What Causes Poor PETG Layer Adhesion? (Tips & Tricks to Fix)

3D printing is certainly not an easy hobby at times, as unexpected issues can suddenly appear and ruin a print just as you think that you configured everything correctly.

Without a doubt, the most frustrating form of issue is when you make a slight modification to the process, such as changing the filament, and everything suddenly falls apart.

Poor PETG layer adhesion is perhaps the best example of such an issue, with many enthusiasts switching to PETG filament to benefit from its naturally strong layer adhesion capabilities but being greeted with the complete opposite.

As this is an issue that we hear a lot about in the community, we decided to dedicate today’s article to diving into what causes it and how you can fix it in a detailed manner.

So, what causes poor PETG layer adhesion, and how can you fix it?

Here are some of the factors that can cause poor PETG layer adhesion.

  • Low printing temperature
  • High cooling fan speed
  • High printing speed
  • High layer height
  • Low flow rate (extrusion multiplier)

As fixing the poor layer adhesion problem requires you to find the factor causing it, let’s start by taking a deeper look into each of these factors and the signs and symptoms they bring.

What Causes Poor PETG Layer Adhesion?

Since a few different causes can be behind poor PETG layer adhesion, we will talk about each of them separately and in detail to help you identify the one giving you trouble.

Low Printing Temperature

A low printing temperature is the most common reason behind poor PETG layer adhesion.

As the filament needs to be hot enough to melt and adhere, a low printing temperature will outright prevent the layers from sticking to each other.

Alongside poor layer adhesion, low printing temperatures usually cause skipping, grinding, and under-extrusion as a result.

High Cooling Fan Speed

A cooling fan speed that is too high is also one of the most common reasons behind poor PETG layer adhesion, coming right behind low printing temperatures.

Similar to the problem caused by a low printing temperature, a high cooling fan speed will easily prevent layers from sticking to each other by drying the plastic way too fast.

A high cooling fan speed usually also causes warping alongside poor layer adhesion.

High Printing Speed

Another factor that can cause poor PETG layer adhesion is high printing speeds, and while not as common as the previous factors, it can certainly be a problem.

A high printing speed prevents the layers from having enough time to adhere to each other, and as a result, the layers entirely separate from one another.

Typical symptoms of a high printing speed include blobbing, stringing, filament grinding, ringing, and artifacts.

High Layer Height

Layer height has a significant role in layer adhesion, and its value being too high will most certainly lead to problems.

As layer height determines the thickness of a layer, setting it too high reduces the heat transfer between the current layer and the next, causing adhesion issues.

Layer height being too high often causes the quality of your prints to be lower as well.

Low Flow Rate (Extrusion Multiplier)

While very unlikely, a low flow rate can be the culprit behind your layer adhesion problems, which makes it worth mentioning as the last factor in our list.

If the flow rate is too low, there won’t be enough filament for the layers to form strong bonds, causing the layers to separate.

A common sign of a low flow rate is under-extrusion as flow rate directly controls the amount of extruded plastic.

How to Fix Poor PETG Layer Adhesion?

After finding the cause behind your PETG prints having poor layer adhesion, all there is left to do is applying the related fix, which is the easy part.

If you could not find the cause, you can also take more of a trial-and-error approach by trying each solution in order and running test prints to see whether it worked or not.

Increase the Printing Temperature

While the optimal printing temperature depends on the brand of the filament, a range of 230 to 260 degrees Celsius is often considered optimal for PETG.

Depending on the manufacturer of your filament, you may find the suggested temperature on the packaging, which will most likely give the best results.

Decrease the Cooling Fan Speed

As the optimal fan speed depends on the cooling fans you have, we recommend lowering the fan speed in increments of 10 percent until you find a value that works well.

While using a 0 percent cooling fan speed is not unheard of while printing with PETG for maximum layer adhesion, it’s vital to consider that lower fan speeds also reduce the aesthetical quality of your prints.

Decrease the Printing Speed

Our tests revealed that setting the printing speed between 50 and 60 mm/s yields the best results for PETG, and speeds over 60mm/s often cause layer adhesion issues.

As the optimal speed can vary depending on your printer and the filament you’re using, we recommend starting at 60 mm/s and decreasing the printing speed in increments of 5 mm/s until you find the value that works best.

Decrease the Layer Height

As a rule of thumb, the optimal layer height should be below 80 percent of the nozzle diameter, with no limit on how thin it should be.

For instance, for a 0.4mm nozzle, you should not set the layer height to a value above 0.32, but you can set it as low as you wish to.

While a low layer height increases the print time, it improves the aesthetical quality of your print.

Increase the Flow Rate

The best value for the flow rate is often 100%, but you can increase this value up to 110% if nothing else helped you fix your layer adhesion issues.

We only recommend increasing the flow rate as a last resort due to its possibility to introduce issues such as blobbing.

How Do I Get PETG to Stick to the Bed?

As PETG not sticking to the bed can be caused by various issues, you will most likely need to try a few different things to get it to work.

Here are some things that can help you to get PETG stick to the printer bed.

  • Clean the printer bed with isopropyl alcohol.
  • Ensure that the printing temperature and the bed temperature are correct.
  • Ensure that the nozzle height is correct.
  • Ensure that your filament isn’t moist.
  • Ensure that the printer bed is level.
  • Double-check the first-layer settings in your slicer.
  • Use adhesives such as hairspray, painter’s tape, or glue on the printer bed.

PETG vs. PLA Layer Adhesion: Which Is Better?

While bed adhesion is much simpler with PLA, PETG is undeniably the best choice if you need strong layer adhesion.

The main reason behind PLA’s popularity is its ease of use. As printing with PLA doesn’t require high temperatures, a heated bed, or a closed chamber, most 3D printing enthusiasts start their journey with PLA.

On the other hand, PETG is known for its strong layer adhesion, making it the best choice for scenarios where durability is a vital factor, such as industrial applications.

As PETG is usually more challenging to print than PLA, poor layer adhesion with PETG is a common issue in the community despite PETG being one of the strongest filament materials.

Wrapping Up

As PETG is a material that naturally has strong layer adhesion, misconfiguration is the cause behind poor PETG layer adhesion in most scenarios.

Issues such as misconfigured printing temperature, cooling fan speed, printing speed, layer height, and flow rate can easily contribute to you experiencing poor layer adhesion with your PETG prints.

Fortunately, these issues are pretty straightforward to fix once you identify the one giving you trouble, meaning that you will be getting back to 3D printing as usual in no time.

We hope that this guide was helpful for you to fix your PETG layer adhesion issues as quickly and painlessly as possible.

Happy printing!