What Causes First Layer Curling on 3D Printed Models?

We are sure that we can all relate to the fact that new issues keep coming up whenever we think that we have perfected the 3D printing process, leaving us to wonder what has gone wrong this time over and over.

Sometimes hardware, sometimes software-related, the issues can become quite mind-boggling at times, especially when another problem pops up right after fixing the previous one.

Today, we will be talking about one of the most commonly encountered issues that trouble 3D printing enthusiasts regardless of the filament type, printer, or slicer they use, which is the curling of the first layer.

So, what causes the first layer curling issue on 3D printed models?

First layer curling happens due to the exposure of hot filament to the cold temperature of the build plate and the air – with the sudden change in temperature causing the filament to contract suddenly and severely.

As the force of the contraction shouldn’t be enough to cause the corners to curl in an optimal scenario, such an issue usually points out bed adhesion problems.

In the upcoming sections, we will look at why first layer curling occurs in greater detail, discuss what you can do to fix it and point out the signs you should watch out for to help you recognize the problem.

What Causes First Layer Curling on 3D Printed Models?

While the reason behind the curling of the first layer can be slightly confusing to understand at first, there’s actually a simple and scientific explanation for it.

As you know, the molten filament reaches very high temperatures (above 200 degrees Celsius for almost all filament types) as it leaves the nozzle, which causes it to undergo a phenomenon known as thermal expansion, where the material expands due to the heat.

When the filament makes its way out of the nozzle and touches the build plate, it rapidly starts cooling down due to both the bed and the air being much colder than the internal temperature of the plastic, with cooling fans also accelerating the process.

The sudden change in temperature causes the opposite of thermal expansion, known as thermal contraction, where the material starts shrinking.

The force that appears as a result of the contraction causes the material to pull on itself, essentially making it so that it tries to separate itself from the build plate.

If the adhesion strength between the layer and the build plate isn’t high enough at this point, the force of the contraction causes the corners of the layers to lift and detach from the surface, producing the phenomenon we call first layer curling.

In most cases, the occurrence of the first layer of curling issue is a sign of bed adhesion problems, which can happen due to many factors, with incorrect bed leveling, low bed temperature, and dirty build plate, to name a few.

How to Stop and Fix First Layer Curling on 3D Printed Models?

Since the issue of first layer curling is all about providing the right environment for the filament to cool down gradually and evenly, there are a few variables you can change in the printing process.

Level the Build Surface

A build surface that isn’t level is perhaps the primary contributor to the issue of first layer curling due to it causing bed adhesion problems by making the printer miscalculate the height between the build plate and the nozzle.

You can level the build surface by following the simple process of sliding a piece of paper between the build plate and the nozzle on every corner of the build plate and adjusting the bed in a way that there is no gap between the build plate and the paper, and the paper and the nozzle.

On the other hand, as manual leveling can be unreliable, a better way to level your bed is to purchase and install a bed leveling probe, such as BLTouch, and let it handle the leveling process.

Clean the Build Surface

Another culprit behind poor bed adhesion, and hence first layer curling, is a build surface that isn’t clean enough, as the filament needs the build surface to be entirely clean to adhere as well as possible.

The vital point to keep in mind here is to wipe the surface thoroughly with the optimal cleaning agent and ensure that you don’t touch the surface with your hands or place any items on it to keep it completely clean.

As the optimal cleaning agent is dependant on the material of your build surface, we recommend researching on the web to find out what works best for the one you use.

Disable Cooling

As the issue of first layer curling is related to the contraction of the filament, the cooling fans also contribute to the problem by cooling the material way too quickly and increasing the severity of the contraction.

Completely disabling the cooling fans while printing the first layer is usually the best idea to ensure that the layer sticks to the bed as well as possible.

As the upper layers will require cooling, you should use the parameter that specifically disables fans for the first layer only, such as the Initial Fan Speed parameter in Cura.

Adjust the Bed Temperature

Bed temperature is another factor that plays a significant role in solving the first layer curling issue as it has a considerable impact on the adhesion of the first layer.

