What Causes PLA to Curl During 3D Printing? (How to Fix?)

The appearance of imperfections on the model’s structure during the printing process makes up for the majority of the issues in the 3D printing world, where the model you have printed looks nothing like the model you see on your screen.

While the most common examples of such an issue are stringing and blobbing, which most 3D printing enthusiasts are familiar with, there are many other ways for your model to have imperfections for different reasons, meaning that they also require distinct solutions.

Today, we will be talking about such an issue that can frequently occur while printing with PLA filament, known as curling, where the edges of the plastic end up curling upwards and ruin the model by causing dimensional inaccuracies.

So, what causes PLA to curl during the 3D printing process?

The primary reasons that cause PLA to curl during the 3D printing process are the uneven or insufficient cooling of the plastic after it leaves the nozzle of the 3D printer instead of gradual cooling evenly spread across the entire print.

Next up, we will discuss the factors that can cause PLA to curl in more detail, find out what we can do to prevent the curling from taking place, and take a quick look at what we can do for the particular cases of PLA curling on the first layer and overhangs.

What Causes PLA to Curl During 3D Printing?

If you have never experienced such a thing before, observing the edges of your 3D printed model curling upwards can be a confusing phenomenon to witness.

When PLA cools down in an uneven or insufficient manner, the issue of curling takes place due to how thermoplastics behave in such conditions.

In the case of uneven cooling, the layers that cool down before the others end up contracting and pulling the melted layers towards themselves, causing these layers to solidify in a curled state as a result.

On the other hand, in the case of insufficient cooling, the plastic ends up staying in a melted state for too long, which eventually causes it to deform and solidify in this deformed state, presenting itself in the form of curling.

As either scenario will end up with your model having curling issues, it’s vital to ensure no problems in either front to guarantee that your prints don’t curl.

How Do You Keep PLA from Curling?

Preventing PLA from curling mainly comes down to ensuring that you configure your printer and slicer settings correctly, which won’t take too much of your effort or time in most cases, as the process of configuring these parameters is pretty straightforward.

Below is a list of steps we recommend taking to minimize the chance of experiencing PLA curling during the printing process:

  • Optimize the cooling. The vital points to consider with cooling are that it’s even throughout the model, and it’s strong enough to cool the plastic down rapidly before it can deform. Using a larger (and stronger) cooling fan and increasing the cooling speed (except for the first few layers to avoid first layer curling issues) are the best things you can do to combat PLA curling.
  • Decrease the nozzle temperature. Decreasing the nozzle temperature will allow the plastic to cool down quicker, reducing the chance it deforms due to staying in a melted state for too long.
  • Reduce the print speed. Reducing the print speed will give the plastic more time to cool down naturally before the new layers come in, once again reducing the chance of deformation.
  • Use a printing enclosure. While not a necessity, printing with an enclosure allows the stabilization of the ambient temperature and protection of the model from drafts, which drastically reduces the chance of the plastic cooling down unevenly due to external factors.

PLA Curling on the First Layer – What to Do?

In some cases, it’s possible for PLA to only curl on the first layer or first few layers but print as it should throughout the rest of the model, and in such a case, the optimal solution path to follow is slightly different.

PLA curling on the first layer is primarily a product of bed adhesion issues caused by a wrong amount of spacing between the surface and the nozzle, which prevents the nozzle from applying enough pressure to stick the plastic to the build plate reliably.

To fix the issue of PLA curling on the first layer, we recommend following the steps below:

  • Ensure that you level the bed correctly.
  • Re-configure the Z offset.
  • Re-configure the initial layer height and initial layer speed values.
  • Clean the build surface thoroughly.
  • Use a heated bed if possible.
  • Apply adhesives to the build plate.
  • Use a brim or a raft.

PLA Curling on Overhangs – What to Do?

Another specific case of PLA curling is when it only curls on overhangs and prints correctly throughout the rest of the model, which once again requires a slightly different solution compared to the cases where the plastic curls throughout the entire model.

In the case of overhangs curling with PLA filament, the primary culprit is either too little part cooling or too high nozzle temperature, with both factors leading to the plastic running way too hot and not cooling down on time.

To fix the problem, we recommend applying a higher level of cooling (try 10% increments) or reducing the nozzle temperature (try 5-degree increments) while printing overhangs, which should allow the layers to cool in a timely fashion.

Wrapping Up

While the curling of PLA can be an annoying problem to deal with, it’s usually a simple one to solve by following the appropriate steps as the possible culprits behind the issue is limited.

To quickly recap, what causes PLA to curl after it leaves the 3D printer’s nozzle is either uneven cooling of the plastic or a lack of cooling, where the layers that cool down before the others end up pulling the hot layers as they contract or the plastic remains in its melted state for too long and ends up deforming.

Since printing with a too high temperature and not using enough cooling are the primary culprits behind this issue, going through these two variables and correcting them should solve your problem in most cases.

Happy printing!