Filament type selection is one of the core factors in 3D printing, as each filament has a unique set of properties that affect the printing process and the 3D printed model itself.
As PETG, a filament type that we can consider to be more challenging to print than PLA – is the next destination after spending enough time with PLA for most 3D printing enthusiasts, many filament-related questions in the 3D printing community are about PETG.
As a result, today, we will look at one of the most common PETG-related issues in particular, which is PETG filament sticking to the printer’s nozzle. Considering that this issue can bring many other problems, it’s definitely a vital one to solve.
So, why does PETG stick to the nozzle during print?
There are a few different factors that can cause PETG to stick to the nozzle, which are:
- Print temperature too low
- Incorrect nozzle gap
- Flow rate too high
- Clogged nozzle
- Problems with bed adhesion
In the upcoming section, we will go into greater detail about each of these factors and look at all the signs and other issues they can cause to make it easier for you to identify the root cause in your case.
Why Does PETG Stick to the Nozzle?
With many factors in play that can cause PETG to stick to the nozzle, taking a close look at each of them will help us identify the actual root cause and choose the appropriate solution for it.
Print Temperature Too Low
A low print temperature is one of the primary factors that can cause the PETG filament to stick to the nozzle.
If the filament doesn’t get warm enough to flow out of the nozzle optimally, it will get stuck in the nozzle, clump up, and eventually clog the nozzle.
With a print temperature that is too low, you will also notice signs related to under-extrusion, such as filament grinding, gaps and holes, missing and thin layers, and an overall lack of material on the 3D printed model.
Incorrect Nozzle Gap
Another common factor that can cause the issue is the nozzle gap being incorrectly set.
Both a nozzle gap that is too high or a nozzle gap that is too low can cause PETG to stick to the nozzle.
When the nozzle gap is too high, the filament won’t be able to touch the build plate, and as a result, start gathering on the nozzle.
On the other hand, when the nozzle gap is too low, the filament will start rubbing onto the nozzle due to there not being sufficient space for the extrusion, once again causing it to stick to the nozzle.
While a too high nozzle gap will usually show itself in the form of poor layer and bed adhesion, a too low nozzle gap presents itself with signs such as uneven lines, holes, scarring, and the plastic sticking way too much to the build plate.
Flow Rate Too High
A too high flow rate can also easily contribute to PETG sticking to the printer’s nozzle.
When the flow rate is higher than it should be, the amount of material extruded by the printer is more than optimal, and as a result, the excess material can end up sticking to the nozzle.
A flow rate value that is too high will often present itself with the signs of over-extrusion, such as oozing, blobbing, and stringing, and nozzle jam in more severe scenarios.
A nozzle that is already clogged can also contribute to more filament sticking to it.
When the nozzle is already clogged, it’s harder for the filament to escape the nozzle and make its way to the build plate. As a result, more and more plastic ends up being stuck to the nozzle, eventually completely jamming it.
A clogged nozzle will display signs such as uneven extrusion, thinner lines than expected, filament curling up towards the nozzle, and overall symptoms related to under-extrusion.
Problems with Bed Adhesion
Finally, issues related to bed adhesion can also be the reason behind PETG sticking to the nozzle.
If the adhesion between the PETG and the bed is poor, the filament has no other choice than to stay on the nozzle instead as it cannot stick to the bed.
If you are experiencing poor bed adhesion, you will also notice signs such as warping, gaps on the model, or the nozzle not extruding any plastic at all, depending on what’s causing the bed adhesion issue.
How Do You Keep PETG from Sticking to the Nozzle?
As a fair few different things can cause PETG to stick to the nozzle, there isn’t a single solution that fits every scenario.
Below are the solutions we recommend applying to keep PETG from sticking to the nozzle, depending on what’s causing the issue.
Increase the Print Temperature
The first step is to ensure that the print temperature is sufficient and increase it if not.
We recommend using a temperature between 220 and 260 degrees Celsius for printing PETG unless the manufacturer of the filament you’re using recommends the exact temperature you should use.
While you can always experiment to find the most optimal value, using this range will ensure that you won’t face temperature-related problems.
Correct the Nozzle Gap
Next up is correcting the nozzle gap.
We recommend using a nozzle gap of 0.1 mm for printing PETG, which is roughly the thickness of a piece of paper.
By placing a sheet of paper between the nozzle and the build plate, you can easily estimate the correct nozzle gap value.
Ensure that your bed is correctly level and that you pre-heat the bed before correcting the nozzle gap, as a heated bed is what you will be using while printing PETG.
Reduce the Flow Rate
Moving on, let’s tune the flow rate.
While the default flow rate value is 100%, this is often too much for PETG, which causes over-extrusion.
We recommend starting with a flow rate (extrusion multiplier) of 95% and experimenting to find the optimal flow rate depending on the results.
As the flow rate is a very delicate setting, even a percentage difference can easily cause over-extrusion or under-extrusion, meaning that experimentation is necessary to find the correct value.
Unclog the Nozzle
If nothing else has worked so far, it’s a good idea to take a look at the nozzle itself.
To resolve a simple clog, insert a piece of filament or a thin needle through the nozzle to move the plastic causing the clogging.
We will be going deeper into how you can unstick PETG from the nozzle in the upcoming section for more severe blockages where this method may not work.
Solve Bed Adhesion Issues
Finally, solving bed adhesion issues may be necessary to ensure that PETG doesn’t end up sticking to the nozzle.
As bed adhesion issues are a topic of their own due to the possibility of them being caused by a multitude of factors, we won’t be able to go into it in detail in this article.
That being said, you can read another article of ours where we extensively cover what can cause PETG to not stick to the bed and what you can do to fix it.
How Do You Unstick PETG from the Nozzle?
There are a few different methods to unstick PETG from the nozzle with varying difficulties, and the one you should use depends on the severity of the situation.
Below, we have listed the methods we recommend using to unstick PETG from the nozzle in increasing effectiveness (and difficulty as a result).
- Unclogging with a needle or a piece of filament – Insert the filament or the needle into the nozzle to try to move or break the PETG causing the clogging.
- Cold pull – Start by heating the nozzle to the printing temperature of the cleaning filament you will be using, and push some of the cleaning filament through the nozzle. Let the nozzle cool down as you keep putting pressure on the cleaning filament, and stop the pressure when the nozzle cools down. Heat the nozzle up once again, and pull the cleaning filament out, which should bring the PETG that’s causing the clogging with it.
- Nozzle removal – Carefully remove the nozzle from the printhead and manually clean the nozzle in different ways, such as using a heat gun to melt the PETG or unblocking the clogging with a needle.
While PETG sticking to the nozzle is an issue that many 3D printing enthusiasts encounter, it’s definitely not the end of the world, considering that finding the root cause and applying the solution is straightforward in most cases.
To quickly recap, here are the things that can cause PETG to stick to the nozzle:
- The print temperature is too low.
- The flow rate is too high.
- The nozzle gap is incorrectly set.
- The nozzle is clogged.
- There are issues regarding bed adhesion.
As each of these factors displays distinct signs, finding the one that is troubling you and solving it should not take a lot of your time, meaning that you will be back on track as soon as possible!