Optimal Cooling Fan Speed Configuration for PLA – Explained

Even though it’s usually overlooked compared to other print settings such as printing temperature and bed temperature, especially when printing with PLA filament, the cooling fan speed value plays a critical role in determining the properties of your 3D printed part, whether it’s the visual quality or the strength.

In this guide, we will discuss the optimal cooling fan speed value for printing with PLA filament, take you through the process of fine-tuning the cooling fan speed value with a fan tower, and look at the signs that can appear on your prints as a result of using too much or too little cooling when printing with PLA.

What Is the Optimal Cooling Fan Speed Value for Printing PLA?

While the general recommendation is to use a fan speed value of 100% when printing with PLA filament due to it not being a material that suffers from poor layer adhesion as a result of being cooled down way too quickly, unlike other commonly used filaments such as PETG and ABS, where too much cooling can easily create interlayer adhesion issues, there actually is more that goes into optimally configuring the fan speed value for PLA than that.

In essence, when you use a cooling fan speed value that’s on the higher end, you will immediately notice that the visual quality of your prints becomes much higher, as cooling the PLA down as quickly as possible will minimize the time it spends in its molten state, which in turn will prevent it from drooping and cause it to solidify before any deformation can occur.

So, in cases where you’re printing parts that are purely cosmetic, which effectively is the primary usage area for PLA due to its lack of flexibility that makes it highly susceptible to breakage when you use it for a functional part that you plan on exposing to physical forces, the general advice to go with the highest fan speed value possible does make sense to an extent.

On the other hand, while PLA will never be the perfect choice for functional parts, using a lower cooling fan speed, just as it does for any other material that actually requires it for a successful print, will allow the layers to have more time to form strong bonds with each other before solidifying in the case of PLA as well, which in turn will increase the strength of the part and make it less prone to cracking and breakage, and as a result, make the print more suited for functional usage.

With that in mind, in cases where you need to print a functional part and don’t have access to any other filament except PLA, using lower cooling fan speeds, or even not using any cooling at all, would be perfectly feasible and also the correct thing to do, as opposed to using a cooling fan speed value of 100% whenever you’re printing with PLA, regardless of the purpose of your print.

To round things up, we can practically say that there isn’t only one optimal cooling fan speed value for printing PLA and that the cooling fan speed you should use largely depends on the purpose of your print, whether it’s a high fan speed, such as 100% for cosmetic prints, such as a figurine, a low fan speed, such as 10%, for purely functional parts, such as nuts & bolts, or a balanced value, such as 50%, for a print that requires equal parts of strength and visual quality.

Fine-Tuning Your PLA Cooling Fan Speed Value

The best way to fine-tune the cooling fan speed value for PLA, or basically any other filament, is to print a fan speed tower, which effectively allows you to test different fan speed values in a single print and decide on the one that has produced the best results in a straightforward way.

Even though there are a few different methods you can utilize to print a fan tower, we will be using the Cura Calibration Shapes plugin for this guide in particular, which we have found to be the most convenient way of printing any calibration model, whether it’s a fan tower or a retraction tower.

So, to start, the first step you will need to take is to click the Marketplace button on the top-right corner of the Cura window, which will bring up Cura’s plugin manager, where you can install any plugin of your choice in an easy way.

cura opening marketplace


Next, type “calibration shapes” into the search input at the top of the Marketplace window, together with the quotation marks, click the Install button next to the Calibration Shapes entry, follow the on-screen instructions to install the plugin, and restart Cura for the plugin to load.

cura calibration shapes plugin installation


With the plugin now installed, click the Extensions button on the top menubar, hover over the Part for calibration option, and click Add a PLA TempTower, which should insert a temperature tower 3D model on the build plate.

pla temperature tower calibration shapes


Once that’s done, slice the 3D model (Slice button on the bottom-right corner), and switch to the Preview tab by clicking the corresponding button on the top of the Cura window.

