stretched across.
Cleaning the nozzle doesn’t have to be a chore.
Check the nozzle for any filament that may have gotten stuck on it. This is most common when there is an oozing problem and some of the oozing filament got stuck on.
If the filament pieces are large, you might be able to pull them off of a cold nozzle with some pliers.
Any pieces that you cannot get off with some cold pliers will need to be removed with a bronze brush.
I would recommend avoiding using a brush harder than bronze. You do not want to damage you nozzle.
A bronze brush can be found at a gun store or in the sporting area of the super market as they are often used for cleaning guns. I recommend this one from Amazon. It is only a few buck and works great.
To clean the nozzle, you will need to set the nozzle temperature based on the filament you are trying to clean. Set it to the lowest temperature for that filament, 180 °C for PLA.
Once the nozzle is warm, gently brush the filament off of the nozzle. If the temperature is too high, the filament may actually start stringing between the nozzle and the brush.
When you have removed all the stuck on filament, print out a test print.
Minimize Print Travels
So, you have configured your retraction and temperature setting to their optimal levels. But no matter what you do, there is always a little bit of stringing.
Since stringing only happens when the nozzle moves over an empty space, if we can get reduce the amount of times the nozzle has to travel outside the print, we can reduce stringing.
This is also a great way to avoid stringing when you cannot use retraction.
Retraction does not work well with flexible filaments like TPU. For flexible filaments your only option is to reduce travel outside of the print.
In Cura the setting to use is called Combing. If you use Simplify3D, the setting Avoid crossing outline for travel movement works the same way as combing in Cura.
Combing in Cura or Avoid crossing outline for travel movement in Simplify3D tells the nozzle to avoid going over gaps as much as possible. If the nozzle needs to move to another part of the print, the slicer will set a path for the nozzle that goes over already printed parts.
One issue with combing is that it will increase print time. How much will depend on the print itself.
Since the print head is combing over already printed parts, there is the potential that the nozzle may hit or stick to the print and pull it off the build plate. The nozzle can also pick up filament as it passes over potentially causing more stringing when passing over gaps is unavoidable.
Keep Filaments Moisture-Free
Filament, especially PLA, like to absorb moisture. If your filament has absorbed too much moisture, whether from the air or getting liquid on it, this moisture will turn to steam in the hotend.
Water expands much more than filament when heated, especially once it turns to steam. This steam will push filament out the nozzle and cause oozing. As mentioned earlier, oozing leads to stringing.
It is pretty simple to fix moisture. If you live in an area with high humidity, keep you filament in an air tight container with moisture absorbing packets. Most new filament comes packed this way.
I have used these large vacuum sealed containers from Amazon to hold multiple rolls of filament. I added these moisture absorbing dry packs to absorb any leftover moisture in the air. The dry packs can easily be renewed by heating them up in the oven.
While this worked great for me, the only problem I had was when I needed a new roll I had to open the package back up and reseal and repump to maintain the vacuum.
I switched over to using the Nanovac Vacuum Pump & Airlock Bag Bundle (non-affiliate) from Polyalchemy. The advantage of these bags is that they fit individual rolls.
How To Dry Filament Rolls
So you have oozing and can hear hissing and popping from water that the filament has absorbed turning to steam in the hot end. How do you fix this?
There is a filament dryer called the PrintDry Filament Dryer that can be used to dry out your filament. Using the Filament Dryer is pretty straight forward, put your roll of filament in, set the temperature based on the type of filament, and turn it on. After a preset determined time, pull out your dried out roll.
Another option is using your oven. Place your rolls in a preheated oven for roughly 4-6 hours at a fairly low temperature. The temperature depends on the filament type. You want to avoid heating the filament to a too high temperature. If the temperature is too high, the filament will start to melt and adhere to itself on the roll, completely ruining the roll.
Here is a guide for different filament types:
|Filament Type||Temperature in °C||Temperature in °F||Time|
|PLA||50 °C||120 °F||3 Hours|
|ABS, PETG, CPE,||65 °C||150 °F||3 Hours|
|Nylon||70 °C||160 °F||12 Hours|
|PVA||45 °C||115 °F||10 Hours|
|TPU, TPE||55 °C||130 °F||4 Hours|
|ASA, HIPS||60 °C||140 °F||4 Hours|
|PP||55 °C||130 °F||6 Hours|
|PC, PEEK||70 °C||160 °F||6 Hours|
The last option to consider is a food dehydrator. These operate consistently at lower temperatures than ovens generally are able to. Set the temperature as in the above table and you should be good.
After you have dried the filament roll out, be sure to place it in a sealed container.