We recommend finding the optimal bed temperature for the filament you use through the filament’s packaging or the manufacturer’s website, as this temperature will most likely yield the best results.

If you still experience first layer curling with the recommended bed temperature, incrementally increasing the bed temperature and running more test prints is usually the way to go.

Adjust the Z-Offset

Similar to an unlevel bed, a misconfigured Z offset can also cause the first layer to curl by causing the printer to calculate the distance between the build plate and the nozzle wrongly.

The Z-offset value should account for the gap between the build plate and the nozzle, meaning that the correct Z-offset value should make it so that there is no gap.

To set the Z offset correctly, home the printer with the G28 G-code, and then specify the Z offset value you would like to use by using the G92 G-Code.

Adjust Initial Layer Settings

The two initial layer settings of initial layer height and speed are also something to look at, as these parameters have a significant impact on the adhesion strength of the first layer.

In a nutshell, you should thicken the initial layer height and reduce the initial layer speed for the first layer to adhere to the bed more strongly, as more plastic and more time for cooling down will directly increase the adhesion strength.

To perform this action without disrupting the configuration for the rest of the layers, you can use parameters such as Initial Layer Height and Initial Layer Speed in Cura.

Adjust the Print Temperature

As the print temperature directly decides how hot the filament gets, it’s also a contributing factor to the curling of the first layer when it’s not configured correctly.

We recommend using the print temperature the filament manufacturer suggests for the best results possible, but feel free to decrease it in small increments and experiment if you still face first layer curling.

In most scenarios, the print temperature should not be the problem as it would cause many other issues that you would notice before the curling.

Apply Adhesives to the Build Surface

If all else fails, applying adhesives to the build surface is also a fantastic way to strengthen the bonds between the first layer and the bed.

Depending on the build surface you use, adhesives such as hair spray, glue stick, and painter’s tape can increase the adhesion between the first layer and the build plate, which will give the adhesion enough strength for it to resist the force of the contraction.

Please ensure that the adhesive you will use is compatible with the build surface before applying it to ensure that you don’t damage the surface.

Use a Brim or a Raft

Brims and rafts are handy for increasing the strength of the bed adhesion, especially for models that don’t have flat bottoms.

Brims and rafts serve the purpose of both increasing the surface area that connects to the build plate and ensuring that the part of the model that touches the build plate is flat and even.

As a flat surface is vital for the heat to be distributed equally, brims and rafts are a fantastic way to combat issues related to first layer curling.

Use an Enclosure

While usually not very necessary unless the filament you’re printing requires it, an enclosure is quite helpful to reduce the effects of the cold air on the first layer.

With the help of an enclosure, you can completely negate the effects of the ambient temperature and keep the temperature of your model as stable as possible.

As we don’t recommend buying an enclosure only for solving the first layer curling issue (since it’s an investment), you should only use it as a last resort if nothing else has helped.

How to Recognize First Layer Curling on 3D Printed Models?

When we say first layer curling, it can sound slightly vague if you have never experienced the problem before.

In a nutshell, the easiest way to understand whether you’re experiencing first layer curling or not is to observe the corners of your model while the printer is printing the first few layers and see if the corners start lifting from the build plate.

Even if one of the corners of the first few layers of your model curls off the build plate slightly, it’s a sign that the issue of first layer curling may be troubling the print.

While curling can also happen on the higher layers, it’s a separate issue that we will discuss in another article in the future due to it having entirely different causes than the issue of first layer curling.

Wrapping Up

It’s undeniable that experiencing the curling of the first layer on your 3D printed models is an annoying one due to it requiring a good amount of experimentation to fix in most scenarios.

To quickly recap, the issue of first layer curling is a result of extremely hot filament being exposed to the much colder (in comparison) build plate and the air.

When the plastic’s temperature drops very suddenly and unevenly due to this heat transfer, the plastic starts contracting very suddenly, which presents itself in the form of curling from the sides.

As a result, the primary goal for solving this issue is to ensure that the filament cools down slowly, gradually, and evenly by optimizing the printing process through different methods, such as z-offset tuning, bed leveling, temperature tuning, and many more.

Happy printing!