Cooling is one of the most dynamic settings in 3D printing, where the optimal value varies heavily between different filament types, different model shapes, and even different layers during the printing of the same object.
As a result, cooling is one of the most challenging settings to get right, and on top of that, the fact that it’s a fundamental parameter that needs to be correct at all times for the printing process to produce the desired results leaves no room for error.
In today’s article, we will be focusing our efforts on finding the optimal cooling fan speed for printing with TPU filament, which is a vital parameter that can make or break a print with its capability of heavily impacting the printing process.
So, how much cooling does TPU require for a successful 3D print?
Aside from bridges, overhangs, and smaller layers that require a slight-to-medium level of cooling to stabilize, printing with TPU filament, for the most part, does not require any cooling due to the fact that the layers need some time to form bonds that are strong enough with each other.
In the upcoming sections, we will analyze the cooling requirements of TPU in more detail, discuss the effects of various levels of cooling, and take a quick look at the signs that appear as a result of cooling TPU way too much or too little.
How Much Cooling (Fan Speed) Does TPU Require?
In the process of adjusting the cooling fan speed for printing with TPU filament, the best course of action is to take a case-by-case approach for optimal results.
In most cases, it’s possible to print with TPU filament without using any cooling, and considering that too much cooling can have adverse effects on the layer adhesion of your prints, it’s best to apply a slight degree of cooling (10-20% fan speed) at most to refrain from problems.
On the other hand, there are some exceptions that we need to keep in mind while configuring the cooling in the form of small layers, overhangs, and bridges, as they behave differently than the standard layers of a model.
For the printing of small layers, cooling will come in handy to ensure that the layers cool down sufficiently before the printer adds the upcoming layers on top, which will prevent these layers from deforming.
For overhangs and bridges, we will need cooling to solidify the plastic as quickly as possible before it starts drooping due to the lack of support beneath it.
In either case, starting with a cooling fan speed of 10-20% and moving up in increments of 5% until you find a balanced value that provides enough cooling without damaging the layer adhesion too much should do the job.
Since the values that yield the best results depend on many factors ranging from the shape of the model to the capabilities of your 3D printer, going through a few test prints is always the best course of action for a successful final product.
What Effects Does Cooling Have on Printing with TPU?
While cooling may seem like a factor that isn’t too significant, its direct impact on the temperature of TPU makes it a parameter that is just as crucial as parameters such as nozzle temperature and bed temperature on vital factors like layer adhesion and aesthetic quality.
The primary factor you will observe with different cooling levels while printing with TPU filament will be the change in the strength of adhesion between the layers, as the higher the speed of the cooling fans gets, the quicker the plastic will shift from its melted state to the solid-state.
Since the layers need to spend time contacting each other in their melted state to form bonds, which is particularly long in the case of TPU, solidifying the plastic too quickly will prevent these bonds from forming and cause the layer adhesion to be poor.
While TPU is much less prone to deformation at its melted state compared to other filaments, we still can’t ignore the effects of cooling on the aesthetic quality of the model, where lower cooling fan speeds make it more likely for the plastic to deform.
Fortunately, such deformations will most likely only be visible in the case of smaller layers that don’t have enough time to correctly cool down before the printer adds the upcoming layers on top and in the case of overhangs and bridges that don’t have enough support to stay stable until they can cool down naturally.
What Happens If You Apply Too Much Cooling on TPU?
There is no doubt that cooling the plastic down way too quickly before it can make proper contact with the build plate is harmful to the printing process, as thermoplastics, such as TPU, are highly sensitive to changes in temperature.
Below, we have listed the adverse effects of applying too much cooling on TPU:
- The plastic may become brittle as a result of excessive cooling.
- The model’s layers may separate (delamination) due to having insufficient time to form strong bonds, creating visible cracks on the surface.
- The layers of the model may warp due to the air pressure.
- The model may become very fragile and prone to cracking.
- Bridges may become specifically weak and easily break off.
- Overhangs may become specifically weak and easily break off.
What Happens If You Apply Too Little Cooling on TPU?
While applying too much cooling to TPU will prevent you from obtaining optimal results, too little cooling is no good either and comes with a different list of problems.
Below, we have listed the adverse effects of applying too little cooling on TPU:
- Stringing and blobbing may appear due to the nozzle picking up melted filament from the previous layers.
- Smaller layers may deform due to not having enough time to cool down.
- Bridges may start drooping due to not cooling down quickly enough.
- Overhangs may start drooping due to not cooling down quickly enough.
Due to its effects on the inner temperature of the plastic, correctly configuring the cooling fan speed parameter is a significant factor in avoiding issues related to bed adhesion, layer adhesion, model durability, and more.
To quickly recap, cooling is not entirely necessary for printing with TPU filament and; in fact, excessive cooling can cause more harm than good by causing the layers to cool down before they can correctly adhere to each other, which compromises the structural integrity of the object.
On the other hand, as exceptions such as overhangs, bridges, and small layers that don’t take too much to print will not stabilize from their melted state without some help, activating cooling specifically for these scenarios will be necessary nevertheless.