Why Is My PETG Bubbling During 3D Printing? (How to Fix It?)

We can all accept that 3D printing is an activity where the chance of issues occurring is considerably more substantial compared to more mainstream, less technical hobbies, to an extent where we can consider troubleshooting to be a regular part of 3D printing.

On the other hand, more often than not, there are reasonable explanations for the issues we face while 3D printing, as the problem primarily comes down to us overlooking simple things that end up having a significant impact.

In this article, our topic will be the issue of PETG filament bubbling during the 3D printing process, a common problem where bumps start appearing on the 3D printed model, completely ruin its aesthetics as a result and most likely infuriate us in the process.

So, what can cause your PETG to bubble during the 3D printing process?

The primary factor that can cause PETG to bubble during printing is the absorption of moisture by the filament, which presents itself as bubbles once the water comes into contact with the high temperatures of the nozzle and releases pressure.

While less likely, a too-high print temperature value can also cause similar effects, as the printer would essentially be boiling the PETG during printing.

Next up, we will dive into the factors that can cause PETG to bubble in more detail, discuss the methods you can use to fix the bubbling issue, and share with you the signs and symptoms you can use to identify the problem.

Why Is My PETG Bubbling During 3D Printing?

Even though a few different factors can be responsible for PETG filament bubbling during 3D printing, one primary reason, in specific, is responsible for the majority of the cases.

Moisture in the PETG filament, which is a pretty common occurrence, especially if you had your spool of PETG for a while now, is the main culprit behind PETG bubbling during 3D printing.

As we are all familiar with, exposing water to temperatures above 100 degrees Celsius causes it to evaporate and turn into steam in the process, releasing some pressure as it starts rising into the air.

Since the temperature of the nozzle during printing is more than enough to cause water to turn into steam, the pressure released from the PETG as water evaporates causes pockets of air to form on the model as the stream rises, which we know as the issue of bubbling.

While most cases of PETG bubbling are due to the filament absorbing moisture, there is one more factor that can cause a similar issue if moisture is not the culprit.

A print temperature that is too high can cause the issue of PETG bubbling by exposing the plastic to temperatures where it will essentially start boiling and forming bubbles.

As the nozzle cannot control the flow of the plastic in such a case, the appearance of artifacts on the 3D printed model is unavoidable.

How to Fix PETG Bubbling During 3D Printing?

Fixing the issue of PETG bubbling during 3D printing primarily comes down to finding and applying the correct solution, and it shouldn’t require a lot of expertise or effort.

Below is a step-by-step guide we recommend following to fix your issue of PETG bubbling during the 3D printing process:

  1. Reduce the printing temperature. To eliminate the possibility of print temperature being too high, we highly recommend using the temperature value suggested by the filament manufacturer.
  2. Dry your spool of PETG. There are plenty of different ways for drying PETG effortlessly and quickly, which can even involve ordinary household objects such as an oven or a food dehydrator.
  3. Try a different, preferably brand new spool of PETG. As there is a chance that the drying process has not removed all the moisture, it can be helpful to run a test print with an entirely new spool of PETG to pinpoint the issue.
  4. Check and clean the nozzle. If else fails, checking the nozzle is often a good idea to see if some form of blockage could be causing the issue.

We highly recommend going for a test print after applying each fix, as a test print is the surest way to see whether you have solved the problem or not.

How to Identify PETG Bubbling?

Identifying whether you’re facing the issue of PETG bubbling or not is a vital part of applying the right solution, considering that problems can have similar signs at times but require different fixes.

The primary sign of PETG bubbling is the inconsistent formation of bumps throughout the 3D printed model, which look like pockets of air that elevate the plastic in some parts.

If the bubbling takes place due to the absorption of moisture, the most apparent signs you can observe are crackling and popping sounds, and in some cases, visible steam coming out of the extruder during the printing process.

On the other hand, if a too high print temperature is the culprit, the primary sign is a model that looks blurry, as if parts of liquid plastic are pooled together, pretty similar to how burnt plastic looks.

In both cases, alongside the bubbles, you can also experience signs such as weak layers, inconsistent extrusion, and overall suboptimal print quality.

PETG Only Bubbling on First Layer – What to Do?

An interesting issue related to PETG bubbling is when the bubbles only appear on the first layer but not the rest of the model, which usually points to a different set of culprits.

Here is a step-by-step guide we recommend following if you experience PETG bubbling exclusively on the first layer:

  1. Ensure that the printer bed is level.
  2. Increase the layer height value for the first layer.
  3. Increase the Z-offset value.
  4. Reduce the first layer flow rate.

As usual, a test print after each step is the best course of action to pinpoint the problem and avoid wasting time.

Wrapping Up

While a few different factors can cause PETG to bubble during the printing process, it’s one of the easier problems to troubleshoot due to the culprit being the same in almost all scenarios.

To summarize quickly, the most common factor that causes PETG to bubble during printing is the absorption of moisture, which causes the filament to store water.

Even though the water itself is not damaging to PETG, the high temperature of the nozzle causes the water to turn into steam during printing, and bubbles start appearing on the model due to the pressure.

While rarer than the issue of moisture absorption, it’s worth noting that a print temperature value that is too high can cause the problem of PETG bubbling, as temperatures that are too high cause the filament to boil.

Happy printing!