pla temperature tower preview example


Now, bring the layer slider on the right side of the Cura window all the way down to 1, then bring it one layer up at a time (you can use arrow keys after clicking on the layer slider dot) until you find the point where the base of the model ends (where the two squares appear, which is the layer 5 in our example, as in the image below), and make a note of the layer number that comes right before, which would be 4 in our example, as the Change Layer Offset.

cura finding change layer offset for fan tower script


Next, bring the layer slider all the way up to find the total layer count, subtract the Change Layer Offset value you have noted earlier from the number from the total layer count, divide this number by 9 (the number of sections on the fan tower), and note down the number you find as the Change Layer value, which would be 41.5 ( (378-4) / 9 ), rounded up to 42, in our example.

cura total layer count preview example


Once you have both the Layer Offset and Change Layer values ready, click the Extensions button on the top menubar yet again, but this time, hover over the Post Processing option and click the Modify G-Code option to bring up the Post Processing Scripts window.

cura opening the post processing section


Now, click the Add a script button and choose the TempFanTower option from the dropdown menu that appears, which will activate the fan tower script we will be using to adjust the fan speed dynamically throughout the different sections of the tower.

cura tempfantower script in post processing


Once that’s done, configure the Starting Temperature value to be the same as the printing temperature you regularly use, input 0 for the Temperature Increment value, and enter the values you have noted down earlier into their respective inputs for the Change Layer and Change Layer Offset parameters.

fan tower adjustment example


Next, check the Activate Fan Tower checkbox and enter nine fan value percentages with semicolons in between into the Fan values in % box, representing the fan speed percentages your 3D printer will utilize when printing each of the nine sections on the fan tower.

For instance, if you enter “100;95;90;85;80;75;70;65;60” as your fan values, your 3D printer will print the fan tower’s first section with 100% fan speed and reduce the fan speed by 5% for each of the following sections all the way until it reaches 60% for the very last section.

fan tower adjustment 2nd example


Finally, close the Post Processing window, slice your 3D model, and print it as usual, which will prompt your 3D printer to produce a fan tower that you can observe to find the fan speed value that seems to work the best in your case, and adjust your slicer settings accordingly.

What Happens If You Use Too Much Cooling for Printing PLA?

While using too much cooling when printing PLA won’t have any noticeable adverse effects, it can cause the part you have printed not to be able to fulfill its purpose in cases where you’re looking to get some functional use out of it.

The primary issue you will come across as a result of using too much cooling for printing PLA is the part ending up being way too weak in cases where you’re printing a functional part, and considering that PLA isn’t the best choice for cases where you need your part to be able to sustain a load anyway, overcooling it will make things even worse in that department.

On the other hand, for prints where strength isn’t important at all, there is practically nothing such as too much cooling since using as much cooling as possible will only improve the visual quality of your print without any downsides.

What Happens If You Use Too Little Cooling for Printing PLA?

Compared to using too much cooling, where the primary problem you’ll face is the part you have printed not being strong enough, using too little cooling will produce signs that you can notice a lot easier due to its effect on the visual quality of the print.

The main issue you will come across using too little cooling or no cooling at all when printing with PLA is a considerable loss in visual quality, with the surfaces of your prints looking melty and smudged, as the molten material will have way too much time to droop and sag before naturally cooling down to the level where it solidifies and retains its shape.

On the other hand, for functional prints where visual quality isn’t exactly important, undercooling your PLA shouldn’t create any issues that you will need to worry about, as allowing the material to cool down naturally instead of cooling it down with a fan will further strengthen your part by giving the layers more time to adhere to each other strongly.

Conclusion

Even though going ahead with a 100% fan speed when printing PLA is a safe bet that will ensure you don’t have any issues regarding the visual quality of your prints, optimizing your fan speed value will allow you to strengthen your part in a way that wouldn’t be possible with the cooling fan working at full speed, which can come in handy in many scenarios.

Especially considering that PLA isn’t the most robust material around, which makes it far from being the first choice for a functional print, tweaking the fan speed to gain an extra bit of strength on your 3D printed part can be the key that allows it to fulfill its purpose reliably if you don’t have access to any other filament at the moment.