Stringing is an annoyingly common problem in PETG 3D printing that occurs when the melting filament escapes from the nozzle when it’s traveling between two points. This results in an unsightly hair-like appearance on the print, which is quite hard to remove. So, how can you prevent or at least reduce stringing on PETG?
Here are 12 tips and tricks on how to reduce stringing on PETG:
- Increase retraction speed.
- Increase retraction distance.
- Decrease minimum travel distance.
- Balance travel speed.
- Decrease nozzle temperature.
- Enable coasting.
- Enable the wiping feature.
- Use Z-Hop.
- Enable combing.
- Dry the filament.
- Control fan speed properly.
As a big percentage of PETG stringing is related to your printer settings, configuring your printer to the correct values is the best way to stop stringing. Read on to learn more about these printer settings.
1. Increase Retraction Speed
The retraction speed refers to how fast the extruder draws back the filament. If the speed is too low, the extruder takes its sweet time to retract the filament back, causing over-extrusion. This happens because the filament keeps oozing out of the nozzle before the extruder fully retracts it.
A low retraction speed is the number one cause of PETG stringing. It causes over-extrusion by making the filament ooze out of the nozzle when it shouldn’t.
Once you find the retraction speed setting on the menu, start by increasing the speed by increments of 5 millimeters (0.2 in) per second. If this slight increase makes a difference, you can continue to use smaller increments until you get that perfect print.
The optimal retraction speed varies from printer to printer, so finding that sweet spot is a matter of trial and error. But so you know, Bowden extruders require a higher retraction speed than direct-drive extruders. This means you can start the speed increment with a higher number than 5mm/s (0.2 in).
2. Increase Retraction Distance
The retraction distance refers to how far back the extruder pulls in the filament. If the retraction distance is too low, the filament remains close to the tip of the nozzle after retraction. As you can guess, this can mean over-extrusion because the filament is somewhere it can ooze out of the nozzle quite easily.
However, the low setting causes stringing, and it’s among the major causes. Even if the retraction speed is perfect, the low retraction distance will cause over-extrusion since the filament has nowhere to go. Having a too high retraction distance is not good either, as it can cause delays when you want the filament to come back down.
Again, go to the retraction setting menu on your slicer and find the retraction distance. More often than not, it’s right next to the retraction speed setting. Increase the retraction distance with small increments of 1 millimeter (0.04 in) and continue doing so until you get the perfect result.
One thing to note about retraction distance, though, is that you should also consider the length of the nozzle. If the nozzle is 12mm (0.47 in) long, do not set the retraction distance higher than that, as this can cause delays and clogging.
3. Decrease Minimum Travel Distance
The minimum travel setting determines the minimum distance required to trigger retraction. If this minimum travel setting is too high, retraction takes too long and sometimes never occurs. As a result, the filament stays at the tip of the nozzle and continues to ooze out, causing stringing.
On the other hand, a minimum travel setting that’s too high causes filament grinding since there are many retractions. This isn’t good, and it can cause the print to fail, so a high retraction minimum travel is always recommended.
However, there must be a balance between retraction minimum travel and the travel distance. For example, the minimum travel value should also be lower in print models where the retraction travel distance is too low. Hitting that balance will reduce stringing significantly.
To correct the retraction minimum travel setting, go to the settings again and increase the value by increments of 5 millimeters (0.2 in). Continue to adjust this value slightly until you get the highest possible value where you no longer experience stringing.
4. Balance Travel Speed
The travel speed, in this case, refers to how fast the extruder moves from one point to another while not extruding the filament. As you can imagine, a low travel speed setting means the extruder is moving too slowly between the points. This low speed can cause the PETG on the nozzle to ooze out and cause stringing.
Interestingly, setting the travel speed to a high value is also problematic and can cause ghosting or rippling. Ghosting and rippling are where weird artifacts appear on your print, and it’s not pretty.
Since both low and high travel speeds are bad, you have to find that perfect balance between the two. Go to the settings menu on your slicer as usual and increase the travel speed value by 5-10mm/second (0.2-0.39 in) increments until you find the balance. Making these speed adjustments can take a few tries, so you have to test print a few demos with every increment to see the differences.
5. Decrease Nozzle Temperature
The nozzle temperature, also known as printing temperature, is the temperature at which the 3D printer heats the filament. If this temperature is too high, the filament overheats and melts faster than it should. The overheating makes it flow out of the extruder uncontrollably and cause stringing.
You don’t want the nozzle temperature to be too low either, as this will cause a print fault, but there’s a balance as always. Since the melting point of any filament depends on the material it’s made of, you have to set the nozzle temperature to work with that particular filament.
For instance, the nozzle temperature range of 230°C-260°C (446°F-500°F) is recommended for PETG filament. However, each brand specifies the exact temperature you should use, so checking the packaging is important. This means you don’t have to go through trial and error when setting the nozzle temperature and all you have to do is enter the recommended figure.
If the nozzle temperature is too high and the filament is oozing out too fast, you can decrease the setting or turn the temperature off completely.
6. Increase Print Speed
As the name suggests, the print speed refers to how fast the printer moves when it’s printing your model. If the speed is too low, the nozzle stays in one place for too long and continues oozing filament. The only solution is to turn up the speed a little bit so the printer can move on faster.
Ideally, you should increase print speed by 5-10 millimeters (0.2-0.39 in) per second increments until you’re satisfied. You don’t want the speed to be too high either, as this can cause ghosting and weak layer adhesion.
Like every other setting in this narrative, you must rely on trial and error to get a perfect speed. It’ll help if you check the user manual of your printer, but it’s pretty much up to you to establish what works best for your 3D prints.
7. Enable Coasting
If you’ve tried all other configurations and nothing has worked against stringing, you may need to check out experimental features. Coasting is one such feature found in modern slicers like Cura. It works by replacing the last few millimeters of extrusion with a move where the printer stops extruding. As a result, stringing is avoided or at least reduced.
That said, coasting comes with its settings and configurations to work.
Too much coasting can cause under-extrusion, so you need to work with a few of its parameters like volume and speed to get the maximum efficiency. Thankfully, coasting speed and volume do not need much adjustment, and you can increase by 0.01 cubic mm (6.10 cubic in) until you get the desired result.
8. Enable the Wiping Feature
Wiping is another experimental feature in advanced slicers like Cura. When enabled, it causes the nozzle to move softly over the outer layer of your printed model and wipe off any remaining filament. As a result, the nozzle tip has no leftover filament that can cause stringing.
Enabling wiping is a really simple way of preventing stringing, especially if you combine it with coasting. It also has a parameter where you can adjust the wipe distance. Configure this value with increments of 0.1 millimeters (0.004 in) until you get the perfect setting.
9. Use Z-Hop
Also known as a vertical lift, the z-hop is yet another advanced feature that causes the nozzle to move up just a bit after retraction. This feature prevents PETG from stringing as the extruder won’t leave leftover filament on the print due to the distance created. In some cases, though, it works by causing the plate to move down after retraction.
If you’re using Cura, you can easily find the z-hop setting in the Travel menu. Experiment with this feature first to see how it works for you, as some people claim it makes stringing worse.
10. Enable Combing
When doing 3D printing, the slicer goes first and cuts a path where the extruder will follow. This is called a travel path. In rare cases, travel paths cause stringing unless you adjust the spaces. Make sure the extruder doesn’t leave the boundaries of print when passing through the travel paths.
As usual, you can find the feature called combing on the Travel settings and enable it. It’ll recalculate the travel paths so that the extruder stays over the print at all costs, even if that means a greater travel distance.
Keeping the travel paths on the boundaries of the print eliminates the need for retraction and thus prevents the filament from stringing.
11. Dry the Filament
But what if you’ve configured all the settings to perfection, and it wasn’t enough to stop stringing? Maybe your filament is the problem. PETG is prone to absorbing moisture from its environment, which is why it should always be covered.
Sometimes, moisture can cause the filament to string, among other issues like weak layer adhesion, cracking, and blobbing. Unfortunately, it’s impossible to know how moist the filament is beforehand. It’s only during printing that you will tell the filament has been compromised.
In this case, you must dry the filament first before using it again. You can remedy the situation by putting the filament in an oven at 60°C (140°F) for at least 6 hours. Alternatively, place the filament in a container with a desiccant for 24 hours or more.
12. Control Fan Speed Properly
The general rule when printing PTEG is the less fan, the better the layers will bond and strengthen. Unfortunately, this will also lead to a bad finish with stringing and poor overhang. On the other hand, a fan speed of 100% gives the best surface resolution but a weaker bond.
A good compromise is starting at 40% fan speed and increasing or decreasing as needed. For instance, if you have a bridging section somewhere, increase the fan speed so the molten doesn’t sag before it’s cooled.
The Best PETG Print Settings
As promised at the beginning of this article, here are some of the best PETG print settings you can use to reduce stringing on PETG:
- Temperature: The recommended printing setting for PETG is 220°C-245°C (428°F-473°F), depending on your extruder. The PETG bed temperature should be around 70°C-75°C (158°F-167°F), though you go a little hotter for the first few layers.
- Surface: Blue painter’s tape is the best surface to print PETG on. It’s a very old method that has passed the test of time. Generally, PETG has no issues sticking to the print surface, so you’ll have difficulty taking it out if you stick it on standard material.
- Offset: Allow an extra 0.02-0.06 mm (0.0008-0.002 in) offset when printing. PETG doesn’t work well when squeezed onto the print bed, and it can cause blobs and strings, among other issues. Start off moving the nozzle away in 0.02 mm (0.0008 in) increments until there’s no skimming.
- Speed: As with most 3D printing materials, PETG prefers to be printed slowly. 60mm/second (2.36 in) is the recommended speed to allow the filament time to bond and cool sufficiently.
Experiencing stringing on your 3D print model is a nightmare, to say the least. However, it’s not something you must live with, as simple tweaks on your printer can solve the issue.
Even though configuring the printer settings can take time and a lot of trial and error, the process is not really technical. In the end, you’ll be glad you did it when your print models come out perfect.